Effects of metals on the transformation of hexabromocyclododecane (HBCD) in solvents: implications for solvent-based recycling of brominated flame retardants.
The management of electronic wastes (e-wastes) has become a global issue as it may release large quantities of hazardous materials such as heavy metals and brominated flame retardants (BFRs) to the environment. Solvent-based recycling is a newly developed, efficient and environmentally beneficial technology for the removal or recovery of BFRs from e-wastes. However, little is known about the behavior of BFRs in the solvents and to what extent they may be affected by co-existing heavy metals. This study quantified the rates of transformation of hexabromocyclododecane (HBCD), a widely used BFR, in the presence of different solvents (i.e. acetone, methanol or toluene) and metals (i.e. Ni, Cu, Zn, Fe or Al). Our experimental results showed that less than 20% of HBCD was transformed in all pure solvent systems within 24h at 50 degrees C. The presence of Ni greatly increased the transformation of HBCD (45-99%) in these solvent systems, whereas other metals had little or no effect on extraction process. The kinetics study showed that transformation of HBCD in Ni-containing systems followed pseudo-first-order kinetics and that the highest transformation rate constant (1.2+/-0.1h(-1)) of HBCD was recorded in the Ni+acetone system. The formation of HBr and pentabromocyclododecene in the acetone+Ni system suggested that transformation of HBCD proceeded via dehydrobromination. Collectively, these results indicated that acetone should not be applied in the recycling or extraction of HBCD from Ni-rich e-wastes, as debromination of HBCD may occur during these processes, even at mild extraction temperatures.
Zhong
Yin
Y
Pearl River Delta Research Center of Environmental Pollution and Control, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Wushan, Guangzhou 510640, PR China.
Peng
Ping'an
P
Yu
Zhiqiang
Z
Deng
Haopeng
H
D000096:Acetone / Q000737:chemistry; D055615:Electrical Equipment and Supplies; D005411:Flame Retardants; D006842:Hydrocarbons, Brominated / Q000737:chemistry*; D007220:Industrial Waste; D007700:Kinetics; D008670:Metals / Q000737:chemistry*; D000432:Methanol / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D014050:Toluene / Q000737:chemistry; D018505:Waste Management / Q000379:methods*
D005411:Flame Retardants; D006842:Hydrocarbons, Brominated; D007220:Industrial Waste; D008670:Metals; D012997:Solvents; D000096:Acetone; D014050:Toluene; C089796:hexabromocyclododecane; D000432:Methanol