Estudo da remoção de Cu (II), Ni (II) e Fe (II) de efluentes de galvanoplastia por eletrocoagulação com corrente pulsada

Abstract

Several industries in Brazil use toxic metals in high scale processes, which, posteriorly, need to be discard in the concentration allowed by law, according with the resolution nº 430 by CONAMA. The industrial sector in Ceará is represented mainly by shoes, clothing, food, beverages, jewelry and plated jewelry industry, the latter being characterized as electroplating industry, that Juazeiro do Norte/CE is the most important national pole. In this work, it was developed an electrochemical cell using pulsed direct current, being applied to the treatment of electroplatings’ effluents. The best condition was using 1,5 L of synthetic effluent with Cu2+ (55 mg L-1), Ni2+ (7 mg L-1) e Fe2+ (85 mg L-1), on the conditions of pH0 = 4,0, j=7,14 mA/cm2, aluminum electrodes, 666,7 mg L-1 of NaCl and agitation of 600 rpm in 30 minutes of treatment. Using that conditions, the removal percentage of copper, nickel and iron were 98,3 ±0,7 %, 94,7 ±1,1 % e 100 %, respectively, and the final concentration of soluble Al3+ was 0,21 ±0,03 mg L-1. Appling these conditions in the real effluent treatment, the results were satisfying, being the removal percentage of the metallic ions higher than 85 %, but, even though, the wastewater still was very toxic to aquatic organisms, probably because the high concentration of anions, which remained in the aqueous medium after the treatment. The mass loss test of the aluminum electrodes showed that as the pH increased, greater is the wear on the metal plates. The influence of the aluminum and titanium electrodes coated by platinum was evaluated, even in the presence and absence of iron in the system. It was observed that the presence of iron affected negatively the Cu2+ and Ni2+ removal, even when was used Al electrodes and Ti/Pt electrodes. The best removal condition to Cu2+ and Ni2+, in the concentration studied, was using aluminum electrodes, in the absence of iron, for 20 minutes and that the percentages were 99,9 % for Cu and 98,5 ±1,1 % for Ni. The use of Ti/Pt electrodes favored only the iron removal, which was 93,8 ±1,8 %.