Quantitative Investigation of the Size-dependent Aggregation of Nanoplastics

HU Tingting; LI Zhixiong; CHEN Jiawei

doi:10.15898/j.ykcs.202305020058

Rock and Mineral Analysis > 2024 > 43(1): 101-113. > DOI: 10.15898/j.ykcs.202305020058

HU Tingting，LI Zhixiong，CHEN Jiawei. Quantitative Investigation of the Size-dependent Aggregation of Nanoplastics[J]. Rock and Mineral Analysis，2024，43（1）：101−113. DOI: 10.15898/j.ykcs.202305020058

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Quantitative Investigation of the Size-dependent Aggregation of Nanoplastics

School of Earth Science and Resources, China University of Geoscience (Beijing), Beijing 100083, China

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Received Date: May 01, 2023
Revised Date: August 28, 2023
Accepted Date: September 16, 2023
Available Online: December 07, 2023

Abstract

HIGHLIGHTS
(1) Smaller NPs have higher CCC value than larger NPs and thus may transport longer distance.

(2) Ionic strength and pH are the key factors to affect the aggregation of NPs.

(3) The aggregation of NPs is controlled by their electrical state of charged interfaces.

ABSTRACT

The geochemical behavior of microplastics (MPs) and nanoplastics (NPs) in the environment has become a global hot topic. Aggregation effect is an important factor controlling the geochemical behavior of NPs, yet there is conflicting evidence regarding the dependence of aggregation on NPs size. Investigating the general patterns and dominant mechanisms governing the aggregation behavior of different-sized NPs under various environmental conditions, will provide help in understanding and predicting the fate of NPs with different sizes. The study has shown that NPs with the same chemical composition but different sizes have different stability and mobility under the same conditions. The critical coagulation concentration (CCC) for NPs increases with the decrease in particle size at a fixed surface ζ potential (CCC=325mmol/L, 296mmol/L, 264mmol/L for 50nm, 100nm, and 200nm, respectively); indicating smaller NPs may transport longer distances. As the pH increased from 5.5 to 7, the negative surface charge of 100 and 200nm NPs allowed them to remain stable even at higher ionic strength. However, 50 nm NPs underwent rapid aggregation because of its smaller ζ potential. Therefore, the effects of pH, ionic strength and NPs sizes should be considered comprehensively in predicting and evaluating the geochemical behavior of NPs in the natural environment. The BRIEF REPORT is available for this paper at http://www.ykcs.ac.cn/en/article/doi/10.15898/j.ykcs.202305020058.
- nanoplastics,
- aggregation,
- dynamic light scattering,
- critical coagulation concentrations,
- size-dependent effect
BRIEF REPORT
Significance: Microplastics (MPs) are defined as plastic fragments or particles with the size of <5mm^[3], which are directly manufactured by industry or derived from weathering of large-sized plastic^[4]. These tiny plastics are easily ingested by organisms of various trophic levels and have toxic effects on organisms^[5-6]. Clarifying the geochemical transport behavior and fate of MPs is a crucial prerequisite for assessing their environmental impacts throughout the entire life cycle, making it a hot topic in environmental research^[7-8]. Among all the MPs, those with a size <1μm are defined as nanoplastics (NPs)^[9-10]. NPs exhibit stronger interactions with other pollutants and more adverse eco-impacts on living things than MPs^[11-12]. Furthermore, the quantitative analysis of NPs is more challenging than that of MPs. The smaller size, stronger Brownian motion, and higher specific surface area of NPs result in significantly different environmental behaviors from MPs^[13]. Therefore, it is necessary to further study the transport and fate of NPs.

　　The aggregation behavior of NPs in aquatic environments is an important factor influencing its transport and fate^[14]. When the aggregation rate is slow, NPs can remain suspended and transport long distances with river currents. Conversely, rapid aggregation leads to a substantial increase in the size of NPs aggregates, making them more prone to settling at the water bottom^[15]. In recent years, scholars have investigated the influence of environmental factors such as pH value and ion strength on NPs aggregation by using dynamic light scattering (DLS) technique^[18-19]. These studies have not taken into account the effects of NPs size, while the NPs exist as various sizes in the environment. Size, as a paramount property of NPs is likely to significantly impact their aggregation behavior. Currently, there is limited research on how changes in NPs size affect aggregation behavior. Therefore, it is imperative to explore the combined effects of particle size, ion strength, pH value, and other factors on NPs aggregation behavior and elucidate the primary mechanisms involved.

