A sustainable emulsion for separation and Raman identification of microplastics and nanoplastics

Abstract

The extensive occurrence of small plastic particles in the environment and our foods, and the resulting hazardous effects to nature and people have become an issue of increasing concern worldwide. The currently established approaches and tools for the elimination of the emerging contaminants, in particular micro- and nano-scale plastic particles, from environmental and food matrices have been often limited to the use of poorly sustainable materials and complicated preparation/operation. Here we show a conceptually new strategy for the removal of microplastics and nanoplastics using an olive oil-based emulsion. By emulsifying naturally occurring olive oil, water and emulsifiers at an oil-to-water ratio of 5:12, a stable O/W emulsion can be produced by mechanical agitation, which can adsorb onto microplastics and nanoplastics via hydrophobic interactions. Upon demulsification, interestingly, the tiny plastic particles can be enriched at an efficiency up to ∼87%, attributable to the affinity-driven encapsulation of the plastics by the merged oil phase. We further demonstrate the emulsion affords the removal of tiny plastic particles from seawater, tea leaves, soil and toothpaste supernatants at considerably low concentration levels in efficiencies of 75%, 80%, 83% and 82%, respectively, while preserving uncompromised performance. The identification of the extracted plastics has been achieved using Raman spectroscopy, which has implications in health risk assessment and clarification of the contamination route. Given the high removal efficiency, green feature and generality of the emulsion coupled with Raman fingerprints, sustainable materials for the depollution of microplastics and nanoplastics are within reach.