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Furfural, as a typical chemical indicator, is used to evaluate the aging state of the cellulose insulation in the transformer. However, partial oil replacement will lead to the loss of furfural in oil and disturb the equilibrium distribution of furfural between oil and cellulose insulation, which could affect the evaluation results of the aging state of the cellulose insulation. Unfortunately, the influence of partial oil replacement has not been focused on. Given this issue, this work studies the influence of partial oil replacement on dynamic diffusion behavior of furfural in oil-pressboard insulation. First, the dynamic diffusion behavior of furfural between insulating pressboard and oil after partial oil replacement is discussed, and the theoretical diffusion model of furfural is established. Second, based on the mass gain curve of furfural in oil, the diffusion coefficients under different oil replacement ratios are obtained. Finally, a formula for calculating the diffusion equilibrium time is proposed. This paper attempts to report a method for analyzing the impact of the oil replacement ratio on the dynamic diffusion of furfural. These findings are expected to improve the accuracy of the aging assessment results by using furfural analysis.

The flexible metal-organic framework MIL-53(Cr) has been demonstrated to be an efficient adsorbent for liquid phase adsorption and separation, while the effect of this attractive “breathing effect” on its performance remains uncertain. In this research, by increasing the amount of introduced water, MIL-53(Cr) first shrank into a narrow pore form through bound water and then reopened due to the introduction of free water. Using MIL-53(Cr) with diverse amounts of water as an adsorbent, the liquid-phase adsorption and separation of C8 aromatics, including o-xylene (OX), p-xylene (PX), m-xylene (MX) and ethylbenzene (EB), was manipulated by the pre-adsorbed water in MIL-53(Cr). Pre-adsorbing water in MIL-53(Cr) induced a preference reversal between MX and PX, where dry samples preferentially adsorbed MX, while high-water-addition samples preferred PX instead. In addition, the reopened MIL-53(Cr) with high water addition hardly adsorbed EB, thereby increasing the selectivity of xylene isomers to EB. A longer equilibrium time was observed on MIL-53(Cr) with high water addition, during which the adsorption preference shifted from OX to MX to PX. Further molecular simulation provided a microscopic explanation that water molecules in the pores tended to package around MX and EB, hindering their interaction with frameworks or other adsorbates.

This study was carried out to analyse the experimental data by hypothesis testing using various statistical tests. It enabled us to make significant statements about the adsorption parameters. Dried mango leaf powder was used as an adsorbent to remove Cu (II), Zn (II) and Pb (II) ions from contaminated water samples. Student’s t-tests, F-test and Chi-square test and ANOVA were used for the analysis of data. The calculated values of t, F and chi-square were compared with their tabulated values listed in literature within 5% level of significance. Results showed the experimental data in an accepted region on the probability charts, signifying the validity of data % zinc ions removed, equilibrium time, the effectiveness of adsorption in the removal of zinc ions, equality of variance of two samples of different concentrations and difference of means of multiple samples.

A high-performance dye adsorbent of ultrathin dodecyl-sulfate (DS−) intercalated Mg-Al layered double hydroxide nanosheets (DI-LDH Ns) were controllably synthesized by a simple one-step surfactant-assisted hydrothermal method. The unique intercalated structure with week interlayer interaction and high accessible surface of DI-LDH Ns provide efficient adsorption of methyl orange (MO), leading to its superior performance with much higher uptake capability (846.6 mg/g at 298 K) and less adsorbing equilibrium time (5 min) than those of ultrathin DS−-surface-modified Mg-Al-LDH nanosheets (DM-LDH Ns, 327.4 mg/g at 298 K, 120 min) and original Mg-Al-LDH (O-LDH, 208.2 mg/g at 298 K, 120 min). The composition and structure of these LDHs were investigated by systematic physicochemical characterization, such as XRD, TEM, FT-IR, BET and TGA. The adsorption behavior of DI-LDH Ns follows the Langmuir isotherm equation. A plausible mechanism is proposed to explain the adsorption process of such DI-LDH Ns, in which the synergistic contributions of surface and interlayer adsorption between DI-LDH Ns and MO play an important role. This study puts forward a new thought for the development of high-performance LDH adsorbents with an ultrathin intercalated structure for the efficient and rapid removal of dyes.

The aggregation behaviours of three primary reactive dyes in water were determined by molecular dynamics simulations. The aggregation equilibrium time period was determined by SASA analyses. The maximum aggregation sizes for the seven systems were not greater than that of a pentamer. For single dye solutions, the aggregation trend followed the order Y176 > B194 > R239. For two-colour mixed dye solutions, the aggregation compatibilities followed the order Y176-B194 > Y176-R239 > B194-R239. Overall, the three dyes had satisfactory aggregation compatibilities. The dye-dye and dye-water molecule interactions were analysed by RDG and aRDG methods. The results graphically showed the place, strength and type of the interactions. The main interactions between the dye anions were the VdW and π-π stacking interactions. Most parts of the dyes showed VdW interactions with water. The aggregation tendency may be affected by the number and the position of the water-soluble groups of the dyes, the molecular weight of the dye molecules and whether or not the configuration of the dyes was beneficial to the formation of π-π stacking interactions.

Selective enrichment and purification of histidine (His)-rich protein from complex mixtures is vital to satisfy the requirements of proteomic and diagnostic applications, but it still remain a chal...

