Sustainable utilization of wetland biomass for activated carbon production: A review on recent advances in modification and activation methods

Constructed wetlands (CWs) as a green eco-technology have been applied for treating various wastewaters for several decades. However, sustainable reclamation of the harvested wetland biomass remains a challenge. Utilization of wetland biomass for value-added activated carbon (AC) production could be a potential strategy to improve the sustainability with multi-functions such as energy storage, resource recovery and environmental remediation. This paper aims to present a comprehensive review on the recent advances in production of ACs from wetland biomass and their application for adsorption of metal ions from wastewaters. The physicochemical properties of the ACs with chemical activations and their feasibility for heavy metal ions adsorption are compared, and the adsorption mechanisms are found to be complexation, physical adsorption, ion-exchange and electrostatic interactions. The surface chemistry of ACs impacted more on the adsorption ability towards heavy metal ions than their porosity. The in-situ modification during H3PO4 activation and new phosphorus-based activation are also summarized for enhancing the surface functionality and introducing specific surface functionalities on ACs, in turn promoting their adsorption ability for heavy metal ions. The high adsorption capacity and cost-effectiveness make these ACs as economical alternatives for waste remediation, and future research on the optimization and applications of ACs was also highlighted.