A fractal Langmuir kinetic equation and its solution structure

The Langmuir kinetic equation is analyzed by the variational iteration method, its solution property is revealed analytically. The effects of desorption time and adsorption coefficient on the solution properties are also discussed, and a fractal modification of Langmuir kinetic equation is suggested.

Study on Asymmetry Concentration of Mixed Oil in Products Pipeline

Long-distance pipelines transporting multiple product oils such as gasoline, diesel and jet fuel, are important facilities for transporting fossil energy. One major concern in operation is the energy consumption of the pipeline. Energy consumption should be made optimized tracking batches of oils and cutting mixed oil, which requires an accurate prediction of concentration curve. In engineering, the concentration curve is usually assumed to be symmetric, but it is actually asymmetric, which may lead to estimation errors. Thus, the asymmetric concentration of mixed oil should be studied. The formation mechanism of the asymmetry of concentration curve has not been clearly clarified. A new method is proposed to measure the asymmetry of the concentration curve. Quantitative analysis is carried out for each factor on the asymmetry distribution of concentration curve. Based on the convection–diffusion equation, a modified oil-mixing model considering near wall adsorption effect is established. The model shows a good agreement with the Jablonski empirical formula. The error, compared with the experimental results, is less than 5%. The main findings are: (1) deviation volume has a negative correlation with pipe diameter and mean velocity; (2) adsorption coefficient has a greater impact on the length ratio of front and tail oil than diffusion coefficient; (3) the influence of all factors considered on the total length of mixed oil, front oil, tail oil and trail oil are basically the same; (4) if the limit of adsorption concentration in adsorption layer is 1, the reasonable value of adsorption coefficient a and b should be around 0.4. The results reveal the mechanism of asymmetric concentration of product oils and can provide practical suggestions to deal with the mixed oil.

Adsorption-desorption of chlorpyrifos in soils and sediments from the Rufiji Delta, Tanzania

Batch adsorption-desorption equilibrium techniques were used to investigate the adsorption capacity and influence of salinity on partitioning of the insecticide chlorpyrifos between water and soil or water and sediments from the Rufiji Delta. The data were fitted to different adsorption-desorption models and the hysteresis index was calculated using the ratio between the Freundlich exponents for desorption and adsorption, and secondly, the difference in area under the normalized adsorption and desorption isotherms using the maximum adsorbed and solution concentrations. The data showed non-linear adsorption and that chlorpyrifos was strongly adsorbed to soil and sediments from the Rufiji Delta. The linearized adsorption coefficient (KD) and Freundlich adsorption coefficient (Kf) correlated significantly with organic carbon content. Chlorpyrifos adsorption as well as hysteresis calculated by both methods decreased with salinity (i.e. the sediment adsorbs increasing amounts of chlorpyrifos with decreasing salinity). This indicates that settling of freshwater sediments is among the major removal pathways of the chemical from the water column, but increased turbulence during high tides may resuspend settled sediment simultaneously increasing salinity and re-dissolve chlorpyrifos. However, discharge of fresh water, particularly during heavy rains, increases the trapping efficiency of the sediments. The theoretical approach developed showed that the Langmuir model describes the desorption data better than the Freundlich model, and that a better index of hysteresis is one that considers areas under the adsorption and desorption isotherms, provided the desorption isotherm is described by the normalized Langmuir isotherm and the adsorption isotherm by the normalized Freundlich isotherm.

The distances measurement problem for an underwater robotic swarm: a semi-experimental trial, using power LEDs, in unknown sea water conditions

In a preceding paper, we have showed as swarm robotics displacement can be related to the deformation of a continuum material, discretized by a lattice network representing the swarm. To reach this aim, it is fundamental to know the swarm configuration, i.e., its shape; this can be computed from the knowledge of the relative distances between its elements and it is studied as a geometry distances problem. Typically, ultrasonic devices are employed to measure the distances. We propose a method based on light signal exchanged between the machines and the computing of the unknown water adsorption coefficient and distance. Aim of this paper is, therefore, to measure distances between underwater elements of the swarm using cheap power LEDs as light source and photodiode as receiver. The receiving photodiode produces a current we can correlate with distance and water adsorption coefficient; we can be able to estimate the two unknown parameters by moving the robots and stressing the emission conditions of the LED diode. Actual work is based on a previous paper where we stressed work conditions of a power LED in shallow water to change its emission characteristics; now, using these results, we can now perform a set of measurements leading to the knowledge of distances d and adsorption coefficient $$a(\lambda ). $$ a ( λ ) . The method we propose here can be a possible support to traditional ultrasonic devices

Evaluating Methane Adsorption Characteristics of Coal-Like Materials

In order to investigate the methane adsorption characteristics of coal seam materials in a “solid–gas” coupling physical simulation experiment, activated alumina, silica gel, the 3Å molecular sieve, 4Å molecular sieve and 5Å molecular sieve were selected as adsorption materials. According to the pore structure and adsorption characteristics, coal samples at the Aiweiergou #1890 working face were prepared as compared materials. The WY-98A methane adsorption coefficient measuring instrument was used to carry out this adsorption experiment under different temperatures, particle sizes and moisture contents. The results suggested that the adsorption principles of three kinds of molecular sieves under multiple factors do not fully fit a Langmuir adsorption model, and cannot be used as adsorption materials. The changing trend of the adsorption increment of activated alumina and silica gel are similar to that of coal samples, so they can be used as a coal-like materials. The methane adsorption coefficient a value changing trends of activated alumina and silica gel appear to be the same as the Aiweiergou #1890 coal samples, but the results from silica gel are closer to that of coal samples. Thus, silica gel is preferred as the adsorption material. The result provides an experimental basis for the selection of methane-adsorbing materials and carrying out “solid–gas” coupling physical simulation experiments in a physically similar testing model.

Sorptive Interactions of Fungicidal 2-(4'-Thiazolyl) Benzimidazole with Soils of Divergent Physicochemical Composition

Thiabendazole, 2-(4'-thiazolyl) Benzimidazole fungicide is rampantly used in Pakistan for controlling fungalgrowth in addition to combating various fungus driven diseases. Thiabendazole leaching and mobility patterns can beeasily predicted through investigation of Thiabendazole adsorption and desorption behavior in soils. Present work iscarried out by conducting a batch equilibration experiment for evaluation of Thiabendazole adsorption and desorption insoils from four diverse Pakistani climatological regions. Data revealed Thiabendazole had moderate to weak adsorption inselected soils with distribution co-efficient Kd(ads) ranging from 13.33 to 24.04 µg/ml in selected soils. The TBZ adsorptionin soils best fitted with Freundlich model (R2>0.87). The Freundlich adsorption coefficient (Kf(ads)) values ranged from4.51 to 8.90 µg/ml. Thiabendazole adsorption trends in the selected soils were positively influenced by the clay contentand soil organic matter while it was negatively influenced by soils’ pH. The Freundlich desorption coefficient (Kf(des))values spanned over a range of 1.03 to 6.43 µg/ml indicating decreased desorption from soils with creditable affinities forThiabendazole adsorption. The adsorptive interactions between Thiabendazole and selected soils were primarily physicalconfirmed through lower values of Gibbs free energy ∆G ≤ - 40kJ/mol. Thiabendazole desorption was highly hysterical inall soils with profound irreversibility. Thiabendazole possessed medium mobility patterns in selected soils. The loweradsorptive capability of Thiabendazole in selected soils points towards its lower application rates for combating long termenvironmentally perilous implications.