Removal of Ni(II) Ions by Poly(Vinyl Alcohol)/Al2O3 Nanocomposite Film via Laser Ablation in Liquid

Al2O3-poly(vinyl alcohol) nanocomposite (Al2O3-PVA nanocomposite) was generated in a single step using an eco-friendly method based on the pulsed laser ablation approach immersed in PVA solution to be applicable for the removal of Ni(II) from aqueous solution, followed by making a physicochemical characterization by SEM, XRD, FT-IR, and EDX. After that, the effect of adsorption parameters, such as pH, contact time, initial concentration of Ni(II), and medium temperature, were investigated for removal Ni(II) ions. The results showed that the adsorption was increased when pH was 5.3, and the process was initially relatively quick, with maximum adsorption detected within 90 min of contact time with the endothermic sorption process. Moreover, the pseudo-second-order rate kinetics (k2 = 9.9 × 10−4 g mg−1 min−1) exhibited greater agreement than that of the pseudo-first-order. For that, the Ni(II) was effectively collected by Al2O3-PVA nanocomposite prepared by an eco-friendly and simple method for the production of clean water to protect public health.


Introduction
Nano adsorbent materials have sparked tremendous attention in recent years because of their large specific surface area, regular pore structure, and highly controlled surface characteristics. Almost the majority of the adsorbents that are created today to overcome the hazard of heavy metal ions and dyes depend on the engagement of the hazardous chemical compounds with the presence of functional groups on the adsorbents' surfaces [1][2][3][4][5]. As a result, the matrix's vast surface area and many adsorption sites are the most critical elements influencing the adsorbent's adsorption capacity. From hazardous chemical compounds, nickel waste is extremely dangerous to people, ecosystems, and animals. It has been found in a wide range of industrial wastes, including nickel-cadmium batteries, organic compounds, and insecticides [6][7][8][9]. The abundance of nickel ions in the water supply has been linked to a variety of major health issues, including carcinogenic agents. In this work, an Al 2 O 3 -PVA nanocomposite was effectively produced in just one step using the eco-friendly promising tools of the PLAL method to be suitable for nickel ion adsorption from aqueous solutions. The properties of the synthesized hybrid structure were carried out by different techniques. After that, the influence of several factors on the sorption process, such as concentration, contact duration, beginning concentration, and temperature was examined for Ni(II).

Materials
Ultra-pure water was used to make all of the reagents. Poly vinyl alcohol solution (PVA) was purchased from La-113 laboratory, Rasayan, Egypt. Aluminum sheet (Al) with dimension 2 × 2 cm 2 and thickness of 0.1 mm was purchased from the BDH Chemical Ltd. pool, England. Nickel nitrate (NiNO 3 ) was purchased from LOBA Chemie, Laboratory Reagents and fine Chemicals, India, which was used to make a stock solution of Ni(II) ions. Sodium hydroxide (NaOH) and hydrochloric acid (HCl) were purchased from El Nasr Pharmaceutical Co., Giza, Egypt.

Preparation of PVA Solution
A 10 wt.% PVA was produced by dissolving 10 g of PVA in 100 mL of ultra-pure water and maintaining it at 80 • C for 300 min with continued magnetic stirring.

