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Radon can move freely through air and water. Water radon measurement is a method of earthquake monitoring and water radon can be used as an environmental tracer to follow transit pathways. A novel bubbling device was developed for continuous detection of waterborne radon levels. Equilibrium between water and gas-phase radon concentrations in the gas path of this device is attained through circulation and bubbling. Monitoring gas radon allows dynamic tracking of water radon concentration. At the temperature of 22.6 °C, the device exhibits a sensitivity of 0.0016 CPM/Bq/m3 and detects concentrations within the range of 0.96–180,000 Bq/m3. [ABSTRACT FROM AUTHOR]

Local scour depth around bridge piers is time-dependent. It develops asymptotically towards the equilibrium depth of scour under clear-water scour. Scour is the major cause of bridge pier failure. Many equations are available for predicting temporal and equilibrium scour depth. The present study discusses the phenomenon of temporal scour depth variation at wide bridge piers and deals with the techniques for its estimation. Two types of pier shapes (circular and rectangular) were used to collect the data. The rate of local scour, observed for different pier widths and sediment sizes, was recorded. The data indicates that 50% of the equilibrium scour depth (0.5dse) is achieved at a variety of times, which range from 0.7% to 11%, according to the sediment coarseness values. Similarly, 80% of the equilibrium scour depth develops in a time-varying from 10% to almost 50% of the equilibrium time. The upper limit curve for all the data is also presented. [ABSTRACT FROM AUTHOR]

This study investigates the influence mechanism of particle size and gas pressure on the dynamic diffusion law of CO2 in coal.We used a self-developed high pressure adsorption and desorption experimental system for coal seam to analyze the dynamic adsorption-diffusion characteristics before the adsorption equilibrium of gas in coal based on the volumetric adsorption experiment, which was combined with the classical single hole diffusion model to calculate the CO2 diffusion coefficient at different times.The results show that the adsorption equilibrium time is positively correlated with the coal particle size, and decreases with the increase of adsorption equilibrium pressure.Larger coal particle size would result in more obvious decreasing trend.The effective diffusion coefficient is found to be more effective than the diffusion coefficient in explaining the relationship between particle size and equilibrium time.Smaller particle size would result in higher effective diffusion coefficient and shorter adsorption equilibrium time.The effective diffusion coefficient shows a power function with time.The initial effective diffusion coefficient (De0) and effective diffusion attenuation coefficient (β) both decrease with the increase of particle size.De0 first increases and then decreases with the increase of equilibrium pressure, and the β exhibits varying relationships with the increase of equilibrium pressure depending on different particle sizes of the coal.Smaller particle size would result in better connectivity between the pores of coal, leading to shorter diffusion paths of gas molecules and lower diffusion resistance, thus more facilitated to adsorption.Gas pressure poses a driving effect on CO2 adsorption and diffusion, but with the continuous adsorption of coal samples, the coal matrix expands and blocks the pores, leading to a narrowing of the diffusion channel and diminished driving effects.

In this study, the influence of the bottom mixing system on the balance characteristics of instantaneous kinetic energy was analyzed by devising the regiment configuration of the bottom nozzles. The results indicated that the stirring strength of the case with the regiment distribution is higher due to the synergy of gas streams. The time required for the kinetic energy to reach the equilibrium state is the shortest at a gas flowrate of 960 Nm3 h−1. It is suggested that the arrangement of bottom tuyeres located on the line of the same circumference should not be dispersed to reduce the convection effect and the dissipation of kinetic energy. To reflect the flow conditions inside the bath, the agitating intensity index was defined in the investigation. When the outer nozzles are located at a pitch circle diameter ratio of 0.7, the maximum index is 1.94 × 10−3. [ABSTRACT FROM AUTHOR]

The investigation of bed topography downstream of culverts is very important. Since bed topography goes through extreme changes through time, this study investigated the temporal evaluations of bed topography. Also, the bed level downstream of culverts, as one of effective parameters in topography in different time spans, was investigated. One of the most important findings of the study is that with increasing the experiment time and approaching the equilibrium moment, the change percentage of the maximum scour depth decreased. Also with changes to and decrease in the bed level downstream of the culvert, the change percentage of the depth scour decreased. Another salient finding of this study was that the maximum scour over the beginning durations of the tests in case of equal downstream level and culvert bed level was approximately equal to the maximum scour in cases where the downstream bed level differed from the culvert bed level by 0.067 and 0.13 times the culvert mouth width. [ABSTRACT FROM AUTHOR]

