Arsenic(V) removal with a Ce(IV)-doped iron oxide adsorbent

The removal of arsenic(V) by a new Ce–Fe adsorbent was evaluated under various conditions. Under an initial As(V) of 1.0 mg l−1, the adsorption capacity of the Ce–Fe absorbent was constant around a value of 16 mg g−1 over a wide pH range (3–7), while a maximum adsorption capacity of 8.3 mg g−1 was obtained over a narrow pH range around 5.5 for activated alumina, a conventional adsorbent. Kinetics of adsorption obeys a pseudo-first-order rate equation with the rate constant Kad as 1.84×10−3 min−1. The pattern of adsorption of As(V) by the adsorbent fitted well both the Langmuir and Freundlich models. A Langmuir Q0 of 70.4 mg g−1 was obtained at an initial pH of 5.0 and temperature of 20 °C, significantly higher than those of other adsorbents reported. Phosphate seriously inhibited the removal of As(V) while fluoride did not compete with As(V) even at an F/As molar ratio as high as 30, suggesting that the adsorption sites for As(V) and fluoride were different. Salinity, hardness, and other inorganic anions such as Cl−, NO3−, and SO42− had no apparent effect on As(V) adsorption. Fourier transform infrared spectra of Ce–Fe adsorbent before and after As(V) adsorption demonstrated that M–OH groups plays an important role for As(V) ions removal in the adsorption mechanisms of Ce–Fe adsorbent.