Eco-Friendly Recycling of Lithium Batteries for Extraction of High-Purity Metals

The significant increase in lithium batteries consumption produces a significant quantity of discarded lithium-ion batteries (LIBs). On the one hand, the shortage of high-grade ores leads to the necessity of processing low-grade ores, which contain a low percentage of valuable metals in comparison to the discarded LIBs that contain a high percentage of these metals, which enhances the processing of the discarded LIBs. On the other hand, the processing of discarded LIBs reduces the negative environmental effects that result from their storage and the harmful elements contained in their composition. Hence, the current study aims at developing cost-effective and ecofriendly technology for cobalt and lithium metal ion recovery based on discarded LIBs. A novel synthesized solid-phase adsorbent (TZAB) was utilized for the selective removal of cobalt from synthetic solutions and spent LIBs. The synthesized TZAB adsorbent was characterized by using 13C-NMR, GC-MS, FT-IR, 1H-NMR, and TGA. The factors affecting the adsorption of cobalt and lithium ions from synthetic solutions and spent LIBs, including the sorbent dose, pH, contact time, temperature, and cobalt concentration were investigated. The conditions surrounding the recovery of cobalt and lithium from processing discarded LIBs, were investigated to optimize the maximum recovery. The Langmuir, Freundlich, and Dubinin–Radushkevich (D-R) isotherm models were used to study the kinetics of the adsorption process. The obtained results showed that high-purity CoC2O4 and Li3PO4 were obtained with a purity of 95% and 98.3% and a percent recovery of 93.48% and 95.76%, respectively. The maximum recovery of Co(II) from synthetic solutions was obtained at C0 = 500 mg·L−1, dose of 0.08 g, pH 7.5, T = 25 °C, and reaction time = 90 min. The collected data from Langmuir’s isotherm and the adsorption processes of Co agree with the data predicted by the D-R isotherm models, which shows that the adsorption of Co(II) onto the TZAB seems to be chemisorption, and the results agree with the Langmuir and D-R isotherm models.


Introduction
Electronic products, particularly mobile ones such as cell phones and laptops, have shorter lifespans than they used to because of the fast rate at which new technologies are developed. Because of this, there has been a growth in the quantity of used electronic and electrical equipment, such as LIBs [1,2]. Since these batteries contain harmful materials such as heavy metals and electrolytes, their disposal can have negative consequences for the environment. These important metal ions include cobalt and lithium, which are crucial and appreciated metals, and the recycling of them is essential [3].
Recycling LIBs not only helps prevent pollution, but it also results in the better use of scarce materials and may reduce the cost of producing new batteries. In addition, Nearly 90% of the value of used LIBs comes from the metals contained within them. The active cathode layer contains these metals. When it comes to the business of managing and recycling LIBs, cobalt is by far the most valuable component and the most lucrative commodity traded. It is anticipated that 4500 tons of cobalt are present in 1,200,000,000 cell phone batteries with an average weight of 20 g/unit [33,34]. There is an estimated 8900 USD per ton market for the recycling of lithium cobalt oxide batteries, while recycling lithium manganese oxide batteries is seen as unprofitable and inconvenient, with a capacity of just 860 USD per ton. Cobalt's 2017 economic value per ton of waste LIBs was projected to be 55,000 USD. The European Commission has classified cobalt as a critical, precious, and strategic metal due to its fixed production in 2017, posing a threat to the market and supply chain (EU, 2017). More than fifty percent of the world's cobalt funds will be depleted by the LIBs industry by 2025 [35,36].
The current study aims at exploring the preparation and characterization of a novel synthesized adsorbent for the sorption of high-purity cobalt and lithium based on spent LIBs through adsorption by using a modified triazole Schiff base. The factors affecting the sorption of cobalt ions, including pH, sorbent dose, contact time, temperature, and cobalt concentrations, were investigated. Additionally, the kinetics of the adsorption processes were studied.

Materials
All the chemicals used in the current study were of analytical grade and obtained from Sigma-Aldrich (St. Louis, MO, USA) and Merck (Darmstadt, Germany). The synthetic reactions involving metal complexes and the ligand were performed by using solvents that were distilled and dried, as is customary for such techniques in the literature. The decomposition temperatures of the metal complexes and the melting points of the produced ligands were determined with a Stuart melting point instrument.
Using a Nicolet FT-IR Impact 400D spectrometer, infrared spectra of the solids (by using a KBr matrix) in the 3700-370 cm −1 area were recorded. The Bruker Advance 300 MHz equipment was used to obtain the 1H and 13CNMR spectra. The ligand mass spectra were captured with a JEOL MS Route instrument. At room temperature, magnetic susceptibility was measured by weighing the complexes against a standard of mercury acetate ligand in a Stanton SM12/S Gouy balance.

Preparation of the Aqueous Solutions of Cobalt
Cobalt (II) nitrate hexahydrate (Co(NO 3 )2.6H 2 O) (J. T. Baker, 99%, Phillipsburg, NJ, USA) and deionized (DI) water were used to prepare all the aqueous solutions. Except for the experiments conducted to test the impact of pH upon sorption, all the cobalt solutions were adjusted at a pH of 5.5. Atomic absorption spectrophotometry (AAS) (Varian AA240) was used to analyze the cobalt content, with the calibration curve established with a cobalt standard (Merck) of 1000 mg/L.

Adsorption via Batch Technique
The batch adsorption mode tests were accomplished by reserving the solution in conjunction with a proper dose of PST-SA in an Erlenmeyer flask (100 mL) in a shaker incubator of the type FTSH-301 MINI (SP) at 150 rpm. Each experiment was conducted to determine the Co +2 adsorption by utilizing 0.1 g/L PST-SA at pH values between 2 and 10, with an initial Co +2 concentration of 250 mg/L. The mixture was shaken for 30 min at 25 • C before starting the experimental studies on the adsorption process.
NaOH and HCl solutions were utilized for pH regulation. To determine the optimum adsorbent dose, a set of examinations was conducted by utilizing a dosage between 0.01 and 0.25 g/L at the optimum pH value. No novel parameters of operation were introduced in this set of evaluations. The kinetic experiments were conducted at 25 • C at a 250 mg/L Materials 2023, 16, 4662 4 of 26 initial concentration and for times ranging from 5 to 120 min. The initial Co +2 concentrations in the equilibrium experiments varied from 250 to 1500 mg/L. The time of equilibrium was calculated via adsorption kinetics.
The sorbents' abilities to absorb Co +2 ions in the presence of another interfering ion were measured with several binary adsorption tests. For the multicomponent adsorption experiments, the ending Co +2 concentrations were determined by using UV-VIS spectroscopy (Rigol-Ultra-3660 spectrophotometer) and atomic absorption spectroscopy (by using a Varian AA240). A duplicate observation of each experiment was performed, and the mean values were reported. The adsorption capacity qt (mg/g) was calculated according to Equations (1) and (2).
where q t is the concentration of the adsorbed cobalt ions per unit mass at time t (mg/g); qe is the equilibrium concentration (mg/g); C o is the initial concentration of cobalt ions in the solution (mg/mL); C e and C t is the cobalt ion concentration at time t or at equilibrium (mg/mL), respectively; V is the aqueous solution volume containing cobalt ions (L); and m is the adsorbent mass (g).

