Thermogravimetric Analysis and Kinetic Study of Biochemically Pretreated Printed Circuit Board Wastes

The problems with e-waste have received significant attention worldwide. This study examined the recovery of energy and materials from the epoxy component of e-waste by pyrolysis. The potential to reduce the pyrolysis temperature through pre-degradation was considered. Pre-degradation was conducted by immersing epoxy wastes in biometabolic acids including sulphuric, nitric, lactic, citric, and malic acids. For the purpose of this screening test, this was conducted over a short period of time, 6 h. The thermal degradation of the neat and pretreated epoxy e-waste were studied using thermogravi-metric analysis. The neat epoxy demonstrated thermal degradation from 300 to 400 degrees C, with maximum weight loss at around 350 degrees C. Preliminary screening test demonstrated the degradation of all pre-treated epoxy samples. All treated samples showed shifts in degradation to lower temperatures and loss of specific functional group characteristics of depolymerisation. The polarity of the acids appears to play a role in easing the accessibility and thus attack of the epoxy. Organic acids with lower polarity induced higher shift in degradation temperature in comparison to mineral acids. Kinetic analysis was conducted by dynamic and isothermal analyses. The dynamic analysis revealed the pre-treatment with acids resulted in lowering of the activation energies of pyrolysis (EA) from 251.6 to 228.7 kJ mol(-1) and the frequency factors (A) from 9.63 x 10(20) to 1.44 x 10(20) min(-1). The reduction in kinetic parameters was also confirmed in the isothermal study, where it was revealed the effect of pre-treatment on the pyrolysis kinetics of epoxy is greater, with 2 stage degradation, where the reduction of activation energy was less than half of the raw epoxy. These lower kinetic parameters (E-A and A) are indicative of the reduction in the thermal stability of the epoxy resulting from partial degradation. These results demonstrate the efficacy of acid induced pre-degradation of epoxy as a method for reducing the energy requirement of pyrolysis.