Análise da aplicabilidade das reações de fenton no tratamento de efluentes de uma indústria cosmética por meio de delineamento composto central rotacional

Abstract

The industries of the cosmetic sector stand out among the industrial enterprises due to the generation of liquid effluents of difficult degradation, originating from the process of manufacture of the products, and cleaning of the reactors of daily manipulation of the factories. Thus, the objective of this work was to evaluate the efficiency of Fenton reactions (RF) in batch reactor in effluent degradation from a cosmetic industry in the state of Rio Grande do Sul. For this, experiments were performed varying the concentrations of oxidant (H2O2) and catalyst (Fe2 +). The variables treatment optimization responses are the reduction of chemical oxygen demand (COD), apparent color, turbidity and absorbance (λ - 350 nm). Fe2+ and H2O2 were optimized according to a Rotational Compound Central Design (RCCD), which totaled 12 assays. The results obtained in the DCCR were submitted to statistical analysis, confirming the coefficient correlation linear (R²) obtained for COD (R2 = 0,814), turbidity (R2 = 0,825), apparent color (R2 = 0,944) and absorbance at the wavelength of maximum absorption of the effluent (λ - 350 nm) (R2 = 0,7683), that the model was valid in the 95 % confidence interval (p < 0,05). Therefore, the optimized values were: 115,0 mg Fe2+ L-1 and 2.045,0 mg H2O2 L-1. Through monitoring the effluent degradation as a function of time and considering the physicochemical parameters: temperature, COD, conductivity, apparent color, turbidity, pH, sedimentable solids, oil and grease content, total suspended solids, fixed and volatile, it was found that the highest RF efficiency was achieved after 8 h of treatment. Under these conditions, 72,75 % of turbidity, 77,14 % of COD and 70,04 % of apparent color were removed, and the other parameters did not show removal. However, only the temperature and COD parameters met the emission standards in the water body determined by Resolutions N° 375/2005 and N° 430/2011 of the National Environmental Council (CONAMA) and Resolution N° 128/2006 of the Council State of the Environment (CONSEMA). Finally, it is suggested the study of the application of a previous treatment to the RF, in order to verify the possibility of better results in relation to the degradation of the cosmetic effluent.