Efficient low-temperature debromination and high selectivity products recovery from brominated epoxy resin waste by subcritical water-urea treatment

In this study, a subcritical water-urea (SubCW-urea) process was developed for the treatment of brominated epoxy resin powder (BRP) waste. The SubCW-urea process had two significant advantages: efficient low-temperature debromination and highly selective products recovery. The NH3 and CO2 released from urea in the SubCW medium had a prominent enhancement effect on the decomposition and debromination of BRP waste when the SubCW temperature was below 300 degrees C. The debromination efficiency of SubCW-urea treatment was significantly enhanced in comparison with that of SubCW-NH3 and single SubCW treatments. The debromination efficiency of BRP could reach 38.21%, 85.3%, and 99.92% at 200 degrees C, 250 degrees C, and 300 degrees C, respectively. The debromination rate constant of BRP in SubCW-urea, SubCW-NH3, and single SubCW system was 0.1363, 0.1254, and 0.0146 min(-1), respectively. No brominated chemical compound could be detected in the oil phase products when the treatment temperature was higher than 250 degrees C. The decomposition products of BRP waste could be easily regulated by controlling the treatment temperature of SubCW-urea. 2-bromo-phenol with the purity of 72.5% could be selectively prepared from BRP by SubCW-urea process at 200 degrees C. The purity of the recovered phenol could reach as high as 81.5% at 250 degrees C. The selectivity of the products decreased greatly at 300 degrees C due to the secondary reactions. The SubCW-urea process has an application prospect in the safe treatment of BRP waste with the aim of high-efficiency debromination and high selectivity products recovery at low temperature. (C) 2020 Elsevier Ltd. All rights reserved.