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 polyamide (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 °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 ~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.