Influence of laundry effluent stability on fibre fragments indentification

Abstract

Among various sources of microplastics, synthetic textiles are one of the main sources of fibrillar microplastics in aquatic environments. Fiber fragments (FFs) are mostly released during the washing process of textiles. The challenges associated with FFs characterization and quantification are related to the wide range of concentrations and degree of degradation. The laundry effluent samples present a particular challenge as they contain a residual component of the detergents used in washing processes, such as sufractants. In addition, surfactants promote the formation of aggregates composed of fibre fragments and inorganic components of the detergent (e.g. zeolites). These aggregates exhibit altered physico-chemical properties that lead to an underestimation of the fiber fragments number, which is a direct consequence of the entanglement of several fibre fragments. The aim of this study was to investigate the possibility of identifying polyethylene terephthalate fibre fragments both in water and detergent suspensions. In order to investigate the influence of solution or suspension stability on the FFs identification, the formation of aggregates was carried out with both freshly prepared but also with 5 days aged suspensions. The amount of fibre fragments in the suspensions was determined gravimetrically after membrane filtration followed by characterisation of the filter cake using an optical microscope. It was confirmed that the presence of detergents leads to aggregate formation. Furthermore, aging of the solution results in an even greater extent of aggregate formation.Sintetičke tekstilije, Među različitim izvorima mikroplastike, predtavljaju jedan su od glavnih izvora fibrilarne mikroplastike u vodenom okolišu. Fragmenti vlakana (FF) najviše se oslobađaju tijekom procesa pranja tekstila. Izazovi u karakterizaciji i kvantifikaciji FF-a povezani su s njihovim širokim rasponom koncentracija i stupnjem razgradnje. Uzorci otpadnih voda iz pranja posebno su izazvoni za analizu jer sadrže ostatke deterdženata korištenih u procesu pranja, poput površinski aktivnih tvari (surfaktanata).Osim toga, surfaktanti potiču stvaranje agregata koji se sastoje od fragmenata vlakana i anorganskih komponenti deterdženta (npr. zeolita). Ujedno formirani agregati sastavljni od više zapetljanih fragmenata vlakna pokazuju promijenjena fizikalno-kemijska svojstva, što dovodi do podcjenjivanja broja fragmenata vlakana.Cilj ovog istraživanja bio je ispitati mogućnost identifikacije fragmenata vlakana poli(etilen-tereftalata) (PET) u uzorcima vodei i suspenzija deterdženta. Kako bi se istražio utjecaj stabilnosti otopine ili suspenzije na identifikaciju frgamenata vlakna, formiranje agregata provedeno je u svježe pripremljenim suspenzijama, ali i u suspenzijama koje su ostavljene da odstoje pet dana. Količina fragmenata vlakana u suspenzijama određena je gravimetrijskom metodom nakon filtracije pomoću membranskog filtra, a talog na filtru analiziran je optičkim mikroskopom. Potvrđeno je da prisutnost deterdženata dovodi do stvaranja agregata, dok starenje otopine rezultira još izraženijim stvaranjem agregata.