Photocatalytic degradation of carbofuran using semiconductor oxides

The photocatalytic degradation of carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate) was investigated in an aqueous solution using Degussa P-25 TiO2 and ZnO as photocatalysts. The progress of degradation was monitored using TOC analyzer, HPLC, GC-MS and UV-vis spectrophotometer. The effects of various experimental parameters such as initial concentration of carbofuran, pH of the solution, catalyst loading and light intensity were systematically studied in order to achieve maximum degradation efficiency. The complete mineralization of carbofuran was confirmed by TOC analyzer. The degradation with ZnO showed less efficiency than TiO2. The formation of NO(3)(-) was identified and quantified using HPLC. In addition, four different intermediates formed during the degradation process were also identified and characterized by GC-MS. The mineralization rate was compared with lamps of wavelength 254 and 365 nm under similar conditions. The rate with 254 nm was observed to be very close to that of 365 nm.     

Areca leaves as a source of carbon: Preliminary investigation as catalyst support for electrolytic hydrogen evolution in acidic medium

Our work tends to establish Green Energy from Waste concept. Refuses/wastes can be a secondary resource for variety of materials which may find applications in domestic, industrial, medical, electronic and energy devices. We have attempted to produce activated carbon powders from a cheap waste namely biomass of areca leaves. The material has been exploited as catalyst support materials in H₂ production through water electrolysis. Catalyst powders of 10% Ni and 1% Pt by weight were supported on the carbon produced from the leaves using NaBH₄ reduction of the respective salts. Physical features of the catalyst powders were evaluated through PXRD, FTIR, density, SEM, surface area. Catalytic activity of the biocarbon supported catalyst powders was assessed by LSV & CV. The carbon produced may attract technological importance because carbon source selected is cheap and green. Further the activated carbon may find applications such as electrode materials, adsorbent for color, odor and hazardous pollutants.     

A functional monomer to synthesize sulfonated poly(ether ether ketone) with sulfonic acid group in the pendant side chain

A functional monomer which enables the synthesis of sulfonated poly(ether ether ketone) (SPEEK) polymer with the sulfonic acid group in the pendant side chain has been successfully developed. 1, 3‐propane sultone was used as the model compound to introduce the side chain moiety in the monomer. The above sulfonated monomer (0.50 mol) along with 4, 4′‐difluorobenzophenone (0.50 mol) were reacted with bisphenol‐A (1.0 mol) to obtain the SPEEK polymer with the sulfonic acid group in the pendant side chain. All the intermediates and the SPEEK polymer were characterized using ¹H‐NMR. The SPEEK polymer is expected to have improved mechanical and electrical properties for PEM fuel cell application. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of chemical structure of aromatic dianhydrides on the thermal, mechanical and electrical properties of their terpolyimides with 4,4′-oxydianiline

Aromatic terpolyimides were synthesized by the reaction of 3,3′,4,4′-oxydiphthalicdianhydride(ODPA), 3,3′,4,4′-biphenyldianhydride(BPDA) and 3,3′,4,4′-benzophenonetetracaboxylicdianhydride(BTDA) with 4,4′-oxydianiline(ODA) via thermal imidization with the view to enhance their tensile properties without compromising thermal properties compared to their homo and copolyimides. Their films were characterized by FTIR, TGA, DSC and XRD. Their FTIR spectra established formation of polyimide by the characteristic vibrations at 1375cm⁻¹(C-N stretch) and 1113 cm⁻¹(imide ring deformation). TGA results showed imidization of residual polyamide acid close to 250 °C and decomposition of polyimides at about 540 °C. XRD results showed amorphous nature for all terpolyimides. Their tensile strength and tensile modulus were higher than either homo or copolyimides. Incorporation of BPDA, without bridging groups between the aromatic rings into the backbone of ODPA/BTDA-ODA is suggested as the cause for such an enhancement. Such terpolyimide can find application as adhesives in making flexible single/multilayer polyimide metal-clad laminates in flexible printed circuits and tape automated bonding applications. In addition, the terpolyimide, BPDA/BTDA/ODPA-ODA (mole ratio 0.5:0.25:0.25:1), showed low dielectric constant (3.52) as BPDA could offer slight rigidity by which the orientation of polar groupings could be reduced.     