Abstract The investigation of bed topography downstream of culverts is very important. Since bed topography goes through extreme changes through time, this study investigated the temporal evaluations of bed topography. Also, the bed level downstream of culverts, as one of effective parameters in topography in different time spans, was investigated. One of the most important findings of the study is that with increasing the experiment time and approaching the equilibrium moment, the change percentage of the maximum scour depth decreased. Also with changes to and decrease in the bed level downstream of the culvert, the change percentage of the depth scour decreased. Another salient finding of this study was that the maximum scour over the beginning durations of the tests in case of equal downstream level and culvert bed level was approximately equal to the maximum scour in cases where the downstream bed level differed from the culvert bed level by 0.067 and 0.13 times the culvert mouth width.

Abstract Ceramic water filters (CWFs) are point-of-use devices mostly used in developing countries as a result of their effectiveness in the treatment of household water. However, there is a dearth of knowledge on the metal ions adsorption behavior of the filter materials. Therefore, this study investigates the adsorption behavior of the divalent metal ions using commercially available ceramic water filters as adsorbents, in a batch experiment and compared the data, to the extent of metal ion removal during filtration. The ceramic water filters were characterized with x-ray fluorescence spectrometer, x-ray powder diffractometer and fourier-transform infrared spectrophotometer. An adsorption batch experiment was conducted and filtration experiments were performed to determine the extent of divalent metal ions removed. The results of the study showed that divalent metal ions were adsorbed efficiently by ceramic water filters. The pseudo-second-order kinetic model best described the kinetic behavior of metal ion removal process. The extent of adsorption of ceramic water filters was in the range: 7.015–335.77 mgg−1. The adsorption patterns fitted the Freundlich isotherm model while the entropy, enthalpy, and Gibbs free energy, indicate that the processes for all CWF-adsorbents are endothermic, feasible and spontaneous. The kinetic and thermodynamic behavior of CWF-adsorbents indicate that the mechanism of the sorption process is chemisorption. There was a significant difference in the amount of divalent metal ions adsorbed in batch experiments compared to filtration experiments for ceramic water filter materials (Pot filter and candle filter). The metal ions adsorption potentials of ceramic water filters are found to be rate dependent; hence the rate of filtration must be of concern to manufacturers.

Ceramic water filters (CWFs) are point-of-use devices mostly used in developing countries as a result of their effectiveness in the treatment of household water. However, there is a dearth of knowledge on the metal ions adsorption behavior of the filter materials. Therefore, this study investigates the adsorption behavior of the divalent metal ions using commercially available ceramic water filters as adsorbents, in a batch experiment and compared the data, to the extent of metal ion removal during filtration. The ceramic water filters were characterized with x-ray fluorescence spectrometer, x-ray powder diffractometer and fourier-transform infrared spectrophotometer. An adsorption batch experiment was conducted and filtration experiments were performed to determine the extent of divalent metal ions removed. The results of the study showed that divalent metal ions were adsorbed efficiently by ceramic water filters. The pseudo-second-order kinetic model best described the kinetic behavior of metal ion removal process. The extent of adsorption of ceramic water filters was in the range: 7.015–335.77 mgg−1. The adsorption patterns fitted the Freundlich isotherm model while the entropy, enthalpy, and Gibbs free energy, indicate that the processes for all CWF-adsorbents are endothermic, feasible and spontaneous. The kinetic and thermodynamic behavior of CWF-adsorbents indicate that the mechanism of the sorption process is chemisorption. There was a significant difference in the amount of divalent metal ions adsorbed in batch experiments compared to filtration experiments for ceramic water filter materials (Pot filter and candle filter). The metal ions adsorption potentials of ceramic water filters are found to be rate dependent; hence the rate of filtration must be of concern to manufacturers. [ABSTRACT FROM AUTHOR]

