Mg–Al layered double hydroxides modified clay adsorbents for efficient removal of Pb2 +, Cu2 + and Ni2 + from water

• The adsorption properties of Pal/CLDH for Pb2 +, Cu2 + and Ni2 + were the best among several adsorbents.
• The adsorption capacity of Pal/CLDH for Ni2 + was almost 3 times that of Pal/MgAl–LDH.
• Surface precipitation of Pb2 + and isomorphous substitution of Mg2 + by Cu2 + or Ni2 + was main adsorption mechanisms.
• The adsorption capacities sequencing of adsorbents for metal ions was Pb2 + > Cu2 + > Ni2 +.

Highly effective clay adsorbents of Mg–Al layered double hydroxides modified palygorskite were prepared from the mixture of metal salts, urea and palygorskite by the in situ hydrothermal crystallization method. The obtained adsorbents were characterized by FT-IR, TG, XRD and SEM/EDS. The adsorption performances were evaluated for the removal of Pb2 +, Cu2 + and Ni2 + in the aqueous solution. The adsorption capacities of the three metal cations at variable pH, contact times and metal concentrations were determined by atomic adsorption spectrometry. The adsorption capacities of the three metal cations on Mg–Al layered double hydroxides modified palygorskite were higher than those of palygorskite and Mg–Al layered double hydroxides at the initial metal ion concentration of 100 mg/L and initial pH of 5.0. The experimental data showed a good compliance with the Langmuir isotherm and the pseudo-second-order kinetic model. Taking advantage of the combined benefits of palygorskite and Mg–Al layered double hydroxides, the as-prepared adsorbents exhibit selective and fast rating adsorption for Pb2 +.

Figure optionsDownload as PowerPoint slide