Arsenic Removal from Aqueous Solution by Iron Oxide-Coated Biomass: Common Ion Effects and Thermodynamic Analysis

Abstract

A batch study showed that the presence of anions (sulfate, chloride, and nitrate) in solution did not affect the adsorption process of both As(V) and As(III) by iron oxide-coated A. niger biomass. It was found that the presence of Ca²⁺, Fe²⁺, and Mg²⁺ ions at a concentration of 200 mg/L in solution could increase the removal efficiency of As(V) by 86.5%, 95.4%, and 65.8%, respectively. Similarly, the presence of Ca²⁺, Fe²⁺, and Mg²⁺ ions at a concentration of 200 mg/L in solution could increase the removal efficiency of As(III) by 39.3%, 97%, and 8.4%, respectively. The batch adsorption-desorption study showed that the reactions between the arsenic species and the iron oxide-coated A. niger biomass were reversible. Desorption of As(V) and As(III) at neutral pH was approximately 15%. As(V) desorbed more than As(III) in acidic (pH 1.33) and alkaline (pH 12.56) solutions. At a pH of 1.33, 67% of the adsorbed As(V) desorbed, and the percentage of desorbed As(III) was only 47.1% in the same condition. At a solution pH of 12.56, 73.4% of the As(V), and 43.7% of As(III) desorbed. The thermodynamic study showed the spontaneous nature of the sorption of arsenic on IOCB. The high value of the heat of adsorption {ΔH ≈ − 133 kJ/mol for As(V), and 88.9 k/mol for As(III)} indicated that the mechanism of arsenic sorption was chemisorption.

Keywords:

• Adsorption
• purification
• biosorption
• batch processing
• thermodynamics
• ion effect

ACKNOWLEDGEMENT

The study was supported by a grant from the Natural Sciences and Engineering Research Council of Canada to the second author. The authors would like to thank the reviewers for their constructive comments.

Notes

Note: ‘Ads.’ means adsorption and ‘Des.’ means desorption.

Note: ‘Ads.' means adsorption and ‘Des.' means desorption.

Note: ‘con.’ means concentration.

Note: ‘con.’ means ‘concentration’.

Note: (1) * Data not significant at 95% confidence level. All other data are significant at 95% confidence level (t-test). (2) ‘Temp.’ means ‘temperature’.