Preparation of the Adsorbent
In order to prepare the adsorbent, 2.0 g of 3,5-diamino-1,2,4-triazole corresponding to (10.0 mmol), in addition to 9.90 g 4-hydroxy 2-butanone corresponding to (20.0 mmol), were mixed by using a three-neck round bottom flask (250 mL has 3 arms) sited on a hot plate with a stirrer associated with a condenser and temperature controller. A total of 25 mL of di-methylformamide (DMF) was utilized as the solvent of the reaction. The reaction mix was refluxed for 36 h at 90 • C, as presented in Scheme 1. After the completion of the reaction, the remaining solvent was evaporated by using an evaporator. To eliminate all traces of the solvent, the resultant pale-yellow product was dried at 50 • C for 6 h by using a vacuum oven before being measured. It was noted that the final yield was 10.7 g, which represents about 92.68%. This chemical is microcrystalline solid in nature, has a 280 • C melting point, and is pale yellow in color. At room temperature, this ligand was soluble in DMF and DMSO.
NaOH and HCl solutions were utilized for pH regulation. To determine the optimum adsorbent dose, a set of examinations was conducted by utilizing a dosage between 0.01 and 0.25 g/L at the optimum pH value. No novel parameters of operation were introduced in this set of evaluations. The kinetic experiments were conducted at 25 °C at a 250 mg/L initial concentration and for times ranging from 5 to 120 min. The initial Co +2 concentrations in the equilibrium experiments varied from 250 to 1500 mg/L. The time of equilibrium was calculated via adsorption kinetics.
The sorbents' abilities to absorb Co +2 ions in the presence of another interfering ion were measured with several binary adsorption tests. For the multicomponent adsorption experiments, the ending Co +2 concentrations were determined by using UV-VIS spectroscopy (Rigol-Ultra-3660 spectrophotometer) and atomic absorption spectroscopy (by using a Varian AA240). A duplicate observation of each experiment was performed, and the mean values were reported. The adsorption capacity qt (mg/g) was calculated according to Equations (1) and (2).
where qt is the concentration of the adsorbed cobalt ions per unit mass at time t (mg/g); qe is the equilibrium concentration (mg/g); Co is the initial concentration of cobalt ions in the solution (mg/mL); Ce and Ct is the cobalt ion concentration at time t or at equilibrium (mg/mL), respectively; V is the aqueous solution volume containing cobalt ions (L); and m is the adsorbent mass (g).

Preparation of the Adsorbent
In order to prepare the adsorbent, 2.0 g of 3,5-diamino-1,2,4-triazole corresponding to (10.0 mmol), in addition to 9.90 g 4-hydroxy 2-butanone corresponding to (20.0 mmol), were mixed by using a three-neck round bottom flask (250 mL has 3 arms) sited on a hot plate with a stirrer associated with a condenser and temperature controller. A total of 25 mL of di-methylformamide (DMF) was utilized as the solvent of the reaction. The reaction mix was refluxed for 36 h at 90 °C, as presented in Scheme 1. After the completion of the reaction, the remaining solvent was evaporated by using an evaporator. To eliminate all traces of the solvent, the resultant pale-yellow product was dried at 50 °C for 6 h by using a vacuum oven before being measured. It was noted that the final yield was 10.7 g, which represents about 92.68%. This chemical is microcrystalline solid in nature, has a 280 °C melting point, and is pale yellow in color. At room temperature, this ligand was soluble in DMF and DMSO. Scheme 1. A novel triazole Schiff base was created by condensing 3,5-diamino-1,2,4-triazole and 4-hydroxybutan-2-one in a 1:2 mass ratio by using alkali-fusion method.

Adsorbent Characterization
Inductively coupled plasma optical emission spectroscopy (ICP-OES) (Optima 7000DV, PerkinElmer, MA, USA) was utilized to detect the concentrations of metal ions in a given solution. Thermo Fischer Scientific's Nicolet™ iS10 spectrophotometer (Nicolet iS10, Morris Plains, NJ, USA) was used to carry out the FTIR spectra. 1H (CD4O, 500 MHz) and (CD4O, 202 MHz) nuclear magnetic resonance (NMR) spectra of IL and IL-ICR (IL after extraction) were documented on a Bruker 500 MHz NMR spectrometer (AVANCE III HD 500 MHz, Bruker BioSpin GmbH, Ettlingen, Germany). The structure and morphology of the prepared adsorbent were characterized by using an energy-dispersive X-ray spectrometer attached to a field emission scanning electron microscope (SEM, Hitachi S-4800, Tokyo, Japan) (EDS, Genesis XM2, EDAX, Pleasanton, CA, USA).

Characterization of TZAB
Firstly, the molecular structure of the produced adsorbent was characterized by using FT-IR spectroscopy. A comparison of the infrared spectra of 3,5-diamino-1,2,4-triazole (DAT) and the triazole Schiff base (TZAB) is presented in Figure 1. The symmetric and asymmetric N-H stretching of the primary amine groups linked to C3 and C5 of the triazole ring was responsible for the two absorption bands observed at 3400 and 3100 cm −1 in the triazole spectra, respectively [37]. The N-H stretching peak at 3300 cm −1 could be traced back to the secondary -NH group present in the triazole ring. N-H bending (-NH 2 ) and C=N stretching (ring) were responsible for the intense absorption peaks at 1635 and 1554 cm −1 , respectively. The C-N stretching (triazole ring) exhibited a modest absorption band at 1340 cm −1 and a strong peak at 1053 cm −1 , while the C-N stretching (-NH 2 ) vibrations did not show any absorption. The other peaks of the reactant 3,5-diamino-1,2,4-triazole were clearly assigned [38].

