High temperature liquid chromatography of triazole fungicides on polybutadiene-coated zirconia stationary phase

High temperature liquid chromatography using water-rich and superheated water eluent is evaluated as a new approach for the separation of selected triazole fungicides, hexaconazole, tebuconazole, propiconazole, and difenoconazole. Using a polybutadiene-coated zirconia column at temperatures of 100–150 oC, clear separations were achieved when 100% purified water was utilized as organic-free eluent. Excellent limits of detection down to pg level were obtained for the separation of the triazole fungicides under optimum conditions. Van’t Hoff plots for the separations were linear suggesting that no changes occurred in the retention mechanism over the temperature range studied

Magnetic graphene oxide as adsorbent for the removal of lead(II) from water samples

Magnetic Fe3O4 nanoparticles were prepared on graphene oxide (Fe3O4/GO) in situ in a one step process. The obtained Fe3O4/GO was used as an adsorbent for the removal for Pb(II) from environmental water samples prior to flame atomic absorption spectroscopy measurement. The adsorption procedure was optimized as follows: 60 min adsorption time, 50 mL sample volume, solution pH 4.5, and 25 mg adsorbent dosage. Under the optimum conditions, the adsorption efficiency obtained was greater than 75% (C = 50 mg L-1). The adsorption isotherm of Fe3O4@GO magnetic adsorbent was studied for Pb(II) adsorption using two isotherm adsorption models namely Langmuir and Freundlich. The adsorption isotherm data fits well with Langmuir isotherm (R2 = 0.9988) rather than with Freundlich isotherm. The maximum adsorption capacity (qm) obtained was 86.2 mg g-1. The results signified that the prepared Fe3O4/GO nanocomposite has a great adsorptive ability towards the Pb(II) from environmental water samples

Influence of sulfate and chloride on the mechanical properties of fired clay masonry wall

This paper presents the influence of aggressive environment on the mechanical properties of masonry systems. The investigation involved the measurement of strength and modulus of elasticity of single leaf brick masonry wall which were built from fired clay bricks in conjunction with designation (iii) mortar with proportions of 1: 1: 6 (OPC: lime: sand). After being constructed, the specimens were cured under polythene sheet for 14 days in a controlled environment room with 80 ± 5% relative humidity and temperature of 25 ± 2ºC. The specimens were then exposed to the solution containing sodium sulfate and sodium chloride. The strength and modulus of elasticity of the brickworks were determined at the ages of 28, 56 and 180 days. The strength and modulus of elasticity of the brickworks, unbonded bricks, and mortar prisms were determined at the ages of 28, 56 and 180 days to quantify the contribution of bricks and mortar on the deformation of the masonry walls. As a result, fired clay brickwork is not durable and deteriorate in the environment containing sodium sulfate but durable in sodium chloride. The deterioration of the brickwork clearly influenced by the deterioration of mortar joint. The present of sodium chloride also retarding the attack of sodium sulphate

Performance of RHA Cement Concrete under Marine Environment via Wetting and Drying Cyclic by Rapid Migration Test

In this research, the performance of concrete containing rice husk ash (RHA) under marine environment through wetting and drying cycles was investigated. Five levels of cement replacement (0%, 10%, 20%, 30% and 40% by weight) were used. The total cementitious content used was 420 kg/m3. A water/binder ratio of 0.49 was used to produce concrete having a target compressive strength of 40MPa at the age of 28 days. The performance of blended cement concrete under marine environment was evaluated using rapid migration test (RMT).  The results clearly showed that RHA can be satisfactorily used as a cement replacement material in order to reduce the chloride penetration depth and hence increases the durability of concrete. Generally, the chloride penetration depth of concrete containing higher RHA replacement is decreased as the RHA replacement increases, resulting in concrete with higher resistance to seawater attack

Magnetic graphene sol-gel hybrid as clean-up adsorbent for acrylamide analysis in food samples prior to GC-MS

Graphene (G) modified with magnetite (Fe3O4) and sol–gel hybrid tetraethoxysilane-methyltrimethoxysilane (TEOS-MTMOS) was used as a clean-up adsorbent in magnetic solid phase extraction (MSPE) for direct determination of acrylamide in various food samples prior to gas chromatography-mass spectrometry analysis. Good linearity (R2 = 0.9990) was achieved for all samples using matrix-matched calibration. The limit of detection (LOD = 3 × SD/m) obtained was 0.061–2.89 µg kg-1 for the studied food samples. Native acrylamide was found to be highest in fried potato with bright-fleshed (900.81 µg kg-1) and lowest in toasted bread (5.02 µg kg-1). High acrylamide relative recovery (RR = 82.7–105.2%) of acrylamide was obtained for spiked (5 and 50 µg kg-1) food samples. The Fe3O4@G-TEOS-MTMOS is reusable up to 7 times as a clean-up adsorbent with good recovery (>85%). The presence of native acrylamide was confirmed by mass analysis at m/z = 71 ([C3H5NO]+) and m/z = 55 ([C3H3O]+)

