Tuning a green carboxymethyl cellulose-based pre-tanning agent via peroxide oxidation for high chrome exhaustion in leather industry.

The low chrome uptake by collagen in the conventional tanning process leads to the pollution of the wastewater. Due to environmental concerns, leather scientists are already searching for innovative ways to produce pre-tanning agents as a high exhaustion chrome tanning auxiliary. Herein, a novel kind of pre-tanning agent is engineered by converting carboxymethyl cellulose (CMC) to oxidized carboxymethyl cellulose (OCMC) via the hydrogen peroxide process. FT-IR and carboxyl content analysis demonstrated the increase in carboxyl content after oxidation. After that, the obtained OCMC was utilized as a pre-tanning agent, resulting in a high exhaustion of chrome (92.76 %) which is 27.76 % more than conventional chrome tanning (65 %), and the amount of chrome in wastewater reduced to 7.24 %. The hydrothermal stability of wet-blue increased by increasing the uptake of chrome (Ts = 118 °C). The obtained crust leather represented excellent mechanical properties (Tensile strength: 305.68 kg/cm2; tear strength: 50 kg/cm) and desirable organoleptic properties. The environmental analysis signifies a significant step towards a cleaner and sustainable tanning process (COD = 1600, BOD5 = 560 mg/L) compared to the conventional chrome tanning process. Consequently, the obtained results offer a green pre-tanning agent to meet the requirements of the sustainable development of the leather industry.

Fabrication of magnetic nanocomposite scaffolds based on polyvinyl alcohol-chitosan containing hydroxyapatite and clay modified with graphene oxide: Evaluation of their properties for bone tissue engineering applications.

One of the most common systems for bone tissue engineering is polymeric scaffolds. However, the low mechanical properties of polymeric scaffolds, considering the properties required for bone replacement tissue, are the main challenge for researchers in this field. For bone tissue engineering, this research prepared nanocomposite scaffolds based on polyvinyl alcohol-chitosan containing modified clay and hydroxyapatite (HAp). HAp used in these 3D scaffolds was synthesized from a chicken femur, and Cloisite 30B clay nanoparticles were modified by graphene oxide and Fe3O4 nanoparticles to strengthen their mechanical properties. Sample characteristics were determined using FT-IR, XRD, SEM, TGA, swelling rate, laboratory degradation, and biological and mechanical properties. These analyses showed that 2% of modified clay (C30B/GO/Fe3O4, CGF) inside the nanocomposite scaffold increased the compressive strength 23 times compared to the pristine polymer scaffold. Also, adding HAp particles and modified clay simultaneously increased the mineralization on the surface of the scaffolds. Final nanocomposite scaffolds were found to have a compressive strength of 9.31 MPa, a porosity of 75 %, and a porosity size of 50 nm and were in the range of cancellous bone. The final swelling amount is 1790 %, which is the amount that is Favorable for bone scaffold. Finally, the analysis results to determine the samples' toxicity showed that none of the prepared scaffolds were toxic and showed good cell viability.

Modified gelatin/iron- based metal-organic framework nanocomposite hydrogel as wound dressing: Synthesis, antibacterial activity, and Camellia sinensis release.

A new kind of Camellia sinensis-loaded nanocomposite hydrogel based on modified gelatin/iron-metal-organic framework was developed as an antibacterial wound dressing. Gelatin as a biocompatible natural polymer was modified with methacrylate anhydride to produce gelatin methacrylate. Thereafter, acrylic acid and acrylamide were grafted on gelatin methacrylate during an aqueous polymerization process. To enhance the porosity, mechanical strength, and drug loading capability of the hydrogel and reduce its toxicity, iron- based metal-organic framework was incorporated within the hydrogel. To add more functionality to the final wound dressing, Camellia sinensis, an antibacterial herbal drug was loaded on the hydrogel. The structural and chemical properties of prepared nanocomposite hydrogel were investigated by FTIR, XRD, SEM, and TGA techniques. The incorporation of iron-based metal-organic framework within the hydrogel matrix led to an increase in its water absorption value from 400.10 to 547.96 (g/g). The release study of Camellia sinensis (CS) extract from the prepared nanocomposite hydrogel exhibited a sustained release manner. The antibacterial test revealed the nanocomposite hydrogel contain extract has an effective antibacterial function against "Bacillus serous", "Staphylococcus aureus", "Streptococcus mutans"," Escherichia coli", "Klebsiella pneumoniae", and "Pseudomonas aeruginosa" bacteria. Therefore, the synthesized nanocomposite is a good candidate as an antibacterial hydrogel wound dressing. .

