Microplastic Removal by Flotation: Systematic Review, Meta-Analysis, and Research Trends

Abstract

Microplastic (MP) pollution is a global concern due to its persistence, ubiquity, and potential ecological and health risks. Although various MP separation techniques exist, flotation has gained attention as a promising approach adapted from mineral processing. This study provides a systematic review, bibliometric analysis, and meta-analysis of MP removal using flotation, covering 31 papers published between 2015 and 2024. Research output has grown rapidly since 2020, with China (including Hong Kong) as the leading contributor with strong international collaborations. Bibliometric mapping highlighted hotspots such as polymer type, particle size, contact angle, and nanobubbles. Meta-analysis showed that flotation achieved high removal efficiencies across water and solid matrices, though performance varies with polymer properties, surfactants used, and experimental design. Studies focused on solid particles remain limited, reflecting greater methodological challenges than in water systems. Critical discussion emphasized the need for standardized protocols, scaling from laboratory to field applications, and integration with wastewater treatment. This review identified knowledge gaps and emerging trends that can inform the future development of flotation as an effective technology for mitigating MP pollution.