Green rust functionalized geopolymer of composite cementitious materials and its application on treating chromate in a holistic system.

Green rust functionalized geopolymer of composite cementitious materials (GR-CCM) was synthesized to improve the adsorption and subsequent stabilization/solidification of chromate in a holistic operating system. The initial pH in solution exhibited the most significant effect on the chromate removal by GR-CCM among three adsorption factors. The maximum monolayer adsorption capacity and theoretical saturation capacity of GR-CCM for Cr(VI) in the acidic condition were 55.01 mg/g and 41.70 mg/g, respectively. Amorphousness brought by loading GR weakened the crystallinity of composite cementitious materials (CCM), which enhanced the adsorption capacity of CCM and boosted the solidification process. The mixed-valent iron species in the GR-CCM not only directly engaged in the adsorption and reduction of chromate also positively strengthened the solidification of Cr species during the whole treatment. This study facilitates the application of GRs on the geopolymer materials and demonstrates the combination of adsorption and immobilization for the treatment of other potential heavy metal contamination.