Gamma radiation-induced synthesis of a high-performance alginate/poly(acrylic acid-vinyl sulfonic acid) adsorbent for Cu(II) and Zn(II) ions
This study reports the synthesis and characterization of an alginate-poly(acrylic acid-co-vinyl sulfonic acid) (Alg-P(AA-co-VSA)) graft copolymer as an adsorbent for the removal of Cu(II) and Zn(II) ions from aqueous solutions. The graft copolymer was synthesized via γ-radiation-induced graft polymerization and characterized using FTIR, XRD, XPS, zeta potential, TGA, and SEM techniques. Batch adsorption studies revealed that adsorption is highly pH-dependent, with optimal pH values of 5.0 for Cu(II) and 6.0 for Zn(II). The maximum adsorption capacities were 65.78 mg/g for Cu(II) and 60.97 mg/g for Zn(II). The adsorption mechanism is complex, likely involving multiple interactions, with contributions from both heterogeneous multilayer adsorption (Freundlich model) and monolayer adsorption (Langmuir model). Adsorption kinetics were well-described by the pseudo-second-order model. Thermodynamic analysis showed a spontaneous and exothermic adsorption process, with negative ΔH, ΔG, and ΔS values. A full factorial design was applied to optimize six key variables: pH, time, temperature, initial metal concentration, adsorbent dose, and agitation speed, leading to a maximum removal efficiency of >99% for Zn(II) and Cu(II) under optimal conditions. These results demonstrate the potential of Alg-P(AA-co-VSA) graft copolymer as a highly efficient adsorbent for both heavy metal removal, offering significant benefits for environmental and industrial applications.
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