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    Controlled release behavior of zinc-loaded carboxymethyl cellulose and carrageenan hydrogels and their effects on wheatgrass growth
    (Springer, 2019) Akalın, Gülen Oytun; Pulat, Mehlika
    Sodium carboxymethyl cellulose (NaCMC) and carrageenan (CG) hydrogels were synthesized for potential use in the growth of wheatgrass plant. The water absorbency and gel content properties of prepared hydrogels were investigated. Water absorbency was reduced with increasing the amounts of polymer and crosslinker, in contrast with gel content results. The treatment of hydrogels with soil enhanced the water retention capacity of soil. Zinc micronutrient was loaded in both hydrogels by classic entrapment method. The zinc release behavior of hydrogels in water and soil were determined and the release rate decreased with high gel content and crosslinking density. The influence of zinc-loaded hydrogel on the wheatgrass plant performance were also investigated by using pot experiments. The growth of the wheatgrass (Triticum aestivum) was obviously increased by the use of zinc-loaded hydrogels. The increase in plant performance by using these hydrogels suggests that prepared hydrogels can be used as a controlled fertilizer system in agriculture fields.
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    Preparation and characterization of K-carrageenan hydrogel for controlled release of copper and manganese micronutrients
    (Springer Verlag, 2020) Akalın, Gülen Oytun; Pulat, Mehlika
    A series of ?-carrageenan (?-CG) hydrogels were prepared by using glutaraldehyde (GA) as crosslinker for controlled releasing of copper and manganese micronutrients. The hydrogels were characterized by gel content, swelling and degradation tests, Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) and Scanning Electron Microscope (SEM) observations. The variations of swelling percentages (S%) with time, temperature and pH were determined for all hydrogels. As the amounts of crosslinker increased, S% decreased regularly in contrast to gel content results. The higher swelling values were obtained in basic medium than acidic and neutral mediums for all ?-CG hydrogels. Releasing of copper and manganese micronutrients from ?-CG hydrogels was investigated in water and soil. A simulated releasing model was also applied to estimate the releasing behaviors in agricultural irrigations. In all release studies, the cumulative release values increased with decreasing GA amounts. The release kinetic parameters were also calculated. It was detected that the releasing of micronutrients in soil was slower than that in water. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.
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    Preparation and characterization of nanoporous sodium carboxymethyl cellulose hydrogel beads
    (Hindawi Publishing Corporation, 2018) Akalın, Gülen Oytun; Pulat, Mehlika
    A series of nanoporous sodium carboxymethyl cellulose (NaCMC) hydrogel beads were prepared using FeCl3 ionic crosslinker by changing polymer and crosslinker percentages (%). Characteristics of the hydrogels were investigated by gel content, swelling test, degradation test, Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR), Scanning Electron Microscope/Energy Dispersive X-ray Analysis (SEM/EDX), and Atomic Force Microscopy (AFM). Swelling experiments were studied by changing time, temperature, and pH. The swelling percentage (S%) regularly decreased with increasing the amounts of polymer and crosslinker, in contrast with gel content results. NaCMC hydrogels were found to be sensitive to pH variations. The degradation test showed that hydrogels had good stability and their degradation period varied from 30 to 36 days. According to SEM analysis, NaCMC hydrogels had mostly nanoporous structure. The average granule and pore sizes of the least swollen NaCMC-12 hydrogel were found to be 13.1 +/- 0.3nm and 82.1 +/- 3.2 nm. The elemental compositions of hydrogels were determined with EDX. The minimum average surface roughness (R-a) and root mean square roughness (R-ms) parameters were found to be 15.7 +/- 1.9nm and 20.3 +/- 2.2nm for NaCMC-12 hydrogels by AFM. Due to their good morphologies, stabilities, and swelling behaviors, NaCMC hydrogels can be suitable for biomaterial applications.