Simultaneous determination of methylene blue and new methylene blue by slab optical waveguide spectroscopy and artificial neural networks

A slab optical waveguide (SOWG) has been used for study of adsorption of both methylene blue (MB) and new methylene blue (NMB) in liquid-solid interface. Adsorption characteristics of MB and NMB on both bare SOWG and silanized SOWG by octadecyltrichlorosilane (ODS) were compared. The simultaneous determinations of both MB and NMB were explored by flow injection SOWG spectrophotometric analysis and artificial neural networks (ANNs) for the first time. Concentrations of MB and NMB were estimated simultaneously with the ANNs. Results obtained with SOWG were compared with those got by conventional UV-visible spectrophotometry.     

Development of a novel electrochemical cell for slab optical waveguide spectroscopy for in situ observation of methylene blue and anions on an electrode/electrolyte interface

A new spectroelectrochemical cell for slab optical waveguide (SOWG) spectroscopy was developed in order to observe in situ an electrode/electrolyte interface for bulk electrolysis. The new SOWG spectroelectrochemical cell has been evaluated by simultaneous electrochemical-absorption experiments of methylene blue (MB) using cyclic voltammetry (CV) and SOWG spectrometry. CV was performed in the SOWG spectroelectrochemical cell using indium tin oxide (ITO) coated glass as the working electrode, platinum wire as the counter electrode and a silver/silver chloride electrode (Ag/AgCl) as the reference electrode. Based on the CV and SOWG spectrometric data, it was found that the SOWG spectra showed the MB spectra on the electrode surface selectively and that SOWG with the cell would be useful as a tool for in situ study of an electrode/electrolyte interface. Using this cell, the effects of the supporting electrolytes, NaNO₃, KNO₃, CH₃COONa, and CH₃COOK on the absorbance of MB were examined at the potential of +0.8 V versus Ag/AgCl. The decrease in MB absorbance by nitrate ions was greater than that of acetate ions. Therefore the competitive adsorption of nitrate ions was stronger than that of acetate ions. Thus, the decrease in absorbance of MB in the presence of anions demonstrates the competitive adsorption of anions. These results show that the extent of specific adsorption of electrolytes was observed by measuring the SOWG absorbance intensity of MB.     

A sub-second, time-resolved, linear dichroism measurement system for visible attenuated total reflection spectroscopy with a slab optical waveguide

A sub-second, time-resolved, linear dichroism (LD) measurement system was constructed, fitted with a slab optical waveguide (SOWG), and utilized to observe the adsorption process of methylene blue (MB) onto silica surfaces. In the system, a semiconductor laser (670 nm) was used as the light source and the out-coupled beam from the SOWG was split by a polarizing beam splitter into two polarized beams (TE and TM modes) to allow sequential linear dichroic ratio data to be obtained; the acquisition rate was 11 data sets per second. For an MB solution that contained no sodium dodecylbenzenesulfonate (DBS), in contact with a bare silica surface, a clear decrease occurred in the average orientation angle of adsorbed MB in the initial stages of the adsorption process. This result may correspond to a change in the chemical form of MB from monomer to dimer.     

Pulse radiolysis of methylene blue and toluidine blue in PVA

Pulse radiolysis experiments were carried out with aqueous solutions of thionine dye methylene blue (MB) and toluidine blue in the presence of polyvinyl alcohol. The transient spectra obtained show maxima at 400 and 880 nm and are assigned to the respective semiquinone radical anions. The semiquinone radical decayed by a second order process. Furthermore, MB in PVA films were bleached by γ-radiolysis and the change in absorption was found to be linear with the dose.     

