DIRECT HYDROTHERMAL VALORIZATION OF BIOMASS AND ELECTROPLATING EFFLUENT

Abstract

With the global increase in industrial activities and urban expansion, addressing cleaner energy production and wastewater treatment has become a critical aspect of responsible environmental management. Industrial activities, particularly those involving metal processing, contribute significantly to the carbon dioxide emission and contamination of water bodies with heavy metals, presenting significant environmental hazards and potential threats to human health. Heavy metals such as copper, zinc, cobalt, and nickel are a few of the most widely used metals, mainly in the electroplating and mining industries. Fatal consequences may arise if the trace amounts of these metals in the human body exceed the threshold limits. Therefore, these heavy metals must be recovered from the wastewater streams economically and effectively. Moreover, the energy utilized by heavy metal industries is produced from non-renewable sources (coal and oil), contributing to greenhouse gas emissions. The depletion of fossil fuel reservoirs, coupled with the escalating specter of global warming, prompts researchers to shift their attention toward renewable energy alternatives such as biomass. Biomass is a carbon-neutral and environmentally friendly energy resource with significant economic value and abundant reserves. The biomass's thermochemical conversion route (pyrolysis and gasification) encounters limitations attributed to its elevated moisture content, necessitating substantial energy inputs for the drying process. Supercritical water gasification (SCWG) offers a distinct advantage in effectively handling wet biomass to generate a hydrogen-rich fuel gas mixture. In this, supercritical water (SCW) is utilized as a solvent and reaction medium to transform lignocellulosic biomass into a fuel gas rich in high value H2-rich gaseous fuel and biochar. SCW shows improved heat transfer and mass transfer properties with higher solvation properties. To enhance the performance and yield of hydrogen, catalysts were incorporated into the process under controlled operating conditions during SCWG. However, these catalysts are prone to deactivation during the process. Henceforth, this research highlights the in-situ utilization of metal-contaminated wastewater as a catalyst infused with lignocellulosic biomass for the co-synthesis of a hydrogen-rich fuel gas mixture and nanometal carbon hybrid (NCH) via SCWG.