Copyright of Basic Sciences Journal of Textile Universities / Fangzhi Gaoxiao Jichu Kexue Xuebao is the property of Basic Sciences Journal of Textile Universities and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Nitrate is one of the leading pollutants in water sources. The limitation of water resources and the increase of surface and underground water pollution by nitrate ions make it necessary to find acceptable environmental solutions to remove this substance from water sources. For practical applications, the adsorbent should have a high capacity, be cheap and easy to use. This research investigated the effect of eggshell, rice husk, wheat straw, and oak leaf nanostructured adsorbents on the removal of nitrate ions from aqueous solution by continuous and discontinuous systems. Discontinuous experiments studied the effect of factors such as pH, equilibrium time, optimal adsorbent mass and initial concentration of nitrate ions. Continuous experiments evaluated the effect of changes in the concentration of nitrate entering the column in increasing the efficiency of the adsorption column, and investigated the application of continuous models of adsorption in the description of breakthrough curves. According to the obtained results, the optimal pH of adsorption for the adsorbents under study was 5. Equilibrium time for eggshell, rice husk, and wheat straw nanostructured adsorbents was 30 and 120 min for oak leaf nanostructured adsorbents. By increasing the adsorbent mass from 0.3 to 1.6 g at the equilibrium time and optimal pH, the efficiency of nitrate ion adsorption has reached its peak by the nanostructured adsorbents of eggshell, rice husk, straw and wheat straw in the mass of 0.5 g and the oak leaf reached nanostructured adsorbent in the mass of 0.7 g. By increasing the initial concentration of nitrate ions from 5 to 120 mg/L, the efficiency of nitrate ion removal by eggshell, rice husk, wheat straw and oak leaf nanostructured adsorbents has decreased. The adsorption process was followed by Hove's kinetic model and Langmuir isotherm. The results of continuous tests showed that the total amount of nitrate absorbed and the adsorption capacity of the column increased with the increase of the concentration of nitrate entering the column, and the Thomas model was more consistent with the laboratory data. It is generally concluded that the eggshell, rice husk, wheat straw and oak leaf nanostructured adsorbents have the potential to remove nitrate ions. [ABSTRACT FROM AUTHOR]

The cost-effective adsorbent was developed to remove copper ions from an aqueous solution. The carbonized sunflower stem was analyzed by SEM, FTIR, and XRD. A batch mode adsorption kinetics study was conducted and was observed that the adsorption of copper ions onto carbonized sunflower stem followed pseudo-second-order kinetics. The equilibrium time was found to be 160 min. Maximum uptake (90 %) of copper ion was observed at pH 3.0 for 20 mg L-1. The experimental data were also analyzed for Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin isotherms. [ABSTRACT FROM AUTHOR]

It finds coefficients I x i that solve the problem: HT ht Graph (6)where the input data, B I x i b data, and output data, B I y i b data, are given and are matrices or vectors. The tortuosity ( I i ) decreases with the increase of bentonite column length, which proves that the diffusion path tortuosity of unit size decreases with the increase of bentonite column length, so the effective diffusion coefficient increases with the increase of bentonite column length. [Extracted from the article]

This study focuses on scour depth development around 45° wing‐wall setback abutments in a compound channel. The results show that the scour development curves almost have similar shape and they can be described using exponential function. It is generally observed that the scour hole achieved 80% of the equilibrium scour depth at a scour time equals to 25% of the equilibrium scour time. Additionally, an increase in the relative abutment length and the contraction ratio causes an increase in the equilibrium time. However, this time decrease with increasing flow depth ratio. Finally, new empirical equations are proposed to predict the development of scour depth and the time to reach the equilibrium state. These equations will be useful to predict these characteristics of scour hole especially for setback abutments in compound channel and predict the temporal development scour depth for previous studies that have available data related to maximum scour depth. [ABSTRACT FROM AUTHOR]

