Methylene Blue Retention Research Articles

Copolymeric hydrogels with high capacities of hydration and methylene blue adsorption in water

Copolymers based on monomethyl hydrogen itaconate (βHI) with 2-hydroxyethyl methacrylate (HEMA) and βHI with 2-hydroxypropyl methacrylate (HPMA) were prepared in different monomer molar ratios. The reactivity parameters of copolymerization (r1 and r2) were determined. The values obtained for r1 and r2 indicate that P(βHI-co-HEMA) exhibits a high tendency towards alternate copolymerization. Structural characterization of the copolymeric hydrogels was carried out using Fourier transform infrared (FTIR) and 1H NMR spectroscopies, where the characteristic signals of the constituent functional groups were observed. The typical thermal stability of the polymeric systems was observed by thermogravimetric analysis (TGA). In addition, the swelling capacity in water was evaluated, and a swelling percentage over 655 % and 1249 % presented P(βHI-co-HEMA) and P(βHI-co-HPMA) respectively, in a period of 15 days at pH 10, and presence of 0.05 M NaNO3.Additionally, methylene blue (MB) adsorption capacity was studied in batch mode by varying different experimental parameters. MB adsorption capacity of 122.79 mg g−1 and 112.24 mg g−1 were achieved for P(βHI-co-HEMA) and P(βHI-co-HPMA), respectively. The data obtained were fitted to the Elovich kinetic model and to a Redlich-Peterson isotherm. The thermodynamic parameters indicated that the adsorption phenomenon is spontaneous, endothermic and with a high probability of occurrence. The adsorption efficiency decreases by approximately 60 % in the presence of interfering ions (Na+, K+, Ca2+ and Cl−). The adsorbents are reusable and achieve high MB adsorption efficiency (90 % and 80 % for P(βHI-co-HEMA) and P(βHI-co-HPMA) respectively) in a textile-simulated wastewater. Based on the results obtained, it is concluded that P(βHI-co-HEMA) and P(βHI-co-HPMA) show great potential for use in adsorption of water molecules, for MB retention and purification of simulated effluents from the textile industry.

Improving separation efficiency of various micropollutants from water by polymer-enhanced ultrafiltration using oxidized alginate featuring less viscous and low filtration resistance

Polymer-enhanced ultrafiltration (PEUF) is an economical and energy-efficient alternative using a versatile water-soluble polymer (WSP) to remove micropollutants by electrostatic interactions, allowing size exclusion through ultrafiltration (UF) membranes due to the WSP being bigger than the pores of UF membranes. However, the WSP used in PEUF is so viscous that it inevitably causes significant filtration resistance and membrane fouling, reducing filtration and energy efficiency. To overcome this problem, in this study, sodium alginate (Alg), which significantly performs in removing cationic pollutants, was oxidized using sodium periodate to produce oxidized alginate (OxAlg). The retention and water flux profiles of OxAlg for three micropollutants, methylene blue (MB), ciprofloxacin, and tetramethylammonium hydroxide, using the PEUF method were investigated in terms of pH, ionic strength, polymer and pollutant amount. A comparison between Alg and OxAlg demonstrated 1.19% to 1.8% higher MB retention rates (99.31%-99.97%) and up to 4.07 times higher water flux depending on the amount of polymer added. Furthermore, OxAlg displayed excellent retention rates of the NF level and 20-60 times higher water flux than typical NF. This outstanding OxAlg performance was mainly due to OxAlg’s properties, such as the low viscosity, flexibility and the resulting accessibility, and appropriate size from the perspective of filtration. Lastly, OxAlg was found to have the potential to surpass the existing WSP in that it showed a higher maximum retention capacity than about 560 to 1250mg/g in the real-world pH enrichment test even before the saturation.

