The volatile organic compounds emission mechanism of pretreated bamboo during heat treatment

Heat treatment can be used to improve bamboo product quality. Pretreatment of the bamboo material can reduce the energy consumption of heat treatment. However, large quantities of volatile organic compounds (VOCs) are released during the bamboo heat treatment process, causing potential problems for the environment and human health. In this study, the effects of pretreatment with sodium hydroxide and zinc chloride solutions on VOCs emissions during heat treatment were investigated. We also explored chemical and structural changes of heat-treated bamboo. The VOCs released by untreated bamboo during heat treatment were mainly aldehydes, alcohols, alkanes, and esters. Alcohol and alkane contents decreased as treatment temperature increased, accompanying the emergence of more complex chemicals. Compared with untreated bamboo, sodium hydroxide pretreatment destroyed the hemicellulose structure, released stable VOCs under heat treatment, and did not produce acidic compounds; ether compounds increased significantly with increase in temperature. The catalysis of zinc chloride pretreatment degraded hemicellulose during heat treatment. The relative contents of aldehydes and esters released from zinc chloride pretreated bamboo during heat treatment increased significantly with temperature. Up to 69.76 % of aldehyde compounds were released at 160 °C, among which the relative proportion of furfural reached 37.23 %. These results may provide theoretical support for controlling VOCs emissions from different pretreated bamboo materials during heat treatment, which is also conducive to the subsequent recycling of VOCs.