Removal of gaseous Hg0 by Cl-loaded carbonaceous material prepared from rice husk

Abstract

The main objective of this study was to investigate the removal of gaseous Hg⁰ from the residue obtained during the chlorination of rice husk char to recover silica. First, the chlorine content, chlorine form, pore size, and chlorination reaction of the chlorination residue of rice husk char were investigated. Subsequently, the adsorption performance of gaseous Hg⁰ and adsorption form of Hg⁰ were examined. Through the chlorination of rice husk char (RC) at 1000 °C for 10 min, silicon (Si) in the char could be separated and recovered, and carbonaceous material doped with 9.0% Cl could be prepared. The temperature-programmed desorption (TPD) analysis of the char before and after chlorination revealed that the oxygen-containing functional groups on the surface of char were part of the Cl adsorption sites. Additionally, the X-ray photoelectron spectroscopy (XPS) analysis showed that Cl was mainly present in the C–Cl bonds of the chlorination residue (RCC). The effect of temperature on the performance was small in the tested range (40–160 °C). The adsorption performance of the prepared RCC was superior to those of chlorine- and sulfur-loaded carbons, as reported in previous studies. The results of TPD analysis after the adsorption tests indicated that the adsorption form of Hg⁰ was mainly HgCl₂.