Nylon 6 and nylon 6,6 micro- and nanoplastics: A first example of their accurate quantification, along with polyester (PET), in wastewater treatment plant sludges

Valter Castelvetro; Andrea Corti; Alessio Ceccarini; Antonella Petri; Virginia Vinciguerra

doi:10.1016/j.jhazmat.2020.124364

Nylon 6 and nylon 6,6 micro- and nanoplastics: A first example of their accurate quantification, along with polyester (PET), in wastewater treatment plant sludges

J Hazard Mater. 2021 Apr 5:407:124364. doi: 10.1016/j.jhazmat.2020.124364. Epub 2020 Oct 23.

Authors

Valter Castelvetro¹, Andrea Corti², Alessio Ceccarini², Antonella Petri³, Virginia Vinciguerra²

Affiliations

¹ Department of Chemistry and Industrial Chemistry, University of Pisa, Pisa, Italy; CISUP - Center for the Integration of Scientific Instruments of the University of Pisa, Pisa, Italy. Electronic address: valter.castelvetro@unipi.it.
² Department of Chemistry and Industrial Chemistry, University of Pisa, Pisa, Italy; CISUP - Center for the Integration of Scientific Instruments of the University of Pisa, Pisa, Italy.
³ Department of Chemistry and Industrial Chemistry, University of Pisa, Pisa, Italy.

PMID: 33139109
DOI: 10.1016/j.jhazmat.2020.124364

Abstract

A novel procedure for nylon 6 and nylon 6,6 polyamide (PAs) microplastics (MPs) quantification is described for the first time. The overall procedure, including quantification of poly(ethylene terephthalate) (PET), was tested on wastewater treatment plant (WWTP) sludges. The three polymers account for the largest global share of synthetic textile microfibers, being possibly the most common MPs released upon laundering in urban wastewaters. Therefore, measuring their content in WWTP sludges may provide an accurate picture of the potential risks associated with both the inflow of these MPs in natural water bodies and the practice of using WWTP sludges as agricultural soil amendment. The novel procedure involves PAs depolymerization by acid hydrolysis followed by derivatization of the monomers 6-aminohexanoic acid (AHA) and hexamethylene diamine (HMDA) with a fluorophore. Reversed-phase HPLC analysis with fluorescence detection results in high sensitivities for both AHA (LOD = 8.85·10^-4 mg/L, LOQ = 3.73·10^-3 mg/L) and HMDA (LOD = 2.12·10^-4, LOQ = 7.04·10^-4 mg/L). PET quantification involves depolymerization, in this case by alkaline hydrolysis, followed by HPLC analysis of its comonomer terephthalic acid. Eight sludge samples from four WWTPs in Italy showed contamination in the 29.3-215.3 ppm and 10.6-134.6 ppm range for nylon 6 and nylon 6,6, respectively, and in the 520-1470 ppm range for PET.

Keywords: Depolymerization; Microfibers; Microplastics; Poly(ethylene terephthalate); Polyamide.

Publication types

Research Support, Non-U.S. Gov't