Removal of Trivalent Arsenic (As(III)) from Contaminated Water by Calcium Chloride (CaCl₂)-Impregnated Rice Husk Carbon

Abstract

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 μg/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 ∼480% and ∼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 ∼769% and the percentage removal was decreased by ∼13%. The spent adsorbent gave ∼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.