Preparation of Al 2 O 3 -PVA Composite
The Al 2 O 3 nanostructured material was generated by the pulsed laser ablation of cleaned metal targets of Al sheet put in a glass vessel filled with 5 mL of the prepared PVA solution to form an Al 2 O 3 nanostructured material embedding PVA. The laser ablation process produced by the laser beam of the first harmonic generation of nanosecond Nd:YAG laser, which produces a 10 Hz repetition rate and 150 mJ of laser energy. The ablation process was carried out by focusing the laser beam on the target's surface with a plancoconvex lens (70 mm) to produce a small spot that had a 20 µm diameter ( Figure 1). The ablation procedure was carried out under mechanical stirring for 30 min to create distinct nanocomposite structures. Then, the prepared nanocomposite solution was separately cast in a glass Petri-dish to obtain the required films, followed by drying in glass Petri dishes with a thickness of about 2 mm in the form of free-standing and a diameter of 25 mm. The amount of immobilized Al 2 O 3 NPs in PVA could be estimated in two ways: the first method was related to measuring the weight of the Al-sheet before and after the ablation process, followed by subtraction of the two values (weight Al sheet -weight ablated Al sheet ) to estimate the amount of immobilized Al 2 O 3 NPs in PVA. The second method was related to measuring the weight of PVA film before and after being embedded with Al 2 O 3 NPs, followed by subtraction of the two values (weight embedded PVA film -weight pure PVA film ) to estimate the amount of immobilized Al 2 O 3 NPs in PVA. After using both methods and repeating each method three times, it was detected that the amount of embedded Al 2 O 3 in the PVA film is 9.2 µg ± 0.051.

Preparation of Al2O3-PVA Composite
The Al2O3 nanostructured material was generated by the pulsed laser ablation of cleaned metal targets of Al sheet put in a glass vessel filled with 5 mL of the prepared PVA solution to form an Al2O3 nanostructured material embedding PVA. The laser ablation process produced by the laser beam of the first harmonic generation of nanosecond Nd:YAG laser, which produces a 10 Hz repetition rate and 150 mJ of laser energy. The ablation process was carried out by focusing the laser beam on the target's surface with a planco-convex lens (70 mm) to produce a small spot that had a 20 µm diameter ( Figure 1). The ablation procedure was carried out under mechanical stirring for 30 min to create distinct nanocomposite structures. Then, the prepared nanocomposite solution was separately cast in a glass Petri-dish to obtain the required films, followed by drying in glass Petri dishes with a thickness of about 2 mm in the form of free-standing and a diameter of 25 mm. The amount of immobilized Al2O3 NPs in PVA could be estimated in two ways: the first method was related to measuring the weight of the Al-sheet before and after the ablation process, followed by subtraction of the two values (weight Al sheet-weight ablated Al sheet) to estimate the amount of immobilized Al2O3 NPs in PVA. The second method was related to measuring the weight of PVA film before and after being embedded with Al2O3 NPs, followed by subtraction of the two values (weight embedded PVA film-weight pure PVA film) to estimate the amount of immobilized Al2O3 NPs in PVA. After using both methods and repeating each method three times, it was detected that the amount of embedded Al2O3 in the PVA film is 9.2 µg ± 0.051.

