TY - JOUR
T1 - New insights into the debromination mechanism of non-metallic fractions of waste printed circuit boards via alkaline-enhanced subcritical water route
AU - Chen, Ye
AU - Yang, Jiakuan
AU - Liang, Sha
AU - Hu, Jingping
AU - Hou, Huijie
AU - Liu, Bingchuan
AU - Xiao, Keke
AU - Yu, Wenbo
AU - Deng, Huali
N1 - Publisher Copyright:
© 2020
PY - 2021/2
Y1 - 2021/2
N2 - The debromination of brominated epoxy resins (BERs) from waste printed circuit boards (WPCBs) is of great challenge due to its high structural stability. An enhanced subcritical water (SCW) process with alkaline additive is proposed for efficient debromination of BERs, and the mechanism of alkaline additive on bromine removal has been investigated. More than 95.11% of bromine is removed under the optimal conditions. Both enhanced fiberglass destruction and BERs degradation contribute to the efficient debromination process. Structure of Ca−Al, Si−O, and Al−O bonds in fiberglass is destroyed by alkaline corrosion, releasing BERs into the solution and facilitating the debromination process. Meanwhile, phenol, 2-bromophenol and catechol are the main products of BERs degradation. Nucleophilic substitution reaction by the bimolecular process dominantly contribute to the debromination. The energy barrier of the bimolecular process is only 15.9 kcal/mol, which is much lower than that of the direct dissociation energy of C−Br bond (168.3 kcal/mol). Ion association of KOH is weaker than that of NaOH in the alkaline-enhanced SCW process due to the difference of cation radius, proved by ab initio molecular dynamics simulation. An efficient approach for WPCBs debromination under mild conditions has been proposed.
AB - The debromination of brominated epoxy resins (BERs) from waste printed circuit boards (WPCBs) is of great challenge due to its high structural stability. An enhanced subcritical water (SCW) process with alkaline additive is proposed for efficient debromination of BERs, and the mechanism of alkaline additive on bromine removal has been investigated. More than 95.11% of bromine is removed under the optimal conditions. Both enhanced fiberglass destruction and BERs degradation contribute to the efficient debromination process. Structure of Ca−Al, Si−O, and Al−O bonds in fiberglass is destroyed by alkaline corrosion, releasing BERs into the solution and facilitating the debromination process. Meanwhile, phenol, 2-bromophenol and catechol are the main products of BERs degradation. Nucleophilic substitution reaction by the bimolecular process dominantly contribute to the debromination. The energy barrier of the bimolecular process is only 15.9 kcal/mol, which is much lower than that of the direct dissociation energy of C−Br bond (168.3 kcal/mol). Ion association of KOH is weaker than that of NaOH in the alkaline-enhanced SCW process due to the difference of cation radius, proved by ab initio molecular dynamics simulation. An efficient approach for WPCBs debromination under mild conditions has been proposed.
KW - Alkaline additives
KW - Brominated epoxy resins
KW - Debromination
KW - Subcritical water
KW - Waste printed circuit boards
UR - http://www.scopus.com/inward/record.url?scp=85094191155&partnerID=8YFLogxK
U2 - 10.1016/j.resconrec.2020.105227
DO - 10.1016/j.resconrec.2020.105227
M3 - 文章
AN - SCOPUS:85094191155
SN - 0921-3449
VL - 165
JO - Resources, Conservation and Recycling
JF - Resources, Conservation and Recycling
M1 - 105227
ER -