Surfactant-intercalated smectite modified electrode: sensitive electrochemical detection of methyl orange dye

This work describes the use of organosmectite modified electrode to evaluate the electrochemical behaviour and to develop an electroanalytical procedure for the determination of methyl orange (MO) dye in natural water. Organosmectites were prepared by intercalation of hexadecyltrimethylammonium cations at various ratios into the interlayer of smectite. The synthesised organosmectites were characterised by various physicochemical techniques such as Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy and transmission electron microscopy. An amperometric sensor based on organosmectite as electrode modifier for MO sensing purposes was then evaluated by means of clay-film modified electrode using square wave voltammetry (SWV). The electrochemical procedure for MO analysis by stripping voltammetry involves two successive steps: accumulation of MO at open circuit conditions followed by a voltammetric detection in a same medium by the SWV technique. The peak current obtained (after 5 min preconcentration of 15 µmol L^?1 MO solution) on a glassy carbon electrode coated by a thin film of the modified clay was more than 2.5 times higher than that exhibited by the same substrate covered by a film of the pristine clay. Under optimised conditions, a linear calibration curve for MO was obtained in the concentration range from 0.1 to 1.6 µmol L^?1, leading to a detection limit of 4 × 10^?8 mol L^?1 (signal-to-noise ratio equal to 3). The interfering effect of various inorganic and organic ions likely to influence the stripping determination of the MO was also examined. To further validate application of this sensor, the proposed method was successfully used to the determination of MO in natural water with satisfactory results.     

Adsorption of anionic methyl orange dye by polyaniline,poly(o-methylaniline) and poly(o-methoxyaniline)

This study reports the effect of substituents in the ortho position of polyaniline on the adsorption capacity to remove the anionic dye methyl orange (MO) from an aqueous solution. The aim of this study is the synthesis of polyaniline (PANI) and its derivatives, poly-o-methylaniline (poly-o-toluidine, POT) and poly-o-methoxyaniline (poly-o-anisidine, POA) for the adsorption removal of MO dye. All polymers were obtained by oxidative polymerization of the corresponding monomers and characterized by scanning electron microscopy (SEM) and infrared spectroscopy (IR). The average particle size of the polymer was about 200 nm. The effect of various parameters such as pH, temperature, adsorption time and initial concentration was analyzed. It was found that the adsorption capacity for dye removal increases from 50.68 to 222.56 mg g⁻¹ for PANI, from 16.89 to 66.57 mg g⁻¹ for POT, and from 97.26 to 532.54 mg g⁻¹ for POA with an increase in the initial dye concentration from 5 up to 50 mg L⁻¹. For all polymers, the equilibrium state of MO adsorption was reached in 50 min. The results showed that MO adsorption on PANI, POT, and POA is well described by a pseudo second order kinetic model. Isothermal studies have shown that adsorption is in good agreement with the Langmuir isotherm model, as evidenced by higher values of correlation coefficients. Based on the data of thermodynamic studies, it was concluded that MO adsorption on PANI, POT, and POA is spontaneous and endothermic.     

pH shifting effect on anionic dye removal by surfactant-modified sugar beet pulp: Modeling of column studies

pH shifting effect on the adsorption of anionic RBB dye was tested by using untreated and CTAB-treated SBP as adsorbent in both batch and continuous systems. Characterization of the sorbents revealed the effects of surface modification. Enhanced binding sites and more porous surface structure resulted in improved adsorption capability. Flow rate and initial RBB concentration effects were tested in packed bed column. Optimum pH value of the adsorption, which was determined as 2.0 in the batch studies with untreated SBP, shifted to 8.0 with 20 g/L CTAB treated SBP. Experimental data in column studies showed the decreasing capacity with increasing flow rate and enhanced performance with increasing inlet RBB concentration for both sorbents. Maximum capacities of the columns were found as 36.9 and 2.6 mg/g with dried SBP at pH 2.0 and 8.0, respectively, at a maximum inlet RBB concentration of 500 mg/L and a minimum flow rate of 0.8 mL/min. The highest capacity value at pH 8.0 was found as 140.0 mg/g under the same operating conditions, which reveals positive effect of the treatment on adsorptive performance. Langmuir isotherm was found to be most convenient model for the all equilibrium cases in the column. Moreover, Thomas model accurately predicted the breakthrough curves of each system. This is the first study reporting the modeling data of an anionic dye adsorption in a packed bed column by using modified SBP.     

