Batch and column study: adsorption of Mo(VI) from aqueous solutions using FeCl2-modified fly ash

Removal of Mo(VI) by adsorption on fly ash modified by FeCl2 was investigated in the present study. Various parameters such as pH, agitation time, Mo(VI) concentration, and temperature had been studied in the batch study to evaluate the effectiveness of modified fly ash for Mo(VI) removal from water. Batch study revealed that the uptake of Mo(VI) was effective in the pH range of 4.0–6.0. Kinetic studies showed that the adsorption generally obeyed the pseudo-second-order model. The isotherm data were fitted well in the Langmuir isotherm model, and adsorption capacity was found to be 17.83 mg g−1. Subsequently, thermodynamic parameters such as ΔH 0, ΔS 0, and ΔG 0 for the adsorption were also evaluated, which showed that the adsorption of Mo(VI) on treated fly ash were endothermic, entropy increasing, and spontaneous. Continuous column study using a series of fixed bed was also carried out. The bed depth service time model was suitable for predicting breakthrough curve for Mo(VI) adsorption column study. In conclusion, the FeCl2-modified fly ash was proven to be a feasible and cost-efficient treatment technology for Mo(VI) removal.