Highly efficient removal of As(V) by using NiAl layered double oxide composites

The NiAl layered double hydroxides (NiAl-LDHs) as well as NiAl layered double oxides (NiAl-LDOT, T: 300, 400, 500, 600 degrees C) were successfully synthesized by hydrothermal process and calcination treatment, and served as adsorbents for the efficient uptake of arsenate (As(V)) from aqueous solutions. Batch experiments were carried out at various solution pH, original As(V) concentration, contact time and calcination temperature. It was found that As(V) adsorption capacity on these composites can be changed by controlling the calcination temperature, and followed the order NiAl-LDO500 (198.1 mg/g) > NiAl-LDO400 (180.9 mg/g) > NiAl-LDO300 (160.2 mg/g) > NiAl-LDO600 (121.4 mg/g) > NiAl-LDH (60.7 mg/g), which could be ascribed to abundant surface adsorption sites and a memory effect provided by Ni-O or Al-O bonds. The thermodynamic experiments revealed that the elimination of As(V) was spontaneous and endothermic. In addition, multiple characterizations and batch experiments have been carried out to prove the surface adsorption and intercalation by rebuilding of primary layered structure contributed to As(V) adsorption. This discovery can provide a new insight into the elimination of As(V) from wastewater for environmental remediation. (C) 2018 Elsevier B.V. All rights reserved.