Characterization of TZAB
Firstly, the molecular structure of the produced adsorbent was characterized by using FT-IR spectroscopy. A comparison of the infrared spectra o 3,5-diamino-1,2,4-triazole (DAT) and the triazole Schiff base (TZAB) is presented in Figure 1. The symmetric and asymmetric N-H stretching of the primary amine groups linked to C3 and C5 of the triazole ring was responsible for the two absorption bands observed at 3400 and 3100 cm −1 in the triazole spectra, respectively [37]. The N-H stretching peak at 3300 cm −1 could be traced back to the secondary -NH group present in the triazole ring. N-H bending (-NH2) and C=N stretching (ring) were responsible for the intense absorption peaks at 1635 and 1554 cm −1 , respectively. The C-N stretching (triazole ring) exhibited a modest absorption band at 1340 cm −1 and a strong peak at 1053 cm −1 while the C-N stretching (-NH2) vibrations did not show any absorption. The other peaks of the reactant 3,5-diamino-1,2,4-triazole were clearly assigned [38].
Because of the -OH stretching of the new hindered phenolic group, a wide absorption band developed at 3430 cm −1 . An absorption at 1428 cm −1 was seen for C-H bending, whereas the classic asymmetric C-H stretching peaks emerged at 2968 cm −1 . In the novel synthesized material TZAB, the -N-H stretching (primary amine group absorption bands at 3400 and 3100 cm −1 disappeared, while the -C=N stretching (imine exocyclic double bond peak formed at 1661 cm −1 [39]. It was confirmed that the intermediate TZAB had the correct structure by observing the absorption band at 1093 cm −1 due to the C-N stretching vibration as well as other characteristic peaks, as presented in Scheme 1. The thermogravimetric analysis of the prepared adsorbent is presented in Figure 2 which shows that the imine coupling of 3,5-diamino-1,2,4-triazole (DAT) with 4-hydroxybutan-2-one was effective. The thermal analysis curve demonstrated that the Because of the -OH stretching of the new hindered phenolic group, a wide absorption band developed at 3430 cm −1 . An absorption at 1428 cm −1 was seen for C-H bending, whereas the classic asymmetric C-H stretching peaks emerged at 2968 cm −1 . In the novel synthesized material TZAB, the -N-H stretching (primary amine group) absorption bands at 3400 and 3100 cm −1 disappeared, while the -C=N stretching (imine) exocyclic double bond peak formed at 1661 cm −1 [39]. It was confirmed that the intermediate TZAB had the correct structure by observing the absorption band at 1093 cm −1 due to the C-N stretching vibration as well as other characteristic peaks, as presented in Scheme 1.
The thermogravimetric analysis of the prepared adsorbent is presented in Figure 2, which shows that the imine coupling of 3,5-diamino-1,2,4-triazole (DAT) with 4-hydroxybutan-2-one was effective. The thermal analysis curve demonstrated that the adsorbent TZAB was less durable than the reactant DAT. The first temperature of degradation for DAT was observed at 275 • C, while the TZAB began to degrade at 188 • C. The DAT's second degradation temperature was observed at 560 • C, and it was completely degraded at 712 • C. The second and third decomposition temperatures of the TZAB were 325 • C and 562 • C, respectively. Hence, Schiff coupling of triazole with a 4-hydroxybutan-2-one molecule decreased the heat stability. adsorbent TZAB was less durable than the reactant DAT. The first temperature o degradation for DAT was observed at 275 °C, while the TZAB began to degrade at 188 °C The DAT's second degradation temperature was observed at 560 °C, and it wa completely degraded at 712 °C. The second and third decomposition temperatures of the TZAB were 325 °C and 562 °C, respectively. Hence, Schiff coupling of triazole with a 4-hydroxybutan-2-one molecule decreased the heat stability. The major (δ ppm) assignments were performed at six ppm, which corresponds to the more deshielded -NH group protons. It was noted that the assignment of the -OH protons (δ = 4.73 ppm) was also deshielded, although less than the assignment of the -NH protons (δ = 6 ppm). The twin assignments of the methylene-group protons were detected at chemical shifts of 3.07 and 3.66 ppm, but the methyl group protons appeared to be significantly shielded compared to the methylene protons at 2.69 ppm. The characterization of the TZAB derv. ligand that occurred by using 1H-NMR spectroscopy is presented in Figure 3A,B. Hz, -OH group), 6 (s, 1H, -NH group). 1H-NMR spectroscopy with an energy of 400.15 MHZ and DMSO-d6 as a diluent is an efficient and suitable instrument that provides substantial information about protons in the synthesized TZAB derv. ligand and can be used to assist with structural characterization.
The major (δ ppm) assignments were performed at six ppm, which corresponds to the more deshielded -NH group protons. It was noted that the assignment of the -OH protons (δ = 4.73 ppm) was also deshielded, although less than the assignment of the -NH protons (δ = 6 ppm). The twin assignments of the methylene-group protons were detected at chemical shifts of 3.07 and 3.66 ppm, but the methyl group protons appeared to be significantly shielded compared to the methylene protons at 2.69 ppm. The characterization of the TZAB derv. ligand that occurred by using 1H-NMR spectroscopy is presented in Figure 3A,B. The chief δ (ppm) performed about 20.6-23.6 ppm, which is associated with the more shielded methyl carbon. It was noticed that the methylene carbon attached to the hydroxyl group was further deshielded (59.1 ppm) than the next methylene carbon (40.9-42.4 ppm). The distinct assignment of the imine group carbon indicated that it was additionally deshielded and associated with a chemical shift of 165.1 ppm. The imine carbon of the triazole ring was established and gave a deshielded value of 157.9 ppm. The specification of the TZAB ligand by using 13C-NMR is shown in  different parameters, namely, the chemical formula, more stable fragment [m/z]+, and purity. Figure 5 shows a GC/MS analysis of the triazole derv. Specific patterns of significant fragmentation were observed and were related to the synthetically produced TZAB derv. chelating ligand; for example, C4H8O2 with a molecular weight (M.W) of 88 and a relative abundance of 34, which would be associated with 4-hydroxybutan-2-one, and C2H5N5 with a M.W of 99 and a relative frequency of 21, which is connected to 1,2,4-triazole-3,5-diamine moiety.   different parameters, namely, the chemical formula, more stable fragment [m/z]+, and purity. Figure 5 shows a GC/MS analysis of the triazole derv. Specific patterns of significant fragmentation were observed and were related to the synthetically produced TZAB derv. chelating ligand; for example, C4H8O2 with a molecular weight (M.W) of 88 and a relative abundance of 34, which would be associated with 4-hydroxybutan-2-one, and C2H5N5 with a M.W of 99 and a relative frequency of 21, which is connected to 1,2,4-triazole-3,5-diamine moiety.

Effect of pH
The pH variation is a significant factor in the adsorption process because of the hydrogen (H + ) and hydroxyl (OH − ) ions. This component can ensure the separation of the presented metal ions such as Co 2+ and alter the surface chemistry of the chosen sorbent. Figure 6A illustrates the effect of the pH change on the Co 2+ adsorption efficiency. The pH effect was investigated by varying it in the range from 2 to 10 for a Co 2+ concentration of 250 mg/L. The adsorbent's surface charge and cobalt (II) species fluctuated when the solution pH changed. Figure 6B illustrates the principal species of cobalt (II) at pH 4-13, which would include Co 2+ , Co(OH) + , Co(OH)2, and Co(OH) 3− . The dominating species was Co 2+ , and cobalt (II) was mostly eliminated via the adsorption reaction. The influence of pH on Co 2+ sorption was calculated at pH values ranging from 2 and 9.
It was noted that when a pH of 7.5 was reached, the TZAB material showed an outstanding adsorption capacity towards Co 2+ due to the protonation of the group reducing and the non-protonated groups being able to bind more Co 2+ . Low cobalt-ion adsorption was observed on the adsorbents in acidic and neutral environments. Because of the shift in potential at the adsorbent's surface, the adsorption capacity rose dramatically, and the surface of the protonation turned cationic. In solutions with a pH better than pHzpc, the surface is negatively charged, making it attractive to cationic ions. The adsorbent's surface can gradually transform from positive to negative as the pH value increases from 3.0 to 10.0. Cobalt ion sorption is improved by an adsorbent with a more negative potential. A pH of 7.5 was selected for the highest adsorption of cobalt by using the TZAB.  Figure 6B illustrates the principal species of cobalt (II) at pH 4-13, which would include Co 2+ , Co(OH) + , Co(OH) 2 , and Co(OH) 3− . The dominating species was Co 2+ , and cobalt (II) was mostly eliminated via the adsorption reaction. The influence of pH on Co 2+ sorption was calculated at pH values ranging from 2 and 9.
It was noted that when a pH of 7.5 was reached, the TZAB material showed an outstanding adsorption capacity towards Co 2+ due to the protonation of the group reducing and the non-protonated groups being able to bind more Co 2+ . Low cobalt-ion adsorption was observed on the adsorbents in acidic and neutral environments. Because of the shift in potential at the adsorbent's surface, the adsorption capacity rose dramatically, and the surface of the protonation turned cationic. In solutions with a pH better than pH zpc , the surface is negatively charged, making it attractive to cationic ions. The adsorbent's surface can gradually transform from positive to negative as the pH value increases from 3.0 to 10.0. Cobalt ion sorption is improved by an adsorbent with a more negative potential. A pH of 7.5 was selected for the highest adsorption of cobalt by using the TZAB.

