Fabrication and characterization of CMC‐based magnetic superabsorbent hydrogel nanocomposites for crystal violet removal

In this research work, novel magnetic superabsorbent hydrogel nanocomposites (MSHNs) based on carboxymethyl cellulose were prepared via a facile “one‐pot” two step approach. Magnetic iron oxide nanoparticles were in situ synthesized and incorporated into carboxymethyl cellulose/poly(acrylic acid) polymer hydrogel. The morphology and chemical composition of MSHNs as well as the presence of magnetic iron oxide nanoparticles were evaluated by using Fourier transform infrared, scanning electron microscopy, transmission electron microscopy, X‐Ray diffraction, ultraviolet–visible spectroscopy, thermogravimetric analysis, and vibrating sample magnetometer. The effect of different reaction parameters on the swelling capacity of MSHNs was investigated. Furthermore, batch adsorption experiments of crystal violet dye onto MSHNs were studied by varying solution pH, initial dye concentration, and temperature. Evaluation of thermodynamic parameters of crystal violet adsorption confirmed that the adsorption was spontaneous and endothermic process in nature. The equilibrium study revealed that the dye adsorption behavior of MHSNs followed the Redlich‐Peterson isotherm model. Finally, the dye adsorption experiment data was well fitted by the pseudo‐second‐order kinetic model with the regression coefficient (R²) of 0.9979. Our results suggest that the MHSNs with facile preparation method, high swelling capacity, and high dye adsorption capacity may be used as promising adsorbents for fast removal of various dyes from aqueous solutions. Copyright © 2016 John Wiley & Sons, Ltd.     

Preparation of pH- and thermo-sensitive hydrogel by two-step grafting of acrylamide and acrylic acid onto preirradiated polyethylene film

Two-step grafting reaction of acrylamide (AAm) and acrylic acid (AAc) onto preirradiated polyethylene (PE) film were performed. The effects of irradiation dose, reaction temperature and reaction time on the grafting yield were studied. The effect of reaction time of the first step grafting on the yield of the second step grafting was also evaluated. The original and the irradiated PE films were tested by Fourier transform infrared (FTIR) spectroscopy in the attenuated total reflectance mode (ATR). The AAm and AAc grafted PE film appeared thermo- and pH-sensitive which are similar to the interpenetrating polymer network hydrogel. This revised version was published online in July 2006 with corrections to the Cover Date.     

Adsorption of crystal violet dye from aqueous solution using mesoporous materials synthesized at room temperature

In this work, batch adsorption experiments are carried out for crystal violet dye using mesoporous MCM-41 synthesized at room temperature and sulfate modified MCM-41 prepared by impregnation method using H₂SO₄ as sulfatising agent. The surface characteristics, pore structure, bonding behavior and thermal degradation of both the MCM-41 samples are characterized by nitrogen adsorption/desorption isotherms, X-ray diffraction (XRD) patterns, Fourier transform infrared (FT-IR) spectroscopy and thermo gravimetric analysis (TGA). The adsorption isotherm, kinetics and thermodynamic parameters are investigated for crystal violet (CV) dye using the calcined and sulfated MCM-41. Results are analysed using Langmuir, Freundlich and Redlich-Peterson isotherm models. It is found that the Freundlich model is an appropriate model to explain the adsorption isotherm. The highest adsorption capacity achieved is found to be 3.4×10⁻⁴ mol g⁻¹ for the sulfated MCM-41. The percentage removal of crystal violet dye increases with increase in the pH for both the MCM-41 adsorbents. Kinetics of adsorption is found to follow the second-order rate equation. From the thermodynamic investigation, it is evident that the adsorption is exothermic in nature.     

Spectral characteristics and nonlinear studies of crystal violet dye

Solid-state dye-doped polymer is an attractive alternative to the conventional liquid dye solution. In this paper, the spectral characteristics and the nonlinear optical properties of the dye crystal violet are studied. The spectral characteristics of crystal violet dye doped poly(methylmethacrylate) modified with additive n-butyl acetate (nBA) are studied by recording its absorption and fluorescence spectra and the results are compared with the corresponding liquid mixture. The nonlinear refractive index of the dye in nBA and dye doped polymer film were measured using z-scan technique, by exciting with He-Ne laser. The results obtained are intercompared. Both the samples of dye crystal violet show a negative nonlinear refractive index. The origin of optical nonlinearity in the dye may be attributed due to laser-heating induced nonlinear effect.     