To exert the imbibition between cracks and matrix effectively and enhance the development effect of tight oil reservoirs, a physical simulation method for imbibition in different scales of cores is developed by combining a high-pressure large-model physical simulation system and nuclear magnetic resonance technology (NMR) to investigate the influencing factors of imbibition process in tight reservoirs, and construct a quantitative evaluation method for the imbibition in water flooding. The results show that in the process of counter-current imbibition, the lower the permeability, the later the oil droplet precipitation, the longer the imbibition equilibrium time, and the lower the recovery degree. Fractures can effectively expand the area of imbibition and the front edge of imbibition in the contact between the dense matrix and water, reduce the resistance of oil discharge, and improve the imbibition speed and the degree of recovery. The more hydrophilic the rock, the higher the imbibition rate and imbibition recovery of tight rocks. In the process of co-current imbibition, the lower the permeability, the more obvious the imbibition, and the displacement recovery is positively correlated with permeability, while the imbibition recovery is negatively correlated with the permeability. It also shows that the imbibition distance of the cyclic water injection is greater than that of the counter-current imbibition, and the higher the permeability and the injection multiple, the longer the imbibition distance. The combination of large-scale volume fracturing with changing reservoir wettability and cyclic water injection is conducive to improving the imbibition ability of tight reservoirs. Key words: tight reservoir, physical simulation, nuclear magnetic resonance, imbibition, influencing factor, imbibition distance

Water arsenic reduction for human consumption represents a global environmental challenge, and there is a wide variety of methods for its removal. The aim of this study was to investigate the kinetics and equilibrium of arsenic adsorption of a soil from Misiones province, Argentina The material used as adsorbent was a lateritic soil. Kinetics experiments were carried out. Adsorption was evaluated through isotherms, working with concentrations between 0.01 and 30.0 mg As.L−1. Initially, a rapid decrease in the concentration of arsenic was verified, determining an equilibrium time of 24 h. Batch studies results were modeling using Langmuir and Freundlich adsorption models. It was verifying a satisfactory approximation to the Langmuir isotherm, (R[Formula presented].908). The adsorbent studied is considered efficient for arsenic removal and it could be used in isolated areas without potable water. Fil: Boglione Mondino, Rosana de Los Milagros. Universidad Tecnológica Nacional; Argentina Fil: Griffa Vignolo, Carina Andrea. Universidad Tecnológica Nacional; Argentina Fil: Panigatti, Maria Cecilia. Universidad Tecnológica Nacional; Argentina Fil: Keller Bataglia, Susana Rita. Universidad Tecnológica Nacional; Argentina Fil: Schierano, María Celeste. Universidad Tecnológica Nacional; Argentina. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Laboratorio de Química Analítica; Argentina Fil: Asforno, Melina. Universidad Tecnológica Nacional; Argentina

The search for washing agents recovered from waste is a new trend in the washing of soils contaminated with heavy metals (HMs). In the present study, dissolved organic matter (DOM) recovered from sewage sludge was used to remediate soil that originated from a metallurgical area and was contaminated with Cu (8109 mg kg−1), Pb (1473 mg kg−1) and Zn (531 mg kg−1). At pH 4 and a washing agent concentration of 4 g TOC dm−3, HMs removal proceeded according to pseudo-second-order kinetics with a relatively short equilibrium time (120 min). DOM was especially effective for removing Cu; in double washing, Cu removal was 5854 mg kg−1 (process effectiveness 72%), Zn removal was 258 mg kg−1 (process effectiveness 50.5%), but Pb removal was low (131 mg kg−1; 8.7%). DOM effectively removed metals from the exchangeable and acid soluble fraction. Based on the reduced partition index (IR), the intensity of Cu and Zn bonding in soil washed with DOM was twice as high as that in unwashed soil. Thus, DOM can serve as an effective washing agent for remediating soils contaminated with Cu and Zn, but it is not useful for removing Pb.

Low cost activated carbon was produced by treated rice husk ash for adsorptive removal of Reactive Orange 16. The selection of adsorbents, effect of equilibrium time, adsorbent dosage, concentratio...

Pottery jar is the preferred storage vessel for aging baijiu, Chinese liquor, and it could sorb liquor micro-compounds. The objective of this work was to identify the sorption of liquor micro-compounds onto pottery powder, and gained insights regarding the sorption processes and mechanism. The sorption of liquor micro-compounds onto pottery powder of different sizes was studied using different kinetic models. The results showed that the sorption capacity varied among particle size of pottery powder, which also affected equilibrium time. The sorption process could be well described by the pseudo-second-order model, and the external diffusion was the rate-limiting step. Liquor volatiles in pottery powder at equilibrium were characterized, which detected alcohols, esters, acids, and furan by gas chromatography-mass spectrometry (GC-MS). These findings demonstrated pottery could not only cause subtractive changes that occur to liquor during the aging period, but also as a vector for transferring aromas sorbed when reused.

Pharmaceutical pollution has emerged as a highly concerned issue due to its adverse effects. Elevated concentrations of pharmaceuticals in water should be regulated to satisfy the requirement for the provision of clean water. Metal-organic frameworks (MOFs) with high specific surface area, controllable porous structure, and facile modification can serve as promising adsorbents for the removal of pharmaceutical contaminants from water. In this review, a selected collection illustrating the reliable strategies and concepts to prepare the MOFs-based materials with superior water stability is described. In addition, recent progress on the adsorptive removal of pharmaceutical pollutant using burgeoning and functional MOFs is also summarized in terms of maximum capacity, equilibrium time, and regenerate ability. Meanwhile, to understand the adsorption mechanism, related interactions including coordination with unsaturated site, pore-filling effect, hydrogen bonding, electrostatic, and π-π stacking are further discussed. Finally, critical perspectives/assessment of future research emphasising on fabricating desirable MOFs and establishing structure-property relationships to facilitate capture performance are identified.

