One-pot synthesis of sodium alginate-grafted-terpolymer hydrogel for As (III) and V(V) removal: In situ anchored comonomer and DFT studies on structures

In this work, an optimum sodium alginate (NaAlg)-grafted-[sodium 2-methylenesuccinate-co-sodium 2-((2(isobutyryloxy)ethoxy)methyl)succinate-co-ethylene glycol methacrylate, i.e., SMS-co-SIBEMS-co-EGMA, i.e., P1], i.e., P2, was selected among twelve hydrogels synthesized by employing variable amounts of synthesis parameters through a facile polymerization of SMS and EGMA monomers. In P1 and P2, SIBEMS third comonomer was strategically anchored in situ. The formation of terpolymer, i.e., P1, rather than generally expected copolymer, i.e., SMS-co-EGMA/ CoP1, was explored via closeness of experimental and simulated excitation energies of P1 and CoP1, measured by using density functional theory (DFT). The grafting of NaAlg into synthetic P1 elevated swelling, crosslink density (CD), network stability, reusability, and adsorption capacity (AC) of semisynthetic hydrogel, i.e., P2. The reusable P2 presenting optimum result among swelling, CD, and mean molar mass was chosen selectively for removals of As(III) and V(V). The structures of P1, P2, and adsorbed P2, i. e., As(III)-P2 and V(V)-P2; NaAlg-grafting; in situ anchored SIBEMS comonomer; reusability; thermostability; and surface properties were explored through XPS-NMR-FTIR-UV-vis, DFT, TG, DLS, XRD, SEM, pHPZC, and network and thermodynamic energies. The ACs of 0.025 g P2 for As(III) and V(V) were 112.24 and 88.89 mg g-1, respectively, at 308 K and within 5-100 mg L-1. The ACs reduced to 67.26, 75.49, 71.42, and 98.25 mg g-1 for As(III) and 40.25, 50.49, 45.37, and 67.88 mg g-1 for V(V) in the presence of Mn(II), Cu(II), Ni(II), and Zn(II), respectively.

Automated summary

In this study, an optimum sodium alginate-grafted hydrogel was selected among twelve synthesized hydrogels for adsorption of arsenic and vanadium. The grafted hydrogel showed improved swelling, crosslink density, and adsorption capacity, making it suitable for efficient removal of As(III) and V(V).