The management of disposable diapers is a major problem. Moreover, light-textured soils are characterized by low water holding capacity and excessive drainage, thus significant portion of irrigation water is lost below the root zone. A laboratory study was conducted to evaluate the potential of recycling disposable baby diapers to conserve soil moisture in light-textures soils. The water absorbency [water absorption capacity (WAC) and water absorption rate (WAR)] of the recovered Super absorbent polymers (SAPs), from diapers, was evaluated and described under different ionic solute strengths (0.0, 0.5, 1.0, 2.0, 3.0 and 4.0 dS m-1) at different time periods. Additionally, several swelling measurements of the SAPs were determined when added to sandy clay loam soil using different levels [0.0, 0.4, 0.6, 0.8 and 1.6% (w/w)] for five rewetting cycles (over a period of 6 months). As the swelling time increased, the WAC increased, while WAR decreased. However, both WAC and WAR were reduced as the solution salinity increased. The recovered SAPs exhibited WAC of 311.0 and 111.0 g g-1 in solution of 0.0 and 3.0 dS m-1, respectively. Polynomials functions were used to calculate the equilibrium time and threshold solute concentration for the SAPs. The average equilibrium time was 4.5 minutes and the threshold solute concentration was 2.78 dS m-1. At SAPs concentration of 1.6%, the water retained by the soil increased by 2.6 folds. The specific amount of water retained (SWR) by SAPs in the SAPs-soil mixture was decreased with repeating wetting, thus, after 6 months, the average WHC of the soil was decreased by 14% compared to initial wetting. The recycling of baby diapers might have a great potential to conserve soil moisture in light soils using water of good quality. However, since the SAPs in diapers are Na+ based, further research is needed to explorer the impact of such treatment on soil chemical properties.

Copyright of Nonferrous Metals (Mining Section) is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Pressure and suction plate tests are among the most common techniques for determining the soil–water characteristic curve. The required testing period depends on many parameters and equilibrium times may vary from a few minutes to several weeks. This paper presents a numerical evaluation of the equilibrium process, considering the influence of soil type, equipment specifications, the use of thin high air-entry value (HAEV) membranes, and the employment of the interrupted outflow method (IOM). A fully coupled numerical model was developed and verified for the analysis of the conservation and flow of water and air in the specimen-HAEV interface system. Verification and sensitivity analyses showed, however, that the suction and pressure plate tests may be adequately represented using a simplified decoupled version of the full model. The results of the sensitivity analysis showed not only the role of the HAEV interface characteristics, but also the effect of soil type, suction value, suction step magnitude, and the suction path. It was found that the IOM offers greater control over testing times, but may cause undesirable suction reversals within the specimen. Finally, a simple method is presented to estimate the equilibrium times using basic testing parameters. [ABSTRACT FROM AUTHOR]

Introduction: Copper and zinc are two of the most important microelements affecting plant growth which can be influenced by many factors. The adsorption processes play a determinative role in solubility of copper and zinc elements in the soil solution and, therefore, their availability to plants. Organic matter is one of the most important factor that have an significant role on the absorption and desorption of elements in the soil. These materials are divided into humic and non-humic groups. Humic substances are divided into three groups of fulvic acid, humic acid and humic, based on their resistance and solubility in acid and base. Humic acid with a medium molecular weight and color is soluble into base and insoluble into acid, and has a medium resistance against the microbial attack. It forms the most important organic part of the soil and is capable to adsorb metals. The purposes of this study were to extract soil humic acid, study the adsorption of metals on the surface of humic acid and to determine the metals adsorption coefficients using adsorption isotherm models. Materials and Methods: Sampling was done from forest areas of northern Iran. Some physical and chemical properties of the studied soil were determined. Then, the humic acid of the soils was extracted by 0.1 M NaOH and 6 M HCl, and purified by 0.1M HCl+0.3M HF. Functional group, E4/E6 ratio (Optical density or absorption of dilute solutions at wavelengths of 465 and 665 nm), and humification index of the extracted humic acid were measured. Some other properties of the extracted humic acid have also been analyzed. To study the adsorption isotherms of Zn and Cu in the presence of humic acid, solutions with concentrations of 10, 20, 40, 60 and 80 mg/L of ZnCl2 (zinc adsorption testing) and CuSO4 (copper adsorption testing) were prepared, respectively in a 0.01M Ca(NO3)2 background solution, and added to 250 g of humic acid. The samples were shaken for 12 hours (based on the time of equilibrium) at pH=5 and 25 °C in incubator shaker, then the samples were centrifuged and the supernatant was passed through filter paper and measured using atomic adsorption spectrophotometer device. The difference between initial concentration and final concentration identified the amount of adsorbed element. Results and Discussion: The results of the acidic functional groups measurement in the humic acid samples revealed that the most of total acidity (60%) was due to the presence of phenolic groups while the carboxylic groups were responsible for the remaining (40%). Phenolic groups were abundant in the primary stages of the decomposition of humic materials. Since the soil used for extracting humic acid was covered with broad leaf trees and the continuous entry of organic matter into it (the fall of leaves) lasted for many years and due to the low temperature of the soil in part of the year, it can be said that a significant part of the soil organic matter is in the primary or middle stages of humification and the phenolic OH groups/carboxylic groups ratio in the humic acid extracted from them was high. The equilibrium time for adsorption of both metals occured at 12 h to achieve maximum adsorption level in the presence of humic acid. The obtained experimental data were fitted to three models of Langmuir, Freundlich, and Tampkin. The accuracy of mentioned models to fit data were estimated based on the detection coefficient (R2) and the roots of mean square error (RMSE). The results showed that the Freundlich model with higher detection coefficient and lower roots of mean squared error describes the adsorption of copper and zinc elements, well. To better compare the adsorption of the elements by humic acid, Langmuir's b parameter (Expresses maximum adsorption) can be used. The maximum adsorption of copper (23.04 mg/g) by humic acid was higher than zinc adsorption (13.8 mg/g). This trend is consistent with the Irving--Williams series of divalent elements: Mn < Fe < Zn < Co < Ni < Cu. It is generally believed that humic acid is a good complexing agent for many metal ions and its binding to metal ions can improve the adsorption. Significance differences were tested by a parametric t-test or F statistics in ANOVA (analysis of variance). There was a significant correlation between the maximum adsorption of metals (b) and the properties of humic acid at a probability level of 5%. [ABSTRACT FROM AUTHOR]

