Microplastic removal by coagulation: a review of optimizing the reaction conditions and mechanisms

Coagulation is a widely employed technique for removing suspended particles from water and wastewater, and recently, it has gotten attention as a popular method for the removal of microplastics (MPs). Studies on coagulation-based removal of MPs are still in their infancy, and few findings are available about this treatment approach, its mechanism, and removal efficiency. Given these gaps, this study was designed to comprehensively investigate recent advances in the removal of MPs via coagulation. The influence of various experimental factors such as coagulant type, dose of the coagulant, pH of the solution, and shape of the MPs are critically reviewed. The study findings showed that optimizing environmental conditions during the coagulation process is crucial for improving the removal of MPs and reducing energy costs. The study findings showed that the coagulation efficiency of MPs depends on optimal reaction conditions, which may vary depending on the type and concentration of MPs and the characteristics of the water or wastewater being treated. Optimizing these reaction conditions is, therefore, critical to achieving maximum removal efficiency. More extensive research is required to reveal the mechanisms of coagulation in controlling floc density and removing pollutants from effluent. Consequently, the current review aims to highlight the gaps and challenges associated with coagulation techniques for the removal of MPs during wastewater treatment. Current advancements in the synthesis and chemical modification of bio-based coagulants and their coagulation performance for the removal of MPs could constitute a paradigm shift in ecosystem protection and sustainability. The use of eco-friendly coagulants and combining coagulation with other techniques are suggested to increase the efficacy and viability of this method. This review will provide significant insights for field researchers, guiding their future investigations and contributing to the advancement of knowledge.