Round-the-clock Cr(VI) removal from actual industrial electroplating wastewater over Bi2S3/PDA/PEI under natural conditions: Synergism of adsorption and photocatalysis

To achieve an effective and straightforward method for Cr(VI) removal from industrial wastewater, a composite Bi 2 S 3 /PDA/PEI material (BSPP) was successfully prepared through in-situ polymerization of polydopamine (PDA) followed by chemical grafting with polyethylenimine (PEI) on the surface of Bi 2 S 3 materials for round-the-clock highly efficient Cr(VI) removal from actual industrial electroplating wastewater. Under dark conditions, the maximum adsorption capacity of Cr(VI) by BSPP reaches 780.75 mg/g. Interestingly, when exposed to light, the maximum Cr(VI) removal capacity was further increased to 1333.21 mg/g. X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma optical emission spectrometry (ICP-OES) analyses indicate that BSPP not only reduces Cr(VI) to Cr(III) under light condition, but also facilitates the significant decrease of total chromium content. Notably, under natural sunlight exposure outdoors, BSPP is capable of completely eliminating Cr(VI) from both plating cleaning solutions and waste plating solutions. More importantly, BSPP maintains its original Cr(VI) removal efficiency after nine cycles within plating cleaning solutions and six cycles within waste plating solutions. Large-scale testing results indicate that BSPP can effectively treat substantial volumes of electroplating wastewater to comply with national Cr(VI) discharge standards. These findings suggest that BSPP represents a promising material for continuous 24-hour Cr(VI) treatment in industrial electroplating wastewater.