Ecofriendly Composite as a Promising Material for Highly-Performance Uranium Recovery from Different Solutions

The development of new materials based on biopolymers (as renewable resources) is substantial for environmental challenges in the heavy metal and radionuclide ions removal contaminations. Functionalization of chitosan with sulfonic groups was achieved for improving the uranium sorption, not only from slightly acidic leachate, but also for the underground water. The prepared hydrogel based on chitosan was characterized by series of analysis tools for structure elucidation as FTIR spectroscopy, textural properties using nitrogen adsorption method, pHPZC (by pH-drift method), thermogravimetric analysis (TGA), SEM, and SEM-EDX analyses. The sorption was performed toward uranium (VI) ions for adjustment of sorption performances. The optimum sorption was performed at pH 4 (prior to the precipitation pH). The total sorption was achieved within 25 min (relatively fast kinetics) and was fitted by pseudo-first order rate equation (PFORE) and resistance to intraparticle diffusion equation (RIDE). The maximum sorption capacity was around 1.5 mmol U g−1. The sorption isotherms were fitted by Langmuir and Sips equations. Desorption was achieved using 0.3 M HCl solution and the complete desorption was performed in around 15 min of contact. The sorption desorption cycles are relatively stable during 5 cycles with limit decreasing in sorption and desorption properties (around 3 ± 0.2% and 99.8 ± 0.1%, respectively). The sorbent was used for removal of U from acid leachate solution in mining area. The sorbent showed a highly performance for U(VI) removal, which was considered as a tool material for radionuclides removing from aquatic medium.


Introduction
The hazardous metal removal and the valuable metal recovery are challenging techniques for water purification and metal valorization. Different processes were used either in leaching of metal ions from ores, waste materials or extraction processes from solution. The green leaching using Humic acid (HA), as well as mineral acids, were used for removing of uranium from crude and spent materials [1][2][3][4]. For this purpose, several techniques were used including solvent extraction, metal precipitation, and membrane-based techniques, which faced limited use on the concentration level of metal ions and the solution complexity. Sorption is the more specifically used in the low concentration of metal ions. Although there is a large variety of commercial resins, there is a demand for developing special types of sorbents (nano particles size or hydrogel) for the removal of heavy metal ions as well as recovering of valuable/economic metals.

Synthesis of the Reference Material (Chitosan Crosslinked)
Dissolving of 2 g of chitosan particles in 30 mL of 7% (v/v) acetic acid solution was performed in a three nicked flask (equipped with condenser, agitator, and thermostat). Addition of 5 mL (15% v/v) glutaraldehyde solution dropwise with vigorous stirring. The produced precipitation was continued stirring (with velocity 190 rpm) for 5 h at 75 °C before filtered and washed with acetone and water to remove the unreacted materials and dried at 60 °C for 10 h to yield CH, as shown in Scheme 1. Scheme 1. Synthesis of the CH sorbent (as a reference material).

Synthesis of the Functionalized Chitosan Composite
Two grams of chitosan and 0.2 g of potassium persulfate were dissolved in 7% (v/v) acetic acid solution (50 mL) in three nicked flask. There as an addition of 2 g of AMPS and 0.1 g of MBA (as a crosslinker) to the solution with vigorous stirring (190 rpm) till dissolve. The flask was equipped with a spiral condenser and heated at 75 °C for 9 h under the vigorous stirring conditions. After cooling, the mixture was poured to a 500 mL solution of NaOH (0.5% (w/v)) contains 15% v/v glutaraldehyde solution (for enhancing the stability through further crosslinking effect) for 10 h at room temperature (21 ± 2 °C) with gentle stirring (95 rpm). The precipitated hydrogel was filtered and washed several times with deionized water and acetone then dried at 60 °C for 10 h to yield CH-S as shown in Scheme 2. Scheme 1. Synthesis of the CH sorbent (as a reference material).

Synthesis of the Functionalized Chitosan Composite
Two grams of chitosan and 0.2 g of potassium persulfate were dissolved in 7% (v/v) acetic acid solution (50 mL) in three nicked flask. There as an addition of 2 g of AMPS and 0.1 g of MBA (as a crosslinker) to the solution with vigorous stirring (190 rpm) till dissolve. The flask was equipped with a spiral condenser and heated at 75 • C for 9 h under the vigorous stirring conditions. After cooling, the mixture was poured to a 500 mL solution of NaOH (0.5% (w/v)) contains 15% v/v glutaraldehyde solution (for enhancing the stability through further crosslinking effect) for 10 h at room temperature (21 ± 2 • C) with gentle stirring (95 rpm). The precipitated hydrogel was filtered and washed several times with deionized water and acetone then dried at 60 • C for 10 h to yield CH-S as shown in Scheme 2.