The management of disposable diapers is a major problem. Moreover, light-textured soils are characterized by low water holding capacity and excessive drainage, thus significant portion of irrigation water is lost below the root zone. A laboratory study was conducted to evaluate the potential of recycling disposable baby diapers to conserve soil moisture in light-textures soils. The water absorbency [water absorption capacity (WAC) and water absorption rate (WAR)] of the recovered Super absorbent polymers (SAPs), from diapers, was evaluated and described under different ionic solute strengths (0.0, 0.5, 1.0, 2.0, 3.0 and 4.0 dS m-1) at different time periods. Additionally, several swelling measurements of the SAPs were determined when added to sandy clay loam soil using different levels [0.0, 0.4, 0.6, 0.8 and 1.6% (w/w)] for five rewetting cycles (over a period of 6 months). As the swelling time increased, the WAC increased, while WAR decreased. However, both WAC and WAR were reduced as the solution salinity increased. The recovered SAPs exhibited WAC of 311.0 and 111.0 g g-1 in solution of 0.0 and 3.0 dS m-1, respectively. Polynomials functions were used to calculate the equilibrium time and threshold solute concentration for the SAPs. The average equilibrium time was 4.5 minutes and the threshold solute concentration was 2.78 dS m-1. At SAPs concentration of 1.6%, the water retained by the soil increased by 2.6 folds. The specific amount of water retained (SWR) by SAPs in the SAPs-soil mixture was decreased with repeating wetting, thus, after 6 months, the average WHC of the soil was decreased by 14% compared to initial wetting. The recycling of baby diapers might have a great potential to conserve soil moisture in light soils using water of good quality. However, since the SAPs in diapers are Na+ based, further research is needed to explorer the impact of such treatment on soil chemical properties. [ABSTRACT FROM AUTHOR]

Integrative simulation techniques for predicting component properties, based on the conditions during processing, are becoming increasingly important. The calculation of orientations in injection molding, which, in addition to mechanical and optical properties, also affect the thermal shrinkage behavior, are modeled on the basis of measurements that cannot take into account the pressure driven flow processes, which cause the orientations during the holding pressure phase. Previous investigations with a high-pressure capillary rheometer (HPC) and closed counter pressure chamber (CPC) showed the significant effect of a dynamically applied pressure on the flow behavior, depending on the temperature and the underlying compression rate. At a constant compression rate, an effective pressure difference between the measuring chamber and the CPC was observed, which resulted in a stop of flow through the capillary referred to as dynamic compression induced solidification. In order to extend the material understanding to the moment after dynamic solidification, an equilibrium time, which is needed until the pressure signals equalize, was evaluated and investigated in terms of a pressure, temperature and a possible compression rate dependency in this study. The findings show an exponential increase of the determined equilibrium time as a function of the holding pressure level and a decrease of the equilibrium time with increasing temperature. In case of supercritical compression in the area of a dynamic solidification, a compression rate dependency of the determined equilibrium times is also found. The measurement results show a temperature-invariant behavior, which allows the derivation of a master curve, according to the superposition principle, to calculate the pressure equilibrium time as a function of the holding pressure and the temperature.

