UV-induced aggregation of polystyrene nanoplastics: effects of radicals, surface functional groups and electrolyte

Document Type

Article

Publication Date

12-1-2020

Abstract

Aggregation behavior determines the fate and bioavailability of nanoparticles in aquatic environments. This study investigated the effect of UV irradiation and salts (NaCl, Na2SO4, CaCl2, and Na3PO4) on the aggregation of three polystyrene nanoparticles (PSNPs) with various surface functional groups. UV irradiation promoted the aggregation of pristine PSNPs in NaCl (>100 mM) and amino-modified PSNPs (PSNPs-NH2) in NaCl (≥100 mM) or Na2SO4 (≥100 mM) solutions. Under UV irradiation, hydroxyl radicals (OH) degraded the sulfate groups of PSNPs and amino groups of PSNPs-NH2 and decreased electrostatic repulsion forces among particles. Carboxyl-modified PSNPs (PSNPs-COOH) were relatively stable in NaCl and Na2SO4 solutions because of their high negative surface charge and hydrophilicity even after UV irradiation. Similarly, because the negative surface charge of PSNPs and PSNPs-NH2 in CaCl2 (1-50 mM) remained high under UV exposure, the strong electrostatic forces retarded the UV effect on the aggregation of PSNPs and PSNPs-NH2. However, UV irradiation accelerated PSNPs-COOH aggregation in CaCl2 (≥20 mM), probably because UV irradiation generated more carboxyl groups, which bind with Ca2+ and increase aggregation via a bridging effect. PO43- inhibited OH photogeneration and stabilized the three types of PSNPs. Our study reveals the intriguing effects of light irradiation and salts on the aggregation behavior of emerging plastic nanoparticles in aquatic environments. This journal is

Identifier

85098466491 (Scopus)

Publication Title

Environmental Science Nano

External Full Text Location

https://doi.org/10.1039/d0en00518e

e-ISSN

20518161

ISSN

20518153

First Page

3914

Last Page

3926

Issue

12

Volume

7

Grant

2018NJ399B

Fund Ref

New Jersey Water Resources Research Institute

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