Mini-hydrocyclone performance enhancement in removing small-size microplastics using flocculants

Abstract

The presence of microplastics (MPs) poses a threat to organisms. However, an effective method is still lacking to remove small-size MPs (5 < d < 20 μm). Mini-hydrocyclones provide a promising solution to this problem but suffer low removal efficiency. Therefore, this paper proposes using flocculants to improve the removal efficiency of mini-hydrocyclones. For these purposes, experimental studies are conducted using a 10-mm hydrocyclone with the addition of flocculants. The considered MPs have a size of 10 μm. The effects of a few key variables on the flocculation and separation performance are quantified, including flocculant concentration, initial water pH value, flocculant type, and the inlet feed velocity. Additionally, numerical results are also conducted to better understand the effect of flocculant additions. The results show that the flocculant addition increases the removal efficiency by 14 % and the concentration ratio by 0.24 to the maximum. The optimum performance is identified for a medium dosage of flocculant concentration and an initial pH of 3 and 9. Aluminum flocculant type affects cyclone performance the least compared with other variables. Moreover, a moderate inlet feed velocity generates adequate centrifugal forces for separation while avoiding floc breakage, which helps achieve high removal efficiency.