A novel resource conversion strategy of waste plastic express packaging bags using supercritical water-ammonia process: Optimization by response surface methodology.

With the rapid development of e-commerce and express delivery industries, a large number of waste plastic express packaging bags (WPEPBs) are generated and urgent to be safely disposed. In this work, a novel resource conversion strategy was developed to produce high value-added chemicals from WPEPBs by supercritical water ammonia (SWA) process without any catalyst. WPEPBs could be converted into two parts by the SWA process: oil and solid residue. More than 80 % of the oil was identified as long-chain alkanes and alkenes due to the decomposition of polyethylene (PE) contained in WPEPBs. The presence of NH 3 in SWA was beneficial to improve the production of long-chain alkenes. The plasticizers in WPEPBs including bisphenol A (BPA) and phthalate ester (DEHP) could be efficiently converted into aniline (≈15%) and 2-ethylhexanol (≈4 %) due to the high reactivity of NH 3 in the SWA process. Compared with the degradation of WPEPBs in supercritical water, the SWA process could reduce side effects and improve the purity of target products. High-purity CaCO 3 powder could be further recovered from the solid residue. The optimal parameters of the SWA process for the conversion of WPEPBs by Response Surface Methodology (RSM) were 440.5 ℃, 90 min, and C NH3 of 4.8 wt%. The conversion ratio of WPEPBs (C WPEPBs) and CaCO 3 recovery ratio (R CaCO3) were 99.10 % and 98.85 %, respectively. In contrast to traditional methods for recycling of plastic waste such as mechanical recycling and incineration, the SWA process is believed to be a clean and high-efficiency resource conversion strategy for WPEPBs. [Display omitted] [ABSTRACT FROM AUTHOR]