In this study, 76 μm polyoxymethylene (POM) strips were evaluated as a passive air sampler (PAS) for monitoring the volatile emissions from dredged material placed in confined disposal facilities (CDF). Laboratory evaluations were used to assess the uptake kinetics, average equilibrium time, and estimate the POM-air partition coefficients (KPOM-A) of 16 PCB congeners. The uptake kinetics defined the effective averaging time for air sampling and ranged from about a week for dichlorobiphenyls to 2 weeks or more for tetra- and pentachlorobiphenyls at ∼20 °C under internal mass transfer resistance control which was applicable for Log KPOM-A

This study aimed to develop a rapid and accurate analytical method for discriminating three lavender varieties (French blue, H-701, and C-197(2)) that could not be easily distinguished by volatile compounds. A total of 22 lavender samples from three varieties were analyzed by static headspace (HS) coupled with gas chromatography-mass spectrometry (GC-MS). The experimental parameters including equilibrium time, equilibrium temperature and water addition were investigated. The optimal analytical conditions for 0.5 g of sample were as follows: an equilibrium time of 20 min, an equilibrium temperature of 90°C and a water volume of 2 mL. Using the proposed method, a total of 26 compounds in the lavender were identified. The results were further processed with a discriminative study by cluster analysis (CA) and principal component analysis (PCA) to detect clustering formation and to establish the relationships between varieties and their volatile components. These varieties were clearly differentiated a...

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 RH 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 (R2 > 0.998) and that the fractal-like Langmuir isotherm could better describe the equilibrium data at different temperatures (R2 > 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.

Removal of inorganic and organic pollutants from synthetic and industrial wastewater samples is one of the biggest challenges facing researchers. In this work, glycine-β-cyclodextrin-functionalized carbon nanotubes (MWCNTs/Gly/β-CD) as a novel nano-adsorbent were synthesized and developed for the removal of organic pollutants. The structure and morphology of MWCNTs/Gly/β-CD was characterized by FT-IR, FESEM, TEM, XRD and EDX, and the results showed that the MWCNT was modified with Gly and β-CD. The effects of surface improvement on the adsorption of organic pollutants were studied in a batch system by considering various parameters such as contact time, adsorbent dosage, pH, and temperature. The results indicated that the maximum capacities of MB, AB113, MO and DR1 onto MWCNTs/Gly/β-CD were 90.90 mg g−1, 172.41 mg g−1, 96.15 mg g−1, and 500 mg g−1, respectively. The dye adsorption kinetics, thermodynamics and isotherms were also investigated. The results indicated that pseudo-second-order kinetics model (R2 > 0.999) and Langmuir isotherm model (R2 > 0.995) well describe the adsorption of the tested dyes on the MWCNTs/Gly/β-CD. In comparison with the raw MWCNTs and MWCNTs/Gly samples, the dye removal efficiency was increased for the synthesized MWCNTs/Gly/β-CD nano-adsorbent. Our results confirmed that β-CD-functionalized MWCNTs can be used as an effective adsorbent due to the high adsorption capacity of dyes as well as the short equilibrium time needed. Therefore, MWCNTs/Gly/β-CD was successfully applied to remove organic pollutants from synthetic and industrial wastewater samples with excellent results.

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 ΔS0 (30.67 kJ mol−1 deg−1) was positive while that of ΔH0 (−5.9 kJ mol−1) and ΔG0 (−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 ΔG0 values with temperature showed that the adsorption process was favorable at high temperature. Keywords: Aflatoxins, Adsorption, Equilibrium time, Bagasse

Acetaldehyde is an important flavor component in beer which is possibly carcinogenic to humans. Owing to the limitations of present detection methods, only free-state acetaldehyde in beers has been focused on, while acetal in beers has hardly been reported so far.; Results: A sensitive headspace gas chromatography method was developed for the determination of diethylacetal and acetaldehyde in beer. The column DB-23 was chosen with a total run time of 22.5 min. The optimal addition amount of NaCl, equilibrium temperature and equilibrium time were 2.0 g, 70 °C and 30 min respectively. For both diethylacetal and acetaldehyde analyses, the limit of detection was 0.005 mg L-1 with relative standard deviation < 5.5%. The recoveries of acetaldehyde and diethylacetal were 95-110 and 95-115% respectively. The diethylacetal and acetaldehyde average contents in 24 beer products were 11.83 and 4.36 mg L-1 respectively. The Pearson correlation coefficient between diethylacetal and acetaldehyde was the highest (0.963). Both diethylacetal and acetaldehyde contents increased to a peak value after fermentation for 3 days and then decreased to a lower value. During both normal and forced aging storage, the diethylacetal content decreased and the acetaldehyde content increased gradually over time. When beers were forced aged for 4 days, the increased ratio of acetaldehyde could be above 40.00%.; Conclusion: The newly established method can be used to assess acetaldehyde level and flavor quality in beer more scientifically. © 2018 Society of Chemical Industry.; © 2018 Society of Chemical Industry.

In this paper, the removal capacity of grape pomace was evaluated removing the KROM Brown KGT dye. Initially, batch adsorption tests were conducted to evaluate the operating parameters, which indicated 2.0 as initial pH, particle size between 0.14–1.4 mm and temperature of 25 °C, for initial dye concentration of 100 mg L−1. Based on these operating conditions, kinetic and adsorption equilibrium data were obtained. The resulting equilibrium time was 12 h. The kinetic model of pseudo first order was the one that best represented the experimental data. The adsorption equilibrium data suggest a process of monolayers, according to the Langmuir model, with a maximum biosorption capacity of 180.2 ± 3.2 mg g−1. The thermodynamic data suggest a thermodynamically favorable and exothermic process. Based on the results, it was found that the grape pomace has potential to be used as biosorbent in wastewater treatment systems containing dyes.