Adsorption Study
The batch sorption of Ni(II) ions onto a PVA-Al 2 O 3 nanocomposite adsorbent in aqueous solutions at ambient temperature was examined. For that, a conical flask containing 100 mL of Ni 2+ metal ion solution was filled with ultra-pure water and stirred to achieve an initial Ni solution concentration ranging from 10 to 100 mg/L before being put in a thermostatic shaker for absorption (200 rpm). The remaining Ni 2+ ion concentration was then measured using atomic absorption spectroscopy. The following formulae were used to investigate the effect of various parameters on the adsorption capacity of Ni 2+ [45,46].
where C o and C a are the concentrations of adsorbent material at the beginning of the adsorption process and at the equilibrium of the adsorption process, respectively. Figure 2 shows the FT-IR spectra of PVA, Al 2 O 3 nanoparticles, and Al 2 O 3 -PVA nanocomposite to identify their vibrational absorption motion, which is produced by FT-IR spectra. The FT-IR spectra of pure PVA exhibited a strong and wide stretching band at 3334 cm −1 and a bending vibration at 1565 cm −1 , 1428 cm −1 , and 1325 cm −1 that can be attributed to the hydroxyl group because of intramolecular and intermolecular hydrogen bonding. Furthermore, stretching vibrational absorption bands at 2945 cm −1 and 2908 cm −1 appeared as a result of functional groups of the CH and −CH 2 groups, respectively. Furthermore, the appearance of stretching vibration around 1100 cm −1 was related to the C-O functional group. These characteristics could be represented by the main functional groups of the PVA structure. In addition to the appearance of a vibrational stretching peak around 1739 cm −1 related to the C=O functional group, but with small intensity as it was related to the presence of leftover acetate groups after the hydrolysis of polyvinyl acetate to produce PVA [30,47,48]. In the case of the laser ablation of the Al sheet immersed in the ultra-pure water, the FT-IR spectra of Al 2 O 3 nanoparticles exhibited two distinctive vibrational peaks of Al 2 O 3 , at 558 cm −1 and 632 cm −1 , which are exhibited in the fingerprint region. Furthermore, the appearance of vibrational peaks characterized by a broad band stretching motion around 3342 cm −1 was related to the residual hydroxyl functional group (-OH) that was produced by atmospheric moisture. Moreover, there are no other peaks related to the residual organic compounds. In the case of Al 2 O 3 -PVA nanocomposite, the primary distinctive vibrational peaks of the PVA structure are still intact, but their strength and position have changed. The intensity of these hydroxyl group bands is clearly reduced, which is attributable to the interaction of the PVA structure with Al ions. Moreover, below 1000 cm −1 , there are two distinct peaks of Al 2 O 3 , at 558 cm −1 and 632 cm −1 , which are exhibited in the fingerprint area of the spectra as evidence for the incorporation of Al 2 O 3 molecules in the polymer matrix. Moreover, it was clear that the strong electronegativity of the atoms formed from Al 2 O 3 and injected into the polymeric matrix of PVA structure, which has a significant impact on the spectrum of adjacent group frequencies, may be responsible for the conformational changes in the width and intensity of the vibrational bands of PVA structure [20,41,49]. These significant fluctuations in the absorbance and frequencies of almost bands suggest that interactions between Al 2 O 3 NPs and the polymeric structure of PVA, such as hydrogen bonds or van der Waals interac-tions, are forming between the (OH − )/(COO − ) groups of PVA and the Al 2 O 3 NPs. This was accomplished by reducing the crystallinity degree of nanocomposites and forming charge transfer complexes in which the Al 2 O 3 NPs function as an electron acceptor and the PVA matrix works as an electron donor. These interactions alter the dynamics of the nanocomposite chain structure.

