Insights into microplastics (MPs) removal using aquatic plant-derived biochar from Taihu Lake at varying carbonization temperatures

Abstract

Microplastics (MPs), recognized as significant emerging contaminants, are prevalent in both terrestrial and aquatic ecosystems. This study investigates the potential of biochar derived from Polygonum amphibium L. (PAL) sourced from Taihu Lake and processed through a low-temperature carbonization method, for in the removal of MPs. This approach addresses the escalating presence of MPs in aqueous environment, especially during the COVID-19 pandemic, simultaneously tackles the issue of waste biomass contributing to eutrophication. The study focused on the impact of carbonization temperatures (450℃-550℃) on physicochemical properties of biochar. Additionally, the effect of contact time, initial concentration of MPs, and environmental factors at various carbonization temperatures were also examined. The results reveal that the biochar yield and adsorption performance of biochar are significantly influenced by carbonization temperature. The adsorption capacity of biochar for MPs removal increases with the carbonization temperature up to 500 ℃, attributed to enhanced diffusion, surface adsorption, interactions, and cation-π electron interactions between the biochar and MPs. However, at a pyrolysis temperature of 550 ℃, the increase in adsorption capacity of biochar-550 is marginal due to increased competitive binging and destabilization of biochar under basic conditions. Overall, the optimum carbonization temperature is identified as 500 ℃, yielding a char rate is 32.23% and an adsorption capacity for MPs of 80.3 mg/g, thereby offering a promising solution for MP removal and water eutrophication management.