Mucoadhesive liquid crystal precursor system for photodynamic therapy of oral cancer mediated by methylene blue

Oral cancer is one of the most prevalent types of cancer head and neck cancers worldwide. Photodynamic therapy (PDT) has demonstrated great potential against cancers, reducing long-term morbidity. In this study, we investigated the incorporation of methylene blue (MB) in a mucoadhesive liquid crystal precursor system (LCPS) for oral cancer treatment. The photostability and the in vitro release, permeation, and retention profile of MB-loaded LCPS (MB-LCPS) were investigated, as well as its in vitro PDT activity against normal (HaCaT) and tumoral (HSC-3) cell lines. LCPS increased the photostability of MB and exhibited a prolonged release profile of MB. In addition, LCPS increased the retention of MB in the porcine esophageal mucosa by around 3 times higher than the MB solution. The retention of MB in LCPS was around 2 times greater than its permeability, which is suitable for guaranteeing the maintenance of the therapy in the oral cavity. In vitro cytotoxicity assay indicated that MB-LCPS increased the antitumoral activity of MB after 20 min of irradiation at 660 nm and 12.5 J/cm2. The results obtained suggest that the developed formulation is an interesting strategy for the potential application in the treatment of oral cancer by PDT.

Monoolein-based nanodispersions for cutaneous co-delivery of methylene blue and metformin: Thermal and structural characterization and effects on the cutaneous barrier, skin penetration and cytotoxicity

This study evaluated the potential of monoolein (MO)-based nanodispersions to promote the cutaneous co-delivery of metformin (MET) and methylene blue (MB) for the treatment of non-melanoma skin cancer. MO-based nanodispersions were obtained using Kolliphor® P407 (KP) and/or sodium cholate (CH), and characterized concerning the structure, thermal stability, ability to disrupt the skin barrier, cutaneous permeation and retention of MB and MET. Additionally, the cytotoxic effect of MO nanodispersions-mediated combination therapy using MET and MB in A431 cells was evaluated. The nanodispersions exhibited nanometric size (<200 nm) and thermal and physical stability. Small angle X-ray scattering studies revealed multiple structures depending on composition. They were able to interact with stratum corneum lipid structure, increasing its fluidity. The effect of MO-nanodispersions on topical/transdermal delivery of MB and MET was composition-dependent. Nanodispersions with low MO content (5 %) and stabilized with KP and CH (0.05–0.10 %) were the most promising, enhancing the cutaneous delivery of MB and MET by 1.9 to 2.2-fold and 1.4 to 1.7-fold, respectively, compared to control. Cytotoxic studies revealed that the most promising MO nanodispersion-mediated combination therapy using MET and MB (1:1) reduced the IC50 by 24-fold, compared to MB solution, and a further reduction (1.5-fold) was observed by MB photoactivation.

Desorption Studies for Methylene Blue Dye Removal by Kaolinite

In wastewater treatment, the reusability of an adsorbent strongly relies on the feasibility of contaminant desorption from the spent adsorbent. This research aims to investigate the Methylene Blue (MB) release from the spent kaolinite clay mineral against a variety of desorbing eluent in an aqueous solution. Malaysia’s kaolinite was characterised using Scanning Electron Microscopy (SEM), surface area analysis, and Fourier Transform Infrared (FTIR) Spectroscopy. The MB desorption was performed using eluents of distilled water, solutions of HCl, NaOH, and NaCl (0.01 M and 0.1 M), and ethanol: water mixtures (30:70, 50:50, and 70:30 v/v ratios). It was found that the MB desorption only occurs in 0.1 M NaOH (pH 12.7). A 4.2% MB desorption was recorded in 1 hour and was increased to 19.5% within 24 hours desorption time. The pH change measurement also reveals the favorability for highly alkaline conditions for MB desorption. The overall finding indicates that the MB retention towards kaolinite is strong, and its adsorption occurs via electrostatic and hydrophobic interaction, as suggested by the FTIR analysis. Kaolinite is a good scavenger for removing the MB dye from contaminated water but requires a strong eluent in the desorption process for its future reusability process.

