Electro-catalytic degradation of methylene blue wastewater assisted by Fe2O3-modified kaolin

The electrochemical oxidation of methylene blue (MB) wastewater assisted by Fe₂O₃-modified kaolin in a 200 mL electrolytic batch reactor with graphite plate as electrodes was investigated. The catalyst was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effects of pH, current density and introduction of NaCl on the efficiency of the electrochemical degradation process were also studied. It was found that Fe₂O₃-modified kaolin has higher catalytic activity in the electrochemical degradation of MB wastewater. 96.47% chemical oxygen demand (COD) removal was obtained in 40 min of electrochemical treatment of MB wastewater at pH 3, current density was equal to 69.23 mA cm⁻².     

Comparative study of catalytic ozonation and Fenton-like processes using iron-loaded rice husk ash as catalyst for the removal of methylene blue in wastewater

This study intends to compare the effectiveness of catalytic ozonation and Fenton-like processes for the decolorization of methylene blue using iron-loaded rice husk ash as catalyst. In both processes, effect of initial pH, adsorption, hydroxyl radical scavenger, and chemical oxygen demand removal was studied. The results revealed that catalytic processes were found to be pH dependent with the highest activity at pH 3.0. Unlike Fenton-like process, catalytic ozonation also found to be effective at pH 7.0. It is therefore, concluded that catalytic ozonation process is more effective than Fenton-like process near wastewater pH values.     

Treatment of waters colored with methylene blue dye by vacuum membrane distillation

Textile industries consume large amounts of water and generate highly dye-contaminated effluents. Textile wastewaters have to be treated in order to be recycled in the process or to meet legislative requirements before being discharged. The objective of the present study was to examine the potential use of the vacuum membrane distillation process for the treatment of dyed solutions. Methylene blue (MB) was used as a model dye. Batch experiments were conducted on dilute MB-water mixtures using a tubular polypropylene membrane module. The concentration of MB dye within the feed reservoir was monitored over time. The impact of operating variables such as feed temperature, flow rate and initial dye concentration was investigated. A mathematical model incorporating temperature and concentration polarization effects was developed and validated on the experimental data.     

Adsorption of methylene blue from aqueous solutions by modified expanded graphite powder

The modified expanded graphite (MEG) powder was used as a porous adsorbent for the removal of the cationic dye, methylene blue (MB), from aqueous solutions. The dye adsorption experiments were carried out with the bath procedure. Experimental results showed that the basic pH, increasing initial dye concentration and high temperature favored the adsorption. The dye adsorption equilibrium was attained rapidly after 5 min of contact time. Experimental data related to the adsorption of MB on the MEG under different conditions were applied to the pseudo-first-order equation, the pseudo-second-order equation and the intraparticle diffusion equation, and the rate constants of first-order adsorption (k₁), the rate constants of second-order adsorption (k₂) and intraparticle diffusion rate constants (k_int) were calculated, respectively. The experimental data fitted very well in the pseudo-second-order kinetic model. The thermodynamic parameters of activation such as Gibbs free energy, enthalpy, and entropy were also evaluated. The results indicated that the MEG powder could be employed as an efficient adsorbent for the removal of textile dyes from effluents.     

Adsorption of methylene blue on kaolinite

Methylene blue was adsorbed on kaolin from a local deposit. The raw kaolin itself was a relatively good adsorbent. The adsorption capacity was improved by purification and by treatment with NaOH solution. Calcination of the kaolin reduced the adsorption capacity. The adsorption data could be fitted by the Freundlich and Langmuir equations. Also, the thermodynamic parameters such as ΔH⁰, ΔS⁰ and ΔG⁰ were determined.     

Binding of the phenothiazinium dye methylene blue with single stranded polyriboadenylic acid

The binding of the phenothiazinium dye methylene blue to single stranded poly(riboadenylic acid) was investigated by spectroscopic and calorimetric techniques. The binding was cooperative and the affinity was of the order of 10⁶ M⁻¹ at 100 mM [Na⁺] as determined from absorbance, fluorescence and calorimetric studies. Ferrocyanide quenching studies showed intercalative binding of methylene blue to poly(riboadenylic acid). The binding perturbed the circular dichroism spectrum of poly(riboadenylic acid) with concomitant formation of prominent exciton split type of extrinsic CD bands in the 550-700 nm region. The interaction involved a single binding mode with a 1:2 binding stoichiometry. The binding affinity increased with [Na⁺] ion concentration in the range 10-200 mM [Na⁺]. Dye binding induced self-assembled duplex formation in poly(riboadenylic acid). The biological utility of the dye methylene blue in probing nucleic acid structure is revealed from these studies.     