Effect of Sorbent Dose
The dosage of the sorbent has a significant effect on the practical application of the sorbent for the metal ion adsorption process [40,41]. The effect of the adsorbent dose on the Co +2 adsorption process was examined by employing variable amounts of the TZAB ranging from 0.01 to 1 g, which were added to 20 mL of the Co +2 solution with a 250 ppm concentration at an ambient temperature (25 • C), 7.5 pH, and contact time of 1 hr. The results obtained are presented in Figure 7. It was noted that the percent removal of Co +2 improved from 29.76 to 88.93% when the sorbent dose increased from 0.01 to 0.08 g. This can be attributed to the fact that the increase in the TZAB dose resulted in more active sites that were available for sorption at the same concentration of Co +2 , so at 0.08 g of the TZAB, all the active sites were occupied and any excess TZAB dose addition did not affect the adsorption capability of the TZAB, as presented in Figure 7. sorbent for the metal ion adsorption process [40,41]. The effect of the adsorbent dose on the Co +2 adsorption process was examined by employing variable amounts of the TZAB ranging from 0.01 to 1 g, which were added to 20 mL of the Co +2 solution with a 250 ppm concentration at an ambient temperature (25 °C), 7.5 pH, and contact time of 1 hr. The results obtained are presented in Figure 7. It was noted that the percent removal of Co +2 improved from 29.76 to 88.93% when the sorbent dose increased from 0.01 to 0.08 g. This can be attributed to the fact that the increase in the TZAB dose resulted in more active sites that were available for sorption at the same concentration of Co +2 , so at 0.08 g of the TZAB, all the active sites were occupied and any excess TZAB dose addition did not affect the adsorption capability of the TZAB, as presented in Figure 7.

Effect of Contact Time
The effect of the contact time on the Co +2 adsorption process was examined by changing the contact time in the range from 1 to 120 min at 0.08 g of a TZAB dose at 25 °C and 7.5 pH. The obtained results are presented in Figure 8. The adsorption process evolved over time via numerous steps of surface diffusion, penetration, and adsorption equilibrium. It was noted that the adsorption quantity increased rapidly over the first 30 min and reached 102.12 mg/g after 40 min. Subsequently, the sorption quantity gradually increased from 45 to 90 min and finally reached 122.87 mg/g at 90 min. After extending the contact time to 90 min, the TZAB adsorption capacity reached the equilibrium state, and nearly no further change was noted.

Effect of Contact Time
The effect of the contact time on the Co +2 adsorption process was examined by changing the contact time in the range from 1 to 120 min at 0.08 g of a TZAB dose at 25 • C and 7.5 pH. The obtained results are presented in Figure 8. The adsorption process evolved over time via numerous steps of surface diffusion, penetration, and adsorption equilibrium. It was noted that the adsorption quantity increased rapidly over the first 30 min and reached 102.12 mg/g after 40 min. Subsequently, the sorption quantity gradually increased from 45 to 90 min and finally reached 122.87 mg/g at 90 min. After extending the contact time to 90 min, the TZAB adsorption capacity reached the equilibrium state, and nearly no further change was noted.

Kinetics of Co +2 Adsorption
The pseudo first-order model and pseudo second-order model (Equations (3) and (4)) were utilized to examine the adsorption kinetics of the TZAB [42].

Kinetics of Co +2 Adsorption
The pseudo first-order model and pseudo second-order model (Equations (3) and (4)) were utilized to examine the adsorption kinetics of the TZAB [42].
where Ce (mg·L −1 ) represents the equilibrium concentration of Co +2 ; Q t and Q e (mg·g −1 ) represent the amount of cobalt adsorbed by the sorbents at time t and after reaching equilibrium, respectively; and k 1 (min −1 ) and k 2 (mg·g −1 ) represent the rate constants of the pseudo first-and second-order kinetics models. It was noted that the TZAB adsorption process clearly fit the pseudo second-order kinetic model (R 2 = 0.9983) more faithfully than that of the pseudo first-order kinetic equation (R 2 = 0.9613), as presented in Table 1 and Figure 9, which suggests that the TZAB adsorption of Co +2 may depend mainly on the chemisorption process [43,44]. In the meantime, it can be concluded that the TZAB had a large number of active sites for the absorption of Co +2 .

Kinetics of Co +2 Adsorption
The pseudo first-order model and pseudo second-order model (Equations (3) and (4)) were utilized to examine the adsorption kinetics of the TZAB [42].
where Ce (mg·L −1 ) represents the equilibrium concentration of Co +2 ; Qt and Qe (mg·g −1 ) represent the amount of cobalt adsorbed by the sorbents at time t and after reaching equilibrium, respectively; and k1 (min −1 ) and k2 (mg·g −1 ) represent the rate constants of the pseudo first-and second-order kinetics models. It was noted that the TZAB adsorption process clearly fit the pseudo second-order kinetic model (R 2 = 0.9983) more faithfully than that of the pseudo first-order kinetic equation (R 2 = 0.9613), as presented in Table 1 and Figure 9, which suggests that the TZAB adsorption of Co +2 may depend mainly on the chemisorption process [43,44]. In the meantime, it can be concluded that the TZAB had a large number of active sites for the absorption of Co +2 .

Influence of Ionic Strength
The influence of the ionic strength on the cobalt adsorption behaviour can be utilized to differentiate the sort or type of complex formation between the sorbent and adsorbate surface. If the ionic strength has no effect on the sorption process, the adsorbent and adsorbate will form an inner surface complex. If the ionic strength increases, the adsorbent and adsorbate will construct an outer surface complex. The adsorption experiment was conducted with various NaNO 3 concentrations (≈0, 0.001, 0.01, 0.1, and 1 mol/L). It was noted that the TZAB adsorption capacity to adsorb Co +2 was not sensitive to changes in the NaNO 3 concentration, as shown in Figure 10. The sorption procedure of the manufactured sample was independent of ionic strength, and complexation on the inner spherical surface (chemical adsorption) instead of the outer spherical surface (physical adsorption) had a larger effect on the sorption of Co +2 on the TZAB [45]. The kinetic effect of the adsorption was evidenced by the experimental results. In conclusion, the TZAB adsorption followed the pseudo second-order model, which is controlled by chemical adsorption. not sensitive to changes in the NaNO3 concentration, as shown in Figure 10. The sorption procedure of the manufactured sample was independent of ionic strength, and complexation on the inner spherical surface (chemical adsorption) instead of the outer spherical surface (physical adsorption) had a larger effect on the sorption of Co +2 on the TZAB [45]. The kinetic effect of the adsorption was evidenced by the experimental results. In conclusion, the TZAB adsorption followed the pseudo second-order model, which is controlled by chemical adsorption.