　　Investigating the general patterns and dominant mechanisms governing the aggregation behavior of different-sized NPs under various environmental conditions, will provide help in understanding and predicting the fate of NPs with different sizes. The study has shown that NPs with the same chemical composition but different sizes have different stability and mobility under the same chemical solution conditions. The critical coagulation concentration (CCC) for NPs increases with the decrease in particle size at a ﬁxed surface ζ potential, thus the smaller NPs may transport longer distances. Therefore, the effects of solution pH, ionic strength and size of NPs should be considered comprehensively in predicting and evaluating the geochemical behavior of NPs in the natural environment.

Methods: The dynamic light scattering (DLS) technique was used to quantitively measure the aggregation kinetics of three typical polystyrene NPs (PSNPs) with the size of 50nm (PS50), 100nm (PS100) and 200nm (PS200), respectively, under various environmental conditions. The aggregation kinetics experiments of PSNPs were conducted at room temperature (25℃). In brief, samples containing 1.25mL of PSNPs suspension (20mg/L) were prepared in a sample cuvette. Subsequently, 1.25mL of NaCl electrolyte solution was added to the samples. After 1 second of rapid mixing, the sample cuvette was immediately transferred to the sample chamber of a nanoparticle size/zeta potential analyzer to measure the hydrodynamic diameters (D_h) of PSNPs.

　　To clarify the size-dependent aggregation of NPs, the ζ potentials and D_h of PS50, PS100 and PS200 were measured in the presence of NaCl (0-800mmol/L). The initial pH value was not adjusted, and the pH of the samples was finally stabilized at 5.5±0.3 after testing. Furthermore, the ζ potentials and hydrodynamic diameters of PS50, PS100, PS200 were obtained at the range of pH (3.0-10.0) in a 400mmol/L NaCl solution. The initial pH of the solution was adjusted using 0.1mol/L sodium hydroxide and 0.1mol/L hydrochloric acid. For each set of solution conditions, the experiments were repeated twice. Importantly, the critical coagulation concentration (CCC) and interaction potential energy were calculated.

Data and Results: (1) DLS technique combined with Derjaguin-Landau–Verwey–Overbeek theory (DLVO) was used to investigate the mechanism of the size-dependent aggregation of NPs. The morphology of PS50, PS100 and PS200 were all spherical and had good dispersity in deionized water, as shown in Fig.1. With the increase of NaCl concentration, the aggregation rate of the three NPs gradually increased at 200-400mmol/L. When the NaCl concentration was above 400mmol/L, the aggregation rate of NPs reached the maximum and no longer increased, as shown in Fig.2. To quantify the dispersion stability of different-sized NPs under various solution conditions, the attachment efficiencies (α) of PS50, PS100, and PS200 as a function of solution electrolyte concentration were obtained by normalizing the initial aggregation rate of NPs according to equation (3). The CCC values of PS50, PS100 and PS200 in NaCl solution were 325mmol/L, 296mmol/L and 264mmol/L by ﬁtting the stability proﬁle with equation (4). The results show that larger PSNPs were more likely to aggregate.

　　Fig.5 shows that the stability proﬁle was in good agreement with DLVO theoretical calculations. For instance, the energy barrier among NPs decreased with increasing NaCl concentration resulting in a higher tendency for NPs to aggregate. As the electrolyte concentration exceeded the CCC, the energy barrier was eliminated, thus the van der Waals attraction forces dominated the particle interactions. However, the CCC values of PS50, PS100 and PS200 obtained by the aggregation kinetics experiment deviated from DLVO theory. The reason for such a deviation may be due to the application of the superposition principle in evaluating the electrical interaction energy^[38]. Taking into account the case that the thickness of the electrical double layer isn’t necessarily much smaller than the linear size of the particle, it can be speculated that the smaller NPs had the thicker double electric layer, accordingly, a higher electrolyte concentration is required to completely compress the double electric layer.

