Hydrothermal degradation of biomass with Zn electroplating metal effluent for H₂ production

Supercritical water gasification (SCWG) is an evolving technology that directly converts complex wet organic waste into hydrogen-rich fuel gases while simultaneously recovering heavy metals from the wastewater. In this study, lignocellulosic feedstock like cauliflower stalk, which is widely available in India, was used along with the heavy metal-contaminated wastewater from electroplating industries for hydrogen production. The research highlights the impact of residence time on the product distribution of gas, liquid, and solid phases. At 600 °C temperature and a 50 min residence time, the highest total gas yield (TGY) (31.7 mol/kg) and the maximum H₂ yield (26.2 mol/kg) were obtained. The treated liquid was analyzed using total organic carbon (TOC) and Microwave Plasma Atomic Electron Spectroscopy (MP-AES) analysis to measure organic carbon and metal concentration. FE-SEM, XRD, and XPS analysis confirm the immobilization of the heavy metals from wastewater to produce nanometal carbon composite during the supercritical water gasification process. The maximum specific surface area (73.43 m²/g) and the pore volume (0.12 cc/g) was obtained at 600 ℃, and the residence time was 60 min.