Adsorption Isotherms and Thermodynamic Study
As is well known, adsorbents are most characterized by their sorption capability and removal amount. The influence of different starting concentrations on the adsorption capability and removal amount of the synthesized sorbent was investigated in a sequence of experiments performed for this study. The adsorption capability increased and the TZAB removal rate decreased as the cobalt concentration increased, as shown in Figure  11. After 90 min of operation in the solution at pH = 7.5, the TZAB's adsorption ability increased from 24.5 mg·g −1 to 319.7 mg·g −1 . However, as the Co +2 concentration rose from

Adsorption Isotherms and Thermodynamic Study
As is well known, adsorbents are most characterized by their sorption capability and removal amount. The influence of different starting concentrations on the adsorption capability and removal amount of the synthesized sorbent was investigated in a sequence of experiments performed for this study. The adsorption capability increased and the TZAB removal rate decreased as the cobalt concentration increased, as shown in Figure 11. After 90 min of operation in the solution at pH = 7.5, the TZAB's adsorption ability increased from 24.5 mg·g −1 to 319.7 mg·g −1 . However, as the Co +2 concentration rose from 100 mg·L −1 to 1500 mg·L −1 , the eliminate rate dropped from 99.33% to 83.9% after being immersed in the solution for 90 min at a pH of 7.5. The reduction in the extraction efficiency can be attributed to the scientific fact that the adsorbent dose remained unchanged, which means that the binding sites of the TZAB are limited. It is theorized that the reduction in the removal rate was due to the steady supply of the adsorbent. So, the TZAB had limited binding sites. Therefore, the ligand bound to Co +2 with more adsorption sites, which led to a higher concentration in the remaining cobalt ions as the Co +2 concentration rose. 100 mg·L −1 to 1500 mg·L −1 , the eliminate rate dropped from 99.33% to 83.9% after being immersed in the solution for 90 min at a pH of 7.5. The reduction in the extraction efficiency can be attributed to the scientific fact that the adsorbent dose remained unchanged, which means that the binding sites of the TZAB are limited. It is theorized that the reduction in the removal rate was due to the steady supply of the adsorbent. So, the TZAB had limited binding sites. Therefore, the ligand bound to Co +2 with more adsorption sites, which led to a higher concentration in the remaining cobalt ions as the Co +2 concentration rose. Three different adsorption isotherm models (Equations (5)- (12)) were used to model the adsorption process. The Langmuir and Freundlich isotherms and the D-R isotherm are presented in Table 2 and Figure 12. The Langmuir isotherm model is expressed in Equation (5): Three different adsorption isotherm models (Equations (5)- (12)) were used to model the adsorption process. The Langmuir and Freundlich isotherms and the D-R isotherm are presented in Table 2 and Figure 12. The Langmuir isotherm model is expressed in Equation (5):    C e is the concentration of Co +2 in the solution (mg·dm −3 ) at equilibrium, and q e is the concentration of the solid-phase adsorbate (mg·g −1 ). Qo is the theoretical monolayer adsorption capacity (mg·g −1 ), and b is the adsorption energy (dm 3 ·mg −1 ). The linear form of the Langmuir equation is given by Equation (6) [46]: Using the linear plot of C e /q e vs. C e in Figure 12A, the values for Q o and K l , the Langmuir constants, were determined to be 322.58 mg·g −1 and 0.0615 dm 3 ·mg −1 , correspondingly (Table 2). A dimensionless constant, the equilibrium factors controlling R L [47] describes the fundamental features of the Langmuir isotherm equation given by Equation (7): The form of the isotherm is specified by the R L value, where b is the Langmuir constant and Co is the initial concentration (mg·g −1 ). For adsorption, the R L values between zero and one are optimal. All the concentrations of Co +2 studied had RL values between 0.0107 and 0.0514. The formula for the Freundlich isotherm is expressed in Equation (8) and its logarithmic form is expressed in Equation (9) [47]: where k f is the adsorption capacity and n is the adsorption intensity. Figure 12B is a linear plot of log q e versus log C e , and the Freundlich constants and k f and n values of the adsorption of Co +2 by the TZAB are listed in Table 2. The form of the Dubinin-Radushkevich isotherm is expressed in Equation (10), and the linear Dubinin-Radushkevich (D-R) isotherm is expressed in Equation (11) [48][49][50]: q e = q m e −Bε 2 (10) ln q e = ln q m − Bε 2 (11) where q m is the theoretical saturation capacity in mol·g −1 ; β is the constant proportional to the average free energy of adsorption per mole of the adsorbate per mole mol 2 ·J −2 ; and ε is the Polanyi potential proportional to the equilibrium concentration, which can be calculated by using Equation (12): where C e is the equilibrium adsorbate concentration in the solution (mol·L −1 ), T ( • K) is the absolute temperature, and R is the constant of universal gas (8.314 J mol −1 ·K −1 ). From the linear plot of ln q e vs. ε 2 , the D-R constants q m and β can be derived, which are presented in Table 2. In order to approximate the mean free energy E (kJ·mol −1 ) of adsorption per molecule of the adsorbate during its transfer from infinity in the solution to the surface of the solid, the used constant can be calculated by using Equation (13): The value of this parameter specifies whether the sorption mechanism is physical or an ion exchange. Adsorption proceeds via an ion exchange for ED values ranging from 8 to 16 kJ mol −1 and is of a physical nature for ED values below 8 kJ mol −1 [51,52]. Adsorption in this study had a mean free energy of 8.01 kJ mol −1 , which is consistent with an ion-exchange process, as shown in Figure 12C. Table 2 displays the correlation parameters, which showed that the Langmuir equation had a stronger correlation with the adsorption process than the Freundlich equation, despite the latter having a higher correlation coefficient (R 2 ). The findings demonstrated that monolayer adsorption processes were occurring.

Effect of Adsorption Temperature
The effect of temperature on Co +2 ions sorption when using the TZAB adsorbent was studied at 0.08 g of TZAB that was added to 1500 ppm of Co +2 at pH 7.5 with a 90 min contact time in the temperature range from 25 • C to 70 • C. The obtained results are presented in Figure 13, which demonstrate that increasing the temperature led to a reduction in the uptake capacity of Co +2 by the TZAB adsorbent, indicating that temperature had a positive influence on the sorption of Co +2 ions by the TZAB and that the uptake was an endothermic process.

