Investigação de efluente têxtil com corante Laranja Reativo 64 tratado por oxidação avançada (US/H2O2)

Abstract

Water resources are of great importance for the maintenance of life, but only a minimal portion is available for human consumption, which is then threatened daily with improper discharges of industrial effluents, from which a large part is generated by the textile industry. Textile effluents have strong colors, containing many dissolved compounds, and are usually toxic. Azo dyes are the most commonly used synthetic dyes, as they have an easy synthesis path, with a wide color spectrum, and desirable physicochemical properties. However, azo dyes are difficult to degrade, and may have high toxicity, thus an efficient process is in demand to degrade such toxins generated by these dyes within textile effluents. Advanced Oxidation Processes (AOPs) using ultrasound combined with hydrogen peroxide have shown to be a good alternative in dye degradation, when they can be applied as pretreatment or post treatment. Reactive Orange 64 is a dye that belongs to the azo class and currently does not have much information in the literature about its degradation and toxicity. This paper performed the degradation of Reactive Orange 64 in a synthetic effluent using Ultrasound/H2O2. Analysis were performed at 0 h, 24 h, 48 h, 72 h, 96 h, 120 h and 168 h after treatment to observe variations in color, pH, conductivity, salinity, turbidity, suspended solids, total dissolved solids, dissolved oxygen, and concentrations of chloride, nitrate, sulfate, sodium, and fluoride. Although the dye could not be completely degraded due to a lower hydrogen peroxide percentage than specified in the reagent label, partial dye degradation occurred, as evidenced by both the spectrophotometer results and the physicochemical properties of the solution. When compared to the untreated synthetic effluent, the partially degraded solution had, at the end of the 7-day period: lower apparent color, total dissolved solids, conductivity and salinity; higher turbidity and dissolved oxygen; and similar values of suspended solids and pH. Ion chromatography detected a lower chloride concentration in the post-treatment solutions when compared to the control solution, suggesting that some chloride is now in the precipitate. In addition, it presented a higher Nitrate concentration at the end of the process than initially, which also indicates the breakdown of the azo or chromophore bond present in the molecule.