Mn(II) removal from aqueous solutions by Co/Mo layered double hydroxide: Kinetics and thermodynamics

Abstract

This paper deals with the experimental investigation related to the Mn(II) removal from aqueous solutions by the adsorption onto a synthesized Co/Mo layered double hydroxide (Co/Mo-LDH). The adsorption behavior was studied as a function of initial Mn(II) concentration (40–145 mg/L), contact time (15–90 min), solution pH (2–9) and adsorbent mass (0.05–0.35 g per 1.0 L). All adsorption processes were rapidly carried out at different temperatures (298, 308 and 318 K) and constant stirring rate 160 rpm. The results showed that the Co/Mo-LDH is a very promising material for removing of Mn(II) from the aqueous solutions. Particularly, the solution pH range of 4–7 has the most significant effect on the adsorption capacity. The results revealed that the maximum adsorption capacities were 20.2, 26.75 and 38.1 mg/g from the initial Mn(II) concentration (145 mg/L) at pH 5, adsorbent mass (0.2 g/1.0 L), and contact time (60 min) at different temperatures, 298, 308 and 318 K, respectively. The adsorption kinetics data are well fitted by the pseudo-second-order model, while the adsorption isotherms data were better fitted by the Langmuir equation. Also, this paper discusses the thermodynamic parameters of the adsorption and the results demonstrate that the adsorption process is spontaneous and endothermic.