Yoldas Seki

Removal of malachite green by using an invasive marine alga Caulerpa racemosa var. cylindracea

The biosorption of a cationic dye, malachite green oxalate (MG) from aqueous solution onto an invasive marine alga Caulerpa racemosa var. cylindracea (CRC) was investigated at different temperatures (298, 308 and 318 K). The dye adsorption onto CRC was confirmed by FTIR analysis. Equilibrium data were analyzed using Freundlich, Langmuir and Dubinin-Radushkevich (DR) equations. All of the isotherm parameters were calculated. The Freundlich model gave a better conformity than Langmuir equation. The mean free energy values (E) from DR isotherm were also estimated. In order to clarify the sorption kinetic, the fit of pseudo-first-order kinetic model, second-order kinetic model and intraparticle diffusion model were investigated. It was obtained that the biosorption process followed the pseudo-second-order rate kinetics. From thermodynamic studies the free energy changes were found to be -7.078, -9.848 and -10.864 kJ mol(-1) for 298, 308 and 318 K, respectively. This implied the spontaneous nature of biosorption and the type of adsorption as physisorption. Activation energy value for MG sorption (E(a)) was found to be 37.14 kJ mol(-1). It could be also derived that this result supported physisorption as a type of adsorption.

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.

The Mechanical Properties of γ-Methacryloxypropyltrimethoxy silane-treated Jute/Polyester Composites:

In this study, jute/polyester composites were fabricated. To improve the adhesion between jute fabric and polyester alkali-treated jute fabrics were treated with γ-methacryloxypropyltrimethoxysilane (γ-MPS). The effect of silane concentrations (0.1%, 0.3%, and 0.5%) on tensile properties, flexural properties, and interlaminar shear strength was investigated. Once jute fabrics were treated with 0.1% and 0.3% silane concentrations, the tensile properties of silane-treated jute polyester composites increased. However, when 0.5% γ-MPS was used in silane treatment, the tensile properties of jute/polyester composites decreased. 0.3% silane-treated jute/polyester composites exhibited superior improvements in terms of the flexure properties among the fabricated composites. Interlaminar shear strength measurements showed that best adhesion was provided by using 0.3% silane-treated jute/polyester composites. Good adhesion between silane-treated jute fabric and polyester was also confirmed by scanning electron microscope observations.

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.

The effect of argon and air plasma treatment of flax fiber on mechanical properties of reinforced polyester composite

Flax fibers were modified by argon and air atmospheric pressure plasma treatments to improve the mechanical properties of flax fiber-reinforced unsaturated polyester composites. Plasma treatments were carried out at plasma powers of 100, 200, and 300 W. Both plasma surface treatments were conducted to improve the tensile strength, tensile modulus, flexural strength, flexural modulus, interlaminar shear strength (ILSS), Mode I interlaminar fracture toughness (GIC), and Mode II interlaminar fracture toughness (GIIC). Moreover, the maximum improvement in the mechanical properties was obtained after air plasma treatment of flax fiber at a plasma power of 300 W. Tensile strength, flexural strength, ILSS, GIC, and GIIC values of flax fiber-reinforced polyester composites increased by nearly 34%, 31%, 39%, 35%, and 42%, respectively. However, for argon plasma-treated flax fiber-reinforced polyester composites, the mechanical properties of composite increased up to argon plasma power of 200 W.

Variations of mechanical properties of jute/polyester composite aged in various media

Woven roving jute fiber-reinforced unsaturated polyester composites were subjected to water absorption tests in order to study the effects of water ageing on the mechanical properties. Composite specimens were immersed in distilled water and salt water up to 2736 h. The water absorption of specimens reached to an equilibrium level after an immersion time of 300 h. It was observed that tensile, flexural, and interlaminar shear strengths (ILSSs) of jute/polyester composites decreased depending on the immersion time. The ILSS values of the composites were reduced by more than 53% for both the distilled water and the salt water after an immersion time of 2736 h.

Effect of siloxane treatment of jute fabric on the mechanical and thermal properties of jute/HDPE

The mechanical and thermal properties of jute fiber/HDPE composites as a function of alkali and oligomeric siloxane treatment of jute fabric were investigated. The effect of surface treatments on the composites was assessed by means of tensile test, short-beam shear test, three-point bending test, SEM, TGA, and DSC. When jute fabric are first treated with alkali solution and then oligomeric siloxane solution, 34% and 49% increases in tensile and flexural strength were observed, respectively. Moreover, it is interesting to note that after alkali and siloxane treatment of jute fabric, 169% increase in ILSS of jute/HDPE composite was obtained. This demonstrates that the adhesion between jute fiber and HDPE matrix is greatly increased by alkali and oligomeric siloxane treatment of jute fabric. This observation was also confirmed by SEM analysis of fracture surface of composites. Alkali and oligomeric siloxane treatment of jute fabric did not considerably change thermal stability and melting and crystallization temperatures of jute/HDPE.

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.

Mechanical anisotropy in unidirectional glass fabric reinforced oligomeric siloxane modified polyester composites

In this study, the effect of incorporation of oligomeric siloxane into unsaturated polyester on mechanical behavior of unidirectional glass fiber/polyester composites has been investigated by means of tensile, flexural and short beam shear tests. The amount of oligomeric siloxane added into unsaturated polyester was in the range 1–3 % by weight of the glass fabrics. Mechanical tests were conducted at different angles (0 °, 45 °, and 90 °) with respect to fiber direction. The higher siloxane content exhibited a tendency to have greater tensile, flexural and interlaminar shear strength values in machine direction, bias direction and cross direction. From Scanning electron microscopy images, the presence of polyester particles on the unidirectional glass fiber surface confirmed better adhesion.