Single step synthesis of sulfidated nanoscale iron modified kaolin clay for hexavalent chromium remediation from groundwater

Abstract

Remediation of dissolved hexavalent chromium [Cr(VI)] is often achieved by iron nanoparticles [nZVI], sulfidated nZVI [SnZVI], and adsorption on clay minerals. Although different types of nZVI effectively removed Cr(VI), performance evaluation of nZVI modified with low-cost and naturally available kaolinite clay was not thoroughly studied. In the present research, kaolin was modified with nZVI (K-nZVI) and SnZVI (K-SnZVI) at two different kaolin to iron mass ratios (kaolin: Fe). Both K-nZVI and K-SnZVI were synthesized by a simple one-step process, avoiding complicated amalgamation methods of modified nZVI. Effects of ionic strength, pH, major cations, and anions in Cr(VI) remediation efficiencies were probed. Kinetics of Cr(VI) removal was quantified from sacrificial batch studies. Further experiments were performed in Cr(VI)-spiked synthetic groundwater matrix in the respective pH and initial Cr(VI) ranges of 5.5–8 and 2–100 mg L−1. With maximum Cr(VI) remediation efficiencies of 100% (K-nZVI) and 98% (K-SnZVI) in synthetic groundwater contaminated with 2–100 mg L−1 Cr(VI), both of these materials might be effectively used for groundwater treatment. The usage of kaolin—an analog of the natural kaolinite clay—with relatively decreased Fe content in the nanoparticles would reduce the treatment cost and provide insight into a sustainable solution for Cr(VI) contamination.