Interaction of polystyrene nanoplastics with impurity-bearing ferrihydrite and implication on complex particle sedimentation

Leiye Sun; Jiayan Wu; Meiqing Chen; Tianming Wang; Zhongbo Shang; Jieyu Liu; Minye Huang; Pingxiao Wu

doi:10.1016/j.scitotenv.2023.165928

Interaction of polystyrene nanoplastics with impurity-bearing ferrihydrite and implication on complex particle sedimentation

Sci Total Environ. 2023 Nov 25:901:165928. doi: 10.1016/j.scitotenv.2023.165928. Epub 2023 Jul 30.

Authors

Leiye Sun¹, Jiayan Wu¹, Meiqing Chen¹, Tianming Wang¹, Zhongbo Shang¹, Jieyu Liu¹, Minye Huang¹, Pingxiao Wu²

Affiliations

¹ School of Environment and Energy, South China University of Technology, Guangzhou Higher Education Mega Centre, Guangzhou 510006, PR China.
² School of Environment and Energy, South China University of Technology, Guangzhou Higher Education Mega Centre, Guangzhou 510006, PR China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, Guangzhou 510006, PR China; Guangdong Provincial Engineering and Technology Research Center for Environmental Risk Prevention and Emergency Disposal, South China University of Technology, Guangzhou Higher Education Mega Centre, Guangzhou 510006, PR China; Guangdong Provincial Key Laboratory of Solid Wastes Pollution Control and Recycling, Guangzhou 510006, PR China; Guangdong Engineering and Technology Research Center for Environmental Nanomaterials, Guangzhou 510006, PR China. Electronic address: pppxwu@scut.edu.cn.

PMID: 37527713
DOI: 10.1016/j.scitotenv.2023.165928

Abstract

Nanoplastics (NPs) usually coexist with impurity-bearing ferrihydrite (ImFh), and their interaction is related to their environmental fate. In this study, the aggregation between ImFh (impurities: Al, Mn and Si) and polystyrene nanoplastics (PSNPs), as well as the sedimentation of ImFh-PSNP complex particles in the aqueous phase were investigated systematically with particle concentrations of 100 mg/L ImFh and 10 mg/L PSNPs. Our results revealed that the PSNP suspension was dispersive and stable under various pH values and low ion strength. After coexisting with ImFh, PSNPs aggregated with the positively charged ImFh to form ImFh-PSNP complex particles, which destroyed the stability of PSNPs. The increase in pH and Na⁺ concentration could inhibit their aggregation, but high Na⁺ concentration (>20 mM) caused the homoaggregation of PSNPs. The aggregation capacity of PSNPs with ImFh was in the order of Al-bearing Fh > Fh > Mn-bearing Fh > Si-bearing Fh. Zeta potential and Derjaguin-Landau-Verwey-Overbeek (DLVO) calculations indicated that Al-bearing Fh showed higher positive potential than pure Fh, which caused stronger electrostatic interactions with PSNPs. However, Mn and Si in ImFh decreased the positive potential and inhibited the electrostatic interaction with PSNPs, and the effect of Si was greater than that of Mn. The aggregation between ImFh and PSNPs inhibited the sedimentation of their complex particles, and the higher aggregation capacity appeared to have a greater inhibition degree. Due to the "electrostatic patches" effect of PSNPs, the energy barrier of the ImFh-PSNPs particles was higher than that of the ImFh particles. Our findings clarified the influence of impurities on the interaction between ImFh and PSNPs and provided insight regarding their fate in the environment.

Keywords: Environment fate; Impurity-bearing ferrihydrite; Interaction; Nanoplastics; Sedimentation.