Electrochemical degradation and toxicity evaluation of reactive dyes mixture and real textile effluent over DSA® electrodes

Electrochemical oxidation was applied to degrade three reactive dyes, blue 19 (RB19), red 195 (RR195) and yellow 145 (RY145), a mixture of dyes and real textile effluent. A 2(3) full factorial design coupled with a response surface methodology (RSM) was conducted. Considering the analysis of variance (ANOVA), statistical models could be used to describe experimental results and to predict the process behavior. RSM indicated the optimum conditions (30 mA cm(-2); 75 ppm and NaCl), obtaining 100 % of removal. The kinetic study followed a first-order model. The mixture and the real textile effluent obtained lower removal, 59 % and 48 %, respectively. The phytotoxicity tests using lettuce indicate the electrochemical reactions were effective to reduce the toxicity of almost all contaminated solutions, however, for more complex solution (mixture of dyes and real effluents), a longer reactional time is necessary. Also, chlorine species in the reaction medium can promote the germination due the oxidative which may help to break the seeds shells, nevertheless, such chemicals are harmful to the plant causing death before the growth. Therefore, the results pointed that the electrochemical reactions are efficient in solution discoloration and can be optimized to treat real textile effluents, indicating a reuse possibility for agricultural purpose.