Enhancement of terephthalic acid recovered from PET waste using a combination of citric acid and dimethyl sulfoxide extraction

This study aimed to develop an eco-friendly, cost-efficient, and practically viable method for extracting terephthalic acid (HBDC) from polyethylene terephthalic (PET) waste. Dimethyl sulfoxide (DMSO) was combined with either citric acid (CHO) or HSO to enhance the particle size of HBDC, and the optimum conditions during the acidification step were determined. Additionally, response surface methodology was employed to examine the influence and interaction of extractant (NaOH) concentration, hydrolysis temperature, and time on the optimal HBDC yield and recovery ratio. Experimental results demonstrated that NaOH concentration significantly impacted both HBDC yield and recovery ratio, surpassing the effects of hydrolysis temperature and time. Under optimal conditions involving a temperature of 200 °C and a 12 h reaction time with 5% NaOH, the model predicted a 100% yield and recovery ratio, which closely matched the experimental results of 99% and 100% for yield and recovery ratio, respectively. To enhance particle size, a combination of DMSO and CHO was more effective than HSO. The maximum particle size achieved was 57.4 µm under the following optimum conditions: premixing 5 M CHO with DMSO at a 35:75 mL ratio and maintaining a reaction temperature of 75 °C for 40 min. The study demonstrated the stability and consistency of the method. The HBDC yield remained between 96 and 98% with high purity over eight consecutive cycles of using the DMSO and CHO mixture. The findings highlight the importance of integrating CHO and DMSO to enhance HBDC quality, meeting commercial product criteria with evidence of high purity and large particle size. This method presents a promising solution for extracting HBDC from PET waste, with potential implications for the recycling industry and a positive environmental impact.