Combined Coagulation and Electrochemical Process to Treat and Detoxify a Real Textile Effluent

Abstract

Combined coagulation and electrochemical treatment processes were used to mineralize the organic load and detoxify a real textile effluent. The coagulation step was investigated for distinct pH values (4 to 11) and Al2(SO4)3 concentrations (0.25 to 9.00 g L−1). Complete turbidity and partial total organic carbon (TOC) removals were attained at pH 5, using 0.50 g L−1Al2(SO4)3. Moreover, the coagulation process totally removed the initial toxicity (100 % mortality) of the effluent, assessed by toxicity tests with the crustacean Artemia salina. The remaining TOC was mineralized by the electrochemical step in a flow cell with a boron-doped diamond (BDD) anode, when the investigated parameters were the BDD boron-doping level (100, 500, 2500 ppm), pH (3, 7, 11, no control), and current density (10, 20, 30 mA cm−2). No significant differences in TOC removal were observed when the BDD anode or pH value was changed; however, as the system was under mass transport limitation, mineralization attained at low current densities led to a reasonable current efficiency (∼40 %) and low energy consumption (∼16 kW h m−3). The use of the electrochemical method solely led to poor TOC and turbidity removals, thus not being recommended.