Investigation of the Prepared Al 2 O 3 -PVA Nanocomposite
Membranes 2022, 12, x FOR PEER REVIEW 6 of 17 bands suggest that interactions between Al2O3 NPs and the polymeric structure of PVA, such as hydrogen bonds or van der Waals interactions, are forming between the (OH − )/(COO − ) groups of PVA and the Al2O3 NPs. This was accomplished by reducing the crystallinity degree of nanocomposites and forming charge transfer complexes in which the Al2O3 NPs function as an electron acceptor and the PVA matrix works as an electron donor. These interactions alter the dynamics of the nanocomposite chain structure. FESEM was used to investigate the morphological changes in PVA caused by embedding with Al2O3 molecules as mentioned in Figure 3. The micrographs exhibit SEM of Al2O3 nanoparticles, PVA, and the hybrid with PVA-Al2O3 nanocomposite. The surface of the produced structure from the laser ablation of the Al sheet in the ultra-pure water showed a semi-spherical shape in the nanoscale form, while the SEM image of the PVA structure showed a uniform surface shape that reveals dispersed smooth microspores instead of uniform ones. Moreover, the surface of the polymer was significantly distorted during metal oxide contact, and the metal oxide particles were uniformly dispersed over the polymer surface compared to the pure PVA structure. As a result, the change in the surface of the PVA-Al2O3 nanocomposite reveals that the PVA surface was highly deformed, and the aluminum oxides were homogeneously distribution throughout the PVA surface. FESEM was used to investigate the morphological changes in PVA caused by embedding with Al 2 O 3 molecules as mentioned in Figure 3. The micrographs exhibit SEM of Al 2 O 3 nanoparticles, PVA, and the hybrid with PVA-Al 2 O 3 nanocomposite. The surface of the produced structure from the laser ablation of the Al sheet in the ultra-pure water showed a semi-spherical shape in the nanoscale form, while the SEM image of the PVA structure showed a uniform surface shape that reveals dispersed smooth microspores instead of uniform ones. Moreover, the surface of the polymer was significantly distorted during metal oxide contact, and the metal oxide particles were uniformly dispersed over the polymer surface compared to the pure PVA structure. As a result, the change in the surface of the PVA-Al 2 O 3 nanocomposite reveals that the PVA surface was highly deformed, and the aluminum oxides were homogeneously distribution throughout the PVA surface.  Furthermore, the elements on the surface of the PVA structure before and after embedding with Al2O3 NPs were examined using an EDX element analyzer. Figure 4 depicts the EDX spectra of a PVA-Al2O3 nanocomposite before and after Al2O3 NPs adsorption. This result verified the presence of a pure PVA structure as it was only comprised of the C and O elements, which represented the main constituted elements of the PVA structure. Moreover, the elemental analysis confirmed the formation of pure Al2O3 nanoparti- Furthermore, the elements on the surface of the PVA structure before and after embedding with Al 2 O 3 NPs were examined using an EDX element analyzer. Figure 4 depicts the EDX spectra of a PVA-Al 2 O 3 nanocomposite before and after Al 2 O 3 NPs adsorption. This result verified the presence of a pure PVA structure as it was only comprised of the C and O elements, which represented the main constituted elements of the PVA structure. Moreover, the elemental analysis confirmed the formation of pure Al 2 O 3 nanoparticles from the laser ablation process in the ultra-pure water as it was only comprised of the Al and O elements, which represented the main constituted elements of the Al 2 O 3 structure. However, in the case of embedding with Al 2 O 3 , a new element (Al) was injected with C and O. So, the PVA structure was embedded with the Al element. Moreover, the phase of Al could be detected to be metallic or oxide form based on looking at the ratio of O/C in PVA structure before and after ablation of Al, which was 0.797 and 1.42, respectively. So, the amount of O was increased owing to the occurrence of Al in the oxide form (Al 2 O 3 ). cles from the laser ablation process in the ultra-pure water as it was only comprised of the Al and O elements, which represented the main constituted elements of the Al2O3 structure. However, in the case of embedding with Al2O3, a new element (Al) was injected with C and O. So, the PVA structure was embedded with the Al element. Moreover, the phase of Al could be detected to be metallic or oxide form based on looking at the ratio of O/C in PVA structure before and after ablation of Al, which was 0.797 and 1.42, respectively. So, the amount of O was increased owing to the occurrence of Al in the oxide form (Al2O3). The XRD measurements were used to examine the crystallinity of the PVA structure with and without incorporated metal produced from the laser ablation of the Al sheet. Nanostructured materials were created by the PLAL method of an Al target immersed in  The XRD measurements were used to examine the crystallinity of the PVA structure with and without incorporated metal produced from the laser ablation of the Al sheet. Nanostructured materials were created by the PLAL method of an Al target immersed in different types of liquid media, and the resultant diffractogram spectra are given in respectively [50]. Furthermore, no other peaks were observed related to any foreign impurities in the PVA structure.
