Understanding the Stability of Nanoplastics by Simulating Various Complex Aqueous Environments

Verma, Shivani (2022) Understanding the Stability of Nanoplastics by Simulating Various Complex Aqueous Environments. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS dissertation of Shivani Verma (17MS110)) 17MS110_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (4MB)

Abstract

The presence and accumulation of micro- and nano-plastics represent an issue of major environmental concern. The stability, transport and aggregation behavior of NPs is influenced by various environmental factors, therefore the present study is aimed at understanding the effect of ionic strength, NOM such as HA, inorganic colloids, pH, temperature and ambient water samples i.e., RW, GW and SW both in absence and presence of an additive such as DEP which is a plasticizer and are released during the fragmentation of plastics so as to simulate the complex chemistry of the aquatic environments to which the NPs are released from the run off effluents and waste water treatment plants. Divalent cations (Ca2+) lead to the faster rate of aggregation of negatively charged NPs resulting the drop in CCC value as compared to that of monovalent cations (Na+). NOM such as HA stabilizes NPs particles via steric hindrance and electrostatic repulsion by adhering to the surface of it through hydrophobic interaction or adsorption, at the same time promoting the particle aggregation in presence of polyvalent electrolytes by cation bridging. CCC value of salt for the aggregation of NPs in presence of inorganic colloids such as Hematite may rise or fall depending upon their PZC value i.e., whether they are positively or negatively charged at experimental pH value. The concentration of salt and NOM determines the stability and aggregation behavior of NPs in RW, GW and SW. Effect of DEP over the aggregation rate of NPs in presence of monovalent and polyvalent electrolyte is analogous to that of NOM such as HA as they both interact with NPs particles in similar manner i.e., via hydrophobic interaction. The results of this study provide a key insight on the fate and transport of NPs in complex water chemistry of aqueous environments.

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