Kinetics and isotherm studies for the adsorptive removal of Reactive Red-141 dye from aqueous solution by uncalcined and calcined zinc aluminium carbonate layered double hydroxide- A comparative study

Abstract

The feasibility of the removal of Reactive Red -141 (RR-141) by two different adsorbent materials namely zinc aluminium carbonate layered double hydroxide (ZAC-LDH) and calcined LDH (CZA-LDH) from aqueous solution has been investigated. To investigate the adsorption capacities of the adsorbent, batch mode adsorption studies has been performed for the removal of RR-141 using different parameters such as initial dye concentration, adsorbent dosage, contact time, temperature and <em>p</em>H. The various adsorption kinetic studies such as pseudo first order, pseudo second order and intra particle diffusion models are performed. The pseudo-second-order kinetic model is fitted well with high correlation coefficient. The optimum <em>p</em>H for maximum dye removal is found to be highly acidic (i.e., <em>p</em>H 2). Both Langmuir and Freundlich isotherm models described the adsorption mechanism of dye by both the adsorbents. The FESEM images and XRD pattern confirmed that the adsorption and intercalation of RR-141 dye molecule onto the adsorbents. The thermodynamic parameters like ΔGº, ΔHº and ΔSº have also been calculated. Regeneration of calcined and its reusability has also been performed for the removal of RR-141. The results suggest that the efficiency of CZA-LDH is found to be good enough to remove RR-141 comparatively with the uncalcined LDH sample ZAC-LDH from aqueous solution.