Single-pass Conditions Research Articles

Highly efficient ZnO photocatalytic foam reactors for micropollutant degradation

The efficient removal of organic micropollutants, pharmaceuticals, pesticides, drugs, and others, remains an unsolved challenge in water treatment. Although photocatalysis has proven highly effective at degrading these substances, its large-scale implementation has been so far hampered by technical and economic concerns. This work describes the development and characterization of novel highly efficient, self-supporting photocatalytic ZnO foams for the degradation of organic micropollutants. A systematic investigation of flow rate, catalyst length and stability under both recirculating and single-pass conditions was conducted using carbamazepine as a UV-recalcitrant model pollutant. Under recirculation, 95 % degradation was achieved with photocatalyst quantum yield of 1.2 × 10−3 and electrical energy per order (EEO) as low as 24 kWh m−3, values outperforming current technology, slurry and immobilised systems. For single-pass tests, complete degradation was achieved in 30 min, with the quantum yield increasing to 6.3 × 10−3, and an EEO of 36 kWh m−3. These values also outperform those for slurries, immobilised and other foam photocatalyst reported in the literature under similar conditions. The low energy consumption of these newly developed photocatalytic foams, combined with their high quantum yield and stability, provides a realistic path towards practical implementation of photocatalytic processes in water treatment, addressing the limitations of existing slurry and immobilised photocatalytic technology.

Statistics of pulse enrgy fluctuations in a solid-state Raman laser

In this paper, we present the results of the study of the statistics of pulse energy fluctuations in a Raman laser under optical pump by the multimode nanosecond pulses. A system of coupled differential equations for slowly varying envelopes of the pump field and first three Stokes lines was integrated numerically with taking into account spatial inhomogeneity of the pump beam, spontaneous noise, and optical feedback. Data of the numerical simulation revealed a sharp increase in the fluctuation amplitude in the nonlinear regime of Raman frequency conversion when the optical length of the Raman cavity was matched with the cavity length of the multimode pump laser. At a mean 1st Stokes conversion efficiency of 3.5–3.8 %, the calculations showed an increase in the coefficient of variation (CV) of a random value from 9 % to 118 %. In the linear regime of Raman frequency conversion, when the conversion efficiency was 0.2–0.03 %, a further increase in the CV value up to 270–500 % was predicted. It is also numerically shown that the fluctuation statistics under the conditions of the cavity length matching is essentially non-Gaussian and described by the L-type probability density distributions (PDDs) with long tails and maxima located near zero. The numerical data were quantitatively confirmed by an experiment for a Raman laser on a barium nitrate crystal operated near the Raman threshold, when the 1st Stokes conversion efficiency did not exceed 0.3 %. A Raman cavity was formed by two flat mirrors providing a double-pass pump configuration. The Raman laser was excited by the linearly polarized frequency-doubled radiation of a Q-switched Nd:YAG laser generating multimode pulses with a duration of 7–8 ns. A Raman laser operating regime characterized by the hyperexponential PDDs with CVs reaching 480 %, which is 2–2.5 times higher than those observed earlier for the single-pass conditions of stimulated Raman scattering, was realized.

Exploration of potential of Zylon and Aramid fibers to enhance the abrasive wear performance of polymers

Two series of composites based on two types of high performance fibers (aramid and liquid-crystalline polyoxazole) were developed by using two different base matrices viz. Polyetherimide (PEI) and Ultra-high-molecular-weight-polyethylene (UHMWPE). PEI based composites reinforced with fabrics of Zylon (liquid-crystalline polyoxazole) and Kevlar-49 (aramid) were developed by using an impregnation technique, while UHMWPE composite reinforced with fibers of Twaron (aramid) was developed by a novel co-mingling technique. These composites were evaluated for their abrasive wear performance under various loads and orientations against Silicon Carbide (SiC) abrasive paper in a single pass condition. These fabric reinforcements enhanced the abrasive wear performance up to 50% when the fabric was oriented normal to the sliding surface. However, the wear performance deteriorated when the fabric was oriented parallel to the sliding surface. Zylon fabric proved to be the most beneficial in maximizing the wear resistance of PEI matrix. These results were supported by the SEM studies done to understand the various possible wear mechanisms.