In this work was investigated the thermal conductivity λ of single-walled carbon nanotube (SWCNT), using the different empirical potentials: Tersoff, REBO and AIREBO. The Green-Kubo's equation was used to calculate λ through the Equilibrium Molecular Dynamics (EMD). The results were compared with SWCNT thermal conductivity reported in the literature using different methods and potentials. Through this investigation was possible to elucidate one possible reason for the huge difference of results for the SWCNT thermal conductivity reported in the literature. It has been shown that, for all the empirical potentials tested, the λ convergence was achieved when an appropriate choice of equilibrium time and simulation time was made. No significant change in λ was observed when different empirical potentials were used with adequate computational time parameters.

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 ...

Table olive processing wastewaters lead to large environmental problems mainly due to its relatively high phenolic content. In the present study, the Cloud Point Extraction (CPE) technique was used to preconcentrate the natural phenolic compounds from table olive processing wastewaters (TOPW) using three different nonionic surfactants: Genapol X-080, Triton X100 and Tween 80. The optimum conditions for the CPE of phenolic compounds were studied with respect to different experimental parameters, surfactant concentration, pH of the solution, equilibrium temperature and incubation time. The most appropriate conditions were found to be 10% of surfactant (w/v), a pH value of 2, a temperature of 70 °C and an equilibrium time of 30 min. The recovery factors of phenolic compounds from TOPW with one step CPE under optimized conditions were 62%, 65% and 68% using 10% of Tween 80, Triton X100 and Genapol X-080, respectively.

In this work, the adsorption of Basic Blue 69 (BB69) and Acid Red 114 (AR114) dyes on cement kiln dust using batch technique was studied. The effects of contact time, mass of adsorbent and initial concentration of dyes were analyzed. Five kinetic models namely, pseudo first order, pseudo second order, Elovich, intraparticle diffusion, and Boyd were applied to analyze the experimental data. The data best fitted to pseudo second order and Elovich models indicating the chemical nature of the adsorption process. The maximum adsorption capacities of BB69 and AR114 were 2119 mg/g and 2125 mg/g, respectively. The equilibrium time was 240 min when using a dose of 8 g/L compared to 300 min when using a dose of 40 g/L. The adsorption rate was fast in the initial stage. Initial equilibrium was attained after 30 min when using a dose of 40 g/L and initial dye concentration of 500 mg/L. That value increased to 90 min when using the same adsorbent dose with initial dye concentration of 300 mg/L. Generally, the equilibrium was attained within 90–300 min depending on the dye, adsorbent dose, and initial dye concentration. The rate of adsorption was found to be affected by both film diffusion and intraparticle diffusion.

Highly efficient elimination of anionic chromate remains a critical task from the biological and ecological perspective owing to their carcinogenic effects on the biosphere and ecosphere. In literature, varieties of functional materials have been applied to remove Cr(VI) from the environmental sources. In which the chemical reduction of Cr(VI) to Cr(III) by a reductant and simultaneous adsorption of Cr species is an effective technique for the removal of Cr(VI). Many effective reductants were applied in the past years, which could be categorized according to their active functional atom/group. Although very few studies illustrated the complete coordination mechanisms between Cr ions and functional groups during the reduction coupled adsorption. This review focuses on recently investigated Cr(VI) reduction coupled adsorption systems based on the electron donor (reductant) functionalities with the interactions of Cr2O72−, CrO42− and Cr3+ ions by the metal and nonmetal functional groups. Also, the removal capacity and equilibrium time were analyzed based on the findings from isotherm and kinetic studies. To conclude, we offered our insights based on the coordination of chromium species with various functionalities into future research prospects and issues in the hope of motivating more researchers to involve in this new area of functional materials for environmental pollution control.

The evolution of a two-dimensional silicon surface under hydrogen thermal treatment is studied by kinetic Monte Carlo simulations, focusing on the dependence of the migration behaviors of surface atoms on both the temperature and hydrogen pressure. We adopt different activation energies to analyze the influence of hydrogen pressure on the evolution of surface morphology at high temperatures. The reduction in surface roughness is divided into two stages, both exhibiting exponential dependence on the equilibrium time. Our results indicate that a high hydrogen pressure is conducive to obtaining optimized surfaces, as a strategy in the applications of three-dimensional devices.

Filter paper technique, humidity control technique and axis translation technique were used to study suction equilibrium time of unsaturated reticulate red clay. Test results show that: (a) suction equilibrium exists in both suction measurement or suction control using any technique in the tests; (b) suction equilibrium time of unsaturated reticulate red clay can be as short as several tens hour or several days for different suction measuring techniques, or long as several days or several tens day for different suction controlling techniques; (c) suction equilibrium time consumed in process of suction measurement is shorter than that of suction control using the same technique; (d) suction equilibrium time in measuring matric suction of unsaturated reticulate red clay using axis translation technique is shorter than that using filter paper technique; and (e) suction equilibrium time of drying process is much longer than that of wetting process, when suction is controlled using humidity control technique.

