Key factors for optimum performance in phosphate removal from contaminated water by a Fe-Mg-La tri-metal composite...

Eutrophication is typically due to excessive discharge of phosphate-containing wastewater into natural waters. In this study, a novel Fe-Mg-La trimetal composite sorbent with a Fe:Mg:La molar ratio of 2:1:1 was developed through a cost-effective co-precipitation approach for phosphate removal in contaminated water. It was found that the adsorption was greatly affected by solution pH. The experimental data was better described by Langmuir isotherm model, and the maximum adsorption capacity of 415.2 mg-P/g was achieved under pH 6.0, much higher than most of sorbents previously reported. Nitrate, sulfate, bicarbonate, fluoride and humic acid widely exist in natural water, and their presences would slightly retard the adsorption of phosphate. The adsorption kinetics experiment showed that most of adsorption occurred in the first 1h and the adsorption equilibrium was achieved in 10h; the adsorption history was well described by the intraparticle diffusion model. The performance of sorbent was further confirmed by treating phosphate contaminated lake water. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis indicated that hydroxyl group on the sorbent surface (M-OH) played the most key role in the phosphate adsorption. The presence of sulfate group was important in the uptake as well.