Enthalpies of adsorption of methylene blue and crystal violet to montmorillonite

Calorimetric measurements of the enthalpy of adsorption on montmorillonite indicate different patterns for methylene blue (MB) and crystal violet (CV). The enthalpy of adsorption of MB is endothermic up to 73% of the cation exchange capacity (CEC) (i.e., about 0.6 mmol g^-1 clay), whereas at higher adsorption ratios the adsorption reaction becomes exothermic. The enthalpy of adsorption of CV is exothermic for all amounts adsorbed. These results were confirmed with adsorption experiments that prove that adsorption of MB increase with temperature, whereas CV adsorption decreases. This behavior indicates changes in the equilibrium coefficient according to Van't Hoff's equation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Adsorption of fast green and erythrosin-B to montmorillonite modified with crystal violet

Adsorption of erythrosin-B (EB) and fast green (FG) to a non-charged organosmectite based on crystal violet adsorbed up to 100% of the cation exchange capacity (CEC) was tested. Adsorption isotherms of EB and FG were prepared at 3, 24 and 50°C. All isotherms are of H-type reaching loads of approximately up to 20% of the original CEC of the crude montmorillonite (up to 0.15 and 0.10 mol dye kg^–1 clay for EB and FG, respectively). Adsorption decreases with temperature, indicating an exothermic process. Enthalpy was evaluated using van’t Hoff equation, yielding approximately –20 kJ mol^–1 for both dyes.     

Ultrasound facilitates and improves removal of triphenylmethane (crystal violet) dye from aqueous solution by activated charcoal: A kinetic study

This work was aimed at removing crystal violet (CV) from an aqueous solution via an ultrasound-aided sorption process. Different operational parameters, such as contact time, ultrasonic power, and the sorbent dosage, were investigated. The results indicated that the sorption process was more rapid compared with the previously stated process; a sorption equilibrium was obtained after 1.5 h. The increase in the dose from 0.02 to 5.0 g/L increased the adsorption efficiency by 100%. The decolorization of the CV pigment occurred very rapidly at the highest sound power, 200 W, and it reached ～85%. The kinetics study indicated that the sorption process fitted the pseudo-second-order model with the chemisorption mechanism. The sorption isotherm data were also interpreted by the mass-transfer model, which established the intraparticle diffusion. Additionally, to estimate the rate-limiting step mechanisms, the intraparticle diffusion was not considered as the sole rate-controlling step. The maximum sorption capacity (q_max) increased from 19.0 to 24 mg/g during the ultrasound and indicated the positive synergistic effect of the ultrasound. The proposed sonosorption technique is a low cost-effective method for purifying water and wastewater from organic pollutants.     

Effect of processing parameters on structural and optical properties of CeO2 nanoparticles for the removal of crystal violet dye

Journal of Sol-Gel Science and Technology - The present work reports the synthesis of CeO2 nanoparticles (NPs) via chemical route by optimizing synthesis parameters such as solvent, capping agent,...     

Sorptive removal of cobalt, strontium and cesium onto manganese and iron oxide-coated montmorillonite from groundwater

Applicability of montmorillonite, manganese oxide-coated montmorillonite (MOCM) and iron oxide-coated montmorillonite (IOCM) as backfill materials in permeable reactive barrier (PRB) to remediate contaminated groundwater was investigated. Single- and bi-solute competitive sorptions of Co, Sr and Cs were conducted. The Freundlich, Langmuir and Dubinin-Radushkevich models fitted the single-solute sorption data well (R ² > 0.95). Maximum sorption capacities (q _mL) of Co and Sr predicted by the Langmuir model were in the order of MOCM (0.37 mmol/g for Co and 0.28 mmol/g for Sr) > montmorillonite (0.27 mmol/g for Co and 0.19 mmol/g for Sr) ≈ IOCM (0.23 mmol/g for Co and 0.21 mmol/g for Sr), while those of Cs were in the order of montmorillonite (1.11 mmol/g) > MOCM (0.68 mmol/g) > IOCM (0.62 mmol/g). In the bi-solute sorptions, the sorbed amount of one solute decreased due to the presence of the other competing metal ion. Langmuir model parameters for single-solute (q _mL and b _L) and bi-solute ( q_\textmL^* q_{\text{mL}}^{*} and b_\textL ^* b_{\text{L}}^{ *} ) sorptions were compared to analyze the effect of competition between the metal ions. The competitive Langmuir (R ² > 0.81) and P-factor (R ² > 0.82) models predicted the bi-solute competitive sorption data well but not the SRS model (0.003 < R ² < 0.97).     