Low-cost adsorbents have been continuously developed for heavy metal removal, but little information is available concerning the follow-up treatment of the toxic metal-laden adsorbents. In this study, an optional strategy was provided for the further treatment of heavy metal-impregnated low-cost adsorbents through employing them for phosphate retention. The enhancement of phosphate adsorption by the sorbed lead was first validated using several types of raw or modified waste biomass. Tea waste-supported hydrated manganese dioxide (HMO-TW) with the highest Pb sorption capability was then chosen to systematically evaluate phosphate retention. Phosphate adsorption onto lead-laden HMO-TW (HMO-TW(Pb)) was pH-insensitive with only slight decline at pH > 8.5, and was barely affected by competing anions owing to the specific surface precipitation mechanism. Moreover, no signs of lead leakage from HMO-TW(Pb) were observed during phosphate adsorption at a wide pH range (4.2–11.3) and high ion strength (0–250 mg L−1 NaNO3). The lead on HMO-TW(Pb) was greatly stabilized through phosphate retention, which also reduced the environmental risks of their following treatment such as solidification and landfill. Additionally, the phosphate adsorption onto HMO-TW(Pb) was quick (with equilibrium time

In this paper, the adsorption of Orange Bezaktiv (SRL-150), onto Diatomite treated at 100°C (Dt-100) and at 300°C (Dt-300) was investigated in aqueous solution. The crystalline phases and surface study of Dt-100 and Dt-300 was investigated using respectively XRD, SEM, FTIR, and BET. The effect of operational parameters such as pH, contact time and, initial dye concentration was studied. From the obtained results there is not drastic difference in the crystalline phases between the obtained materials Dt-100 and Dt-300. The treatment at 300°C increases slightly the specific surface area from 11.09 to 16.12 m2/g, and pores volume. The results of adsorption tests show, that the most suitable pH and equilibrium time were respectively 2 and 30 min, at an adsorbent dosage of 2 g/L. The kinetic studies revealed that the adsorption results fitted very well with pseudo-second order model (R2 = 0.99 for both adsorbents). Adsorption isotherms results were in accordance with Freundlich.

MnO2 nanostructures with two different morphologies (nanowires and nanosheets) were uniformly deposited on diatomite via a one-pot hydrothermal method. The fast decolorization and high removal capacity for anionic dye-MO over synthesized composites had been clarified. The results revealed that the equilibrium time was shortened to as low as 10-30min, and the maximum adsorption capacities were 325mgg-1 and 420mgg-1 for nanowires and nanosheets composites, respectively, under the condition of initial pH 3 and ambient temperature. Indeed, the proposed decolorization mechanism was considered to be simultaneous multi-processes during the dye removal, including physical, physicochemical and chemical process. In principle, well-controlled cost-effective composites have promising ability to remove anionic dye pollutants for environmental remediation.

Isolation of substances by liquid-phase microextraction (LPME) or electromembrane extraction (EME) is becoming more and more important in analytical chemistry. However, the understanding of the mass transfer in LPME and EME is limited, especially for highly concentrated samples. In this work, the mass transfer in LPME and EME from aqueous samples (0.5-200 mg L-1) was studied in terms of recovery, equilibrium time, flux, and mass transfer capacity. In both EME and LPME, high recoveries were achieved at low analyte concentration, and the recoveries decreased at high analyte concentration. For EME, the loss in recovery was partly compensated by increasing the extraction voltage (from 50 to 200 V), while the LPME recovery at high analyte concentration was improved by increasing the extraction time (from 30 to 180 min). EME was superior in terms of equilibrium time and flux, while LPME provided much higher mass transfer capacity especially for highly concentrated samples. Moreover, the recovery was much more sensitive to high analyte concentrations in EME than in LPME, and the EME recovery decreased significantly above 50 mg L-1, indicating that LPME could be used to isolate analytes in a wider concentration range than EME. We believe that this fundamental study will be of great importance for the selection of a suitable membrane-based microextraction technique.

The feedstock from cinnamon (CI) and cannabis (CA) were used for providing biochar at different temperatures using the pyrolysis method (300, 400, and 600 °C) as appropriate adsorbents for removing Pb(II) ions. The properties of materials were examined with varied techniques. The BET surface area of CI600 and CA600 was higher compared with others. The adsorption efficiency of Pb(II) ions relies on initial Pb(II) concentration, pH, adsorbent dose, equilibrium time, and temperature. The adsorption isotherms of Pb(II) ions were assessed via Langmuir adsorption isotherm and the pseudo-second-order model and electrostatic interaction became visible to play the main role in the adsorption process.

17-α-Ethinyl estradiol (EE2) is a widely used drug that acts in the endocrine system and in the environment; even at low concentrations, it causes extensive damage to organisms. The most relevant factors for understanding the EE2 degradation and transport mechanisms in soil are through sorption studies. This study investigated the sorption capacity of EE2 in soil collected amidst vegetation in the region of Sorocaba, Sao Paulo state, Brazil. The soil samples were submitted to the evaluation of the physical-chemical parameters to characterization. The zero point of charge test (ZPC) was run using the adapted method of the 11-point model. Kinetic tests were then carried out, varying the removal times of the samples with fixed EE2 concentration, whereas, for the isotherm tests, the concentrations were varied, and the fixed contact time was maintained. The final concentrations of EE2 were quantified by high-performance liquid chromatography. Data treatments were carried out using mathematical modeling tests present in the literature. The soil presented a medium texture, being predominantly sandy, and the chemical parameters were classified as high and medium. Only the pH parameter was classified as low. The ZPC was 5.57, indicating an adsorption favorable to the EE2 that presented an average pH of 5.73. The adsorption kinetics showed that the equilibrium time for EE2 in contact with the soil is 12 h. The adsorption isotherm presented values related as favorable and adjustable to the Sips isotherm model and estimated the maximum adsorption capacity of 154.2 mgEE2 Kgsoil−1, showing affinity with EE2.

