Tratamento de efluente de indústria de tinta por processos conjugados de coagulação e oxidativo avançado

Abstract

In recent years, the search for new processes in the treatment of industrial effluents has become quite promising, especially considering the water crises that have occurred and that have become increasingly recurrent. In this sense, the present work proposes the combined use of coagulation techniques and advanced oxidative processes (AOP) in the treatment of a real effluent from the paint industry. Initially, the best experimental conditions for coagulation were obtained, using the chemical coagulant FeCl3 at a concentration of 400 mg/L, which resulted in the removal of 99.9% of turbidity, 98.6% of total solids and any apparent color. Continuing, considering the persistence of the characteristic odor and COD (645.2 mg/L), the use of AOP was continued, where the photo-Fenton, modified photo-Fenton and electrochemical processes were investigated, as well as the photo combinations -electro-Fenton and photo-electro-Fenton modified. Initially, tests were carried out to define the ideal experimental conditions of each process individually, as well as to define the radiation source (artificial or solar), which obtained results that indicated that the use of solar radiation presents better or equal performance to those obtained with artificial radiation, which led us to choose to follow the later experiments using solar radiation, thus minimizing the energy consumption of the process, in addition to having the sun as a source. Furthermore, it was possible to investigate the use of a complexing agent (the oxalate ligand), to overcome the limitation of operating in a strongly acidic medium (pH=3), where the use of potassium ferrioxalate ([FeOx] = 0.4 mmol/L), or simply by the in situ addition of the ligand (oxalic acid) in the proportion of 1:9, makes its use possible at pH = 5, presenting satisfactory efficiency in the removal of organic matter. Thus, the combination with the best performance in the treatment of real effluent from the paint industry was the chemical coagulation process combined with the photo-electro-Fenton modified Solar process ([FeOx] = 0.4 mmol/L, [H2O2] = 2, 0 g/L, i = 5 mA/cm2 , pH = 5, supporting electrolyte [Na2SO4] = 0.05 mol/L at an irradiance of 40.5 J/cm2 ). Under these conditions, the treated effluent resulted in the removal of 92% of COD, 99.9% of turbidity, complete removal of apparent color and odor (olfactory perception). Therefore, the use of combined techniques in the treatment of effluent from a paint industry proved to be satisfactory and very promising for applications in treatment plants.