Investigation of Lactic Acid Separation by Layered Double Hydroxide: Equilibrium, Kinetics, and Thermodynamics

The layered double hydroxide (LDH) with high crystallinity was prepared via the coprecipitation method for studying the separation equilibria of lactic acid. It was characterized by FTIR, XRD, and molecular size analyses. The effects of the amount of LDH, temperature, and initial lactic acid concentration on the separation process have been investigated. Results show that the maximum removal of lactic acid was obtained as 66.49% in the case of 1 g of LDH at 298 K. The isothermal data were fitted to Langmuir, Freundlich, and Temkin adsorption isotherms. Elovich, Lagergren, and pseudo-second-order kinetic model equations were applied. The experimental data were fitted with the Langmuir isotherm according to R-2, which is 0.9894 at 298 K, 0.9972 at 308 K, and 0.9998 at 318 K respectively. Separation depended on initial lactic acid concentration at investigated different temperatures (298 K, 308 K, 318 K) significantly. Standard free energy (Delta G degrees), enthalpy (Delta H degrees), and entropy (Delta S degrees) are calculated. The variation of several thermodynamic parameters was calculated according to thermodynamic analysis

Equilibrium, kinetics and thermodynamic studies for separation of malic acid on layered double hydroxide (LDH)

The adsorption equilibria of malic acid onto layered double hydroxide (LDH) was studied. In the experimental context of this study, firstly LDH with a highly crystalline structure was synthesized with the co-precipitation method and characterized. In the adsorption experiment some important effects such as, adsorption equilibrium, influence of quantities of LDH as adsorbent, effect of adsorption temperature, and influence of starting concentration of malic acid were investigated. The removal of malic acid was 96.73% the highest percentage for 1 g LDH at 298 K. The results obtained from the experiment were used to plot Langmuir, Freundlich, and Temkin adsorption isotherms. It has been found that experimental data about solid-liquid equilibria of malic acid with LDH and isotherm equations were appropriate. The equilibrium data show that the adsorption isotherm is compatible with Langmuir isotherm (R-2 is 0.9992 at 298 K). Adsorption depended on the starting malic acid concentration at various temperatures (298, 308,318 K), respectively. The temperature dependence of adsorption process is associated with changes in several thermodynamic parameters such as standard Gibbs energy (Delta G degrees), enthalpy (Delta H degrees) and entropy (Delta S degrees) of adsorption and were calculated. Elovich and other kinetic model equations were applied to the obtained data from the experiment. (C) 2014 Elsevier B.V. All rights reserved

Removal of Basic Dye from Aqueous Solutions Using a Novel Nanocomposite Hydrogel: N-Vinyl 2-Pyrrolidone/Itaconic Acid/Organo Clay

In this work, N-vinyl-2-pyrrolidone/itaconic acid/organo clay nanocomposite hydrogels were synthesized by free radical polymerization technique using different amounts of organo clay. Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy techniques were used for characterization of nanocomposite hydrogels and swelling, and mechanical properties of these hydrogels were investigated. Safranine-T adsorption capacities of nanocomposite hydrogels were investigated at different conditions such as pH, contact time, adsorbent dose and initial concentration of dye. The optimum pH value was found to be pH 6. According to the organo clay content, there are no significant differences in dye adsorption capacities of nanocomposite hydrogels until the clay content reaches 5 % wt. While the organo clay amount of nanocomposite hydrogels increases up to 10 % wt, dye adsorption capacities of these hydrogels significantly decrease. Adsorption processes of dye onto the nanocomposite hydrogels follow pseudo-second-order type adsorption kinetic. The equilibrium adsorption data have been evaluated using Freundlich and Langmuir Isotherm models. The results illustrated that the adsorption follows Langmuir isotherm

N-vinylcaprolactam-based microgels: synthesis, characterization and drug release applications

In this study, N-vinylcaprolactam, metacrylic acid sodium salt and itaconic acid sodium salt-based copolymeric and terpolymeric microgels were synthesized by precipitation polymerization method with 2,2'-azobis(2-methylpropioamidine) dihydrochloride as initiator. Then these microgels were characterized by SEM technique, cloud points and colloidal properties determinations. Volume phase transitions of copolymeric and terpolymeric N-vinylcaprolactam-based microgels are determined at an interval of 32-37 A degrees C. Rhodamine B (model drug) and Nadalol (beta-blocker drug) were used to investigate the drug loading and release behavior of microgels. It is concluded that model drug loading capacity and release amount changed with the presence and amount of itaconic acid sodium salt in the microgel structure. In addition, the maximum drug release amount of microgels was found to be 58 and 55 % for Rhodamine B and Nadolol, respectively. As a result, we can say that the microgels obtained in this study are suitable for drug delivery applications

Swelling, mechanical and mucoadhesion properties of Mt/starch-g-PMAA nanocomposite hydrogels

