Kinetics, isothermal and mechanistic insight into the adsorption of eosin yellow and malachite green from water via tri-metallic layered double hydroxide nanosheets

The use of highly efficient, environment-friendly and economically inexpensive materials for the adsorption removal of contaminants from water has always been considered as emerging task. In this study, we synthesized hybrid tri-metallic nickel cobalt layered double hydroxide (NiCoAl-LDH) porous material for the adsorption removal of Eosin yellow (EY) and Malachite green (MG) from water. The characterization results disclosed that tri-metallic LDH has been synthesized with extraordinary purity, identical morphology and high surface area (134.21 m 2 ·g −1 ). The NiCoAl-LDH performs the best for adsorption of EY (q e =37.30mg·g −1 at pH=2) and MG (q e =39.61 mg·g −1 at pH=10). The Langmuir and Freundlich isotherm models were applied to explain the adsorption process of dyes on the surface of LDH. The Langmuir model (R 2 =0.991 and 0.999 for Eosin Y and Malachite G, respectively) was very appropriate to explain the process of adsorption on NiCoAl-LDH as homogeneous (monolayer). The maximum adsorption capacity of EY and MG calculated with Langmuir model was 78.74 and 110.13 mg·g −1 at 30 °C, respectively. Also with 240 minutes contact time 94.8% EY and 89.9% MG was adsorbed by as synthesized NiCoAl-LDH nanosheets. The NiCoAl-LDH nanosheets showed excellent performance of reusability of up to five regeneration cycles. The results showed that the adsorption capacity of NiCoAl-LDH nanosheets after five regeneration cycles, to adsorb EY, decreased only from 40.80 to 36.93 mg·g −1 and that of MG from 79.21 to 75.42 mg·g −1 , which is acceptable. The overall results Suggest that the fabricated NiCoAl-LDH is favorable for the purification of dye contaminated water.