Electrocoagulation of the indigo carmine dye using electrodes produced from the compression of metallurgical filing wastes

Indigo carmine (IC) is a dye that is widely used in textile industries. Since the dyes lixiviation reaches about 30%, these compounds are largely discharged in effluents, thus contaminating rivers and lakes. The IC presents high toxicity, causing topic irritation and carcinogenic effects. Electrocoagulation (EC) is based on the electrical dissolution of iron and aluminum ions used to promote the formation of metal hydroxide coagulants capable of destabilizing and aggregating pollutant compounds. In this context, this work aimed to investigate the use of electrodes obtained from the direct compression of metallurgical filing wastes on the EC remediation of IC. Electrodes of bronze, aluminum, steel and metal waste were produced and their performances were evaluated in NaCl 0.05 mol L-1 and tap water solutions at 2.5 and 5 V. The IC dye discoloration reached 84% for the aluminum commercial electrode, 90% for the steel commercial electrode and 96% for the bronze commercial electrode, respectively, in 80 min of treatment. For electrodes produced from chips (swarf), there was a discoloration of 72% for the aluminum electrode, 92% for the steel electrode and 90% for the bronze electrode, respectively, in the same time of treatment. These results showed that electrodes obtained from chips and commercial electrodes had similar electrochemical efficiency in the removal of IC dye from wastewater. Also, the use of metallic debris as electrodes makes its application an economically viable option on a large scale, since they have high effectiveness and lower cost and their replacement can solve the electrode passivation.