Solubility of Two Disperse Dyes Derived from <Emphasis Type="Italic">N</Emphasis>-Alkyl and <Emphasis Type="Italic">N</Emphasis>-Carboxylic Acid Naphthalimides in the Presence of Gemini Cationic Surfactants

The solubility of naphthalimide-based monoazo dyes containing N-ethyl and N-ethanoic acid groups was investigated in the presence of a conventional monomeric counterpart (DTAB) and two cationic gemini surfactants (12-4-12 or 14-4-14) individually. The effective parameters on dye solubility such as temperature, time and concentration of surfactants were investigated by UV–Visible spectrophotometry. The results demonstrate that the solubility of both dyes was considerably increased at concentrations above the surfactant CMC. The wavelength for the maximum absorbance of dyes in the aqueous solution shifts toward longer wavelengths with changes in the concentration of the cationic surfactants. A kinetic study of solubilization of dyes in cationic surfactants solution showed that the rate of solubilization follows the pseudo-first-order reactions. Rates of solubilization were in the range of 0.5 × 10⁻³ to 6.8 × 10⁻³ min⁻¹ for both dyes. The disperse dye containing a carboxylic acid group (dye 2) has a higher solubility rate than the dye containing an alkyl group (dye 1). The type of surfactant has a very low effect on adsorption of dye 1 onto the polyester fibers, whereas changing the surfactant type from DTAB to 12-4-12 or 14-4-14 causes adsorption of dye 2 on polyester to decrease.     

Pt film electrodes prepared by the Pechini method for electrochemical decolourisation of Reactive Orange 16

Electrochemical decolourisation of Reactive Orange 16 was carried out in an electrochemical flow-cell, using as working electrodes a Pt thin film deposited on a Ti substrate (Pt/Ti) prepared by the Pechini method and a pure platinum (Pt) foil. Using the Pt/Ti electrodes better results for dye decolourisation were obtained under milder conditions than those used for pure Pt. For the Pt electrode, colour removal of 93 % (λ = 493 nm) was obtained after 60 min, at 2.2 V vs. RHE, using 0.017 mol L⁻¹ NaCl + 0.5 mol L⁻¹ H₂SO₄ solution. For the Pt/Ti electrode there was better colour removal, 98%, than for the Pt electrode. Moreover, we used 0.017 mol L⁻¹ NaCl solution and the applied potential was 1.8 V. Under this condition after 15 min of electrolysis, more than 80% of colour was removed. The rate reaction constant, assuming a first order reaction, was 0.024 min⁻¹ and 0.069 min⁻¹, for Pt and Pt/Ti electrodes, respectively.     

Mutagenic activity removal of selected disperse dye by photoeletrocatalytic treatment

The degradation of black dye commercial product (BDCP) composed of C.I. Disperse Blue 373, C.I. Disperse Orange 37, C.I. Disperse Violet 93 dyes was investigated by photoelectrocatalysis process. The dyes have shown high mutagenic activity with Salmonella strain YG1041 and TA98 with and without S9. Samples of BCPD dye submitted to conventional chlorination and photoelectrocatalytic oxidation were compared monitoring its products by HPLC using a diode array detector, spectrophotometry UV–vis, TOC removal, and mutagenicity potency. The photoelectrocatalytic method operating with Ti/TiO₂ as anode at +1.0 V and UV illumination presented fast oxidation of test solutions containing 10 mg L⁻¹ of dye in 0.1 mol L⁻¹ NaCl pH 4.0 leading to 100% of discoloration, 67% of mineralization, and negative response to all tested Salmonella strains. The formation of Cl^•, CL₂ ^• on photoelectrocatalytic medium improved the efficiency of the method in relation to conventional chlorination method that promoted 100% of discoloration, but only 8% of TOC removal and more mutagenic product.     