Characterization of Materials
The produced sorbents (CH and CH-S) were subjected to grind and sieving. The sorbents that used in the experiments were obtained with scale up to 10 µm. The (C, S, N and H composition) was measured using elemental analysis through element analyzer; CHNOS; Vario ELIII, Elementar-Analyzer system; GmbH, Sonaustraβe-20354 Hamburg, Germany. Chemical analysis and morphological studies were performed by the scanning electron microscope joint with the energy dispersive X-ray analyzer (SEM and EDX, respectively); XL30-ESEM; Philips, Thermo Fisher Scientific, Hillsboro, OR, USA. FTIR spectroscopy (Fourier-transform infrared) were used from the Mobile IR-Portable; Bruker Optics, Billerica, MA, USA. The textural properties of the synthesized material were carried out through the high-speed surface area analyzer using Nova-e Series, Model-25, Quantachrome, Kingsville, TX, USA. The thermal analysis for material degradation was carried out by the TGA thermogravimetric analyzer; N5320011-Perkin Elmer, Villebon-sur Yvette, France), using nitrogen atmosphere as medium for the analysis, with 10 • C min −1 as a temperature ramp. The pH PZC (zero-charge) was measured by the pH-drift method; a 100 mg of the prepared sorbents (both CH and CH-S) were mixed with 50 mL of series of prepared solution (11 prepared samples in closed bottle) with concentration of 0.1 M NaCl at fixed pH 0 (initial pH), that ranged between 1 and 11. After stirring for around 48 h, the pH f (final pH) was measured (using pH meter with the specification described below) and the difference in pH values of the initial and final were determined, in which the pH PZC was equal to pH 0 = pH f . The pH of the solution was established through pH/ionometer, S220 Seven compact, Mettler Toledo-China. The collected solution (samples after pH effect, sorption isotherms, uptake kinetics, desorption, selectivity and after treatment with real samples) was firstly filtrated using micromembrane (1.2 µm) before measuring the metal contents.

Characterization of Materials
The produced sorbents (CH and CH-S) were subjected to grind and sieving. The sorbents that used in the experiments were obtained with scale up to 10 μm. The (C, S, N and H composition) was measured using elemental analysis through element analyzer; CHNOS; Vario ELIII, Elementar-Analyzer system; GmbH, Sonaustraβe-20354 Hamburg, Germany. Chemical analysis and morphological studies were performed by the scanning electron microscope joint with the energy dispersive X-ray analyzer (SEM and EDX, respectively); XL30-ESEM; Philips, Thermo Fisher Scientific, Hillsboro, OR, USA. FTIR spectroscopy (Fourier-transform infrared) were used from the Mobile IR-Portable; Bruker Optics, Billerica, MA, USA. The textural properties of the synthesized material were carried out through the high-speed surface area analyzer using Nova-e Series, Model-25, Quantachrome, Kingsville, TX, USA. The thermal analysis for material degradation was carried out by the TGA thermogravimetric analyzer; N5320011-Perkin Elmer, Villebon-

Sorption Procedures
The batch method (agitation technique) was used for carrying out the uranium sorption tests in closed bottles. Fixed volume of the solution (V, L), have a fixed concentration of the metal ions (C 0 , mmol L −1 ) at initial pH 0 value (before sorption), this solution was mixed with a specific amount of the sorbent (m, g) in a specific time (t, hours) at room temperature (21 ± 1 • C).
For the uptake kinetics, the samples collected from this experiment at each specific time were filtrated using filter membrane (with specification 1.2 µm). The experimental conditions were carefully adjusted in the specific experiments. The standard condition is as follow; the sorbent with size below 10 µm were added to solution with initial metal concentration (C 0 ) around 100 (±5) mg U L −1 (corresponding to 0.42 mmol U L −1 ); at initial pH value (pH 0 ) 4; with sorbent dose (which described as amount of sorbent in a specific volume of the solution (SD; m/V)): 0.833 g L −1 and agitated for 24 h. The pH of the mixture wasn't adjusted through the sorption processes but the pH eq (equilibrium pH) was monitored after sorption experiment.
The sorption isotherms were used with different initial uranyl concentration that varied between 0.04 (±0.02) and 2.00 (±0.05) mmol U L −1 . The models used for uptake kinetics and sorption isotherms are listed in Tables S1 and S2. Desorption experiments were investigated using 0.3 M HCl solution, it was tested from the sorbents collected after treatment in the kinetic experiments (uranium-loaded sorbent; around 0.650 g sorbent in each exp.). The condition used in the desorption procedure is as follow; the eluent volume 250 mL (SD: 2.52 (±0.02) g L −1 ) and the total time of desorption experiment is around 4 h. The recycling experiment was used with the same procedures in which, the water rinsing steps (approximately 30 (±5) mL) were performed between each sorption/desorption run.
The residual concentration (C eq , mmol U L −1 ) was analyzed using an inductively coupled plasma atomic emission spectrometer (ICP-AES) for synthetic and nature solutions. The uranium content in the diluted solution was measured using ICP-AES; Activa M; Horiba/France. The concentration of uranium ions from ore materials and leachate solution was analyzed using ammonium meta vanadate in oxidimetric titration method [47,48], while the measurements of the rare earth elements (REEs) were performed by colorimetric method using Arsenazo III at λ: 654 nm [49,50] through Shimadzu-160A; Shimadzu-Corporation, Kyoto-Japan. The sorption capacity for each element (q, mmol g −1 ) was measured by the mass balance equation: q = (C 0 − C eq ) × V/m.

