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Al 2 O 3 /carbon (Al 2 O 3 /C) composites obtained from the alkaline wastewater of oil refinery and acid wastewater of aluminum anodizing factory have been studied with the principle of “using waste to treat waste”. The process includes these steps: (1) acid-alkali neutralization, (2) evaporation, (3) calcination, (4) washing and drying. The Al 2 O 3 /C composites prepared by calcinating the precursors under Ar atmosphere are used as high-capacity adsorbents for removal of Pb(II) and Cd(II) from aqueous solutions. For Pb(II), the adsorptive behavior satisfies the Langmuir assumptions and the maximum adsorption capacity reaches to 709.2 mg g −1 . For Cd (II), the adsorptive behavior satisfies the Freundlich assumptions and the equilibrium adsorption capacity is up to 1299.4 mg g −1 . For single adsorption of Pb(II) and Cd(II), the adsorption kinetics follows Pseudo-second-order model well. This route shows a possible way of reducing emissions to the environment, recovering resource as a valuable material, and providing a novel strategy for wastewater treatment. [ABSTRACT FROM AUTHOR]

Alkaline wastewater is high-concentrated and refractory organic wastewater from oil refinery, and its chemical oxygen demand (COD) ranged from tens of thousands to more than 100,000 mg L −1 . This kind of wastewater is very difficult to deal with. In this study, natural bentonite (BT) was used as the adsorbent to treat the alkaline wastewater. Subsequently, the used BT containing numerous organic compounds was calcined in inert atmosphere to prepare BT/carbon composite (BTCC). This adsorption-calcinations process can be repeated for 9 times and the adsorption performance does not decrease. The characterization results confirmed that as-prepared BTCC has irregular flake-shaped structures, and the carbon content of samples was increased with increased recycle. The adsorbents can be recycled to deal with alkaline wastewater and reduce the COD value of alkaline wastewater. The percentage removal of COD was 91% after recycling 9 times. Moreover, the recycling BTCC also showed superior adsorption behavior for methylene blue (MB). The equilibrium adsorption isotherms were better fitted by the Freundlich isotherm, and the kinetics model of MB adsorption was ideally conformed to pseudo-second-order model. This process realized the principle of “using waste to treat waste”, and obtained excellent recyclable adsorbent material for organic wastewater treatment. [ABSTRACT FROM AUTHOR]