Removal of trivalent arsenic (As(III)) from contaminated water by calcium chloride (CaCl2)-impregnated rice husk carbon

This paper deals with the arsenic removal ability of activated carbons produced from calcium chloride (CaCl2)-impregnated rice husks (RH). The optimum concentration of Ca2+ ions in calcium chloride solution (CCS) for impregnation was determined to be 2%, which produced ARHC((Ca-2.0)). The maximum specific uptake (18.2 +/- 0.05 mu g/g) was obtained using ARHC((Ca-2.0)) at an initial arsenic concentration of 1000 ppb. It was observed that the percentage removal and specific uptake of trivalent arsenic (As(III)) by ARHC((Ca-2.0)) were similar to 480% and similar to 550% higher than that of activated rice husk carbon without impregnation (ARHC((Ca-0))), for an arsenic solution with an initial concentration of 100 ppb. However, using ARHC((Ca-2.0)) as an adsorbent, when the initial arsenic concentration was increased from 100 ppb to 1000 ppb, the specific uptake was increased by similar to 769% and the percentage removal was decreased by similar to 13%. The spent adsorbent gave similar to 80% desorption of the adsorbed As(III) in 5 N H2SO4. The fitness of the isotherm equations used to explain the adsorption phenomena decreased in the following order: polynomial isotherm > Freundlich isotherm > Langmuir isotherm.