Destabilization and Removal of Mixed Organic-Chromium Complexes from Leather Wastewater by Ultrasonic-Assisted Precipitation

During the leather tanning process, chromium (Cr) can interact with different macromolecular organics to generate mixed ligand complexes. The removal of organochromium complexes is one of the main difficulties in the treatment of tannery wastewater. In this study, a gelatin-gallic ac-id-Cr(III) (G-GA-Cr) mixed ligand complex was used to examine the effects of ultrasonic on chromium destabilization and removal from the dissolved complexes. To investigate organic destruction and chromium liberation, alkali precipitation or chelating precipitation assisted with ultrasound were conducted, respectively. The findings demonstrate that ultrasonic-assisted alkali precipitation and chelating precipitation, respectively, removed over 50% and 93% of Cr from the complexes. According to the data, ultrasonication weakened the bonds that bound macromolecular ligands together, and depolymerization took place to the point where Cr could interact directly with hydroxide ions or chelating agents. In addition, by applying ultrasonic-assisted chelating precipitation, the chromium concentration could meet the discharge standard and the amount of precipitation was also noticeably decreased.