Electrochemical treatment of pharmaceutical azo dye amaranth from waste water

The electrochemical behavior of pharmaceutical azo dye amaranth has been investigated in distilled water and Britton–Robinson buffer. One well-defined irreversible cathodic peak is observed. This may be attributed to the reduction of the –N=N– group. Calculation of the number of electrons transferred in the reduction process has been performed and a reduction mechanism proposed. Results indicate that the electrode process is diffusion controlled. The cathodic peak in the case of controlled potential electrolysis is found to reduce substantially with a decrease in color and absorbance. The reaction has first order kinetics with k value 5.75 × 10⁻² abs min⁻¹. The efficiency of different electrode materials (platinum and steel) for decolorisation is compared. Chemical oxygen demand (COD) decreases substantially from 2,680 to 96 ppm at platinum and to 142 ppm at steel. This translates to 97% COD removal at platinum and 95% at steel.     

DSA electrochemical treatment of olive mill wastewater on Ti/RuO<Subscript>2</Subscript> anode

The electrochemical oxidation of olive mill wastewater (OMW) over a Ti/RuO₂ anode was studied by means of cyclic voltammetry and bulk electrolysis and compared with previous results over a Ti/IrO₂ anode. Experiments were conducted at 300–1,220 mg L⁻¹ initial chemical oxygen demand (COD) concentrations, 0.05–1.35 V versus SHE and 1.39–1.48 V versus SHE potential windows, 15–50 mA cm⁻² current densities, 0–20 mM NaCl, Na₂SO₄, or FeCl₃ concentrations, 80 °C temperature, and acidic conditions. Partial and total oxidation reactions occur with the overall rate being near first-order kinetics with respect to COD. Oxidation at 28 Ah L⁻¹ and 50 mA cm⁻² leads to quite high color and phenols removal (86 and 84%, respectively), elimination of ecotoxicity, and a satisfactory COD and total organic carbon reduction (52 and 38%, respectively). Similar performance can be achieved at the same charge (28 Ah L⁻¹) using lower current densities (15 mA cm⁻²) but in the presence of various salts. For example, COD removal is less than 7% at 28 Ah L⁻¹ in a salt-free sample, while addition of 20 mM NaCl results in 54% COD reduction. Decolorization of OMW using Ti/RuO₂ anode seems to be independent of the presence of salts in contrast with Ti/IrO₂ where addition of NaCl has a beneficial effect on decolorization.     

Electrochemical pretreatment of distillery wastewater using aluminum electrode

Electrochemical (EC) oxidation of distillery wastewater with low (BOD₅/COD) ratio was investigated using aluminum plates as electrodes. The effects of operating parameters such as pH, electrolysis duration, and current density on COD removal were studied. At a current density of 0.03 A cm⁻² and at pH 3, the COD removal was found to be 72.3%. The BOD₅/COD ratio increased from 0.15 to 0.68 for an optimum of 120-min electrolysis duration indicating improvement of biodegradability of wastewater. The maximum anodic efficiency observed was 21.58 kg COD h⁻¹ A⁻¹ m⁻², and the minimum energy consumption observed was 0.084 kWh kg⁻¹ COD. The kinetic study results revealed that reaction rate (k) decreased from 0.011 to 0.0063 min⁻¹ with increase in pH from 3 to 9 while the k value increased from 0.0035 to 0.0102 min⁻¹ with increase in current density from 0.01 to 0.03 A cm⁻². This study showed that the COD reduction is more influenced by the current density. The linear and the nonlinear regression models reveal that the COD reduction is influenced by the applied current density.     

On the activation and physical degradation of boron-doped diamond surfaces brought on by cathodic pretreatments

The electrochemical activation and physical degradation of boron-doped diamond (BDD) electrodes with different boron doping levels after repeated cathodic pretreatments are reported. Galvanostatic cathodic pretreatment passing up to −14000 C cm⁻² in steps of −600 C cm⁻² using −1 A cm⁻² caused significant physical degradation of the BDD surface, with film detachment in some areas. Because of this degradation, a great increase in the electrochemically active area was observed in Tafel plots for the hydrogen evolution reaction (HER) in acid media. The minimum cathodic pretreatment needed for the electrochemical activation of the BDD electrodes without producing any observable physical degradation on the BDD surfaces was determined using electrochemical impedance spectroscopy (EIS) measurements and cyclic voltammetry: −9 C cm⁻², passed at −1 A cm⁻². This optimized cathodic pretreatment can be safely used when electrochemical experiments are carried out on BDD electrodes with doping levels in the range between 800 and 8000 ppm.     

