Solidification/stabilization of mercury contaminated soil by geopolymer/MoS2 composites

Abstract

The present study is aimed to solidify and stabilize mercury contaminated soil (MCS) by molybdenum disulfide nanosheets (MoS2)/geopolymer composite, which is a novel and efficient treatment for MCS. Therefore, fly ash and blast furnace slag were used to prepare geopolymer, and MoS2 was synthesized via the hydrothermal method. Firstly, MSC was pre-adsorbed by MoS2 and the adsorption mechanism was investigated through the structure characterization and adsorption kinetics test. The results indicated that the MoS2 has outstanding Hg adsorption due to the complexation of Hg with intrinsic S on MoS2 surfaces, and the electrostatic interaction between MoS2 and Hg2+. Then geopolymer was used to solidify and stabilize MCS pre-adsorbed by MoS2. The compressive strength and leaching toxicity test demonstrated that the MCS/geopolymer/MoS2 composite could effectively solidify and stabilize Hg. The excellent Hg immobilization property of MCS/geopolymer/MoS2 was mainly attributed to the synergy effect between geopolymer and MoS2. Dispersed Hg was concentrated on MoS2 and then was encapsulated by geopolymer. Meanwhile, the MoS2 could accelerate the hydration process and decrease the porosity of geopolymer, which further strengthening Hg immobilization. The findings will provide a new strategy for immobile heavy metal pollution using two-dimensional nanosheet composites.