Mechanochemical declorination of hexachlorocyclohexane isomers by planetary ball mill in the presence of metal oxides

Abstract

Although the use of hexachlorocyclohexane (HCH, C6H6C16) is currently prohibited, the remaining production stocks of HCH are still present. Recent investigations have shown that mechanochemical dechlorination is a promising method to degrade HCH. However, the mechanochemical dechlorination method still needs further investigations. For this reason, in this study, mechanochemical dechlorination of HCH isomers were investigated for the first time by using coal fly ash (FA) and refractory brick waste (RB) which contain various metal oxides. The mechanochemical dechlorination process was carried out at room temperature using a planetary ball mill and the gas chromatograph with electron capture detector (GC-ECD) was used to determine the degradation efficiency. The results show that HCH isomers can be completely destroyed after 600 min grinding time in a mixture with a HCH/FA ratio of 1:20 (m/m). The conversion rate of chlorine to water soluble chlorine is 52%. At the end of the process, the ball temperatures increased up to 105 degrees C and the mixture temperatures of reagent + HCH were continuously increased with the process time. Tetrachlorobenzenes (TeCBz) and trichlorobenzenes (TCBz) are the isomers detected during the dechlorination. Based on this study, mechanochemical dechlorination of HCH isomers is a eco-friendly technology alternative to thermal treatment and biotic degradation applications.