Desorption Speed Research Articles

UV-crosslinked SBS block copolymers via thiol-ene reaction for efficient absorption and removal of oil/organic solvents from water

With the urgent need for oil/organic solvents spills disposal, the development of new sorbents with low cost, high sorption capacity, good selectivity and reusability is required. In the current work, three-dimensional structured absorbents have been rapidly fabricated by ultraviolet (UV)-crosslinking of styrene-block-butadiene-block-styrene (SBS) copolymers via thiol-ene reaction in 60 s, using poly-(mercaptopropyl)methylsiloxane (SMS) as crosslinker. The SBS-SMS absorbents were characterized by FT-IR, SEM, XRD, tensile strength, thermogravimetric, gel fraction and water contact angle analysis, which showed high tensile strength, good thermal stability, hydrophobicity, and acceptable gel content. The absorption capacity investigations were carried out in 7 types of organic liquids and 2 types of oils. The SBS-SMS0.005 exhibited the highest absorption performance in different organics, with the capacities of 74.6 g/g for dichloromethane, 20.1 g/g for kerosene, and 12.8 g/g for diesel oil, respectively. The impacts of sheet thickness on the absorption and desorption kinetics were studied, and the results showed that thinner absorbents illustrated faster absorption and desorption speed. Additionally, the SBS-SMS absorbents showed good selectivity and effectiveness in organic solvents/oil separation from water (separation efficiency > 93 %), well oil retention ability and oil desorption efficiency, floating properties, easy collection, as well as good reusability upon ten absorption-desorption cycles. The current SBS-SMS absorbents should have great potential in practical application for efficient oil/water separation as well as radioactive organic waste liquid treatment.

Characteristics of the gas diffusion in water-bearing coal with different damage degree and its influence mechanism

The moisture content and degree of damage in water-bearing coal affect the gas diffusion characteristics in coal, which limits the effect of gas extraction. The experiments were carried out on water-bearing coal with different damage degrees using a self-built coal and gas adsorption–desorption system to study the gas diffusion characteristics of water-bearing coal with varying degrees of damage. The results show that the pore volume of tectonic coal is positively correlated with the degree of damage. The increased moisture content in coal decreases gas desorption performance, embodied in the simultaneous reduction of desorption amount, desorption speed, and diffusion coefficient. Under the same water content condition, the gas desorption amount, gas desorption rate, and gas diffusion coefficient of coal with different damage degrees all show a downward trend, and the decline range is positively correlated with the water content. The relation between the amount of gas desorption, the time, and the moisture content of the water-bearing coal with different damage degrees has been set up. The study results provide a solid theoretical foundation for evaluating and predicting the gas extraction characteristics of coal seams with varying degrees of damage.

Desorption Characteristics of CH4-C2H6 Mixed Gas in Heavy Hydrocarbon-Rich Coal Seams.

The gas desorption characteristics of coal are closely related to the gas content of the coal seam. The gas in heavy hydrocarbon-rich coal seams contains CH4 and C2H6 heavy hydrocarbons. However, most current research on the gas desorption characteristics of coal seams focuses on CH4 analysis, ignoring the influence of the C2H6 heavy hydrocarbon gas. To accurately determine the gas content of a heavy hydrocarbon-rich coal seam, methods based on CH4 analysis are inadequate and the desorption characteristics of CH4-C2H6 mixed gas must be clarified. This work experimentally and theoretically studies the desorption characteristics of single-component gas and CH4-C2H6 mixed gas from coal samples. The results show that increasing the adsorption-equilibrium pressure was found to increase the desorption quantity and desorption speed of single-component gas and increase the desorption quantity, desorption ratio, and diffusion coefficient of mixed gas. Under the same adsorption-equilibrium pressure, the desorption quantity and rate of single-component CH4 gas exceeded those of C2H6. The quantity and speed of mixed gas desorption increased with rising CH4 concentration and decreased with rising C2H6 concentration. The change in the mixed gas concentration during desorption reflects the distribution characteristics of light hydrocarbon components on the outer surface and heavy hydrocarbon components on the inner surface of coal. From the desorption characteristics of mixed gas, desorption models of mixed gas were obtained at different concentrations, laying a theoretical foundation for accurate determinations of gas contents in heavy hydrocarbon-rich coal seams.

Study on the Characteristics and Model Optimization of Coal Particle Gas Emission Law.

In order to further clarify the transport mechanism of coalbed methane and to study the gas diffusion law in coal, this paper conducted an experimental study on the desorption law of coal particle gas. On the basis of experiment, the time-varying characteristics of the diffusion coefficient in the process of coal particle gas desorption were analyzed, and the gas diffusion calculation model considering the time-varying diffusion coefficient was obtained by experimental fitting. On this basis, the influence of coal particles with different shapes on the gas desorption law is studied, and the gas diffusion equations of flat and cylindrical coal particles based on time-varying diffusion coefficients are established. The corresponding analytical solutions are obtained by using mathematical and physical methods, and the results are verified. The results show that the larger the adsorption equilibrium pressure is, the larger the gas desorption capacity is. At the initial stage of desorption, the larger the particle size is, the smaller the desorption capacity and desorption speed are. However, after reaching the "limit particle size", the particle size has little influence on the desorption capacity and desorption speed. Under different temperature conditions, the gas desorption amount monotonously increases with time. The higher the temperature is, the greater the desorption amount is. The adsorption constant a value slightly increases with the increase of temperature and then decreases. The adsorption constant b value has a trend of decreasing with the increase of temperature. The research results have very important practical significance for the optimization of the testing method of underground coalbed methane content and the prediction of coal and gas outburst risk.