Thermodynamic Investigation
To investigate the thermodynamic performance of the Co +2 ion sorption reaction system on the TZAB, enthalpy (ΔH), Gibbs free energy (ΔG), and entropy (ΔS) were calculated. These thermodynamic parameters were calculated by using Equations (14) and (15) where K is the reaction constant, T (°K) is the absolute temperature, and R is the universal constant of gas (8.314 J/mol·K). Table 3 displays the thermodynamic factors controlling the adsorption processes that were determined from experiments conducted at temperatures of 298, 313, 323, 333, and 343 °K. The values of ΔS and ΔH could be derived from the slope of the intersection between the Log Kd against the 1/T plot, as shown in Figure 14. As the obtained value of ΔH was positive, this means that the sorption of Co +2 onto the TZAB sorbent was endothermic. The sorption of Co +2 by the TZAB led to a rise in the randomness of the solid-liquid interface due to the positive ΔS value. Since ΔG was negative, this means that Co +2 adsorption onto the TZAB adsorbent occurred spontaneously.
Δ G° (kJ mol −1 ) Figure 13. The effect of temperature on the adsorption of Co +2 on TZAB.

Thermodynamic Investigation
To investigate the thermodynamic performance of the Co +2 ion sorption reaction system on the TZAB, enthalpy (∆H), Gibbs free energy (∆G), and entropy (∆S) were calculated. These thermodynamic parameters were calculated by using Equations (14) and (15) [53][54][55]: where K is the reaction constant, T ( • K) is the absolute temperature, and R is the universal constant of gas (8.314 J/mol·K). Table 3 displays the thermodynamic factors controlling the adsorption processes that were determined from experiments conducted at temperatures of 298, 313, 323, 333, and 343 • K. The values of ∆S and ∆H could be derived from the slope of the intersection between the Log Kd against the 1/T plot, as shown in Figure 14. As the obtained value of ∆H was positive, this means that the sorption of Co +2 onto the TZAB sorbent was endothermic. The sorption of Co +2 by the TZAB led to a rise in the randomness of the solid-liquid interface due to the positive ∆S value. Since ∆G was negative, this means that Co +2 adsorption onto the TZAB adsorbent occurred spontaneously.

Selectivity of TZAB for Metal Ions
The selectivity of the used adsorbent was investigated by studying the adsorption behavior of Co +2 in the presence of metal ions in the solution. The effect of the presence of varying concentrations of Mn(II), Ni(II), Fe(II), and Li(I) in the range from 10 to 250 mg/L on the sorption efficiency of Co +2 when using the TZAB adsorbent was investigated, which explained the Co +2 competition for adsorption sites in the presence of other metal ions. The obtained results presented in Figure 15 indicate that the selectivity of the TZAB was not affected by the presence of Li(I) ions, was a little affected by the presence of Mn(II) and Ni(II), and was moderately affected by the presence of Fe(II), which resulted in a reduction in the adsorption efficiency to 82% when the concentration of iron was 250 ppm. This can be attributed to the ability of the TZAB adsorbent to adsorb foreign cations through a chelation mechanism.

Selectivity of TZAB for Metal Ions
The selectivity of the used adsorbent was investigated by studying the adsorption behavior of Co +2 in the presence of metal ions in the solution. The effect of the presence of varying concentrations of Mn(II), Ni(II), Fe(II), and Li(I) in the range from 10 to 250 mg/L on the sorption efficiency of Co +2 when using the TZAB adsorbent was investigated, which explained the Co +2 competition for adsorption sites in the presence of other metal ions. The obtained results presented in Figure 15 indicate that the selectivity of the TZAB was not affected by the presence of Li(I) ions, was a little affected by the presence of Mn(II) and Ni(II), and was moderately affected by the presence of Fe(II), which resulted in a reduction in the adsorption efficiency to 82% when the concentration of iron was 250 ppm. This can be attributed to the ability of the TZAB adsorbent to adsorb foreign cations through a chelation mechanism.

Elution and Regeneration of TZAB Adsorbent
The absorbed Co +2 on the surface of the TZAB was recovered from the TZAB by utilizing several eluents, namely 0.5 M solutions of different acids (HCl, H 2 SO 4 , EDTA, and HNO 3 ). The leaching of the adsorbed Co +2 ion from the sorbents was also tested by using deionized water as a control. The highest Co +2 ion recovery of 85.72% from the TZAB was obtained by using a 0.5 M HCl solution preceded by HNO 3 , H 2 SO 4 , and EDTA solutions, as presented in Figure 16. Figure 16A shows that the most efficient eluent type for the recovery of Co +2 was HCl, which was capable of recovering 85.72% of the loaded Co +2 . The effect of the HCl concentration on the percent recovery of Co +2 was investigated by applying different concentrations of HCl in the range from 0.1 to 2 M, and the obtained results are presented in Figure 16B. The results showed that using 1 M HCl could result in the recovery of 91.7% of the loaded Co +2 from the TZAB adsorbent. Finally, the effect of the elution time on the Co +2 recovery from the loaded TZAB adsorbent was investigated by varying the elution time in the range from 5 to 90 min, and the obtained results are presented in Figure 16C. It is clear from Figure 16C that 50 min was sufficient to recover almost all of the Co +2 on the loaded TZAB. More than 99% of the loaded Co +2 was recovered at a 50 min elution time.
Materials 2023, 16, x FOR PEER REVIEW 18 of 27 Figure 15. Impact of foreign ions on the sorption efficiency of Co +2 by using TZAB adsorbent.

Elution and Regeneration of TZAB Adsorbent
The absorbed Co +2 on the surface of the TZAB was recovered from the TZAB by utilizing several eluents, namely 0.5 M solutions of different acids (HCl, H2SO4, EDTA, and HNO3). The leaching of the adsorbed Co +2 ion from the sorbents was also tested by using deionized water as a control. The highest Co +2 ion recovery of 85.72% from the TZAB was obtained by using a 0.5 M HCl solution preceded by HNO3, H2SO4, and EDTA solutions, as presented in Figure 16. Figure 16A shows that the most efficient eluent type for the recovery of Co +2 was HCl, which was capable of recovering 85.72% of the loaded Co +2 . The effect of the HCl concentration on the percent recovery of Co +2 was investigated by applying different concentrations of HCl in the range from 0.1 to 2 M, and the obtained results are presented in Figure 16B. The results showed that using 1 M HCl could result in the recovery of 91.7% of the loaded Co +2 from the TZAB adsorbent. Finally, the effect of the elution time on the Co +2 recovery from the loaded TZAB adsorbent was investigated by varying the elution time in the range from 5 to 90 min, and the obtained results are presented in Figure 16C. It is clear from Figure 16C that 50 min was sufficient to recover almost all of the Co +2 on the loaded TZAB. More than 99% of the loaded Co +2 was recovered at a 50 min elution time.

