Efficient promotion of Cr(VI) removal over Bi2S3 nanoparticles with cupric ions: Potential applications in electroplating wastewater and contaminated groundwater

Abstract

Emerging Bi2S3-based nanotechnology has great potential in Cr(VI)-contaminated wastewater treatment. In this work, it was found for the first time that Bi2S3 nanoparticles (BS-D) prepared from dual sulfur sources of L-cysteine and ammonium sulfide efficiently promoted Cr(VI) removal with excellent selectivity for simultaneous removal of Cr(VI) and Cu2+ from aqueous solutions containing various co-existing ions (including Na+, K+, Ca2+, Zn2+, Ni2+, Cd2+, NO3–, SO42− and Cl−) at pH > 3, preferably at pH of 4.5. Besides, BS-D had stable performance for co-removal of Cr(VI) and Cu2+ in five recycling tests. Kinetic and thermodynamic studies indicated that the adsorption of Cr(VI) or Cu2+ by BS-D was a spontaneous endothermic process and conformed to pseudo-second-order kinetic model. The adsorbed Cr(VI) ions were partially reduced to Cr(III), which were leached into the solution at pH ≤ 3, inhibiting the adsorption of Cu2+ on BS-D and its promotional effect on Cr(VI) removal by BS-D. The mutual promotional effects between Cu2+ and Cr(VI) during their co-removal by BS-D were ascribed to electrostatic attraction between HCrO4− and Cu2+ and smaller pH variation in mixed Cr(VI)-Cu2+ solutions. Finally, potential applications of BS-D were demonstrated by co-removal of Cr(VI) and Cu2+ from real electroplating wastewater and contaminated groundwater. This work provided a promising BS-D adsorbent for Cr(VI)-contaminated wastewater treatment, and shed insight on the influence of Cu2+ on the Cr(VI) removal by BS-D.