Decoration of MWCNTs with CoFe2O4 Nanoparticles for Methylene Blue Dye Adsorption

In the present work, a simple and viable method for producing multi-walled carbon nanotubes (MWCNTs) decorated with CoFe₂O₄ nanoparticles is presented. Chemical composition and crystal structure of the CoFe₂O₄/MWCNT composite was confirmed by X-ray diffraction measurements, while transmission electron microscopy was used to characterize the morphology and the distribution of nanocrystals in the composite. The obtained particles with relatively small diameter (about 14.9?nm) were found to be dispersed on the carbon nanotubes. The adsorption of methylene blue dye on CoFe₂O₄/MWCNT composites has been investigated. CoFe₂O₄/MWCNT composites show high adsorption capacity for methylene blue dye. Both Langmuir and Freundlich models describe the adsorption isotherms very well and the adsorption thermodynamic parameters (?G ⁰, ?H ⁰ and ?S ⁰) were calculated. The adsorption of methylene blue is generally spontaneous and thermodynamically favorable. The adsorption of methylene blue involves an endothermic process.     

Thermodynamic study on molecular association of some organic dyestuffs in aqueous solution

The temperature effects on the absorption spectra of acridine orange and methylene blue in aqueous solution at various concentrations have been observed, and it was found that the increase in temperature has an effect on the spectra similar to that of the dilution. The heats of dimerization of the dyestuffs in aqueous solution have been measured directly by the calorimetric titration method, and ΔH_d for acridine orange and methylene blue were found to be ?49.6 and ?83.3 kJ mol^?1, respectively. The entropy of dimerization values were also calculated to be ΔS_d = ?54.9 and ?211.6 J K^?1 mol^?1 for acridine orange and methylene blue, respectively. It has been concluded that the stacking interactions are primarily responsible for the self-association of the dye molecules.     

New Methylene Blue (NMB) Encapsulated in Mesoporous AlMCM‐41 Material and Its Application for Amperometric Determination of Ascorbic Acid in Real Samples

New methylene blue (NMB) dye incorporated into AlMCM‐41 surfactant‐free and hybrid surfactant‐AlMCM‐41 mesophase. UV‐vis evidence shows that new methylene blue dye protonated in both cases of zeolites. New methylene blue is electroactive in zeolites and their electrochemical activity has been studied by cyclic voltammetry and compared to that of NMB in aqueous solutions. New methylene blue molecules are not released to the solution during CV measurements and are accessible to H₃O⁺ ions. The presence of surfactant affects the kinetics of the redox process through proton ions diffusion. The midpoint potentials (E_m) values show that new methylene blue dye incorporated into AlMCM‐41 can be reduced easily with respect to solution new methylene blue. New methylene blue interacting with surfactant polar heads and residual Br^? ions as a results, it shows a couple of peaks in high potential with respect to new methylene blue solution. The electrode made with methylene blue‐AlMCM‐41 without surfactant was used for the mediated oxidation of ascorbic acid. The anodic peak current observed in cyclic voltammetry was linearly dependent on the ascorbic acid concentration. The calibration plot was linear over the ascorbic acid concentration range 1.0×10^?5 to 5.0×10^?4 M. The detection limit of the method is 1.0×10^?5 M, low enough for trace ascorbic acid determination in various real samples.     

Studies on pollutants: A new reagent for the detection of fluoride

A new solid analytical reagent is reported for the detection and semiquantitative determination of traces of fluoride. A blue (λ_max 590 nm) trypan blue dye is liberated from an insoluble zirconium-trypan blue complex by the action of fluoride in dilute acetic acid medium. The detection limit is 0.8 ppm and the range of semiquantitative determination is 0.8 to 8 ppm. The method is simple and can be conveniently used for field detection of fluoride in polluted waters.     

