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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]

A phase transfer method was developed to prepare Mg(OH)2 nanosheets and a subsequent adsorption–calcination process was followed to obtain lamellar MgO nanostructures. The as-prepared MgO nanosheets also showed a superior adsorption property of Congo red. Transmission electron microscopy and x-ray diffractometer results indicated that the as-obtained Mg(OH)2 was plate-shaped with a hexagonal crystal structure where MgO possessed a lamellar structure with a cubic phase. The maximum adsorption capacities of Mg(OH)2 and MgO were reached up to 1820 and 2650 mg g−1, respectively. The high adsorption capacity might be related to the particle geometry and large surface area (87.97 m2 g−1 for Mg(OH)2 and 132.31 m2 g−1 for MgO). The adsorbents can be easily regenerated for five times without any significant loss in their adsorption property. The adsorption behaviors of the Mg(OH)2 and MgO adsorbents showed that the adsorption kinetics and isotherms were in good agreement with pseudo-second-order rate equation and Freundlich adsorption model. [ABSTRACT FROM PUBLISHER]

Highlights: [•] The iron oxide is gained via a facile, green, and economical synthesis process. [•] The promising adsorptive applications in water treatment are investigated. [•] Congo red removal capacity is 253.8mgg−1, and commercial α-Fe2O3 is 42.4mgg−1. [•] The maximum adsorption capacity for Cr(VI) is 17.0mgg−1. [ABSTRACT FROM AUTHOR]