Abstract
This paper describes a kinetic study of the decomposition of waste printed circuit boards (WPCB) under conventional and microwave-induced pyrolysis conditions. We discuss the heating rates and the influence of the pyrolysis on the thermal decomposition kinetics of WPCB. We find that the thermal degradation of WPCB in a controlled conventional thermogravimetric analyzer (TGA) occurred in the temperature range of 300 °C–600 °C, where the main pyrolysis of organic matter takes place along with an expulsion of volumetric volatiles. The corresponding activation energy is decreased from 267 kJ/mol to 168 kJ/mol with increased heating rates from 20 °C/min to 50 °C/min. Similarly, the process of microwave-induced pyrolysis of WPCB material manifests in only one stage, judging by experiments with a microwave power of 700 W. Here, the activation energy is determined to be only 49 kJ/mol, much lower than that found in a conventional TGA subject to a similar heating rate. The low activation energy found in microwave-induced pyrolysis suggests that the adoption of microwave technology for the disposal of WPCB material and even for waste electronic and electrical equipment (WEEE) could be an attractive option.
Highlights
Due to the rapid development of technology, the lifespan of electrical and electronic equipment (EEE) is very short, resulting in increasing quantities of waste electronic and electrical equipment (WEEE)
The main thermal degradation temperature in this paper were a little high when compared to the work of Chen et al [19] and Chiang et al [31] which could be caused by high heating rates and different compositions
This work describes a kinetic study of the thermal decomposition of waste printed circuit boards (WPCB) subject to both conventional thermogravimetric analyzer (TGA) electric heating and a microwave thermogravimetric system, the experimental conditions such as particle size, sample mass, flow rate of purge gas, etc., were different in the microwave pyrolysis vs. conventional TGA experiments
Summary
Due to the rapid development of technology, the lifespan of electrical and electronic equipment (EEE) is very short, resulting in increasing quantities of waste electronic and electrical equipment (WEEE). As one of the most important branches of the WEEE stream, waste printed circuit boards (WPCB) are generally considered to be representative of WEEE, and have received increasing attention from the public and researchers because they contain a wealth of nonferrous metals in addition to a variety of toxic materials [3,4]. Pyrolysis can be described as the thermal decomposition of organic components in an oxygen-free atmosphere to yield char, oil, and gas, and it holds promise as an approach to optimal waste upgrading, especially for organic polymers. The applications of MWP include the pyrolysis of plastic waste [5,6], the pyrolysis of biomass waste [7,8,9,10,11,12,13], sewage sludge [14,15], and waste automotive engine oil [16,17,18], among others
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