Transport and retardation of microplastic in biochar

Microplastic is an emerging contaminant of concern. Presence of microplastic at significant level in aquatic and soil environments has been reported in recent studies; which highlights the microplastic pollution as a global environmental challenge. Recent studies have shown that biochar; which is a product of pyrolysis of biomass, presents promising properties as a carbonaceous absorbent for managing various contaminants. We will present the results of a series of experimental investigations on the removal of microplastic spheres (microbeads) by biochar and the interactions between microbeads and biochar. Filtration properties of biochar samples produced at three different temperatures from corn straw and a hardwood biochar show significant capacity for the removal and immobilisation of 10 μm diameter microplastic spheres. Biochar samples showed high immobilisation (95% removal efficiency) whilst 60-80% of microplastic particles were retained in sand under same experimental conditions. The microscopic examination of the samples that were retrieved after the leaching tests revealed that the microplastic spheres were immobilised through three morphologically controlled mechanisms (or combinations of those) which are conceptualised to be stuck, trapped and entangled mechanisms whilst the microplastic spheres would only stuck in the sand.