Arsenic Adsorption by Activated Carbon with Different Amounts of Basic Sites under Different Solution pH and Coexistent Ions

Abstract

The bamboo-based and bead-shaped activated carbon (BAC) were used to examine the effects of textural properties and surface chemistry, respectively, on As(V) adsorption. The relationships between solution pH, coexistent ions and/or arsenic species and As(V) adsorption by BAC were also investigated. The Langmuir and pseudo-second order kinetics models were employed to evaluate the prepared activated carbon for As(V) adsorption. The results showed that As(V) adsorption was strongly attributed to surface properties, that is, basic sites rather than textural properties. The fittings of adsorption data to the kinetics models revealed that As(V) adsorption would be governed by diffusion process rather than collision process. Among various acidity regulators (HCl, HNO₃, and H₂SO₄), the pH adjustment by HCl induced the highest adsorption amount at pH 5.5, indicating that the inhibition effect of Cl⁻ ion for As(V) adsorption was much less than and ions. The effective arsenic species for As(V) adsorption was , and the decrease in the adsorption amount in acidic condition would be due to the inhibition by excess of Cl⁻ ion, while the decrease in the adsorption at pH more than 5.5 would be attributed to the increase in OH⁻ ion or to the influence of increased hydrogen arsenate species ().

Keywords:

• activated carbon
• arsenic adsorption
• arsenic species
• basic site
• coexistent anion
• solution pH

ACKNOWLEDGEMENTS

The authors wish to express gratitude to Prof. Dr. Masami Aikawa of Kisarazu National College of Technology for his fruitful discussion. Gratitude is also extended to Prof. Dr. Keiichi Nagao, Ex-Head of Safety and Health Organization, Chiba University, for his encouragement and support on this work.