Water-n-BuOH solvothermal synthesis of ZnAl-LDHs with different morphologies and its calcined product in efficient dyes removal

In this study, water-n-BuOH mixed solvents were used to synthesize the ZnAI-layered double hydroxides (ZnAl-LDHs) via hydrothermal method. The XRD, FT-IR, SEM, ICP and CHN analyses revealed that the type of intercalated anions, the layer Zn/A1 ratios, and morphologies of the LDHs depended on the ratio of V (water)/V(n-BuOH) in the mixed solvents. When the ratio of V(water)/V(n-BuOH) is 3 or 0.3, the as prepared LDHs had 3D silk flowers (ZnAI-LDH-3) or Sedimentary rock morphology (ZnAI-LDH0.3). Adsorption properties of dyes on calcined LDHs were studied. Compared with ZnAI-LDO-0.3 and ZnAI-LDO-w (calcined from the LDHs obtained in pure water), ZnAI-LDO-3 showed much better adsorption efficiency for anionic dyes thanks to its much larger BET-specific surface area. The sorption kinetics for dyes was appropriately described by the pseudo-second-order model and sorption isotherms can be fitted more satisfactorily by the Langmuir model. With the increasing concentrations of dyes from 10 mg/L to 400 mg/L, the maximum absorption capacities of ZnAl-LDO-3 were 1540 mg/g (2.21 mmol/g) for congo red, 1153 mg/g (3.52 mmol/g) for methyl orange and 390 mg/g (0.63 mmol/g) for active red (X-3B), respectively. The adsorption dyes onto the external surface is still the main mechanism for LDO adsorbents. The ZnAI-LDO-3 was a potential adsorbent for dyeing wastewater treatment. (C)2017 Elsevier Inc. All rights reserved.