dissertation
Vaibhav Budhiraja (Avtor), Andrej Kržan (Mentor)

Povzetek

Plastics are based on organic polymers that are sensitive to the environment in which they find themselves and will gradually decay through a variety of chemical reactions. This process is of great importance for the transformation and persistence of microplastics (MPs) that pollute the environment. The rate of degradation depends on two major factors: Firstly, the intrinsic properties of the polymers, such as chemical structure, molecular weight, crystallinity and the presence of additives, fillers or reinforcement and secondly, the environment to which they are exposed. The degradation rate of plastic will vary in different environmental matrices like soil, freshwater, seawater, wastewater, land etc., as well as in diverse environmental conditions like UV radiation, temperature, humidity, the effect of pollutants etc. Plastic mainly undergoes two fundamental reactions: oxidation and hydrolysis and the chemical structure of the polymer and its additives plays a key role in the degradation mechanism of plastic. Polyolefins having a carbon-only main chain are resistant to hydrolysis but susceptible to oxidation, whereas polyesters and polyamides containing heteroatoms are sensitive to hydrolysis and much more resistant to oxidation. In the context of the present work, five different studies were done involving both naturally degraded plastic and accelerated weathering of plastics in the form of small particles, MPs. In the first study, natural degraded polyethylene (PE) and polypropylene (PP) samples with a life span of more than forty years were collected from the environment and their physiochemical properties were analysed. The results show that red coloured PE samples were more degraded as compared to blue coloured samples, indicating that pigment plays a key role in the degradation. The PP sample shows extreme surface degradation, leading to fragmentation and the generation of MPs. In the second study, the effect of hydrodynamic cavitation on MPs in waste water treatment plant sludge was evaluated. PE, PP, polyethylene terephthalate and polyamide were extracted from the sludge. It was found that hydrodynamic cavitation does not disintegrate the MPs, although it removes some toxic metals and shows cell disruption mechanisms. Other studies were done with accelerated weathered MPs, which include PE, PP and tire wear particles (TWP), that were treated in accordance with an ISO 4892 standard weathering procedure that mimics natural weathered conditions. In the third study, we used weathered PE films to evaluate the synergistic adsorption behaviour of two pollutants, namely triclosan (TCS) and methylparaben (MeP). It was found that weathered MPs adsorb more pollutants and the adsorption behaviour of TCS is enhanced in the presence of MeP. In the fourth study, the magnetic extraction of pristine and weathered PE and TWP particles was performed. The results confirmed that the magnetic VI extraction of weathered MPs is difficult as compared to pristine MPs as their surface becomes more hydrophilic with weathering. In the fifth study, the effect of weathering on the density of PE and PP was evaluated. We found that weathering enhances the density of polyolefins, which is one of the main reasons for the observed sinking of polyolefin MPs in water.

Ključne besede

accelerated weathering;aging;density;magnetic separation;pigment;plastic degradation;pollutants;polyethylene, polyolefin;polypropylene;sinking;tire wear particles;dissertations;

Podatki

Jezik: Angleški jezik
Leto izida:
Tipologija: 2.08 - Doktorska disertacija
Organizacija: UNG FPŠ - Fakulteta za podiplomski študij
Založnik: [V. Budhiraja]
UDK: 678.5:504.5(043.3)
COBISS: 197682179 Povezava se bo odprla v novem oknu
Št. ogledov: 1460
Št. prenosov: 5
Ocena: 0 (0 glasov)
Metapodatki: JSON JSON-RDF JSON-LD TURTLE N-TRIPLES XML RDFA MICRODATA DC-XML DC-RDF RDF