Adsorptive and stripping behavior of methylene blue at gold electrodes in the presence of cationic gemini surfactants

The adsorptive and stripping behavior of methylene blue (i.e. methylene blue chloride, MB) at a gold electrode has been studied with voltammetry, alternating current impedance spectra (ACIS) and quartz crystal microbalance (QCM). MB exhibits a pair of cyclic voltammetry peaks at about −0.3 V (versus SCE) in 0.05 M pH 6.9 phosphate buffer solutions. In the presence of cationic gemini surfactants such as C₁₆H₃₃N(CH₃)₂-C₄H₈-N(CH₃)₂C₁₆H₃₃Br₂ (C₁₆-C₄-C₁₆), C₁₆H₃₃N(CH₃)₂-C₄H₇OH-N(CH₃)₂C₁₆H₃₃Br₂ (C₁₆-C₄OH-C₁₆), C₁₆H₃₃N(CH₃)₂-CH₂-C₆H₄-CH₂-N(CH₃)₂C₁₆H₃₃Br₂ (C₁₆-ph-C₁₆) and C₁₆H₃₃N(CH₃)₂-C₁₂H₂₄-N(CH₃)₂C₁₆H₃₃Br₂ (C₁₆-C₁₂-C₁₆), the anodic peak grows rapidly and moves in positive direction, but the cathodic peak gradually decreases, due to the association adsorption and electrostatic interaction of the geminis with MB and its reduced product (i.e. leuko methylene blue, LMB). With the aid of geminis the adsorption amount of MB increases under open-circuit, but the impedance of the mixed adsorption film to Fe(CN)₆^3−/4− almost keeps unchanged, compared with either bare gold electrodes or MB film, while the adsorption film of geminis exhibits greater impedance. This probably is due to the electron medium action of MB in the film. Gemini surfactants with same alkyl-chain (i.e. -(CH₂)₁₅CH₃) but different molecular structure, exhibit different influence. The enhancing action of geminis studied follows such order as: C₁₆-ph-C₁₆ > C₁₆-C₄-C₁₆ > C₁₆-C₄OH-C₁₆ > C₁₆-C₁₂-C₁₆. The change of peak potential was ascribed to the interaction between MB and surfactants, as well as the blocking action of surfactant film. For comparison, the influence of dihexadecyldimethylammonium bromide (DCAB) and cetyltrimethylammonium bromide (CTAB) was studied, and the influence of other factors is discussed as well.     

Electrochemical property of methylene blue redox dye immobilized on porous silica-zirconia-antimonia mixed oxide

The mixed oxide SiO₂/ZrO₂ obtained by the sol-gel processing method adsorbs Sb(V) from acid solution, forming a new phase on the matrix surface designated as SiO₂/ZrO₂/Sb₂O₅. The amount of Zr(IV) in the matrix was 8.1 wt.%, corresponding to 0.89 mmol g⁻¹, and the amount of Sb(V) incorporated in the matrix was 6.3 wt.% (0.52 mmol g⁻¹). This material presented a specific surface area, S_BET=590 m² g⁻¹. The immobilized Sb₂O₅ is a good cation exchanger and adsorbs methylene blue (MB) cationic dye with an average surface density δ=1.1×10⁻¹¹ mol cm⁻² (about 0.07 molecule nm⁻²). The dye is strongly entrapped in the pores of the matrix and it is not leached off in KCl solutions as concentrated as 1.0 M. A carbon paste of the SiO₂/ZrO₂/Sb₂O₅/MB material showed a reversible redox pair with midpoint potential E_m=−0.1 V versus SCE. This midpoint potential is not affected by solution pH change between 2 and 7. The immobilized dye mediated NADH catalytic oxidation at ca. 50 mV.     

Effective removal of cationic methylene blue dye using nano-hydroxyapatite synthesized from fish scale bio-waste

Nano-hydroxyapatite (NHAp) with a novel rod shape was synthesized from an economical and easily accessible Labeo rohita fish scale bio-waste by facile and straightforward alkaline heat treatment method. The purity, functionality, morphology, and surface area of the green synthesized NHAp powder were well-characterized via X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET). The TEM and BET results indicate that the apatite is prepared as a rod-like particle and highly porous with high surface area (112.36 m² g⁻¹). The NHAp powder was used for the adsorptive removal of cationic dye-methylene blue (MB) from the aqueous samples. Batch experiments were performed to evaluate the mechanism of adsorption and kinetic models. The NHAp achieved an enhanced adsorption efficiency (666.67 mg g⁻¹) for the adsorption process. The obtained results perfectly obeyed the pseudo-second-order model, and the Langmuir isotherm exhibited an excellent relationship with the experimental data. Furthermore, thermodynamic studies reveal that the adsorption process was exothermic and spontaneous. Thus, the results proved that Labeo rohita fish scale bio-waste derived NHAp can be inventively utilized as a cost-effective and eco-friendly adsorbent for wastewater treatment.     