Ore Specification
Gabal (G) El-Sela area is considered as a signifying portion of late Precambrian early Paleozoic Pan Africa Orogeny. It involves two-mica granite as polymetallic intra-granitic vein-type U-deposits. It is known as the one of the most favorable areas in Egypt for hosting U-mineralization [51][52][53][54][55]. G El-Sela is sited in southern part of Egypt between latitudes 22 • 17 50 -22 • 16 30 E). It is a topographically low, as well as moderate to slightly high, found as remarkably scattered isolated hills that are separated by vast sand sheets ( Figure 1).
Many promising features to locate uranium mineralization were studied, particularly those related to the ENE-WSW shear zone [54,56]. Geology/mineralogy of G. El Sela two mica granite were premeditated by several researchers confirming prevalence of the primary and secondary uranium minerals [54,56,57]. The chemical composition of the collected sample that was used in this study was performed using XRF facilities and reported in Table 1. From chemical composition it was high concentration of U (1158 mg U kg −1 ), while some valuable elements were found in high concentration as REE (1330 mg U kg −1 ) and others in low concentration as V, Zr, Hf, Nb and Ta.

Mineralogical Characteristics of the Studied Sample
Mineralogical characteristics of the studied sample of the G. El Sela were firstly sieved to appropriate liberation size as determined microscopically (0.063-0.5 mm) and then separated into light and heavy fractions by using bromoform (sp. gr. 2.8 g cm −3 ). Different mineral grains were picked from the obtained heavy fractions and carefully investigated under binocular stereomicroscope. The separated grains were examined by SEM attached by EDX microanalysis unit for minerals identification. The results of EDX analysis reports of notable uranium minerals associated with non-radioactive elements. Accordingly, the studied ore material referred to the poly-mineral associations: autunite, uranophane and apatite in association with hematite, goethite and magnetite minerals. while some valuable elements were found in high concentration as REE (1330 mg U kg −1 ) and others in low concentration as V, Zr, Hf, Nb and Ta.

Mineralogical Characteristics of the Studied Sample
Mineralogical characteristics of the studied sample of the G. El Sela were firstly sieved to appropriate liberation size as determined microscopically (0.063-0.5 mm) and then separated into light and heavy fractions by using bromoform (sp. gr. 2.8 g cm −3 ). Different mineral grains were picked from the obtained heavy fractions and carefully investigated under binocular stereomicroscope. The separated grains were examined by SEM attached by EDX microanalysis unit for minerals identification. The results of EDX analysis reports of notable uranium minerals associated with non-radioactive elements. Accordingly, the studied ore material referred to the poly-mineral associations: autunite, uranophane and apatite in association with hematite, goethite and magnetite minerals.

Results of H 2 SO 4 Agitation Leaching Process
From the foregoing study, it can be concluded that H 2 SO 4 agitation leaching technique is more efficient for U leaching efficiency (89.7%) than other techniques (percolation and pelletization) from the studied G El-Sela at the optimum of the leaching conditions as 15% H 2 SO 4 and adding 0.25 M NaCl with a 1/2 solid/liquid ratio at 2 h and 90 • C.

Textural Properties
The functionalization process of the chitosan particles involved increasing in the SSA (specific surface area) through the adsorption/desorption of nitrogen isotherms. The SSA values were increased by functionalization from 5.75 m 2 g −1 (for CH), to 13.7 m 2 g −1 (for CH-S). This is due to the efficient reaction of the MBA and AMPS through crosslinking via C=C (lead to decreasing the size and high network) than that of MBA and chitosan (through C=C and NH 2 , respectively). According to this, the porous volume (volume of micropores) is increased as well from 0.0473 cm 3 g −1 (for CH), to 0.0796 cm 3 g −1 (for CH-S). The other criterion was observed through increasing the cumulative volumes (total volume) of pore from 0.051 to 0.059 cm 3 g −1 .

