(170f) Effect of Recycling HTC Process Liquid on Hydrochar Morphology and Its Corresponding Performance on Dye Adsorption

The dying process industries release many chemicals through the polluted wastewater that result in the death of aquatic life, ruining of soil and poisoning of drinking water. Henceforth, this study addresses the adsorption of dye from the wastewater through various quality hydrochars and optimize the adsorption process. Hydrochars are produced via Hydrothermal Carbonization (HTC) which is a thermochemical process that converts wet waste biomass into effective adsorbent. HTC has been successfully reported for wastes including but not limited to food waste, sewage sludge, dairy manure, municipal solid wastes, and agricultural wastes. Despite producing huge quantity of liquid in the reaction products, the hydrochar has received attention to date for its ability to act as an adsorbent. However, the HTC process liquid remains a concern for potential commercialization due to its high disposal costs and environmental pollution potentials. Therefore, this study focused on the recyclability of the process liquid to the HTC reaction to produce different quality hydrochars, to enhance the sorption capacity and further minimize the waste disposal cost. The consequence of preceding process liquid recycle at each HTC of corn stover for ten cycles with a focus on the char characteristic was studied. The HTC was done for 230 °C with a fixed residence time of 30 mins. The resulting chars were characterized through mass yield, ultimate analysis, and surface morphology (BET surface area, pore size, pore volume), pH, pH at point of zero charge (pH_PZC) and surface functionalities to evaluate their dye sorption capacity and two adsorption isotherm models (Langmuir and Freundlich) were fitted at 4, 20 and, 36 °C. Finally, a comparative analysis was done between the resulting chars and the optimum recycle number was found out in terms of adsorption performance.