Suppressing effect of calcium-based waste on control of bromine flux during the pyrolysis of printed circuit boards

The effect of calcium-based addition on the brominate flux during printed circuit board (PCB) pyrolysis was investigated. It was found that bromine (Br) can be effectively fixed in solid phase during PCB pyrolysis by adding calcium-based waste materials. Phenol and 4-ethylphenol are the major products of pyrolysis. When the two kinds of red mud were used as additive, their content was 85.25 and 84.81%, respectively, which was higher than others. The 2-bromophenol and 2-bromo-4-methyl-benzene are the main Br-containing pyrolysis volatiles. After adding calcium-based additive, these two volatiles were apparently reduced and only small amounts of 2-bromo-4-methyl-benzene were detected in the products, namely 0.71 and 0.86%, respectively for the two kinds of red mud. Hence, no matter from the perspective of product use or simple Br-fixing, the bromine in the three-phase products can be effectively regulated and controlled by adding calcium-based waste residue during PCB pyrolysis. Finally, the Br-fixing mechanism was analysed. As a result, when calcium-based waste materials were added to the PCB pyrolysis it made bromine fix easily in the resident yielding a byproduct that can be further used.