Web Release Date: March 21,
Removal of Trivalent Arsenic (As(III)) from Contaminated Water by Calcium Chloride (CaCl2)-Impregnated Rice Husk Carbon
Department of Chemical Engineering, Indian Institute of Technology (IIT) Roorkee, Roorkee-247667, Uttaranchal, India
Received for review June 2, 2006
Revised manuscript received January 13, 2007
Accepted January 26, 2007
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 
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
~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.
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