Efeito do Pré-aquecimento e de Único e Múltiplos Passes no Grau de Porosidade, Oxidação e Microdureza de um Revestimento de Aço Inoxidável Duplex Depositado por Aspersão Térmica Chama Arame

Resumo: Este trabalho tem como objetivo estudar o efeito do pré-aquecimento e de único e múltiplos passes no grau de porosidade, oxidação e microdureza no processo de revestimento obtido por aspersão térmica chama arame. A oxidação ao ar de partículas aspergidas após ancoragem afeta o desempenho para o aço inoxidável duplex AF2209 depositado por aspersão térmica chama arame em substrato de aço estrutural pré-aquecido com maçarico à diferentes temperaturas. O percentual de óxidos e poros foram medidos e quantificados por microscopia óptica com auxilio de software de análise de imagem. Imagens por MEV e a dureza Vickers dos óxidos e panquecas indicam que a oxidação aumenta com o pré-aquecimento e com a deposição de múltiplos passes. Os resultados indicam que maiores pré-aquecimentos e a deposição de múltiplos passes reduzem a fragmentação das partículas, mas aumenta a quantidade de óxidos. Observa-se também que o reaquecimento da camada reduz a microdureza Vickers média dos óxidos e panquecas da condição de único passe para a condição de múltiplos passes.

Assessment of potential of nano and micro-sized boron carbide particles to enhance the abrasive wear resistance of UHMWPE

Abstract Two series of UHMWPE composites were developed using boron carbide (B4C) particles in different amounts and sizes. Micro-series contained micro B4C particles (2–5 μm) in various wt% (0, 2, 4, 6, 8 and 10) while nano-series contained nano-particles (NPs) of size 70–90 nm in 0, 2 and 3%. Abrasive wear studies against silicon carbide (SiC) paper in a single pass condition were conducted under varying loads and speeds. Inclusion of B4C particles proved beneficial to enhance the wear resistance and optimum amounts of filler for micro and nano-series were ≈ 6–8% and 3% respectively. Scratch hardness showed fairly good linearity with the wear resistance. SEM studies confirmed that inclusion of hard fillers mainly reduced the severity of micro-cutting mechanism and hence wear.

TiO2-Impregnated Porous Silica Tube and Its Application for Compact Air- and Water-Purification Units

A simple, convenient, reusable, and inexpensive air- and water-purification unit including a one-end sealed porous amorphous-silica (a-silica) tube coated with TiO2 photocatalyst layers has been developed. The porous a-silica layers were formed through outside vapor deposition (OVD). TiO2 photocatalyst layers were formed through impregnation and calcination onto a-silica layers. The resulting porous TiO2-impregnated a-silica tubes were evaluated for air-purification capacity using an acetaldehyde gas decomposition test. The tube (8.5 mm e.d. × 150 mm) demonstrated a 93% removal rate for high concentrations (ca. 300 ppm) of acetaldehyde gas at a single-pass condition with a 250 mL/min flow rate under UV irradiation. The tube also demonstrated a water purification capacity at a rate 2.0 times higher than a-silica tube without TiO2 impregnation. Therefore, the tubes have a great potential for developing compact and in-line VOC removal and water-purification units.

Field performance test of an air-cleaner with photocatalysis-plasma synergistic reactors for practical and long-term use.

A practical and long-term usable air-cleaner based on the synergy of photocatalysis and plasma treatments has been developed. A field test of the air-cleaner was carried out in an office smoking room. The results were compared to previously reported laboratory test results. Even after a treatment of 12,000 cigarettes-worth of tobacco smoke, the air-cleaner maintained high-level air-purification activity (98.9% ± 0.1% and 88% ± 1% removal of the total suspended particulate (TSP) and total volatile organic compound (TVOC) concentrations, respectively) at single-pass conditions. Although the removal ratio of TSP concentrations was 98.6% ± 0.2%, the ratio of TVOC concentrations was 43.8% after a treatment of 21,900 cigarettes-worth of tobacco smoke in the field test. These results indicate the importance of suitable maintenance of the reactors in the air-cleaner during field use.

Influence of graphite filler on two-body abrasive wear behaviour of carbon fabric reinforced epoxy composites

The influence of graphite filler additions on two-body abrasive wear behaviour of compression moulded carbon–epoxy (C–E) composites have been evaluated using reciprocating wear unit and pin-on-disc wear unit under single pass and multi-pass conditions respectively. The carbon fabric used in the present study is a plain one; each warp fiber pass alternately under and over each weft fiber. The fabric is symmetrical, with good stability and reasonable porosity. Abrasive wear studies were carried out under different loads/abrading distance using different grades of SiC abrasive paper (150 and 320 grit size). Graphite filler in C–E reduced the specific wear rate. Further, the wear volume loss drops significantly with increase in graphite content. Comparative wear performance of all the composites showed higher specific wear rate in two-body wear (single-pass conditions) compared to multi-pass conditions. Further, the tribo-performance of C–E indicated that the graphite filler inclusion resulted in enhancement of wear behaviour significantly. Wear mechanisms were suggested and strongly supported by worn surface morphology using scanning electron microscopy.