Durability of TBAZ for the Sorption of Co +2 Ions
The ability to regenerate ion-imprinted polymers is crucial to their utility in the real world. Hence, TZAB sorption-elution tests were studied. In this case, 20 mL of a Co +2 solution was added to 0.08 g of adsorbent and agitated for 90 min at 70 °C before the Co +2 concentration was determined. By using an a1M HCl solution, the TZAB was

Durability of TBAZ for the Sorption of Co +2 Ions
The ability to regenerate ion-imprinted polymers is crucial to their utility in the real world. Hence, TZAB sorption-elution tests were studied. In this case, 20 mL of a Co +2 solution was added to 0.08 g of adsorbent and agitated for 90 min at 70 • C before the Co +2 concentration was determined. By using an a1M HCl solution, the TZAB was regenerated. The obtained results of the TZAB adsorbent regeneration are shown in Figure 17. It was noted that after five cycles of recycling, the TZAB still had a high uptake capacity, with an efficiency of over 97%. This confirms the actual utilization of the TZAB adsorbents in the wastewater treatment process. Based on the obtained results of the current investigation, the TZAB shows promising potential for adsorbent utilization for Co +2 separation in a real wastewater sample.

Durability of TBAZ for the Sorption of Co +2 Ions
The ability to regenerate ion-imprinted polymers is crucial to their utility in the real world. Hence, TZAB sorption-elution tests were studied. In this case, 20 mL of a Co +2 solution was added to 0.08 g of adsorbent and agitated for 90 min at 70 °C before the Co +2 concentration was determined. By using an a1M HCl solution, the TZAB was regenerated. The obtained results of the TZAB adsorbent regeneration are shown in Figure 17. It was noted that after five cycles of recycling, the TZAB still had a high uptake capacity, with an efficiency of over 97%. This confirms the actual utilization of the TZAB adsorbents in the wastewater treatment process. Based on the obtained results of the current investigation, the TZAB shows promising potential for adsorbent utilization for Co +2 separation in a real wastewater sample.  In order to give more attention to the advantages and the importance of the synthesized adsorbent, a comparison between different adsorbents prepared for the adsorption of Co +2 is presented in Table 4. It was noted that the prepared TZAB adsorbent had a maximum adsorption capacity of 319.7 mg·g −1 at the optimum operation conditions, which is higher than most other sorbents for which data are available. Scheme 2 presents the proposed possible chelation and adsorption mechanism for the Co +2 -TZAB interaction, involving the imine's lone pair of electrons and the long pairs of electrons found in hydroxyl groups.
Magnetite-alginate nanoparticles 33.6 [67] Triazol Schiff base derivatives (TZAB) 319.7 Current study Scheme 2 presents the proposed possible chelation and adsorption mechanism for the Co +2 -TZAB interaction, involving the imine's lone pair of electrons and the long pairs of electrons found in hydroxyl groups. Scheme 2. The proposed mechanism of interaction between Co +2 metal ions and TZAB adsorbent.

Application of TZAB Adsorbent in Processing Recycled Li-Ion Batteries
In this section, the Li-ion batteries collected from laptops fitted with LiCoO2 (ICR) cathodes obtained from the secondary IT device market and repair shops are utilized for the extraction of Co +2 metal ions. The plastic container covering the cells was removed by hand sorting. To prevent the occurrence of a short circuit, the cells were first submerged in an electrolyte solution of 5% NaCl w/v for one day before being removed, were rinsed in deionized water, and were dried at 90 °C for 12 h. Then, a manual opening was carried out by cutting a cross section through the metal cap. After cutting away the steel casings of the cell, the contents of the cell were sorted into their different component parts: plastic, aluminum sheets of the cathodes, and copper sheets of the anodes. The powdered cathodic active material was easily removed from the aluminum sheets by heating them in the temperature range of 250 °C to 300 °C for 30 min. The recovered powder was milled to a mesh size of −200 µm before being sieved.
The leaching experiments were conducted by using sulfuric acid with a 2 M concentration at 60 °C for 60 min at a 40 g/L solid/liquid ratio and a 15% hydrogen Scheme 2. The proposed mechanism of interaction between Co +2 metal ions and TZAB adsorbent.

