Zn2+-imprinted porous polymer beads: Synthesis,structure, and selective adsorption behavior for template ion

Zn²⁺-imprinted polymer was synthesized in porous spherical forms via a self-assembled complex between 2,2′-bipyridyl/4-vinylpyridine complexant/functional monomer and Zn²⁺ template ion. Diameters of particles ranged from 250 to 550 μm to enlarge the surface area and thus enhance the adsorption capacity. The presence/absence of the template ion in the preparation of the imprinted polymer was confirmed by EDX spectroscopy, and the physical structure of the particles was investigated using ESEM and BET analysis. The particle and the pore size were controlled by the cross-linker/monomer feed ratio. The adsorption capacity of the imprinted polymers was 210.61 μmol g^?1 for Zn²⁺, while those for Cu²⁺, Ni²⁺, and Pb²⁺, were 37.92 μmol g^?1, 33.02 μmol g^?1, and 9.70 μmol g^?1, respectively. This big discrepancy of the adsorption capacities illustrates the excellent separation selectivity of the imprinted polymers. The adsorption capacity decreased significantly at pH below 4.5, as the polymers are easily protonated. The imprinted particles lost only 10 % of their adsorption ability after 10 repeated uses.     

A chemiluminescence sensor for determination of epinephrine using graphene oxide–magnetite-molecularly imprinted polymers

A chemiluminescence (CL) sensor for the determination of epinephrine using the system of luminol–NaOH–H₂O₂ based on a graphene oxide–magnetite-molecularly imprinted polymer (GM-MIP) is described. The epinephrine GM-MIP was synthesized using graphene oxide (G) which improved the adsorption capacity, and magnetite nanoparticles which made the polymers easier to use in the sensor. The adsorption performance and properties were characterized. The GM-MIP was used in CL analysis to increase the selectivity and the possible mechanism was also discussed. The CL sensor responded linearly to the concentration of epinephrine over the range 1.04 × 10^?7–7.06 × 10^?3 mol/L with a detection limit of 1.09 × 10^?9 mol/L (3σ). The relative standard deviation for determination was 3.87%. On the basis of speediness and sensitivity, the sensor is reusable and shows a great improvement in selectivity and adsorption capacity over other sensors. The sensor had been used for the determination of epinephrine in drug samples.     

Adsorption of heavy metals on amine-functionalized SBA-15 prepared by co-condensation: Applications to real water samples

SBA-15 functionalized with 3-aminopropyltrimethoxy-silane was studied as potential absorbent for Cd²⁺, Co²⁺, Cu²⁺, Zn²⁺, Pb²⁺, Ni²⁺, Al³⁺ and Cr³⁺. The adsorption capacity and selectivity of the materials were investigated in single and multi-metal solutions. Using single-metal solutions, the adsorbent was found to have an affinity (molar basis) for metal ions in decreasing order of Al³⁺ > Cu²⁺ > Ni²⁺ > Zn²⁺ > Co²⁺ > Cd²⁺ > Pb²⁺ > Cr³⁺. Using very dilute solutions, i.e., 10 ppm, more than 95% of cations were removed, except Co²⁺ and Cr³⁺, indicating the high sensitivity of the current adsorbent. The affinity for coexisting metal cations decreased in the order of Al³⁺ > Ni²⁺ > Cr³⁺ > Pb²⁺ > Zn²⁺ > Cd²⁺ > Co²⁺ > Cu²⁺. The adsorption capacities in multi-metal solutions were lower than in single-metal ones because of competition between metallic elements for the amine groups, with a preference for Al³⁺. The amine-modified SBA-15 adsorbent exhibited an excellent selectivity against sodium, potassium, and calcium, indicating that the ionic strength does not affect the adsorption properties. Application of this material to remove copper in tap water, river water, and electroplating wastewater was shown to be successful.     

