Falah H. Hussein

Photo-oxidation of alcohols catalysed by platinised titanium dioxide

Abstract Irradiation of alcohols in benzene in the presence of platinised titanium dioxide provides a clean and convenient procedure for the synthesis of aldehydes and ketones on preparative scale.

Photocatalytic dehydrogenation of liquid propan-2-ol by platinized anatase and other catalysts

The photocatalytic dehydrogenation of liquid propan-2-ol by suspensions of platinum and other metals supported on anatase has been investigated by following propanone formation under an N2 atmosphere. Measurements were made over the range 278–303 K using filtered 366 nm u.v. radiation.With Pt/TiO2 prepared by H2 reduction there was an appreciable dark reaction, which was absent with catalysts prepared by photodeposition. Reaction on photodeposited catalysts was consistently associated with an activation energy of 20 kJ mol–1, although the activity fell in the sequence Pt/TiO2 > Pd/TiO2 > Rh/TiO2 > Au/TiO2= 0 for catalysts with a metal content of 0.5 wt%. The activation energy is identical to that for photoreaction on the anatase support in the presence of O2 and is believed to be associated with the transport of photoelectrons through the anatase to either metal particles or adsorbed O2.

Photocatalytic Degradation of Textile Dyeing Wastewater Using Titanium Dioxide and Zinc Oxide

Photodegradation of a real textile dyeing wastewater taken from Hilla textile factory in Babylon Governorate, Iraq have been investigated. Photocatalytic degradation was carried out over suspensions of titanium dioxide or zinc oxide under ultraviolet irradiation. Photodegradation percentage was followed spectrophometrically by the measurements of absorbance at λmax equal to 380 nm. The rate of photodegradation increased linearly with time of irradiation when titanium dioxide or zinc oxide was used. A maximum color removal of 96% was achieved after irradiation time of 2.5 hours when titanium dioxide used at 303K and 82% color reduction was observed when zinc oxide used for the same period and at the same temperature. The effect of temperature on the efficiency of photodegradation of dyestuff was also studied. The activation energy of photodegradation was calculated and found to be equal to 21 ± 1 kJ mol-1 on titanium dioxide and 24 ± 1 kJ mol-1 on zinc oxide.

Photocatalytic dehydrogenation of liquid alcohols by platinized anatase

The photocatalytic dehydrogenation of liquid methanol, ethanol, propan-1-ol and propan-2-ol has been investigated using platinized anatase and 366 nm u.v. radiation over the range 278–303 K. Activities and activation energies for carbonyl-compound formation were effectively identical for the four alcohols on Pt(0.5)/TiO2 prepared by photodeposition. The activation energy of 20 kJ mol–1 is associated with photoelectron transport through the anatase to the Pt particles. With Pt(0.5)/TiO2 prepared by impregnation and H2reduction, identical activities for the four alcohols were achieved after O2 treatment. From the effect of u.v. intensity on the rate of propanone formation at 293 K, the limiting quantum yield was found to be 0.45 for photodeposited Pt(0.5)/TiO2 under N2 and 0.82 for support anatase under O2. Arrhenius plots for reaction at reduced u.v. intensities showed that the activation energy fell to zero when these quantum yields were achieved. Different mechanisms follow from the manner in which photoholes are surface trapped; two mechanisms for dehydrogenation with a limiting quantum yield of 0.5 are discussed.

Effect of Chemical and Physical Properties of River Water in Shatt Al-Hilla on Phytoplankton Communities

This paper aims to study the chemical and physical properties in the ecological system of Shatt Al-Hilla in Babylon Governorate in Iraq and its effect on phytoplankton population. In this context, several limnological parameters were evaluated during the period from December 2003 through November 2004 from four sampling stations sited along Shatt Al-Hilla. The physical parameters included: temperature, turbidity and electrical conductivity. The chemical parameters included: pH, alkalinity dissolved oxygen, total hardness and the concentrations of nitrite, nitrate, phosphate and sulphate. A total of 154 species were recorded. Ninety-seven species of the total belong to Bacillariophyceae, 37 species belong to Chlorophyceae, 13 species to Cyanophyceae, 5 species to Chrysophyceae, and 2 species to Euglenophyceae. Bimodal variation of phytoplankton was observed. Five genus of phytoplankton were the highest number of species ( Nitzschia, Navicula, Gomphonema, Cymbella and Scendesmus). Some species was occurred continuously during study period such as, Cyclotella ocellata, Cyclotella meneghiniana, Aulacoseria distans, and Gomphonema abbreviatum. The phytoplankton communities at all sampling sites showed a clear seasonal variation in phytoplankton cell number. However, no significant correlation between total cell number of phytoplankton and nutrient concentration was observed. The study was revealed the city sewage discharge, agriculture and urban run-off were affecting the water quality of Shatt Al-Hilla.

Role of Platinum Deposited on TiO2 in Photocatalytic Methanol Oxidation and Dehydrogenation Reactions

Titania modified nanoparticles have been prepared by the photodeposition method employing platinum particles on the commercially available titanium dioxide (Hombikat UV 100). The properties of the prepared photocatalysts were investigated by means of the Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), atomic force microscopy (AFM), and UV-visible diffuse spectrophotometry (UV-Vis). XRD was employed to determine the crystallographic phase and particle size of both bare and platinised titanium dioxide. The results indicated that the particle size was decreased with the increasing of platinum loading. AFM analysis showed that one particle consists of about 9 to 11 crystals. UV-vis absorbance analysis showed that the absorption edge shifted to longer wavelength for 0.5% Pt loading compared with bare titanium dioxide. The photocatalytic activity of pure and Pt-loaded TiO2 was investigated employing the photocatalytic oxidation and dehydrogenation of methanol. The results of the photocatalytic activity indicate that the platinized titanium dioxide samples are always more active than the corresponding bare TiO2 for both methanol oxidation and dehydrogenation processes. The loading with various platinum amounts resulted in a significant improvement of the photocatalytic activity of TiO2. This beneficial effect was attributed to an increased separation of the photogenerated electron-hole charge carriers.

