Experimental Study On Debromination Of Waste Printed Circuit Board

As one kind of the waste electrical and electronic equipments, the harmless treatment of waste print circuit board (PCB) becomes much more important. Pyrolysis is thought to be a promising alternative to recycle material and energy of waste waste print circuit board. Pyrolysis technique plays a import role in the aspects of reducing the volume of the waste PCB, improving the recovery efficiency of metals, the organic chemical materials from the bromine epoxy resin (BER) in waste PCB and the energy. However, the bromine content in the liquid product coming from the BER in waste PCB undermines the quality of the liquid product to be the feedstock or fuel. On the ground of the research which is carried out by my colleges, the present study focuses on debromination of the liquid product during the pyrolysis of the waste PCB.Based on the idea that debromining of plastic by the additives, this work tries to find a suitable additive to debromine the liquid product. This work chooses three additives and compare the debromination efficiency of them. It finds thatα-FeOOH is the best additive, that is, comparing to the pyrolysis without additives, the bromine content in the liquid product decreases from 31.17-65.27% to 4.39-15.93% with the temperature varying from 280-550℃while that in the solid increases from 50.76-11.49% to 84.66-60.02%. 350℃is the most suitable temperature to get the liquid product with the least bromine while 400℃is for gas among the choosing temperatures. The percents of inorganic bromine in the solid residue keep a good linear relation with the mass percents of the additives in the mixture prove the reaction between theα-FeOOH and HBr generating from the BER.GC/MS is used to analyze the organic components in the solid residue and liquid product generating during the pyrolysis of PCB. The organic bromine substances in the liquid product are bromoacetone, 2-bromophenol, 4-bromophenol, 2-bromo-4(1methylethyl)phenol, 2-bromo-4(1methylethenyl)phenol, 2,6-dibromo- phenol, 2,6-dibromo-4(1methylethyl)phenol, bromobisphenol A, dibromobisphenol and tribromobisphenol A. 2,4-dibromophenol and 2,4,6-tribromopheol only appear in the solid residues. By the careful analysis of the structure of BER's unit and providing the possible generating route of the organic substances detected in the liquid product, the present work improves the decomposition mechanism of BER. It figures out that: the breakage of C-O bond is the first step of generating volatilizing components, the breakage of the C-Br and C-Benzene happen during the whole decomposition of BER and their competitive relation reflects on the quantity relation of bromophenol and bromobisphenol. The possible generation routes provided in this work for the substances with two benzene rings give much more evidence to the synthesis of bromobisphenol A.