The volatilization of heavy metals during combustion of polyvinyl chloride after hydrothermal carbonization

Abstract

This paper experimentally investigated the volatilization characteristic of five heavy metals (cadmium, chromium, nickel, lead and zinc) during combustion of hydrochars of polyvinyl chloride with hydrothermal carbonization pretreatment. The differences of volatilization rate of cadmium and lead between polyvinyl chloride and hydrochars were within 5%, indicating that hydrothermal carbonization had no significant effects on their volatilization behavior. Higher hydrothermal carbonization temperature and lower combustion temperature resulted in lower volatilization rate of zinc. For chromium and nickel, although their volatilization rates were lowered, the absolute volatilization rates increased remarkably because of the increase of original concentrations. Nevertheless, the total emissions of heavy metals studied reduced. Hydrothermal carbonization performed at 230 °C showed the most significant absolute volatilization rates reductions ranged from 79.2% to 86.8% depending on combustion temperature. The highest concentrations of chromium and nickel in bottom ash reached up to 20.1 g/kg and 7.9 g/kg, respectively.