Degradation of acid black 210 Na AZO dye through electro-oxidation with graphite electrodes

Dyes are widely used substances, however, if disposed of incorrectly in the environment, they can cause numerous problems. To degrade them, it is possible to use advanced oxidative processes (AOP) methods, such as electro-oxidation. This technique was used to degrade the azo dye Acid Black 210 Na. Four treatments were applied (A, B, C, and D) with electric current densities of 4, 12, 20, and 30 mA.cm −2 for 10 min, and the degradation was evaluated by molecular absorbance spectroscopy. Using ANOVA, it was verified that the most suitable condition for degradation corresponds to an electric current density of 20 mA.cm −2 (treatment C), obtaining degradation around 87 % for 459 nm and 95 % for 609 nm, since the degradation at 319 nm follows second-order kinetics, with a rate constant (K) of 0.561 and R² of 0.978. There was an increase in the toxicity of the samples, through the germination and growth of Lactuca sativa radicles and the test with Daphnia magna, after the treatments, possibly due to the presence of chlorine, since the absorbance analysis in the infrared region did not indicate the formation of toxic intermediates.