Clay and charcoal composites: characterisation and application of factorial design analysis for dye adsorption

The characterisation of smectite clay, charcoal and prepared clay-charcoal composites was carried out through the X-ray diffractometry, energy dispersive X-ray spectroscopy (EDS), simultaneous thermal analysis (TGA/DTA), infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The analysis revealed the composites to have different characteristics from the precursor clay and charcoal, and a peak displacement (d ₀₀₁) was observed through the X-ray diffraction; this suggests the incorporation of charcoal into the clay lamellas and the formation of a new phase. Tests of adsorption with methylene blue dye were also carried out to evaluate the percentage of dye removal by the adsorbent, in which the composites presented better results than charcoal, indicating great potential for industrial use. A 2³ factorial design was employed to evaluate the influence of temperature, ionic strength and pH on the adsorption of methylene blue using the AV₅₀ composite that presented the best adsorption efficiency.     

Kinetic catalytic determination of trace levels of iodide based on the oxidation of basic dyes with hydrogen peroxide monitored potentiometrically using simple PVC electrodes

Four sensitive catalytic potentiometric methods have been developed for trace levels determination of iodide based on its catalytic effects on the oxidation of four dyes: viz. variamine blue (VB), rhodamine B (RB), methylene blue (MB) and malachite green (MG), with H₂O₂ in H₃PO₄ medium at 25 ± 0.5 °C. The catalyzed reaction rates were estimated potentiometrically by monitoring the potential of the corresponding dye-PVC ion selective electrodes. To select the optimized reaction conditions offering the highest sensitivity of the method, parallel studies were carried out on each dye catalyzed reaction including: the effect of reactant concentration, reaction medium and temperature. The working calibration curves were linear over the concentration range from 0.32 to 2.54 mg L⁻¹ iodide for VB method and from 3.2 to 12.7 mg L⁻¹ for other ones. The tolerance limits of more than 20 interfering species were listed indicating the high selectivity of the method. Trace iodide in edible salt and pharmaceutical samples was determined without the need for separation or preconcentration procedures.     

Extraction of gold(III) from low-grade ores with amidines followed by its spectrophotometric determination with methylene blue

A procedure is described in which gold(III) is quantitatively extracted with an amidine into chloroform over the acidity range pH 3.0–11.0 M HCl, followed by its selective spectrophotometric determination by interaction of the extract with methylene blue in the pH range 3.0–9.0. The molar absorptivity of the coloured complex formed by extraction with ten different amidines and methylene blue reaction lie in the range 1.1 × 10⁴?6.5 × 10⁴ 1 mol^?1 cm^?1 at λ_max (650 nm) in chloroform. The simplest compound, N, N′-diphenylbenzamidine, was chosen for detailed study. The limit of detection is 5 μg Au l^?1. The method is free from interferences from the metals that are generally associated with gold. The method is simple, reproducible and applicable to the accurate recovery of gold from low-grade ores containing the metal at levels of > 1.5 μg g^?1.     

Photocatalytic activity of polyaniline/Fe-doped TiO2 composites by in situ polymerization method

This study was focused on the photocatalytic activity of polyaniline (Pani)/iron doped titanium dioxide (Fe–TiO₂) composites for the degradation of methylene blue as a model dye. TiO₂ nanoparticles were doped with iron ions (Fe) using the wet impregnation method and the doped nanoparticles were further combined with Pani via an in situ polymerization method. For comparison purposes, Pani composites were also synthesized in the presence undoped TiO₂. The photocatalyst and the composites were characterized by standard analytical techniques such as FTIR, XRD, SEM, EDX and UV–Vis spectroscopies. Fe–TiO₂ and its composites exhibited enhanced photocatalytic activity under ultraviolet light irradiation. Improved photocatalytic activity of Fe–TiO₂ was attributed to the dopant Fe ions hindering the recombination of the photoinduced charge carriers. Pani/Fe–TiO₂ composite with 30?wt.% of TiO₂ nanoparticles achieved 28% dye removal and the discoloration rate of methylene blue for the sample was 0.0025?min^?1. FTIR, XRD, SEM, EDX and UV–Vis spectroscopies supported the idea that Fe ions integrated into TiO₂ crystal structure and Pani composites were successfully synthesized in the presence of the photocatalyst nanoparticles. The novelty of this study was to investigate the photocatalytic activity of Pani composites, containing iron doped TiO₂ and to compare their results with that of Pani/TiO₂.     

