Electrochemical oxidation of textile dye indigo

Electrochemical methods are being used increasingly as an alternative treatment process for the remediation of textile wastewaters. This study focused mainly on the colour removal and chemical oxygen demand (COD) reduction of vat textile dye (CI Vat Blue 1: indigo) from its aqueous solution by electrochemical oxidation. The process was carried out in a batch‐type divided electrolytic cell under constant potential using a Pt cage as anode and Pt foil as cathode. Operating variables such as supporting electrolyte, pH, ultrasonification and treatment time were investigated to probe their effects on the efficiency of the electrochemical treatment. Colour removal was estimated by monitoring the disappearance of the absorbance peak at 681.5 nm. It was found that in acidic conditions the electrolysis was more efficient. At pH 1, an NaCl concentration of 0.24 mol dm^?3, a dyeing solution concentration of 0.1% (w/v) and a period of 90 min of electrolysis, there was almost 100% colour removal and 60% reduction in COD. Voltammetric and IR investigations demonstrated that partial degradation of dye was achieved. The experimental results indicate that this electrochemical method could effectively be used as a pretreatment stage before conventional treatment. Copyright © 2005 Society of Chemical Industry     

Photoinduced electron transfer-catalyzed processes of sulfoamino perylene diimide under concentrated sun light

A new water-soluble perylene diimide derivative, N,N′-bis(12-sulfoaminododecyl)-3,4,9,10-perylenetetracarboxdiimide (SULFAPER), has been synthesized and characterized by visible, fluorescence, IR, ¹H and ¹³C NMR, mass, CV and time resolved measurements. Its photophysical properties in aqueous and organic solutions have been described. The singlet energy levels of the synthesized compound have been found to be 57.8 kcal/mol and 59.2 kcal/mol in aqueous and methanol solution, respectively. The LUMO energy level of SULFAPER has been determined by solid state cyclic voltammetry, and found to be −3.60 eV. SULFAPER undergoes two electron reduction process (−0.64 V and −0.42 V) versus ferrocene. SULFAPER has an energy band gap of 2.56 eV. The absorption maximum of the synthesized compound gives bathochromic shift of 12 nm in water with respect to its visible spectrum in methanol solution. The fluorescence quantum yields of the compound are low both in water and methanol solution because of the aggregation effect. Time-resolved fluorescence measurements have showed that the fluorescence decay times of the SULFAPER are τ₁ = 4.1 ns and τ₂ = 0.8 ns in water, and τ₁ = 4.0 ns and τ₂ = 2.5 ns in methanol solutions. The aqueous solution of SULFAPER is stable under UV–VIS irradiation, but a slight loss of fluorescence emission (25%) has been detected at a rate of k_p = 6.3 × 10⁻⁵ s⁻¹ in methanol solution, which might be the result of either the quenching of fluorescence emission by reactive oxygen species, or by enhanced aggregation effect. SULFAPER-sensitized photooxidations of (E)-cinnamic acid and methyl acrylate have been found to give selective photoproduct formations under concentrated sun light in organic phase. (E)-cinnamic acid has been seen to favor photochemical E–Z isomerization and methyl acrylate has been seen to favor the formation of methyl 2-oxopropanoate. The quantum yield of (E)-cinnamic acid (Φ_CA) under concentrated solar irradiation process has been calculated to be about 0.015, by the employment of an actinometry method developed by Erten and Icli.     

Modeling Milk Clotting Activity in the Continuous Production of Microbial Rennet from Mucor miehei

Production of microbial rennet, a milk clotting enzyme, from a commercial strain of Mucor miehei (NRRL 3420) was investigated in a continuously fed fermenter system for prolonged periods. The spherical film-wise growth of the culture has been accomplished and the effects of medium pH, mixing and dilution rates, and feed of D-glucose concentration on milk clotting activity was investigated. In model simulation studies, maximum milk clotting activity was generated from a multiple linear function. This was expressed in terms of fermentation medium pH, D-glucose, dissolved oxygen concentrations and dilution rate at the time of maximum milk clotting activity.     