Dye removal from colored textile wastewater using acrylic grafted nanomembrane

In this paper, the dye removal ability of the acrylic grafted polysulfone nanomembrane using ultraviolet radiation was studied to remove dyes from colored textile wastewater. Acrylic acid was used to modify polysulfone ultrafiltration membrane. The effect of different operating parameters such as pressure, salt concentration and chemical structure of dyes was evaluated. Data indicated that the photografted membrane has acceptable performance both in terms of flux and rejection. The dye rejection and hydraulic permeability were 86–99.9% and 7.6 L m^{− 2} h^{− 1} bar^{− 1}, respectively. It was found that the rejection of dyes decreased with salt concentration due to a decrease of the Donnan effect. Also, the low molecular weight dyes and highly charged dyes were more sensitive in the presence of salts. Addition of 80 mM Na₂SO₄ in dye solution decreased the dye rejection more than 15%. The rejection enhancement for all cases was negligible by increasing driving pressure from 1 to 4 bar. Dyes with low charger were more sensitive to operating pressure than that of dyes with higher charges. All findings supported that acrylic grafted nanomembrane is potentially capable to separate dyes from colored textile effluent.     

Electrochemical treatment of water containing chlorides under non-ideal flow conditions with BDD anodes

In this work a undivided parallel plate cell equipped with boron doped diamond (BDD) anode was tested as electrochemical reactor for disinfection of water. Two configurations were adopted: a single pass configuration (SPC) and a recirculated configuration (RC) in which also a reservoir was inserted in the hydraulic circuit. In both the experimental configurations the system worked in continuous mode with a flow rate ranging from 0.05 to 0.42 dm³ min⁻¹; in the RC the recirculating flow rate ranged from 0.45 to 6 dm³ min⁻¹. Thermostated (25 °C) galvanostatic electrolyses were carried out with aqueous solutions containing 100 mg dm⁻³ of chloride ions: values of current density from 2.5 to 5.0 mA cm⁻² were used. Steady state data revealed that active chlorine and chlorate ions were the main oxidation products. Particular attention was paid to the hydrodynamics both for SPC and RC: pulse-response curves were experimentally obtained with an inert tracer, and the behaviour of the system was interpreted by models based on a combination of ideal flow reactors, bypass flow elements, and dead zones. The hydrodynamic models were utilized to predict the outlet concentration of the electrolysis products. A good agreement between model predicted and experimental data was obtained for a wide range of experimental conditions. Preliminary disinfection tests were then performed using Escherichia coli as model microorganism. Results were discussed in terms of both disinfection efficiency and by-products formation.     

Effect of electrolyte concentration on morphology,microstructure and electrochemical impedance of anodic oxide film on titanium alloy Ti-10V–2Fe–3Al

Anodic oxide films were fabricated on titanium alloy Ti-10V–2Fe–3Al in ammonium tartrate solutions at the concentrations: 1, 3, 5, 10 and 15 g L⁻¹. The morphological characteristics and microstructures of the films of the alloy were studied by optical microscopy (OM) and Raman spectroscopy (Raman), respectively. The electrochemical impedances of the films in 0.5 mol L⁻¹ H₂SO₄ solution were investigated by electrochemical impedance spectroscopy (EIS). It was showed that different electrolyte concentrations led to different change rates of anodizing forming voltage. The change rate significantly affected the morphology, microstructure and electrochemical impedance of anodic oxide film. When electrolyte concentration was 5 g L⁻¹, anodic oxide film was the most uniform, exhibited by the least and smallest breakpoints on the film. In addition, the amount of crystal phase of the film was the largest at 5 g L⁻¹, showed by the highest intensity of Raman peaks. Furthermore, the electrochemical impedance of the film of the alloy was the greatest at 5 g L⁻¹, demonstrated by the highest values of polarization resistances and lowest values of capacitances. These phenomenon were associated with the minimum value of the change rate of anodizing forming voltage at 5 g L⁻¹.     