Thermogravimetric Analysis
The thermal degradation and the derivative thermogram analyses (DTG) were performed for the functionalized chitosan sorbent (CH-S) as shown in Figure 2. It is characterized by two loss steps. The first stage is achieved at around 160 • C, this is attributed to the loss of the surface water (physically adsorbed) and inside the pores, the wight loss at this stage is 5.88%. The second stage of the loss is noticed between 160 • C and 579.9 • C, the additional loss was 88.22% and this was attributed to different modes for the polymer degradation, decomposition of the amine moieties from chitosan, degradation of sulfonic groups (which reports to be in the range of temp. 200-400 • C [59]), polymer network frame [60], and the char decomposition. It was concluded that the total weight loss of this polymer was close to 94.1%. Similar profiles were observed from Akköz et al. [61] through the use of sulfonated-agriculture waste. Several shoulders were found by DTG, the peaks at 43.6 and 192.7 • C for water loss either from the surface or inside the pores, while at 307.4 • C and 457.1 • C for depolymerization and degradation of the functional groups.
The functionalization process of the chitosan particles involved increasing in the SSA (specific surface area) through the adsorption/desorption of nitrogen isotherms. The SSA values were increased by functionalization from 5.75 m 2 g −1 (for CH), to 13.7 m 2 g −1 (for CH-S). This is due to the efficient reaction of the MBA and AMPS through crosslinking via C=C (lead to decreasing the size and high network) than that of MBA and chitosan (through C=C and NH2, respectively). According to this, the porous volume (volume of micropores) is increased as well from 0.0473 cm 3 g −1 (for CH), to 0.0796 cm 3 g −1 (for CH-S). The other criterion was observed through increasing the cumulative volumes (total volume) of pore from 0.051 to 0.059 cm 3 g −1 .

Thermogravimetric Analysis
The thermal degradation and the derivative thermogram analyses (DTG) were performed for the functionalized chitosan sorbent (CH-S) as shown in Figure 2. It is characterized by two loss steps. The first stage is achieved at around 160 °C, this is attributed to the loss of the surface water (physically adsorbed) and inside the pores, the wight loss at this stage is 5.88%. The second stage of the loss is noticed between 160 °C and 579.9 °C, the additional loss was 88.22% and this was attributed to different modes for the polymer degradation, decomposition of the amine moieties from chitosan, degradation of sulfonic groups (which reports to be in the range of temp. 200-400 °C [59]), polymer network frame [60], and the char decomposition. It was concluded that the total weight loss of this polymer was close to 94.1%. Similar profiles were observed from Akköz et al. [61] through the use of sulfonated-agriculture waste. Several shoulders were found by DTG, the peaks at 43.6 and 192.7 °C for water loss either from the surface or inside the pores, while at 307.4 °C and 457.1 °C for depolymerization and degradation of the functional groups.  Figure 3 shows a comparison study of the crosslinked chitosan (before functionalization) and after functionalization process. The FTIR spectra present in this section  Figure 3 shows a comparison study of the crosslinked chitosan (before functionalization) and after functionalization process. The FTIR spectra present in this section represents with full wavenumber ranges, while Figure S1, shows the most important peaks for comparison the shifts and intensity during functionalization or loading and elution processes. The FTIR spectra were performed for sorbent before and after functionalization (CH and CH-S, respectively), after loading and after 5 cycles of sorption desorption for the CH-S. More specifically the -OH, -NH, and -SO 3 H groups are identified and reported in Table 2. As sulfonation was performed on chitosan a new series of peaks were identified associated with substantial changes, the C-S, O-S, and SO 3 H peaks were identified for the modified composite with increasing the intensity of OH and NH stretching bands (derived from the new substates and the sulfonic groups).

FTIR Spectroscopy
Increasing the intensity of the OH and NH bands as functionalization was performed was attributed to the new grafted groups (from the MBA and the sulphonic group) [62,63]. Disappearing of OH band at 649 cm −1 with the new broad band for C-O-S of sulfonic group was observed. Overlapping the N-H bands (which appeared at 1575 cm −1 in CH) with that of C=O for CH-S, verifying the changes occurred in the environment of this groups. There was an appearance of new broad band at 1096 cm −1 which is related to NCS group [64]. The other interested bands were reported in the Table 2. Most of these bands decreased in the intensity or shifts, especially for OH, NH, S-O, NCS, and C=O as uranyl ion adsorbed, represents with full wavenumber ranges, while Figure S1, shows the most important peaks for comparison the shifts and intensity during functionalization or loading and elution processes. The FTIR spectra were performed for sorbent before and after functionalization (CH and CH-S, respectively), after loading and after 5 cycles of sorption desorption for the CH-S. More specifically the -OH, -NH, and -SO3H groups are identified and reported in Table 2. As sulfonation was performed on chitosan a new series of peaks were identified associated with substantial changes, the C-S, O-S, and SO3H peaks were identified for the modified composite with increasing the intensity of OH and NH stretching bands (derived from the new substates and the sulfonic groups). Increasing the intensity of the OH and NH bands as functionalization was performed was attributed to the new grafted groups (from the MBA and the sulphonic group) [62,63]. Disappearing of OH band at 649 cm −1 with the new broad band for C-O-S of sulfonic group was observed. Overlapping the N-H bands (which appeared at 1575 cm −1 in CH) with that of C=O for CH-S, verifying the changes occurred in the environment of this groups. There was an appearance of new broad band at 1096 cm −1 which is related to NCS group [64]. The other interested bands were reported in the Table 2. Most of these bands decreased in the intensity or shifts, especially for OH, NH, S-O, NCS, and C=O as uranyl ion adsorbed, which shared in the binding mechanism. After five cycles of sorption desorption processes, the spectra restored with full intensity of decreased peaks, confirming the high chemical stability and lack of changes in the chemical structure of the sorbent.   The elemental analysis was performed for each sorbent (CH and CH-S), which appeared in Table 3. As sulfonation was performed (by grafting of AMPS) on chitosan surface, with the MBA crosslinker, it followed an increase of N, O and S contents from 3.44, 26.408 and 0 mmol g −1 to 4.934, 26.952 and 0.683 mmol g −1 , respectively.  Figure 4a,b, shows the semi-quantitative EDX analysis of the CH and after functionalization (CH-S). It shows a trace of Na element (from the sodium hydroxyl solution) in the final synthesis step. However, this analysis was parallel with the elemental analysis for increasing the N, and O as well as the appearance of S in the final sorbent, which is derived from AMPS and MBA.