　　(2) ζ potential serves as a crucial parameter for quantitative assessment of NPs stability. Under all experimental conditions, a significant correlation was observed between the attachment efficiency and ζ potential (r²=0.70-0.88, p<0.05), as shown in Fig.6. This indicates that environmental factors such as ion strength and pH values affected the dispersion stability of NPs by altering electrostatic interaction. Data obtained by Lee et al.^[19] for PSNPs in natural river water and seawater, as well as their ζ potentials, also supported this finding. The PSNPs had ζ potentials in the range of −30mV to −24mV in river water at different temperatures, indicating PSNPs exhibited a relatively stable condition. In seawater, the ζ potentials of PSNPs were in the range of −15mV to −5mV, and rapid aggregation occurred. Therefore, ζ potentials can be used to preliminarily assess the stability of NPs.

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References (44)

References

[1]	Koelmans A A, Redondo-Hasselerharm P E, Nor N H M, et al. Risk assessment of microplastic particles[J]. Nature Reviews Materials, 2022, 7(2): 138−152. doi: 10.1038/s41578-021-00411-y
[2]	McDevitt J P, Criddle C S, Morse M, et al. Addressing the issue of microplastics in the wake of the microbead-free waters act—A new standard can facilitate improved policy[J]. Environmental Science & Technology, 2017, 51(12): 6611−6617.
[3]	Thompson R C, Olsen Y, Mitchell R P, et al. Lost at sea: Where is all the plastic?[J]. Science, 2004, 304(5672): 838−838. doi: 10.1126/science.1094559
[4]	Halle T A, Ladirat L, Gendre X, et al. Understanding the fragmentation pattern of marine plastic debris[J]. Environmental Science & Technology, 2016, 50(11): 5668−5675.
[5]	Vethaak A D, Legler J. Microplastics and human health[J]. Science, 2021, 371(6530): 672−674. doi: 10.1126/science.abe5041
[6]	刘沙沙, 梁绮彤, 陈诺, 等. 纳米塑料对生物的毒性效应及作用机制研究进展[J]. 生态毒理学报, 2022, 17(4): 99-108. Liu S S, Liang Q T, Chen N, et al. Research progress on toxic effects and mechanisms of nanoplastics on organisms[J]. Asian Journal of Ecotoxicology, 2022, 17(4): 99-108.
[7]	Alimi O S, Farner B J, Hernandez L M, et al. Microplastics and nanoplastics in aquatic environments: Aggregation, deposition, and enhanced contaminant transport[J]. Environmental Science & Technology, 2018, 52(4): 1704−1724.
[8]	胡婷婷, 陈家玮. 土壤中微塑料的吸附迁移及老化作用对污染物环境行为的影响研究进展[J]. 岩矿测试, 2022, 41(3): 353−363. doi: 10.3969/j.issn.0254-5357.2022.3.ykcs202203002 Hu T T, Chen J W. A review on adsorption and transport of microplastics in soil and the effect of ageing on environmental behavior of pollutants[J]. Rock and Mineral Analysis, 2022, 41(3): 353−363. doi: 10.3969/j.issn.0254-5357.2022.3.ykcs202203002
[9]	Halle T A, Jeanneau L, Martignac M, et al. Nanoplastic in the North Atlantic subtropical gyre[J]. Environmental Science & Technology, 2017, 51(23): 13689−13697.
[10]	Gigault J, Halle A T, Baudrimont M, et al. Current opinion: What is a nanoplastic?[J]. Environmental Pollution, 2018, 235: 1030−1034. doi: 10.1016/j.envpol.2018.01.024
[11]	Ni B J, Thomas K V, Kim E J. Microplastics and nanoplastics in urban waters[J]. Water Research, 2023, 229: 119473. doi: 10.1016/j.watres.2022.119473
[12]	Liu L, Xu K X, Zhang B W, et al. Cellular internalization and release of polystyrene microplastics and nanoplastics[J]. Science of the Total Environment, 2021, 779: 146523. doi: 10.1016/j.scitotenv.2021.146523
[13]	Gigault J, El Hadri H, Nguyen B, et al. Nanoplastics are neither microplastics nor engineered nanoparticles[J]. Nature Nanotechnology, 2021, 16(5): 501−507. doi: 10.1038/s41565-021-00886-4