Membranes 2022, 12, x FOR PEER REVIEW 9 of 1 different types of liquid media, and the resultant diffractogram spectra are given in Fig  ure 5. In the case of pure PVA, there are two separate diffraction peaks at diffraction an gles 2θ = 19.5° and 40.5°, which correspond to the indices planes (1 0 1) and (1 1 1), re spectively [50]. Furthermore, no other peaks were observed related to any foreign impu rities in the PVA structure. In the case of the laser ablation of the Al sheet immersed in the ultra-pure water, th crystalline peaks appeared at 31.62°, 37.18°, 39.79°, 46.17°, 60.84°, and 67.13°, which cor respond to (2 2 0), (3 1 1), (2 2 2), (4 0 0), (4 2 2), and (4 4 0), respectively, based on JCPD XRD card number 79-1558 of the cubic structure of Al2O3. Moreover, no other typica peaks were seen in the diffractogram, which may be produced from the other contam nants during the preparation steps. This observation confirmed the high purity of th produced nanostructure materials. Moreover, the main crystalline peak used to deetec the crystallite size of Al2O3 nanostructure using the Debye-scherrer equation [51].
(2 where D, , , and θ are the crystallite size of Al2O3 nanostructure, used X-ray wave length, FWHM of the diffraction peak at 2θ = 67.13°, and the Bragg angle (33.57°), re spectively, its crystallite is 19.8 nm. In the case of laser ablation of Al sheet immersed i the PVA solution, the semi-crystalline structure was still present in the case of embed ding with the generated nanostructured materials formed from the PLAL process o Al-target immersed in PVA solution, but the intensity was reduced by a large amoun under the effect of the intermolecular hydrogen band produced between the PVA struc ture and nanostructured materials. Furthermore, the new crystalline peaks appeared a 31.62°, 37.18°, 39.79°, 46.17°, 60.84°, and 67.13°, which correspond to (2 2 0), (3 1 1), (2 2 2 (4 0 0), (4 2 2), and (4 4 0), respectively, based on JCPD XRD card number 79-1558 of th cubic structure of Al2O3 [52]. It was clear that the PVA diffraction peaks remained afte being incorporated with Al2O3 NPs in the creation of a nanocomposite structure. It wa Moreover, no other typical peaks were seen in the diffractogram, which may be produced from the other contaminants during the preparation steps. This observation confirmed the high purity of the produced nanostructure materials. Moreover, the main crystalline peak used to deetect the crystallite size of Al 2 O 3 nanostructure using the Debye-scherrer equation [51].
where D, λ, β, and θ are the crystallite size of Al 2 O 3 nanostructure, used X-ray wavelength, FWHM of the diffraction peak at 2θ = 67.13 • , and the Bragg angle (33.57 • ), respectively, its crystallite is 19.8 nm. In the case of laser ablation of Al sheet immersed in the PVA solution, the semi-crystalline structure was still present in the case of embedding with the generated nanostructured materials formed from the PLAL process of Al-target immersed in PVA solution, but the intensity was reduced by a large amount under the effect of the intermolecular hydrogen band produced between the PVA structure and nanostructured materials. Furthermore, the new crystalline peaks appeared at 31.  [52]. It was clear that the PVA diffraction peaks remained after being incorporated with Al 2 O 3 NPs in the creation of a nanocomposite structure. It was demonstrated that the Al 2 O 3 NPs incorporation had no effect on the distribution of the PVA's crystallinity, while its area under the curve has changed to a lower value, indicating that the crystallinity of the PVA structure has reduced. This reduction could be related to the presence of intermolecular hydrogen bonding that occurred between its chain structure and Al 2 O 3 NPs, leading to reducing the intermolecular interaction between the chains of PVA. Therefore, the electrostatic interaction of Al 2 O 3 NPs with the PVA chain leads to disturbing the crystalline phase of the PVA structure. So, this observation could be represented as a confirmation of successful incorporation.