Multistage storage- and entropy-constrained tree-structured vectorquantization

This paper proposes a new algorithm for the design of a tree-structured vector quantizer that operates under storage and entropy constraints; hence, it is called the storage- and entropy-constrained tree-structured vector quantizer (SECTSVQ). The algorithm uses the tree-growing approach and designs the tree one stage/layer at a time. The constraints on the rate and storage size, i.e., the number of nodes or codewords, at each stage are specified prior to the design procedure. While growing the tree, at each stage the algorithm optimally allocates the rate and the number of nodes available for the current stage to the nodes of the previous stage using the dynamic programming technique. The nodes of the current stage are then determined based on the allocations. In addition to being useful as a tree-structured VQ, SECTSVQ is particularly suited for application in progressive transmission. Moreover, the optimal allocation technique used in the design can be effectively applied to other optimal resource allocation problems. The SECTSVQ algorithm is implemented for various sources and is shown to compare favorably with other VQs     

Radiation protection for accompanying person and radiation workers in PET/CT

The purposes of the present study are to measure the total radiation doses for the radiation workers and for the accompanying person to the patients in positron emission tomography (PET)/computed tomography (CT) imaging. Urines samples from the patients were collected at 43, 62, 87, 117, 238, 362 min after the 555-MBq (18)flour-fluorodeoxyglucose ((18)F-FDG) injection and activities were measured. Dose rates were recorded using a Geiger-Muller counter and the total radiation doses were measured with using an electronic personnel dosemeter. According to the results here, 18.4 % of (18)F-FDG was excreted in the urine in 117 min after injection. At 117th min after injection, dose rates were determined as 345, 220, 140, 50 and 15 μSv h(-1), at proposed distances. The radiation doses after 117 min were measured as 3.92 mSv at 0.1 m, 2.11 mSv at 0.25 m and 1.08 mSv at 0.5 m. In conclusion, radiation protection will be sufficient within 2 h after (18)F-FDG injection for PET/CT imaging in daily practice.     

Effect of side chain substituents on the electron injection abilities of unsymmetrical perylene diimide dyes

Three near-infrared (NIR) absorbing unsymmetrical perylene diimide D-A-D type dyes containing 6-undecanoxy as donor group were utilized in dye-sensitized nanocrystalline TiO₂ solar cells. Structure of the acceptor side of the molecules were improved by adding 4-[2-methyl-5-(cyanoacrylic acid)-3-thienyl]-phenyl (V), 3-carboxy-2-pyridil (VI) and 3-carboxy-2-pyrazyl (VII) moieties attached to one of the N-side of the dye. The relationship between the molecular structure of the acceptor sites of the dyes and the photovoltaic performances were discussed. Electrochemical measurements indicated that band gaps of the dyes were energetically favorable for electron injection from the excited state of the dyes to the conduction band of TiO₂ nanoparticles. However, three dyes gave lower conversion efficiency on DSSC applications. Strong electron-withdrawing nature of perylene core might not permit to transfer the photo-generated electrons to the carboxyl groups anchoring to TiO₂ surface, and then solar-to-electricity conversion efficiencies of the dyes were reduced.     

Electrostatic energy harvesting by droplet-based multi-phase microfluidics

This paper presents an energy scavenging technique, merging microfluidics with electrostatic energy harvesting. The method employs droplet-based microflow of two phases with different electrical permittivities, resulting in a capacitance change across the microchannel, to harvest electrical energy. The technique is implemented on 3?mm wide, 1?mm deep minichannels. It is shown that 0.4?nW can be harvested using a single electrode pair, with air and water as the two phases flowing at 1?ml/min. The generated power can be increased significantly by microscale implementation, where the number of electrodes can also be increased for further improvement.     

Penetrating Sealants for Concrete Bridge Decks—Selection Procedure

The major parameter controlling the effectiveness of penetrating sealants as a means of protecting concrete bridge deck surface is the depth of penetration. The factors affecting the depth of sealant penetration are identified both through a fundamental approach and with reference to the literature on penetrating sealants, concrete deterioration, durability, and permeability. Penetration properties and the use of silane and siloxane as concrete surface sealers are discussed. The effects of surface cleaning methods and the drying period are discussed. Penetrating sealants are effective if proper surface cleaning and application procedures are employed. However, moisture state within the first 6-mm depth controls the depth of sealant penetration. Thus, the factors that affect the drying period before sealant application are identified. Penetrating sealants selection procedure incorporating available test methods is outlined based on the knowledge gained through the fundamental studies of flow phenomenon and literature.