Hydrothermal treatment of contaminated sorghum: Hydrochar properties and characterization/phytotoxicity evaluation of the liquid phase
article
Reducing the heavy metals (HMs) content and enhancing the fuel quality of phytoremediation biomass is a crucial environmental and technical challenge. This study investigates hydrothermal carbonization (HTC) as a promising way to recycle HMs-contaminated sorghum (CS) into a cleaner solid biofuel and characterize and evaluate the liquid by-product more deeply. A systematic study of temperature (180–240◦C) and residence time (0.5–4 h) revealed that the hydrochar higher heating value increases with temperature (from 20.6MJ/kg to 25.5MJ/kg), albeit reducing the solid yield (down to 62 % from 80 %). HC200–0.5 was identified as the optimum best among the tested experimental conditions regarding the application of hydrochar as solid biofuel with respect to energy content and reduced HMs content. The low pH (3.96 ± 0.08) of the effluents due to the high concentration of carboxylic acids (up to 50 %), and the high total organic carbon (TOC) and HMs content are accountable for the strong phytotoxicity, as revealed by the complete inhibition of seed germination. These findings underline the necessity of post-treatment strategies for HTC effluents. This work puts emphasis on hydrochar quality and at the same time addresses the composition of the liquid phase and its toxicity, an aspect often neglected in the literature, proposing an integrated process to valorize HMs contaminated lignocellulosic biomass, retaining the contamination in the effluents that need to undergo adapted treatment
Topics
TNO Identifier
1019671
Source
Journal of Environmental Chemical Engineering(13), pp. 1-11.
Pages
1-11