Effective removal of anionic dyes from aqueous solutions by novel polyethylenimine-ozone oxidized hydrochar (PEI-OzHC) adsorbent

The adsorption behavior of the anionic dyes Remazol Brilliant Blue R (RBBR) and Reactive Black 5 (RB5) from aqueous solutions by polyethylenimine ozone oxidized hydrochar (PEI-OzHC) was investigated. The adsorption capacities of both dyes increased with functionalization of PEI in the hydrochar adsorbent. The results of surface characterization (FTIR, BET, TGA, elemental analysis, and SEM) showed that PEI modification greatly enhanced the adsorbent surface chemistry with a slight improvement of adsorbent textural properties. In addition, the adsorption kinetics data showed an excellent adsorption efficiency as reflected in the high removal percentages of the anionic dyes. The Isotherm results indicated that RBBR and RB5 dye adsorption occurred via monolayer adsorption, and chemisorption was the rate-controlling step. The PEI-OzHC adsorbent possesses higher maximum Langmuir adsorption capacity towards RBBR (218.3 mg/g) than RB5 (182.7 mg/g). This increase in adsorption capacity is attributed to the higher number of functional groups in RBBR that interact with the adsorbent. This study reveals the potential use of adsorbents derived from pine wood hydrochar in municipal as well as industrial wastewater treatment. Furthermore, surface chemistry modification is proven as an effective strategy to enhance the performance of biomass-derived adsorbents.     

Adsorption of anionic dye by anionic surfactant modified chitosan beads: Influence of hydrophobic tail and ionic head-group

In this paper, how chitosan hydrogel beads were modified by anionic surfactants (SDS, SDOS, SDBS, AOT, and DTM-12) and then used for the adsorption and removal of an anionic dye (congo red) from aqueous solutions were described. The effect of surfactant concentration, surfactant ionic head-group, and surfactant hydrophobic tail were investigated in detail. The result revealed the modified CS beads all had the obviously higher adsorption capacity than CS beads. Compared to the ionic head-group, the hydrophobic tail of the surfactant plays more important role in the adsorption, and a high adsorption capacity was observed for CS/AOT beads and CS/DTM-12 beads (both with two hydrophobic tails). The Sips isotherm model showed a good fit with the equilibrium experimental data, and the values of the heterogeneity factor (n) indicated heterogeneous adsorption. The adsorption kinetics analysis indicated that the pseudo-second-order rate model could better describe the adsorption process than the pseudo-first-order rate model.     

聚吖啶橙修饰电极伏安法测定黄嘌呤

报道了聚吖啶橙 (POAO)修饰电极多阶半微分伏安法测定黄嘌呤 (Xa)。在pH 5 .3的磷酸盐缓冲溶液中 ,Xa在POAO电极上于 0 .8V处产生一灵敏的氧化峰 ,峰电流与其浓度在 7.8× 1 0 - 8～ 1 .1× 1 0 - 6mol/L和 1 .1× 1 0 - 6～ 1 .0×1 0 - 5mol/L范围内呈良好的线性关系 ,检出限为 7.8× 1 0 - 9mol/L。方法可用于人尿中Xa的测定     

Highly removal of anionic dye from aqueous medium using a promising biochar derived from date palm petioles: Characterization,adsorption properties and reuse studies

