Arsenic removal by modified activated carbons with iron hydro(oxide) nanoparticles

Different activated carbons modified with iron hydro(oxide) nanoparticles were tested for their ability to adsorb arsenic from water. Adsorption isotherms were determined at As (V) concentrations < 1 ppm, with varying pH (6, 7, 8) and temperature (25 and 35 °C). Also, competition effect of anions on the As (V) adsorption capacity was evaluated using groundwater. The surface areas of the modified activated carbons ranged from 632 m2 g−1 to 1101 m2 g−1, and their maximum arsenic adsorption capacity varied from 370 μg g−1 to 1250 μg g−1. Temperature had no significant effect on arsenic adsorption; however, arsenic adsorption decreased 32% when the solution pH increased from 6 to 8. In addition, when groundwater was used in the experiments, the arsenic adsorption considerably decreased due to the presence of competing anions (mainly SO42−, Cl− and F−) for active sites. The data from kinetic studies fitted well to the pseudo-second-order model (r2 = 0.98–0.99). The results indicated that sample CAZ-M had faster kinetics than the other two materials in the first 10 min. However, sample F400-M was only 5.5% slower than CAZ-M. The results of this study show that iron modified activated carbons are efficient adsorbents for arsenic at concentrations lower than 300 μg L−1.

► Surface area, iron content and pH of the adsorbent influence the As (V) uptake.
► As (V) adsorption capacity decreases 32% when the solution pH increases from 6 to 8.
► Temperature does not significantly affect As (V) adsorption capacity.
► SO42−, Cl− and F− compete with As (V) for active sites.
► 30–36% of As (V) is removed by modified carbon materials in the first 10 min.