Enhanced Dye Adsorption of Mixed‐Matrix Membrane by Covalent Incorporation of Metal‐Organic Framework with Poly(styrene‐alt‐maleic anhydride)

AbstractIn this study, a novel mixed‐matrix membrane (MMM) based on covalent incorporation of poly(styrene‐alt‐maleic anhydride) (PSMA) with a metal‐organic framework (MOF) UiO‐66‐NH2 was prepared and utilized for dye removal from aqueous solution. The fabrication of PSMA and UiO‐66‐NH2 was carried out by the amidation reaction between the maleic anhydride ring and amino functional group affording crosslinked MOF/PSMA membrane. The separate UiO‐66‐NH2 and PSMA solutions were mixed before cast films were produced. The MMM was prepared with final UiO‐66‐NH2 wt % content from 0 to 30 % in each membrane. The formation of MMM was confirmed with FT‐IR, PXRD, TGA, SEM, and XPS analysis. The MMM having high adsorption capacity was used for the separation of methylene blue (MB) and methyl orange (MO) as organic dye pollutants commonly found in wastewater. The MMM could be recycled and still maintained 75 and 52 % retention of MB and MO on the third reuse cycle, respectively. The results suggest that the MOF incorporated PSMA was an outstanding membrane for the development of filtration techniques for decontamination of water resources.

Synergistic Photoantimicrobial Chemotherapy of Methylene Blue-Encapsulated Chitosan on Biofilm-Contaminated Titanium.

Intensive efforts have been made to eliminate or substantial reduce bacterial adhesion and biofilm formation on titanium implants. However, in the management of peri-implantitis, the methylene blue (MB) photosensitizer commonly used in photoantimicrobial chemotherapy (PACT) is limited to a low retention on the implant surface. The purpose of this study was to assess enhancive effect of water-soluble quaternary ammonium chitosan (QTS) on MB retention on biofilm-infected SLA (sandblasted, large grid, and acid-etched) Ti alloy surfaces in vitro. The effectiveness of QTS + MB with different concentrations in eliminating Gram-negative A. actinomycetemcomitans or Gram-positive S. mutans bacteria was compared before and after PACT. Bacterial counting and lipopolysaccharide (LPS) detection were examined, and then the growth of human osteoblast-like MG63 cells was evaluated. The results indicated that the synergistic QTS + MB with retention ability significantly decreased the biofilm accumulation on the Ti alloy surface, which was better than the same concentration of 1 wt% methyl cellulose (MC). More importantly, the osteogenic activity of MG63 cells on the disinfected sample treated by QTS + MB-PACT modality was comparable to that of sterile Ti control, significantly higher than that by MC + MB-PACT modality. It is concluded that, in terms of improved retention efficacy, effective bacteria eradication, and enhanced cell growth, synergistically, PACT using the 100 μg/mL MB-encapsulated 1% QTS was a promising modality for the treatment of peri-implantitis.

Diagnostic efficiency of methylene blue and lugol's iodine double staining method in oral leukoplakia in detecting dysplasia.

Early detection of dysplasia in oral potentially malignant disorders (PMD) might facilitate screening for possible subsequent malignant transformation. Vital staining is a non-invasive clinical adjunct used for determining the biopsy site, which facilitates early detection of dysplastic changes in PMD. Some authors suggested that double staining method has superior results over staining with a single dye. The aim of the study was to evaluate the accuracy of in vivo staining with methylene blue (MB) and Lugol's iodine (LI) double staining method in comparison with MB staining alone. Fifty patients of oral leukoplakia were recruited for the study. After obtaining written informed consent from the patients, the lesions were stained consecutively with 5% MB and 3% LI. The pattern of dye retention of MB alone, followed by MB and LI was noted. Incisional biopsy from the lesion was taken based on the retention of MB and the absence of staining of LI or by clinical judgement in case both stains were not retained. The clinical uptake of the stains was correlated with the degree of dysplasia on histopathological examination. Out of 50 subjects, MB was retained in 47 cases (94%), while 3 cases (6%) failed to retain the dye. However, out of 47 cases, 20 cases had dark blue stain and were considered as MB positive, while the rest 27 cases had pale blue stain and were considered to be negative for MB staining. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and diagnostic accuracy (DA) of MB staining were 57.82%, 100%, 100%, 26.53% and 46%, respectively. After applying both stains, i.e., double staining method, the outline of the lesion was better defined. Out of 50 PMD cases, 3 patients retained only LI and showed no dysplasia. Out of 47 cases which showed dysplasia, 27 cases showed pale blue retention of MB (-) and also were negative for LI. The rest 20 cases were positive for MB but negative for LI. The sensitivity, specificity, PPV and NPV with double staining technique were 100%. The accuracy and reliability of double staining method was superior to MB staining. Increased accuracy of double staining method aids in better detection of dysplasia and is of great help to the clinician in deciding the nature of PMD in question.

