Indigo Carmine degradation by hypochlorite in aqueous medium monitored by electrospray ionization mass spectrometry

The degradation of the dye Indigo Carmine by hypochlorite in aqueous solution was monitored by electrospray ionization mass spectrometry in the negative ion mode (ESI(—)‐MS). Hypochlorite was highly efficient in removing the color of aqueous solutions of the dye. ESI(—)‐MS monitoring showed that concomitant with the Indigo Carmine consumption two transient species appeared (detected as doubly charged anions) probably formed via a net insertion of two hydroxyl groups at the exocyclic C?C bond followed by the incorporation of two (mainly) or one oxygen atoms at the indolic rings of the dye. Structures of these products were proposed based on the ESI(—)‐MS/MS data and high accuracy mass measurements. These two transient intermediates quickly decomposed, both in the condensed and in the gas phase, to yield mono‐charged anions. Based on these results, a route for the Indigo Carmine degradation by hypochlorite in aqueous solution has been proposed. Copyright © 2007 John Wiley & Sons, Ltd.     

The removal of humic acids from water by solvent sublation

The application of solvent sublation in the removal of humic acids was investigated in the present study. The humic acids (HA) were removed from an aqueous solution by solvent sublation of humic acid-hexadecylpyridium chloride (HPC) complex (sublate) into isopentanol. Several parameters were examined towards the optimization of humic acid removal; the dosage of a surfactant was found to be the major one, controlling the overall efficiency of the progress. The removal rate was somewhat enhanced by higher airflow rate and almost independent of the volume of the organic solvent floating on the top of the aqueous column. The effects of electrolytes (e.g., NaCl), nonhydrophobic organics (e.g., ethanol), and pH of the solution upon the process were studied. Under the optimized condition, the treatment performance was found to be very efficient, reaching almost 100%, indicating that solvent sublation can serve as a possible alternative technology for the removal of humic acids. The solvent sublation process follows first-order kinetics. A characteristic parameter, apparent activation energy of attachment of the sublate to bubbles, was estimated at a value of 9.48 kJ/mol. Furthermore, the simulation of a mathematical model with the experiments on the solvent sublation of humic acid-HPC was described here.     

Effect of Temperature on the Binding and Distribution Characteristics of Thionine in Sodium Dodecylsulfate Micelles

The interaction between thionine (a cationic thiazine dye) and anionic surfactant sodium dodecylsulfate in aqueous solution at different temperatures has been studied spectrophotometrically. The absorption spectra were used to quantify the dye/surfactant binding constants and surfactant/water partition coefficients of the dye by applying mathematical models that consider partitioning of the dye between the micellar and aqueous pseudo-phases. The Benesi-Hildebrand equation was applied to calculate the binding constants of thionine to sodium dodecylsulfate micelles over a temperature range of 293 to 333 K. To evaluate the thermodynamic aspects of the interaction of thionine with sodium dodecylsulfate micelles, Gibbs energy, enthalpy and entropy changes were determined. The effect of temperature on the critical micelle concentration of sodium dodecylsulfate in the presence of thionine was also studied and discussed. The binding affinity of thionine to the sodium dodecylsulfate micelles significantly decreased with increasing temperature because of the thermal agitation.     

溶剂气浮法分离水中的Zn离子的研究

以双硫腙为配体,溴化十六烷基三甲基铵（CTAB）为表面活性剂。对Zn离子在无机相中形成的Zn-双硫腙-CTAB体系的溶剂气浮进行了研究。研究表明表面活性剂与Zn离子的物质的量之比为5：1,约1h水中的锌离子去除率可达98％。0．5mol／L NaCl大大提高体系的溶剂气浮的去除率,溶剂气浮的速率随着气流速率的增加而增加,共存溶质乙醇存在会使去除率降低,有机溶剂的量对溶剂气浮影响较小,溶剂气浮过程遵从假一级动力学。考察了不同温度下溶剂气浮的回收速率,计算了该过程中的气浮表观活化能为9．037kJ／mol。     

Ion flotation of nickel using ethylhexadecyldimethylammonium bromide

Nickel ions react with the surfactant ethylhexadecyldimethylammonium bromide (EHDABr) to foam a surface-active sublate which can be removed from aqueous chloride solutions by ion flotation. A typical ion-flotation procedure involves passing a fixed volume of air through a 250-ml solution containing 4.0 ppm nickel and 0.05 M KCl at a pH of 5 at a rate of 60 ml/min for 60 min. The method is simple and rapid with 87% removal of the nickel.     

