On the adsorption of Cr (VI) in water by NiCoFe ternary metal-based LDHs

Abstract

This paper prepares NO3-layer double hydroxides (LDHs) NiFe-LDHs, NiCoFe-LDHs and CoFe-LDHs by co-precipitation, studies the LDHs' adsorption of the heavy metal element Cr (VI) in water, and systematically explores the influence of the initial concentration of solution, the adsorption time and the pH value of the solution on the adsorption performance. The results indicate that the adsorption rate reaches 96.7% when the concentration of Cr (VI) solution is 2 mg/L, and reaches 30.22mg/g when the concentration of Cr (VI) solution is 10 mg/L. When the pH value of the solution is 5.5, the adsorption performance is the best, and the adsorption process can reach equilibrium in 30min. Thermodynamics and isothermal adsorption studies show that the adsorption process of Cr (VI) by NiCoFe-LDHs fits the Langmuir model and pseudo-second-order kinetics model. Thus, the adsorption process occurs on the adsorbent surface and the adsorption process is chemisorption.