Study of association thermodynamics between crystal violet and sodium bis(2-ethylhexyl)sulfosuccinate and kinetics of basic fading of crystal violet in microemulsions

The thermodynamics of the association between 4,4′,4″-tris(dimethyl-amino)triphenylmethyl chloride (crystal violet or CV) and sodium bis(2-ethylhexyl)-sulfosuccinate (aerosol OT or AOT) in water/AOT/n-decane microemulsion and the kinetics of the basic hydrolysis of CV in a water-in-oil microemulsion were investigated by UV–vis spectroscopic measurements. An association model of CV and AOT was used to analyze the experimental data to obtain the association constants at various temperatures. By taking the association into account, the “actual” rate constants and the activation energies of the basic hydrolysis of CV in the media of water/AOT/oil were obtained. The difference in thermodynamics and kinetics between the two media of water/AOT/n-decane and water/AOT/isooctane is discussed. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 294–300, 2008     

Controlled crystal phase and particle size of loaded-TiO2 using clinoptilolite as support via hydrothermal method for degradation of crystal violet dye in aqueous solution

TiO₂-supported clinoptilolites (TiO₂/clinoptilolites) were successfully synthesized with controlled crystal phase and particle size via hydrothermal method to enhance photocatalytic performance of TiO₂. The effects of various parameters including temperature, acidity and concentration of Ti-containing solutions on the particle size, crystal phase and agglomeration of TiO₂ supported on clinoptilolite were investigated thoroughly by characterizations of X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), transmission electron microscope (TEM), BET isotherm, UV–visible (UV–vis) spectrophotometer and Malvern zetasizer. The results demonstrate that increasing temperature and strengthen acidity are beneficial to enhance the crystallinity and particle size of supported TiO₂. Increase in acidity also leads to more uniform distribution of TiO₂ on the surface of clinoptilolite. The TiO₂ nano-crystals deposited on the surface of clinoptilolite, exhibit rutile or anatase phase, strongly depending on the preparation procedure. The resultant TiO₂/clinoptilolites could be used as photo-catalysts for the degradation of crystal violet (CV) dye in aqueous solution, showing a higher photo-catalytic activity with 89% degradation within 100 min. The effect of operational parameters, such as pH values of reaction media, dose of used catalyst, and concentration of CV dye on the CV degradation performance were investigated, in which the kinetics of CV dye degradation was found to follow the pseudo-first order kinetic model.     

Green synthesis and characterization of copper and nickel hybrid nanomaterials: Investigation of their biological and photocatalytic potential for the removal of organic crystal violet dye

Nanotechnology deals with the materials at nanoscale to synthesize nanoparticles. The current study introduced a new green approach for the synthesis of Copper and Nickel hybrid nanoparticles by using Zingiber officinale rhizome extract as a capping and reducing agent. The nanoparticles were physico-chemically characterized by UV–visible spectroscopy, Fourier transform infrared spectroscopy, X-ray powder diffraction, Energy-dispersive X-ray spectroscopy, and Scanning electron microscopy. It was revealed by scanning electron micrograph that the Cu-Ni hybrid nanoparticles have spherical geometries with average grain size of 25.12 ± 1.2 nm. Furthermore, biocatalytic and photocatalytic applications of the biosynthesized nanoparticles were assessed. The results of antibacterial assay revealed that Cu-Ni hybrid nanoparticles had an inhibition zones of 28 ± 1.0, 25 ± 0.8, and 25 ± 1.5 mm against P. aeruginosa, E. coli and Proteus vulgaris. Commercially available antibiotics were purchased and coated with Cu-Ni hybrid nanoparticles, it was found that their antimicrobial efficacy was increased twice. To evaluate the antioxidant potential, nanoparticles having a concentration of 200 µg/mL were applied against 2,2-diphenyl-1-picrylhydrazyl free radicals and NPs showed 42.1 ± 0.71 % inhibition. Cu-Ni nanoparticles have shown a dose-dependent cytotoxicity against amastigote and promastigote in anti-leishmanial assay. The synthesized nanoparticles were found biocompatible and safe in nature to be used in vivo, as they showed no significant hemolysis of human red blood cells at their highest concentration. In antidiabetic assay, NPs inhibited alpha-amylase enzyme up to 38.07 ± 0.65 %. An organic crystal violet dye was successfully degraded by the synthesized nanoparticles in photocatalytic assay. Hence, it is concluded that Cu-Ni hybrid nanoparticles can be used both in vitro and in vivo for drug delivery in biomedical research. These nanoparticles can also be used in the remediation of organic dyes as a catalyst.     