Electrochemical detection of DNA hybridization using methylene blue and electro-deposited zirconia thin films on gold electrodes

A novel electrochemical DNA biosensor based on methylene blue (MB) and zirconia (ZrO₂) thin films modified gold electrode for DNA hybridization detection is presented. Zirconia thin films were electrodynamically deposited onto the bare gold electrode in an aqueous electrolyte of ZrOCl₂ and KCl by cycling the potential between −1.1 and +0.7 V (versus Ag/AgCl) at a scan rate of 20 mV s⁻¹. Oligonucleotide probes with phosphate group at the 5′ end were attached onto the zirconia thin films because zirconia is affinity for phosphoric group. The surface density of the immobilized DNA molecules at the zirconia interface was investigated by fluorescence spectroscopy method. Hybridization was induced by exposure of the ssDNA-containing Au electrode to complementary ssDNA in solution. The decreases in the peak currents of MB, an electroactive label, were observed upon hybridization of probe with the target. The cathodic peak current (i_p) of MB after hybridization with the target DNA was linearly related to the logarithmic value of the target DNA concentration ranging from 2.25×10⁻¹⁰ to 2.25×10⁻⁸ mol l⁻¹. A detection limit of 1.0×10⁻¹⁰ mol l⁻¹ of oligonucleotides can be estimated.     

Removal of methylene blue by tea wastages from the synthesis waste waters

The tea wastages could remove methylene blue（MB） as a cationic dye from waste water corresponding to second-order kinetic model.Thermodynamic studies showed that adsorption equilibrium constant（K_L） and maximum adsorption capacities(Q_max) were increased with increasing temperature.The removal efficiency of MB for Co 0.01 mmol/L at optimum conditions was about 85%. The maximum uptake capacity(Q_max) of methylene blue in a batch reactor was 0.328,0.542 and 0.659 mmol/g at 15,25 and 40℃, respectively.The enthalpy change（ΔH） and entropy change（ΔS） were 11.356 kJ/mol and 20.563 J/（mol K）,respectively.     

Comparative adsorption of methylene blue by magnetic baker’s yeast and EDTAD-modified magnetic baker’s yeast: Equilibrium and kinetic study

Magnetic baker’s yeast (MB) was prepared using glutaraldehyde cross-linking method and chemical modification with ethylenediaminetetraacetic dianhydride (EDTAD). The fabricated EDTAD-modified magnetic baker’s yeast (EMB) was then employed to remove methylene blue. Comparative adsorption of methylene blue by EMB and MB was systematically investigated with respect to pH, contact time, initial concentration and reaction temperature. The mechanism of methylene blue adsorption by EMB and MB was investigated by SEM, FTIR and Special surface area using methylene blue method. The results revealed that Fe₃O₄ nanoparticles were steadily cross-linked/incorporated with baker’s yeast biomass and the EDTA was modified on the surface of the magnetic baker’s yeast. The equilibrium adsorption data were fitted better by Langmuir isotherm, and the specific surface areas were 42.953–226.07 m²/g for MB and 94.972–499.85 m²/g for EMB, respectively. Kinetic studies suggested that the pseudo-second-order model was suitable to describe the adsorption process. Thermodynamic studies indicated that the adsorption was feasible, spontaneous and endothermic. The recovery efficiencies were above 80% by using 0.1 M HCl.     

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.     

Synthesis of NiO coated chitosan-cenosphere buoyant composite for enhanced adsorptive removal of methylene blue

The objective of the present study is to utilize fly ash cenosphere to remove methylene blue (MB) from the water streams. Nickel oxide is a typical semiconductor used as proficient adsorbent material for degradation of dye with environment friendly applications due to its excellent chemical stability and high catalytic activity. The chitosan cenosphere buoyant composite coated with NiO was synthesized with hydrothermal grafting reaction using silane coupling agent and epichlorohydrin as a cross-linking reagent. The batch adsorption experiments were carried out with a cationic dye, methylene blue as a representative organic pollutant to investigate the adsorptive capabilities of the composite as adsorbent. The influence of pH (2-12), initial concentration of dye (50–200 mg/L), temperature (37–47 °C) and contact time (0–24 h) were taken as parameters in the study. On the relative elimination of MB, the effect of time and temperature were investigated. The adsorption kinetics for MB was correlated and found to observe the pseudo-second order kinetic model, whereas the equilibrium adsorption isotherm follows the Langmuir model (R² > 0.99). The results indicate that the floating fly ash cenosphere coated with NiO proved to be more responsive for enhanced degradation of methylene blue.     

