Rapid and effective removal of Cr(VI) from aqueous solution using exfoliated LDH nanosheets

Direct exfoliation of lactate-intercalated [MgAl-NO3]-LDH nanocomposites (LCT-LDH) into single-layer LDH nanosheets in water media, termed LDHNSs, to enlarge the overall surface area and adsorption rate. The LDHN5 were then used as adsorbents to remove Cr(VI) from aqueous solution by batch adsorption method. Adsorption experiments considered the effects of various factors such as pH, dosage, contact time, and temperature on Cr(VI) removal efficiency. The morphology, texture, and surface properties of the [MgAl-NO3]-LDH, LCT-LDH, LDHNSs, and Cr-LDHNSs were characterized by HRTEM, AFM, XRD, FT-IR, XPS, elemental analyzer and zeta potential analyzer. It was found that the optimum pH for Cr(VI) maximum removal efficiency onto LDHNSs was pH 6.0. Adsorption data were found to be better fitted by the Langmuir isotherm, and the maximum adsorption capacity of LDHNSs for Cr(VI) was 125.97 mg/g at 308 K. The adsorption of Cr(VI) onto LDHNSs was rapid, and the contact time required to reach complete adsorption equilibrium within 8 min. Thermodynamic analysis showed that the adsorption process was endothermic, spontaneous, and physical in nature, involving weak interactions such as electrostatic attraction, ion-exchange, and hydrogen bonding between the Cr(VI) species and the binding sites on the LDHNSs. (C) 2017 Elsevier B.V. All rights reserved.