Enhanced visible light-driven photocatalytic degradation of crystal violet dye using Cr doped BaFe12O19 prepared via facile micro-emulsion route

The Cr ion doping effect on various properties of Cr doped BaCr_xFe_12-xO₁₉ nanoparticles was investigated, which were synthesized via a facile microemulsion approach and properties were studied using XRD, SEM, FTIR, Raman, photoluminescence and UV–visible techniques along with dielectric, optical and ferroelectric properties. The BaCr_xFe_12-xO₁₉ structure was hexagonal involving P63/mmc space group with average crystalline size of 9–18 nm. The NPs exhibited agglomerated platelet heterogeneous morphology. The presence of the Ba-O-Fe functional group was also confirmed by FTIR analysis. The PL analysis revealed that the doping reduced the recombination rate and charge (e^?-h⁺) separation is facilitated. The coercivity (H_c) and saturation polarization (Ps) increased with doping content and dielectric loss reduces with frequency and dopant concentration. The dopant contents also increased the AC conductivity and the optical bandgap found in 1.75–2.83 (eV) range. The BaCr_xFe_12-xO₁₉ exhibited a significantly higher photocatalytic efficiency versus BaFe₁₂O₁₉, and 91 % CV dye was degraded in 90 min under visible light irradiation. Additionally, a recycling experiment was conducted to confirm the stability of the prepared photocatalyst and Cr doped BaCr_xFe_12-xO₁₉ exhibited excellent stability and reusability. The Cr doping affected the dielectric, optical and ferroelectric properties and based on photocatalytic properties of BaCr_xFe_12-xO₁₉, it has potential applications for the destruction of dyes in wastewater under visible light exposure, which will make the process highly feasible for photocatalytic applications.     

Radiation-induced grafting of acrylamide onto guar gum in aqueous medium: Synthesis and characterization of grafted polymer guar-g-acrylamide

Mutual radiation grafting technique has been applied to carry out grafting of acrylamide (AAm) onto guar gum (GG) using high-energy Co⁶⁰ γ radiation to enhance its flocculating properties for industrial effluents. The grafted product was characterized using analytical probes like elemental analysis, thermal analysis, Fourier transformed infrared (FTIR), X-ray diffraction (XRD) and scanning electron microscope (SEM). The grafting extent was observed to decrease with the dose rate and increase with the concentration of AAm. Thermo gravimetric analysis (TGA) of grafted and ungrafted samples indicated better stability of grafted product. γ and microwave radiation effect on grafted and virgin GG has also been reported.     

Removal of methylene blue dye from an aqueous media using superabsorbent hydrogel supported on modified polysaccharide

The removal of methylene blue (MB) in water with the superabsorbent hydrogel (SH) formed by modified gum arabic, polyacrylate, and polyacrylamide was investigated. The SH exhibited excellent performance in MB absorption. The maximum absorption capacity was 48 mg of the dye per g of SH, representing 98% of the MB removed. Experimental parameters were used as follows: pH 8, hydrogel mass 50 mg, and initial concentration of MB 50 mg L(-1). In a procedure with an individual solution of orange II, an opposite effect related to the MB was observed: the hydrogel only absorbed water, resulting in an orange II-richer solution. The orange II concentration in solution increased about 50 times (relative to the initial concentration). In another experiment using an aqueous mixture of orange II and MB, the SH absorbed the MB exclusively. Compared to the MB, the orange II is separated from water by SH selectivity-absorption through an inverse process. This effect was attributed to the formation of a ionic complex between the imine groups of MB and the ionized carboxylic groups of SH.     