Facile and green synthesis of Cu3V2O8 nanostructures via Moringa peregrina natural extract as a high performance photo catalyst

In this paper Cu₃V₂O₈ nanoparicles were synthesized with a low-cost and green method with using the extract of Moringa peregrine. This novel synthesized material was characterized by using X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM) and Energy-dispersive X-ray spectroscopy (EDS) analysis. The analysis showed the produced nanoparticles have high purity and well crystalline structure. Moreover, the capability of the nanostructures for the removal of dye pollutants was evaluated. For this purpose, methylene blue was selected as a model of organic dye. The experiments showed Cu₃V₂O₈ nanoparticles have high efficiency for removing of dye molecules. Photocatalytic decolorization of methyl blue was optimized with varying the experiment conditions. With 0.02 g of catalyst, pH 6 and concentration of dye 30 mg/l removal efficiency was obtained about 90% in a short time 20 min. Also a kinetic study showed this photodegradation process obeys a first-order kinetic with rate constant about 0.07 min⁻¹.     

Catalytic Spectrophotometric Determination of Titanium(IV) Using Methylene Blue‐Ascorbic Acid Redox Reaction

A highly selective and sensitive catalytic method for the determination of trace amounts of titanium(IV) was developed. The method is based on the catalytic effect of titanium(IV) on the methylene blue‐ascorbic acid redox reaction. The reaction was followed spectrophotometrically by measuring the change in absorbance of methylene blue at 665 nm, 5 minutes after the initiation of the reaction. In this study experimental parameters were optimized and the effect of the presence of various cations and some anions on the determination of titanium(IV) was examined. The calibration graph was linear in the range of 3‐25 ng mL^?1 of titanium(IV). The relative standard deviation for the determination of 10 and 20 ng mL^?1 of titanium(IV) were 2.64% and 1.51%, respectively (n = 8). The detection limit calculated from three times of standard deviation of blank 3S_b was 0.6 ng mL^?1. The method was successfully applied to the determination of titanium(IV) in tap water and ore samples.     

Synthesis,structural characterization and reactivity of manganese tungstate nanoparticles in the oxidative degradation of methylene blue

Nanoparticles of manganese tungstate (MnWO₄) were prepared via an impregnation method using Mn(NO₃)₂·4H₂O and WO₃ as a source of Mn and W, respectively. The morphology of the manganese tungstate nanoparticles was studied in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). MnWO₄ nanoparticles showed severe catalytic performances for the degradation of organic dye (methylene blue, MB) in the presence of tert-butyl hydrogen peroxide, TBHP, as the oxidant at room temperature in water.     

Numerical investigations of response surface methodology for organic dye adsorption onto Mg-Al LDH -GO Nano Hybrid: An optimization,kinetics and isothermal studies

We developed Mg-Al LDH intercalated with NO₃^- decorated Graphene Oxide nanohybrid with positive cationic textile dye adsorption, such as methylene blue. Contact time, initial dye concentration, and pH were among the independent variables used in the study. The Response Surface Model (RSM) was used to optimise and describe the interdependencies of the different variables. The method was evaluated using the Box-Behnken design (BBD). A second-order polynomial model was used to understand the experimental results, and the effectiveness of the chosen model was verified by its strong agreement in determination coefficient values. The adsorption results suited the best for the Langmuir isotherm than the D-R and Freundlich isotherms, resulting in efficient adsorption of 187.62 ?mg/g, proving LDH-GO is an effective dye adsorbent. Simultaneously, the kinetics were based on the pseudo-second-order model, and additional kinetic factors such as Elovich, pseudo-first-order, and intra-particular diffusion were examined. According to Thermodynamic studies, the adsorption process is spontaneous, which is exothermic and characterised by increased randomness. According to a regeneration test, even after four cycles, 37% of the removal efficiency for MB can be achieved. Based on this report, these materials can be used as an adsorbent to remove the dye.     