The present work investigates the preparation of promising biochar derived from date palm petioles powder (DPB) via a thermal treatment. DPB was characterized through various techniques to analyze the chemical (FTIR), morphological (SEM) and point of zero charges to investigate changes incorporated through the pyrolysis process.The adsorption of methyl orange (MO) onto the biochar was investigated using batch experiments according to different parameters which influence the adsorption process such as: initial dye concentration, equilibrium time, pH, and temperature. Isothermal and reuse studies of MO adsorption onto DPB were also investigated.Results of MO removal on DPB have demonstrated that the adsorption process was initial dye concentration-dependent, and equilibrium time was occurred in 60 min. The biochar presented high stability of MO adsorption capacity in a large domain of pH. Thermodynamic analysis of this process revealed that methyl orange adsorption was exothermic and spontaneous in nature.The experimental data were analyzed by pseudo-first-order, pseudo-second-order model, and the intraparticle-diffusion for kinetics and Langmuir, Freundlich, and Temkin models for isotherms.Kinetic adsorption followed the pseudo-second-order model and the intraparticle-diffusion within pores controlled the adsorption rate. The experimental data yielded good fits with in the following isotherms order: Langmuir > Temkin > Freundlich, The maximum adsorption capacity of MO on DPB was found 461 mg.g^?1. The reusability study reveals the possibility of the reuse of DPB for three (03) cycles of adsorption–desorption, a slight decrease in the ability of methyl orange adsorption has noticed with the increase of the number of adsorption–desorption cycles : 81.03 %, 67.84 %, and 51.72 %, respectively. The found results of the present study show that the biochar derived from date palm petioles have the potential to be used as a promising adsorbent for the treatment of MO dye.     

Spectrophotometric determination of cationic and anionic surfactants with anionic dyes in the presence of nonionic surfactants,part I: A general aspect

The behavior of color development of anionic azo dyes, methyl orange and its analogues, was examined in aqueous media by changing the microenvironment of the dyes. The addition of alcohols, organic onium ions, anionic surfactants and nonionic surfactants brought about a decrease of the band at wavelengths near 480 nm and an increase of the band at wavelengths near 420 nm. Such a shift toward the shorter wavelengths in spectra was attributed to the change of the micro-environment around the dyes from a polar field to a less polar field; that is, the shift is caused by the change of the contribution of the following resonance forms, On the basis of the color change phenomena, the spectrophotometric methods for the determination of organic onium ions and anionic surfactants were proposed.     

固相反应法合成的巯基乙酸钠修饰zns的光催化性能

固相反应法;巯基乙酸钠修饰的zns;甲基橙;光催化     

Efficient removal of MB dye using litchi leaves powder adsorbent: Isotherm and kinetic studies

Removal of Methylene Blue (MB) dye using Litchi Leaves Powder (LLP) material was carried out in batch mode. Effect of the mass of the adsorbent (0.1–2.5 g/L), pH of the solution (2−12), starting concentration of MB dye (50–150 mg/L), ionic strength using NaCl (0.1–0.5 M) as an electrolyte, contact time (0–60 min) on the adsorption of MB dye was studied. To calculate pH at which LLP material surface becomes neutral point of zero charge (pH_pzc) is also determined and found to be 6.48. Removal process best fit in the pseudo-second-order kinetic model as indicated by its higher R² value (0.999). Isotherm models (Freundlich and Langmuir) were fitted to the data obtained from the experiment to understand the adsorption behaviour. Result shows that experimental data were fitted to the both isotherm models (Freundlich and Langmuir) as indicated by higher R² value for both Freundlich (0.991) and Langmuir (0.994) model, and it was determined that LLP has a maximum adsorption capacity of 119.76 mg/g.     

Application of phenolic compounds as natural dye extracted from date-pits: dyeing studies of modified acrylic fibres

This research work involves the dyeing of acrylic fabric with natural dye extracted from date pits powders using Soxhlet extraction process. The effect of dye bath pH, salt concentration, dyeing time and temperature were studied. The optimal dyeing conditions where pH 4, 0 g/L salt, 60 min, and 80 °C. The COD and the BOD5 of the residual dye bath were measured and it was shown from the registered values that the residual dye bath presents an acceptable rate of organic discharge.     

