Enhanced arsenate removal by novel Fe–La composite (hydr)oxides synthesized via coprecipitation

Arsenic exists ubiquitously in the environment and has been proved to be of great harm to human health. In this study, a series of Fe–La composite (hydr)oxides were synthesized via a facile coprecipitation for effective As(V) removal from aqueous solution. A variety of techniques including BET surface area measurement, powder XRD, SEM, and XPS were employed to characterize the synthetic Fe–La composite (hydr)oxides. Fe–La composite (hydr)oxides grains were formed via aggregation of primary nanoparticles. With an increase in La content, the specific surface area of Fe–La composite (hydr)oxides decreased, but the pore diameter, the pore volume and the grain size of Fe–La composite (hydr)oxides increased gradually. Rapid As(V) adsorption on the synthesized composite oxides was achieved and the adsorption was well fitted by the pseudo-second-order equation. The adsorption isotherms could be well described by Langmuir equation and the maximal adsorption capacity of Fe–La composite (hydr)oxides can reach 368 mg/g. The As(V) removal was pH-dependent and decreased with an increase in pH value, especially in alkaline condition. Under acidic and neutral conditions, As(V) removal was mainly achieved by both precipitation and adsorption. By contrast, adsorption is the only mechanism for As(V) removal in alkaline condition. The results indicate that the Fe–La composite (hydr)oxides could be potentially attractive adsorbents for As(V) removal.