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 (CaCl 2 )impregnated rice husks (RH). The optimum concentration of Ca 2+ 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 H 2 SO 4. The fitness of the isotherm equations used to explain the adsorption phenomena decreased in the following order: polynomial isotherm > Freundlich isotherm > Langmuir isotherm.

Biosorptive Performance of Bacillus arsenicus MTCC 4380 Biofilm Supported on Sawdust/MnFe2O4 Composite for the Removal of As(III) and As(V)

“…Loading of MnFe 2 O 4 increased the positive charge density on the biosorbent surface by neutralizing negative surface charge and creating positive charge in its place [24]. Mondal et al reported that impregnation of Ca on the surface of GAC also increased the positive charge on the surface of GAC and finally improved the adsorption capacity of GAC [25,26]. By comparing the arsenic adsorption capacity of MnFe 2 O 4 with and without the template in Table 4, it was observed that the adsorption capacities of MnFe 2 O 4 loading on the acid-treated sawdust are much higher than the bare ones.…”

Waste Treatment and Remediation Technologies for Arsenic

“…After charring the source materials to remove volatiles, the resulting carbon is usually 'activated' with heat and chemicals (such as acids, bases, steam, or metal salts; (Mohan and Pittman, 2007)) to increase its surface area and improve sorption. Although activated carbon will sorb a wide variety of organic and inorganic contaminants from water, the pure compound is generally ineffective in removing As(III) (Dambies, 2004, 608;Mondal, Majumder and Mohanty, 2007). Depending upon the composition and surface area of the activated carbon and the chemistry of the water, the carbon may (Mokashi and Paknikar, 2002) or may not (Daus, Wennrich and Weiss, 2004) extensively remove As(V) from water.…”

“…As an alternative, GAC may be impregnated with iron and other materials and then placed into permeable treatment columns. Impregnating activated carbon with inorganic materials, such as calcium chloride (CaCl 2 ) or iron, copper, or zirconium salts, can greatly improve the sorption of As(III) and/or As(V) (US EPA, 2002b, 25;(Rajaković, 1992;Mohan and Pittman, 2007;Mondal, Majumder and Mohanty, 2007;Zhang et al, 2007c;Schmidt et al, 2008). The addition of polyanilines ((C 6 H 7 N 4 ) n ) or other organic compounds to activated carbon may also substantially enhance the sorption of As(V) (Yang, Wu and Chen, 2007; Table 7.1).…”

Treatment of Arsenic Contaminated Groundwater Using Calcium Impregnated Granular Activated Carbon in a Batch Reactor: Optimization of Process Parameters

“…Impregnation of Ca 2+ on rice husk carbon (RHC-Ca) considerably increases the arsenic removal capacity of RHC [14]. Impregnation of divalent Ca 2+ ions increases the positive charge density on the adsorbent surface by neutralizing one negative surface charge and creating one positive charge in its place [14].…”

“…Impregnation of divalent Ca 2+ ions increases the positive charge density on the adsorbent surface by neutralizing one negative surface charge and creating one positive charge in its place [14]. Impregnation of Ca 2+ ion on the surface of GAC, which is predominantly negatively charged at neutral pH [23], may increase the positive charge density on the GAC-Ca surface.…”