A low cost flexible photocatalyst based on silver decorated Cu2O nanowires

In this study a low cost photocatalyst design was introduced based on the silver nanoparticle decorated Cu2O nanowires that were grown on flexible copper substrate. Photocatalyst was characterized by using scanning electron microscope, energy dispersive X-ray scattering (EDS), UV–vis diffuse reflectance spectroscopy and X-ray diffractometer. Band gap energy values for Cu2O and Ag decorated Cu2O were determined as 2.37 eV and 2.17 eV respectively. Photocatalytic activity was tested against methylene blue (MB) degradation at three different pH values. Although no noticeable difference was observed, pH 5.3 was faster. Decreasing methylene blue concentration was followed up by UV–vis spectroscopy. Visible light adsorption increased by decorating the Cu2O nanowires with silver nanoparticles. Kinetics of degradation was found to be first order with a R-squared value of 0.99. Nearly total MB was degraded at 300 min. Degradation was verified by high pressure liquid chromatography. Absence of initial MB retention peaks showed a successfully degradation under 100 W LED light illumination. Flexible copper support under the nanowire arrays presents an advantage of easy removal for the photocatalyst. After the end of the reaction, no photocatalyst residue is left when compared to the powder photocatalyst systems eliminating the heavy filtration processes.

Adsorption-Desorption Profile of Methylene Blue Dye on Raw and Acid Activated Kaolinite

The efficiencies of raw (RK) and acid activated (0.5 M AAK) kaolinite clay minerals to remove methylene blue (MB) dyes in aqueous solution were investigated and compared. The 0.5 M AAK was prepared by treatment of RK in dilute 0.5 M HCl aqueous solution under reflux. Kaolinite adsorbents were characterized and their MB removal performances were evaluated via the batch method. MB desorption from spent kaolinites was investigated at pH 4 to 8. The MB removal was increased with increasing initial dye concentration, agitation speed and adsorbent dosage in 60 min reaction time at pH 6. Both kaolinites showed high MB removal (up to 97%). The Freundlich model has the best-fit equilibrium adsorption isotherm model for RK and 0.5 M AAK. The kinetic data for both adsorbents showed strong agreement with the pseudo second order kinetic model (r2 &gt; 0.98). Nevertheless, the spent RK adsorbent demonstrated a significant higher MB retention than 0.5 M AAK in desorption experiments. Kaolinite clays have great potential as cost-effective materials for dyes removal in wastewater treatment.

The Reuse of Palm Tree Fiber Waste As a Solid Phase Extractor for the Removal of Methylene Blue Dye from Wastewater

