A novel safety treatment strategy of DEHP-rich flexible polyvinyl chloride waste through low-temperature critical aqueous ammonia treatment.

Flexible polyvinyl chloride (f-PVC) contains high content of plasticizers and chlorine. Improper treatment of waste f-PVC can easily lead to resource wasting and bring environmental risks. In this work, a novel strategy for resource recycling and dechlorination of waste f-PVC containing high content of di-(2-ethylhexyl) phthalate (DEHP) was developed by using low-temperature critical aqueous ammonia (LCA) process. The LCA treatment of waste DEHP-rich f-PVC (WDP) was performed at the temperature range of 200-400 °C with the ammonia concentration of 1%-5%. The results indicated that the LCA temperature had a significant effect on the chemical composition of decomposition products. High concentration of 2-ethyl-1-hexanol (86.12%), which is an important chemical feedstock and is derived from the decomposition of DEHP, could be obtained from WDP by the LCA process at 250 °C, and the concentration of 2-ethyl-1-hexanol decreased markedly with increasing the temperature. Benzaldehyde and acetophenone were generated when the temperature increased to 300 °C, and their concentrations increased with the rise of temperature. The increase of the ammonia concentration and the temperature could enhance the dechlorination efficiency of WDP. The dechlorination could reach 98.7% at 300 °C. This result showed that the LCA process was a promising and high-efficiency strategy for the sustainable management of WDP.