Efficient removal of microplastics from wastewater by an electrocoagulation process

With the gradual increase of microplastics in the water environment, it is imperative to understand the removal characteristics of microplastics in the current treatment process. Electrocoagulation (EC) is an effective water treatment technology. The purpose of this study is to investigate the removal performance, mechanism and influencing factors of microplastics in wastewater treatment by EC. The impacts of wastewater properties, including initial pH, electrolyte concentration, applied voltage density, anode materials, microplastic type and microplastic concentrations, on the removal efficiency of microplastics by EC were systematically investigated. The findings showed that aluminum anode was better than iron anode in the removal of microplastics, and the removal rate of was above 80% in all experiments, which indicates that aluminum anode EC is an effective method to remove microplastics in wastewater. The removal rate of four microplastics by EC can reach more than 82% in the range of pH 3-10, and the best removal rate was 93.2% for PE, 91.7% for PMMA, 98.2% for CA and 98.4% for PP at pH 7.2. The removal efficiency of fiber microplastics by EC is better than that of granular microplastics. The microplastic removal efficiency increased with the increase of electrolyte concentration and applied voltage density. Additionally, microplastics undergo flocculation and charge neutralization at the same time during EC. The economic evaluation of the reactor operation cost showed that the optimal EC reaction conditions were: 0.05 M of electrolyte concentration, pH 7.2, 10 V of applied voltage density and Al anode. Further research should focus on the possible reactor design and improvement to optimize the process and realize the replication and transfer from the laboratory to the sewage treatment plant.