All-solid-state ultraviolet laser based on frequency doubling in an external ring cavity

An all-solid-state ultraviolet laser based on frequency doubling in an external ring cavity with low input pump power is reported. Both second harmonic generation (SHG) and fourth harmonic generation (FHG) occurred in an external three-mirrors ring cavity. The need for impedance matching of this cavity to the input radiation was eliminated and the cavity adaptation was simplified, because the mirrors were not highly reflecting at 1064 nm and the cavity resonates only at 532 nm. Experiment results demonstrate that the conversion efficiency of this external cavity is higher than that of the single-pass condition.

Laboratory Studies of Electrochemical Treatment of Industrial Azo Dye Effluent

Removal of color and reduction of chemical oxygen demand (COD) in an industrial azo dye effluent containing chiefly reactive dyes were investigated under single-pass conditions at a dimensionally stable anode (DSA) in a thin electrochemical flow reactor at different current densities, flow rates, and dilutions. With 50% diluted effluent, decolorization was achieved up to 85-99% at 10-40 mA/ cm2 at 5 mL/min flow rate and 50-88% at 30-40 mA/ cm2 at high (10-15 mL/min) flow rates. The COD reduction was maximum (81%) at 39.9 mA/cm2 or above when solution-electrode contact time (Ct) was as high as 21.7 s/cm2 and decreased as Ct declined at a given current density. Cyclic voltammetric studies suggesting an indirect oxidation of dye molecules over the anode surface were carried out at a glassy carbon electrode. The effect of pH on decolorization and COD reduction was determined. An electrochemical mechanism mediated by OCl- operating in the decolorization and COD reduction processes was suggested. The effluent was further treated with NaOCI. The oxidized products from the treated effluents were isolated and confirmed to be free from chlorine-substituted products by IR spectroscopy. From the apparent pseudo-first-order rate data, the second-order rate coefficients were evaluated to be 2.9 M(-1) s(-1) at 5 mL/ min, 76.2 M(-1) s(-1) at 10 mL/min, and 156.1 M(-1) s(-1) at 15 mL/ min for color removal, and 1.19 M(-1) s(-1) at 5 mL/min, 1.79 M(-1) s(-1) at 10 mL/min, and 3.57 M(-1) s(-1) at 15 mL/min for COD reduction. Field studies were also carried out with a pilot-scale cell at the source of effluent generation of different plants corresponding to the industry. Decolorization was achieved to about 94-99% with azo dye effluents at 0.7-1.0 L/min flow costing around Indian Rupees 0.02-0.04 per liter, and to about 54-75% in other related effluents at 0.3-1.0 L/min flow under single-pass conditions.

04/00176 Effect of filler-fiber interactions on compressive strength of fly ash and short-fiber epoxy composites: Kulkarni, S. M. Journal of Applied Polymer Science, 2003, 87, (5), 836–841

The influence of graphite filler additions on two-body abrasive wear behaviour of compression moulded carbon–epoxy (C–E) composites have been evaluated using reciprocating wear unit and pin-on-disc wear unit under single pass and multi-pass conditions respectively. The carbon fabric used in the present study is a plain one; each warp fiber pass alternately under and over each weft fiber. The fabric is symmetrical, with good stability and reasonable porosity. Abrasive wear studies were carried out under different loads/abrading distance using different grades of SiC abrasive paper (150 and 320 grit size). Graphite filler in C–E reduced the specific wear rate. Further, the wear volume loss drops significantly with increase in graphite content. Comparative wear performance of all the composites showed higher specific wear rate in two-body wear (single-pass conditions) compared to multi-pass conditions. Further, the tribo-performance of C–E indicated that the graphite filler inclusion resulted in enhancement of wear behaviour significantly. Wear mechanisms were suggested and strongly supported by worn surface morphology using scanning electron microscopy.

