Removal of chromium (VI) from aqueous solution using treated oil palm fibre

This study proposed an oil palm by-product as a low-cost adsorbent for the removal of hexavalent chromium [Cr (VI)] from aqueous solution. Adsorption of Cr (VI) by sulphuric acid and heat-treated oil palm fibre was conducted using batch tests. The influence of pH, contact time, initial chromium concentration and adsorbent dosage on the removal of Cr (VI) from the solutions was investigated. The optimum initial pH for maximum uptake of Cr (VI) from aqueous solution was found to be 1.5. The removal efficiency was found to correlate with the initial Cr (VI) concentration, adsorbent dosage as well as the contact time between Cr (VI) and the adsorbent. The adsorption kinetics tested with pseudo first order and pseudo second order models yielded high R(2) values from 0.9254 to 0.9870 and from 0.9936 to 0.9998, respectively. The analysis of variance (ANOVA) showed significant difference between the R(2) values of the two models at 99% confidence level. The Freundlich isotherm (R(2)=0.8778) described Cr (VI) adsorption slightly better than the Langmuir isotherm (R(2)=0.8715). Difficulty in desorption of Cr (VI) suggests the suitability of treated oil palm fibre as a single-use adsorbent for Cr (VI) removal from aqueous solution.     

An Analytical Study on a Model Describing Heat Conduction in Rectangular Radial Fin with Temperature-Dependent Thermal Conductivity

The coupling of the homotopy perturbation method (HPM) and the variational iteration method (VIM) is a strong technique for solving higher dimensional initial boundary value problems. In this article, after a brief explanation of the mentioned method, the coupled techniques are applied to one-dimensional heat transfer in a rectangular radial fin with a temperature-dependent thermal conductivity to show the effectiveness and accuracy of the method in comparison with other methods. The graphical results show the best agreement of the three methods; however, the amount of calculations of each iteration for the combination of HPM and VIM was reduced markedly for multiple iterations. It was found that the variation of the dimensionless temperature strongly depends on the dimensionless small parameter ${\varepsilon_1}$ . Moreover, as the dimensionless length increases, the thermal conductivity of the fin decreases along the fin.     

Inverse radiation-conduction estimation of temperature-dependent emissivity using a combined method of genetic algorithmand conjugate gradient

The solution of an inverse, conduction-radiation problem in a two-dimensional rectangle is analyzed to determine the temperature-dependent emissivity at the boundary. The medium is gray, absorbing, emitting and isotropically scattering. The bounding surfaces are assumed to be opaque and diffuse. The inverse problem is solved by minimizing the performance function, which is expressed by the sum of square residuals between estimated and exact heat fluxes, using a combined method of genetic algorithm and conjugate gradient. The emissivity is assumed to be represented as a function of boundary temperature with unknown variables. Therefore, the inverse problem is treated by the estimation of these variables. Finally, four examples are presented to show the accuracy of the algorithm. The effect of the measurement errors on the accuracy of the inverse analysis is also investigated. Results show the algorithm can estimate the unknown emissivity when the measurement errors are neglected. Also it is found that increasing the measurement error decreases the accuracy of estimation of temperature-dependent emissivity.     

Self-standing crystalline TiO2 nanotubes/CNTs heterojunction membrane: synthesis and characterization

In the present study, we report for the first time synthesis of TiO(2) nanotubes/CNTs heterojunction membrane. Chemical vapor deposition (CVD) of CNTs at 650 °C in a mixture of H(2)/He atmosphere led to in situ detachment of the anodically fabricated TiO(2) nanotube layers from the Ti substrate underneath. Morphological and structural evolution of TiO(2) nanotubes after CNTs deposition were investigated by field- emission scanning electron microscopy (FESEM), glancing angle X-ray diffraction (GAXRD), and X-ray photoelectron spectroscopy (XPS) analyses.     

Surfactant modified zeolite carbon paste electrode (SMZ-CPE) as a nitrate selective electrode

A nitrate-selective electrode based on surfactant-modified zeolite (SMZ) particles into carbon paste was proposed (SMZ-CPE). The electrode was fully characterized in terms of composition, response time, ionic strength, thermal stability and usable pH range. The electrode containing 10% SMZ exhibited linear response range to nitrate species in the range of 1.00 × 10⁻⁶ to 1.00 × 10⁻³ M with a detection limit of 1.00 × 10⁻⁶ M and a Nernstian slope of 59.4 ± 0.7 mV per decade of nitrate concentration. The response of the electrode to nitrate remains constant in the pH ranges of 3.5–9.8 and 1.7–10.5 for 1.00 × 10⁻⁴ and 1.00 × 10⁻² M nitrate, respectively, and in presence of 1 × 10⁻⁴ to 1 × 10⁻³ M NaCl. The response of the electrode reaches to its equilibrium value within several seconds (10 s) after immersing the electrode in nitrate solution. Selectivity coefficients showed multivalent anions (such as arsenate, dichromate and sulfate) have higher interferences than monovalent anions (such as iodide, fluoride, bromide, chloride and thiocyanate). The electrode was used for determination of nitrate in an ammonium nitrate fertilizer sample, using direct potentiometry, and the satisfactory results were obtained. The electrode was also used for the potentiometric titration of nitrate. The validation of the obtained results in each case was proved by statistical “t” and “g” tests.     

