The treatment of chromium containing wastewater using electrocoagulation and the production of ceramic pigments from the resulting sludge.

This research experimentally investigates the treatment of authentic electroplating wastewater with high Cr(VI) content by electrocoagulation with the obtained sludge being reused as a raw material to produce inorganic pigments. A zero waste process is introduced to help conserve resources and to minimize environmental effects. The effects of operational parameters on electrocoagulation are determined in a batch stirred reactor using an iron electrode. The best performance was observed when a current density 20 mA/cm, pH 2.4 and 0.05 M NaCl electrolyte were maintained. The initial Cr(VI) concentration of 1000 mg/L was almost completely abated (∼100%) at an energy cost of 2.68 kWh/m, fulfilling the EPA guideline of 2.77 mg/L within a single step process. The sludge was characterized using XRD and XRF showing that the sludge is a rich source of iron and chromium and can be reused to produce value added ceramic pigments. Pigments prepared in this way appeared to be reddish brown and black color in transparent glaze and were also characterized using XRD and XRF. In this study, a zero waste process is successfully introduced with ∼100% Cr(VI) removal, with subsequent reuse of the resulting sludge.