模拟电子垃圾热回收处理过程,将丙烯腈-丁二烯-苯乙烯塑料(ABS)、四溴双酚A(TBBPA)分别与4种金属(Cu、Fe、Zn和Ni)进行混合,在自制的加热装置内开展了不同气氛、不同温度条件下热解实验研究。对产物溴代二噁英(PBDD/Fs)检测显示,2,3,7,8-TBDF、2,3,7,8-TBDD及1,2,3,4,7,8-与1,2,3,6,7,8-Hx BDD为主要产物,其中2,3,7,8-TBDF含量最高,约占总PBDD/Fs的12%~90%。反应生成的8种2,3,7,8-PBDD/Fs浓度范围为0.05~2 082 ng·g-1。在同等实验条件下,温度升高有利于ABS塑料混合物中PBDD/Fs的生成。Cu、Fe、Zn和Ni四种金属都具有催化效应。空气、氮气气氛下热解实验显示,空气气氛下PBDD/Fs的生成量大,2种条件下生成的二噁英总量比值在0.8~99.6之间变化。无金属催化条件下此比值变化范围较小,为0.8~1.5;在金属参与条件下,此比值变化范围加大,为1.2~99.6;其中,在Cu和Fe参与下,此比值较高。各种热解条件下形成的PBDD/Fs都具有PBDFs〉PBDDs的特征。研究结果说明,虽然无金属参与条件下含TBBPA的ABS热解生成溴代二噁英浓度较低,但金属(如Cu等)存在时,此类污染物的浓度显著增加。
The formation of polybrominated dibenzo-p-dioxins(PBDDs) and dibenzofurans(PBDFs) during the py-rolysis of acrylonitrile-butadiene-styrene(ABS) and tetrabromobisphenol A(TBBPA) blends containing or not one of the four metals(Cu, Fe, Zn and Ni) was investigated using a self-made apparatus at different temperatures and carrier gas compositions. Results showed that 2,3,7,8-TBDF, 2,3,7,8-TBDD, 1,2,3,4,7,8-Hx BDD and 1,2,3,6,7,8-Hx BDD were the main products, and that the highest concentration congener was 2,3,7,8-TBDF, accounting for 12% ~ 90%of total concentration of the products. The total concentration of 2,3,7,8-PBDD/Fs ranged from 0.05 to 2 082 ng·g-1.Under the same conditions, high temperatures favored the formation of PBDD/Fs during the pyrolysis. The four metals were found to have a catalytic effect on the formation of PBDD/Fs. Higher concentration of PBDD/Fs was detected when air was used as carrier gas, and the ratios of ∑PBDD/Fs to the total concentration of the products under the two gas conditions(with air and N2 as carrier gas, respectively) ranged from 0.8 to 99.6. In the absence of the metals, the ratios of ∑PBDD/Fs to the total concentration of the products showed little variation(ranging from0.8 to 1.5); while, in the presence of the metals, the ratios varied greatly from 1.2 to 99.6. Under the experimental conditions of the present study, the concentrations of PBDFs formed during the pyrolysis were much higher than those of PBDDs. The metals such as Cu could increase the formation of PBDD/Fs during the pyrolysis of ABS/TBBPA blends, although the levels of PBDD/Fs formed in the absence of the metals during the pyrolysis were relatively low.