Highly efficient Cr (VI) removal from electroplating wastewater by regenerable copper sulfides: Mechanism and magical induction effect for Cr resource recovery.

The current sorbents used to remove Cr (VI) from electroplating wastewater are faced with some challenges including the difficulty in separating, regenerating, and safely disposing of adsorbed Cr species. To address these challenges, CuS x /TiO 2 was developed to recover Cr (VI) from electroplating wastewater. CuS x /TiO 2 had superior performance in removing Cr (VI), with the rate and capacity of approximately 9.36 mg g−1 h−1 and 68.8 mg g−1 at initial pH 4.0, respectively. Additionally, Cu2+ released from CuS x /TiO 2 during Cr (VI) removal would come back to its external surface as the Cu(OH) 2 precipitate at initial pH 4.0, which helped to prevent the generation of secondary pollution. The Cu(OH) 2 precipitate would be decomposed into CuO x after calcination, which would then be transformed back into CuS x by re-sulfuration for regeneration. Hence, CuS x showed a magical induction effect on Cr (VI) recovery, and Cr (VI) from electroplating wastewater might be gradually enriched as Cr 2 O 3 in the sandwich between CuS x and TiO 2 through multiple regenerations and removals, which could be considered as a chromium ore resource for industrial applications when the amount of enriched Cr 2 O 3 reached more than 30 wt%. Overall, CuS x /TiO 2 showed great potential as a promising sorbent for Cr (VI) removal from electroplating wastewater. [Display omitted] • CuS x exhibits superior performance in removing Cr (VI), which outperforms common FeS x. • CuS x /TiO 2 can be recycled for Cr (VI) removal after regeneration. • CuS x shows a magical induction effect on Cr (VI) recovery. • CuS x /TiO 2 is a promising sorbent for Cr (VI) removal from electroplating wastewater. [ABSTRACT FROM AUTHOR]