Elemental Analysis
The elemental analysis was performed for each sorbent (CH and CH-S), which appeared in Table 3. As sulfonation was performed (by grafting of AMPS) on chitosan surface, with the MBA crosslinker, it followed an increase of N, O and S contents from 3.44, 26.408 and 0 mmol g −1 to 4.934, 26.952 and 0.683 mmol g −1 , respectively.  Figure 4a,b, shows the semi-quantitative EDX analysis of the CH and after functionalization (CH-S). It shows a trace of Na element (from the sodium hydroxyl solution) in the final synthesis step. However, this analysis was parallel with the elemental analysis for increasing the N, and O as well as the appearance of S in the final sorbent, which is derived from AMPS and MBA.

Surface Charge-pHPZC
Through applying the pH-drift method for determination of the pHPZC values, Figure  5 shows the result of the pHpzc value. It shows a shift based on acid base properties. The pHPZC is strongly affected by functionalization of the sulfonic acid groups. In fact, the chitosan compound enhances the basic characters, which is derived from the amine and

Surface Charge-pH PZC
Through applying the pH-drift method for determination of the pH PZC values, Figure 5 shows the result of the pH pzc value. It shows a shift based on acid base properties. The pH PZC is strongly affected by functionalization of the sulfonic acid groups. In fact, the chitosan compound enhances the basic characters, which is derived from the amine and hydroxyl groups on the surface. By grafting the sulfonic acid moiety, the acid strength is noticeably changed and shifts to acidic part. The pH PZC decreased from 6.6 to 4.9 for CH and CH-S, respectively. This reflects the effective functionalization of sulfonic groups on the chitosan behavior. On the other words, it means that, the surface of CH remains positively charged at a wide pH range than CH-S and this may cause a repulsion effect (especially at strong acidic pH) with positively charge metal ions. After pH 4.9 the CH-S surface becomes negative, this kind of repulsion is negligible even before this point. The sorbent is partially negatively charged, more specifically on the chelating atoms. Similar results (decreasing in the pH pzc values) were obtained by Akkoz et al. through sulfonation of hawthorn kernel (as agriculture wastes) that decreased from 7 to 3.9 [61], while Urbano and Rivas [73] shows the pH PZC values of 3.4 for the sulfonated groups of polyacrylamide and montmorillonite composites. Figure 6a compares the loading capacities of both sorbents (before and after modification) toward U (VI) ions. Regardless of the type of sorbent, the sorption capacity of U (VI) was progressively increased as pH raised from 1 to 5 before becoming stabilized at pH around 4. It was increased from 0.08 to 0.23 ± 0.02 mmol U g −1 for CH sorbent, and from 0.22 to 0.95 ± 0.05 mmol U g −1 for CH-S. From these data, it was shown that as functional-ization was performed, the loading capacity enhanced by more than 4 times. Increasing the pH caused partial deprotonation of the functional groups and the electrons on the N, O and S are ready for binding through chelating properties. While repulsion between positively charged uranyl ions and protonated groups at acidic pH values exists, on the other side the sorption properties were improved by increasing pH through decreasing the repulsion effects. The three repeated experiments show the successes in the reproducibility properties of the sorbent. Figure 6b shows the pH deviation of the three experiments, it shows deviation of about 0.3 values. From Figure S2, the uranium was found in different species depending on the pH values. The most interesting points are those that lay below pH 4 and 5 for the maximum sorption, before the precipitation point (>5.2) and the existing of hydrolyzed species. The uranyl oxide (UO 2 2+ ) is the mainly sorbed species that are found in the solution (for our case/C 0 , 100 mg L −1 , uranyl nitrate as uranium source, at pH 4), which can bound with the deprotonated (or partially deprotonated) functional groups as NH, OH and SO 3 H. hydroxyl groups on the surface. By grafting the sulfonic acid moiety, the acid strength is noticeably changed and shifts to acidic part. The pHPZC decreased from 6.6 to 4.9 for CH and CH-S, respectively. This reflects the effective functionalization of sulfonic groups on the chitosan behavior. On the other words, it means that, the surface of CH remains positively charged at a wide pH range than CH-S and this may cause a repulsion effect (especially at strong acidic pH) with positively charge metal ions. After pH 4.9 the CH-S surface becomes negative, this kind of repulsion is negligible even before this point. The sorbent is partially negatively charged, more specifically on the chelating atoms. Similar results (decreasing in the pHpzc values) were obtained by Akkoz et al. through sulfonation of hawthorn kernel (as agriculture wastes) that decreased from 7 to 3.9 [61], while Urbano and Rivas [73] shows the pHPZC values of 3.4 for the sulfonated groups of polyacrylamide and montmorillonite composites.  Figure 6a compares the loading capacities of both sorbents (before and after modification) toward U (VI) ions. Regardless of the type of sorbent, the sorption capacity of U (VI) was progressively increased as pH raised from 1 to 5 before becoming stabilized at pH around 4. It was increased from 0.08 to 0.23 ± 0.02 mmol U g −1 for CH sorbent, and from 0.22 to 0.95 ± 0.05 mmol U g −1 for CH-S. From these data, it was shown that as functionalization was performed, the loading capacity enhanced by more than 4 times. Increasing the pH caused partial deprotonation of the functional groups and the electrons on the N, O and S are ready for binding through chelating properties. While repulsion between positively charged uranyl ions and protonated groups at acidic pH values exists, on the other side the sorption properties were improved by increasing pH through decreasing the repulsion effects. The three repeated experiments show the successes in the reproducibility properties of the sorbent. Figure 6b shows the pH deviation of the three experiments, it shows deviation of about 0.3 values. From Figure S2, the uranium was found in different species depending on the pH values. The most interesting points are those that lay below pH 4 and 5 for the maximum sorption, before the precipitation point (>5.2) and the existing of hydrolyzed species. The uranyl oxide (UO2 2+ ) is the mainly sorbed species