Effect of pH
The pH of the solution is a critical variable in the adsorption process because it influences metal sorption via protonation and deprotonation of the adsorbent's functional groups, the Ni speciation, adsorbent surface charge, and adsorbent ionization. As a result, the influence of pH on nickel sorption is explored in the pH range 2-7 for an initial concentration of 100 mg L −1 from Ni(II), an adsorbent dose of 0.5 g/L, and a temperature of study at 303 K as depicted in Figure 6a. This graph clearly shows that the adsorption capacity rises with a rising pH value, and the precipitation occurs in nickel solutions when the pH exceeds 7. So, the trials are not undertaken above a pH of 7. Furthermore, around pH 5.3, nickel adsorption capacity reaches a maximum of 62 mg g −1 and thereafter decreases with increasing pH levels [53][54][55][56]. This was related to: 1.
At pH values higher than 6, the excess of alkaline -OH group has a greater tendency to combine with Ni 2+ and form Ni(OH) 2 participated, causing the adsorption to be diminished.

2.
At pH values in the range 5-6, the surface charge of the hybrid nanocomposite turned to a negative charge due to the medium having a low acidic concentration, increasing the coordination between positively charged metal ions (Ni 2+ ) and Al 2 O 3 -PVA nanocomposite by electrostatic attraction, leading to reach the maximum adsorption capacity. The results were consistent with Ni 2+ adsorption on Al 2 O 3 -PVA nanocomposite as mentioned in the previous work [57].

3.
At pH values lower than 5, the decrease in nickel adsorption capability at lower pH levels is related to protonation of the Al 2 O 3 -PVA nanocomposite by the acidic medium and the water molecules converted from H 2 O to H 3 O + , leading to a decrease in the number of charge carriers in the hybrid membrane for metal adsorption. In addition, competition for adsorption sites on the PVA structure created between H + and Al 2+ make an electrostatic repulsion between them [58-61].

Effect of Initial Pollutant Concentration
The influence of initial Ni 2+ concentrations on nanocomposite adsorption was examined from 0 mgL −1 to 500 mgL −1 of beginning Ni(II) concentration at a temperature of study at 303 K, pH 5.3, and an adsorbent dose of 0.5 g/L, and the findings are presented in Figure 6b. It was shown that the initial Ni 2+ concentration in aqueous solution increased till it reached saturation and then decreased. So, the precision description of this process can be described as the percentage amount of Ni(II) removal greatly reduced as the beginning Ni(II) ion concentration content rises. This observation could be discussed when the initial Ni(II) ion concentration increased from 0 to 200 mg/L, the mass transfer of Ni(II) ions between the aqueous solution and the Al 2 O 3 nanoparticles were supported, leading to improved interaction between Ni(II) ions and the Al 2 O 3 nanoparticles and increasing the adsorption uptake of Ni(II). In other words, when the initial Ni(II) ion concentration was further increased from 200 to 500 mg/L, the adsorption capacity hit a plateau due to the strong binding sites on the Al 2 O 3 /PVA nanocomposites have been filled with the initial amounts of Ni(II) ions, which appeared from the adsorption isotherm analysis as the Langmuir and Freundlich models, which were compatible with the other scholars who had observed similar findings. So, from this study, the optimum beginning Ni(II) ion concentration for a good adsorption process was chosen before the plateau shape, at 100 mg/L as this value represented the highest rate of adsorption capacity and after this value, the rate of adsorption capacity started to be decreased [62][63][64].