Electroanalysis of urinary l-dopa using tyrosinase immobilized on gold nanoelectrode ensembles

The performance of an amperometric biosensor constructed by associating tyrosinase (Tyr) enzyme with the advantages of a 3D gold nanoelectrode ensemble (GNEE) is evaluated in a flow-injection analysis (FIA) system for the analysis of l-dopa. GNEEs were fabricated by electroless deposition of the metal within the pores of polycarbonate track-etched membranes. A simple solvent etching procedure based on the solubility of polycarbonate membranes is adopted for the fabrication of the 3D GNEE. Afterward, enzyme was immobilized onto preformed self-assembled monolayers of cysteamine on the 3D GNEEs (GNEE-Tyr) via cross-linking with glutaraldehyde. The experimental conditions of the FIA system, such as the detection potential (−0.200 V vs. Ag/AgCl) and flow rates (1.0 mL min⁻¹) were optimized. Analytical responses for l-dopa were obtained in a wide concentration range between 1 × 10⁻⁸ mol L⁻¹ and 1 × 10⁻² mol L⁻¹. The limit of quantification was found to be 1 × 10⁻⁸ mol L⁻¹ with a resultant % RSD of 7.23% (n = 5). The limit of detection was found to be 1 × 10⁻⁹ mol L⁻¹ (S/N = 3). The common interfering compounds, namely glucose (10 mmol L⁻¹), ascorbic acid (10 mmol L⁻¹), and urea (10 mmol L⁻¹), were studied. The recovery of l-dopa (1 × 10⁻⁷ mol L⁻¹) from spiked urine samples was found to be 96%. Therefore, the developed method is adequate to be applied in the clinical analysis.     

Photoelectrocatalysis reactivity of independent titania nanotubes

Two types of independent titania nanotube arrays with the separated tube wall structure have been fabricated by a controlled anodization process and used for photoelectrocatalysis (PEC) applications. The photocatalysis degradation efficiency of the organic pollutant is improved from 6.0 to 9.2% through increasing tube length and inter-tube space. The PEC degradation efficiency is 20.4% at an applied potential of 2.885 V for titania long nanotube array. An electro-Fenton-assisted PEC reaction system has been developed using titania long nanotube array and an iron sheet as two anodes in a parallel connection and a multiporous carbon as one cathode. The current distribution among three functional electrodes is conducted to optimize titania PEC reaction and electro-Fenton reaction. Accordingly, the degradation efficiency is improved from 20.4% in PEC to 60.2% in electro-Fenton-assisted PEC, and the mineralization efficiency is also improved from 8.1 to 37.4%. The corresponding reaction rate constant of 5.19 × 10⁻³ min⁻¹ is even higher than that of 3.98 × 10⁻³ min⁻¹ for the sum of individual oxidation reactions of titania PEC, electro-Fenton, and anodic electrolysis.     

Preparation and performance of novel thermal stable composite nanofiltration membrane

The novel thermal stable composite nanofiltration membranes were prepared through the interfacial polymerization of piperazine and trimesoyl chloride on the poly (phthalazinone ether) ultrafiltration substrate. The effects of polymerization and testing conditions on membrane performance were studied. The surface morphologies of the substrate and the composite membranes were observed by means of scanning electron microscopy (SEM) and atomic force microscopy (AFM). The separation properties of membranes for dyes and salts were tested. The composite membranes show good thermal stability. The rejection for Na2SO4 was kept over 96%, while the flux reached 400 L·m⁻²·h⁻¹ when it was tested at 1.0 MPa and 80°C. When tested at 1.0 MPa and 60°C, the rejection of the composite membrane for dyes was kept at high level, and the flux reached 180–210 L·m⁻²·h⁻¹, while the rejection for NaCl was lower than 20%. __________ Translated from the Journal of Functional Materials, 2007, 38(12): 2025–2027, 2031 [译自: 功能材料]     

Electrochemical determination of plant-derived leuco-indigo after chemical reduction by glucose