[14]	Liu Y J, Hu Y B, Yang C, et al. Aggregation kinetics of UV irradiated nanoplastics in aquatic environments[J]. Water Research, 2019, 163: 114870. doi: 10.1016/j.watres.2019.114870
[15]	Yuan B, Gan W H, Sun J, et al. Depth profiles of microplastics in sediments from inland water to coast and their influential factors[J]. Science of the Total Environment, 2023, 903: 166151.
[16]	Praetorius A, Badetti E, Brunelli A, et al. Strategies for determining heteroaggregation attachment efficiencies of engineered nanoparticles in aquatic environments[J]. Environmental Science:Nano, 2020, 7(2): 351−367. doi: 10.1039/C9EN01016E
[17]	Wang X J, Bolan N, Tsang D C W, et al. A review of microplastics aggregation in aquatic environment: Influence factors, analytical methods, and environmental implications[J]. Journal of Hazardous Materials, 2021, 402: 123496. doi: 10.1016/j.jhazmat.2020.123496
[18]	Wang J Y, Zhao X L, Wu A M, et al. Aggregation and stability of sulfate-modified polystyrene nanoplastics in synthetic and natural waters[J]. Environmental Pollution, 2021, 268: 114240. doi: 10.1016/j.envpol.2020.114240
[19]	Lee C H, Fang J K H. Effects of temperature and particle concentration on aggregation of nanoplastics in freshwater and seawater[J]. Science of the Total Environment, 2022, 817: 152562. doi: 10.1016/j.scitotenv.2021.152562
[20]	Kim M J, Herchenova Y, Chung J, et al. Thermodynamic investigation of nanoplastic aggregation in aquatic environments[J]. Water Research, 2022, 226: 119286. doi: 10.1016/j.watres.2022.119286
[21]	Mao Y F, Li H, Huangfu X L, et al. Nanoplastics display strong stability in aqueous environments: Insights from aggregation behaviour and theoretical calculations[J]. Environmental Pollution, 2020, 258: 113760. doi: 10.1016/j.envpol.2019.113760
[22]	Liu L, Song J, Zhang M, et al. Aggregation and deposition kinetics of polystyrene microplastics and nanoplastics in aquatic environment[J]. Bulletin of Environmental Contamination and Toxicology, 2021, 107(4): 741−747. doi: 10.1007/s00128-021-03239-y
[23]	Li X, He E, Xia B, et al. Protein corona induced aggregation of differently sized nanoplastics: Impacts of protein type and concentration[J]. Environmental Science: Nano, 2021, 8(6): 1560−1570. doi: 10.1039/D1EN00115A
[24]	Quevedo I R, Tufenkji N. Mobility of functionalized quantum dots and a model polystyrene nanoparticle in saturated quartz sand and loamy sand[J]. Environmental Science & Technology, 2012, 46(8): 4449−4457.
[25]	Gong Y Y, Bai Y, Zhao D Y, et al. Aggregation of carboxyl-modified polystyrene nanoplastics in water with aluminum chloride: Structural characterization and theoretical calculation[J]. Water Research, 2022, 208: 117884. doi: 10.1016/j.watres.2021.117884
[26]	Li J, Yang X J, Zhang Z Z, et al. Aggregation kinetics of diesel soot nanoparticles in artificial and human sweat solutions: Effects of sweat constituents, pH, and temperature[J]. Journal of Hazardous Materials, 2020, 403: 123614.
[27]	Chen C Y, Huang W L. Aggregation kinetics of diesel soot nanoparticles in wet environments[J]. Environmental Science & Technology, 2017, 51(4): 2077−2086.
[28]	Liu J J, Dai C, Hu Y D. Aqueous aggregation behavior of citric acid coated magnetite nanoparticles: Effects of pH, cations, anions, and humic acid[J]. Environmental Research, 2018, 161: 49−60. doi: 10.1016/j.envres.2017.10.045
[29]	Petosa A R, Jaisi D P, Quevedo I R, et al. Aggregation and deposition of engineered nanomaterials in aquatic environments: Role of physicochemical interactions[J]. Environmental Science & Technology, 2010, 44(17): 6532−6549.
[30]	Cai L, Hu L L, Shi H H, et al. Effects of inorganic ions and natural organic matter on the aggregation of nanoplastics[J]. Chemosphere, 2018, 197: 142−151. doi: 10.1016/j.chemosphere.2018.01.052
