Preparation of porous scaffolds for industrial dyes removal from aqueous solution

Sintetička bojila u velikoj su mjeri prisutna u otpadnim vodama industrije papira, tekstila i plastike. Mnoga bojila u svojoj strukturi sadrže aromatske prstene, što ih čini otrovnim i kancerogenim. S ciljem smanjenja rizika od onečišćenja okoliša, potrebno je tretiranje otpadnih voda prije ispusta u okoliš. Postoji nekoliko metoda koje se primjenjuju za uklanjanje bojila iz obojenih otpadnih voda poput koagulacije, oksidacije, adsorpcije, membranske filtracije i biološke obrade. Između tih tehnika, adsorpcija je okarakterizirana kao jedna od najučinkovitijih metoda zbog svoje jednostavnosti, isplativosti i energetske učinkovitosti. Iako postoje brojni nekonvencionalni jeftini adsorbensi koji se primjenjuju za uklanjanje bojila, velika je pozornost usmjerena prema polisaharidima poput kitozana. Ovaj biokompatibilni polimer posjeduje nekoliko karakteristika koje ga čine učinkovitim adsorbensom za uklanjanje bojila. U ovom radu pripravljeni su materijali na temelju kitozana kao polimerne biokompatibilne i biorazgradljive matrice i hidroksiapatita kao anorganske faze. Porozna struktura kitozana te kompozita postignuta je metodom toplinski inducirane fazne separacije uz geliranje i ekstrakciju. Sastav pripravljenih nosača utvrđen je rendgenskom difrakcijskom analizom i infracrvenom spektroskopijom s Fourierovim transformacijama. Morfologija materijala istražena je pomoću pretražnog elektronskog mikroskopa. Materijalima je određena poroznost, stupanj bubrenja te Youngov modul elastičnosti. Kitozan i njegov kompozit te aktivni ugljen kao kontrolni adsorbens korišteni su za uklanjanje bojila Congo Red iz vodene otopine. Provela se kinetička analiza adsorpcije i usporedila s kinetičkim modelima koji uobičajno opisuju proces adsorpcije. Regeneracija korištenih nosača se provela s ciljem ponovne upotrebe materijala nakon adsorpcije bojila. Synthetic dyes widely exist in the wastewaters of industries such as textiles, paper and plastics. Many dyes contain aromatic rings in their structures, which make them toxic and carcinogenic. In order to reduce risk of environmental pollution, it is necessary to treat the wastewaters before releasing them into the environment. There are several methods for dyes removal from colored wastewaters such as coagulation, oxidation, adsorption, membrane filtration and biological treatment. Among these techniques, adsorption is characterized as one of the most effective methods due to it's simplicity, cost and energy efficiency. There are numerous non-conventional low-cost adsorbent materials that are used for dye removal, however, special attention has been given to polysaccharides such as chitosan. This biocompatible polymer possesses several characteristics that make it an effective biosorbent for dye removal. Materials based on chitosan as biocompatible and biodegradable matrix and hydroxyapatite as inorganic phase were prepared in this study. Porous structures of chitosan and its composite has been obtained by freeze-gelation method. The composition of prepared scaffolds was carried out by X-ray diffraction analysis and Fourier-transform infrared spectroscopy. The morfology of materials was imaged by scanning electron microscopy. Chitosan and its composite and activated carbon as control adsorbent have been used as the adsorbents for removal of Congo Red dye from aqueous solution. The analysis of adsorption kinetics was carried out while behaviour of dye removal was evaluated by kinetic models that usually describe adsorption process. In order to reuse the materials after adsorption of Congo Red, regeneration of pre-adsorbed scaffolds was done.