Adsorption of direct violet dye by Zn/Cr and Zn/Al layered double hydroxides: Thermodynamic study

Abstract

In this study, Zn/Cr and Zn/Al layered double hydroxides have been prepared as adsorbent. The adsorbent was characterized using X-Ray Diffraction and the surface area was analyzed by BET method. The adsorption effect and influencing factors were studied. The value of dye absorbed was calculated and suggested of high efficiency to remove direct violet (DV) dye in aqueous solution. The isotherm models were examined using Freundlich and Langmuir. The results showed the Freundlich isotherm models are fitted and indicating multilayers adsorption mode. The higher adsorption capacity of Zn/Cr and Zn/Al reached at 323 K at the amount of 45.06 mg g-1 and 30.23 mg g-1, respectively. The thermodynamic study showed that the adsorption processes were spontaneous. The negative value of ΔG and endothermic found the cost of LDH positively.