Enrichment of microplastic pollution by micro-nanobubbles

Microplastic pollution has become a global environmental concern. It has been reported that microplastics are easily accessible to a wide range of aquatic organisms and ultimately enter the human body along the food chain. They pose a severe threat to ecosystems, organisms and even human health due to their durability and persistence. However, how to reduce microplastic pollution still remains a challenge in terms of scientific techniques and policy-making. There is currently still a lack of effective methods for microplastic recycling and removal. Luckily, a new technique, micro-nanobubbles (MNBs), may provide a possible and highly effective method to enrich microplastic pollution: their great advantages [1] include a high specific surface area, long lifetime and ability to adsorb microplastics of the same size and hydrophobicity. Then they further adsorb on larger bubbles such as microbubbles or millimeter bubbles and float to the water surface together. In this study, we present a new method using MNBs to enrich microplastic pollution with high efficiency. Two types of microplastics, millimeter-scale plastic fragments and microplastic particles, were chosen as the model microplastic pollution systems to study the enrichment efficiency of MNBs on microplastics. Results showed that MNBs can efficiently enrich these microplastics. The enrichment efficiency increases with flotation time until a maximum value is reached. It is proved that MNBs not only collect the microplastic pollution but also reduce detergent use in domestic laundry sewage. This is because detergent, as a surfactant, is easily absorbed on the surface of MNBs and can be collected together with the microplastic pollution. Our research has demonstrated that the MNB technique could be promising for use in microplastic recycling and reducing detergent pollution in daily life.