Uptake Kinetics
Under the selected experimental conditions (for the pH, sorbent dose and uranium concentration in the solution), the sorption equilibrium is reached during the first 40 min, while around 90% of the total sorption was attained during 25 min as shown in Figure 7 and Figure S3. The superimposition of the three experiments (small in deviation error), which emphasizes the reproducibility. The large pores character (see BET surface area) of the sorbent may explain the fast sorption kinetics and the fast mass transfer, which is controlled through the resistances to film diffusion, as well as the intraparticle diffusion properties, so the resistance to intraparticle diffusion equation (RIDE) cannot be neglected for

Uptake Kinetics
Under the selected experimental conditions (for the pH, sorbent dose and uranium concentration in the solution), the sorption equilibrium is reached during the first 40 min, while around 90% of the total sorption was attained during 25 min as shown in Figures 7 and S3.
The superimposition of the three experiments (small in deviation error), which emphasizes the reproducibility. The large pores character (see BET surface area) of the sorbent may explain the fast sorption kinetics and the fast mass transfer, which is controlled through the resistances to film diffusion, as well as the intraparticle diffusion properties, so the resistance to intraparticle diffusion equation (RIDE) cannot be neglected for the kinetic models. Moreover, the proper sorption rate, which is modeled by pseudo-first order (PFORE); it is described as physical sorption, or pseudo-second order rate equation, PSORE, by correspond the chemical sorption.

Uptake Kinetics
Under the selected experimental conditions (for the pH, sorbent dose and uranium concentration in the solution), the sorption equilibrium is reached during the first 40 min, while around 90% of the total sorption was attained during 25 min as shown in Figure 7 and Figure S3. The superimposition of the three experiments (small in deviation error), which emphasizes the reproducibility. The large pores character (see BET surface area) of the sorbent may explain the fast sorption kinetics and the fast mass transfer, which is controlled through the resistances to film diffusion, as well as the intraparticle diffusion properties, so the resistance to intraparticle diffusion equation (RIDE) cannot be neglected for the kinetic models. Moreover, the proper sorption rate, which is modeled by pseudo-first order (PFORE); it is described as physical sorption, or pseudo-second order rate equation, PSORE, by correspond the chemical sorption.  Hubbe et al. [74] concluded that the PSORE in a lot of cases was inferred with the control of mass transfer through resistance to intraparticle diffusion. Simonin [75] was declared the critical impacts of selection of experimental condition, which was responsible for the quality of the models used (i.e., PFORE and PSORE). Table S1 summarizes the different equations which used in describing of the kinetic profiles. Table 4 reports the experimental values and the parameters for uranium sorption. The values of (R 2 ) of the determination coefficient and the comparisons of both experimental and calculated of the sorption parameters (C(t) fitted /C 0 vs. C(t) exp /C 0 ) are demonstrated that the PFORE and RIDE are more appropriate for kinetic profile modeling. This is also confirmed by the values of AIC, which indicating the lowest (negative) values obtained by these two models. Figure 8 shows the plotted of sorption isotherms (with error bars) for U(VI) sorption from the mono component solution at pH in 4 ± 0.1 (pH eq : 4.1 ± 0.1) using CH-S sorbent. Figure S4 reports the Freundlich and Temkin models for fitting the sorption isotherms of U sorption. It was shown that the sorption capacities are progressively increased with concentration before tends to the saturation plateau (which seems to be high for U(VI) 1.54 mmol U g −1 ).