Cadmium ion-selective sorbent preconcentration method using ion imprinted poly(ethylene glycol dimethacrylate-co-vinylimidazole)

The present study focuses on the preparation of an Cd²⁺-imprinted poly(ethylene glycol dimethacrylate-co-vinylimidazole) for selective extraction/preconcentration of Cd²⁺ ions from aqueous solution, with further determination by FAAS using a flow system. Sorbent extraction/preconcentration system was optimized by using chemometric tools (factorial design and Doehlert matrix). Under optimized conditions, the method presented a limit of detection of 0.11 μg L^?1 and linear analytical curve from 1.0 up to 50.0 μg L^?1 (r = 0.993). The preconcentration factor (PF), consumptive index (CI) and concentration efficiency (CE) were found to be 38.4, 0.39 mL and 14.3 min^?1, respectively. The selectivity coefficient of ion imprinted polymer was compared with the selectivity coefficient of NIP (non-imprinted polymer) for the Cd²⁺/Pb²⁺, Cd²⁺/Cu²⁺ and Cd²⁺/Zn²⁺ binary mixtures, where the respective values of relative selectivity coefficient (k′) of 157.5, 4.44 and 1.38 were obtained. The proposed method was successfully applied for cadmium determination in different types of water samples, urine and certified reference material (Lobster Hepatopancreas).     

The adsorptive extraction of oxidized sulfur-containing compounds from fuels by using molecularly imprinted chitosan materials

An innovative approach for desulfurisation of fuels is proposed. It relies on the formation of recognition sites, complementary to oxidized sulfur-containing compounds, on cross-linked chitosan microspheres and electrospun chitosan nanofibers using the molecularly imprinted polymer technique. Benzothiophene sulfone (BTO₂), dibenzothiophene sulfone (DBTO₂) and 4,6-dimethyldibenzothiophene sulfone (4,6-DMDBTO₂) were used as templates for the preparation of molecularly imprinted polymers (MIPs). The possible molecular interactions between imprinted chitosan adsorbent and oxidized sulfur-containing compounds were investigated by molecular modeling using density functional theory (DFT) and results indicated that interactions took place via hydrogen bonding. The molecularly imprinted polymer adsorbents (cross-linked microspheres and electrospun nanofibers) gave better selectivity for the target sulfonated compounds and the adsorption isothermal studies followed the Freundlich model. Maximum adsorption capacities of 8.5 ± 0.6 mg/g, 7.0 ± 0.5 mg/g and 6.6 ± 0.7 mg/g were observed for model BTO₂, DBTO₂ and 4,6-DMDBTO₂ respectively at 1 mL/h when imprinted nanofibers were employed, and the imprinted microspheres gave maximum adsorption capacity of 4.9 ± 0.5 mg/g, 4.2 ± 0.7 mg/g and 3.9 ± 0.6 mg/g for BTO₂, DBTO₂ and 4,6-DMDBTO₂ respectively. Application of the nanofibers to oxidized hydro-treated fuel under continuous flow adsorption system at 1 mL/h indicated that 84% of sulfur was adsorbed, with adsorption capacity of 2.2 ± 0.2 mg/g.     

Synthesis of NIPAAm-based polymer-grafted silica beads by surface-initiated ATRP using Me4Cyclam ligands and the thermo-responsive behaviors for lanthanide(III) ions

The applicability of atom transfer radical polymerization (ATRP) to the copolymerization of N-isopropylacrylamide (NIPAAm) with N-vinyl-2-pyrrolidone (NVP) was examined in CuCl/CuCl₂-catalyst system using tris[2-(dimethylamino)ethyl]amine (Me₆TREN) and 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane (Me₄Cyclam) as ligands. In the Me₆TREN system, less reactive NVP not only does not quantitatively copolymerize but also interferes with homopolymerization of NIPAAm units. In contrast, the Me₄Cyclam system under heating was more active, although the controllability for polymer homogeneity is lower than Me₆TREN system. The application of active Me₄Cyclam system to surface-initiated ATRP has successfully prepared silica beads surface-modified with NIPAAm copolymers of NVP and 4-vinylpyridine (VPy). The thermo-responsive behavior of surface-grafted NIPAAm-based polymers was investigated for lanthanide trivalent ions (Ln(III)) in different pH solutions. In the weak acidic solutions of pH = 5.4–5.6, all the surface-grafted polymers including poly(NIPAAm) exhibited only adsorption behavior with regular selectivity (Eu³⁺ > Sm³⁺ > Nd³⁺ > Ce³⁺ > La³⁺) below the phase-transition temperatures. In the more acidic solution of pH = 2.9, the surface-grafted poly(NIPAAm) and NVP copolymers exhibited adsorption and desorption behaviors below and above the phase-transition temperatures, while VPy copolymers exhibited only adsorption independent of temperature change. Furthermore, the adsorption capacity of all the surface-grafted polymers was deteriorated by the lowering of pH. The observed desorption and the deterioration of adsorption capacity suggest the weakening of adsorption strength for Ln(III) in low pH solutions. In this study, a possible adsorption/desorption mechanism of Ln(III) on surface-grafted NIPAAm-based polymers is discussed.     