固定式填充复合床光催化反应器降解亚甲基蓝的研究

设计了一种固定式填充复合床光催化反应器,以普通玻璃片和玻璃螺旋圈为载体,用溶胶-凝胶法制备了负载型TiO2薄膜光催化剂。利用紫外光为光源,采用难降解物质亚甲基蓝在不同初始浓度、pH值和光强等因素下的光催化降解脱色反应速率考察了该反应器的工艺特性,试验结果表明:该种反应器的最佳操作条件为反应器中同时放置普通玻璃片TiO2薄膜光催化剂和玻璃螺旋圈TiO2薄膜光催化剂,溶液pH值为7.5,光源光强为650W,光照时间为180min。当进水亚甲基蓝的质量浓度为8.0mg/L时,在此条件下的降解脱色效率为93.83%,且其设计易于实现产业化。     

Application of the methylene blue test to cement raw materials

Characterisation of raw materials for Portland cement manufacture by use of the methylene blue adsorption method is discussed. The method is shown to be a simple, convenient ‘rule of thumb’ procedure. It provides a guide to the quantity and type of argillaceous minerals present in a given raw material sample.     

Visible light active Cu-doped iron oxide for photocatalytic treatment of methylene blue

In recent work, pure α-Fe₂O₃ (F-1) and series of 5% Cu doped Fe₂O₃ (CF-5) , 10% Cu doped Fe₂O₃ (CF-10) and 15% Cu doped Fe₂O₃ (CF-15) nanoparticles by facile chemical coprecipitation method were synthesized to study the effect of concentration of doping for photocatalytic activity. As prepared F-1, CF-5, CF-10, CF-15 nanoparticles were subjected to X-ray diffraction (XRD) and Fourier transform infra-red (FTIR) techniques to analyse the structural and functional groups features. These characterization techniques confirmed the successful doping of Cu ²⁺ ions in α-Fe₂O₃. The crystallite size of synthesized samples was calculated by Scherrer formula. Gradually decline in crystallite size from 18 to 15 nm was observed for undoped to doped samples. Scanning electron microscopic (SEM) analysis expressed that doping of Cu reduced the aggregation of particles and enhanced the surface area of nanoparticles. UV–Visible spectroscopic analysis of synthesized samples was used to calculate the bandgap energy of F-1, CF-5, CF-10, CF-15 nanoparticles i.e., 2.0, 1.7, 1.5, 1.4eV respectively. Narrowing bandgap energy of doped hematite supported to perform excellent photocatalytic activity. Maximum degradation of methylene blue was recorded via CF-10 within 140 min. Higher degradation rate of methylene blue by optimal concentration of CF-10 is due to effective electron trapping ability of photocatalyst.     

高岭土负载HPCS-MA对亚甲基蓝废水的絮凝性能

以羟丙基壳聚糖（HPCS）、马来酸酐（MA）为原料合成N-马来酰化羟丙基壳聚糖（HPCS-MA）。采用红外光谱（FTIR）、核磁共振氢谱（¹H NMR）对其结构进行表征。考察了缚酸剂三乙胺用量、反应温度、反应时间及马来酸酐用量对产物羧基含量及特性黏数的影响。结果表明：在缚酸剂用量为5g，反应温度65℃，反应时间6h，马来酸酐用量为4.5g的条件下，产物的羧基含量和特性黏数均达到较佳值，为83.50%和211.96mL/g。利用高岭土负载HPCS-MA处理亚甲基蓝印染废水，研究了pH、投加量、絮凝温度、初始浊度对亚甲基蓝染料脱色性能的影响。结果表明，在亚甲基蓝浓度为3×10^-5mol/L的印染废水中，HPCS-MA絮凝脱色的适宜条件为：pH为1～5，投加量为4～8mg/L，温度为20～25℃，浊度为200～400NTU，在此条件下色度去除率均在96.5%以上。     

Ag-ZnO catalysts for UV-photodegradation of methylene blue

High surface area Ag-ZnO catalysts have been made by flame spray pyrolysis (FSP) and characterized by X-ray diffraction (XRD), nitrogen adsorption, UV–vis spectroscopy and electron microscopy (SEM and transmission electron microscopy (TEM)) combined with energy dispersive X-ray spectroscopy (EDXS) for elemental mapping. Silver metal clusters deposited directly on ZnO nanocrystals were obtained from this process. The Ag loading (1–5 at.%) controlled the Ag cluster size from 5 to 25 nm but did not influence the ZnO crystal size. Photodegradation of 10 ppm methylene blue (MB) solution was used to evaluate the performance of these FSP-made Ag-ZnO and was compared to wet-made Ag-ZnO and reference titania photocatalysts. The rate of photodegradation was optimal for Ag loading around 3 at.%. The best photocatalytic performance was exhibited by flame-made Ag-ZnO produced at the longest high-temperature residence times having high crystallinity as determined by XRD and UV–vis.     