Introduction – Quite often large amounts of colored wastewater are discharged into natural streams with undesirable consequences to the environment and to human health, being generated by industries that use dyes to impart a desired color to their products (food, paper, rubber, textile, plastics and others) [1]. The dye-contained effluents are supposed to be a significant concern due to the adverse effects of dye in various parts of the life cycle. The toxicological and aesthetical problems associated with release of dyes into the environment are the main reasons of these worries. Methylene blue (MB) is one of the widespread materials in dye which is used for cotton and silk painting. The most harmful effects of MB is eye burn and also create breathing problems, nausea, vomiting, profuse sweating, mental confusion and methemoglobinemia. Many treatment methods have been used to remove the dyes from industrial wastewater, which can be divided into physical, chemical, and biological methods. Among the various methods, adsorption is an effective separation process for a wide variety of applications [2]. It is now recognized as an effective and economical method for the removal of both organic and inorganic pollutants from wastewaters. Palm Tree Fiber (PTF), a residue from date farms and industry was studied as a biosorbent for the removal of Methylene blue dye (MB) from contaminated water. Experimental Adsorbent preparation and Characterization : the Palm Tree Fiber was washed, dried, grounded then sieved to different particle size and stored into plastic bag. PTF was characterized by Field Emission Scanning Microscopy/Energy Dispersive X-ray (FESEM- JEOL JSM 6360LA, Japan). The FESEM analysis was carried out at room temperature with accelerating voltage of 20 kV. Batch experiment: Study effect of different environmental factor such as, adsorbent mass, contact time, pH and temperature. All determinations were performed in a total of three replicates per experiment and the average values were reported using Ultraviolet (UV-C) with two 15-watt lamps (Philips Model) was used as a source of ultraviolet radiation at λmax = 664 nm. kinetic and isotherm models were utilized to describe the adsorption process mechanisms [3]. Environmental application and recycling. Results and Discussion - Palm Tree Fiber (PTF) residue of date farms and industry was successfully used as biosorbent for Methylene blue (MB) dye from contaminated water. The chemical composition and surface morphology of the biosorbent was critically studies figure (1). In batch separation mode, the effect of various analytical parameters (adsorbent dose, ion strength, contact time, pH, and temperature) on MB uptake by the used bio sorbent was studied. The kinetic data were also subjected to pseudo-first order and pseudo- second order mathematical models. The pseudo-second order was more predominant for MB uptake. The adsorption equilibrium data of MB retention were subjected to Langmuir to assign the most probable retention mechanism. Langmuir isotherm model indicated an adsorption in monolayers [4]. The application study showed that 99% of MB was removed from the environmental water samples, and a good removal percentage on the 2-time recycling was achieved. Conclusions - The maximum percentage removal of MB was about 99 %, at the dosage of 20 mg. Adsorption isotherms, and kinetic models were carried out for the calculation of adsorption parameters. The data a demonstrated that the Langmuir isotherm provides a better fit due to higher R2 values. The adsorption process followed a pseudo second order kinetic model indicates that the rate controlling step may be electrostatic attraction. The regenerated biomass exhibited increased dye adsorption up to two subsequent cycles. The results presented in this study indicate that PTF presents great potential as an inexpensive and easily available alternative adsorbent for the removal of cationic dyes in wastewater treatments. For a future research, modification of PTF surface to increase the efficiency of adsorption capacity. Keywords: Adsorption kinetics; Agri-food waste; Biosorption; Methylene Blue dye; Water treatment.

Improvement of cutaneous delivery of methylene blue by liquid crystals

The purpose of this study was to evaluate the effect of composition and characteristics of liquid crystalline phases (LCPs) on cutaneous delivery of methylene blue (MB). LCPs were obtained by mixing Brij97® with water at various ratios; Brij97®:water at 8:2 (F8:2), 7:3 (F7:3), and 6:4 (F6:4) were selected, and MB was incorporated at 0.1%. F8:2 and F7:3 exhibited textures and small angle X-ray scattering (SAXS) patterns corresponding to lamellar phase, whereas F6:4 displayed characteristics of hexagonal phase. All three LCPs were stable for 9 months, and exhibited thixotropic pseudoplastic behaviour. Increasing water content increased viscosity. All three LCPs released less (3.2- to 6.6-fold) MB than control gel (3.0% hydroxyethylcellulose (HEC) + 0.1% MB), demonstrating their ability to sustain release. Despite the lower release, all LCPs improved skin retention of MB at 6 h post-application (1.3- to 2.1-fold) compared to the control gel. Among the LCPs, F8:2-mediated skin retention of MB was more pronounced, followed by F7:3. Consistent with the increased penetration, transepidermal water loss (TEWL) also increased after treatment with the LCPs (2.0–2.8 fold), which suggests their influence on skin barrier. Irritation studies by Hen’s Egg Test – Chorioallantoic Membrane (HET-CAM) suggest that F7:3 and F6:4 may be better tolerated by the skin than F8:2.