Preparation and characterization of magnetic chelating resin based on chitosan for adsorption of Cu(II), Co(II), and Ni(II) ions

Cross-linked magnetic chitosan–diacetylmonoxime Schiff’s base resin (CSMO) was prepared for adsorption of metal ions. CSMO obtained was investigated by means of scanning electron microscope (SEM), FTIR, ¹H NMR, wide-angle X-ray diffraction (WAXRD), magnetic properties and thermogravimetric analysis (TGA). The adsorption properties of cross-linked magnetic CSMO resin toward Cu²⁺, Co²⁺ and Ni²⁺ ions were evaluated. Various factors affecting the uptake behavior such as contact time, temperature, pH and initial concentration of the metal ions were investigated. The kinetics was evaluated utilizing the pseudo-first-order and pseudo-second-order. The equilibrium data were analyzed using the Langmuir, Freundlich, and Tempkin isotherm models. The adsorption kinetics followed the mechanism of the pseudo-second-order equation for all systems studied, evidencing chemical sorption as the rate-limiting step of adsorption mechanism and not involving a mass transfer in solution. The best interpretation for the equilibrium data was given by Langmuir isotherm, and the maximum adsorption capacities were 95 ± 4, 60 ± 1.5, and 47 ± 1.5 mg/g for Cu²⁺, Co²⁺ and Ni²⁺ ions, respectively. Cross-linked magnetic CSMO displayed higher adsorption capacity for Cu²⁺ in all pH ranges studied. The adsorption capacity of the metal ions decreased with increasing temperature. The metal ion-loaded cross-linked magnetic CSMO were regenerated with an efficiency of greater than 84% using 0.01–0.1 M ethylendiamine tetraacetic acid (EDTA).     

Synthesis of Copper and Lead Ion Imprinted Polymer Submicron Spheres to Remove Cu2+ and Pb2+

In this paper, Methacrylic acid (MAA) and 4-vinyl pyridine (4-VP) as functional monomers, Ethylene glycol two methyl acrylate (EGDMA) as crosslinking agent, isopropyl alcohol as the solvent, prepared the Cu(II)- and Pb(II)- imprinted polymers (IIPs) submicron spheres by precipitation polymerization. The presence/absence of the template ion in the preparation of the imprinted polymer was confirmed by EDX spectroscopy, and the structure of the particles was investigated using IR, SEM and BET analysis. From different components of crosslinker/monomer (C/M) ratio analysis, C/M at 1:3 was the optimal ratio for preparing IIPs. Atomic absorption spectroscopy (AAS) was characterized the imprinted polymers absorption behavior. The results show that the maximum adsorption capacity of Cu²⁺ and Pb²⁺ -imprinted polymer were 26.9 mg g^?1 and 25.3 mg g^?1, respectively. They also have good adsorption capacity and superior selectivity property for Cu²⁺ and Pb²⁺ in water, respectively. The selectivity factors (α) for Ni²⁺, Zn²⁺, Co²⁺ and Fe²⁺ were 16.5 (Cu²⁺) and 12.1 (Pb²⁺), 13.8 (Cu²⁺) and 16.2 (Pb²⁺), 10.8 (Cu²⁺) and 10.1 (Pb²⁺), 20.4 (Cu²⁺) and 20.7 (Pb²⁺), respectively. The regeneration experiment result demonstrates an excellent re-utilization property of these two type IIPs, after ten uses, the adsorption capacity can maintain above 60%.

     

Molecularly imprinted hydrogels for fibrinogen recognition

Molecularly imprinted hydrogels (MIHs) composed of N-isopropylacrylamide (NIPA) and maleic acid (MA) monomers and fibrinogen (Fbg, MW: 340 kDa, pI: 5.8) imprinted molecule were fabricated in pH buffer solutions (pH_prep: 4.0, 5.8 and 8.0). The non-imprinted hydrogels were also prepared in the same conditions without Fbg imprinted molecule. The adsorption equilibrium constant and the maximum adsorption capacity of the MIH prepared in pH 4.0 were evaluated to 9.61 mL mg^?1 and 38.99 mg protein g^?1 dry gel in pH 4.0 buffer solution, respectively. The selectivity tests were also performed by using two reference molecules as bovine serum albumin (BSA, MW: 67 kDa, pI: 4.78) and urease (MW: 480 kDa, pI: 5.99). The MIHs have 2.37–4.23 times higher selectivity for the Fbg imprinted molecule than the non-imprinted hydrogels prepared in the same conditions. Easy preparation of the MIHs, their high stability and ability to recognize small and large proteins, as well as to discriminate molecules with small variations in charge, make this approach attractive and broadly applicable in biotechnology, assays and sensors.     