Pharmaceutical quality control of acid and neutral drugs based on competitive self-assembly in amphiphilic systems

An aggregation parameter-based methodology for determining acid and neutral drugs in pharmaceutical dosage forms is presented. The method is based on competitive self-assembly in ternary dye-surfactant-drug aqueous mixtures. Dyes bearing charge of opposite sign to that of surfactants bind to surfactant to form mixed dye-surfactant aggregates, which are monitored from changes in the spectra features of the dye. The drug competes with the dye to interact with the surfactant to form drug-surfactant aggregates, which results in a decrease in the surfactant to dye binding degree proportional to the drug concentration in the aqueous solution. Coomassie Brilliant Blue G (CBBG) and didodecyldimethylammonium bromide (DDABr) were the dye and surfactant reactant used, respectively. The suitability of the surfactant to dye binding degree (SDBD) method to determine drugs with very different molecular structure: propionic (flurbiprofen, ibuprofen, naproxen and ketoprofen) and acetic (diclofenac, felbinac and zomepirac) acids, indolines (indomethacin and sulindac), glycyrrhetinic acid derivatives (carbenoxolone and enoxolone), salicylates (diflunisal and phenyl salicylate), oxicams (meloxicam, piroxicam and tenoxicam), pyrazolones (phenylbutazone and sulfinpyrazone) and hydrocortisones (dexamethasone and prednisolone) has been proved. The proposed method was successfully applied to the determination of drugs in commercial formulates (effervescent granulates, tablets, suppositories, gels and blisters) with a minimum sample treatment (dilution of liquid samples and dissolution of solid samples).     

Ion flotation of zinc using ethylhexadecyldimethylammonium bromide

Zinc ions react with the surfactant ethylhexadecyldimethylammonium bromide (EHDABr) to form a surface active sublate which can be removed from aqueous chloride solutions by ion flotation. A typical ion flotation procedure involves passing air through a 235-ml solution containing 5 ppm Zn²⁺, 2.0 M HCl, and 2.5 × 10^?3M EHDABr at a flow rate of 40 ml/min for 150 min. The procedure is simple and rapid. Cadmium, copper, lead, and nickel ions cause reductions of zinc flotation efficiencies of less than 2.5% under the experimental conditions.     

Dye aggregation and influence of pre-micelles on heterogeneous catalysis: A photophysical approach

Common cationic dyes used for laser and fluorescent probes present low solubility in water. In order to increase the dye concentration in aqueous solutions, anionic surfactant can be added. The strong interaction between anionic surfactant and cationic dye can affect drastically the dye absorption and fluorescence properties. Here we observed that the fluorescence of the species in aqueous solution is maximized at condition of complete micellization of surfactants at critical micelle concentration (CMC). In addition, combined measurements of absorption, emission and fluorescence lifetime provide fundamental information on the critical concentration of H-aggregates formation and monomer separation, induced by pre-micelles and homomicelles on different surfactant sodium dodecylsulphate (SDS) concentration. The experimental results show how to find precisely the critical concentration of H-aggregates by optical method in two different xanthene-derived molecules: rhodamine 6G and rhodamine B. The adequate transference of electron from excited dye to the conduction band of semiconductor (TiO₂) promotes the creation of reactive species that provides the degradation of dye with advantage of use of irradiation in the visible region and strong photobleaching with direct exposure to the visible light irradiation in a scale of time of 10 min.     

