magistrsko delo
Ema Šušteršič (Author), Mojca Škerget (Mentor), Maja Čolnik (Co-mentor)

Abstract

Polimlečna kislina oz. PLA je popolnoma biološko razgradljiv polimer, ki velja za enega najbolj obetavnih polimerov na biološki osnovi in predstavlja odlično alternativo plastiki na osnovi nafte. Njen osnovni gradnik je mlečna kislina, ki nastane s fermentacijo sladkorjev pridobljenih iz obnovljivih virov. Namen magistrske naloge je bil preučiti recikliranje odpadne plastike iz PLA z uporabo podkritične vode, ki predstavlja zeleno in perspektivno tehnologijo. Preučili smo pridobitev tako glavnih (monomer PLA- mlečna kislina) kot tudi sekundarnih produktov (različne organske kisline). Eksperimente smo izvajali z dvema različnima materialoma PLA, in sicer osnovno PLA in odpadno PLA pri različnih temperaturah (180, 200, 250 in 300 °C), različnih reakcijskih časih (10, 20, 30 in 60 min) in v različnih atmosferah (dušik in zrak). Po reakciji razgradnje smo kot produkt dobili tri faze (trdno, vodno in plinasto fazo). V vseh primerih smo najvišje izkoristke dosegli v vodni fazi, medtem ko so se izkoristki trdne faze z zviševanjem temperature in reakcijskega časa, tekom reakcije razgradnje zniževali, izkoristki plinov pa naraščali. Glavni produkt razgradnje PLA je mlečna kislina, ki smo jo analizirali s HPLC metodo. Optimalni pogoji za pridobitev najvišje koncentracije mlečne kisline pri razgradnji osnovne PLA smo dosegli pri 250 °C in 30 min in je v zračni atmosferi znašala 43,6 mg/mL (87,2 %), medtem ko smo v dušikovi atmosferi pridobili malenkost nižjo koncentracijo mlečne kisline in sicer 43,4 mg/mL (86,6 %). Pri razgradnji odpadne PLA smo v vodni fazi zasledili nižje koncentracije mlečne kisline, saj odpadna PLA vsebuje tudi primesi in aditive, ki po reakciji ostanejo v trdnem ostanku. V vodni fazi smo v manjših koncentracijah pridobili tudi ocetno, mravljično, akrilno, oksalno in propanojsko kislino. Pri povišani temperaturi (300 °C) pa se mlečna kislina in sekundarni produkti pričnejo razgrajevati v pline. Vodni fazi smo določili tudi vsebnost totalnega ogljika (TC). Najvišjo koncentracijo TC smo določili pri razgradnji osnovne PLA (24,9 mg/mL) pri 250 °C in 30 min v zračni atmosferi . Na koncu smo s pomočjo FTIR analize okarakterizirali še trdni preostanek, ki je nastal po reakciji.

Keywords

bioplastika;polimlečna kislina (PLA);mlečna kislina;recikliranje;hidrotermična razgradnja;podkritična voda;magistrske naloge;

Data

Language: Slovenian
Year of publishing:
Typology: 2.09 - Master's Thesis
Organization: UM FKKT - Faculty of Chemistry and Chemical Engineering
Publisher: [E. Šušteršič]
UDC: 66.094.94:[628.477.6:678.7](043.2)
COBISS: 195527171 Link will open in a new window
Views: 114
Downloads: 6
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Other data

Secondary language: English
Secondary title: Chemical recycling of PLA plastic wastes by hydrothermal processes
Secondary abstract: Polylactic acid or PLA is a fully biodegradable polymer that is considered one of the most promising bio-based polymers and an excellent alternative to petroleum-based plastics. Its basic building block is lactic acid, which is produced by fermenting sugars obtained from renewable sources. The aim of the Masters thesis was to study the recycling of waste PLA plastic using subcritical water, which represents a green and promising technology. The recovery of both the main products (PLA monomer - lactic acid) and the secondary products (different organic acids) was investigated. The experiments were carried out with two different PLA materials, virgin PLA and waste PLA, at different temperatures (180, 200, 250 and 300 °C), different reaction times (10, 20, 30 and 60 min) and different atmospheres (nitrogen and air). After the decomposition reaction, three phases (solid, aqueous and gaseous) were obtained as products. In all cases, the highest yields were obtained in the aqueous phase, while the yields of the solid phase decreased with increasing temperature and reaction time during the decomposition reaction and the yields of the gases increased with increasing temperature and reaction time. The main product of PLA degradation is lactic acid, which was analysed by HPLC. In the case of virgin PLA, the optimum conditions for the highest lactic acid concentration were obtained at 250 °C for 30 min and it was 43.6 mg/mL (87, 2 %) in an air atmosphere, while a slightly lower lactic acid concentration of 43.4 mg/mL (86,6 %) was achieved in a nitrogen atmosphere. Lower lactic acid concentrations were observed in the aqueous phase during the degradation of PLA waste, as PLA waste also contains impurities and additives that remain in the solid residue after the reaction. Acetic, formic, acrylic, oxalic and propanoic acids were also obtained in the aqueous phase in lower concentrations. However, at higher temperatures (300 °C), the lactic acid and secondary products start to decompose into gases. The total carbon (TC) content of the aqueous phase was also determined. The highest TC concentration was determined when the virgin PLA (24.9 mg/mL) was decomposed for 30 min at 250 °C in an air atmosphere. Finally, the solid residue formed after the reaction was characterised by FTIR analysis.
Secondary keywords: bioplastics;polylactic acid (PLA);lactic acid;recycling;hydrothermal degradation;subcritical water;
Type (COBISS): Master's thesis/paper
Embargo end date (OpenAIRE): 2027-03-20
Thesis comment: Univ. v Mariboru, Fak. za kemijo in kemijsko tehnologijo
Pages: 1 spletni vir (1 datoteka PDF (49 f.))
ID: 23114480