[31]	Lowry G V, Hill R J, Harper S, et al. Guidance to improve the scientific value of Zeta-potential measurements in nanoEHS[J]. Environmental Science:Nano, 2016, 3(5): 953−965. doi: 10.1039/C6EN00136J
[32]	Yu S J, Shen M H, Li S S, et al. Aggregation kinetics of different surface-modified polystyrene nanoparticles in monovalent and divalent electrolytes[J]. Environmental Pollution, 2019, 255: 113302. doi: 10.1016/j.envpol.2019.113302
[33]	Lu S H, Zhu K R, Song W C, et al. Impact of water chemistry on surface charge and aggregation of polystyrene microspheres suspensions[J]. Science of the Total Environment, 2018, 630: 951−959. doi: 10.1016/j.scitotenv.2018.02.296
[34]	Tang H, Zhao Y, Yang X N, et al. New insight into the aggregation of graphene oxide using molecular dynamics simulations and extended Derjaguin-Landau-Verwey-Overbeek theory[J]. Environmental Science & Technology, 2017, 51(17): 9674−9682.
[35]	董会军, 董建芳, 王昕洲, 等. pH值对HPLC-ICP-MS测定水体中不同形态砷化合物的影响[J]. 岩矿测试, 2019, 38(5): 510−517. doi: 10.15898/j.cnki.11-2131/td.201808230096 Dong H J, Dong J F, Wang X Z, et al. Effect of pH on determination of various arsenic species in water by HPLC-ICP-MS[J]. Rock and Mineral Analysis, 2019, 38(5): 510−517. doi: 10.15898/j.cnki.11-2131/td.201808230096
[36]	孟瑞芳, 杨会峰, 白华, 等. 海河流域大清河平原区地下水化学特征及演化规律分析[J]. 岩矿测试, 2023, 42(2): 383−395. Meng R F, Yang H F, Bai H, et al. Chemical characteristics and evolutionary patterns of groundwater in the Daqing River Plain area of Haihe Basin[J]. Rock and Mineral Analysis, 2023, 42(2): 383−395.
[37]	曹寒, 张月, 金洁, 等. 土壤中碘的赋存形态及迁移转化研究进展[J]. 岩矿测试, 2022, 41(4): 521−530. doi: 10.15898/j.cnki.11-2131/td.202203170055 Cao H, Zhang Y, Jin J, et al. Iodine speciation, transportation, and transformation in soils: A critical review[J]. Rock and Mineral Analysis, 2022, 41(4): 521−530. doi: 10.15898/j.cnki.11-2131/td.202203170055
[38]	Chen K L, Elimelech M. Relating colloidal stability of fullerene (C₆₀) nanoparticles to nanoparticle charge and electrokinetic properties[J]. Environmental Science & Technology, 2009, 43(19): 7270−7276.
[39]	Hsu J P, Liu B T. Effect of particle size on critical coagulation concentration[J]. Journal of Colloid and Interface Science, 1998, 198(1): 186−189. doi: 10.1006/jcis.1997.5275
[40]	Afshinnia K, Sikder M, Cai B, et al. Effect of nanomaterial and media physicochemical properties on Ag NM aggregation kinetics[J]. Journal of Colloid and Interface Science, 2017, 487: 192−200. doi: 10.1016/j.jcis.2016.10.037
[41]	Xu C Y, Zhou T T, Wang C L, et al. Aggregation of polydisperse soil colloidal particles: Dependence of Hamaker constant on particle size[J]. Geoderma, 2020, 359: 113999. doi: 10.1016/j.geoderma.2019.113999
[42]	Pochapski D J, Carvalho dos Santos C, Leite G W, et al. Zeta potential and colloidal stability predictions for inorganic nanoparticle dispersions: Effects of experimental conditions and electrokinetic models on the interpretation of results[J]. Langmuir, 2021, 37(45): 13379−13389. doi: 10.1021/acs.langmuir.1c02056
[43]	Chowdhury I, Duch M C, Mansukhani N D, et al. Colloidal properties and stability of graphene oxide nanomaterials in the aquatic environment[J]. Environmental Science & Technology, 2013, 47(12): 6288−6296.
[44]	Dong Z Q, Qiu Y P, Zhang W, et al. Size-dependent transport and retention of micron-sized plastic spheres in natural sand saturated with seawater[J]. Water Research, 2018, 143: 518−526. doi: 10.1016/j.watres.2018.07.007

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Quantitative Investigation of the Size-dependent Aggregation of Nanoplastics