Adsorption and photocatalytic decomposition of methylene blue on mesoporous metallosilicates

Mesoporous silica and mesoporous metallosilicates with Al, Ti and Fe as foreign metal species were successfully synthesized by the rapid room temperature method. Mesoporous metallosilicates with low contents of foreign metals possessed high surface area (S_a), large mesopore volume (V_mp) and highly ordered hexagonal mesoporous structure. Increases in foreign metal contents caused disordering the mesoporous structures and lowering the S_a and V_mp values. Bleaching of aqueous methylene blue (MB) by mesoporous silica and metallosilicates was investigated. Mesoporous aluminosilicate and ferrosilicate with cation-exchangeable ability showed the excellent property for the adsorption of MB of cationic dye, while mesoporous ferrosilicate and titanosilicate which absorbed UV lights catalyzed the photocatalytic decomposition of MB under UV-illumination.     

Preparation of reusable glass hollow fiber membranes and methylene blue adsorption

In this work, the PVDF/glass as-prepared composite membrane was prepared through phase-inversion method and used to adsorb methylene blue dye. The results of SEM and BET showed that the membrane had an asymmetric nanoscale porous structure. The electronegativity on the surface of membrane was determined through zeta potential test. The adsorption properties of as-prepared composite membrane and glass membrane were studied through testing the removal ratio of methylene blue from aqueous solution. Then the effects of membranes dose, pH value, temperature and initial concentration on the removal ratio were systematically studied. The adsorption mechanism was also studied. The adsorption kinetics and adsorption isotherm fitted well with the pseudo-second-order model and Freundlich model, respectively. In addition, the adsorption efficiency of glass membrane basically remained 85% after eight repeated adsorption-calcination cycles. The obtained membranes could be reused for methylene blue removal with high efficiency for multiply times.     

Photoelectrocatalytic determination of NADH in a flow injection system with electropolymerized methylene blue

It was firstly described that a glassy carbon electrode electropolymerized with methylene blue shows an efficient photoelectrocatalytic activity towards NADH oxidation in a phosphate buffer solution (pH 7.0). In order to perform the photoelectrocatalytic determination of NADH in a flow injection analysis (FIA) system, a home-made flow electrochemical cell with a suitable transparent window for the irradiation of the electrode surface was constructed. The currents obtained from the photoamperometric measurements in the FIA system at optimum conditions (flow rate of carrier solution, 1.3 mL min⁻¹; transmission tubing length, 10 cm; injection volume, 100 μL; and constant applied potential, +150 mV vs. Ag/AgCl) were linearly dependent on the NADH concentration and linear calibration curves were obtained in the range of 1.0 × 10⁻⁷–2.0 × 10⁻⁴ M. The detection limit was found to be 4.0 × 10⁻⁸ M for photoamperometric determination of NADH.     

曙红亚甲基蓝分光光度法测定水中阳离子表面活性剂

采用分光光度法测定水样中阳离子表面活性剂的含量。在弱酸性的HCl-NaAc缓冲介质中,阳离子表面活性剂十六烷基溴化吡啶(CPB)以及十六烷基三甲基溴化铵(CTAB)能与曙红亚甲基蓝反应,形成离子缔合物,后者的最大吸收波长分别为660 nm和658 nm,且阳离子表面活性剂的浓度与溶液的显色程度呈良好线性关系。在最大吸收波长处,CPB和CTAB的浓度分别在0~2.10×10-5mol/L和0~1.98×10-5mol/L范围内遵守比尔定律,表观摩尔吸光系数分别为1.79×104L/(mol.cm)和1.38×104L/(mol.cm),检出限分别为8.27×10-7mol/L和9.88×10-7mol/L,平均回收率为99.5%~102.6%。方法具有较高的灵敏度和良好的选择性,可用于水样中阳离子表面活性剂的测定。     

Spectral and electrochemical studies of methylene blue and thionine encapsulated in zeolite-Y

Investigation on the spectral and electrochemical properties of methylene blue and thionine encapsulated in zeolite-Y is carried out. Both the dyes exist as monomer and H-aggregates in zeolites and the ratios for the aggregates of the dyes are different at the zeolite surface even though the dyes have similar basic structure. The electrochemical behaviour of thionine and methylene blue at zeolite modified electrode shows that both the dyes experience different environment at zeolite modified electrode and the presence of methyl groups in methylene blue plays a vital role in stabilizing the electroactive species at the electrode surface. The concentration of the supporting electrolyte is found to influence the nature of the redox process.