We used two types of soil with different physicochemical properties ( loam and sand), oven-dried them, and then added the known isotopic composition mineral water that was reference water to compose the soil-water mixture with different soil water contents (loam; 0.15, 0.20, 0.30 g ⋅ g-1 ; sand: 0.10 g ⋅ g-1). Alter that, we set up different equilibrium time (loam; 3, 6, 12, 24, 48, 72, 96 h; sand: 96 h) to ensure that the dry soil particles were well mixed with the added water. The soil water was extracted by mechanical centrilugation and cryogenic vacuum extraction alter equilibrium, and their isotope composition was analyzed. Results showed that the isotopic values of soil water extracted by mechanical centrilugation method had no significant difference in same water content with different equilibration times, but were more enriched compared with the reference water isotopic value. The maximum enrichment for hydrogen and oxygen isotope was 7.38%e and 1.24%e, respectively. In contrast, cryogenic vacuum extraction method resulted in more depleted soil water isotopes than reference water, with the maximum depletion for hydrogen and oxygen isotope being 6.27%e and 1.03%e, respectively. Moreover, the degree of depletion increased with the increases of equilibrium time (less than 24 h) at low water content, and became stable after 24 h. With the increases of soil water content, the isotopic composition of the extracted soil water was less affected by the two extraction methods. The water isotope value of loam that had high clay content, was more sensitive to the extraction method than the sandy soil that had low clay con- tent. The difference of isotopic composition caused by extraction methods did not affect the plant water source segmentation. [ABSTRACT FROM AUTHOR]

Abstract In this article, a brief outlook of different kinetic models employed in batch adsorption study has been discussed. As the adsorption kinetic modeling has so far been inadequately addressed in the literature, therefore the equilibrium kinetic profiles of adsorption study were portrayed into an innovative sigmoidal expression q t q e = 0.637 tan − 1 sinh 5.233 × t t e G n G , using the Gudermannian function with significant mathematical hypotheses. The kinetic data obtained from methylene blue and acridine orange dye adsorption studies using Abelmoschus esculentus seed powder were utilized to evaluate the adequacy of the proposed model. The extent of model compatibility was evaluated through six non-linear error functions represented as composite fractional error, residual root mean square error, Marquardt's percent standard deviation, average relative error, average percentage error and Chi-square error. This aforesaid three-parametric sigmoidal model was compared with pseudo-first-order, pseudo-second-order, intra-particle diffusion, Elovich, Bangham, modified-Freundlich and hyperbolic tangent model, which are known as the well-recognized kinetics. According to the comparison of different error functions and to the assessment of corrected Akaike information criterion, the developed model was ranked as the best fitting kinetic model illustrating the experimental data. It also demonstrated that the normalized Gudermannian kinetic equation has the ability to predict the equilibrium adsorption time at different initial dye concentrations, which can be exploited for configuring the large-scale industrial reactors. Graphical abstract Unlabelled Image Highlights • A three-parametric kinetic model was developed for batch adsorption at solid-liquid interface. • The normalized Gudermannian function was applied to describe the kinetic equilibrium data. • The proposed model can predict the exact equilibrium time of the adsorption process. • The model was employed to fit the experimental results for the adsorption of methylene blue and acridine orange dyes. • The feasibility of the kinetic model was verified using non-linear error functions and Akaike information criterion. [ABSTRACT FROM AUTHOR]

