The goal of this study was to investigate the activity of the coagulant extracted from the cactus Opuntia ficus-indica (OFI) in the process of coagulation/flocculation of textile effluents. Preliminary tests of a kaolinite suspension achieved maximum turbidity removal of 95 % using an NaCl extraction solution. Optimization assays were conducted with actual effluents using the response surface methodology (RSM) based on the Box-Behnken experimental design. The responses of the variables FeCl3, dosage, cactus dosage, and pH in the removal of COD and turbidity from both effluents were investigated. The optimum conditions determined for jeans washing laundry effluent were the following: FeCl3 160 mg L(-1), cactus dosage 2.60 mg L(-1), and pH 5.0. For the fabric dyeing effluent, the optimum conditions were the following: FeCl3 640 mg L(-1), cactus dosage 160 mg L(-1), and pH 6.0. Investigation of the effects of the storage time and temperature of the cactus O. ficus-indica showed that coagulation efficiency was not significantly affected for storage at room temperature for up to 4 days.
The present work investigated the degradation of a dyeing factory effluent by advanced oxidative process under UV irradiation. TiO and ZnO were used as catalysts and the influence of different concentrations of HO added to the system was studied. The catalysts were characterized in terms of crystal structure (X-ray diffraction), textural properties (Brunauer-Emmett-Teller area and pore volume) and point of zero charge, which indicated the semiconductors had a positively charged surface in an acidic medium. After 8 h of irradiation at pH 3.0 and catalyst concentration of 0.0625 g L, the effect of HO was evaluated by means of kinetic efficiency (rate constants), absorbance reduction (at 284, 621 e 669 nm), total organic carbon reduction and mineralization (in terms of the formation of ions such as [Formula: see text] and [Formula: see text]). Adding HO to the photocatalytic system significantly increased pollutants' removal, highlighting tests with 1.0 × 10 mol L, showing higher absorbance reduction and rate constants at 621 and 669 nm for TiO and best mineralization rates for ZnO. Ecotoxicity bioassays using Artemia salina L confirmed the treatment efficacy, with effluent lethal concentration (LC) increasing from 65.68% (in natura) to over 100% after photocatalysis treatment.
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