Preparation and characterization of calcined Ni/Mo hydrotalcite for the effective removal of lead from wastewater

Abstract

ABSTRACT In this investigation, calcined Ni/Mo hydrotalcite was prepared via co-precipitation method and used as a sorbent for efficient removal of lead from aqueous solutions. The Pb2+ removal efficiency reached 99% at pH 6 and a sorbent dose of 2 g/L. The equilibrium data were satisfactorily fitted by the Langmuir and Hill models with a maximum capacity of 196.87 mg/g, indicating the monolayer sorption for lead over calcined Ni/Mo hydrotalcite. The Pb2+ sorption kinetic follows a pseudo-second-order reaction due to high correlation coefficients (R 2 > 0.99), while the Boyd’s plots confirm the external mass transfer as the rate-limiting step in the Pb2+ sorption. The temperature effect indicated a spontaneous and exothermic Pb2+ uptake. Mechanisms involved in the removal process include surface precipitation, diffusion into the solid pores and isomorphic substitution with Ni2+ of the sheets. The results showed excellent selectivity for Pb2+ removal from multi-divalent cation solutions and good reusability of the sorbent for up to 10 consecutive sorption–regeneration cycles without significant loss of the removal efficiency. As an application, the treatment of wastewater containing Pb2+, generated from the battery industry has been undertaken. The Pb2+ concentration was reduced from 5.7 to 0.6 mg/L, corresponding to an abatement of 89.5%. Therefore, the sorption using calcined Ni/Mo hydrotalcite is an efficient and suitable method for the elimination of Pb2+.