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 ([email protected]) composite adsorbent was synthesized to remove As(V) and Cr(VI) in single and binary system. The affinity of [email protected] to As(V) and Cr(VI) and the main adsorption mechanism of them were investigated. The characteristics of [email protected] 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 [email protected] 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 [email protected] was assessed and the removal performance of As(V) and Cr(VI) maintained 99.14% and 81.70% of freshly prepared [email protected] capacity after 5 days aging, respectively. The findings herein highlight the higher chemical affinity of [email protected] to As(V) than Cr(VI). Moreover, X-ray photoelectron spectrometer (XPS) results demonstrated that As(V) was directly adsorbed on [email protected] surface by co-precipitation, and the reduction of Cr(VI) to Cr(III) were found to be the primary approach for Cr(VI) adsorption.