Ostali podatki

Sekundarni jezik: Slovenski jezik
Sekundarni naslov: Razgradnja mikroplastike v okolju
Sekundarni povzetek: Plastika temelji na organskih polimerih, ki so občutljivi na okolje, v katerem se znajdejo, in postopoma razpadajo zaradi različnih kemijskih reakcij. Ta proces je zelo pomemben za preoblikovanje in obstojnost mikroplastike (MPs), ki onesnažuje okolje. Hitrost razgradnje je odvisna od dveh glavnih dejavnikov: prvič, od notranjih lastnosti polimerov, kot so kemijska struktura, molekulska masa, kristaliničnost in prisotnost dodatkov, polnil ali ojačitev, in drugič, od okolja, ki mu je polimer izpostavljen. Hitrost razgradnje plastike se razlikuje v različnih okoljskih matricah, kot so tla, sladka voda, morska voda, odpadna voda, kopno itd., ter v različnih okoljskih pogojih, kot so UV sevanje, temperatura, vlažnost, vpliv onesnaževal itd. Plastika je v glavnem podvržena dvema temeljnima reakcijama: oksidaciji in hidrolizi, kemijska struktura polimera in njegovih dodatkov pa ima ključno vlogo pri mehanizmu razgradnje plastike. Poliolefini z glavno verigo, ki vsebuje samo ogljik, so odporni na hidrolizo, vendar dovzetni za oksidacijo, medtem ko so poliestri in poliamidi, ki vsebujejo heteroatome, občutljivi na hidrolizo in veliko bolj odporni na oksidacijo. V okviru tega dela je bilo opravljenih pet različnih študij, ki so vključevale naravno razgrajeno plastiko in pospešeno vremensko razgradnjo plastike v obliki majhnih delcev. V prvi študiji so bili iz okolja zbrani naravni vzorci degradiranega polietilena (PE) in polipropilena (PP) z življenjsko dobo več kot štirideset let in analizirane njihove fizikalno-kemijske lastnosti. Rezultati kažejo, da so bili rdeče obarvani vzorci PE bolj razgrajeni v primerjavi z modro obarvanimi vzorci, kar kaže, da ima pigment ključno vlogo pri razgradnji. Vzorec PP izkazuje izjemno degradacijo površine, kar vodi v fragmentacijo in nastanek MPs. V drugi študiji je bil ocenjen učinek hidrodinamične kavitacije na MP v blatu čistilnih naprav. Iz blata so bili ekstrahirani PE, PP, polietilen tereftalat in poliamid. Ugotovljeno je bilo, da hidrodinamična kavitacija ne razgradi MP, čeprav odstrani nekatere strupene kovine in pokaže mehanizme razbijanja celic. Druge študije so bile opravljene s pospešenimi vremensko obremenjenimi MP, ki vključujejo PE, PP in delce iz obrabe pnevmatik (TWP), ki so bili obdelani v skladu s standardnim postopkom ISO 4892, ki posnema naravne vremenske razmere. V tretji študiji smo uporabili vremensko obremenjene filme PE za oceno sinergijskega adsorpcijskega obnašanja dveh onesnaževal, in sicer triklosana (TCS) in metilparabena (MeP). Ugotovljeno je bilo, da vremensko pogojeni MP adsorbirajo več onesnaževal, adsorpcijsko obnašanje TCS pa se poveča v prisotnosti MeP. V četrti študiji je bila izvedena magnetna ekstrakcija čistih in vremensko spremenjenih delcev PE in TWP. Rezultati so potrdili, da je magnetna ekstrakcija vremensko spremenjenih MP v primerjavi s VIII prvotnimi MP težja, saj njihova površina z vremenskimi vplivi postane bolj hidrofilna. V peti študiji je bil ocenjen vpliv vremenskih vplivov na gostoto PE in PP. Ugotovili smo, da vremenske razmere povečajo gostoto poliolefinov, kar je eden glavnih razlogov za opaženo potapljanje poliolefinskih MP v vodi.
Sekundarne ključne besede: razgradnja plastike;pospešeno preperevanje;staranje;gostota;magnetna separacija;pigmenti;onesnaževala;polietilen;poliolefini;polipropilen;posedanje;delci gume iz obrabe pnevmatik;Umetne snovi;Disertacije;Onesnaževanje okolja;
Vrsta dela (COBISS): Doktorsko delo/naloga
Konec prepovedi (OpenAIRE): 2024-12-31
Komentar na gradivo: Univ. v Novi Gorici, Fak. za podiplomski študij
Strani: XIX, 149 str.
ID: 24009418