Amperometric immunosensors based on layer-by-layer assembly of gold nanoparticles and methylene blue on thiourea modified glassy carbon electrode for determination of human chorionic gonadotrophin

Nano-Au and methylene blue (MB) were assembled layer-by-layer (LBL) into films on the glassy carbon electrode modified by thiourea for detection of human chorionic gonadotrophin (HCG). The electrode modification process was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron micrograph (SEM). The factors influencing the performance of the amperometric immunosensor were studied in detail. Tests performed with this immunosensor showed good linearity, the working range for the system was 1.0–100.0 mIU/mL with a detection limit of 0.3 mIU/mL at 3σ. Moreover, the studied immunosensor exhibited high sensitivity and long-term stability. The present work supplied a promising test method for clinical immunoassay.     

Sensitive measurement of methylene blue active substances by attenuated total reflection spectrometry with a trimethylsilane-modified glass slab optical waveguide

Attenuated total reflection spectrometry with a slab optical waveguide (SOWG) was explored for the simple, rapid and sensitive measurement of total anionic surfactants by the methylene blue active substance (MBAS) method. A fused-silica sheet used as a guiding layer was modified with trimethylsilane (TMS) to extract and concentrate the MBASs on the SOWG surface. Based on preliminary studies of the adsorption behavior and visible ATR spectrum of MB on the modified silica surface, a detection wavelength of 600 nm was chosen for the sensitive measurement of anionic surfactants. When the concentration of MB was set at 10 microM in the final measurement solution, the calibration curve for a typical anionic surfactant (sodium dodecylbenzenesulfonate) was linear up to 0.6 microM and the detection limit was 0.07 microM. The proposed method was applied to the determination of total anionic surfactants in river water.     

Green synthesis of loofah-based biosorbent via radiation grafting for effective removal of methylene blue

A new loofah-based biosorbent with high adsorption capacity for cationic dye was synthesized by a one-step co-radiation grafting method. The successful grafting of sodium 4-vinylbenzene sulfonate (SSS) onto loofah sponge (LFs) through electron beam radiation can significantly improve the remove capacity of methylene blue in wastewater. The biosorbent with a 409.67 mg/g of uptake capacity for methylene blue (MB), was higher than most of the loofah based adsorbents reported. FT-IR, elemental analysis, XRD, SEM and TG were used to analyze the changes in the functional group composition, element content, morphology, thermal stability of the obtained biosorbent. The pH, contact time, temperature and the effect of dosage on adsorption were also investigated. The results showed that the adsorption behavior well accorded with the pseudo-second-order kinetic and Langmuir adsorption model, which proved that the adsorption was a single-layered and chemisorption process. The thermodynamic parameters suggested a spontaneous and endothermic process. XPS analysis confirmed a potential adsorption mechanism was based on hydrogen bond interaction, electrostatic interaction and π-π stacking. Additionally, the adsorbent owned outstanding reusability, which could be reused five times with a slight reduction of removal rate. Overall, this research enriches the MB trapping agent and provides a new methods for the reuse of waste natural loofah sponge, and it will be a valuable research with the advantages of low cost and less environmental pollution.     