Development of non-enzymatic strip for simple and selective determination of urea in water and biological samples

A simple and selective method for the determination of urea based on the paptode technique is described. The sensor was constructed by immobilizing an ionophore on a TLC strip. The procedure is based on the nucleophilic displacement of urea with tetrachloro-p-benzoquinone (chloranil) as an ionophore, and the formed violet-color product was detected using a flatbed scanner. The color of each spot was analyzed to red (R), green (G) and blue (B) values from 0 to 255 using a program written in visual basic (VB) programming language. The calibration graph obtained with the proposed sensor was linear over the range of 0.05?C10.00?mg?L^?1 with a detection limit of 0.01?mg?L^?1 for urea. Parameters such as pH and concentration of chloranil were optimized. The proposed sensor was successfully applied for the determination of urea in bovine serum, urine and tap water samples.     

有机改性TiO2光催化剂的制备及可见光催化性能

以染料黄叱精(Chrysoidine G)和TiO₂ (Degussa P25)为原料, 利用甲苯二异氰酸酯为桥连体, 成功合成了一种有机改性的TiO₂光催化剂. 采用XRD, TEM, FT-IR, UV-Vis对所得催化剂进行了表征, 以亚甲基蓝降解为探针反应, 考察其可见光催化性能. 结果表明: 甲苯二异氰酸酯在黄叱精和TiO₂之间形成了稳定的化学键, 从而实现了对TiO₂的表面有机改性; 改性后的TiO₂在可见光区(400～550 nm)有明显的吸收; 与未改性TiO₂相比, 有机改性的TiO₂催化剂在可见光照射下表现出了很好的光催化性能.     

Structural,electrochemical, and adsorption studies of Ni and Zn benzylimidazole coordination polymers with terephthalate linkers

Two coordination polymers, [Ni(bim)₂(L1)(H₂O)₂] _n (CP-1) and [Zn(bim)(L1)(Cl)] _n (CP-2) (bim = 1-benzylimidazole, L1 = terephthalic acid), were synthesized and characterized by physicochemical and spectroscopic methods. The Ni(II) center in CP-1 is octahedral, while the Zn(II) center in CP-2 is tetrahedral. CP-1 and CP-2 were used to modify carbon paste electrodes to assess their effect on the electrochemical behavior of ferricyanide. The redox reactions of ferricyanide on both electrodes proved to be reversible and diffusion controlled, with ferricyanide diffusion coefficients for CP-1 and CP-2 of 1.88 × 10⁵ and 3.44 × 10⁵ cm² s^?1, respectively. These coordination polymers were also investigated for their adsorption behavior toward two dyes: Chicago sky blue and methylene blue. CP-1 and CP-2 both rapidly adsorbed the anionic Chicago sky blue dye by different intermolecular interactions; in contrast, the cationic methylene blue dye was adsorbed to a lesser extent. The adsorption of these CPs depends on the charge but not the size of the dye. Addition of methanolic potassium nitrate solution caused the release of the adsorbed dyes.     

A novel sensitized chemiluminescence: Infrared emissions from thiazine dyes sensitized by singlet oxygen

An unusual infrared chemiluminescence emission (8130Å) of methylene blue, and other thiazine dyes, sensitized by singlet molecular oxygen is reported. This chemiluminescence does not correspond to the ordinary fluorescence of the dye and cannot be explained by previously proposed mechanisms for singlet oxygen sensitized emissions of dyes. From energetic considerations singlet molecular oxygen in its ¹Σ_g⁺ state is postulated as the sensitizing agent for the thiazine dye chemiluminescences. Schemes in which ¹Σ_g⁺ oxygen transfers electronic excitation energy (a) to the lowest triplet state of the dye, (b) to a combined multiplicity state of the lowest triplet state of the dye, and triplet molecular oxygen, or (c) to a charge-transfer state between the dye and oxygen, are compared. The chemiluminescence of methylene blue in aqueous solution may be used as a luminescent probe for ¹Σ_g⁺ oxygen.     

