Mercury removal from solid waste by oxygen plasma and thermal processes

Abstract

Mercury and its compounds are very dangerous to environmental and human health. Methods to contain and/or limit its emission through the filters, gas cleaning systems, and alternative processes for purification of industrial residues are necessary. This study focused on mercury removal from diatomite sorbent samples–used as a filter in chemical industries–using an oxygen low-pressure hollow cathode discharge (HCD). The effects of the exposure time and temperature were investigated. Thermal desorption (at 500 and 650 °C) and plasma oxidation were performed at low pressures (between 36 and 80 Pa). The results show a considerable acceleration of the diatomite decontamination to a temperature of 650 °C, bringing the concentration of mercury below 100 µg/kg after 10 min and 39 µg/kg after 110 min of HCD exposure time. A comparative analysis of the virgin diatomite characteristics used in the filter press and after treatment show the possibility of recycling this material. Additionally, the mercury extracted by condensation in the vacuum line (by using a dry ice trap) can be purified for reuse and returned to the industrial process.