Uso de terra diatomácea residual da indústria cervejeira em tecnologias avançadas de remoção de corantes e tratamento de efluente têxtil

Abstract

Advanced Technologies designed for the removal of environmental pollutants have attracted the interest of researchers for application in water and wastewater treatments, mostly those using low­cost materials, such as agroindustrial wastes. Previous studies showed that residual diatomaceous earth (RDE) from brewing industry showed a potential for biosorption of textile dyes, indicating that this material can be applied in advanced technologies for wastewater treatment. In this study, RDE was: (i) used for the biosorption of the textile dyes Acid Blue 277 (AB277) and Acid Red361 (AR361) in single and binary solutions and under the interference of salts and metals. (ii) chemically modified by acid treatment (RDE­A) and silanized with APTES (RDE­S) for the Biosorption of the textile dye Acid Black 172 (AB172) in ideal conditions of pH an at the real effluent pH value (5.0). and (iii) used as a biosorbent and a support for the immobilization of laccases RDE­LA) for the treatment of industrial wastewater. Biosorption capacity of RDE in binary solutions was of 4.26 and 8.35 mg g­1 respectively for AB277 and AR361, with a sum of 12.61 mg g­1 of dyes biosorbed, higher than the capacity in single solutions (8.29 mg g­1 for AR361 and 6.86 mg g­1 for AB277). The presence of salts and metals interfered negatively on biosorption in single solutions, but salts interfered positively in binary solutions. RDE­S showed a higher biosorption capacity than RDE and RDE­A in the pH of textile effluent. All biosorption tests were well represented by Langmuir and Sips isotherm models and by pseudo­second order kinetic model. Thermodynamic studies showed that biosorption of the dyes by RDE with or without chemical modifications is spontaneous and influenced by temperature. The immobilization of laccases in RDE­LA was optimized by factorial planning with three levels and successfully preserved 79.0% of enzyme activity at the best studied conditions (200 U L­1 and 1.5% of glutaraldehyde). Enzyme immobilization increased the stability of the enzymes at pH and temperature through time and preserved better enzyme activity after storage by freezing. RDE­LA could remove 66.2% of COD from the textile effluent and RDE­S could remove 55.0%, and there was a reduction of 24.0% and 27.9% in the effluent color for RDE­LA and RDE­S respectively when analyzed by UV­Vis. Wastewater treatment with RDE­LA and RDE­S reduced ecotoxicity in a test with Artemia salina. Infrared analysis by MIR­ATR contributed for elucidating thefunctional groups responsible for biosorption of textile dyes and indicated the presence of dyes and textile effluent components on the material surface.