magistrsko delo
Maja Mazej (Avtor), Selestina Gorgieva (Mentor), Alenka Ojstršek (Komentor)

Povzetek

Vse večja rast prebivalstva in razvoj industrije sta močno vplivala na povečano porabo vode. Velik problem pri tem pa predstavljajo predvsem obarvane odpadne vode v tekstilni industriji, ki so zelo obremenjene in predstavljajo ob izpustu veliko obremenitev za okolje. Odstranjevanje barvil iz odpadnih vod, zaradi kompleksnih molekulskih struktur predstavlja velike izzive industriji. Tako so želje po ponovni uporabi spodbudile razvoj novih tehnologij, ki bi na učinkovit in cenovno ugoden način te vode pred izpustom v vodotok tudi ustrezno prečistile. Že predhodne raziskave so pokazale, da je ena izmed učinkovitejših fizikalnih metod ločevanja barvil membranska adsorpcija. Magistrsko delo predstavlja preučitev različnih možnosti in načinov, s katerimi bi uspešno ločili kationska barvila iz modelnih odpadnih vod z uporabo membranskih adsorbentov na osnovi celuloznih nanofibrilov in pektina. Cilj magistrskega dela je bil sinteza cenovno – učinkovitih, okolju prijaznih membran, na osnovi nanofibrilirane celuloze in pektina, na osnovi enostavnih postopkov mešanja, vlivanja in sušenja z dodatkom citronske kisline (CA) in CaCl2 kot zamreževalca. Različne strukturirane membrane smo primarno okarakterizirali glede na njihove morfološke in fizikalno-kemijske lastnosti, ter sekundarno glede na njihove adsorpcijske lastnosti, na podlagi katerih smo preučili mehanizme in učinkovitost adsorpcije. Pri tem smo pridobili membrane, ki bi lahko uspešno vplivale na ločitev kationskih barvil iz vodnih medijev. Gravimetrična analiza membran nam je podala zaključek, da so vse membrane na osnovi mešanic primarnih surovin brez dodanih zamreževalcev neobstojne v vodi, zato je dodatek zamreževalcev ključnega pomena. Opazili smo, da membrana formirana le iz CNFjev, ne potrebuje zamreževalca, saj je samostojno obstojna v vodi, kar pa gre pripisati intenzivnemu in ireverzibilnemu povezovanju nanofibrilov pri procesu sušenja, v odsotnosti drugih komponent. Z ATR – FTIR spektroskopijo smo ugotovili, da obe vrsti zamreževalca, tako CA kot CaCl2, naredita spremembo v kemijski strukturi, in prispevata k določeni meri stabilizacije in s tem nakazujeta na uspešno ionsko (CaCl2), ter kovalentno (CA) vezavo. Z rezultati, pridobljenimi pri potenciometrični titraciji, smo ugotovilii, da dosežejo največji skupni naboj tiste membrane, ki vsebujejo zamreževalec CA. K doseganju največjega naboja membrane je prispevala predvsem prisotnost karboksilnih skupin, ki tudi vplivajo na večjo adsorpcijsko sposobnost membran. Izmerjene vrednosti z goniometrijo pri vseh membranah so bile nižje od 90° in kažejo na izrazito hidrofilnost membran, saj osnovne komponente vsebujejo hidrofilne hidroksilne, ter karboksilne skupine. Z optično mikroskopijo smo membrane le makroskopsko opazovali in zaključili, da imajo membrane izotropne strukture, brez preferenčne ureditve. Z rezultati gravimetričnega določanja % nabrekanja smo ugotovili, da zamreževalec pozitivno vpliva na ohranjanje strukture membrane v vodi. Pektin pa očitno vpliva na nestabilnost (karboksilne skupine, ob stiku z vodo dezintegrirajo), če primerjamo membrane z dodanim pektinom in membrano 10, ki ima vključen samo CNF. Z analizo adsorpcije barvil (UV-VIS spektrokoskopija) vidimo uspešno adsorpcijo obeh barvil Basic Yellow 28 kot tudi Basic Blue 22 v različnih koncentracijah na membrane. Najbolj uspešen primer navzemanja barvila je v primeru CNF/PC membran, ker ima pektin naboj, ki omogoča uspešno vezavo barvila. Dokazali smo tudi uspešno navzemanje barvila na membrane, pri obeh vrstah barvila. Odstotek razbarvanja kopeli se razlikuje glede na koncentracije v primeru najnižje koncentracije in najmanjše razbarvanje v primeru najvišje koncentracije, kar velja za vse membrane. Adsorpcija barvil je pogojena s kemijsko strukturo ter mikrostrukturo membrane, ki se uporabi kot adsorbent.