HS-SPME-GC/MS has been widely used in herbs and spices for essential oil analysis. This paper reports on the utility of HS-SPME method for profiling of volatile compounds from Echinacea flower using commercial and laboratory-prepared SPME fibers, and additionally comparing the volatiles extracted from HD. For achieving optimum recovery of volatiles, SPME conditions (equilibrium time, extraction temperature and extraction time) were examined. The use of SPME method enhanced the detected volatiles (161 peaks) in comparison to HD method (90 peaks). The identified volatile in Echinacea as total was 92 whether identified by SPME or HD methods. The total of tentatively identified compounds including monoterpenes, monoterpenoids, sesquiterpenes, sesquiterpenoids and other hydrocarbons with HS-SPME method (83) was higher than HD method (59). Sesquiterpenic hydrocarbons were shown to be the main group within Echinacea by both methods. It is shown that the extraction efficiencies of polymeric ionic liquid based SPME fibers are comparable with commercial ones.

A method of headspace combination with gas chromatography-mass spectrometry was developed for the determination of total volatile organic compounds (TVOC) from recycled plastic. The factors such as equilibrium temperature, equilibrium time and sample uniformity were investigated. Toluene was selected as reference material. The results showed that the optimum conditions were as follows: equilibrium temperature was 80°Cand equilibrium time was 25min. The calibration curves showed good linearity and the correlative coefficients was 0.9975. The method detection limit(S/N=3) was 0.01mg/kg, and the recoveries ranged from 83.5% to 108.3%, with RSDs

Traditional adsorption resin prepared by a low efficiency method has a low porosity and surface area, which limits the adsorption performance of the resin. Therefore, a novel porous resin was developed by structural design of the resins through post- modification with HPA and a post-crosslinked method. The novel porous post-modification resin was successfully prepared by the multistep method. Meanwhile, the high surface area and abundant micropores in HCR-AO can improve the adsorption rate by accelerating the diffusion of uranium in the external diffusion stage. The removal capacity of HCR-AO increased 366% for HCR and 120% for PSD-AO at the same initial concentration. HCR-AO takes less time to reach equilibrium than PSD-AO and HCR. Excitingly, the adsorption amount of the material dropped only slightly even after 8 cycles. The short equilibrium time and outstanding removal efficiency makes it a novel candidate for further extraction of U (VI) from seawater.

The biosorption of copper(II) from aqueous solutions by rice straw treated with Aspergillus niger , namely fermented rice straw, was investigated to identify the metal removal efficiency of biosorbents, and, for the first time, proximate analysis of raw rice straw was performed. Fermented rice straw exhibited a short biosorption equilibrium time of 30 min, high biosorption capacity (23.8 mg/g) and high removal efficiency at a pH range of 4.0–6.0. The biosorption capacity of fermented rice straw was better than that of raw rice straw under the identical conditions can be ascribed to the enzyme system secreted by Aspergillus niger which changed the surface properties of raw rice straw. In addition, the biosorption mechanism was involved in chelation with functional groups such as −OH, C O, C O and C C, and the biosorption data obtained were well described by the pseudo-second order and the fredunlich isotherm model. The obtained data suggesting that the microbiologically-treated rice straw could become a promising biosorbent.

This study aimed at the co-current removal of chromium and lead ions from synthetic waste water using dum palm kernel activated carbon. The adsorption experiment was conducted by varying time, pH and concentrations of the simulated solution. The data obtained were analyzed, and the best conditions for the uptake were at pH of 6, equilibrium time of 40 minutes. The two best isotherms models for the adsorption system were Sip, and Dubinin–Radushkevich, models respectively. Based on the Temkin adsorption energy calculated as 9.5793 and 0.4997 J/mol, the uptake of lead and chromium were chemisorption and physico-sorption, respectively. The maximum uptake calculated from Dubinin–Radushkevich plots were 14.1696 and 7.7191 mg/g, for lead and chromium, respectively.International Journal of Environment Vol.5(3) 2016, pp.104-118

Controlled mud-cap (CMD) drilling is an advanced deepwater drilling technology. When the surface pump is shut down, the CMD system causes unsteady flow that may create control problems. A new mathematical model has been developed to simulate unsteady flow in CMD systems. The model predicts the transient flow, the equilibrium time, and the change in bottomhole pressure during the unsteady flow. The simulation results show that the flow parameters change rapidly during the first 10 min and that unsteady flow leads to fluctuations in bottomhole pressure. In combination with measured data, the transient flow behavior computed by the model can be used for early detection of well kick after shutdown of the mud pump.

In the present study, a thorough investigation has been done on the removal efficiency of both As(III) and As (V) from synthetic wastewater by phycoremediation of Botryococcus braunii algal biomass. Artificial neural networks (ANNs) are practised for predicting % phycoremediation efficiency of both As(III) and As(V) ions. The influence of several parameters for example initial pH, inoculum size, contact time and initial arsenic concentration (either As(III) or As(V)) was examined systematically. The maximum phycoremediation of As(III) and As(V) was found to be 85.22% and 88.15% at pH9.0, equilibrium time of 144h by using algal inoculum size of 10% (v/v) and initial arsenic concentration of 50mg/L. The data acquired from laboratory scale experimental set up was utilized for training a three-layer feed-forward back propagation (BP) with Levenberg-Marquardt (LM) training algorithm having 4:5:1 architecture. A comparison between the experimental data and model outputs provided a high correlation coefficient (R(2)all_ANN equal to 0.9998) and exhibited that the model was capable for predicting the phycoremediation of both As(III) and As(V) from wastewater. The network topology was optimized by changing number of neurons in hidden layers. ANNs are efficient to model and simulate highly non-liner multivariable relationships. Absolute error and Standard deviation (SD) with respect to experimental output were calculated for ANN model outputs. The comparison of phycoremediation efficiencies of both As(III) and As(V) between experimental results and ANN model outputs exhibited that ANN model can determine the behaviour of As(III) and As(V) elimination process under various circumstances.

