Highly efficient Cr(VI) removal from industrial electroplating wastewater over BiS nanostructures prepared by dual sulfur-precursors: Insights on the promotion effect of sulfate ions.

In this work, different BiS nanostructures were prepared from various single and dual sulfide precursors via a solvothermal method. It was found that BiS nanostructures prepared from dual sulfur precursors of L-cysteine and ammonium sulfide exhibited highest Cr(VI) removal ability with maximum Cr(VI) removal capacity of 148.95 mg/g in Cr(VI) solution (pH = 2). More importantly, the removal capacity strikingly increased to 223.33 and 240.25 mg/g in two kinds of actual industrial electroplating wastewater. By analyzing the components of actual electroplating wastewater and the results of control experiments in the absence and presence of different ions in Cr(VI) solution, it was found that SO played a critical role in the Cr(VI) removal over BiS. The addition of SO could promote the conversion of Cr(VI) to Cr(III) on the surface of BiS, thus leading to the enhanced Cr(VI) removal ability in actual electroplating wastewater. The BiS maintained its original Cr(VI) removal ability after four cycles in the electroplating wastewater, indicating the moderate reuse ability of the sample. This work not only demonstrated an highly efficient nanomaterials for the Cr(VI) removal in industrial electroplating wastewater, but also provided an insight on the influence of the components in wastewater on Cr(VI) removal.