Sorption of Cd2+ on Bone Chars with or without Hydrogen Peroxide Treatment under Various Pyrolysis Temperatures: Comparison of Mechanisms and Performance

Abstract

In this study, bone char pretreated with hydrogen peroxide and traditional pyrolysis was applied to remove Cd²⁺ from aqueous solutions. After hydrogen peroxide pretreatment, the organic matter content of the bone char significantly decreased, while the surface area, the negative charge and the number of oxygen-containing functional groups on the bone char surface increased. After being pyrolyzed, the specific surface area and the negative charge of the material were further improved. The adsorption kinetics and isotherms of Cd²⁺ adsorption were studied, and the influence of solution pH and the presence of ionic species were investigated. The experimental results showed that the samples with lower crystallinity exhibited less organic matter content and more surface oxygen-containing functional groups, resulting in stronger adsorption capacity. After being treated with hydrogen peroxide and pyrolyzed at 300 °C, the maximum adsorption capacity of bone char was 228.73 mg/g. The bone char sample with the lowest adsorption capacity(47.71 mg/g) was pyrolyzed at 900 °C without hydrogen peroxide pretreatment. Ion exchange, surface complexation, and electrostatic interactions were responsible for the elimination of Cd²⁺ by the bone char samples. Overall, this work indicates that hydrogen peroxide-treated pyrolytic bone char is a promising material for the immobilization of Cd²⁺.