Abstract In this work, the pseudo-first-order (PFO), pseudo-second-order (PSO) and Vermeulen equations were modified by introducing an adjustable parameter i.e. the fractional surface coverage θ. The Langmuir kinetic equation was modified by the fractal-like approach and the separation factor R H was proposed to express essential characteristics of the fractal-like Langmuir isotherm. The kinetic and isotherm data obtained from nitrate adsorption on the PAN/AC composite were used to evaluate the validity of these models. Results indicated that the modified PSO equation could accurately predict the equilibrium time at different initial nitrate concentrations (R 2 > 0.998) and that the fractal-like Langmuir isotherm could better describe the equilibrium data at different temperatures (R 2 > 0.994). The magnitude of parameter b reflected the affinity of the adsorbent for the adsorbates. The innovation and significance of the present study was that the modified kinetic and isotherm models could predict the equilibrium time and describe the heterogeneous surfaces, respectively. Therefore, this work is expected to extend the application scope of the PFO, PSO and Vermeulen equations and Langmuir isotherm. Highlights • The equilibrium time can be predicted by modified PFO, PSO and Vermeulen equations. • The fractal-like Langmuir isotherm model is proposed. • The fractal-like Langmuir equation can describe nitrate adsorption well. • A new separation factor is defined. [ABSTRACT FROM AUTHOR]

A novel adsorbent for the removal of aflatoxin from poultry feed was prepared from bagasse and was characterized by surface area analyzer, SEM, XRD, FTIR, TG/DTA and EDX. A specially designed chamber was used for the preparation of the adsorbent. SEM, XRD and FTIR analysis showed the iron oxide presence on the adsorbent surface. The adsorption parameters were determined for aflatoxin adsorption using Freundlich and Langmuir isotherms. The equilibrium time was 115 min for 200 ppm at pH 3 while 150 min at pH 7. At high pH there was a decline in percent adsorption. Best fit was obtained with pseudo first order kinetics model for the kinetics data of adsorption. The value of Δ S 0 (30.67 kJ mol −1 deg −1 ) was positive while that of Δ H 0 (−5.9 kJ mol −1 ) and Δ G 0 (−9.303, −9.610, −9.916 and −10.226 kJ mol −1 correspond to 30, 40, 50 and 60 °C) was negative. The increase in Δ G 0 values with temperature showed that the adsorption process was favorable at high temperature. [ABSTRACT FROM AUTHOR]

The effect of rainfall spatial distribution and duration on determining rainfall spatial resolution for runoff discharge prediction and equilibrium time estimation was studied. We simulated hydrographs and equilibrium times of storms which have the same spatial averaged rainfall intensity with wide range of spatial distributions and durations under stationary storm conditions on an idealized plane. The equilibrium times under various rainfall conditions were estimated with an approximate solution based on the kinematic wave assumption. The runoff hydrographs were simulated using a kinematic wave runoff model. The approximate and computed results were used to investigate the relationship between the spatial–temporal rainfall characteristics and rainfall spatial resolution. From the simulated results, it was found that (i) A required rainfall spatial resolution to achieve threshold accuracy depended on rainfall spatial distribution. For the simulated cases, the critical rainfall spatial resolution was higher as the slope of rainfall spatial distribution was steeper. (ii) The rainfall duration, as well as rainfall spatial distribution, was an important factor for determining a required rainfall spatial resolution for accurate flood prediction. The required rainfall spatial resolution to achieve threshold prediction accuracy was higher as the rainfall duration was shorter. (iii) The rainfall spatial distribution and duration which were traditionally neglected need to be considered in lumped runoff modelling or measurement as an important factor. Although limited to the ideal test cases, the maximum errors due to the low rainfall spatial resolution for the equilibrium time and peak discharge were about 25% and 35%, respectively. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate the effects of initial oil volume and equilibrium time on the swelling factor during swelling tests. These parameters have not been addressed thoroughly in previous studies. Most investigators used only their own initial oil volume and equilibrium time during their experiments. The present study is focused on investigating the effects of these parameters under various initial oil volumes and equilibrium times according to the design of experiments. The optimum initial oil volume and equilibrium time to yield maximum swelling factor are determined. The initial oil volume and equilibrium time are found to contribute a positive impact to the swelling factor. Based on the results, the maximum initial oil volume is 3.4 cc or 85% of the total cell volume while the optimum equilibrium time is 101 min. The increment of the initial oil volume of.5 cc or 12.5% to 3.4 cc or 85% increases the swelling factor to 6.7% while the increment of the equilibrium time from 30 to 101 min increases the swelling factor to 4.9%. The study also found that the response surface method is appropriate to produce the optimum parameters in order to get maximum swelling factor. [ABSTRACT FROM AUTHOR]

