Recent development of natural polysaccharide-modified biochar on adsorption of pollutants from wastewater: Preparation, characterization, mechanisms and applications

The presence of toxic and hazardous substances in aquatic environments poses an enormous risk to ecosystems and human health. Recent years have witnessed a substantial rise in the utilization of biochar (BC) as an adsorbent for the remediation of water contamination. To augment the adsorption capability of pristine BC, a multitude of BC composites have emerged. Natural polysaccharides (NP), such as chitosan, sodium alginate, β-cyclodextrin, starch, and other substances, can act as modifiers for BC, enabling the incorporation of the benefits of both NP and BC. Generally, the formed composites demonstrate significant improvements in functional groups, specific surface area, adsorption sites, stability, and adsorption efficacy. Significantly, NP-BC demonstrates notable attributes as a green adsorbent while also being cost-effective in synthesis. Over the past five years, there has been a growing corpus of investigations on the topic of water pollutant adsorption, with a particular emphasis on the application of NP-BC. Nevertheless, a comprehensive evaluation of NP-BC remains absent, specifically regarding its modification techniques and characterization methodology. Furthermore, there is a notable absence of a systematic summary of research methodology concerning adsorption mechanisms. Consequently, the present study investigates the synthesis, characterization, and mechanism of NP-BC, along with its use in adsorbing water contaminants, including metal ions, organic pollutants, and inorganic ions. On this basis, this paper presents a comprehensive overview of the challenges that necessitate attention and the potential research directions worth exploring for NP-BC in removing water pollutants. According to the current dual-carbon policy, it is anticipated that NP-BC will have significant potential in water pollution remediation.