Sorption Isotherms
The sorption of uranium is controlled by the pH of the solution as well as the uranium species (mainly UO 2 2+ ). The fitted equation for the isotherm profiles is the Langmuir equation. This equation is considered as a good fitting model of the experimental data over the entire range of the uranyl concentrations. The Freundlich equation (fails for fitting the sorption experiments either in the initial or saturation sections) is a powerlike equation. Sips equation (has a good fit in the whole sections), which includes an adjustable parameter (n). From the data collected from Table 5 concerns with the R 2 , variations coefficient of the affinity and AIC values (including the triplicate experiments), the preferred models for fitting the data in Figure 8 is the Langmuir and the Sips equations. The sorption capacity at saturation of the monolayer (i.e., q m,L ) slightly overestimates the experimental values.   Table 6 reports the comparison of U(VI) sorption of some alternative sorbents. It is hard to establish such a comparison due to different functional groups (the bases used) and the detected solution (the source of uranium bearing solution, initial concentration of the uranium ions in either nature liquids or synthetic solution and the uranium salt used in the synthetic solution) but try to make select the matches condition for our work. The sorption capacity is relatively with high values (1.5 mmol U g −1 ). Some sorbents were used at pH 6, with high loading capacity (4.48 mmol g −1 ) using functionalized silica with diethylenetriamine tethered, but there is a risk in our cases of using such condition to avoid precipitation [76]. The other functionalized of mesoporous silica with Phosphonate groups [77] but with lower level of affinity and capacity. Others derived from marine fungus with capacity (about 1.56 mmol U g −1 ) but exhibited a lower affinity coefficient (≈0.38 L mmol −1 ) [78]. The sorbent represents a promising tool for extraction of uranium with respect the kinetic uptake, the capacity, and the affinity coefficients.   Table 6 reports the comparison of U(VI) sorption of some alternative sorbents. It is hard to establish such a comparison due to different functional groups (the bases used) and the detected solution (the source of uranium bearing solution, initial concentration of the uranium ions in either nature liquids or synthetic solution and the uranium salt used in the synthetic solution) but try to make select the matches condition for our work. The sorption capacity is relatively with high values (1.5 mmol U g −1 ). Some sorbents were used at pH 6, with high loading capacity (4.48 mmol g −1 ) using functionalized silica with diethylenetriamine tethered, but there is a risk in our cases of using such condition to avoid precipitation [76]. The other functionalized of mesoporous silica with Phosphonate groups [77] but with lower level of affinity and capacity. Others derived from marine fungus with capacity (about 1.56 mmol U g −1 ) but exhibited a lower affinity coefficient (≈0.38 L mmol −1 ) [78]. The sorbent represents a promising tool for extraction of uranium with respect the kinetic uptake, the capacity, and the affinity coefficients.   Units: t eq : min; q m : mmol U g −1 ; b L : L mmol −1 .

Sorption Mechanism
The collected information from the pH PZC (global charge of the functional groups) and the sorption behavior during different pH values (depending on the speciation of uranyl ions), FTIR analysis (shifts and change the peaks resolution, which used in the interaction models; mainly for OH, SO 3 H and NH), and the data of the EDX analyses (increasing the ratio of some components as S element during synthesis and sorption of uranyl ions, which appeared clearly). It is possible to conclude a different interaction mode of the reactive functional groups on CH-S sorbent and the uranyl ions. The interaction expected to perform through protons on either sulfonic acid, and hydroxyl groups beside the free electrons available on the amine groups, this interaction be mixed of ion exchange and chelating modes, especially that the sorbent is completely negative, and the optimism sorption pH as shown in Figure 9.

Metal Desorption and Recycling Properties
Desorption of adsorbed uranyl ions and recycling of the CH-S sorbent is a key of challenge in valorization and in term of metal recovery. This is the important step in evaluating of the competitiveness process. From FTIR spectra, it was shown the chemical stability of sorbent during recycling process and restoring the original peaks of the sorbent. The composite material produced from the kinetic experiments applied for desorption using 0.3 M HCl solution, which shows fast kinetics. The maximum time required for complete desorption is around 20 min as shown in Figure 10.
From Table 7 shows stability of sorption and desorption recycling which shows a remarkable stability in both sorption (with limited decreasing; around 3% after five cycles) and the desorption efficiency which remains stable (higher than 99.5%). This means that, the prepared composite is shown a remarkably stable of reuses.

