Treatment of galvanic effluent through electrocoagulation process: Cr, Cu, Mn, Ni removal and reuse of sludge generated as inorganic pigment

Galvanic effluents are composed of a wide range of heavy metals, requiring adequate treatment to remove these contaminants and to meet the limits established by environmental agencies. Considering this aspect, the present study had as main objectives: (i) to evaluate the efficiency of the electrocoagulation (EC) in the treatment of a galvanic effluent, with the purpose of removing total Cr, Cu, Mn, Ni and (ii) reuse the sludge generated for inorganic pigment production. EC tests were carried out through factorial design 2(3) with triplicate central point. pH (3, 7, 11), reaction time (15, 22.5 and 30 min) and current density (10, 17.5 and 25 mA/cm(2)) were the control variables. Under ideal experimental conditions (pH 7.00; t = 22.5 min and DC = 17.5 mA/cm(2)) were removed 96.94% of Mn, 97.63% of Cu and 99.99% of total Cr and Ni, allowing to meet the limits provided in CONAMA Resolution 430/2011. The production of inorganic pigments from a mixture of 10% sludge (generated in the ideal experimental condition) and Al2O3 and TiO2 proved to be technically viable. It was obtained 8.27 g of a brown inorganic pigment, composed mainly of Al1.82Cr0.18O3, Ca-0.999(Ti0.805Fe0.201)O-2.899 and Fe2.18O4Ti0.42. Therefore, the results obtained demonstrate that EC is an effective technique in galvanic effluents treatment. The sludge generated in this process showed to be appropriated to be reused in inorganic pigment production and could be considered as an alternative to reduce the environmental impact related to electroplating process.

Automated summary

The study successfully removed heavy metal pollutants from galvanic effluents using electrocoagulation, and reused the generated sludge for inorganic pigment production, reducing the environmental impact related to electroplating process.