Electrochemical determination of redox active dye species is demonstrated in indigo samples contaminated with high levels of organic and inorganic impurities. The use of a hydrodynamic electrode system based on a vibrating probe (250 Hz, 200 μm lateral amplitude) allows time-independent diffusion controlled signals to be enhanced and reliable concentration data to be obtained under steady state conditions at relatively fast scan rates up to 4 V s⁻¹. In this work the indigo content of a complex plant-derived indigo sample (dye content typically 30%) is determined after indigo is reduced by addition of glucose in aqueous 0.2 M NaOH. The soluble leuco-indigo is measured by its oxidation response at a vibrating electrode. The vibrating electrode, which consisted of a laterally vibrating 500 μm diameter gold disc, is calibrated with Fe(CN)₆ ^3−/4− in 0.1 M KCl and employed for indigo determination at 55, 65, and 75 °C in 0.2 M NaOH. Determinations of the indigo content of 25 different samples of plant-derived indigo are compared with those obtained by conventional spectrophotometry. This comparison suggests a significant improvement by the electrochemical method, which appears to be less sensitive to impurities.     

Preparation and electrochemical performance of gel polymer electrolytes with a novel star network

Well-defined star shaped polymers with α-Cyclodextrin (α-CD) core linking PMMA-block arms were synthesized by atom transfer radical polymerization (ATRP). Gel polymer electrolytes (GPEs) were prepared by encapsulating electrolyte solution of 1 mol L⁻¹ of LiClO₄/EC-PC (volume 1:1) into the obtained star shaped polymer host. The ionic conductivity of the GPEs and the cycling characteristics of LiCoO₂/GPEs/Graphite cell were studied by electrochemical impedance spectroscopy and charge-discharge testing, respectively. The results indicate that the GPEs have a high ionic conductivity up to 1.63 × 10⁻³ S cm⁻¹ at room temperature and exhibit a high electrochemical stability potential of 4.5 V (vs. Li/Li⁺). The discharge capacity of LiCoO₂/GPEs/Graphite cell is about 98% of its initial discharge capacity after 20 cycles at 0.1 C rate. Discharge capacity of the model cell with GPEs is stable with charge-discharge cycling.     

Electrochemical degradation of the Acid Blue 62 dye on a β-PbO<Subscript>2</Subscript> anode assessed by the response surface methodology

The electrochemical degradation of the anthraquinonic dye Acid Blue 62 in a filter-press reactor on a Ti/Pt/β-PbO₂ anode was investigated using the response surface methodology with the variables: current density, pH, [NaCl], and temperature. The system’s modeling was carried out with the charge required for 90% decolorization (Q ⁹⁰) and the chemical oxygen demand removal percentage after a 30 min electrolysis (COD ³⁰), with good correlations between predicted and observed values. Best conditions for decolorization were attained in acidic solutions (pH = 4) with medium to high [NaCl] (1.0–2.0 g L⁻¹) and lower temperature due to the prevalent oxidant species HOCl and Cl₂. Optimal conditions for COD ³⁰ removal were attained at high current densities in pH > 5 solutions with high [NaCl], when the prevalent oxidant species are HOCl and OCl⁻. The lowest charge per unit volume of the electrolyzed solution necessary for total mineralization was attained at pH 11.     

Poly(acrylamide/maleic acid)–sepiolite composite hydrogels for immobilization of invertase

Poly(acrylamide/maleic acid) and sepiolite (PAMS) composite hydrogel was prepared and used for the immobilization of invertase. In FTIR analysis, the characteristic bands of composite such as –OH, –COOH, Si–OH show the evidence of sepiolite and maleic acid. In TGA analysis, water loss, decomposition of amide side groups and breakdown of main chain regions of the composite were found. The parameters of equilibrium swelling, initial swelling rate, diffusional exponent, and diffusion coefficient were calculated and evaluated from swelling experiments in distilled water. Invertase was immobilized onto PAMS by adsorption and poly(acrylamide/maleic acid)–sepiolite–invertase (PAMSI) was prepared. Optimum pH, optimum temperature values for free invertase and PAMSI were found. It was found that K _m values of free invertase and PAMSI were 11.3 and 34.1 mM, respectively. V _max value was found that 2.0 μmol min⁻¹ for free invertase and 13.9 μmol min⁻¹ for PAMSI, respectively. PAMSI showed excellent temperature, operational and storage stability.     

