Two-Stage Waste Treatment for Hexavalent Chromium
Waste treatment of hexavalent chromium is a two-stage process. [S1] The hexavalent chromium is first reduced to the trivalent chromium ion; then it can be precipitated as chromium hydroxide. [S1]
Alternative Removal Approaches Reported in the Literature
Ion-exchange elimination of hexavalent chromium [Cr (VI)] from electroplated industrial wastewater has been investigated as a treatment option. [S2]
Uptake of hexavalent chromium in electroplating wastewater by hydrothermally treated and functionalized sand has been studied, and its sustainable reutilization for glass production has been considered. [S3]
Batch adsorption using two different nano-adsorbents—purified carbon nanotubes (P-CNTs) and polyhydroxylbutyrate functionalized carbon nanotubes (PHB-CNTs), both produced through catalytic chemical vapour deposition (CCVD) method—has been investigated for the removal of heavy metals, including As, Pb, Cr, Cd, Ni, Cu, Fe, and Zn, from industrial electroplating wastewater. [S4]
Pre-Treatment by Precipitation and Flocculation
Electroplating wastewater containing Cr (VI), Cu 2+ and Ni 2+ is a mixture from electroplating production lines in the electroplating park. [S5] The wastewater was pretreated by precipitation and flocculation before utilizing them in present experiments. [S5]
Summary of the Reduction–Precipitation Sequence
The reduction step converts hexavalent chromium to the trivalent chromium ion, which is then precipitated as chromium hydroxide. [S1] Other reported handling options for hexavalent chromium in electroplating wastewater include ion-exchange elimination [S2], adsorption onto hydrothermally treated and functionalized sand with potential reuse in glass production [S3], and batch adsorption using P-CNTs and PHB-CNTs produced by the CCVD method for mixed heavy-metal removal [S4]. Mixed electroplating wastewater containing Cr (VI), Cu 2+ and Ni 2+ has been subjected to precipitation and flocculation as a pre-treatment step. [S5]