Coagulation of microplastics using polyglutamic acid: insights from dlvo theory and experimental study

Microplastics have become a significant environmental and public health issue, particularly in Malaysia, where an estimated 0.4 to 0.9 million tons of plastic waste are discharged into water bodies annually. Traditional removal methods are insufficient, thus prompting the need for more effective solutions. This study introduces polyglutamic acid (PGA) as a novel, environment-friendly coagulant for microplastic removal, with polyethylene selected because of its prevalence in surface waters. Using jar tests, the optimal PGA dosage and pH for removal were determined, and mathematical modelling based on the Derjaguin–Landau (Verwey) theory was employed to predict the critical coagulation concentration (CCC). The findings indicate that 8 ppm PGA at a pH of 1 is optimal for microplastic removal, with the DLVO theory-based model aligned well with the experimental results. This study not only highlights the effectiveness of PGA as a coagulant, but also offers valuable insights into microplastic coagulation mechanisms, contributing to the development of improved water purification strategies in regions affected by severe plastic pollution.