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    Dissolution kinetics of ulexite in acetic acid solutions
    (Elsevier, 2008) Ekmekyapar, Ahmet; Demirkiran, Nizamettin; Kuenkuel, Asim
    Ulexite is an important boron mineral used for the production of boron compounds. The aims of this study are to examine the dissolution kinetics of ulexite in acetic acid solutions, and to present an alternative process to produce boric acid. In order to investigate the dissolution kinetics of ulexite in acetic acid solutions, the concentration of solution, reaction temperature, solid-to-liquid ratio, and particle size were selected as experimental parameters. It was determined that the dissolution rate of ulexite increased with increasing solution concentration and temperature and decreasing particle size and solid-to-liquid ratio. The activation energy of the process was found to be 55.8 kj/mol. (c) 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
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    Modeling the effect of physical crosslinking degree of pH and temperature responsive poly(NIPAAm-co-VSA)/alginate IPN hydrogels on drug release behavior
    (Elsevier, 2022) Balan, Kaan Emre; Boztepe, Cihangir; Kuenkuel, Asim
    There is a growing demand to design and development of hydrogel based stimuli responsive drug-delivery systems due to possess several advantages, namely high drug loading capacity, target specific delivery, biocompatibility, reduced drug toxicity and controlled drug release. Because their drug release behavior is dependent on many factors, it is very difficult to accurately characterize these behaviors. So, the characterization of drug loading and release behaviors is very important from an industrial and academic point of view. In this study, pH and temperature responsive poly(NIPAAm-co-VSA)/Alginate interpenetrating polymer network (IPN) hydrogel was synthesized by free radical polymerization in the presence of Poly(NIPA-co-VSA) nano gels. Na-Alginate natural polymer was used to physically cross-link the hydrogels with the Ca(2+ )ions. To obtain physically crosslinked hydrogel series at different rates, hydrogels were kept in various concentrations of CaCl2 solutions. The mechanical, chemical and morphological properties of obtained hydrogel series were characterized by compression test, FT-IR and SEM analysis techniques. As a result of the mechanical tests, it was determined that the fracture strengths varied between 137 and 830 kPa. The doxorubicin (DOX) loading capacities of the hydrogels were determined to be between 86 and 161 mg DOX/g polymer by the solution impregnation method. Their DOX release behavior have been investigated as a function of time, pH, temperature and physical cross -linking degree of hydrogel. Experimentally obtained and highly complex DOX release behaviors were success-fully modeled with the artificial neural network (ANN) technique.