A comprehensive investigation of zeolite-rich tuff functionalized with 3-mercaptopropionic acid intercalated green rust for the efficient removal of Hg and Cr in a binary system.

In this study, the 3-mercaptopropionic acid (MA) was chosen to achieve the anionic intercalation into the green rust (GR) materials (MA-GR). The zeolite-rich tuff functionalized with the MA-intercalated GR (MA-GR-tuff) was subsequently synthesized and used to remove both Hg cations and Cr anions in a binary system. MA-GR-tuff showed the best adsorption capacities to both Hg and Cr among the adsorbent materials. The optimal combination of parameters was determined as the molar ratio of Fe to Fe of 3.5, the molar ratio of OH to the total iron of 3.75, the molar ratio of MA to the total iron of 2.5, and the mass ratio of the total iron to the tuff of 1.25. The pseudo-first-order kinetic model was appropriate in describing the kinetic sorption of Cr by MA-GR-tuff. Both the pseudo-first-order kinetic model and Elovich were suitable for explaining Hg sorption. The maximum monolayer adsorption capacities of MA-GR-tuff towards Cr and Hg were 185.19 mg/g and 72.99 mg/g, respectively. More flocs and plumes were formed in the MA-GR while the intercalation and more pores and crevices of different sizes were found in the MA-GR-tuff. Sulfhydryl complexation and the molecular sieve of tuff obviously both played a role in influencing the adsorption process. This study directly overcomes the drawback brought by the natural tuff to the treatment of a cationic-and-anionic binary system and supplies a new kind of tuff-based adsorbent for the potential use for the remediation of HM-contaminated wastewater.