Ključne besede

celulozni nanofibrili;pektin;zamrežanje;membrana;membranska adsorpcija;kationska barvila;magistrske naloge;

Podatki

Jezik: Slovenski jezik
Leto izida:
Tipologija: 2.09 - Magistrsko delo
Organizacija: UM FS - Fakulteta za strojništvo
Založnik: [M. Mazej]
UDK: 544.725/.726:628.316.12(043.2)
COBISS: 151194627 Povezava se bo odprla v novem oknu
Št. ogledov: 176
Št. prenosov: 39
Ocena: 0 (0 glasov)
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Ostali podatki

Sekundarni jezik: Angleški jezik
Sekundarni naslov: Development of cellulose-pectin based membranes for adsorption of cationic dyes from model solutions
Sekundarni povzetek: Increasing population growth and industrial development have substantially impacted increased water consumption. A significant problem here is mainly coloured wastewater in the textile industry, which is heavily loaded and burdens the environment when discharged. The removal of dyes from wastewater, due to their complex molecular structures, presents significant challenges to the industry. The desire for reuse has encouraged the development of new technologies that would effectively and affordably purify this water before it is released into the watercourse. Previous research has shown that membrane adsorption is one of the more effective physical methods of dye separation. The master's thesis examines various possibilities and ways to successfully separate cationic dyes from model wastewater using membrane adsorbents based on cellulose nanofibrils and pectin. The goal was the synthesis of cost-effective, environmentally friendly membranes based on nanofibrillated cellulose and pectin, based on simple mixing, casting and drying procedures with the addition of citric acid (CA) and CaCl2 as crosslinkers. The various structured membranes were primarily characterised according to their morphological and physicochemical properties, based on which we studied the mechanisms and efficiency of adsorption. In doing so, we obtained membranes that could successfully influence the separation of cationic dyes from aqueous media. The gravimetrical characterization of the membranes made us conclude that all membranes based on mixtures of primary raw materials without added crosslinkers are unstable in water, so the addition of crosslinkers is crucial. We noticed that the membrane formed only from CNFs does not need a crosslinker, as it is independently stable in water, which can be attributed to the intense and irreversible linking of nanofibrils during the drying process in the absence of other components. With ATR - FTIR spectroscopy, we identified that both types of crosslinkers, CA and CaCl2, change the chemical structure and contribute to a certain degree of stabilization, thus indicating successful ionic (CaCl2) and covalent (CA) crosslinking. With the results obtained in the potentiometric titration, we found that the maximum total value of that membrane containing the CA crosslinker was reached. The presence of carboxyl groups, which also affects the membrane's greater adsorption capacity, contributes to achieving the maximum membrane charge. The values measured by goniometry for all membranes were lower than 90° and indicate a pronounced hydrophilicity of the membrane since the essential components contain hydrophilic hydroxyl and carboxyl groups. We only observed the membranes macroscopically with optical microscopy and concluded that the membranes have isotropic structures without preferential arrangement. With the results of the gravimetric determination of % swelling, we found that the crosslinker has a positive effect on maintaining the structure of the membrane in water. However, pectin affects the instability (carboxyl groups disintegrate upon contact with water) if we compare membranes with added pectin and membrane 10, which only has CNF included. By analyzing the adsorption of dyes (UV-VIS spectroscopy), we see the successful adsorption of both dyes, Basic Yellow 28 as well as Basic Blue 22, in different concentrations on the membranes. The most successful example of dye uptake is in the case of CNF/PC membranes because pectin has a charge that enables successful binding of the dye. We also demonstrated the successful dye uptake on the membranes with both types of dye. The percentage of bath decolourization varies with concentrations in the case of the lowest concentration and the least decolourization in the case of the highest concentration, which is valid for all membranes. Adsorption of dyes is conditioned by the chemical structure and microstructure of the membrane, which is used as an adsorbent.
Sekundarne ključne besede: cellulose nanofibrils;pectin;crosslinking;membrane;membrane adsorption;cationic dyes;
Vrsta dela (COBISS): Magistrsko delo/naloga
Komentar na gradivo: Univ. v Mariboru, Fak. za strojništvo, Tehniško varstvo okolja
Strani: 1 spletni vir (1 datoteka PDF (XVIII, 78 f.))
ID: 17703508