Evaluating the factors affecting microplastic removal from synthetic leachate via electrocoagulation

Abstract

The ubiquitous presence of microplastics in the environment has raised concerns over their impact on human, environmental and ecological health. Landfill leachate, which is the highly toxic wastewater produced in landfills, is a primary source of microplastics into the soil and groundwater. Though microplastics have been detected in landfill leachate, studies on their presence and removal remain limited. Electrocoagulation has recently emerged as a viable and efficient wastewater treatment process. Although microplastic removal using electrocoagulation has been studied, the impact of the inter-electrode distance, the interaction between the variables, and the sample preparation technique need to be investigated. This study evaluates the effectiveness of electrocoagulation in the removal of microplastics from synthetic leachate sample to address these important gaps. Polyvinyl chloride samples were weathered using UV light before microplastics were leached from the samples to synthesize a wastewater sample containing weathered secondary microplastics. The electrocoagulation experiments were conducted across two phases whilst varying the inter-electrode distance (1-3 cm), initial pH (5-9), electrode material (aluminum and iron), current density (2-10 mA/cm2) and electrolysis time (15-45 minutes). The results show that electrocoagulation is effective in removing microplastics, with removal efficiencies exceeding 85% reported for all the experiments conducted. The analysis of the results show that the effects of the pH and inter-electrode distance were not significant for the removal of microplastics using aluminum electrodes but that the pH2 interaction was significant for the iron electrodes at a confidence level of 90%. The paired t-test results show that both electrode types were effective in removing microplastics and were statistically indifferent. In the second phase of the experiment, the current density and electrolysis time were found to be statistically significant with p-values of 0.0001 and 0.000, respectively. The optimal variables were consequently determined as: aluminum electrodes, inter-electrode distance of 2 cm, current density of 6 mA/cm2, and electrolysis time of 45 minutes, yielding a removal efficiency of 98%. The important findings of this study can be used in future studies to assess the removal of microplastics using electrocoagulation from real wastewater samples.