Mechanism of complexation of the phenothiazine dye methylene blue with fullerene C60

The complexation of fullerene C₆₀ with the aromatic dye methylene blue (MB) in aqueous solution was studied. Spectrophotometric titration revealed a reasonably strong interaction between C₆₀ and MB molecules with an equilibrium constant K = 2110 L/mol and the binding of up to five dye molecules with the surface of C₆₀. The energy analysis of the MB-C₆₀ system showed that the intermolecular and hydrophobic interactions were dominant in the energy profile of the complexation, and while the electrostatic factor played an insignificant role.     

Photocatalytic activity of divalent ion (copper,zinc and magnesium) doped NiAl2O4

Nickel aluminate (NiAl₂O₄) and doped nickel aluminate (Ni_1-xM_xAl₂O₄; M = Mg, Zn, Cu; x = 0.1) were prepared by sol-gel method using citric acid. The synthesized compounds were analyzed by various techniques such as powder XRD, FTIR, SEM-EDAX and UV-DRS. The lattice parameter was found to increase with the copper, zinc and magnesium doping in nickel aluminate. The band gap was decreased from 3.0 eV (NiAl₂O₄) to 2.9 (zinc doped), 2.7 eV (magnesium doped) and increased to 3.1 eV in the case of copper doping. The catalytic study was carried out for a cationic (methylene blue) and an anionic dye (methyl orange). The percentage degradation of methyl orange using Zn_0.1Ni_0.9Al₂O₄ and Mg_0.1Ni_0.9Al₂O₄ was found to be 92% (180 min) and 96% (90 min). 93% (120 min) and 97% (120 min) degradation of methylene blue was observed using zinc doped and magnesium doped nickel aluminate respectively. These results are comparatively higher than its parent analogue (94% (180 min) degradation against methyl orange and 91% (120 min) against methylene blue). Whereas the percentage degradation was found to be less in the case of Cu_0.1Ni_0.9Al₂O₄ (83% (180 min) against methyl orange and 90% (120 min) against methylene blue).     

液相色谱法检测水产品中亚甲蓝及其代谢物残留

建立了液相色谱同时检测水产品中亚甲基蓝及其代谢物天青A、天青B、天青C残留的方法并用于样品检测.试样中残留的药物以含离子对试剂对甲苯磺酸的乙酸铵缓冲液-乙腈提取,二氯甲烷反萃,MCAX固相萃取小柱净化,液相色谱测定.对提取、净化及仪器分离分析条件进行了探讨,对亚甲基蓝在分析过程的稳定性进行了研究.水产品中4种化合物在0.005～0.50 mg/kg范围内线性关系良好,相关系数为0 9946～0.9978.在0.005～0.5 mg/kg浓度范围内,平均加标回收率为75.9%～93.2%; 相对标准偏差为3 3%～11.9%; AZA、AZB、AZC、MB的检出限分别为1.27、0.98、1.48和1.33μg/kg.方法稳定可靠,可满足水产品中亚甲基蓝及其代谢物的检测需要.     

DFT Study of Methylene Blue Adsorption on ZnTiO3 and TiO2 Surfaces (101)

The search for alternative materials with high dye adsorption capacity, such as methylene blue (MB), remains the focus of current studies. This computational study focuses on oxides ZnTiO₃ and TiO₂ (anatase phase) and on their adsorptive properties. Computational calculations based on DFT methods were performed using the Viena Ab initio Simulation Package (VASP) code to study the electronic properties of these oxides. The bandgap energy values calculated by the Hubbard U (GGA + U) method for ZnTiO₃ and TiO₂ were 3.17 and 3.21 eV, respectively, which are consistent with the experimental data. The most favorable orientation of the MB adsorbed on the surface (101) of both oxides is semi-perpendicular. Stronger adsorption was observed on the ZnTiO₃ surface (−282.05 kJ/mol) than on TiO₂ (–10.95 kJ/mol). Anchoring of the MB molecule on both surfaces was carried out by means of two protons in a bidentate chelating (BC) adsorption model. The high adsorption energy of the MB dye on the ZnTiO₃ surface shows the potential value of using this mixed oxide as a dye adsorbent for several technological and environmental applications.