Recycling of blended textile materials

V zadnjih desetletjih je zaradi vse višjega življenjskega standarda ter globalne rasti prebivalstva, močno narastla tudi količina proizvedenih in uporabljenih tekstilnih materialov. Posledično se je povečala tudi količina odpadnega tekstila, upravičeno pa lahko sklepamo, da bo le-ta v prihodnjih letih le še naraščala. Po ocenah strokovnjakov naj bi na odlagališčih odpadkov končalo kar 70 % odpadnih tekstilnih materialov, vsi ti nepredelani odpadki pa predstavljajo ogromen neuporabljen vir sekundarnih surovin in negativni ogljični odtis za okolje. V magistrski nalogi smo se lotili raziskovanja možnosti kemijskega recikliranja tekstilnega materiala bombažnega, volnenega in poliestrnega izvora, oziroma tekstilnih mešanic omenjenih komponent. Odločili smo se za izbiro kemikalij in pogojev, s katerimi bi dosegli čim višjo učinkovitost, hkrati pa bi bil postopek še vedno čim bolj ekološko in ekonomsko sprejemljiv. Razgradnjo naravnih vlaken (bombaža in volne) smo tako izvajali z uporabo H3PO4 (fosforjeve (V) kisline). Pri tem smo razmišljali tudi o nadaljnji uporabi produkta, ki bi ga še posebej zaradi prisotnosti fosforjevih ionov lahko uporabili v pridelavi umetnih gnojil. Za razgradnjo poliestrnega materiala smo uporabili proces nevtralne hidrolize pri dveh različnih razmerjih med poliestrom in vodo. Pri tem smo dosegli depolimerizacijo poliestra (PET) do osnovnih gradnikov: tereftalne kisline (TK) in etilen glikola (EG). Izvedbi reakcije razgradnje eno-komponentnih materialov je sledilo ločevanje dvo-komponentnega materiala, ki je bil sestavljen iz kombinacije bombaža in poliestra oziroma volne in poliestra. Razgradnjo naravnih vlaken ter ločevanje tekstilnih komponent smo izvajali v steklenem reaktorju, medtem ko smo za nevtralno hidrolizo poliestra uporabili posebej v ta namen izdelan visokotlačni in visokotemperaturni reaktor. Na podlagi raziskave smo ugotovili, da lahko z uporabo H3PO4 kisline uspešno razgradimo naravna vlakna, kot sta bombaž in volna, največji vpliv na izkoristek reakcije pa imata izbrana koncentracija kisline in reakcijski čas. Podobno smo ugotovili tudi pri eksperimentih ločevanja mešanic omenjenih naravnih vlaken s poliestrom, v katerih je poliestrni material ostal kemijsko nespremenjen. Na osnovi rezultatov nevtralne hidrolize smo ugotovili, da je mogoče PET zgolj s pomočjo vode, povišane temperature in tlaka depolimerizirati do osnovnih enot. Po prečiščenju trdega reakcijskega produkta smo pridobili tereftalno kislino (TA) visoke čistosti. Ugotovili smo, da na izkoristek nevtralne hidrolize vplivata tako čas reakcije, kot tudi razmerje med PET materialom in vodo, ki posledično vpliva tudi na delovni tlak v sistemu.Due to higher living standards and global population growth in recent decades, the quantity of produced and used textile materials has grown significantly . Consequently, the amount of waste textiles has also increased, and can be reasonably inferred that in the coming years the later will continue to rise. According to experts, today 70 % of waste textile materials ends up in landfills. All of these unprocessed wastes represent a huge unused source of secondary raw materials and negative carbon footprint for the environment. In this thesis we started to explore the possibilities of chemical recycling of different single component textile materials: cotton, wool and polyester and textile mixtures of these components. We opted for the choice of chemicals and conditions in order to achieve the highest possible efficiency, while the process would still be the most ecologically and economically acceptable. Degradation of natural fibers (cotton and wool) was carried out using H3PO4 (phosphoric (V) acid). In doing so, we also considered further use of these waste products that could be used in the production of fertilizers, particularly due to the high amount of phosphorous ions present. For the depolymerization of polyester a process of neutral hydrolysis was selected. This process only uses water, high temperature and pressure for depolymerization of PET to the basic components: terephthalic acid (TPA) and ethylene glycol (EG). Reactions of decomposition of single-component materials were followed by separation of the two-component material, which has been assembled from a combination of cotton and polyester, or of wool and polyester. Degradation of natural fibers and separation of the textile components were performed in a batch glass reactor, while the neutral hydrolysis of the polyester was performed in high-temperature and pressure reactor, which was designed especially for this purpose. Based on research, we found that natural fibers such as cotton and wool can be successfully degraded using H3PO4. Concentrations of selected acid and reaction time have the greatest impacts on the yield of reactions. Similarly, we also observed in the experiments of separating blends of these natural fibers with polyester, in which the polyester remained chemically unmodified. On the basis of the results of neutral hydrolysis, we found that PET can be depolymerized to basic units using only water, elevated temperature and high pressure. After purification of crude reaction product, terephthalic acid (TA) of high purity was obtained. We have found that the yield of neutral hydrolysis reactions is influenced by both the reaction time, as well as the ratio between PET material and water, which in turn affects the working pressure in the system