Evaluating the effect of graphene oxide PEGylation on the properties of chitosan-graphene oxide nanocomposite scaffold.

In this study, graphene oxide (GO) was functionalized with polyethylene glycol (PEG) to understand the effect of PEGlayted GO on properties of chitosan-based nanocomposite scaffold. GO was synthesized according to modified Hummer's method and covalently linked to polymeric chains of PEG to produce polyethylene glycolated GO (PGO). Successful preparation of GO and PGO was confirmed by FT-IR and Raman techniques, where the chemical bonding of PEG and GO nanosheets were concluded based on PGOs' lower zeta potential compared to GO. Nanocomposite scaffolds were prepared by adding equal amounts of GO and PGO into 2% (w/v) chitosan (Cs) solutions. The highly porous scaffolds were developed by lyophilization of solutions. Incorporation of GO and PGO into chitosan scaffold network resulted in uniform and spherical pores. Modified samples offered higher porosity and density, indicating adequate scaffold structure. Improvements in the physical properties of prepared chitosan scaffolds were concluded through higher water absorption and retention values. Compressive strength measurement showed 6.33 and 5.5 times improvement respectively for Cs-GO and Cs-PGO samples compared to Cs scaffold. The Cs-GO scaffolds showed minimum susceptibility toward enzymatic degradation and higher degrees of protein adsorption (26% and 23% improvement in value of adsorbed protein respectively for Cs-GO and Cs-PGO compared to Cs scaffold) and biomineral formation on scaffold surface. Also, Cs-PGO sample showed the highest degree of cell viability and lower hemolysis than both Cs and Cs-GO scaffolds. Investigations showed that cell infiltration into scaffold porous structure was more prominent in Cs-PGO scaffolds than in Cs and Cs-GO scaffolds.

Effect of glutaraldehyde and calcium chloride as different crosslinking agents on the characteristics of chitosan/cellulose nanocrystals scaffold.

The effect of glutaraldehyde and calcium cations as covalent and ionic crosslinkers was investigated on the main characteristics of scaffolds based on chitosan and cellulose nanocrystals. Therefore, four different scaffolds based on chitosan/cellulose nanocrystals with different crosslinking methods were fabricated using the freeze-drying method for potential use in bone tissue engineering. The structural and chemical features of prepared scaffolds were studied by the FTIR technique. FESEM images revealed that all scaffold samples are porous three-dimensional networks in which the pores are connected. TGA analysis showed that the thermal stability of scaffolds based on chitosan/cellulose nanocrystals has not been changed significantly by using different crosslinking methods. The chitosan/cellulose nanocrystals scaffold crosslinked by glutaraldehyde represented the highest compressive strength and the uncrosslinked scaffold showed the highest swelling ratio in comparison to the other scaffolds. The fastest degradation rate belonged to the scaffold crosslinked by calcium cations. FESEM images and EDX analysis confirmed that fabricated scaffolds have good biomineralization ability. The cell viability and cell attachment results indicated that all four scaffolds support cell proliferation and cell adhesion. However, the viability of NIH3T3 fibroblast cells in the presence of glutaraldehyde-containing scaffolds was lower than that of other scaffolds.

Development of a novel reinforced scaffold based on chitosan/cellulose nanocrystals/halloysite nanotubes for curcumin delivery.

Chitosan, cellulose nanocrystals, and halloysite nanotubes in the presence of calcium cations were used to fabricate a three-dimensional nanocomposite scaffold. The FTIR and XRD analyses revealed that formation of the network and incorporation of halloysite nanotubes into it were successful. FESEM images showed that the addition of higher amounts of halloysite nanotubes into the scaffold's matrix leads to more and smaller pores. The addition of halloysite nanotubes enhanced the thermal stability, mechanical characteristics, water uptake, and degradation rate of the nanocomposite scaffold. The nanocomposite scaffold represented good biomineralization, great cell proliferation, and acceptable cell attachment. Furthermore, the capability of the nanocomposite scaffold for curcumin delivery was approved through cell proliferation, cumulative release, and antibacterial studies. Cell proliferation of the nanocomposite with 10 wt% curcumin-loaded halloysite nanotubes reached around 175% after 72 h. Considering the results, the prepared nanocomposite scaffold holds great potential for being used in bone tissue engineering applications.

Starch-based semi-IPN hydrogel nanocomposite integrated with clinoptilolite: Preparation and swelling kinetic study.