Effect of Initial Pollutant Concentration
The influence of initial Ni 2+ concentrations on nanocomposite adsorption was examined from 0 mgL −1 to 500 mgL −1 of beginning Ni(II) concentration at a temperature of study at 303 K, pH 5.3, and an adsorbent dose of 0.5 g/L, and the findings are presented in Figure 6b. It was shown that the initial Ni 2+ concentration in aqueous solution increased till it reached saturation and then decreased. So, the precision description of this process can be described as the percentage amount of Ni(II) removal greatly reduced as the beginning Ni(II) ion concentration content rises. This observation could be discussed when the initial Ni(II) ion concentration increased from 0 to 200 mg/L, the mass transfer of Ni(II) ions between the aqueous solution and the Al2O3 nanoparticles were supported, leading to improved interaction between Ni(II) ions and the Al2O3 nanoparticles and increasing the adsorption uptake of Ni(II). In other words, when the initial Ni(II) ion concentration was further increased from 200 to 500 mg/L, the adsorption capacity hit a plateau due to the strong binding sites on the Al2O3/PVA nanocomposites have been filled with the initial amounts of Ni(II) ions, which appeared from the adsorption isotherm analysis as the Langmuir and Freundlich models, which were compatible with the other scholars who had observed similar findings. So, from this study, the optimum beginning Ni(II) ion concentration for a good adsorption process was chosen before the plateau shape, at 100 mg/L as this value represented the highest rate of adsorption capacity and after this value, the rate of adsorption capacity started to be decreased [62][63][64].  Figure 6c depicts the influence of reaction temperature on the removal of Ni 2+ ions for 100 mg L −1 beginning Ni(II) ion concentration, an adsorbent dose of 0.5 g/L, and pH of 5.3 for nickel solutions at varying temperatures from 298 K to 328 K. As the temperature rose from 298 to 328 K, the adsorption capacity of nickel ions grew from 65.8 mg g −1 to 87.4 mg g −1 . These findings revealed that nickel ion sorption onto the Al 2 O 3 /PVA nanocomposite adsorbent was endothermic.

Mechanism of Adsorption Process
The adsorption of metal ions of Ni 2+ by the nanocomposite could be controlled in three ways. The first predicted mechanism was the nanocomposite adsorbent's quick transfer to the external surface absorption of metal ions. The second predicted mechanism was the diffusion of metal ions via the pores of the nanocomposite. The third predicted mechanism might be linked to chemical adsorption between nanocomposite functional groups, such as hydroxyl groups, and metal ions. The experimental results were analyzed using pseudo-first-order or pseudo-second-order kinetic models to study the kinetic parameters of the adsorption of metal ions via the Al 2 O 3 /PVA nanocomposite [30,[66][67][68]. q t = q e 1 − e −k 1 t Pseudo-first-order (3) q t = k 2 q e 2 t /(1 + q e k 2 t) Pseudo-second-order (4) where q t is the amount of adsorbed metal after t time, q e is the amount of adsorbed metal after equilibrium time, k 1 is the constant of pseudo-first-order, and k 2 is the constant of pseudo-second-order. From Figure 7, the intercept, slope, and the correlation coefficient of Pseudo-first-order are 4.95347 ± 0.03878, −0.3606 ± 0.00983, and 0.98969, respectively, while the intercept, slope, and the correlation coefficient of Pseudo-second-order are 0.15013 ± 0.00719, 0.01219 ± 8.87805 × 10 −5 , and 0.99926, respectively. So, the value of k 1 and k 2 are 0.3606 and 9.9 × 10 −4 gmg −1 min −1 , respectively. Therefore, in the case of the pseudo second-order, the predicted equilibrium adsorption capacity was more compatible with its experimental value.

Conclusions
A novel hybrid PVA/Al2O3 nanocomposite was created in this study using a simple green potential approach. This approach used a pulsed laser ablation method to create a hybrid nanocomposite from an Al sheet immersed in PVA solution. The successful em-

Conclusions
A novel hybrid PVA/Al 2 O 3 nanocomposite was created in this study using a simple green potential approach. This approach used a pulsed laser ablation method to create a hybrid nanocomposite from an Al sheet immersed in PVA solution. The successful embedding of PVA structure with Al 2 O 3 nanoparticles was demonstrated by FTIR, XRD, and SEM-EDAX investigation of PVA before and after contact with Al 2 O 3 nanoparticles. It can be utilized as a cost-effective alternative to activated carbons, membrane filtration, and ion-exchange adsorbents. The adsorbent effectively removes Ni(II) from aqueous solutions, with even greater removal achieved at low concentrations of about 100 mg/L. The adsorption was shown to be pH-dependent, with pH 5.3 yielding the most clearance. The pseudo-second-order rate kinetics was used to manage the removal process. The adsorption findings revealed that hybrid PVA/Al 2 O 3 nanocomposite may be utilized to efficiently remove Ni(II) from aqueous solutions.