Facile one-pot synthesis of nano-zinc hydroxide by electro-dissolution of zinc as a sacrificial anode and the application for adsorption of Th4+, U4+, and Ce4+ from aqueous solution

Facilely synthesized zinc hydroxide nanoparticles by electro-dissolution of zinc sacrificial anodes were investigated for the adsorption of thorium (Th 4+ ), uranium (U 4+ ) and cerium (Ce 4+ ) from aqueous solution. Various operating parameters such as effect of pH, current density, temperature, electrode configuration, and electrode spacing on the adsorption efficiency of Th 4+ , U 4+ and Ce 4+ were studied. The results showed that the maximum removal efficiency was achieved for Th 4+ , U 4+ and Ce 4+ with zinc as anode and stainless steel as cathode at a current density of 0.2 A/dm 2 and pH of 7.0. First- and second-order rate equations were applied to study the adsorption kinetics. The adsorption process follows second order kinetics model with good correlation. The Langmuir, Freundlich adsorption models were applied to describe the equilibrium isotherms and the isotherm constants were determined. The experimental adsorption data were fitted to the Langmuir adsorption model. Thermodynamic parameters such as free energy (Δ G° ), enthalpy (Δ H° ), and entropy changes (Δ S °) for the adsorption of Th 4+ , U 4+ and Ce 4+ were computed to predict the nature of adsorption process. Temperature studies showed that the adsorption was endothermic and spontaneous in nature.