The Effect of Fibre Reinforcement and Solid Lubricants on Abrasive Wear Behavior of Polyetheretherketone Composites

The tribo performance evaluations were carried out for various composites of polyetheretherketone (PEEK) filled with short glass, carbon fibre, and solid lubricants in abrasive wear situation. Abrasive wear studies were carried out under single pass condition against SiC abrasive paper by using pin-on-disc machine. The influence of variables such as sliding distance, load and abrasive grit size has been investigated. It was observed that fibre reinforcement deteriorated the abrasive wear resistance of neat PEEK matrix. Combination of fibre and particulate filler is more detrimental to abrasive wear performance. Efforts were made to correlate the abrasive wear performance with the appropriate mechanical properties. Ratner-Lancaster plot showed linear correlation. SEM was used to analyse the worn surfaces of the samples.

Effect of solid lubricant and fibrous reinforcement on the abrasive wear of polyamides

AbstractShort glass fibre‐reinforced polyamide 6 and polyamide 11 (PA 6 and PA 11) with and without a solid lubricant of polytetrafluoroethylene and metal powders (e.g., bronze) and copper as fillers were formulated and characterised for their compositional and mechanical properties. A tribological evaluation of these composites' abrasive wear was carried out by abrading a polymer pin against 80 grade (175 um) silicon carbide (SiC) paper under single‐pass conditions at various loads. It was observed that the fibre reinforcement reduced the abrasive wear resistance of virgin polymers. A combination of fibre and particulate fillers was further detrimental in this respect. Efforts were made to correlate the wear performance with the ductility factor, fracture toughness, and fracture energy in the case of PA 6 and its composites.

Two-body and three-body abrasive wear behaviour of polyaryletherketone composites

Single and multipass two-body and three-body abrasive wear behaviour of various polyaryletherketone composites have been carried out by using a pin-on-disc machine and a rubber wheel abrasion test (RWAT) rig. Abrasive wear studies were conducted under different loads and sliding distances. Comparative wear performance of all the composites at different loads shows that specific wear rate ( K o) of two-body abrasive wear (single pass condition) is 30–50 times greater than three-body abrasive wear. Also, specific wear rate ( K o) of two-body abrasive wear (multipass condition) is 5–12 times greater than three-body abrasive wear. Efforts were made to correlate the abrasive wear performance with the appropriate mechanical properties. The operating wear mechanisms under different experimental condition have also been studied by using scanning electron microscopy.

Analysis of simultaneous influence of operating variables on abrasive wear of phenolic composites

The paper deals with the abrasive wear investigations on various composites of phenolic resin filled with alumina powder and abraded against silicon carbide paper under dry and single pass condition. The data analysis was done using orthogonal experimental design method. The objective was to study the influence of variables such as filler concentration, load, sliding speed and abrading particle size on the abrasive wear performance of phenol-formaldehyde-based composites. Regression analysis of the data was carried out to develop equations for the composites in which the wear volumes of the specimens were expressed in terms of simultaneous contribution from the influence of load, abrading particle size, sliding speed and their mutual interactions. It was confirmed that among these factors load was the factor contributing most strongly to the wear of these composites. Sliding speed seemed to have least effect on the wear performance in the selected operating conditions. Worn surfaces were studied by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) to have an insight into the wear mechanisms and particle dispersion in the bulk of the composites.

Influence of abrading particle size on the wear performance of various polyamides

AbstractVarious polyamides (PAs) containing different CONH2/CH2 ratios were selected for abrasive wear studies. Eleven types of silicon carbide (SiC) papers varying in particle size (10–175 μm) were selected as abrading counterfaces. The wear performance under single‐pass conditions indicated that the selected PAs did not show a size effect, in contrast to the case of metals and some other polymers. Wear rates were of the order of 2–17 × 10−11 m3/Nm. Scanning electron micrographs of some of the worn papers indicated correlations between wear and the size and number of wear debris particles and the amount of material transferred to the papers.

Abrasive wear performance of various polyamides

Polyamides (PAs) form a major class of tribo-polymers used in almost all types of wear situations. They excel most of the engineering polymers especially in the case of abrasive wear performance. Since methylene (CH 2) to amide (CONH) group ratio in PAs control the physical and mechanical properties, it was thought interesting to examine its influence on tribo-performance also. Hence, two types of PAs (addition and condensation) were selected for the present study. Abrasive wear studies on 10 PAs were done in a single pass condition by abrading a polymer pin against a waterproof silicon carbide (SiC) abrasive paper under various loads. It was observed that CH 2/CONH ratio had a significant influence on various mechanical properties such as tensile strength, elongation to break, fracture toughness, fracture energy and therefore, on the abrasive wear performance. It was observed that CH 2/CONH ratio and various mechanical properties when plotted individually did not show linear relation in most of the cases, while the specific wear rate as a function of some mechanical properties showed good correlation.

