Comparativo dos processos de eletrocoagulação e coagulação/floculação aplicado no tratamento de efluente têxtil sintético

Abstract

Brazil has a strong economic movement in the textile industry, being responsible for revenue of 190 billion reais in 2021 and the clothing sector is the 2nd largest employer in the processing industry, second only to food. Due to its great importance, it is concerned with the different stages of the textile sector and its environmental impacts. The present study was carried out seeking to compare the efficiency of coagulation/flocculation and electrocoagulation treatments applied to a synthetic textile effluent containing the dye navy blue (AM-16). For the coagulation/flocculation process, aluminum polychloride (PAC 18%) and aluminum sulfate (Al2(SO4)3) were used as coagulants and cationic polymer (PC) as a coagulation aid. Coagulation/flocculation treatments were evaluated at dye concentrations in the range of 150 - 350 mg L-1, PAC-18% concentration (range of 10 - 50 mg L-1), PC concentration (range of 0.1 -0.5), initial pH (range 5-9). For the tests with Al2(SO4)3, the same study ranges were applied, with the only exception of the initial pH, where the range used was 4 to 8. For the electrocoagulation process, aluminum electrodes were used, and it was conducted using a concentration range for the dye of 150 to 350 mg L-1 and the applied current of 0.3 to 0.9 A. The variables responses were contaminant removal (AM-16), color removal, chemical oxygen demand (COD), total organic carbon (TOC) and toxicity reduction using the microcrustacean Artemia salina as a bioindicator. The objective was to compare the performance of different treatment methods (coagulation/flocculation and electrocoagulation), as well as evaluate how all independent variables and their interactions affected the efficiency of the processes. The results found through statistical analysis demonstrated that the factor with the greatest influence on the coagulation/flocculation process for removing the AM-16 dye concentration was the initial pH, both for PAC -18% and for aluminum sulfate (Al2 (SO4)3). However, for aluminum sulfate, the dye concentration also had an influence, indicating that the increase in pH and dye concentration favors removal. Regarding the toxicity of the effluent after the treatments, there was a maximum average reduction of approximately 11% for the treatment with Al2(SO4)3. Electrocoagulation did not present any significant variable at the levels studied, however it presented a good average performance in removing the dye concentration (83.68%) and color (95.1%) from the efluente. The two treatment processes evaluated (coagulation/flocculation and electrocoagulation) demonstrated efficiency for the studied variables and their levels. However, the coagulation/flocculation processes performed better if we take into account the removals obtained in the set of response variables evaluated.