Simultaneous removal of chromium(VI) and Reactive Black 5 using zeolite supported nano-scale zero-valent iron composite

Pollution due to heavy metals and dyes has become a major global environmental issue. Simultaneous removal of heavy metals and dyes from wastewater remains a major challenge. In this study, a zeolite supported nano-scale zero-valent iron (Z-nZVI) composite was innovatively used for the simultaneous removal of Cr(VI) and Reactive Black 5 from aqueous solution. Experiments were carried out at different pH values (2–8) and adsorbent dosages (0.2–1 g L⁻¹). The maximum removal was found to be 99% for both Cr(VI) and Reactive Black 5 (RB5) at pH 3 with initial RB5 concentration 85 mg L⁻¹, Cr(VI) concentration 23 mg L⁻¹ and adsorbent dosage 1 g L⁻¹. A Freundlich model showed a satisfactory fit to the equilibrium adsorption data of a Z-nZVI composite with a correlation coefficient R² = 0.9790 for RB5 and R² = 0.9726 for Cr(VI). The kinetics of adsorption followed a pseudo-first-order model. The results of the study indicated that a Z-nZVI composite could potentially be used for the simultaneous removal of metals and dyes from wastewater.