Diffusion coefficients of lithium chloride and potassium chloride in hydrogel membranes derived from acrylamide

Diffusion of non-associated electrolytes (potassium chloride and lithium chloride) in concentrated aqueous solutions (0.1-1.0 mol dm⁻³) has been studied in hydrogels derived from acrylamide and methyl methacrylate to study the mechanism of electrolyte transport. The preparation of two gels with different monomer ratio compositions resulted in obtaining membranes of substantially different hydrophilic character with polymer fractions of 0.3 and 0.5.Cukier hydrodynamic model was applied to explain the dependence of the diffusion coefficients of KCl and LiCl on the electrolyte concentration in hydrogel obtained experimentally. It was shown that the increase of the diffusion coefficients is accompanied with a decrease of the mean distance of approach of the ions. This can be explained by the formation of ion-pairs, resulting in a further contribution to diffusion once there is a decrease in the hydrodynamic resistance of the medium to the diffusing particles. Parameters, which characterise such a behaviour quantitatively, are different for different electrolytes and depend on water content in the gel.     

Transuranium removal from Hanford High Level Waste simulants using sodium permanganate and calcium

Hanford High Level Waste will require processing to reduce the concentration of various actinide elements prior to encapsulation into low activity glass for disposition. High level waste at Hanford contains elevated actinide concentrations in the supernate because of organic complexants present in the tanks. Traditional removal strategies are not viable processing sequences for the Hanford tanks containing complexants. Reported here is a novel actinide decontamination strategy. This pretreatment sequence consists of addition of calcium nitrate and sodium permanganate. The observed optimum decontamination efficiencies for plutonium and americium are more than 99.5%.     

Effect of the chemical grafting of epoxy resin onto organomodified montmorillonite on the structure and heat resistance of an epoxy nanocomposite

It is shown that the noncatalyzed chemical grafting of an epoxy oligomer onto the surface of montmorillonite platelets may proceed via the reaction between the epoxy groups and the hydroxyl groups of the organic modifying agent of the layered aluminosilicate. The effect of grafting on the structure and heat resistance of the cured epoxy nanocomposite is studied. Complete exfoliation of montmorillonite particles into individual platelets is shown to be a necessary but insufficient condition for increasing the glass-transition temperature of the nanocomposite relative to that of the initial matrix. A much higher contribution to the increase in the glass-transition temperature is ensured by grafting of epoxy molecular chains onto the surface of aluminosilicate platelets; i.e., strong covalent matrix-aluminosilicate bonds form in addition to physical bonds, a process that entails development of a thicker three-dimensional network.     

A simple method for removal of toxic dyes such as Brilliant Green and Acid Red from the aquatic environment using Halloysite nanoclay

This project explains an easy, simple and eco-friendly method to remove some toxic dyes like Brilliant Green and Acid Red from aquatic solution by technique of solid-phase extraction that uses Halloysite nanoclay eco-friendly solid phase as absorbent surface for adsorption of dye. The physical properties of the HNC such as scanning electron microscopy, transmission electron microscope, X-ray diffraction, Fourier transform infrared spectroscopy, and surface area analysis were studied. The best conditions like pH of the solution, HNC weight, contact shaking time, the temperature of the solution, and ionic strength were investigated for removal effectiveness. The experimental data of the adsorption process showed that HNC can remove most of the dyes within 30 min, with an adsorption capacity of 12.5 mg/g for A.R dye and 13.9 mg/g for B.G dye on HNC solid phase at optimum conditions. The removal process of dyes on HNC was studied kinetically and thermodynamically, and the data confirms that the pseudo-second-order kinetic model was able to describe the adsorption process. Thermodynamic data confirms the process was spontaneous andexothermic in nature for A.R dye, while was spontaneous and endothermic in nature for B.G dye. Finally, the effectiveness of HNC was inspected by removing dyes from three various real samples, and the results showed high performance in removing dyes on HNC for four consecutive cycles.