Novel mucoadhesive montmorillonite/starch-graft-poly (methacrylic acid) nanocomposite hydrogels (Mt/S-g-PMAA) based on gelatinized wheat starch, an anionic monomer methacrylic acid (MAA), and different amounts of montmorillonite (Mt) as nanoparticles were synthesized according to the conventional grafting reaction mechanism in the aqueous media. The grafting amount of the products (G%) was determined. The formation of Mt/S-g-PMAA was confirmed by FTIR and XRD analyses. The swelling behavior and the erosion characteristics of the Mt/S-g-PMAA were investigated in deionized water, and pH = 5 lactate buffer solution as in vitro vaginal medium at 37 +/- 0,1 degrees C. Mechanical and in vitro mucoadhesion properties of all Mt/S-g-PMAA were also investigated using ewe vaginal mucosa. The results show that adding a higher amount of Mt could effectively increase the mucoadhesion properties of the clay mineral-polymer nanocomposite (CPN) hydrogels. It is then concluded that the 10Mt/S-g-PMAA may be used as alternative highly mucoadhesive CPN hydrogel drug carrier for vaginal route. (C) 2015 Elsevier B.V. All rights reserved

Study on novel exfoliated polyampholyte nanocomposite hydrogels based on acrylic monomers and Mg-Al-Cl layered double hydroxide: Synthesis and characterization

Novel exfoliated polyampholyte nanocomposite hydrogels (NH-LDHs) based on acrylic acid (AA), 2(diethylamino) ethyl methacrylate (2-DEAEMA), N,N-methylenebisacrylamide (NMBA) and layered double hydroxide (Mg-Al-CI LDH) were synthesized using an in situ free radical addition polymerization method in aqueous media. First, Mg-Al-CI LDH with a highly crystalline structure was prepared and characterized using FTIR, XRD, TGA and SEM analyses. The formation of NH-LDHs was confirmed by FTIR and XRD analyses. The morphological structure and select properties, such as the thermal, swelling and mechanical properties, of the NH-LDHs were also investigated. NH-LDHs have an exfoliated structure and smooth and nonporous surface morphologies. They can also be used as thermally stable nanocomposite hydrogels. The results revealed that adding a small amount of exfoliated Mg-Al-CI LDH could effectively increase the compressive modulus of the polyampholyte gels. When the Mg-Al-CILDH was incorporated into the polyampholyte hydrogel matrix, two synergic effects, additional co-crosslinking and additional hydrophilicity, occur in the swelling behaviors of the gels. All NH-LDHs are sensitive to pH, and they have zwitterion characteristics at pH 5.5. It was concluded that the NH-LDHs synthesized in this study might be used as alternative water absorbents in solutions with different pH. The diffusion of water into the NH-LDHs gel systems in deionized water at room temperature is assumed to be a non-Fickian behavior. (C) 2013 Elsevier B.V. All rights reserved

Chemıstry, Applıed

10.1016/j.carbpol.2015.08.079The aim of this study was to prepare and evaluate the mucoadhesive, biocompatible and biodegradable progesterone containing vaginal tablets based on modified starch copolymers for the estrus synchronization of ewes. Starch-graft-poly( acrylic acid) copolymers (S-g-PAA) were synthesized and characterized. The vaginal tablets were fabricated with S-g-PAA and their equilibrium swelling degree (Qe) and matrix erosion (ME%) were determined in lactate buffer solution. In vitro, mucoadhesive properties of the tablets were investigated by using ewe vaginal mucosa and in vivo residence time were also investigated. In vitro and in vivo progesterone release profiles from the tablets were compared with two commercial products. Tablet formulation containing wheat starch based grafted copolymer (WS-g-PAA)(gc) indicated promising results and might be convenient as an alternative product to the commercial products in veterinary medicine. (C) 2015 Elsevier Ltd. All rights reserved

Development of starch based mucoadhesive vaginal drug delivery systems for application in veterinary medicine

The aim of this study was to prepare and evaluate the mucoadhesive, biocompatible and biodegradable progesterone containing vaginal tablets based on modified starch copolymers for the estrus synchronization of ewes. Starch-graft-poly( acrylic acid) copolymers (S-g-PAA) were synthesized and characterized. The vaginal tablets were fabricated with S-g-PAA and their equilibrium swelling degree (Qe) and matrix erosion (ME%) were determined in lactate buffer solution. In vitro, mucoadhesive properties of the tablets were investigated by using ewe vaginal mucosa and in vivo residence time were also investigated. In vitro and in vivo progesterone release profiles from the tablets were compared with two commercial products. Tablet formulation containing wheat starch based grafted copolymer (WS-g-PAA)(gc) indicated promising results and might be convenient as an alternative product to the commercial products in veterinary medicine. (C) 2015 Elsevier Ltd. All rights reserved