Removal of polystyrene nanoplastics from water by CuNi carbon material: The role of adsorption

Nanoplastics have attracted wide attention worldwide as a new potentially threatening pollutant, and they can cause harm to the organisms and pose threat to the water environment. Therefore, efficient removal techniques for nanoplastics are urgently needed. In this study, CuNi carbon material (CuNi@C) was prepared by hydrothermal method for the removal of polystyrene (PS) nanoplastics from water. CuNi@C was effectively adsorbed on PS nanoplastics. When the CuNi@C dosage increased from 0.1 g/L to 0.3 g/L, the removal efficiency of PS nanoplastics (10 mg/L) elevated from 32.72% to 99.18%. The images of the scanning electron microscope (SEM) and the Fourier transform infrared spectroscopy (FTIR) spectra of CuNi@C confirmed the adsorption of PS nanoplastics on the CuNi@C. The fitting results of adsorption kinetic models and isotherms equations demonstrated that physical adsorption and monolayer coverage were the predominant mechanisms of the PS nanoplastics adsorption on CuNi@C. Thermodynamics analysis illustrated the adsorption of PS nanoplastics on CuNi@C was a spontaneous and endothermic process. The electrostatic attraction occurred in adsorption progress, and the removal efficiency of PS nanoplastics in the acidic system was generally higher than that in the alkaline system. CuNi@C can be recycled via washing and drying treatment and these CuNi@C comparable PS nanoplastics removal performance to the original ones. After four times cycles, CuNi@C can still remove similar to 75% of total PS nanoplastics from water. This study reveals that CuNi@C can be used as promising techniques for the removal of PS nanoplastics from the aqueous environment.

Automated summary

Nanoplastics have become a global concern as a new type of threatening pollutant. This study demonstrated that CuNi@C prepared by hydrothermal method efficiently removes polystyrene (PS) nanoplastics from water through physical adsorption and monolayer coverage mechanisms, with electrostatic attractions playing a role in the process. The adsorption of PS nanoplastics on CuNi@C was found to be a spontaneous and endothermic process, with higher removal efficiency in acidic systems compared to alkaline systems.