Photocatalytic degradation of dye effluent by titanium dioxide pillar pellets in aqueous solution

Photocatalytic oxidation (PCO) process is an effective way to deal with organic pollutants in wastewater which could be difficult to be degraded by conventional biological treatment methods. Normally the TiO2 powder in nanometre size range was directly used as photocatalyst for dye degradation in wastewater. However the titanium dioxide powder was arduous to be recovered from the solution after treatment. In this application, a new form of TiO2 (i.e. pillar pellets ranging from 2.5 to 5.3 mm long and with a diameter of 3.7 mm) was used and investigated for photocatalytic degradation of textile dye effluent. A test system was built with a flat plate reactor (FPR) and UV light source (blacklight and solar simulator as light source respectively) for investigating the effectiveness of the new form of TiO2. It was found that the photocatalytic process under this configuration could efficiently remove colours from textile dyeing effluent. Comparing with the TiO2 powder, the pellet was very easy to recovered from the treated solution and can be reused in multiple times without the significant change on the photocatalytic property. The results also showed that to achieve the same photocatalytic performance, the FPR area by pellets was about 91% smaller than required by TiO2 powder. At least TiO2 pellet could be used as an alternative form of photocatalyst in applications for textile effluent treatment process, also other wastewater treatment processes.

Polypyrrole nanoparticles and dye absorption properties

Polypyrrole (PPy) nanoparticles were prepared by using microemulsion polymerization processes at 3 °C. Particle characterization was performed by using FTIR, elementary analysis, UV–vis spectra and scanning electron microscope (SEM). The size of the nanoparticles varied from about 50 to 100 to 100 to 200 nm with the change in concentration of surfactant from 0.8 to 0.44 M. Polypyrrole nanoparticles were dedoped by a 10% NaOH solution, followed by a redoping process using a nuclear fast red kernechtrot dye, which has a sulfonate group. Dedoping changed the optical absorption properties of the nanoparticles.

Photocatalytic decolorization of lanasol blue CE dye solution using a flat-plate reactor

This paper reports the effectiveness of the photocatalysis TiO₂ in degrading Lanasol Blue CE. A flat-plate reactor (FPR) with a reactor area of 0.37 m² and ultraviolet (UV) light source of six 36 W blacklight lamps was used in the study. Operating variables including dosage of the photocatalyst, flow rates through the FPR, UV intensity, and tilted angle of the reactor were investigated to degrade Lanasol Blue CE. Results showed that the photocatalytic process can efficiently remove the color in textile dyeing effluent. The degradation process was approximated using first-order kinetics. The photocatalytic apparent reaction rate increased with the increasing UV intensity received by the photocatalyst TiO₂ in slurry. The liquid flow rate and tilted angle influenced the film thickness. The apparent reaction rate constant was mainly determined by the liquid film thickness, UV intensity, and the dosage of the photocatalyst. The findings of this research can be utilized as preliminary input for potential solar photocatalytic applications on color removal from dye solutions.

The effects of dye dopants on the conductivity and optical absorption properties of polypyrrole

Ten anionic compounds, including four acidic dyes, were used to dope polypyrrole powder. The effects of the dopants on density, optical absorption and conductivity of the polypyrroles were studied. The presence of the dopant in the conducting polymer matrix was verified by ATR-FTIR spectroscopy. Density function theory (DFT) simulation was used to understand the effect of the dopants on the solid structure, optical absorption and energy band structures. Anthraquinone-2-sulfonic acid-doped polypyrrole yielded the highest conductivity. The dye-doped polypyrrole showed an enhancement in its UV–vis optical absorption.

Effects of atmospheric pressure plasma on dye uptake by the surface of wool

A woven pure wool fabric has been exposed to atmospheric pressure plasma for 30 seconds using a pilot-scale. commercial machine. X-ray photoelectron spectral data revealed large increases in oxygen and nitrogen. and a large reduction in carbon. on the surfaces of the plasma-treated fibres. A CIN ratio of 3.55 for plasma-treated wool was consistent with removal of the covalently-bound fatty acids from the surface of the cuticle cells. resulting in exposure of the proteinaceous epicuticle. Dye staining experiments revealed that the back of the fabric had received the same, uniform level of treatment as the face, despite the fact that only the face had been directly exposed to the plasma. Dyes (1 % oww) were applied to fabric at 50°C (liquor ratio =40: 1) and pH values from 3 to 6. The relatively low temperature of 50°C was selected in order to accentuate the effects of plasma on the rate of dye uptake. Under these conditions, dye was adsOibed onto the fibre surfaces, with very little penetration into the fibres. Effects of the plasma treatment on the rate of dyes adsorption were dyespecific. No significant effects of plasma on the rate of dye uptake were observed with relatively hydrophobic dyes, but hydrophilic dyes were adsorbed more rapidly by the plasmatreated fabric. It would appear that for more hydrophobic dyes, hydrophobic effects are more important for the adsorption of dyes by the plasma-treated fibres, even though these fibres were quite hydrophilic. On the other hand. it is concluded that for more hydrophilic dyes, electrostatic effects are more important for adsorption by the plasma-treated fibre.

