Kinetics, thermodynamics and isotherm modeling for removal of nitrate from liquids by facile one-pot electrosynthesized nano zinc hydroxide

- Nitrate was removed efficiently by in situ prepared zinc hydroxide.
- Maximum adsorption efficiency was achieved.
- Adsorption equilibrium follows pseudo-second-order model.
- Equilibrium data were well described by the typical Langmuir adsorption isotherm.
- Thermodynamic studies revealed that the adsorption reaction was spontaneous.

This study deals with the removal of nitrate from water by electrocoagulation process using zinc and stainless steel as anode and cathode respectively. The optimizations of various experimental operating parameters like effect of electrolyte pH, current density, temperature, and inter-electrode distance on the removal of nitrate were carried out. The effect of co-existing anions such as carbonate, phosphate, silicate and phosphate was studied on the removal efficiency of nitrate. The results showed that the optimum removal efficiency of 69% was achieved. The maximum removal efficiency was achieved at a current density of 0.1 A dm− 2 and pH of 7.0. First and second-order rate equations were applied to study adsorption kinetics and the adsorption process follows second order kinetics model with good correlation. The Langmuir adsorption isotherm favors monolayer coverage of adsorbed molecules for adsorption nitrate. Thermodynamic parameters, including the Gibbs free energy, enthalpy, and entropy, indicated that the adsorption of nitrate on zinc hydroxide was feasible, spontaneous and endothermic.