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    A research on antioxidant activity evaluation of waste lignocellulosic biomass: optimization using response surface methodology
    (Sivas Cumhuriyet Üniversitesi, 2020) Meryemoğlu, Bahar; Kaya, Burçak; Niş, Berna
    In the present study, lignocellulosic biomass such as corn straw and sorghum were used as raw materials for a new, abundant, low-cost and natural antioxidant source to use in foods or medicinal materials as replacements for synthetic antioxidants such as butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT). The effect of extraction temperature, extraction time, solvent volume on extraction yield, total phenol content and antioxidant activity were investigated and the results obtained by response surface methodology (RSM) were evaluated. Linear and quadratic models were revealed as a result of experiments. The fit of these models with predictions results were tested and optimal condition parameters were investigated. It was seen that different results were obtained because of structural differences between corn straw and sorghum. These results showed that the extraction temperature was the main positive linear effect on extraction yield. The solvent volume and temperature were found to important model terms for total phenol content. For antioxidant activity, the solvent volume was the main linear effect for sorghum where as it has a quadratic effect for corn straw biomass.
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    Fabrication of Carbonaceous-Modified Halloysite Nanotubes for the Removal of Metal Ions from Aqueous Solution
    (2023) Meryemoğlu, Bahar; Özsel, Burcak; Niş, Berna
    Halloysite nanotube-carbonaceous (HNT-C) composites were fabricated through one-pot hydrothermal carbonization of fructose and sodium carboxymethyl cellulose for use as an adsorbent for the removal of Pb(II), Zn(II), and Cu(II) from wastewater. The composites were chemically treated with sulfuric acid after carbonization. The acidic treatment of HNT-C structures contributed to a larger specific surface area and surface functionality, which was favorable for adsorbing more metal ions. Carbonaceous-modified HNTs were characterized by elemental analysis, FT IR, XRD, and BET analysis. Metal ion adsorption experiments were conducted with solutions containing low and high total metal ion concentrations (Cu, Zn, Pb) by mixing with HNT-C composites at a solid/liquid ratio of 1.0 and 10.0 g/L. The results indicated that the HNT C composites exhibited promising Zn(II) adsorption up to 94%, while no Zn(II) adsorbed onto unmodified HNTs. The amount of Pb(II), Zn(II), and Cu(II) ions that were taken up increased as the amount of adsorbent was increased up to 10 g/L in an aqueous solution. The HNT-C composites exhibited the highest adsorption efficiency for Pb(II) ions.