Removal of microplastics in wastewater via electrocoagulation and recycling of Fe3O4-C composite as anode material for lithium ion batteries

초록

With the explosive increase in the amount of plastic used in recent decades, a large amount of plastic waste accumulates in a form of microplastics in the ocean, acting as a serious source of pollution in an aquatic ecosystem. Despite the effort to reduce the indiscriminate usage and disposal of plastics waste, the development of microplastic treatment technologies in wastewater is urgently required for the purpose of restoring the contaminated natural environment. In general, the wastewater is purified through a water treatment process (WTP) consisting of a coagulation-flocculation-sedimentation-filtration steps. The key to WTP is to make pollutants into heavy and insoluble flocs, precipitating them by gravity, which is implemented using aluminum or iron-based coagulants. However, the flocs produced by the traditional method require sufficient time for sedimentation and separation in the treatment tank, and they are a source of contamination themselves that must be treated with additional time and cost. In this study, we designed the process of electrocoagulation-flocculation-magnetic sedimentation and filtration using iron metal which is able to act as a coagulant to remove microplastics in wastewater. In electrocoagulation (EC), in which metal ions are electrically dissolved in a metal working electrode (aluminum or iron) to form flocs through agglomeration with microplastics, the variation in the pH of electrolyte caused by hydrogen evolution taking place at the counter electrode leads to the formation of aggregated flocs with different crystalline phase compared to those produced by conventional manner. Therefore, by applying iron as a working electrode, Fe3O4 flocs with magnetic property are obtained that can be straightforwardly precipitated and filtered simultaneously using a magnet in a few seconds with removal efficiency of 97 %. In addition, since the magnetite constituting the iron flocs is a transition metal oxide with a high theoretical capacity of 9