Electrocoagulation method for treatment and reuse of sulphide mineral processing wastewater: Characterization and kinetics.

This study investigated the treatment and reuse of sulphide mineral processing wastewater through electrocoagulation (EC) and determined the optimum value of operational variables. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray fluorescence were used to analyze the characteristics of sludge produced in the EC. Results showed that the chemical oxygen demand (COD) removal efficiency reached 98.36% under the optimum treatment conditions. The amounts of sulfate (SO 4 2−) and calcium ion (Ca2+) pollutants in the wastewater decreased, with removal efficiency of 93.14% and 94.86%, respectively. The treated water was reused in the grinding system and exerted no negative effect on subsequent flotation. In addition, amorphous aluminum hydroxide (Al (OH) 3(s)) was formed during the EC and hydrocarbons, SO 4 2−, and Ca2+ appeared in the sludge in accordance with the characteristic of the EC products. In summary, the adsorption of amorphous Al (OH) 3(s) resulted in the removal of pollutants in the wastewater. The kinetic analysis of the EC system showed that the removal of pollutants obeyed the pseudo-second-order kinetic model, and the main rate-limiting step of the adsorption of amorphous Al (OH) 3(s) was chemisorption. Unlabelled Image • Electrocoagulation could remove COD, SO 4 2− and Ca2+ in mineral processing wastewater. • The adsorption of amorphous aluminum hydroxide resulted in the removal of pollutants. • The reuse of treated water into grinding system did not affect subsequent flotation. • The use of fresh water and the discharge of wastewater were reduced by water recycle. [ABSTRACT FROM AUTHOR]