Research on the treatment of acidic dye wastewater using bentonite-loaded zero-valent aluminum coupled flocculation method

Abstract

The global economy's continuous development has intensified the challenges associated with industrial wastewater treatment. This study synthesizes bentonite-loaded zero-valent aluminum (B-ZVAl) materials using physicochemical methods and explores their application for adsorbing and degrading pollutants in dye wastewater. The process exploits the intrinsic electron transfer capability of zero-valent aluminum (ZVAl) alongside the generation of active free radicals and flocs during the reaction. Orthogonal experiments were conducted to assess the impact of key factors including material loading, reaction pH, dosage, reaction temperature, and settling time on the decolorization efficiency of dye wastewater. Under optimal conditions (50% loading, 90-min settling time, pH 3, 2.5 g/L dosage, and 20°C reaction temperature), the decolorization rate of acid red dye wastewater reached 98.07%. Additionally, chemical oxygen demand (COD) was reduced by 72.36%, total organic carbon (TOC) by 65.34%, with an effluent pH of 7.38 and an aluminum concentration of 0.024 mg/L. Reusability tests indicated that the material retained significant decolorization and adsorption performance after three cycles. Characterization techniques including scanning electron microscopy (SEM), energy disperse spectroscopy (EDS), and x-ray diffraction (XRD) confirmed the stability of the B-ZVAl material before and after reactions, while UV-visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), and three-dimensional excitation-emission matrix (3D EEM) analysis further demonstrated the composite material's efficiency in decolorizing dye wastewater and reducing pollutant levels. In conclusion, the novel composite material not only overcomes the issue of ZVAl oxidation but also ensures a low residual aluminum concentration in the treated water, thereby reducing the potential risk of biological toxicity.