Enhancing the photocatalytic activity of TiO2 by pH control: a case study for the degradation of EDTA

The photocatalytic degradation of EDTA has been investigated in detail under pH-controlled conditions employing the pH-stat technique. The results indicate that by holding the pH constant (i.e., at pH 5) during the experiment, the photocatalytic degradation rate is enhanced by ca. 50% as compared with measurements carried out under “free-floating” pH conditions, i.e., with the pH being adjusted to 5 at the beginning of the reaction. The higher photocatalytic activity at a constant pH of 5 is explained by the higher adsorptivity of EDTA on TiO2 at this pH as evinced from the dark adsorption measurements. Investigations carried out at different light intensities indicate that the rate of the photocatalytic EDTA degradation is proportional to the square root of the light intensity at moderate values becoming independent from the light intensity at higher values. The activation energies for the photocatalytic EDTA degradation and for its complete mineralization, respectively, have been determined to be 21.54 ± 1.4 kJ mol−1 and 16.4 ± 0.5 kJ mol−1, respectively, employing the Arrhenius data treatment. This difference is explained by the fact that the intermediates formed upon the photocatalytic EDTA degradation are less resistant against their photocatalytic mineralization than the parent molecule.

Photochemical Treatments of Textile Industries Wastewater

Textile industry is one of the most water and chemical intensive industries worldwide due to the fact that 200-400 liters of water are needed to produce 1 kg of textile fabric in textile factories (Correia et al., 1994 & Orhon et al., 2003). The water used in this industry is almost entirely discharged as waste. Moreover, the loss of dye in the effluents of textile industry can reach up to 75% (Couto & Toca-Herrera, 2006). The effluents are considered very complex since they contain salt, surfactants, ionic metals and their metal complexes, toxic organic chemicals, biocides and toxic anions. Azo dyes are regarded as the largest class of synthetic. Approximately, 50–70% of the available dyes for commercial applications are azo dyes followed by the anthraquinone group (Konstantinou & Albanis, 2004). Azo dyes are classified according to the presence of azo bonds (–N=N–) in the molecule i.e., monoazo, diazo , triazo etc. and also sub-classified according to the structure and method of applications such as acid, basic, direct, disperse, azoic and pigments (Bhutani, 2008). Some azo dyes and their dye precursors are well-known of high toxicity and suspected to be human carcinogens as they form toxic aromatic amines (Gomes et al., 2003 & Stylidi et al., 2003). Different physical, chemical and biological as well as the various combinations of pretreatment and post-treatment techniques have been developed over the last two decades for industrial wastewaters treatment in order to meet the ever-increasing requirements of human beings for water. Though there are numerous studies published in this field, most of the techniques adopted by these researchers are uneconomical, ineffective or impractical uses (Cooper, 1995 & Stephen, 1995). Recent studies have demonstrated that heterogeneous photocatalysis is the most efficient technique in the degradation of colored chemicals(Li et al., 2003; Vione et al., 2003; Antharjanam et al., 2003; Fernandez-Ibanez et al., 2003; Liu et al., 2003; Ohno, 2004; Chen et al., 2004; Alkhateeb et al., 2005 & Attia et al., 2008). These studies used titanium dioxide and / or zinc oxide in the photolysis processes. The large bang gap of titanium dioxide and zinc oxide (~ 3.2 eV) put a limitation of using these semiconductors in photocatalytic degradation under natural weathering conditions. Only a small part of the overall solar intensity could be useful in such photodegradation processes. However, the existence of dye on the surface of catalyst reduces the energy required for excitation and then increases the efficiency of the excitation process by extending its absorption in the visible region of the spectrum.

Photocatalytic Degradation of Anthracene in Closed System Reactor

Polycyclic aromatic hydrocarbons (PAHs) represent a large class of persistent organic pollutants in an environment of special concern because they have carcinogenic and mutagenic activity. In this paper, we focus on and discuss the effect of different parameters, for instance, initial concentration of Anthracene, temperature, and light intensity, on the degradation rate. These parameters were adjusted at pH 6.8 in the presence of the semiconductor materials (TiO2) as photocatalysts over UV light. The main product of Anthracene photodegradation is 9,10-Anthraquinone which isidentified and compared with the standard compound by GC-MS. Our results indicate that the optimum conditions for the best rate of degradation are 25 ppm concentration of Anthracene, regulating the reaction vessel at 308.15 K and 2.5 mW/cm2 of light intensity at 175 mg/100 mL of titanium dioxide (P25).

Comparison between Solar and Artificial Photocatalytic Decolorization of Textile Industrial Wastewater

The photocatalytic decolorization of industrial wastewater was investigated by using TiO2 and ZnO photocatalysts. Heterogeneous photocatalytic processes applied under natural weathering conditions, in the presence of solar radiation show a promising degradation capability. The complete removal of color could be achieved in a relatively short time of about 20 minutes, when ZnO was used and about 100 minutes when TiO2 was used under solar irradiation. However, in the presence of artificial UV-light, complete decolorization of textile industrial wastewater was obtained after less than one hour of irradiation when ZnO was used and in less than two hours, when TiO2 was used at the same temperature. The results indicate that the degree of photocatalytic decolorization of textile industrial wastewater was obviously affected by different parameters. These parameters include catalyst mass, type of catalyst, type of reactor, type of dye, dye concentration, and temperature. The procedure used in this research can be used as an efficient technology for solar photocatalytic decolorization of the colored wastewater discharged from the textile industry under the climatic conditions of most countries.