Spectroscopic investigations on the binding of ammonium salt of 8-anilino-1-naphthalene sulfonic acid with non-ionic surfactant micelles in aqueous media

The anionic dye 8-anilino-1-napthalensulfonic acid ammonium salt, or ANS, was used as a fluorescent probe to investigate the behaviour of dye-surfactant interactions in aqueous solutions of Triton X-100 and the Brij and polyoxyethylene tridecyl ether (POE TDE) series of polyoxyethylene non-ionic surfactants. The fluorescence behaviour of the dye with the non-ionic surfactants was examined in micellar media. The concentration of surfactant was kept well above the cmc to investigate the interaction of the dye with surfactant micelles. In this investigation, the relative fluorescence enhancements, binding constants of the dye to the surfactant micelles and aggregation numbers of the micelles were determined, from the analysis of spectroscopic data.     

辛基三甲基溴化铵与辛基硫酸钠混合水溶液的相行为

对辛基三甲基溴化铵(OTAB)与辛基硫酸钠(SOS)正、负离子混合表面活性剂水溶液的相行为进行了研究.在高浓度的溶液中,混合表面活性剂形成液晶相,随着混合摩尔比OTAB/SOS接近于1,液晶结构由六角相转层状相,同时夹杂少量沉淀物;在中等浓度时,任意混合摩尔比例下皆为均相透明溶液;在低浓度下,在很宽的OTAB/SOS混合摩尔比的范围,出现双水相,其中的表面活性剂稀薄相,为不同大小的胶团与囊泡组成的稀溶液,另一表面活性剂富集相中则为数密度很大的囊泡聚集体,富集相对油溶性染料的增溶作用比非富集相高得多.     

NaBr对杂双子表面活性剂C_mOhpNC_8水溶液吸附和聚集的影响

以表面张力和荧光探针技术研究了NaBr对杂双子表面活性剂CmOhpNC8(m:10,14,16)水溶液性质的影响。结果表明,NaBr强烈促进了CmOhpNC8在气/液界面上的吸附和在水相中的聚集,其中c20在cNaBr≥10mmol/L时降到极低的微摩尔/升数量级,显示了相当高的降低水表面张力效率。在NaBr促进下,水溶液中CmOhpNC8表现出强烈的预胶团化行为。这些均是对应的2种单头基单烷烃链表面活性剂简单1:1混合所无法实现的,显示了在头基处引入短联接链形成杂双子结构的表面活性优势以及对盐效应的敏感性。     

Superabsorbent amphoteric nanohydrogels: Synthesis,characterization and dyes adsorption studies

The goal of the present research is to remove high percentage of cationic and anionic dyes such as,Neutral Red, Safranin O and Indigo Carmine from aqueous solutions by poly(NIPAAm/N,Ndiallylpyrrolidinium bromide/AA) superabsorbent amphoteric nanohydrogels synthesized using the inverse microemulsion polymerization method. Effect of various parameters such as, treatment time,initial dye concentration, p H and adsorbent dose were investigated. Furthermore, kinetics and isotherms adsorption models were applied to determine the maximum adsorption and mechanism for adsorption,which shows that adsorption obeyed the pseudo-second order kinetics. From the results, removal of dyes within the nanohydrogel was found to be in the order: AB-74 BR-2 BR-5.     

Kinetic and redox characteristics of semireduced species derived from phenosafranine in homogeneous aqueous and sodium dodecyl sulfate micellar media

One‐electron reduction of phenosafranine (PS⁺ 3,7‐diamino‐5‐phenylphenazinium chloride), a phenazinium dye, has been studied in homogeneous aqueous and sodium dodecyl sulfate (SDS) micellar media, using the pulse radiolysis technique. The various reducing radicals employed for the study in homogeneous aqueous medium were e_aq^?, H^˙, CO_2,^˙?, and isopropyl ketyl radicals (CH₃)₂ ^˙COH. Semireduced species generated by these reactions have been characterized by their absorption spectra, decay kinetics, and pK_a. The one‐electron reduction potential of PS⁺ was determined at pH 7 in homogeneous aqueous solution employing nitrobenzene (NB/NB^˙?) as the standard couple. One‐electron reduction in SDS micellar medium and a detailed spectrophotometric investigation of the parent dye in this surfactant system was carried out in order to understand the dye–surfactant interactions in the micellar and premicellar media.© 2001 John Wiley & Sons, Inc. Int J Chem Kinet 34: 56–66, 2002     