The Effect of Ultrasonic Waves on Oil Viscosity

This study presents the development of a technique to directly investigate the effect of ultrasonic waves at 25 and 68 kHz and 100, 250, and 500 W on the viscosity of paraffin, synthetic oil, and kerosene. Experiments were performed under both controlled and uncontrolled temperature conditions in a smooth capillary tube. The results indicate that the viscosity of the liquids decreases upon exposure to ultrasound and may be attributed to induced heat generation and cavitation within the fluid. The specifics of ultrasound frequency, power, and temperature on viscosity reduction are discussed and interpreted.     

Does Density Aggravate the COVID-19 Pandemic?

Abstract

Problem, research strategy, and findings: The impact of density on emerging highly contagious infectious diseases has rarely been studied. In theory, dense areas lead to more face-to-face interaction among residents, which makes them potential hotspots for the rapid spread of pandemics. On the other hand, dense areas may have better access to health care facilities and greater implementation of social distancing policies and practices. The current COVID-19 pandemic is a perfect case study to investigate these relationships. Our study uses structural equation modeling to account for both direct and indirect impacts of density on the COVID-19 infection and mortality rates for 913?U.S. metropolitan counties, controlling for key confounding factors. We find metropolitan population to be one of the most significant predictors of infection rates; larger metropolitan areas have higher infection and higher mortality rates. We also find that after controlling for metropolitan population, county density is not significantly related to the infection rate, possibly due to more adherence to social distancing guidelines. However, counties with higher densities have significantly lower virus-related mortality rates than do counties with lower densities, possibly due to superior health care systems.

Takeaway for practice: These findings suggest that connectivity matters more than density in the spread of the COVID-19 pandemic. Large metropolitan areas with a higher number of counties tightly linked together through economic, social, and commuting relationships are the most vulnerable to the pandemic outbreaks. They are more likely to exchange tourists and businesspeople within themselves and with other parts, thus increasing the risk of cross-border infections. Our study concludes with a key recommendation that planners continue to advocate dense development for a host of reasons, including lower death rates due to infectious diseases like COVID-19.     

Effect of packing on void morphology in resin transfer molded E‐glass/epoxy composites

Effects of applying a packing pressure on void content, void morphology, and void spatial distribution were investigated for resin transfer molding (RTM) E‐glass/epoxy composites. Packing pressures of zero and 570 kPa were respectively applied to center‐gated composites containing 17.5% randomly oriented, E‐glass fiber preform. Radial samples of these disk‐shaped composites were utilized to evaluate voidage via microscopic image analysis. Two adjacent surfaces were cut from each molded disk in order to evaluate void presence from both through‐the‐thickness and planar views. The packed composite was found to contain almost 92% less void content than the unpacked composite. While void fractions of 2.2 and 2.6% were measured, respectively, from the through‐the‐thickness and planar surfaces of the unpacked composite, only 0.2% void content was observed in the packed composite from both surfaces. Digital images obtained from through‐the‐thickness surface showed that average void size dropped from 59.3 μm in the unpacked composite to 31.7 μm in the packed composite. A similar reduction in average void size from 66.7 to 41.1 μm was observed from the planar surfaces. Circular voids were found to experience higher removal rates at 99%, followed by cylindrical and elliptical voids at 83 and 81%, respectively; while irregular voids show slightly lower void removal rates at 67%. Void proximity to fiber bundles was also observed to affect void reduction as voids located inside fiber tows experience lower void reduction rates. Along the radial direction of the molded disks, removal of voids with different proximities to fibers seems to depend on their arrangement at the end of the filling stage. These findings are believed to ascertain packing as an effective void removal method for RTM and similar liquid composite molding processes. POLYM. COMPOS., 26:614–627, 2005. © 2005 Society of Plastics Engineers     

Determination of Polycyclic Aromatic Hydrocarbons (PAHs) in Olive and Refined Pomace Olive Oils with Modified Low Temperature and Ultrasound-Assisted Liquid–Liquid Extraction Method Followed by the HPLC/FLD

The cleanup method of modified low temperature was compared with the standardized method of modified ultrasound-assisted liquid–liquid (UALL) extraction for the analysis of 15 polycyclic aromatic hydrocarbons (PAHs) in olive oil and refined pomace olive oil. The modified UALL extraction consisted in purification on C₁₈ reversed-phase, Florisil-bonded-phase and NH₂ cartridges, and modified low-temperature extraction was followed by alumina-N and NH₂ solid-phase extraction (SPE) cartridges. Both methods are followed by reversed-phase high-performance liquid chromatography with fluorescence detection. The chromatograms of the final extracts showed lower interferences in both of the methods. The solvent consumption and cost for the modified UALL method were higher than those of the modified low temperature, and also, it needed more equipment, but its analysis time was less. The limit of detection and limit of quantitation of the modified UALL method were 0.16–0.97 and 0.57–2.93 μg kg^?1, respectively, and for the modified low temperature, they were 0.09–1.97 and 0.29–5.99 μg kg^?1, respectively. The PAH recoveries for the modified UALL extraction method ranged from 75.0 to 111.0 % (RSD?=?3–8 %), and for the modified low temperature, they ranged from 81.5 to 113.8 % (RSD?=?3–10 %).     

Demand response in the UK's domestic sector

The purpose of this paper is to assess the current level of demand responsiveness among domestic loads. The paper first studies different load profiles of domestic consumers which are composed of power consumption of end-use appliances. Afterwards, it differentiates those loads which could become responsive and evaluates the aggregated effect of these loads and the margin which could be derived from them. The area which has been considered is a residential area; consists of results have been demonstrated on a real residential network in southwest of the UK; small residential area in city of Bath.