Recognition of dimethoate carried by bi-layer electrodeposition of silver nanoparticles and imprinted poly-o-phenylenediamine

Thin film of a molecular imprinted polymer based on electropolymerization method with sensitive and selective binding sites for dimethoate was developed. This film was cast on gold electrode by electrochemical polymerization in solution of o-phenylenediamine and template dimethoate via cyclic voltammetry scans and further deposition of Ag nanoparticles. The surface plasmon resonance and cyclic voltammetric signals were also recorded simultaneously during the electropolymerization, controlling the thickness of the polymer film to be 25 nm. The imprinted film showed high selectivity towards to dimethoate. The recognition between the imprinted sensor and target molecule was observed by measuring the variation amperometric response of the oxidation–reduction probe, K₃Fe(CN)₆, on electrode. Under the optimal experimental conditions, the peak currents were proportional to the concentrations of dimethoate in two ranges, from 1.0 to 1000 ng mL^?1 and from 1.0 to 50 μg mL^?1, with the detection limit of 0.5 ng mL^?1. Due to the high affinity, selectivity and stability the imprinted sensor provides a simple detection platform for organophosphate compounds.     

Electrochromic performance and ion sensitivity of a terthienyl based fluorescent polymer

A novel terthienyl based fluorescent polymer bearing strong electron-withdrawing substituents directly attached to the 3,4-positions of the central thiophene ring was synthesized by electrochemical polymerization of diethyl 2,5-di(3,4-ethylenedioxythiophen-2-yl)thiophene-3,4-dicarboxylate. The corresponding polymer was characterized by cyclic voltammetry, FT-IR and UV–vis spectroscopy. The polymer has a well-defined redox process (E_p,1/2 = 0.74 V) and demonstrates a reversible electrochromic behavior; lilac in the neutral state and transparent sky blue in the oxidized state. Also, the polymer had low band gap (E_g = 1.82 eV) and high redox stability (retaining 94.0% of its electro-activity after 500th switch). Moreover, the sensitivity of both the monomer and its polymer towards metal cations was investigated by monitoring the change in the fluorescence intensity. Among various common ions both the monomer and its polymer were found to be selective towards Cu²⁺ and Cu⁺ ions by quenching the fluorescence efficiency with a Stern–Volmer constant (K_sv) of (1.4–1.6 × 10³ M^?1) and (1.5–1.8 × 10² M^?1) for monomer and polymer solutions, respectively.     

Fabrication of copper coated polymer foam and their application for hexavalent chromium removal

The polymer foam coated with zero-valent copper (Cu⁰) was designed and prepared for the removal of hexavalent chromium (Cr(VI)) in water. Firstly, porous poly(tert-butyl acrylate) was fabricated by concentrated emulsion polymerization and then acrylic acid groups were generated on the surface of foam by hydrolysis reaction. Secondly, with the help of the large amount reactive carboxylic acid groups, polyethyleneimine (PEI) were chemically grafted onto the surface by the reaction between amine group and acrylic acid group. Finally, zero-valent copper was reduced by sodium borohydride (NaBH₄) and coated on the surface of polymer foam. Thus the copper functionalized porous adsorbent (Cu⁰–PEI–PAA) was constructed, and then applied for removing Cr(VI) from aqueous solution. The removal mechanism of Cr(VI) involved redox reaction by zero-valent copper and adsorption by amine groups, simultaneously. As a result, 99.5% of Cr(VI) could be removed within 2 h, and the maximum removal capacity for Cr(VI) of Cu⁰–PEI(1800)–PAA was 9.16 mg/g. Furthermore, the effect of initial concentration of Cr(VI), pH value, and temperature on the Cr(VI) removal was investigated. Therefore, the as-prepared zero-valent copper-loaded polymer foam could be an efficient and promising remediation material to remove Cr(VI) from wastewater.     