A spectral approach to determine location and orientation of azo dyes within surfactant aggregates

The UV–vis absorption properties of azo dyes are known to exhibit a variation with the polarity and acidity of the dye environment. The spectral properties of a series of anionic azo dyes were characterized to further probe the interaction of these dyes with two types of surfactant aggregates: (1) the spherical micelles formed in aqueous solution by alkyltrimethylammonium bromide (C_nTAB) surfactants with n = 10–16 and (2) the unilamellar vesicles spontaneously formed in water from binary mixtures of the oppositely-charged double-tailed surfactants cationic didodecyldimethylammonium bromide (DDAB) and anionic sodium dioctylsulfosuccinate (Aerosol OT or AOT). The observed dye spectra reflect the solvatochromic behavior of the dyes and suggest the location and orientation of the dye within the surfactant aggregates. Deconvolution of the overall spectra into sums of Gaussian curves more readily displays any contributions of tautomeric forms of the azo dyes resulting from intramolecular hydrogen bonding. The rich variation in UV/vis absorption properties of these anionic azo dyes supports their use as sensitive tools to explore the nanostructures of surfactant aggregates.     

Dye-labeled polystyrene latex microspheres prepared via a combined swelling-diffusion technique

A series of water-insoluble, biologically compatible dyes, meso-tetraphenylchlorin, meso-tetraphenylporphyrin and chlorophyll-a, were successfully incorporated into beads composed of linear polystyrene (PS) via a tunable combined swelling-diffusion process. Dyed PS beads were prepared by the addition of a dye solution in tetrahydrofuran to an aqueous suspension of 10 μm PS beads in the presence of a poly((ethylene glycol)-b-(propylene glycol)-b-(ethylene glycol)) block copolymer surfactant. The presence of surfactant was found to be beneficial to prevent particle aggregation, especially at tetrahydrofuran contents above 30%. Dye loading was shown to be tunable by simple adjustments in dye composition. Confocal fluorescence microscopy indicated that dyes were distributed uniformly throughout the entire PS bead, but heterogeneously with ~500 nm diameter droplets, indicative of a separate dye phase within the PS matrix. The stability of dyed beads, indicated by resistance to dye leaching in solvent, was found to be governed by the degree of swelling of PS in the solvent medium. Hence, no leaching was observed even when a good solvent for the dye was used (ethanol), as long as that solvent did not swell the carrier particle, PS. No leaching of dyes from the beads was observed during long-term (2 years) storage in water.     

Immobilization of Bromocresol Purple in Inorganic-Organic Sol-Gel Thin Film with Presence of Anionic and Non-ionic Surfactants

Sol-gel materials known as organically modified silicates (ORMOSILs) offer interesting features such as chemical and mechanical stability. In this paper VTES (vinyltriethoxysilane) and TEOS (tetraalkoxysilane) are mixed in 3:1 ratio. Sol-gel solution was prepared by hydrolysis process of precursors by using ethanol as solvent. After a while a pH-sensitive indicator bromocresol purple (BCP) and surfactant were incorporate into the sol-gel mixture. The percentage of sodium dodecyl sulfate (SDS) and polyethylene glycol (PEG) which act as surfactant were varied to observe the effect of improving host material's nanostructure as well as the interaction between BCP and sol-gel matrices. The absorption peak of the BCP dye changed significantly in the presence of surfactant compared to pure VTES: TEOS mixture (control) in the range of 400 to 450 nm. The presence of BCP dye in the sol-gel mixture can be determined via FTIR spectrum with a =C–H stretch in aromatics observed at 3100-3000 cm^-1 which represented the aromatic of the BCP structure. The addition of BCP and surfactant had influenced the FTIR spectra of VTES: TEOS sol-gel materials. Addition of an anionic surfactant to the sol-gel mixtures was found to increase the BCP dye and the sol-gel matrices interaction, thus reducing the dye's tendency to leach. This work shows that sol-gel derived matrices yield dyes with sufficient rigid environment and addition of the surfactant helps to improve the interaction of filler matrices. The anionic SDS shows better leaching resistant compared to non-ionic PEG surfactant. Results of this study offer an attractive possibility to optimize the doped sol gel matrices to be used as sensing material in aqueous condition.     

