Hydrothermal processes of contaminated biomass: fate of heavy metals and liquid effluent valorization
Résumé
This review evaluates the fate of heavy metals (HMs) during the hydrothermal conversion of biomass obtained from phytoremediation sites, by extensively exploring existing literature on the treatment and the utilization of liquid euents from hydrothermal processes applied to contaminated biomass, particularly focusing on both novel and conventional methods for HM wastewater treatment. Processes like combustion, pyrolysis, or gasication valorize contaminated biomass directly as fuel for energy generation, but post-treatment metal recovery must be guaranteed. Research reviewed suggests that hydrothermal carbonization (HTC) can shift HMs into the liquid phase under acidic conditions, allowing for their concentration and safe disposal while yielding clean hydrochar. HTC emerges as the most promising thermochemical process for treating contaminated biomass to remove pollutants and enable further processing into a clean biomass. However, euents loaded with HMs can cause environmental problems if not properly managed. This review highlights valuable studies on the valorization of contaminated biomass with HTC and proposes possible pathways for euent treatment such as adsorption, chemical precipitation, coagulation-occulation otation, and membrane separation. Unfortunately, there has been limited attention on the treatment of HTC euents from contaminated biomass. Eective disposal of HMs from HTC euents is crucial for any contaminated biomass valorization project. This review aims to address this gap by proposing current wastewater treatment methods applicable to HTC-contaminated biomass euents, a topic that may not have received extensive attention thus far.