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It is a challenge to achieve the harmless treatment and resourceful use of various metal elements in electroplating sludge, and converting them into functional materials has become an important technological direction. Based on the existence of various metal ions in electroplating sludge, sodium oleate intercalated Zn−Cr‐LDHs (Zn−Cr‐layered double hydroxides) were prepared by two‐phase solution heating method. The adsorption process of the prepared LDHs for Congo red (CR) in aqueous solution can be described by Langmuir isotherm model and pseudo‐second‐order kinetic model and the maximum adsorption capacity is 2750.43 mg/g. The results of TEM and XPS show that the adsorption mechanism is dominated by electrostatic adsorption, ion exchange process, hydrogen bonding interaction and surface complexation. Therefore, this paper provides a strategy for recovering metal elements from electroplating sludge to prepare LDHs adsorption materials with ultra‐high adsorption capacity. [ABSTRACT FROM AUTHOR]

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]