Application of TZAB Adsorbent in Processing Recycled Li-Ion Batteries
In this section, the Li-ion batteries collected from laptops fitted with LiCoO 2 (ICR) cathodes obtained from the secondary IT device market and repair shops are utilized for the extraction of Co +2 metal ions. The plastic container covering the cells was removed by hand sorting. To prevent the occurrence of a short circuit, the cells were first submerged in an electrolyte solution of 5% NaCl w/v for one day before being removed, were rinsed in deionized water, and were dried at 90 • C for 12 h. Then, a manual opening was carried out by cutting a cross section through the metal cap. After cutting away the steel casings of the cell, the contents of the cell were sorted into their different component parts: plastic, aluminum sheets of the cathodes, and copper sheets of the anodes. The powdered cathodic active material was easily removed from the aluminum sheets by heating them in the temperature range of 250 • C to 300 • C for 30 min. The recovered powder was milled to a mesh size of −200 µm before being sieved.
The leaching experiments were conducted by using sulfuric acid with a 2 M concentration at 60 • C for 60 min at a 40 g/L solid/liquid ratio and a 15% hydrogen peroxide concentration, which resulted in the extreme leaching efficiencies of the Co +2 and Li metal ions. Co +2 is more leachable with H 2 SO 4 because hydrogen peroxide causes a reduction of Co from Co +3 to Co +2 . In terms of stability, Co +2 is more stable than Co +3 . Both Li and Co are leached even at the minimum sulfuric acid concentration [68]. The leaching process of LiCoO 2 in the H 2 SO 4 solution was carried out in accordance with Equation (16) [69]: 2LiCoO 2(s) + 3H 2 SO 4(aq) + H 2 O 2(aq) → 2CoSO 4(aq) + Li 2 SO 4(aq) + 4H 2 O (g) + O 2(g) (16) In order to separate the leachate solution from the insoluble residues, a La fil 400 vacuum filtration system was employed, and Whatman Grade GF/B filter paper (12.5 cm size) was employed for the filtering. ICP-OES was used to examine the metal value content of the Co and Li in the liquid samples, as shown in Table 5. The physical analysis of the black cathodic material by X-ray diffraction presented in Figure 18A revealed that the Li and Co metal ions were presented in the form of LiCoO 2 , which considered the principal source of the cathode active material. All the sharp peaks in the diffraction pattern referenced LiCoO 2 , and no additional peaks were visible. It was noted that the high crystallinity regenerated material formed because of the characteristic peak's sharpness. A SEM analysis was also performed on the black powder. The particles had a fibrous crystallite shape, as observed on the deposit surface in Figure 18B [70]. Therefore, the LiCoO 2 powders derived from the used LIBs cannot be used directly as active materials in cathode production unless they are first recovered and purified.
visible. It was noted that the high crystallinity regenerated material formed because of the characteristic peak's sharpness. A SEM analysis was also performed on the black powder. The particles had a fibrous crystallite shape, as observed on the deposit surface in Figure 18B [70]. Therefore, the LiCoO2 powders derived from the used LIBs cannot be used directly as active materials in cathode production unless they are first recovered and purified. Ten grams of the spent black powder of the cathode was subjected to a leaching process by using 250 mL of 2M sulfuric acid in the presence of 15% hydrogen peroxide at 60 °C for 60 min. The obtained leach liquor was filtrated, and the cobalt and lithium content were measured by using ICP-OS; the concentration of Co +2 was found to be 5612 ppm while the lithium concentration was 1091 ppm. The second step was applying the best controlling parameters that were optimized by using the TZAB adsorbent for the Ten grams of the spent black powder of the cathode was subjected to a leaching process by using 250 mL of 2 M sulfuric acid in the presence of 15% hydrogen peroxide at 60 • C for 60 min. The obtained leach liquor was filtrated, and the cobalt and lithium content were measured by using ICP-OS; the concentration of Co +2 was found to be 5612 ppm while the lithium concentration was 1091 ppm. The second step was applying the best controlling parameters that were optimized by using the TZAB adsorbent for the adsorption of Co +2 from the black powder leach liquor so that 1 g of the TZAB was speared on 250 mL of the spent batteries' cathode leach liquor. The solution was adjusted at 7.5 pH (by using 1 M of NH 4 OH or 1 M H 2 SO 4 ) and stirred for 60 min at 70 • C. It was noted that the maximum leaching efficiency of the Co +2 was 95%, and then the Co +2 loaded on the TZAB was subjected to an elution process by using a 1M HCl solution that was stirred for 50 min at 25 • C. The obtained liquor was subjected to precipitation by using ammonium oxalate and by adjusting the solution pH to 1.5 and stirring speed to 300 rpm for 60 min at 75 • C in accordance with Equation (17). It has been suggested that the following process can be used to recover cobalt from ammonium oxalate; after numerous washes and drying, the resulting solids were analyzed by using a SEM-EDX analysis: The recovered CoC 2 O 4 from the extraction processes was characterized by using XRD and SEM-EDX analyses. The obtained XRD analysis is presented in Figure 19A, and micrographs of the resultant product are presented in Figure 19B. Figure 19 illustrates the results of an X-ray diffraction (XRD) analysis on the crystal structure of the cobalt oxalate product. According to the pattern, all the diffraction peaks exhibited properties of the cobalt oxalate phase, which can be indexed to the orthorhombic phase of CoC2O4.H2O (JCPDS No. 25-0250) [71].
The residual filtrates after separating CoC 2 O 4 contained all lithium, which was subjected to precipitation by using phosphoric acid. Then, the pH of the leaching liquor was adjusted by using NaOH and heating the solution to 70 • C at a 300 rpm stirring speed for 60 min to produce pure Li 3 PO 4 according to Equation (16). The obtained Li 3 PO 4 precipitate was characterized by using XRD and SEM-EDX analyses, as presented in Figure 20A,B. The precipitation and purification procedure, which included multiple washes with distilled water, resulted in a relatively pure Li 3 PO 4 product (with a purity of 98.3%). One possible reaction for lithium recovery is described in Equation (18) analyzed by using a SEM-EDX analysis: Li + (aq) + Co +2 (aq) + (NH4)2C2O4(aq) → CoC2O4(s) + Li + (aq) + 2NH + (aq) (17 The recovered CoC2O4 from the extraction processes was characterized by using XRD and SEM-EDX analyses. The obtained XRD analysis is presented in Figure 19A and micrographs of the resultant product are presented in Figure 19B. Figure 19 illustrates the results of an X-ray diffraction (XRD) analysis on the crysta structure of the cobalt oxalate product. According to the pattern, all the diffraction peaks exhibited properties of the cobalt oxalate phase, which can be indexed to the orthorhombic phase of CoC2O4.H2O (JCPDS No. 25-0250) [71]. The residual filtrates after separating CoC2O4 contained all lithium, which was subjected to precipitation by using phosphoric acid. Then, the pH of the leaching liquo was adjusted by using NaOH and heating the solution to 70 °C at a 300 rpm stirring speed for 60 min to produce pure Li3PO4 according to Equation (16). The obtained Li3PO precipitate was characterized by using XRD and SEM-EDX analyses, as presented in Figure 20A,B. The precipitation and purification procedure, which included multiple washes with distilled water, resulted in a relatively pure Li3PO4 product (with a purity o 98.3%). One possible reaction for lithium recovery is described in Equation (18): 3Li + (aq) + H2PO4 − (aq) + 2NaOH(aq) → Li3PO4(s) + 2Na + (aq) + 2H2O (18 The XRD analysis of the white precipitate of lithium phosphate shows that the diffraction lines of the precipitated solid corresponded to Li3PO4 (JCPDS 015-0760) while the SEM analysis showed that lithium phosphate particles had an olivine structure with a diagonal length between 1 and 2 µm [42]. The proposed flowsheet of the cobalt and lithium extraction from the spent LIBs by using a novel synthesized (TZAB) adsorbent is presented in Figure 21. The XRD analysis of the white precipitate of lithium phosphate shows that the diffraction lines of the precipitated solid corresponded to Li 3 PO 4 (JCPDS 015-0760), while the SEM analysis showed that lithium phosphate particles had an olivine structure with a diagonal length between 1 and 2 µm [42].
The proposed flowsheet of the cobalt and lithium extraction from the spent LIBs by using a novel synthesized (TZAB) adsorbent is presented in Figure 21. The proposed flowsheet of the cobalt and lithium extraction from the spent LIBs by using a novel synthesized (TZAB) adsorbent is presented in Figure 21.

Conclusions
The global increasing interest in clean and green energy resources and environmental restrictions has led to the production of a huge number of energy storage batteries. One of the promising types of these batteries is LIBs, which have shown advanced operational and technological properties. Due to the significant increase in the consumption of lithium batteries, a huge number of discarded lithium batteries will be generated accordingly. The present study aimed to explore the processing of discarded LIBs by using ecofriendly and cost-effective processes to reduce the negative environmental effects and at the same time utilize them to produce valuable metals. The proposed technique presented here applies a novel synthesized solid-phase (TZAB) adsorbent in the hydrometallurgical processing operation to selectively remove cobalt and lithium from synthetic solutions and discarded LIBs.
The obtained results showed that the optimum conditions for the maximum recovery of Co(II) from synthetic solutions were as follow: C 0 = 500 mg·L −1 , dose of 0.08 g, pH 7.5, T = 25 • C, and reaction time = 90 min. The collected data from Langmuir's isotherm and the adsorption processes of Co agreed with the data predicted by the D-R isotherm models, which showed that the adsorption of Co(II) onto TZAB appeared to be chemisorption, and the results were in good agreement with the Langmuir and D-R isotherm models. The experimental data on dynamics also fit the pseudo second-order kinetic equation nicely. According to the thermodynamic data, it was determined that the reaction behavior was spontaneous and endothermic.
The application of the novel synthesized adsorbent and the optimized adsorption conditions on the selected sample of discarded lithium-ion batteries led to the recovery of high-purity cobaltous oxalate and lithium phosphate. High-purity CoC 2 O 4 and Li 3 PO 4 were obtained with a purity of 95% and 98.3% and a percent recovery of 93.48% and 95.76%, respectively. The synthesized TZAB adsorbent is one of the highly recommended adsorbents due to its high adsorption capacity and cost effectiveness in comparison with other adsorbents. All this enhances its application in the processing of spent LIBs for the selective adsorption of Co(II) and lithium.