Facile synthesis of Tri-metallic layered double hydroxides (NiZnAl-LDHs): Adsorption of Rhodamine-B and methyl orange from water

Abstract

In this research work, tri-metallic layered double hydroxides (NiZnAl-LDH) nano-sheets were efficiently synthesized by hydrothermal technique and applied for the decontamination of rhodamine B (Rh-B) and methyl orange (MO). Material characterizations confirm the formation of tri-metallic NiZnAl-LDH nano-sheets of continuous macrostructure skeleton with interconnected macropores. Several adsorption factors like initial concentration, pH of dyes solution, contact time and adsorbent dosage were investigated. Results exposed that synthesized NiZnAl-LDH perform best in basic medium for the removal of Rh-B and in mild acidic for that of MO. Also with 210 min contact time NiZnAl-LDH showed adsorption efficiency of 38.03 mg/g for Rh-B and 32.67 mg/g for that of MO. The Langmuir model perfectly defined the adsorption process on to the surface of NiZnAl-LDH as monolayer with relatively higher R2 value (R2 = 0.978 for Rh-B and 0.996 for MO). The maximum adsorption capacities (qmax) calculated with Langmuir model were 97.09 mg/g for Rh-B and 105.26 mg/g for MO, which are analogous with other conventional adsorbents. Furthermore, the adsorption of Rh-B and MO onto NiZnAl-LDH follow pseudo second order kinetics indicating that adsorption process is independent to that of concentration of adsorbate. Additionally, reusability experiment confirmed that the fabricated tri-metallic LDHs nano-sheets own outstanding recyclability with qe = 21.25 mg/g of Rh-B and 28.55 mg/g of MO at 4th regeneration cycle. The outcomes of this research could serve as a foundation for designing and engineering exceptional materials for purification of industrial waste water.