Abstract:The escalating global plastic pollution has led to the accumulation of microplastics in water bodies. Their strong pollutant adsorption capacity and the difficulty of collection pose significant challenges to traditional treatment technologies. Microalgae, with their high environmental adaptability and robust metabolic capacity, have shown great potential in the bioremediation of microplastics. This review systematically explores the interaction mechanisms between microalgae and microplastics, bioremediation strategies, and co-conversion pathways. Regarding the interaction mechanisms, extracellular polymeric substances (EPS) secreted by microalgae are the key drivers for the formation of heterogeneous aggregates, enabling interfacial adhesion through charge regulation and hydrogen bonds. The relative size of microplastic to microalgae regulates aggregation behavior: similar sizes facilitate aggregation and sedimentation; excessively large particles block light; overly small particles induce cytotoxicity. The toxicity of microplastics to microalgae is influenced by multiple factors, including particle size, concentration, and degree of aging. Moreover, microalgae can accelerate the aging and degradation of microplastics through physical abrasion and hydrolytic enzyme activity. In terms of bioremediation, it is essential to match the surface properties of microalgal strains with those of microplastics, regulate EPS secretion and biofilm growth, and balance system shear forces to achieve stable removal. For co-conversion pathways, the co-pyrolysis or liquefaction of microalgae and microplastics can reduce nitrogen- and oxygen-containing impurities in bio-oil via the hydrogen-donating effect of microplastics. Additionally, this process can yield porous carbon with a high specific surface area or fluorescent carbon quantum dots. However, current research on microalgae-based bioremediation of microplastics still faces notable limitations. Most studies on toxicity and degradation mechanisms rely on static experimental systems involving a single microplastic type and a single microalgal species, which fail to simulate real hydrodynamic conditions (e.g., flow velocity and turbulence intensity) in aquatic environments. Furthermore, the coupling effects of multiple pollutants (such as heavy metals and pharmaceutical compounds) are often overlooked. The co-conversion process also suffers from discontinuity, and no correlation model has yet been established among raw material ratios, reaction atmospheres, and product quality, hindering industrial scale-up. Future research should prioritize the targeted construction of multi-microalgal synergistic remediation systems. Hydrodynamic simulation devices should be introduced to replicate real aquatic environments, and remediation experiments should be conducted under the coexistence of multiple pollutants. Additionally, multi-stage continuous-flow co-conversion reactors should be developed, with optimized catalyst selection and reaction parameters. Ultimately, these efforts will promote the transition of bioremediation technology from laboratory research to industrial application. This review aims to bridge the gap between microplastic remediation and microalgae resource utilization, offering an environmentally friendly and economically viable approach to microplastic pollution control, while providing theoretical support for further research and industrial implementation. Close-