Semi-interpenetrating polymer network (semi-IPN) of starch-graft-poly(acrylic acid-co-acrylamide)/polyvinyl alcohol/clinoptilolite (starch-g-p(AA-co-AAm)/PVA/clino) superabsorbent nanocomposite was synthesized by free-radical graft co-polymerization technique in an aqueous solution. Taguchi method was used to optimize the synthesis reaction condition based on the equilibrium swelling capacity of the hydrogels. FTIR, XRD, and SEM analyses were used to study the chemical and structural properties of the hydrogel samples. The equilibrium swelling capacity of the semi-IPN superabsorbent nanocomposite (364.82 g/g) was higher than that of neat hydrogel (286.21 g/g) and in both of them water penetration into hydrogel network occurred through non-Fickian diffusion mechanism. Incorporation of clino into the polymeric matrix not only increased the equilibrium swelling capacity of the hydrogel, but also induced a substantial enhancement in its mechanical strength. Semi-IPN superabsorbent nanocomposite showed reasonable water absorbency under different loads, good salt and pH-sensitive swelling behavior, and better water retention capability, which make it potentially useful for hygiene products.

Slow-release NPK fertilizer encapsulated by carboxymethyl cellulose-based nanocomposite with the function of water retention in soil.

In this study, new slow release fertilizer encapsulated by superabsorbent nanocomposite was prepared by in-situ graft polymerization of sulfonated-carboxymethyl cellulose (SCMC) with acrylic acid (AA) in the presence of polyvinylpyrrolidone (PVP), silica nanoparticles and nitrogen (N), phosphorous (P), and potassium (K) (NPK) fertilizer compound. The prepared materials were characterized by FT-IR, XRD and scanning electron microscopy (SEM) techniques. The incorporation of NPK fertilizer into hydrogel nanocomposite network was verified by results of these analyses. Also, the swelling behavior in various pH and saline solutions as well as water retention capability of the prepared hydrogel nanocomposite was evaluated. The fertilizer release behavior of the NPK loaded hydrogel nanocomposite was in good agreement with the standard of Committee of European Normalization (CEN), indicating its excellent slow release property. These good characteristics revealed that the hydrogel nanocomposite fertilizer formulation can be practically used in agricultural and horticultural applications.

Semi-IPN superabsorbent nanocomposite based on sodium alginate and montmorillonite: Reaction parameters and swelling characteristics.

Semi-interpenetrating polymer network (semi-IPN) superabsorbent nanocomposite based on montmorillonite (MMT) and sodium alginate (NaAlg)-g-poly(acrylic acid(AA))/polyvinylpyrrolidone (PVP) was synthesized. Chemical structure and surface morphology of the hydrogels were characterized by FTIR, XRD, thermogravimetric analysis (TGA), SEM, and TEM techniques. FTIR results revealed that graft polymerization, PVP interpenetration through hydrogel network, and nanocomposite formation have occurred. The coarse surface of the hydrogels was changed into interlinked porous structures in the presence of MMT. The effect of polymerization variables on water absorbency of the hydrogels was assessed and optimized. Semi-IPN superabsorbent nanocomposite presented higher equilibrium swelling capacity (618.92 g/g) compared with neat hydrogel (521.17 g/g). Swelling behavior of the hydrogels strongly depended on pH values of the solution as well as the type and concentration of saline solution. Semi-IPN superabsorbent nanocomposite possessed good reswelling capability, making it as an efficient water reservoir to supply required water to plants in agricultural applications.

Preparation of an antibacterial, hydrophilic and photocatalytically active polyacrylic coating using TiO2 nanoparticles sensitized by graphene oxide.

In recent years more attentions have been paid for preparation of coatings with self-cleaning and antibacterial properties. These properties allow the surface to maintain clean and health over long times without any need to cleaning or disinfection. Acrylic coatings are widely used on various surfaces such as automotive, structural and furniture which their self-cleaning and antibacterial ability is very important. The aim of this work is the preparation of a polyacrylic based self-cleaning and antibacterial coating by the modification of TiO2 as a coating additive. TiO2 nanoparticles were sensitized to the visible light irradiation using graphene oxide through the preparation of TiO2/graphene oxide nanocomposite. Graphene oxide was prepared via a modified Hummers method. TiO2/graphene oxide nanocomposite was used as additive in a polyacrylic coating formulation. Hydrophilicity, photocatalytic and antibacterial activities as well as coating stability were evaluated for TiO2/graphene oxide modified polyacrylic coating and compared with that of pristine TiO2 modified and unmodified polyacrylic coatings. TiO2/graphene oxide nanocomposite and polyacrylic coating modified by TiO2/graphene oxide additive were characterized using FT-IR, UV-Vis, XRD, and FESEM techniques. The effect of TiO2/graphene oxide composition and its percent in the coating formulation was evaluated on the polyacrylic coating properties. Results showed that polyacrylic coating having 3% W TiO2/graphene oxide nanocomposite additive with TiO2 to graphene oxide ratio of 100:20 is the best coating considering most of beneficial features such as high photodecolorization efficiency of organic dye contaminants, high hydrophilicity, and stability in water. According to the results, TiO2 is effectively sensitized by graphene oxide and the polyacrylic coating modified by TiO2/graphene oxide nanocomposite shows good photocatalytic activity under visible light irradiation.

