Utilizing nature-based adsorbents for removal of microplastics and nanoplastics in controlled polluted aqueous systems: A systematic review of sources, properties, adsorption characteristics, and performance

The pervasive distribution of microplastics and nanoplastics in water systems has raised significant concerns about their ecological and human health impacts. Traditional methods to mitigate plastic pollution are often inadequate, prompting the need for innovative and sustainable solutions. Agricultural waste or by-products (AWBP) are underutilized sources of adsorbents for environmental pollution control, particularly for microplastic and nanoplastic removal. Despite their low cost and high adsorption capacities, AWBP are frequently burned, dumped, or placed in landfills. Most importantly, there remains a notable gap in research, i.e., a systematic review of AWBP-based adsorbents for the removal of microplastics and nanoplastics, which is the novelty of this review. Therefore, using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) method, this study reviewed the use of hydrochar, biochar, and activated carbon (collectively termed nature-based adsorbents) for the removal of microplastics and nanoplastics, focusing on their sources, properties, adsorption characteristics, and performance. The principal findings and major conclusions indicate that these adsorbents can achieve up to 100 % adsorption efficiency for the removal of microplastics and nanoplastics. Environmental factors such as pH, temperature, and co-existing species can influence adsorption performance. Functional groups like -COOH, -OH, and -CO enhanced adsorption efficiency. Multiple mechanisms, including physisorption and chemisorption, contributed to high adsorption capacities. The pseudo-second-order kinetic model best described the adsorption processes, with the Langmuir isotherm providing the best fitting. Additionally, these adsorbents offer long-term carbon sequestration and align with several Sustainable Development Goals. This review highlights current knowledge gaps and provides recommendations for future research to further improve this technology.