Selectively removal of Al(III) from Pr(III) and Nd(III) rare earth solution using surface imprinted polymer

Rare earth is a very important strategic resource. But, impurities, such as Al³⁺, have great influence on the properties of rare earth material. In this paper, an Al³⁺-ionic imprinted polyamine functionalized silica gel sorbent was prepared by a surface imprinting technique for selectively adsorbing Al³⁺ from rare earth solution. The adsorption and recognition properties of IIP-PEI/SiO₂ for Al³⁺ were studied in detail. The experimental results showed that IIP-PEI/SiO₂ possessed strong adsorption affinity, specific recognition ability, and excellent selectivity for Al³⁺. The adsorption isotherm data greatly obey the Langmuir model, and the adsorption was typical monolayer. The adsorption capacity could reach to 1.98 mmol g^?1, and relative selectivity coefficients relative to Pr³⁺ and Nd³⁺ are 23.47 and 22.85, respectively. Besides, IIP-PEI/SiO₂ was regenerated easily using diluted hydrochloric acid solution as eluent and IIP-PEI/SiO₂ possesses better reusability.     

An emerging approach for the targeting analysis of dimethoate in olive oil: The role of molecularly imprinted polymers based on photo-iniferter induced “living” radical polymerization

This study concerns the first attempt to prepare molecularly imprinted polymers for the selective recognition of dimethoate using an iniferter polymerization technique (Inif-MIP). The synthesized polymers were fully characterized. SEM micrographs show a large accessibility to the binding sites with a significant improvement in MIP morphology. Inif-MIPs displayed high adsorption capacity (Q = 5.3 mg g⁻¹). The selectivity of this imprinting system was also assessed by means of cross-selectivity assays and the results obtained show that Inif-MIP displays a high selectivity for dimethoate, whereas some structural analogues (omethoate, malathion and methidathion) are poorly retained (6.3–28.7%) or not retained at all (fenthion). Inif-MISPE methodology was implemented by packing Inif-MIPs particles into a Solid Phase Extraction (SPE) cartridge and the loading, washing and eluting steps were optimized. The suitability of this sample preparation technique was demonstrated, as concentrations of dimethoate close to the tolerated maximum residue limits in the olive oil samples could be satisfactorily analyzed with good precision and accuracy. Some remarkable characteristics, like the sorbent reusability (at least 20 cycles without the lost of selectivity), low solvent consumption, reduced sample handling and, moreover higher recovery rates reaching 88% could be ascribed to the Inif-MISPE methodology.     

Effective Cd2+ chelating fiber based on polyacrylonitrile

A reusable chelating fiber containing polyamino–polycarboxylic acid ligands was prepared via the stepwise modification of polyacrylonitrile fiber with diethylenetriamine and chloroacetic acid. The amination and carboxylmethylation conditions were optimized, and the modified fiber was characterized by elemental analysis, XRD, SEM and FTIR. For Cd²⁺ in water, this chelating fiber has prominent adsorption abilities such as low adsorption limitation (0.001 mg/L), high adsorption capacity (1.34 mmol/g) and fast response speed (half-saturation adsorption time less than 0.5 min based on 1 mg/mL Cd²⁺). The effectiveness of this chelating fiber has been proved by using it to treat actual sewage water, where the concentration of Cd²⁺ was reduced from 0.540 to below 0.001 mg/L. This level easily meets drinking water standards (0.003 mg/L) issued by the World Health Organization. Moreover, this chelating fiber is also very effective at treating other metal ions such as Cu²⁺, Ca²⁺, Zn²⁺, Mg²⁺, Pb²⁺, Ni²⁺, Ag⁺ and Hg²⁺.     

Comparison of the influence of nanomaterials on response properties of copper selective electrodes

Novel Cu²⁺ ion selective electrode in carbon paste matrices based on incorporation of bis(2-hydroxynaphthaldehydene)-1,6-hexanediamine (BHNHDA) has been developed. The influence of variables including sodium tetraphenylborate (NaTPB), ionophore, and amount of multiwalled carbon nanotubes (MWCNT) and Nujol and effect of two new nanoparticles including gold nanoparticles loaded on activated carbon (Au-NP-AC) and zinc sulfide nanoparticles loaded on activated carbon (ZnS-NP-AC) on the electrodes response was studied and optimized. At optimum specified conditions, the proposed electrodes have appropriate advantages such as short response times and suitable reproducibility and applicability for a period of at least 1 month without any significant divergence in slope and response properties. The sensor based on impregnations of MWCNT, Au-NP-AC and ZnS-NP-AC have wide linear range of concentration (6 × 10^?8–1.0 × 10^?1 mol L^?1) and detection limit of lower than 4 × 10^?8 mol L^?1 of Cu²⁺ ion. The electrodes based on incorporation of Au-NP-AC and ZnS-NP-AC have Nernstian response with slope of 29.34 ± 1.41 and 29.78 ± 1.23 mV decade^?1 and response is independent of pH in the range of 2.0–5.0. Finally, these electrodes have been successfully applied for the determination of Cu²⁺ ions content in various real samples. Due to their acceptable selectivity coefficient, they are usable for accurate and successful evaluation of Cu²⁺ ions content in various real sample with complicated matrices.     