Superlight Adsorbent Sponges Based on Graphene Oxide Cross-Linked with Poly(vinyl alcohol) for Continuous Flow Adsorption.

In this study, superlight adsorbent sponges (bulk density 0.016-0.049 g·cm-3) were developed based on graphene oxide (GO) cross-linked with poly(vinyl alcohol) (PVA). The interlayer spacing of the GO nanosheets was increased by the insertion of PVA, and good mechanical integrity was attained by the cross-linked structure. They showed excellent continuous flow adsorption capacity (CFAC) when methylene blue (MB) was used as a model contaminant; a water flux of 396 L·m-2·h-1 through a 2 cm thick adsorbent sponge was achieved at a hydraulic head of only 10 cm water, with an almost complete retention of MB. They corresponded to a water permeability of 4.0 × 105 L·m-2·h-1·MPa-1, which was several orders of magnitudes higher than GO-based membranes for similar applications reported in the literature. The GO nanosheets were completely immobilized in the sponge by cross-linking with PVA, and thus, there was no GO nanoparticle leaching or flushing out into the treated permeate water, which was another advantage over direct use of GO powders in water treatment. Because of the high water permeability and CFAC, the cross-linked GO/PVA sponges have a great potential for wastewater treatment.

Characterization of Polysulfone Membranes Prepared with Thermally Induced Phase Separation Technique

Membrane technology is one of the most used water treatment technology because of its high removal efficiency and cost effectiveness. Preparation techniques for polymer membranes show an important aspect of membrane properties. Generally, polysulfone (PSf) and polyethersulfone (PES) are used for the preparation of ultrafiltration (UF) membranes. Polysulfone (PSf) membranes have been widely used for separation and purification of different solutions because of their excellent chemical and thermal stability. Polymeric membranes were obtained by phase inversion method. The polymer solution introduced in the nonsolvent bath (distilled water) initiate the evaporation of the solvent from the solution, this phenomenon has a strong influence on the transport properties. The effect of the coagulation bath temperature on the membrane properties is of interest for this study. Membranes are characterized by pure water flux, permeability, porosity and retention of methylene blue. The low temperature of coagulation bath improve the membrane’s rejection and its influence was most notable.

The Use of Modified Beetroot Fibers by Sodium Dodecyl Sulfate (SDS) Cleaning Water Contaminated by Organic and Inorganic Compounds

&lt;p&gt;The beetroot fibers were used to decontaminate water polluted by methylene blue dye (MB), to remove heavy metals from wastewater and to soften hard water. In order to improve the adsorbent performance and to determine the optimum conditions of industrial wastewater cleaning, the effect of fiber particle sizes, initial concentrations of pollutants, pH of aqueous solutions and effluent rates on the cleaning procedure were investigated. Data showed that the efficiency of cleaning increased when fiber particle size decreased (from mm to µm scale). Optimum pH value for adsorption was 6 to 6.5. Maximum metal cations retention or hardness of modified fibers by sodium dodecyl sulfate (SDS) was estimated at 70 mg per gram of fiber; while the maximum retention of methylene blue was found to be 300 mg of dye per gram of fiber. Chemical modification of fibers by an anionic surfactant such as sodium dodecyl sulfate increased the efficiency of the dye elimination by 2-fold when compared to unmodified fibers. The adsorption parameters were determined using Langmuir and Freundlich isotherms.&lt;strong&gt;&lt;/strong&gt;&lt;/p&gt;

Application of external electric field to enhance the permeate flux during micellar enhanced ultrafiltration

Removal of dye from aqueous solution using electric field assisted micellar enhanced ultrafiltration (MEUF) has been studied in a rectangular cross-flow channel over a wide range of operating conditions. Sodium dodecyl sulfate (SDS) and methylene blue (MB) have been taken as anionic surfactant and cationic dye, respectively. An ultrafiltration membrane (polyphenylene ethersulfone) of molecular weight cut-off (MWCO) 10 kDa, has been used in the experiment. The effects of operating conditions, e.g., electric field, surfactant to dye concentration ratio, transmembrane pressure and cross-flow velocity on the permeate flux and retention of MB have been investigated in detail. Experimental results confirm that by applying d.c. electric field (1000 V m −1), permeate flux increases by about 33% with approximately 99% removal of MB. An expression for the prediction of limiting flux in ultrafiltration is developed in this study. The predictions of permeate flux are in good agreement with the experimental results.