Nanostructured Systems Containing Rutin: In Vitro Antioxidant Activity and Photostability Studies

The improvement of the rutin photostability and its prolonged in vitro antioxidant activity were studied by means of its association with nanostructured aqueous dispersions. Rutin-loaded nanocapsules and rutin-loaded nanoemulsion showed mean particle size of 124.30 ± 2.06 and 124.17 ± 1.79, respectively, polydispersity index below 0.20, negative zeta potential, and encapsulation efficiency close to 100%. The in vitro antioxidant activity was evaluated by the formation of free radical ·OH after the exposure of hydrogen peroxide to a UV irradiation system. Rutin-loaded nanostructures showed lower rutin decay rates [(6.1 ± 0.6) 10⁻³ and (5.1 ± 0.4) 10⁻³ for nanocapsules and nanoemulsion, respectively] compared to the ethanolic solution [(35.0 ± 3.7) 10⁻³ min⁻¹] and exposed solution [(40.1 ± 1.7) 10⁻³ min⁻¹] as well as compared to exposed nanostructured dispersions [(19.5 ± 0.5) 10⁻³ and (26.6 ± 2.6) 10⁻³, for nanocapsules and nanoemulsion, respectively]. The presence of the polymeric layer in nanocapsules was fundamental to obtain a prolonged antioxidant activity, even if the mathematical modeling of the in vitro release profiles showed high adsorption of rutin to the particle/droplet surface for both formulations. Rutin-loaded nanostructures represent alternatives to the development of innovative nanomedicines.     

Studies on auramine dye adsorption on psidium guava leaves

Removal of auramine dye from aqueous waste solutions was investigated by using very cheap and biosorbent, withered guava tree leaves and activated carbon. Guava leaves are readily available in the western and northern parts of India throughout the year, and hence form a cost effective alternative for removal of dyes from waste waters. The optimum contact time was found to be 120 min. in a pH range of 8–9 for 92–94% removal of the dye from aqueous solutions containing 150 mg/L of auramine dye using 2 g of the adsorbent. The effect of pH, dye concentration, sorbent dosage, temperature and contact time on the dye removal efficiency has been studied. Experimental results were found to fit both Freundlich and Langmuir models. Since the dye contains a cationic species, the removal efficiency was highest in a pH range of 8–9. Continuous adsorption studies in a packed column showed 100% removal efficiency for a flow rate of 10 ml·min⁻¹. When compared with the activated carbon, it was also found that adsorbent derived from guava leaves is more efficient in removal of dye.     

Wastewater treatment by adsorption with electrochemical regeneration using graphite-based adsorbents

An innovative technology for wastewater treatment using adsorption and electrochemical regeneration has been developed at the University of Manchester. The process uses a low capacity graphitic adsorbent material (a graphite intercalation compound, Nyex^TM 1000) which can be regenerated electrochemically. In this study, we investigate the characteristics of a new, partially porous adsorbent material, Nyex^TM 2000 which offers increased surface area in comparison with Nyex^TM 1000. Nyex^TM 2000 was found to have an adsorption capacity of almost three times that of Nyex^TM 1000. The electrical conductivity of a Nyex^TM 2000 was found to be double that of Nyex^TM 1000, enabling improvements in the electrochemical regeneration characteristics. The removal of an anionic azo dye, acid violet 17, from aqueous solution using Nyex^TM 1000 and 2000 was investigated under various operating conditions. The adsorption of acid violet 17 on Nyex^TM 2000 was found to be comparatively fast with 75 % of the equilibrium capacity being achieved within 5 min. The parameters affecting the regeneration efficiency including the charge passed, current density, treatment time, adsorbent bed thickness, and pH were investigated. An electrochemical regeneration efficiency of around 100 % was achieved for a fully loaded Nyex^TM 2000 in a sequential batch electrochemical cell with a regeneration time of 60 min and a charge passed of 100 C g⁻¹ at a current density of 14 mA cm⁻². The charge required for electrochemical regeneration was found to be approximately equal to theoretical charge required for complete oxidation of the adsorbed acid violet 17, making process design relatively simple. Nyex^TM 2000 was found to be an economic adsorbent with relatively small electrical energy consumption required (31 J mg⁻¹ of acid violet 17 treated, compared to 52 J mg⁻¹ of acid violet 17 for Nyex^TM 1000). Multiple adsorption/regeneration cycles presented no loss in adsorptive capacity and material loses over five adsorption/regeneration cycles.