Preparation and characterization of fluorescent hyperbranched polyether

A new kind of fluorescent hyperbranched polymers was prepared by an end-capping approach, i.e., the hyperbranched poly(hydroxyl ether) was end capped with p-N,N-dimethylaminobenzaldehyde. The resulting polymers fluoresce yellow-green in solid and in solution. The maximum excitation and emission wavelengths in ethanol are 310 ± 10 and 360 ± 10 nm, respectively. Hyperbranched polyethers with various densities of chromophore groups showed different fluorescence intensities at the same concentration of chromophore groups. The fluorescent hyperbranched polyether with a high density of chromophore groups can form intramolecular excimers. The fluorescence signal of the resulting polymer increases with pH and passes through a maximum at 7.2–8.5 and then decreases gradually. Furthermore, the peak at 360 nm shifts to 405 nm with increasing pH. The fluorescence can be quenched by transition metal cations such as Cu²⁺ and Fe³⁺, while the alkali and alkaline earth metal cations and Ni²⁺ and Co²⁺ have little effect on the fluorescence intensity.     

Synthesis and characterization of magnetic polyHIPEs with humic acid surface modified magnetic iron oxide nanoparticles

Magnetic macroporous polymer monoliths have been prepared using styrene/divinylbenzene (S/DVB) high internal phase emulsions (HIPEs) as templates. Humic acid surface modified iron oxide magnetic nanoparticles (Fe₃O₄@HA) have been used to prepare magnetic emulsion templates. The effect of magnetic particle concentration has been investigated by changing the ratio of Fe₃O₄@HA nanoparticles in the continuous phase. Highly macroporous polymers with magnetic response were obtained by the removal of the internal phase after the curing of emulsions at 80 °C. Fe₃O₄@HA particles were characterized by XRD and FTIR. The porosity, pore morphology and magnetic properties of the macroporous polymers were characterized as a function of the Fe₃O₄@HA concentration by scanning electron microscopy (SEM), Brunauer–Emmet–Teller (BET) molecular adsorption method and vibrating sample magnetometry (VSM), respectively. BET and VSM measurements demonstrated that the specific surface area and the saturation magnetization of the polymer monoliths were changed according to the Fe₃O₄@HA concentration between 8.77–35.08 m² g^?1 and 0.63–11.79 emu g^?1, respectively. Resulting magnetic monoliths were tested on the adsorption of Hg(II) and atomic absorption spectroscopy (AAS) was used to calculate the adsorption capacities. The maximum adsorption capacity of the magnetic monoliths was calculated to be 20.44 mmol g^?1 at pH 4.     

Adsorption and equilibrium adsorption modeling of bivalent metal cations on viscose rayon succinate at different pHs

A viscose rayon succinate (VRS) was studied as a chelating fiber for the removal of metal ions from an aqueous solution. VRS was synthesized successfully from viscose rayon (VR) and succinic anhydride in the presence of dimethylsulfoxide (DMSO), and was characterized by C¹³ nuclear magnetic resonance ¹³C NMR, scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) analysis. The maximum bivalent metal ion adsorption capacity of the VRS was 6.2 meq/g. Studies on the adsorption behaviour of VRS and its ability to remove bivalent trace metals such as Cu²⁺, Zn²⁺, Pb²⁺, and Ni²⁺ from an aqueous solution were performed both by FT-IR and quantitative analyses at different pHs. The results showed that the adsorption of metals on VRS increased as pH increased, and furthermore, that the adsorption capacity of metal ions could be classified as Cu²⁺ > Zn²⁺ > Ni²⁺ > Pb²⁺. The adsorption modeling for the interpretation of empirical data was carried out by assuming a probability factor, P(A), and a degree of protonation, χ. Surface potential, Ψ₀, and an effective ratio of surface equilibrium constants, K_effect, were obtained using the model.