Metabolism of flupyrazofos in the isolated perfused rat liver.

To investigate the hepatic metabolism of the new insecticide flupyrazofos [O,O-diethyl O-(1-phenyl-3-trifluoromethylpyrazol-5-yl) phosphorothioate], isolated rat liver was perfused with flupyrazofos under single-pass conditions. In outflow perfusate and bile, 1-phenyl-3-trifluoromethyl-5-hydroxyprazole (PTMHP), PTMHP-sulfate and PTMHP-glucuronide conjugates were identified as the metabolites of flupyrazofos. However, O,O-diethyl O-(1-phenyl-3-trifluoromethylpyrazol-5-yl) phosphate (flupyrazofos oxon) was not detected. A HPLC method with UV detection was used to investigate the hepatic disposition of flupyrazofos and its metabolite PTMHP. The concentrations of flupyrazofos, PTMHP and PTMHP conjugates in outflow perfusate reached steady-state levels within 20 min after commencing perfusion of 7.3 microM flupyrazofos. At steady state, the mean extraction ratio of flupyrazofos was 0.93 (+/- 0.01) and clearance was 26.1 (+/- 0.2) ml min-1 which nearly approached perfusate flow rate (28 ml min-1). PTMHP accounted for 55.7 (+/- 5.8)% of eliminated flupyrazofos and was recovered as unchanged PTMHP, PTMHP-sulfate and PTMHP-glucuronide in the bile as well as the outflow perfusate.

Influence of fillers on abrasive wear of short glass fibre reinforced polyamide composites

Various composites of polyamide 6 filled with short glass fibre, polytetrafluoroethylene and metal powders viz. copper and bronze were formulated in the laboratory and characterised for their various mechanical properties such as tensile strength, tensile elongation, flexural strength, hardness and impact strength. Compositional analysis was done with gravimetry, solvent extraction and differential scanning calorimetry (DSC) techniques followed by tribo-performance evaluation in abrasive wear mode by abrading a sample against silicon carbide (SiC) abrasive paper in a single pass condition under various loads. It was observed that the fibre reinforcement deteriorated the abrasive wear resistance of virgin polymer. Combination of fibre and particulate filler was more detrimental in this respect. Efforts were made to correlate the wear performance with the appropriate mechanical properties. Under selected loading condition, wear as a function of product of hardness, elongation to break (e) and ultimate tensile strength (S) showed better correlation than Ranter-Lancaster plot. Scanning electron microscopy (SEM) was used to analyse the worn surfaces of the samples.

Improved recovery of insulin-like growth factors (IGFs) from bovine colostrum using alkaline diafiltration.

Studies to develop a rapid, bioprocess-compatible method to recover low-molecular-mass growth factors from bovine colostrum are reported. Defatted bovine colostrum was subjected to tangential-flow filtration (TFF) using two different filters [polyether sulphone (PES) and regenerated cellulose (RC)] at pH 5.8, pH 8.0 and pH 8.0+0. 01 M NaCl. Single-pass TFF at pH 5.8 using a 100 kDa RC filter resulted in the loss of approx. 90% of insulin-like growth factor I (IGF-I) to non-specific filter adsorption. Comparison of 30 kDa RC and PES filters under single-pass conditions showed that yields of IGF-1 and IGF-II were highest with RC filters. Yields of IGF-I and protein from both filter types were increased at pH 8.0 and were greatest for the 30 kDa RC filter. Effects of adding large diluent volumes continuously during TFF (diafiltration) were tested at pH 5. 0 and 8.0. The use of 10 diafiltrate vols. at pH 8.0 resulted in the recovery of 15-28% of colostral IGF-1 from the RC 30 kDa permeates, 2-4-fold greater than under acidic conditions. Yields of IGF-II (39.6%) were unaffected by pH and at least 97% of total protein was retained by the 30 kDa filter at pH 8.0. Denaturing SDS/PAGE analysis of the alkaline RC 30 kDa permeates demonstrated two major regions of stained proteins at 10-13 kDa and 17-19 kDa. Acidic TFF permeates contained additional stained proteins at approximately 90, 48 and 37 kDa. Isoelectric focusing of these samples demonstrated the presence of proteins with isoelectric points of 8.2 and 8.6. The current study demonstrates a one-step bioprocess-compatible technique for the recovery of low-molecular-mass polypeptides from bovine colostrum. By using alkaline diafiltration with RC filters TFF provided optimal recovery of IGF-1 from colostrum.