A folding-type electrochemical aptasensor was developed for the quantitative detection of penicillin G (Pen-G) residue in milk. The sensor signaling is based on the target binding-induced a change in the probe conformation. The change can drive the MB labels close to the electrode surface, thus producing a big increase in the detection signal. The effect of matrix on sensor response was systematically investigated. The results show that the sensor can respectively produce 23.4 ± 2.8% and 95.2 ± 3.2% of detection signal enhancement (SE) change in the presence of Pen-G concentrations of 1.0 nM and 0.5 mM in buffer. The corresponding limit of detection (LOD) is ~0.3 nM and the response equilibrium time is 90 s. When validated for the quantitative detection of practical milk samples, the sensor performed well with LOD of ~1.7 nM and whole measurement time of

Chemical methods used to predict the bioaccessibility of hydrophobic organic compounds (HOCs) still need further development and improvement. In this work, magnetic solid-phase extraction (MSPE) based on poly(β-cyclodextrin)-coated magnetic polydopamine (Fe3O4@PDA@PCD) was first introduced to assess the bioaccessibility of polycyclic aromatic hydrocarbons (PAHs) in soils. Due to its good hydrophilicity and submicrometer scale, Fe3O4@PDA@PCD displayed a higher extraction rate for PAHs in an aqueous solution (equilibrium time

This study compared the effects of five types of inorganic nanoparticles (INPs) on the 17β-estradiol (E2) adsorption to graphene oxide (GO). The results showed that INPs increased the equilibrium time for the adsorption of E2 to GO. Higher Brunauer-Emmett-Teller (BET) surface area of INPs resulted in lower diffusion rate of E2, and thus the adsorption rate constant (k2) calculated from pseudo-second-order kinetic model negatively correlated with the BET surface area of INPs (p = 0.037). In addition, INPs decreased the adsorption amount of E2 to GO, and the inhibition effects declined in the order of Al2O3 > ZnO > TiO2 > SiO2 > Fe2O3. This is determined by the interactions between GO and INPs. The positively charged ZnO and Al2O3 strongly heteroaggregate with GO via electrostatic attraction, and then significantly inhibited E2 adsorption to GO. In contrast, the homoaggregation of GO was superior to its heteroaggregation with negatively charged SiO2 and TiO2, and then lower inhibition of E2 adsorption to GO was induced. Fe2O3 with less negative charge (−8.48 mV) led to the lowest inhibition effect on E2 adsorption to GO because of its preferable homoaggregation. The results were further confirmed by Derjaguin-Landau-Verwey-Overbeek calculation, transmission electron microscopy, and sedimentation experiments. This study revealed how the properties of INPs influence their effects on the adsorption of E2 by GO, and the findings are critical to understand the behavior and fate of GO and pollutants in natural aquatic environment.

Urine and struvite are promising organic fertilizers that can replace conventional fertilizers. However, these fertilizers can have some emerging contaminants, such as dipyrone. This drug is one of the main painkillers consumed in the world and its continuous and indiscriminate intake can promote the camouflage of symptoms of other diseases, anaphylactic shock and even death. Thus, a fast, sensitive, inexpensive and portable method for metamizole (dipyrone) determination in several matrices, applied as organic fertilizers, has been successfully developed using portable equipment and bare carbon screen-printed electrodes in conjunction with square wave voltammetry (SWV). The main SWV operating parameters were optimized (equilibrium time (60 s), step potential (6 mV), modulation amplitude (50 mV) and frequency (10 Hz)) using univariate experiments. The proposed method presented a limit of detection of 0.097 ± 0.002 μmol L−1 (RSD = 2.72%, n = 3) for dipyrone in 0.1 mol L−1 HCl and R2 equal to 0.993. The determination in the struvite sample presented a concentration of 0.47 μmol L−1 of dipyrone. Urine sample used in the production of struvite and urine collected from an individual 10h after ingestion of 500 mg dipyrone tablet showed concentrations of 15.2 and 590 μmol L−1 of dipyrone, respectively. The recovery test in fortified struvite sample showed values between 91 and 102% (RSD = 3.1%, n = 3) and of 102% (SD = 3.7%, n = 3) in human urine, indicating that there is no matrix effect. These results reinforce the possibility of applying the proposed method on-site in a practical and fast way, without the need of significant amounts of sample promoting a more sustainable chemistry.

This paper reports a novel and rapid method for determining carboxyl groups in carbon materials by headspace gas chromatography (HS-GC). Taking carboxylated carbon nanotubes (CNTs) as an example, the experiment based on GC measurement of carbon dioxide (CO2) generated by complete reaction between carboxyl groups and sodium bicarbonate in a sealed vial, which showed that carboxyl groups in CNTs could be completely transformed into CO2 under the equilibrium temperature at 60 °C for 10 min. The relative standard deviation (RSD) of this method in the repeatability test was less than 1.52%, and the limit of quantitation (LOQ) for carboxyl content was 0.014 mmol/g in CNTs. More significantly, appropriate ultrasound of the sample before headspace injection could greatly improve the detection efficiency by reducing the equilibrium time. All in all, the HS-GC method provides an automated and accurate analysis for testing carboxyl groups in carbon materials, and it is of profound significance to develop a new way for quantitative research of carbon materials.

