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Removal of pristine and aged microplastics from water by magnetic biochar: Adsorption and magnetization

The Science of The Total Environment 2023 132 citations

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Researchers evaluated whether magnetic corncob biochar could effectively remove both pristine and aged polyamide microplastics from water. The study found that aging dramatically changed the surface properties of microplastics, and the biochar removed approximately 97% of aged microplastics compared to only 25% of pristine ones, with smaller particle sizes further improving removal. Evidence indicates that adsorption combined with magnetization offers a practical approach for removing environmentally weathered microplastics from water.

Polymers

Adsorption is an efficient and eco-friendly removal technique for small pristine microplastics in water. However, small pristine microplastics are not representative of those large microplastics in natural water with different aging levels. Whether the adsorption technique is effective in removing large aged microplastics from water remained unknown. To this end, the removal efficiency of large polyamide (PA) microplastics with different aging time by magnetic corncob biochar (MCCBC) was evaluated under different experimental conditions. After treated by heated-activated potassium persulfate, the physicochemical properties of PA have changed dramatically, as evidenced by rough surface, decreased particle size and crystallinity, and increased oxygen-containing functional groups, which enhanced with aging time. These changes promoted the combination of aged PA and MCCBC, thereby resulting in a higher removal efficiency of aged PA (~97 %) than that of pristine ones (~25 %). It is supposed that the adsorption process was a result of complexation, hydrophobic interaction, and electrostatic interaction. Increased ionic strength inhibited the removal of both pristine and aged PA, and neutral pH conditions favored PA removal. Furthermore, particle size played a great role in the removal of aged PA microplastics. When the particle size of aged PA was smaller than 75 μm, their removal efficiency was significantly increased (p < 0.01). The small PA microplastics were removed by adsorption, whereas the large ones were removed by magnetization. These research findings highlight magnetic biochar as promising technique for removing environmental microplastics.

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