Engineering Properties of Normal Concrete Grade 40 Containing Rice Husk Ash at Different Grinding Times

The effect of rice husk ash produced at different grinding times on the engineering properties of concrete was studied. Eight rice husk ashes representing different grinding times were used in this investigation. Rice husk ash (RHA) was used to partially replace Portland cement Type I at 15% by weight of cementitious material. The compressive strength of concrete was designed to achieve grade 40 N/mm2 at 28 days. A super plasticizer was added to all mixes to provide workability in the range of 110-120 mm. However, the water to cement ratio (w/c) of the concrete was maintained at 0.49. Based on the results, the morphology of the rice husk ashes was changed by grinding. Optimum grinding time appeared to be approximately 90 minutes, during which time the compressive strength increased significantly. Generally, incorporation of RHA at various grinding times can dramatically decrease or increase the engineering properties of concrete

Diffusion coefficients of trivalent rare earth/actinide ions in acid and alkaline aqueous solutions

Leaching is one of the key process of rare earth (RE) element recovery. This paper was set out to validate the effectiveness of acid/alkali in RE leaching by measuring the limiting ionic conductivity (λo), self-diffusion coefficient (Di) and overall diffusion coefficient (DAB) to obtain a clear insight on the transport properties of ions and salts in aqueous solution. The calculation diffusivity of Di which is diffuse individual ions in pure water and DAB diffuse in chemical reagents were determined using Nernst-Haskell equation, applicable for 25°C. The results of D i were found to be consistent with experimental data from the literature where most of calculation and experiment data are less than 5% error. The final outcome had managed to confirm that NaOH is best reagent for most RE element leaching, which suits the common practice of the industry

Strength of porous concrete pavement at different curing methods

Porous concrete pavement has been used in some countries as a solution to environmental problems. Contrary to conventional concrete pavement, there is still lack of knowledge in some areas of production and performance of porous concrete pavement. One of the issue concern is curing conditions. These greatly affect the performance of porous concrete pavement. This paper elaborates the experimental results examining the influence of curing method and makes a comparison between five different curing methods on the strength of porous concrete pavement specimens. The properties analyzed include compressive strength, tensile splitting strength and flexural strength. The experimental results indicate that the different curing methods give a different effect to concrete strength. Based on the results obtained in this experiment, curing method by using polyethylene bag promise a good result and better performance to porous concrete pavement specimen strength

Performance of macro clay on the porous asphalt mixture properties

Porous asphalt pavement already well known as one type of pavement since many decades, however due to lack in strength it is not been widely used in road construction especially in high stresses areas. Many research had been conducted by researchers in order to improve the durability and increase the service life of the road. One of the methods that commonly used is through asphalt modification. Objectives of this study are to discuss influence of macro-clay in terms of physical and rheological properties and their effect on performance of porous asphalt mixture. Various percentage of macro-clay (starting from 2% to 8%) was blended in an asphalt binder and compacted using the Marshall compactor. The blended asphalt was characterized using penetration, softening point test and penetration index compared with unmodified binder. Performance tests of asphalt mixture were carried out such as Los Angeles Abrasion Value (LAAV) and Stability and Flow test in order to determine the strength and durability. The results show that the addition of macro-clay would increase in softening point but decrease in binder penetration. Based on the results, while macro-clay changes physical and rheological properties of bitumen and increase stiffness, it also improves strength and durability resistance, as well. Generally, the best improvements in the modified binders were obtained with 4% of macro-clay

Graphene-chitin bio-composite polymer based mode locker at 2 micron region

In the field of pulsed fiber laser, graphene is a well-known two-dimensional (2D) material for its excellent optical properties. An alternative approach to the existing method, graphene based filament originally intended for 3-dimensional (3D) printing was used as starting material. Coupled with a newly introduced chitin nanofiber as the host polymer, it was demonstrated and reported as passive mode locker at 2-micron region. The conventional soliton operated at operating wavelength of 1982.7 nm with repetition rate of 11.35 MHz. The produced average output power, pulse width, time-bandwidth product (TBP) and signal to noise ratio (SNR) was 76.83 µW, 1.88 ps (HAC200), 0.416 and 43 dB, respectively. When the pulse was amplified with 5.4 dB of Thulium doped fiber amplifier (TDFA), the average output power increased to 3.43 mW and produced a broad operating wavelength around the 2-micron region. At the same repetition rate of 11.35 MHz, the measured pulse width, SNR, pulse energy and peak power of 7.033 ps (pulseCheck 150), 42.0 dB, 0.30 nJ, and 42.98 W, are obtained, respectively. High power laser operation in this region can find applications in medical field and sensors technology