Hydrothermal Treatment of Tetra Pak Waste with Metal Effluents towards Circularity

The present work introduces a novel, zero-waste, and integrated thermochemical process for the catalytic hydrothermal valorization of Tetra Pak waste (TPW) using a mixed Fe–Cu effluent as a dual-functioning liquefaction medium and an in situ catalyst. The impact of the Fe–Cu ratio on the product distribution was investigated. The optimum Fe–Cu ratio of 3:2 resulted in the highest light oil and heavy oil yields of 11.75 and 46.27 wt %, respectively. The synergistic catalytic role of Fe and Cu via the formation of in situ zerovalent metal ions and the release of active H2 enhanced the feedstock fragmentation and its effective conversion to produce the oil fraction. GC-MS and NMR analyses reveal oil fractions enriched in organic species such as alcohols, esters, ketones, aromatics, phenols, hydrocarbons, and organic acids. The deposition of the in situ produced Fe–Cu–Al2O3 nanoparticles onto the carbon matrix produced a metallic carbon nanocomposite (MCN), which was utilized for the fabrication of the supercapacitor electrode material, yielding a high specific capacitance of 119 F/g at 1 mV/s and exhibiting a 61.4% of capacitive retention over 2000 charge–discharge cycles at 1 A/g. Furthermore, the aqueous phase produced from catalytic liquefaction was subjected to supercritical water gasification (SCWG) at 600 °C for 60 min, and a remarkable (∼91%) TOC reduction was observed along with the formation of 1.06 mmol/g of H2. This work not only valorizes complex TPW but also exemplifies a sustainable circular strategy for the production of biofuel, functional material, and H2-rich fuel gas, thereby supporting both waste remediation and clean energy goals.