Simultaneous adsorption of As(V) and Cr(VI) by zeolite supporting sulfide nanoscale zero-valent iron: Competitive reaction, affinity and removal mechanism

In this study, ZSM-5 zeolite supporting sulfide nanoscale zero-valent iron (S-nZVI@ZSM-5) composite adsorbent was synthesized to remove As(V) and Cr(VI) in single and binary system. The affinity of S-nZVI@ZSM-5 to As(V) and Cr(VI) and the main adsorption mechanism of them were investigated. The characteristics of S-nZVI@ZSM-5 were investigated using BET surface area, SEM, TEM, FTIR, XRD and XPS analyses. The Langmuir maximum adsorption capacity of As(V) and Cr(VI) on S-nZVI@ZSM-5 at pH 4.0 was calculated as 161.66 mg/g and 52.16 mg/g in single system, and that was reduced by 13.01% and 63.08% in binary system, respectively. Kinetic results were evaluated to obey the pseudo-second-order model, regardless of single or binary system. Aging time of S-nZVI@ZSM-5 was assessed and the removal performance of As(V) and Cr(VI) maintained 99.14% and 81.70% of freshly prepared S-nZVI@ZSM-5 capacity after 5 days aging, respectively. The findings herein highlight the higher chemical affinity of S-nZVI@ZSM-5 to As(V) than Cr(VI). Moreover, X-ray photoelectron spectrometer (XPS) results demonstrated that As(V) was directly adsorbed on S-nZVI@ZSM-5 surface by co-precipitation, and the reduction of Cr(VI) to Cr(III) were found to be the primary approach for Cr(VI) adsorption. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study synthesized a composite adsorbent S-nZVI@ZSM-5 for the removal of As(V) and Cr(VI) in single and binary systems. The characterization of S-nZVI@ZSM-5 and its high chemical affinity to As(V) were highlighted, along with the main adsorption mechanisms investigated using various analytical techniques.