Color Characteristics of Aqueous Solutions of Synthetic Food Dyes

The color characteristics of aqueous solutions of synthetic food dyes Azo Rubine, tartrazine, Indigo Carmine, Ponceau 4R, Sunset Yellow, and Brilliant Blue were studied. A formula is proposed for determining the hue of dye solutions.     

Synthesis and application of treated activated carbon for cationic dye removal from modelled aqueous solution

Use of activated carbon (AC) prepared from rice husk and treated with anionic surfactant is investigated to eliminate cationic dye crystal violet (CV) using modelled dye solution. AC modified with anionic surfactant sodium lauryl sulfate (ACSLS) and other two surfactant namely sodium dodecyl sulfonate and hexadecyl trimethyl ammonium bromide were used for the analysis. Optimum ACSLS was analyzed and characterized using BET, XRD, SEM accompanied with XEDS, FTIR, HR-TEM and zeta potential, which confirms the sorption of CV onto ACSLS. Influence of pH, dose of adsorbent, concentration of initial dye, contact time, additive salts as well as actual water samples were investigated. Presence of NH⁴⁺, Ca²⁺, Mg²⁺, Na²⁺, Ca²⁺ and K⁺ cations in dye solution were having negligible (less than 4 %) influence on dye removal capacity. Study of mass transfer parameters revealed intra particle diffusion and film diffusion both played their part, whereas other kinetic studies has shown that experimental data fitted best with Pseudo 2nd order rate. Isotherm studies accompanied with error analysis revealed that Langmuir isotherm controls the adsorption equilibrium with highest capacity of CV adsorption with optimum operating conditions as pH = 6, temperature = 318 K, adsorbent dose = 100 mg/L and dye concentration = 30–60 mg/L. Study of thermodynamics and temperature analysis have shown that the sorption reaction was favourable and spontaneous with rise in temperature and endothermic in nature. Column studies are reported for varying rate of flow, depth of bed and dye concentrations along with analysis of column experimental data with various models like Yoon-Nelson, Thomas, Bohart-Adam and Clark model. Reusability (no. of cycles) of used adsorbent was studied using regeneration experiments. Analysis inferred that AC modified using surfactants can be a useful technique for enhanced adsorption capacity of dyes from aqueous solution and not much work has been reported on use of anionic surfactant modified AC for dye removal process.     

Effect of surfactant on porosity and swelling behaviors of guar gum-g-poly(sodium acrylate-co-styrene)/attapulgite superabsorbent hydrogels

Novel fast-swelling porous guar gum-g-poly(sodium acrylate-co-styrene)/attapulgite (GG-g-P(NaA-co-St)/APT) superabsorbent hydrogels were prepared by simultaneous free-radical graft copolymerization reaction of guar gum (GG), partially neutralized AA (NaA), styrene (St) and attapulgite (APT) using N,N'-methylenebisacrylamide (MBA) as a crosslinker and ammonium persulfate (APS) as an initiator in aqueous solution and the surfactant self-assembling templating pore-forming technique. Fourier transform infrared (FTIR) spectroscopy confirmed that the surfactant could be removed from the final hydrogel product by methanol/water (8:1, v/v) washing process and the surfactant only act as micelle template to form pores. The effect of surfactant type on the porous microstructure of the hydrogel was assessed by field emission scanning electron microscope (FESEM). It was shown that incorporation of proper amount of anionic surfactant sodium n-dodecyl sulfate (SDS) in the gelling process of the hydrogel can obviously enhance the swelling capacity and initial swelling rate. The salt-sensitivity of the SDS-added hydrogel in distilled water and 15 mmol/L NaCl, CaCl(2) solution or 15 mmol/L NaCl and CaCl(2) solution was investigated, and it was found that the swelling-deswelling capability is quite reversible. A similar reproducible on-off switching behavior was observed in the 1 mmol/L solution of phosphate buffer at pH 2.1 and 7.4.