Removal of methylene blue from waste water using micellar enhanced ultrafiltration

Ultrafiltration of micellar solutions containing sodium dodecylsulfate (SDS) and oxyethylated coconut fatty acid methyl esters (OMC-10) and their binary mixtures were studied and used to recover methylene blue. This was achieved through solubilization in mixed negatively charged micelles. Under the experimental conditions used, no significant fouling of the membrane comprising of cellulose, polyethersulfone and polyvinylidene fluoride was observed, with no retardation of ultrafiltration. The introduction of a nonionic surfactant to SDS reduced the critical micelle concentration of mixed micelles and then the concentration of surfactants in the permeate, i.e., from 8.3×10 −3 M for SDS to 2.0×10 −3 M for the mixture of SDS:OMC-10=4:1. Such a tailored surfactant mixture enabled the authors to achieve 93–94% retention of methylene blue using a hydrophilic membrane made of cellulose. Ultrafiltration of micellar solutions could also be considered a research method, helpful in determining important parameters such as micelle loading and the micelle binding constant used to characterize micellar solutions. Additionally the distribution coefficient employed in extraction studies can be resolved.

Removal of methylene blue from aqueous solution by fibrous clay minerals

Kinetics and equilibrium processes of the methylene blue (MB) retention from aqueous solution by a mixture of fibrous clay minerals, which was isolated from a naturally occurring clay, were investigated. For these purposes, the effects of contact time, initial adsorbate concentration, adsorbent content, pH and ionic strength were determined. The results show that the MB retention obeys a pseudo-first order equation and the process is a diffusion controlled solid-state reaction. Moreover, the isotherm data fitted the Langmuir equation and the MB binding process became more energetic with the increase of the adsorbent concentration. In addition, the augmentation of the clay content or the initial MB concentration reduced the adsorption capacity, presumably because of the clay particles microaggregation and/or the occurrence of MB deriving species. On the other hand, it is observed that the MB uptake limit is reduced in low acid pH, particularly below the PZC, as well as in ionic strengthen solutions. These facts are linked to the silanol group protonation and to the reduction of the electrostatic forces induced by the clay particles, respectively.

Reduction and uptake of methylene blue from rat air spaces

The use of methylene blue (MB) to estimate dilution of epithelial lining fluid, which occurs during bronchoalveolar lavage (BAL), is complicated by loss of this redox dye from the air spaces. The rate of MB uptake from the air spaces of isolated rat lungs and the effects of oxidation and reduction on this process were investigated in this study. Movement of MB from the air spaces to perfusate was compared with the corresponding transport of 125I-labeled albumin, [14C]-dextran, 99mTc-labeled diethylenetriaminepentaacetate, [3H]-sucrose, and 3H2O. By the end of 2 min, MB concentrations in the BAL had fallen by 58 +/- 4% (SE; n = 11) and 3H2O by 78 +/- 2% (n = 13), whereas concentrations of the other indicators decreased by approximately 6%. All but 10% of the 3H2O lost from the air spaces was found in the perfusate, whereas 19% of the lost MB was not recovered in the perfusate, suggesting retention of MB in the pulmonary tissues. Absorption of MB from the air spaces was slowed by 20% when the lungs were left unperfused, and absorption was accelerated threefold by reduction of MB to leukomethylene blue with Na2S2O4. In contrast, MB losses from the air space were slowed by the oxidizing agent K3Fe(CN)6 and by addition of superoxide dismutase or ascorbic oxidase. It is therefore possible that ascorbic acid and O2- entering the air spaces reduce MB to the uncharged leuko form. Lowering the pH of the BAL fluid to 3.5 also slowed MB reabsorption. This suggests that acid aspiration may stimulate release of oxidants into the air spaces.