A study on fabrication of sulfonated poly(ether ether ketone)-based membrane-electrode assemblies for polymer electrolyte membrane fuel cells

The porosity effect of catalyst electrodes in membrane-electrode assemblies (MEAs) using a hydrocarbon-based polymer as electrolyte and ionomer was investigated on physical and electrochemical properties by varying the content of ionomer binder (dry condition) in the catalyst electrodes. The MEAs were compared with the Nafion^®-based MEA using Nafion^® 112 and 5 wt.% ionomer solution (EW = 1100) in terms of porosity values, scanning electron microscopic images, Nyquist plots, dielectric spectra and I–V polarization curves. In this study, sulfonated poly(ether ether ketone) (SPEEK) membranes with 25 ± 5 μm of thickness and 5 wt.% ionomer solutions have been prepared. The prepared membranes were characterized in terms of FT-IR, DSC and proton conductivity. Proton conductivity of the SPEEK membranes was compared with one of the Nafion^® membranes with relative humidity. The porosity of the catalyst electrodes was calculated using the properties of catalyst, ionomer solution and solvent. As a result, the performance of the new type polymer (i.e., SPEEK in this study)-based MEA with the similar membrane conductivity and porosity of the catalyst electrode in the Nafion^® MEA was similar to that of the Nafion^® MEA.     

Rotating ring-disc electrode (RRDE) investigation of borohydride electro-oxidation

Rotating ring-disc electrode (RRDE) voltammetry is applied for the in situ determination of hydroxy borohydride (BH₃(OH)⁻) formation during borohydride (BH₄⁻) electro-oxidation on a gold (Au) electrode in 6.0 M NaOH solution. The BH₃(OH)⁻ is detected at the ring electrode due to its further oxidation to BH₂(OH)₂⁻ by maintaining its potential in the range of −0.800 to −0.600 V vs. normal hydrogen electrode (NHE) while oxidizing BH₄⁻ on the disc electrode. The study reveals that the generation of BH₃(OH)⁻ increases if the anodic polarization of the disc electrode is increased. The RRDE ring-shielding experiments show that the electro-oxidation of BH₄⁻ occurs over a wide potential range of −0.500 to 0.400 V on the Au electrode under hydrodynamic conditions. Chronoamperometry is also used to study the BH₃(OH)⁻ oxidation in the potential range of −0.800 to −0.600 V with 0.33 M NaBH₄ in three different buffer solutions of pH 10.2, 11.0 and 11.70, respectively. The chronoamperometric studies indicate that the formation and stability of BH₃(OH)⁻ depends on the pH value.     

Simultaneous crystallization of calcium phosphate and calcium oxalate in the presence of ascorbic acid under physiological conditions

Ascorbic acid (AA—Vitamin C) plays a vital role in human body to preserve optimal health. However, high intake may cause the formation of pathological calcium oxalate stones. Calcium oxalate and calcium phosphates are the major crystalline constituents of the urinary calculi and commonly found together. The effect of AA on the crystallization of calcium phosphate was studied in gel matrix under physiological conditions. Calcium phosphates such as hydroxyapatite (HAp), brushite (DCPD) and calcium oxalate dihydrate (COD—Weddellite) were found to crystallize simultaneously in the gel matrix. The formation of HAp is accelerated by AA. A possible reaction scheme for the formation of COD by the metal induced conversion of AA is proposed.     

A visual package for educating preparatory transmission line series compensation

Transmission of electric power over great distances imposes very severe economical and technical limitations. Series compensation techniques are found to be very effective in overcoming such economical and technical limitations, especially transmission line compensation using series capacitors, which has gained special interest among researchers because of its cost effectiveness. This work provides two series compensation algorithms for a student and presents a user-friendly software package developed in Visual Basic for the study of transmission line series compensation.     

Liquid-Phase Cyclization of (Phenylthio)acetaldehyde Diethylacetal to Benzo[b]thiophene over Zn2+ Ion-Exchanged Zeolite BEA

Cyclization of (phenylthio)acetaldehyde diethylacetal was examined in 1,2-dichloroethane and chlorobenzene solvents in the presence of H-beta zeolite and Zn²⁺ ion-exchanged beta zeolite under reflux conditions. Zn²⁺ ion-exchanged beta zeolite showed better activity than its H-form counterpart owing to its higher Lewis acidity. The cyclization proceeds via two different pathways. At lower temperature the reaction proceeds predominantly via a pathway in which deacetalization of the reactant occurs first and then the resulting aldehyde cyclizes to benzo[b]thiophene.     

Automation of photoacoustic spectrometer using VEE Pro software

A photoacoustic spectrometer was developed and the instrument control programs were developed using Agilent VEE Pro virtual engineering software. The performance and validity of the spectrometer was rigorously tested for repeatability and standard error for samples like carbon black, glass and silicon wafers.