The effect of gas environment on rolling oil removal from cold-rolled steel as studied by TG

Summary This study investigates mechanisms of cold rolling oil removal from the surface of low-carbon steel. The removal process has been probed using thermogravimetric analysis techniques. A range of furnace atmospheres, from non-oxidizing through to highly oxidising, have been used to simulate the oil removal conditions in the industrial process. The activation energies of oil removal under each gas atmosphere have been determined by MTG and the Flynn-Wall-Ozawa method. The results show that a reducing atmosphere is the optimal environment for effective oil removal. Steel-oil surface interactions have also been investigated to show that the steel substrate catalyses oil removal.     

Structure and properties of poly(methyl methacrylate) particles prepared by a modified microemulsion polymerization

Nanoscale poly(methyl methacrylate) (PMMA) particles were prepared by modified microemulsion polymerization. Different from particles made by traditional microemulsion polymerization, the particles prepared by modified microemulsion polymerization were multichain systems. PMMA samples, whether prepared by the traditional procedure or the modified procedure, had glass-transition temperatures (T_g's) greater than 120 °C and were rich in syndiotactic content (55–61% rr). After the samples were dissolved in CHCl₃, there were decreases in the T_g values for the polymers prepared by the traditional procedure and those prepared by the modified process. However, a more evident T_g decrease was observed in the former than in the latter; still, for both, T_g was greater than 120 °C. Polarizing optical microscopy and wide-angle X-ray diffraction indicated that some ordered regions formed in the particles prepared by modified microemulsion polymerization. The addition of a chain-transfer agent resulted in a decrease in both the syndiotacticity and T_g through decreasing polymer molecular weight. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 733–741, 2004     

Catalytic reduction of hazardous acid orange 10 dye by BiVO4/TiO2 nanocrystalline heterojunction and influence of aeration,FeSO4, H2O2 and FeCl3 on removal efficiency: A novel and environmentally friendly process

Bismuth vanadate in combination with titanium dioxide were synthesized by hydrothermal method and its photocatalytic activity was investigated under visible light irradiation for acid orange 10 (AO10) dye removal. The 10% BiVO₄/TiO₂ showed the highest catalytic activity in comparison with 20, 30, 40 and 50% BiVO₄/TiO₂ ratios. The removal of AO10 azo dye in aqueous solutions was studied in laboratory-scale experiments using 25 removal processes and their removal efficiencieswere evaluated, separately. The results showed that the amount of de-colorization for each oxidation process is completely different. The order of the investigated processes in removing the dye after 90 min is as follows: LED < TiO₂ < BiVO₄ < 10% BT/without LED < BiVO₄/ LED < 50% BT < 40% BT < 30% BT < 20% BT < UV/H₂O₂ < 10% BT < 5a-10 %BT < 5F-10 %BT < 10a-10 %BT < 50F-10 %BT < 20a-10 %BT < 10F-10 %BT < 20F-10 %BT < 20H_-10 %BT < 40H-10 %BT < 50H_-10 %BT < 20a-20F-10 %BT < 20a-20F-50H_-10 %BT. Among the above processes, 20a-20F-50H-10 %BT had the best removal performance and can be suggested for using in real conditions. Coagulation/precipitation process was done using 5 mg/L of FeCl₃ as post-treatment reaching efficiency of 100% in the studied system.     

Simple and sensitive assay for nucleic acids by use of the resonance light-scattering technique with the anionic dye methyl blue in the presence of cetyltrimethylammonium bromide

This is the first report on the determination of nucleic acids based on the enhancement of resonance light scattering (RLS) of the anionic dye methyl blue (MB) in the presence of cetyltrimethylammonium bromide (CTMAB). In tris(hydroxymethyl) aminomethane buffer of pH 9.0, MB and nucleic acids react with CTMAB to form large particles of complex, which results in strong enhanced RLS signals characterized by three peaks at 334 nm, 393.5 nm and 548 nm. Mechanistic studies show that the enhanced RLS stems from the aggregation of MB on nucleic acids through the bridged and synergistic effect of CTMAB. With the enhanced RLS signals at the best wavelength at 334 nm, the enhanced RLS intensity is proportional to the concentration of nucleic acids in a wide range. The lowest limit of determination was 2.1 ng mL⁻¹, three synthetic samples were analyzed satisfactorily.     