Functionalization effect of Fe-type MOF for methylene blue adsorption

Water pollutant such as dyes had danger the water quality. Todays, porous materials are great potential for dye adsorption from water bodies. In this study, the iron-based metal–organic framework (MOF-Fe) of MIL-101 is synthesized through a facile solvothermal method. The amine-functionalization effect of the MOF-Fe (amine-MOF-Fe) is evaluated for the adsorptive removal of methylene blue (MB) from aqueous solution. The adsorption behaviour had shown a rapid MB adsorption within the first hour of the process due to the pore-filling mechanism of the porous MOF-Fe structure. The electrostatic interaction between the amino group of amine-MOF-Fe and MB had contributed to the high adsorption capacity. The amine-functionalization effect also found the amine-MOF-Fe is having two times higher adsorption capacity when used with the loading two times lower than non-functionalized MOF-Fe. The maximum equilibrium adsorption capacities were measured at 149.25 and 312.5 mg/g with optimum MOFs loading of 0.8 and 0.4 g/L for MOF-Fe and amine-MOF-Fe, respectively. The adsorption mechanism proposed includes the electrostatic interaction, pore filling, hydrogen bonding, and π–π stacking. The regeneration study showed the MOFs could be recycled without interfering with the removal efficiency. Hence, the results indicate that the MOFs had desirable reusability for the practical adsorption of cationic dyes with its features of fast adsorption and high capacity.     

Removal of methylene blue by seed-watermelon pulp-based low-cost adsorbent: Study of adsorption isotherms and kinetic models

Based on the abundance of seed-watermelon pulp (SWP) in Xinjiang, China, SWP was employed to prepare low-cost adsorbent toward the removal of methylene blue (MB). The effects of contact time at different initial concentration were studied. The widely used adsorption isotherm models including Langmuir, Freundlich, and Temkin isotherms were employed to depict the adsorption process. The Langmuir isotherm was best fitted to the experimental data. Batch kinetic studies showed that an equilibrium time of 300 minutes was needed for the adsorption. The adsorption properties can be well described by pseudo-second-order kinetic model and the MB uptake was not controlled by intraparticle diffusion mechanism.     

Removal of methylene blue by two zeolites prepared from naturally occurring Egyptian kaolin as cost effective technique

The optimum condition as well as adsorption behavior of two zeolite types prepared from Egyptian kaolin (namely, zeolite A and zeolite X) with methylene blue (MB) are demonstrated in this study. This will be a step to remove such dyes from textile as well as dying industries.MB removal was investigated using synthetic solutions at initial concentrations 15 mg/L of MB at constant temperature and pH (25 ± 0.1 °C and 7.5 ± 0.2) respectively. The removal efficiency was determined at different contact times and different zeolite doses.The optimum contact times for the removal of MB were 60 min and 75 min for zeolite X and zeolite A, respectively. 0.6 g was the optimum dose for removal of MB with both zeolite types.The batch method has been employed, using MB concentration in solution ranging from 2 to 25 mg/L. The percentage removal and distribution coefficients (K_d) were determined for the adsorption system as a function of sorbate concentration. The isothermal models investigated in this study show that adsorption ratios of MB on both zeolites match to Langmuir and Freundlich equation adding to that every equation constant has been calculated. According to the equilibrium studies, adsorption of zeolite X in higher concentrations is much better than that of zeolite A. Dublin–Kaganer–Radushkevich (DKR) shows physisorption endothermic adsorption process for both zeolites and also linear correlation of Redlich–Peterson and Tekman isothermal models were proved.These results show that zeolites prepared from naturally abundant Egyptian kaolin hold great potential to remove dying materials such as MB from wastewater. This will encourage using such low cost technique in removal of dyes from industrial wastewater.     

表面活性剂改性有机沸石对废水中亚甲基蓝的吸附行为

用表面活性剂十六烷基三甲基溴化铵(CTMAB)和十二烷基硫酸钠(SDS)复合改性沸石,制备了阴阳离子表面活性剂改性沸石,利用X射线衍射和红外吸收光谱表征了改性前后沸石的结构,并研究了改性沸石对亚甲基蓝的吸附行为.结果表明,改性后沸石的吸附性能明显增强;在溶液pH 8、常温,吸附时间100 min、改性沸石用量20 g/...     

