Pyrolysis of waste printed circuit board fragments: Response surface methodology optimization and effect of temperature on product characteristics

The direct pyrolysis of waste printed circuit board (WPCB) produces metal-enriched char, while its polymer fraction converts to valuable gas and liquid fractions. However, the low amount of organic fraction produces less liquid yield. Thus, the current study is focused on optimizing the pyrolysis parameters (temperature, heating rate, and hold time) towards maximum liquid and minimum solid (char) yields using response surface methodology (RSM). The purpose of the objective functions is to completely remove the organic material and convert most of it to liquid fraction while producing metal-enriched char. The RSM study was employed using a face-centered central composite design (CCD). The responses were analyzed using the analysis of variance (ANOVA), and the quadratic model was found to be the best-fit model. The ‘temperature’ was found to be the most significant parameter. Hence, further experiments were conducted by varying the temperature, keeping the heating rate and hold time constant, and the obtained products were subjected to detailed characterization. The obtained liquid samples were rich in aromatics with high calorific value (∼35 MJ/kg) and produced gases like H2 and CH4. This study provides a comprehensive approach, integrating both qualitative and quantitative analyses, to optimize WPCB pyrolysis for enhanced resource recovery.