Conversion of teak wood waste into microwave-irradiated activated carbon for cationic methylene blue dye removal: Optimization and batch studies

The objective of this study is to find optimum preparation conditions in converting teak wood waste into activated carbon (TWAC) and to evaluate its performance in adsorbing cationic dye of methylene blue (MB). TWAC was produced via physiochemical activation (potassium hydroxide, KOH chemical treatment, and carbon dioxide, CO₂ gasification) and heated through microwave irradiation technique. With the aid of response surface methodology (RSM), optimized TWAC was successfully synthesized at radiation power, radiation time, and impregnation ratio (IR) of 366 W, 5.30 min, and 1.15 g/g, respectively. These preparation conditions produced TWAC with MB adsorption uptakes of 66.69 mg/g and a yield of 38.23%. Characteristics of TWAC in terms of BET surface area, mesopores surface area, total pore volume, and average pore diameter were determined to be 1345.25 m²/g, 878.63 m²/g, 0.6140 cm³/g, and 2.85 nm, respectively. Isotherm studies divulged that the MB-TWAC adsorption system followed the Langmuir model with a maximum monolayer adsorption capacity of 567.52 mg/g. In terms of kinetic studies, this adsorption system fit pseudo-second order model the best whereas Boyd plot confirmed that the adsorption process was controlled by the film diffusion mechanism. Thermodynamic parameters of enthalpy change, ΔH°, entropy change, ΔS°, Gibbs free energy, ΔG° and Arrhenius activation energy, E_a were calculated to be ?4.06 kJ/mol, 0.06 kJ/mol.K, –22.69 kJ/mol and 16.03 kJ/mol, respectively. The activation and microwave heating methods employed succeeded to produce TWAC with excellent adsorption performance in removing MB dye. TWAC was also successfully regenerated for 5 cycles via microwave heating technique.     

The effect of UV-irradiation on composting of polyethylene modified by cellulose

LDPE and its blend with cellulose, obtained by extrusion, were UV-irradiated with different doses or biodegraded in soil up to 1 year. Simultaneously, the same samples were 1 year biodegraded after 20 h UV pre-irradiation in the same conditions. The course of photo- and biodegradation was monitored by estimation of average molecular weights and polydispersity, gel amount, changes of PE crystallinity and mechanical properties. Moreover, the biodegradation degree was calculated on the basis of carbon dioxide evolved and surface morphological changes were observed by SEM. It was found that biodegradation of PE + cellulose is hampered by intermolecular crosslinking of both components. Although, the rate of decomposition of PE + cellulose blends is low it is enough for disintegration of such materials in the natural environment.     

Influence of adsorption orientation of methyl orange on silver colloids by Raman and fluorescence spectroscopy: pH effect

This work seeks to characterize the UV–Vis absorption, SRES and fluorescence of methyl orange (MO) on silver colloids at different pH. The gradual changes of SERS signals indicate differing adsorption orientations of dyes on silver surface when pH changed and thus, results in different energy transfer efficiencies, i.e., the fluorescence quenching at 428 nm and synchronous enhancement at 560 nm changed gradually with pH increased by step-up. Both experimental evidence and theoretic analysis indicate that, different molecular structures and differing adsorption orientations of dyes on silver surface were existence when pH changed, and thereat caused the diverse spectral phenomena.     

Aggregation of dextran hydrophobically modified by sterically-hindered phenols in aqueous solutions: Aggregates vs. single molecules

The hydrodynamic properties of dextrans hydrophobically modified by sterically-hindered phenols in aqueous solution were characterized by a combination of Cryogenic Transmission Electron Microscopy (Cryo-TEM), fluorescent spectroscopy, and Dynamic Light Scattering (DLS). All solutions investigated contained aggregates the structure, shape, and critical aggregation concentration of which are influenced by the amount of the inserted phenol groups in the polymer matrix. We found that increasing of temperature enhances aggregation. It was established that the critical aggregation concentration could be well approximated by a logarithmic function of the substitution degree of the glycoside units. The results suggest that the proportion of aggregates is nevertheless negligible in comparison with the proportion of single molecules.