Superabsorbent hydrogel made of NaAlg-g-poly(AA-co-AAm) and rice husk ash: Synthesis, characterization, and swelling kinetic studies.

The sodium alginate-g-poly(acrylic acid-co-acrylamide)/rice husk ash (NaAlg-g-P(AA-co-AAm)/RHA) superabsorbent nanocomposite was synthesized by the free-radical graft copolymerization of alginate (NaAlg), acrylic acid (AA), acrylamide (AAm), and RHA in aqueous solution. FTIR spectra revealed that the monomers were grafted onto NaAlg chains, and the nanocomposite was formed successfully. Incorporation of RHA into hydrogel matrix formed porous interlinked channels within hydrogel network. Superabsorbent nanocomposite showed greater equilibrium swelling capacity (1070g/g) compared with neat hydrogel (830g/g). Moreover, water transport mechanism of all hydrogels was non-Fickian diffusion type. Rheological measurements confirmed effective role of RHA in improving gel strength of superabsorbent nanocomposite. The influence of various factors, such as different loads (0.3, 0.6, 0.9 psi), solution pH, saline solution, and temperature on the swelling behavior of hydrogels was also assessed. Superabsorbent nanocomposite exhibited good pH-dependent swelling reversibility and high water retention capability, making it more efficient water-saving material for agricultural and horticultural applications.

Slow-released NPK fertilizer encapsulated by NaAlg-g-poly(AA-co-AAm)/MMT superabsorbent nanocomposite.

A novel slow released NPK fertilizer encapsulated by superabsorbent nanocomposite was prepared via in-situ free radical polymerization of sodium alginate, acrylic acid, acrylamide, and montmorillonite in the presence of fertilizer compounds. Evidence of grafting and component interactions, superabsorbent nanocomposite structure and morphology was obtained by a FT-IR, XRD and SEM techniques. The water absorbency behavior of superabsorbent nanocomposite was investigated. After those characterizations, the potential application was verified through the study of fertilizer release from prepared formulations. Results indicated that the presence of the montmorillonite caused the system to liberate the nutrient in a more controlled manner than that with the neat superabsorbent. The good slow release fertilizer property as well as good water retention capacity showed that this formulation is potentially viable for application in agriculture as a fertilizer carrier vehicle.

Electrocatalytic reduction of nitrate ions from water using polyaniline nanofibers modified gold electrode.

Polyaniline (PANI) nanofibers were electrochemically synthesized on gold electrode using ethanol as soft template by the cyclic voltammetry technique. The PANI nanofibers were characterized by Fourier transform infrared spectroscopy, UV-visible spectroscopy, and scanning electron microscopy. Linear sweep voltammetry was used to investigate electrocatalytic activity of the PANI nanofibers modified electrode toward the reduction of nitrate ions. Results showed that the electroreduction process strongly depends on the applied potential. At the potential value of about -0.8 V vs Ag/AgCl, the electroreduction of nitrate anions to nitrite anions was identified as the rate-determining step of the electroreduction process. In the potential range of -0.8 to -1.0 V, reduction of nitrite to hydroxylamine occurs, followed by the reduction to ammonia. At potentials more negative than -1.0 V, nitrite is directly reduced to ammonia. This study demonstrates the effectiveness of PANI nanofibers modified electrode in the electroreduction of nitrate ions compared to traditional reduction methods.

Degradation of ampicillin antibiotic in aqueous solution by ZnO/polyaniline nanocomposite as photocatalyst under sunlight irradiation.

