Reactivity enhancement of ferrous sulfide by Poly-Sodium Acrylate cryogels on aqueous Cr(VI) removal: Performance and mechanism

FeS nanoparticles have been reported to exhibit efficiency in Cr(VI) removal, while it might fail in practical water treatment engineering. A novel monolithic composite (PSA-nFeS) by embedding nFeS into Poly Sodium Acrylate (PSA) through ion-exchanging and homogeneous precipitation was therefore synthesized in this study. PSA-nFeS showed high efficiency in Cr(VI) removal in pH 2-10, corresponding to an enhancement of efficiency from 16.40 % (41.30 mg Cr(VI) per g nFeS) to 90.51 % (282.43 mg Cr(VI) per g nFeS) relative to that achieved by nFeS. The removal mechanism of PSA-nFeS was further elucidated via SEM, EDS, FTIR, XRD and XPS. The results showed that reduction and adsorption accounted for 81 % and 19 % of Cr(VI) removal respectively, and Fe(II) played a key role in Cr(VI) reduction with the contribution of three times as much as S(-II), which was confirmed by density functional theory (DFT) calculation. Furthermore, PSA cryogel also facilitated the electron transfer process of interfacial Cr(VI) reduction demonstrated by EIS and LSV. This work suggested a novel multifunctional material for high-effective treatment of aqueous Cr(VI) in practical engineering application.