The analysis of residual kanamycin (KANA) has drawn great attentions based on its potential threat to human health and environment caused by its residual in aquatic and soil system. Herein, an ultrasensitive fluorescent aptasensing system was proposed based on the fluorescence change resulting from the conformation switch of kanamycin-aptamer (KANA-aptamer) with or without kanamycin in the sensing system, in which berberine was employed as the fluorescence reporter and KANA-aptamer as the recognition unit. Free berberine emits weak fluorescence at 535 nm in aqueous solution, and its fluorescence enhanced remarkably after it intercalated to KANA-aptamer. Once kanamycin was introduced into the sensing system, the randomly coiling structure of KANA-aptamer switched to a hairpin form, which made the dissociation of berberine from the KANA-aptamer, thus the fluorescence was quenched. Various experimental conditions including the concentration of berberine, KANA-aptamer, pH, ion strength and equilibrium time were studied in detail. Under the optimal experimental condition, a good correlation was obtained between the fluorescence of the sensing system and the concentration of kanamycin ranged from 5.0 nM to 71.0 nM with LOD at 2.3 nM. The presented fluorescent aptasensor also showed a delightful recovery of 96.50%–101.20% in human serum and milk. The excellent analytical performance of kanamycin shows a promising prospect in the practical application.

Highlights • Small-gap-smooth-cup-and-bob is suitable geometry for dilute digested sludge (~2%). • Small-gap-vane-and-rough cup is preferred for sludge at medium thickness (~3.5%). • Roughened wide gap geometry is preferred for highly thickened digested sludge (~6%). • An equilibrium time at each point of flow curve is necessary for sludge measurement. • Flow curve data requires to visually inspected for instabilities., Inconsistent experimental procedures have been used to characterize sludge rheology in literature. This often has resulted in proposing different rheological models for sludge as well as non-comparable data. Any collected rheological data needs to be interpreted considering the methodology used for its collection because otherwise they cannot be used by engineers for design and troubleshooting. This paper intends to shed light on the influential parameters during data collection procedure to produce a reliable and reproducible data. This paper systematically investigates the impact of different geometries, preshear, equilibrium, rest and storage time on flow curve measurement for digested sludge in the range of 2.3 to 6% total solid and recommends a reliable procedure for reproducible sludge flow curve measurements. While the magnitude of impacts is different, we found all factors are significantly dependent on the sludge solid concentration. Besides, the method of the development of the protocol can be utilized to develop appropriate protocols for rheological characterization of any other sludge. The customization highlights are:•Selecting the geometry according to the sludge solid concentration.•Allocating an equilibrium time at each point of flow curve according to the sludge solid concentration.•Flow curve data requires to visually inspected for instabilities., Graphical abstract Image, graphical abstract

A macroporous silica-based (Calix[4]+Dodecanol)/SiO2-P absorbent for separation of Cs(I) from HNO3 solution was prepared by impregnating the 1,3-[(2,4-Diethylheptylethoxy)oxy]-2,4-crown-6-calix[4]arene and its molecule modifier 1-dodecanol into a macroporous silica/polymer composite support. To establish its application into partitioning of Cs(I) from High Level Liquid Waste (HLLW), the adsorption properties and radiation effects on the adsorbent were investigated. The adsorbent showed a relatively large distribution coefficient of Cs(I) and fast equilibrium time in simulated HLLW. Additionally, the adsorbent under the gamma-ray field was found to be able to selectively adsorb Cs(I) with similar behavior to the adsorption without irradiation up to at least 170 kGy.

An attempt has been taken to reformulate the dyeing process of cotton fabric with the aim of reducing the environmental pollution with economic advantages by the substitution of harmful chemical auxiliaries with ethanol at low concentration. The results were studied in comparison with the standard conventional recipe, and a favorable effect of alcohol addition, at 1–3 g/L, on the dye uptake, equilibrium time of isothermal dyeing was achieved in laboratory scale. Fastness properties and dyeing levelness were also compared. Color fastness to wash and rubbing were found to be unaffected with better levelness of dyeing by the introduction of ethanol in the reactive dyeing recipe of cotton. Ethanol replaced dyeing auxiliaries successfully by serving the function of both wetting and leveling agent where it is readily biodegradable, and hence, this process becomes eco-friendly. Finally, environmental and economic issues arising from chemical substitution of dyeing additives with ethanol were considered, and environmental advantages and cost saving due to the application of ethanol in comparison with dyeing auxiliaries were brought to light.

The pectin gel has been proved to be an effective material for methylene blue (MB) removal, but it presented low adsorption rate. To get over the vice, the pectin microgel particles (PMP) was prepared. No matter high or low initial MB concentration, the PMP presented high adsorption rate with equilibrium time of 20 min. The adsorption process based on monolayer adsorption and adsorbance of 284.09 mg/g was obtained. What's more, the adsorption process was electrostatic adsorption with mean free energy of 74.223 kJ/mol. The pseudo-second-order kinetic model fitted perfectly to the experimental data. The MB uptake was controlled by film diffusion mechanism. Furthermore, the recovery efficiency of regenerated PMP were higher than 80% after three cycles. The present study showed the PMP presented acceptable adsorbance, high adsorption rate and recovery efficiency. Thus, we believe that the PMP was a promising candidate for MB cleanup.

The article covers the one-dimensional Kardar-Parisi-Zhang equation, weak drive limit, universality, directed polymers in a random medium, replica solutions, statistical mechanics of line ensembles, and its generalization to several components which is used to study equilibrium time correlations of anharmonic chains and of the discrete nonlinear Schrodinger equation. The notes are an extended version of my lectures at Les Houches July 2015.