Metal Desorption and Recycling Properties
Desorption of adsorbed uranyl ions and recycling of the CH-S sorbent is a key of challenge in valorization and in term of metal recovery. This is the important step in evaluating of the competitiveness process. From FTIR spectra, it was shown the chemical stability of sorbent during recycling process and restoring the original peaks of the sorbent. The composite material produced from the kinetic experiments applied for desorption using 0.3 M HCl solution, which shows fast kinetics. The maximum time required for complete desorption is around 20 min as shown in Figure 10. challenge in valorization and in term of metal recovery. This is the important step in evaluating of the competitiveness process. From FTIR spectra, it was shown the chemical stability of sorbent during recycling process and restoring the original peaks of the sorbent. The composite material produced from the kinetic experiments applied for desorption using 0.3 M HCl solution, which shows fast kinetics. The maximum time required for complete desorption is around 20 min as shown in Figure 10.  Table 7 shows stability of sorption and desorption recycling which shows a remarkable stability in both sorption (with limited decreasing; around 3% after five cycles) and the desorption efficiency which remains stable (higher than 99.5%). This means that, the prepared composite is shown a remarkably stable of reuses.   Results of the uranium extraction applying the optimum leaching conditions upon 200 g of El Sela highly altered granitic rocks. Agitation leaching technique using sulfuric are more efficient than other techniques (percolation and pelletization). Treatment of the collected ore is sampled with 15% H 2 SO 4 in the presence of 0.25 M NaCl with a 1/2 of solid/liquid ratio for 2 h at 90 • C, which yields a solution with uranium leaching efficiency of 89.7%. The produced leaching liquor from 200 g ore sample is about 0.6 L of sulfate solution. The produced solution contains 386 mg U L −1 with pH 0.3. The most interesting metal ions concentration is given in Table 8. The sorption was performed in batch method at different pH values 1 to 5. As pH increased, the sorption efficiency also increased. The capacity of uranium increased from 0.03, 0.156, 0.20, 0.224 and 0.253 mmol U g −1 from pH eq 1.2, 2.3, 3.2, 4.1 to 4.8, respectively. The selectivity coefficient (SC) was increased to pH eq 3.2 then decreased to pH eq 4.8. The SC U/Metal was shown in Figure 11 at the optimum pH eq 3.2, which is around 14.99, 6.67, 29.49, 37.68, 5.22 and 2.70 for Ca, Mg, Fe, Al, Zn, and Pb, respectively. This indicates the efficient uses of the modified chitosan for uranium removal from low concentrate solution.
This can be used for the heavy metal removal of Fe, Zn, and Pb from aquatic medium, which appear to have highly efficient sorption toward these ions.
increased, the sorption efficiency also increased. The capacity of uranium increased from 0.03, 0.156, 0.20, 0.224 and 0.253 mmol U g −1 from pHeq 1.2, 2.3, 3.2, 4.1 to 4.8, respectively. The selectivity coefficient (SC) was increased to pHeq 3.2 then decreased to pHeq 4.8. The SCU/Metal was shown in Figure 11 at the optimum pHeq 3.2, which is around 14.99, 6.67, 29.49, 37.68, 5.22 and 2.70 for Ca, Mg, Fe, Al, Zn, and Pb, respectively. This indicates the efficient uses of the modified chitosan for uranium removal from low concentrate solution. This can be used for the heavy metal removal of Fe, Zn, and Pb from aquatic medium, which appear to have highly efficient sorption toward these ions. Figure 11. Selectivity studies of uranium sorption from acidic ore leachate.

Conclusions
Successive synthesis of novel sorbent based on chitosan particles for high performance uranium recovery was performed through functionalization of sulfonic groups (source; AMPS) on the chitosan surface via redox polymerization. The produced hydrogel Figure 11. Selectivity studies of uranium sorption from acidic ore leachate.

Conclusions
Successive synthesis of novel sorbent based on chitosan particles for high performance uranium recovery was performed through functionalization of sulfonic groups (source; AMPS) on the chitosan surface via redox polymerization. The produced hydrogel was characterized by FTIR spectroscopy, TGA analysis, textural properties (BET surface area) through nitrogen adsorption method, pH PZC (by pH-drift method), SEM, and SEM-EDX analyses. The most favorable pH is around 4 (prior to precipitation limit), the sorption kinetics is relatively fast; it is around 25 min is sufficient for total sorption, and 15 min for the total desorption with more than 99.9% of desorption efficiency. Using 0.3 M HCl solution is efficient eluent. The PFORE and RIDE are the most fitting model for kinetic uptake than the PSORE, while Langmuir and Sips equations for sorption isotherms. The sorbent was applied for uranium recovery from leachate waste solution and is considered as a promising tool for the recovery of uranium from acid leaching in polymetallic solution.