Nano zinc oxide for UV protection of textiles

This paper describes the effect on the fading of dyed polyester fabrics in artificial sunlight, when the Ultra Violet (UV) component of the radiation was blocked by coating the fabric with zinc oxide nanoparticles, dispersed in an acrylic polymer. Zinc oxide is photoactive and generates superoxide and hydroxyl radicals (Reactive Oxygen Species; ROS) when irradiated with UV in the presence of oxygen and water. The results for the four dyes studied show that different dye chromophores interact differently with ROS. Selection of dyes with anti oxidant properties or addition of other anti oxidants may reduce the adverse effects of ROS

One-bath union dyeing of wool/polytrimethylene terephthalate blends

The one-bath dyeing of blends of polytrimethylene terephthalate (PTT) staple and wool has been investigated. The exhaustion of selected Terasil disperse dyes on PTT fibre and Lanasol reactive dyes on wool was measured as a function of temperature, together with the cross-staining of the Terasil dyes on the wool component and the Lanasol dyes on PTT component. Most Terasil disperse dyes achieved satisfactory dye uptake on PTT at 110 °C, whereas on conventional polyester (polyethylene terephthalate) temperatures of up to 130 °C are required. An optimised union-dyeing technique for wool/PTT blends was developed which minimised the staining of Terasil disperse dyes on wool and produced dyed goods with high levels of wet colour fastness. Carriers were not required to enhance the dyeability of PTT at low temperatures. The wool component appeared to be protected against damage at 110 °C by the reactive dyes. The results indicate the potential for blending PTT fibre and wool to produce fabrics that are easier to dye at lower temperatures than conventional wool/polyester blends.

Effects of undoped and manganese-doped zinc oxide nanoparticles on the colour fading of dyed polyester fabrics

This paper describes the effects of applying coatings of an acrylic polymer containing nanoparticles of zinc oxide (ZnO) on the fading rate in artificial sunlight of polyester fabrics dyed with disperse dyes containing anthraquinone and benzopyran chromophores. Factors affecting the transparency and UV absorbance of the coatings are discussed. Removing the UV component of sunlight with ZnO nanoparticles markedly decreased the fading rate of the dyes, provided the polymer/ZnO film was not in direct contact with the fabric. When the treatment was applied directly to the fabrics, however, the protection against colour fading was different for the two dyes studied. Whereas the rate of colour fading of a benzopyran dye, of relatively low lightfastness, was decreased by the polymer-ZnO film, the treatment increased the fading rate of the dye of higher lightfastness, based on anthraquinone. This effect has been attributed to the generation of reactive oxygen species (ROS) when ZnO is exposed to UV. The effect of decreasing the photoactivity of ZnO by doping with manganese has been examined. For the benzopyran dye, the UV protection was greatly increased, whereas a much smaller improvement was found for the anthraquinone-based dye.

Electrostatic complex of didodecyldimethylammonium and DNA: Langmuir monolayer, Langmuir–Blodgett film and dye recognition at air/water interface

DNA–didodecyldimethylammonium (DNA–DDDA) electrostatic complex was prepared and characterized through Fourier transformation infrared (FT-IR), 1H NMR and circular dichroism (CD) spectroscopy. When the dye molecule aqueous solutions were used as the subphase, the interaction between three dye molecules, acridine orange (AO), ethidium bromide (EB) and 5,10,15,20-tetrakis(4-N-methylpyridyl)porphine tetra(p-toluenesulfonate) (TMPyP) and the complex at air/solution interface were investigated through the surface pressure–area (π–A) isotherms, Brewster angle microscopy and UV-Vis spectroscopy, respectively. Our investigation indicates that the interaction capabilities of the three dyes to DNA–DDDA complex are different and present an order of TMPyP>AO>EB. For the interaction forms, we believe that TMPyP intercalates into the double helix of DNA, and AO adsorbs onto the surface of the DNA. As for EB, the measured signal is too weak to give a definite interaction form in the present experiment.

Dye-sensitized nanocrystalline solar cells incorporating ethylmethylimidazolium-based ionic liquid electrolytes

High-performance dye-sensitized solar cells incorporating electrochemically stable non-volatile electrolytes are especially desirable devices. In particular, ionic liquid systems based on ethylmethylimidazolium dicyanamide seem to be promising for this purpose. These have triggered our interest in the properties of further ethylmethylimidazolium-based ionic liquids with anions which are close relatives of dicyanamide. In this study, the effect of three different anions, tricyanomethanide, dicyanamide and thiocyanate, on the performance of dye-sensitized solar cells have been investigated. Both the short circuit photocurrent and conversion efficiency are increased with decreasing viscosity of the ionic liquids under comparable conditions. A conversion efficiency of 2.1% at 30% light intensity was observed for the cell containing the tricyanomethanide salt, which has lowest viscosity among the three ionic liquids, while efficiencies of 0.7% and 1.7% at the same light intensity were observed in the case of dicyanamide and thiocyanate salts, respectively, as an electrolyte.

PEDOT-coated counter electrodes for dye-sensitized solar cells

Poly(3,4-ethylenedioxythiophene) (PEDOT)-coated counter electrodes for dye-sensitized solar cells have been prepared at ambient temperature and without the use of iron-based oxidants, using an ionic liquid for the synthesis of the PEDOT. These electrodes show comparable electrocatalytic performance with conventional Pt-coated counter electrodes (solar cell efficiencies >7.5%).

Ambient temperature plastic crystal electrolyte for efficient, all-solid-state dye-sensitized solar cell

Doping the molecular plastic crystal of succinonitrile with solid N-methyl-N-butylpyrrolidinium iodide salt and iodine has produced a highly conductive solid iodide/triiodide conductor. Furthermore, it was employed for a highly efficient, all-solid-state dye-sensitized solar cell.