Hydrochar for pollution remediation: Effect of process parameters, adsorption modeling, life cycle assessment and techno-economic evaluation

Hydrochar (HC) is a bio-based product and commonly used as a fuel or soil additive. Currently, the use of hydrochar for pollution remediation is increasing. While commercial applications of hydrochar as an energy source have been extensively studied. Its potential for pollution control, particularly in the removal of dyes and heavy metals, has primarily been explored at the laboratory scale, with no comprehensive reviews available in this domain. This review aims to provide a comprehensive summary of the hydrothermal carbonization (HTC) process, sources of feedstock, reaction mechanisms, and key influencing factors while also highlighting recent developments in the field. Our primary focus is to evaluate the application of hydrochar for removing dyes and heavy metals from wastewater. The efficiency and mechanisms involved in the biosorption process are described in detail, along with modeling methodologies employed. Additionally, we explore the merits related to environmental safety and the techno-economic benefits of such applications. Furthermore, this review considers potential regeneration options for biosorbents and addresses the challenges and future directions of this research. These insights are crucial for the eventual commercial-scale development of hydrochar as a valuable commodity in pollution remediation.