Aylin Altinisik

A natural sorbent, Luffa cylindrica for the removal of a model basic dye

In this work, application of Luffa cylindrica in malachite green (MG) removal from aqueous solution was studied in a batch system. The effect of contact time, pH and temperature on removal of malachite green was also investigated. By the time pH was increased from 3 to 5, the amount of sorbed malachite green also increased. Beyond the pH value of 5, the amount of sorbed malachite green remains constant. The fits of equilibrium sorption data to Langmuir, Freundlich and Dubinin-Radushkevich equations were investigated. Langmuir isotherm exhibited best fit with the experimental data. Monolayer sorption capacity increased with the increasing of temperature. Sorption kinetic was evaluated by pseudo-first-order, pseudo-second-order, Elovich rate equations and intraparticle diffusion models. It was inferred that sorption follows pseudo-second-order kinetic model. Thermodynamic parameters for sorption process were also found out. Spontaneous and endothermic nature of sorption was obtained due to negative value of free energy (DeltaG(o)) and positive value of enthalpy (DeltaH(o)) changes. FTIR analyses were also conducted to confirm the sorption of malachite green onto L. cylindrica.

Preparation of pH- and ionic-strength responsive biodegradable fumaric acid crosslinked carboxymethyl cellulose

A novel biodegradable sodium carboxymethyl cellulose (NaCMC)-based hydrogel was synthesized by using fumaric acid (FA) as a crosslinking agent at various ratios. Hydrogels (CMCF) were characterized using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Swelling behaviors of hydrogels were investigated in distilled water, various salt, and pH solutions. The FTIR results indicated the crosslinking between carboxyl groups of FA with hydroxyl group of NaCMC through ester formation. AFM analyses showed that roughness of hydrogel surface decreased with increasing crosslinker concentration. The swelling capacity decreased with an increase in charge of the metal cation (Al(3+)<Ca(2+)<Na(+)). In order to investigate reversible pH sensitivity of CMCF hydrogels, pH-dependent swelling was studied at pH 2 and 10. Reversible pH-responsiveness of CMCF hydrogels was achieved. CMCF hydrogels containing the greatest ratio of FA exhibited the longest biodegradation time with a half life of 21 h using cellulase.

Application of carboxymethylcellulose hydrogel based silver nanocomposites on cotton fabrics for antibacterial property

In this study, fumaric acid (FA) crosslinked carboxymethylcellulose (CMC) hydrogel (CMCF) based silver nanocomposites were coated on cotton fabric for antibacterial property for the first time. The performance of the nanocomposite treated cotton fabric was tested for different mixing times of hydrogel solution, padding times and concentrations of silver. The cotton fabrics treated with CMC hydrogel based silver nanocomposites demonstrated 99.9% reduction for both Staphylococcus aureus (Sa) and Klebsiella pneumonia (Kp). After one cycle washing processes of treated cotton fabric, there is no significant variation observed in antibacterial activity. From SEM and AFM analyses, silver particles in nano-size, homogenously distributed, were observed. The treated samples were also evaluated by tensile strength, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) analysis, fluid absorbency properties, and whiteness index. The treatment of cotton fabric with CMCF hydrogel did not affect the whiteness considerably, but increased the absorbency values of cotton.

Chitosan/poly(vinyl alcohol) hydrogels for amoxicillin release

Chitosan and poly(vinyl alcohol)-based hydrogel films were synthesized using tartaric acid as a crosslinking agent. The films denoted as CVT were then characterized using Fourier transform infrared, Nuclear magnetic resonance, X-ray diffraction, and scanning electron microscopy analysis. TG/DTG and DSC analysis were also carried out for the determination of thermal properties of hydrogel films. Swelling properties of these hydrogel films were investigated at two different pHs and temperatures. The swelling behaviors of all samples were increased in acidic medium, while decreased in alkaline medium. The enzymatic degradation of the hydrogels was studied using lysozyme, and degradation rates were found to be parallel with the swelling ratio for CVT hydrogel. The hydrogels were also used for the amoxicillin release in KCl/HCl and PBS buffer solutions. The release behaviors of CVT hydrogel films were slower and can be controlled as compared with commercial drug release systems. CVT hydrogel films may be more appropriate for controlled release of amoxicillin.

Evaluating of Agave americana fibers for biosorption of dye from aqueous solution

Fibers extracted from Agave americana were evaluated as a low cost sorbent for the removal of Malachite Green (MG) from aqueous solution. Agave fiber was characterized by using X-ray diffraction (XRD), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), and determining chemical content such as cellulose and hemicellulose. The crystallinity index and average size of crystals of agave fibers were obtained to be 53.29 % and 1.4 nm, respectively. The effects of temperature, amount of sorbent and ionic strength on biosorption behavior were investigated. By using Langmuir, Freundlich, and Dubinin-Radushkevich equations, equilibrium biosorption data were analyzed. Based on R2 values, the best fit was provided with Langmuir isotherm. The results showed that the largest biosorption capacity was obtained as 33 mg g−1 at 318 K. According to the thermodynamic studies, biosorption was determined to be endothermic and spontaneous in nature. Biosorption kinetics was investigated by equations such as Elovich rate equations, intraparticle diffusion models, pseudo-second-order, and pseudo-first-order models.