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Graphical abstract Abstract Potassium humate possesses a wide variety of oxygen-containing functional groups and has good adsorption and complexation properties for many kinds of transition metal ions. In this work, a simple and separable route had been developed to synthesize Fe 3 O 4 /graphene nanocomposite, derived from potassium humate, were employed for the effective adsorption of Cr(VI) in aqueous phase. In addition, the Fe 3 O 4 /graphene nanocomposite prepared at 600 °C (S-600) showed a maximum adsorption capacity of 280.6 mg/g for Cr(VI) and good cycling performance, which was much higher than those reported graphene-based adsorbents and other conventional adsorbents. The adsorptive behavior was well fitted to the Langmuir isotherm model. The adsorption kinetics for removal of Cr(VI) agreed with pseudo-second-order equation, which indicates a kind of chemical adsorption. Its superior adsorption performance might be due to the effective adsorption sites at the surface and formation of FeOH2+ on the surface of Fe 3 O 4 /graphene. This work provided a promising approach for the removal of Cr(VI) from wastewater using a Fe 3 O 4 /graphene nanocomposite, which shows a huge number of application prospects. [ABSTRACT FROM AUTHOR]

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]