Kinetics of uptake of Fe(II) from aqueous solutions by Co/Mo layered double hydroxide (Part 2)

The kinetics of the Fe(II) uptake by Co/Mo layered double hydroxide (Co/Mo-LDH) intercalated with carbonate (CO3)(2-) as an interlayer anion was studied. The results revealed that the maximum adsorption capacities were 29.5, 59.1, and 77.9mg/g when the initial ferrous ion concentration was 25mg/l at 298, 308, and 318K, respectively. These results displayed a high efficiency of the Fe(II) uptake from aqueous solution at higher temperature. The adsorption isotherms were seen to be consistent with Langmuir's adsorption isotherm. The equilibrium adsorption contact time was determined for Co/Mo-LDH. This suggested that the pseudo-first-order equation might not be sufficient to depict the kinetics of Fe(II) onto the Co/Mo-LDH, and the kinetics of adsorption of Fe(II) onto Co/Mo-LDH were best described by the pseudo-second-order model. Also, the paper discussed the thermodynamic parameters of the adsorption (Gibbs free energy, entropy, and enthalpy). Our results demonstrated that the adsorption process was spontaneous and endothermic. The synthesized Co/Mo-LDH product could act as a highly-effective nano-adsorbent of Fe(II) removal from the aqueous solutions.