Utilization of Bubbles and Oil for Microplastic Capture from Water

Abstract

The removal of microplastics (MPs) from water using oil has shown early promise; however, incorporation of this technique into a feasible in situ method has yet to be developed. Here, a simple yet effective method of MP capture from water using vegetable oil with bubbles is demonstrated to achieve high removal efficiencies of > 98%. Comparisons are made with other methods of agitation, and higher removal efficiencies are observed when bubbles are used. Due to the low agitation provided by the bubbles, the oil layer remains unbroken, meaning that no oil is released into the bulk water phase. In this way, secondary contamination is avoided—unlike membrane filtration, another effective removal method, in which polymer-based membranes can break down due to chemical backwashing and ageing. It is demonstrated that variation in MP size within the micrometer range (50–170 μm) has minor impact on the removal efficiency; however, 100% removal is achieved for larger, millimeter-sized MPs (500–5000 μm). Similarly, a high removal efficiency of greater than 99% is achieved in the capture of microfibers. Other factors such as oil volume and water salinity are also investigated and discussed. Based on these results, the proposed method can be introduced into multiple setting types as a passive and continuous method of MP capture.