Distribution of iron in activated carbon composites: assessment of arsenic removal behavior

The main objectives of this study were to evaluate the effectiveness of using iron impregnated granular activated carbon (AC) to remove arsenic from water and to assess the partitioning behavior of arsenic under a variety of conditions. Iron impregnated granular activated carbon (AC-Fe) composites were prepared with different ferric (Fe⁺³) concentrations, ranging from 0.09 to 3.0 M. These AC-Fe composites were able to remove 92–98% of the arsenate [As(V)] and 42–65% of the arsenite [As(III)]. The composite containing the lowest iron concentration (1.54%) was the most effective at arsenic sorption. Langmuir model fit indicated that the maximum 125 mg As(V)/gFe and 98.4 mg As(III)/gFe can be sorbed by the composite. The kinetics of arsenic sorption is well explained by pseudo first-order kinetics. The arsenate removal efficiency was found to decrease with increasing solution pH, while the As(III) removal efficiency was found to increase. The background ionic strength (IS) had no significant effect of on As(V) removal, but As(III) removal increased when the IS was greater than 50 mM NaCl. Our results indicate that a small amount of iron embedded efficiently in AC may have considerable potential in removing arsenic from water.