Removal of microplastics from aqueous solutions by magnetic carbon nanotubes

Microplastics (MPs), as reservoirs of cocktail of contaminants, impose severe impacts on human and ambient water environment. Therefore, efficient and eco-friendly MPs removal techniques are urgently needed. In this study, for the first time, magnetic carbon nanotubes (M-CNTs) have been synthesized as adsorbates to remove MPs. M-CNTs were effectively adsorbed on polyethylene (PE), polyethylene terephthalate (PET), and poly amide (PA) and all the MPs/M-CNTs composites were readily separated from aqueous solutions by magnetic force. When the 5 g.L-1 of M-CNTs was added, target MPs (5 g.L-1) were completely removed within 300 min. The maximum adsorption capacities of PE, PET and PA were 1650, 1400 and 1100 mg-M-CNTs.g(-1), respectively. This process was hardly affected by the COD, NH3-N, and PO43- substance and all MPs were completely removed from the wastewater discharged from a kitchen waste treatment plant. Furthermore, the adsorbed M-CNTs can be recycled via thermal treatment (600 degrees C) and these M-CNTs were featured with the same magnetic properties and comparable MPs removal capacity to the original ones. After being used for four times, M-CNTs were still able to remove similar to 80% of total MPs in the testing solution. The observed effectual removal of MPs from prepared solutions and wastewater highlights M-CNTs as promising techniques for the control of MPs pollution.

Automated summary

This study synthesized magnetic carbon nanotubes (M-CNTs) as adsorbates for the efficient removal of microplastics. The M-CNTs were able to effectively adsorb various types of microplastics and could be easily separated by magnetic force. Additionally, the adsorbed M-CNTs showed potential for recycling and maintained high removal capacity after multiple uses.