In this study, a new hyperbolic tangent model has been proposed for analyzing adsorption kinetic at the solid-solution interface. The most important advantage of the proposed model is its ability to predicate the equilibrium time of adsorption, which is very vital to optimize the cost of the adsorption system design. The ability of the new model for modeling of adsorption kinetic and predication of the equilibrium time was tested by using of the generated data points based on the mixed 1,2-order equation (MOE). The new model was applied for fitting of the reported experimental data. The obtained results show that the new model can analyze the experimental data very well. [ABSTRACT FROM AUTHOR]

In this study, rice husk (RH) and activated carbon (AC) adsorbents was used for removing of cadmium ion from aqueous solution at pH = 6. Equilibrium time was shortened with a decrease in initial concentration of Cd from 50 mg/l to 1 mg/l for both adsorbent. This time was 60 and 45 minutes for rice RH and AC, respectively. Furthermore, not only the equilibrium time decreased with increasing initial concentration from 50 mg/l to 500 mg/l, but it became identical for both absorbents. Adsorption efficiency increased with a decrease in initial concentration of solution for both adsorbents. Maximum adsorption efficiency was found for RH and AC at initial concentration of 1 mg/l. Obtained adsorption efficiency at this concentration were approximately 98.0 and 99.7 percent for RH and AC, respectively. Fitting the results to the Lagergren (1898) and Ho et al. (1996) models was also attempted; the latter model better described the outcome. Moreover, the Freundlich isotherm better described the data than the Langmuir isotherm.

Magnetic carbon nanocomposites were prepared from maize wastes and were characterized by surface area analyzer, scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric/differential thermal analysis (TG/DTA), and electron dispersive X-ray (EDX). The presence of iron oxide on the adsorbent surface was confirmed from SEM, XRD, and FT-IR analysis. Freundlich and Langmuir isotherms were used for the determination of adsorption parameters. The effect of pH on adsorption process was evaluated, and a decline in percent adsorption was noted at high pH. The equilibrium time at pH 7 and 3 was 96 and 180 min, respectively, and nearly 90% removal of aflatoxin B1 was achieved for both adsorbent. Pseudo-first-order and pseudo-second-order kinetic equations were used to analyze the kinetic data. Best fit was obtained with pseudo-first-order kinetics equation. The thermodynamics parameters were also determined, ΔS°was positive (64.438 kJ mol−1 deg−1) while ΔH°(−16.24 kJ mol−1) and ΔG°were negative (−1.949, −2.593, −3.238, and –3.882 kJ mol−1corresponding to 30, 40, 50, and 60°C, respectively). [ABSTRACT FROM PUBLISHER]

Derivation of spatial distribution of travel time is required in some conceptual rainfall-runoff transformation models. Application of a kinematic wave (KW) solution to delineate isochrones of travel time may be straightforward, particularly in an overland flow regime. In this article, a new analytical approach based on the diffusive wave (DW) solution is developed for calculation of travel time. The discharge hydrograph over a rectangular plane will be calculated based on the developed analytical DWmethod through the application of the time-area method. Differences between calculated maximum travel time (i.e., equilibrium time), isochrone locations, and outflow discharge between the KWand DW solutions are compared with those of the numerical dynamic wave (DYW) solution. It is shown that analytical DW results are closer to those of the DYW in comparison with those of the KW. The effect of the K0F20 number on the solution accuracy is investigated, where K0 is the kinematic wave number and F0 is the Froude number. It is perceived that as K0F20 decreases, the differences between KWand analytical DWsolutions grow. For instance, at equilibrium time, the new DWsolution improved the results by 5 to 12% over the KW solution. In addition, the DWisochrones lie upstream of the corresponding KWisochrones. Finally, the 1.5 < K0F20 < 20 interval is proposed for using an analytical DW solution in lieu of the KWand DYW solution. [ABSTRACT FROM AUTHOR]