PURPOSE AND METHOD: ZnO/polyaniline nanocomposite in core-shell structure was prepared by the synthesis and adsorption of polyaniline chains on the structure of ZnO nanoparticles. Fourier transform infrared and ultraviolet-visible (UV-Vis) spectroscopy, X-ray diffraction patterns, field emission scanning electron microscopy, and transmission electron microscopy were used to characterize the composition and structure of the nanocomposite. The nanocomposite was used as an active photocatalyst for photodegradation and removal of ampicillin in aqueous solution. RESULTS: UV-Vis spectroscopy studies showed that ZnO/polyaniline nanocomposite absorbs visible light irradiation as well as ultraviolet spectrum, and therefore, it can be photoactivated under visible and ultraviolet lights. The photocatalytic activity of ZnO/polyaniline nanocomposite in degradation of ampicillin molecules in aqueous solution under natural sunlight irradiation was evaluated and compared with that of ZnO nanoparticles and pristine polyaniline. The ZnO/polyaniline core-shell nanocomposite exhibited higher photocatalytic activity compared to ZnO nanoparticles and pristine polyaniline. The effect of operating conditions (pH, ZnO/polyaniline nanocomposite dosage, and ampicillin concentration) in the photocatalytic degradation of ampicillin using ZnO/polyaniline nanocomposite was investigated. The optimum conditions for maximum efficiency of ampicillin degradation under 120 min sunlight irradiation were found as 10 mg L(-1) dosage of ZnO/polyaniline nanocomposite, ampicillin concentration of 4.5 mg L(-1), and solution pH = 5. Under optimum operating conditions, degradation efficiency was reached to 41% after 120 min of exposure to the sunlight irradiation.

Removal of chromium from aqueous solution using polyaniline--poly ethylene glycol composite.

The adsorption of chromium compounds from solutions by a composite of polyaniline/poly ethylene glycol (PANi/PEG) was investigated in this study. Experiments were conducted in batch mode under various operational conditions including agitation time, solution pH, PANi/PEG dose and initial concentration of chromium salts. Results showed that concentration of PEG at synthesizing stage has a significant effect on the capacity of produced composite for removal of chromium. Morphologically, PANi/PEG composite is closely dependent on the concentration of PEG. Maximum removal of hexavalent chromium was experienced when 2g/L of PEG was used in synthesis of PANi/PEG. Removal of hexavalent chromium by PANi/PEG composite included surface adsorption and reduction reaction. The optimum pH was 5 and the equilibrium time for hexavalent chromium removal was about 30 min. Investigation of the isothermal characteristics showed that chromium adsorption by PANi/PEG composite was in high accordance with Langmuir's isotherm.

Determination of linear short chain aliphatic aldehyde and ketone vapors in air using a polystyrene-coated quartz crystal nanobalance sensor.

A polystyrene coated quartz crystal nanobalance (QCN) sensor was developed for use in the determination of a number of linear short-chain aliphatic aldehyde and ketone vapors contained in air. The quartz crystal was modified by a thin-layer coating of a commercial grade general purpose polystyrene (GPPS) from Tabriz petrochemical company using a solution casting method. Determination was based on frequency shifts of the modified quartz crystal due to the adsorption of analytes at the surface of modified electrode in exposure to various concentrations of analytes. The frequency shift was found to have a linear relation to the concentration of analytes. Linear calibration curves were obtained for 7-70 mg l(-1) of analytes with correlation coefficients in the range of 0.9935-0.9989 and sensitivity factors in the range of 2.07-6.74 Hz/mg l(-1). A storage period of over three months showed no loss in the sensitivity and performance of the sensor.

Application of polyaniline for the reduction of toxic Cr(VI) in water.

Various oxidation states of polyaniline, as film and powder, were used for reduction of highly toxic Cr(VI) to less toxic Cr(III) ion. The effects of various parameters such as synthesis method, physical and oxidation state of polyaniline, film thickness, solution pH and initial Cr(VI) concentration on the kinetics and efficiency of reduction process were investigated. Results showed that a very broad concentration range of Cr(VI) solutions (10-10(5)ppb by emeraldine base and 10-10(6.5)ppb by leucoemeraldine) can be efficiently (>98%) reduced by polyaniline as film or powder. Cr(VI) solutions with concentrations higher than these ranges were caused to the overoxidation and degradation of polymer. Decreasing of solution pH, increased the kinetics and performance of reduction process, but lowered the Cr(VI) concentration ranges caused the overoxidation and degradation of the polymer. Higher reduction efficiencies were obtained for thicker electrochemically synthesized polyaniline films and for thinner chemically prepared polyaniline free standing films. The ability or capacity of various forms of polyaniline in Cr(VI) reduction was evaluated as the milligrams of Cr(VI) reduced by one gram of various forms of polyaniline.