Review on recent advances of carbon based adsorbent for methylene blue removal from waste water

The growth in textile and printing industries proven detrimental to the aquatic environment as the industrial waste containing dye seeped into the ecosystem. A high concentration of dye in water possess negative impacts on water ecosystem and harmful to human health. Removal of methylene blue (MB) dye from industrial waste via adsorption pathway has been widely investigated that promised high efficiency of MB removal. This review will summarize researches published from 2008 to 2019 on the removal of MB using carbon adsorbent with focus will be given on the synthesis and modification of carbon-based materials, and the structural properties influencing the performance of MB adsorption. Summary on the type of material used for the synthesis of carbon materials (activated carbon and biochar) will be included from utilization of the naturally occurring carbon sources such as polymers, biomasses and biowastes, and also sucrose and hydrocarbon gases. Modification of carbon materials such as chemical activation and physical activation; surface grafting to form functionalized surfaces; deposition with metal and magnetic nanoparticles via impregnation; and manufacturing of carbon composites will be discussed on the effects to promote MB adsorption and desorption. Another type of carbon adsorbents such as porous carbon; graphitic carbons including graphite, graphene, graphene oxide, and carbon nitride (g-C₃N₄); and finally nanocarbon in the form of nanotube, nanorod and nanofiber; will be included in the review with details on the synthesis method and the correlation between structural properties and adsorption activity. The regeneration process to increase the life cycle of carbon adsorbent will also be discussed based on two regeneration pathway i.e. a thermal degradation and desorption on MB. Finally the thermodynamics, kinetics, and the adsorption models of MB on carbon adsorbent will be discussed in this review.     

基于医用纱布负载的二氧化锰纳米颗粒用于亚甲蓝染料的去除

以医用纱布(medical gauze,MG)同时作为模板和还原剂,通过原位氧化还原反应,简便地制备了MG负载的MnO₂纳米颗粒(MnO₂ NPs/MG),并对其形貌、成分进行表征。结果表明,MnO₂ NPs均匀地分散于MG纤维表面。结合MnO₂纳米材料的吸附性能和MG复合材料的操作便捷性,将MnO₂ NPs/MG进一步应用于亚甲蓝染料的去除。结果表明,在中性条件下,通过简单的浸泡搅拌,MnO₂ NPs/MG对亚甲蓝的去除率可达85.09%,并且可以通过增大吸附材料用量与染料初始浓度的比例提高去除率。等温吸附和动力学研究证明,MnO₂ NPs/MG对亚甲蓝的吸附符合Langmuir吸附等温模型和拟二级动力学模型。     

基于医用纱布负载的二氧化锰纳米颗粒用于亚甲蓝染料的去除

以医用纱布（medical gauze,MG）同时作为模板和还原剂,通过原位氧化还原反应,简便地制备了MG负载的MnO₂纳米颗粒（MnO₂ NPs/MG）,并对其形貌、成分进行表征。结果表明,MnO₂ NPs均匀地分散于MG纤维表面。结合MnO₂纳米材料的吸附性能和MG复合材料的操作便捷性,将MnO₂ NPs/MG进一步应用于亚甲蓝染料的去除。结果表明,在中性条件下,通过简单的浸泡搅拌,MnO₂ NPs/MG对亚甲蓝的去除率可达85.09%,并且可以通过增大吸附材料用量与染料初始浓度的比例提高去除率。等温吸附和动力学研究证明,MnO₂ NPs/MG对亚甲蓝的吸附符合Langmuir吸附等温模型和拟二级动力学模型。     

Catalytic degradation of methylene blue in aqueous solutions over Ni- and Co- oxide systems

The oxidative catalytic degradation of the cationic dye methylene blue (MB) with NaOCl in aqueous solutions was studied using individual and iron modified Ni- and Co-oxide systems as catalysts. The adsorption extent and the contribution of the uncatalyzed oxidation on the overall degree of MB were determined. The results indicate that methylene blue—a representative of a class of dyestuffs resistant to biodegradation—could be successfully decolorized and degraded using nickel and cobalt oxide catalysts at room temperature. The highest catalytic activity manifests in the Co-oxide system which is consistent with the adsorption data. The oxidative degradation reaction proceeds via first-order kinetics. Temperature has a relatively small effect on the methylene blue degradation kinetics. The results obtained reveal that the catalysts investigated are suitable for oxidative destruction of methytlene blue dye in wastewaters.