Further research on the impacts of humic acid in the aggregation of nanoplastics: The roles of molecular weight and surface functionalization
Humic acid (HA) affects the aggregation behavior of nanoplastics. This study examines the adsorption of molecular weight (MW)-fractionated HA onto functionalized polystyrene nanoplastics (PS-Bare, PS-COOH, and PS-NH₂) in NaCl and CaCl₂, characterizes the properties of the adsorbed HA layer, and asse...
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Elsevier
2025-09-01
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| author | Feng-Yi Li Gui-Yun Song Qing-Xin Zhang |
| author_facet | Feng-Yi Li Gui-Yun Song Qing-Xin Zhang |
| author_sort | Feng-Yi Li |
| collection | DOAJ |
| description | Humic acid (HA) affects the aggregation behavior of nanoplastics. This study examines the adsorption of molecular weight (MW)-fractionated HA onto functionalized polystyrene nanoplastics (PS-Bare, PS-COOH, and PS-NH₂) in NaCl and CaCl₂, characterizes the properties of the adsorbed HA layer, and assesses their impact on nanoplastics stability. The results reveal that pristine and MW-fractionated HA form adsorbed layers with comparable functional groups and surface charge. However, the adsorbed layer thickness (ALT) exhibits a positive correlation with the adsorption mass and MW of HA. In NaCl, the maximum ALT values were 0.21∼5.93 nm for PS-Bare, 0.74∼9.43 nm for PS-COOH, and 2.23∼12.1 nm for PS-NH₂, whereas their ranges in CaCl₂ were 0.21∼7.1 nm, 1.05∼12.1 nm, and 2.61∼12.8 nm. The increased ALT elevated the critical coagulation concentration (CCC) values in NaCl from 343 to 426∼1266 mM for PS-Bare and 339 to 467∼1380 mM for PS-COOH, while the hydrodynamic diameter (Dh) of PS-NH₂ stabilized at approximately 143 nm, indicating enhanced steric repulsion and improved nanoplastics dispersion. Similar results were also observed in CaCl2 containing low concentrations of HA. However, in CaCl₂, higher-MW HA at 10 mg C L⁻¹ can counteract steric repulsion through a bridging effect, leading to decreasing CCC to 19.2∼23.1 mM for PS-Bare and to 18.7∼21.6 mM for PS-COOH. Lower-MW HA at 5 mg C L⁻¹ promotes increasing Dh of PS-NH₂ to 600∼900 nm via the synergistic effects of charge neutralization and weak steric hindrance. Additionally, HA<3 kDa induces increasing Dh of PS-NH₂ to 1300 nm through patch-charge attraction, irrespective of concentration. |
| format | Article |
| id | doaj-art-b3ac5216ddf641ee8b258bd931cd3050 |
| institution | Kabale University |
| issn | 2590-1230 |
| language | English |
| publishDate | 2025-09-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Results in Engineering |
| spelling | doaj-art-b3ac5216ddf641ee8b258bd931cd30502025-08-22T04:57:26ZengElsevierResults in Engineering2590-12302025-09-012710682310.1016/j.rineng.2025.106823Further research on the impacts of humic acid in the aggregation of nanoplastics: The roles of molecular weight and surface functionalizationFeng-Yi Li0Gui-Yun Song1Qing-Xin Zhang2Corresponding author.; College of Grassland, Inner Mongolia Minzu University, Tongliao, 027000, ChinaCollege of Grassland, Inner Mongolia Minzu University, Tongliao, 027000, ChinaCollege of Grassland, Inner Mongolia Minzu University, Tongliao, 027000, ChinaHumic acid (HA) affects the aggregation behavior of nanoplastics. This study examines the adsorption of molecular weight (MW)-fractionated HA onto functionalized polystyrene nanoplastics (PS-Bare, PS-COOH, and PS-NH₂) in NaCl and CaCl₂, characterizes the properties of the adsorbed HA layer, and assesses their impact on nanoplastics stability. The results reveal that pristine and MW-fractionated HA form adsorbed layers with comparable functional groups and surface charge. However, the adsorbed layer thickness (ALT) exhibits a positive correlation with the adsorption mass and MW of HA. In NaCl, the maximum ALT values were 0.21∼5.93 nm for PS-Bare, 0.74∼9.43 nm for PS-COOH, and 2.23∼12.1 nm for PS-NH₂, whereas their ranges in CaCl₂ were 0.21∼7.1 nm, 1.05∼12.1 nm, and 2.61∼12.8 nm. The increased ALT elevated the critical coagulation concentration (CCC) values in NaCl from 343 to 426∼1266 mM for PS-Bare and 339 to 467∼1380 mM for PS-COOH, while the hydrodynamic diameter (Dh) of PS-NH₂ stabilized at approximately 143 nm, indicating enhanced steric repulsion and improved nanoplastics dispersion. Similar results were also observed in CaCl2 containing low concentrations of HA. However, in CaCl₂, higher-MW HA at 10 mg C L⁻¹ can counteract steric repulsion through a bridging effect, leading to decreasing CCC to 19.2∼23.1 mM for PS-Bare and to 18.7∼21.6 mM for PS-COOH. Lower-MW HA at 5 mg C L⁻¹ promotes increasing Dh of PS-NH₂ to 600∼900 nm via the synergistic effects of charge neutralization and weak steric hindrance. Additionally, HA<3 kDa induces increasing Dh of PS-NH₂ to 1300 nm through patch-charge attraction, irrespective of concentration.http://www.sciencedirect.com/science/article/pii/S2590123025028877NanoplasticsHumic acidMolecular weightAdsorbed layer thicknessAggregation |
| spellingShingle | Feng-Yi Li Gui-Yun Song Qing-Xin Zhang Further research on the impacts of humic acid in the aggregation of nanoplastics: The roles of molecular weight and surface functionalization Results in Engineering Nanoplastics Humic acid Molecular weight Adsorbed layer thickness Aggregation |
| title | Further research on the impacts of humic acid in the aggregation of nanoplastics: The roles of molecular weight and surface functionalization |
| title_full | Further research on the impacts of humic acid in the aggregation of nanoplastics: The roles of molecular weight and surface functionalization |
| title_fullStr | Further research on the impacts of humic acid in the aggregation of nanoplastics: The roles of molecular weight and surface functionalization |
| title_full_unstemmed | Further research on the impacts of humic acid in the aggregation of nanoplastics: The roles of molecular weight and surface functionalization |
| title_short | Further research on the impacts of humic acid in the aggregation of nanoplastics: The roles of molecular weight and surface functionalization |
| title_sort | further research on the impacts of humic acid in the aggregation of nanoplastics the roles of molecular weight and surface functionalization |
| topic | Nanoplastics Humic acid Molecular weight Adsorbed layer thickness Aggregation |
| url | http://www.sciencedirect.com/science/article/pii/S2590123025028877 |
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