Enhanced removal of manganese from groundwater by activated carbon supported calcium ferric phosphate composites

Permeable reactive barriers (PRB) are a demonstrated technique for removing contaminants from groundwater. Investigation of PRB media is particularly important as one of the keys to successful application. Activated carbon supported calcium ferric phosphate composites (CIP-Cs) with various particle sizes were synthesized using a liquid-phase reduction and sol–gel method. The CIP-Cs exhibited developed pores with abundant oxygenous groups. In static batch experiments, the optimal experimental conditions for Mn 2+ removal were determined as a dosage of 2 g l −1 of CIP-Cs, a pH of five, an initial concentration of 5 mg l −1 and a reaction time of 240 min. Under these conditions, the adsorption capacity was found to be 2.42, 2.20 and 0.89 mg g −1 for CIPs with particle sizes of 0.15–0.35, 0.35–0.6 and 0.6–1.18 mm, respectively. Characterization techniques along with kinetic and isothermal fitting models revealed that oxygenous groups played a crucial role in Mn 2+ adsorption. The adsorption mechanism was found to be controlled by ion exchange, dissolution–precipitation, electrostatic attraction and chemical complexation. In conclusion, CIP-Cs were deemed effective media for Mn 2+ removal with significant potential applications in groundwater remediation systems, because of their high efficiency, strong ability to adapt to temperature variation and resistance to cation and anion interference.