A Study on the Improvement of the Photothermal Characteristics of the Adsorbent for Sorption-Based Atmospheric Water Harvesting Driven by Solar

Facing the global freshwater resource crisis, using solar energy to produce fresh water resources in an environmentally friendly way, sorption-based atmospheric water harvesting driven by solar technology has attracted increasingly more attention. In the current research, the adsorbent MOF-801 has the advantages of a high adsorption capacity and is suitable for fields with a wide range of humidity. However, the strong interaction between the adsorbent and water molecules is conducive to rapid moisture absorption, but at the same time, the adsorbent needs higher heat to achieve regeneration, which restricts the practical application of the adsorbent. Based on the principle that carbon materials can improve the photothermal conversion performance of adsorbent, this paper prepared three composite adsorbents with MOF-801 and three different carbon materials, characterized the structure and morphology of each adsorbent, and compared the effects of different carbon materials on the performance of MOF-801 adsorbent. Among them, the photothermal characteristics of MOF-801/CNT adsorbent proposed in this paper are most significantly improved. The experiment shows that compared with MOF-801/G, the adsorption capacity is increased by 30%, and the desorption speed is increased by 50%. It maximizes water withdrawals over a period of time in arid environments.

Numerical analysis on the geometrical design of liquid cooling based carbon capture by adsorption for higher thermal efficiency

Thermal design and management is important to improve the CO2 capture by adsorption's efficiency, but current studies only consider geometric designs of a specific size. This paper develops a 2D multi-physics model to study how the spacing between two fluid pipes in the adsorbent bed affects the desorption performance, which couples the species transport, fluid dynamics, and heat transfer modules. Specifically, the model involves sandwiching the adsorbent bed between two fluid pipes, which will be parametrically studied in terms of the CO2 desorption performance, with indicators being the thermal efficiency, and the speed of CO2 desorption. Results reveal that a trade-off exists where the desorption speed decreased from 0.9 to 0.05 mol/(m3 s) when the bed height changes from 1 cm to 10 cm, but the thermal efficiency will correspondingly increase from 0.52 to 0.85. Furthermore, a sensitivity analysis on this trade-off situation is conducted by varying the thermal conductivity, regeneration temperature, CO2 feed concentration, and applying thermally conductive fins. Results reveal that increasing the thermal conductivity provides the most reasonable performance improvement characteristics as it halved the desorption time while the specific energy consumption for CO2 capture remains largely unaffected.

Metal-Decorated Phthalocyanine Monolayer as a Potential Gas Sensing Material for Phosgene: A First-Principles Study.

Research into a gas sensing material with excellent performance to detect or remove toxic phosgene (COCl2) is of great significance to environmental and biological protection. In the present work, the adsorption performance of COCl2 on pristine phthalocyanine (Pc) and metal-decorated Pc (MePc, Me = Cu, Ga, and Ru) monolayers was studied by first-principles calculations. The results show that the absorption process of COCl2 on pristine Pc and CuPc both belong to physisorption, indicating that they are not suitable gas sensing materials for COCl2. When Pc sheets are decorated by Ga and Ru atoms, the adsorption of COCl2 is changed into chemisorption, and the corresponding adsorption energies are −0.57 and −0.50 eV for GaPc and RuPc, respectively. The microcosmic mechanism between COCl2 and adsorbents (GaPc, RuPc) was clarified by the analysis of the density of states, the charge density difference, and the Hirshfeld charge. In addition, the COCl2 adsorption results in a significant conductivity variation of the RuPc monolayer, demonstrating it exhibits a high sensitivity to the COCl2 molecule. Meanwhile, quick desorption processes were noticed at various temperatures for the COCl2/RuPc system. Consequently, the RuPc monolayer can be considered as a potential candidate for phosgene sensors because of the moderate adsorption strength, high sensitivity, and fast desorption speed.

Adsorption-desorption kinetics and phosphorus loss standard curve in erosive weathered granite soil: Stirred flow chamber experiments

Weathered granite has a high soil adsorption rate and it is difficult to apply phosphate fertilizers. In order to effectively use phosphorus, it is very important to study the intensity and speed of soil retention and desorption of phosphorus. The purpose of this study is to evaluate the kinetics of adsorption and desorption in soils with different erodibility. We selected three weathered granite soils with hugely different erosions: topsoil layer (TL-Tillage layer), laterite layer (LL-Laterite layer) and sand layer (SL-Sand layer). Phosphorus adsorption and desorption experiments were successively carried out in the stirred flow reaction chamber, and the stirred flow experiment under unsaturated adsorption conditions was carried out for the first time. The maximum absorption capacity (qamax) and desorption capacity (qdmax) of phosphorus in TL soil was both greater than that in LL and SL soil. The adsorption process mainly occurs within the first 250 min of the reaction. The desorption ratio (Dr) in the TL soil is smaller than the LL and SL soil. The order of the fast reaction sites proportion (F) is SL > LL > TL in adsorption process and LL > SL > TL in desorption process. Seven key soil property indicators can fit qamax and qdmax values well. In the determination coefficient (R2) of the standard curve of phosphorus loss, SL soil is the larger than TL and LL. The qamax and Dr values measured in the stirred flow experiment are both larger than those in the batch experiment. Among the three soils, LL has the lowest adsorption capacity for P and the highest accessibility. The slow adsorption sites in TL account for the main part, and the adsorption in LL and SL mainly occurs at fast adsorption sites. Through the establishment of the phosphorus loss standard curve, the maximum phosphorus loss in the entire region can be predicted and calculated. This study can provide theoretical basis and reference for phosphorus management in similar soil types or physical geographical areas with severely eroded soils.

Electrophoretic deposition of polyaniline nanofibers on a stainless steel wire as an adsorbent for determination of tamoxifen by SPME/GC-FID in urine samples.

Polyaniline nanofiber films were fabricated on the surface of stainless steel wire via a controllable and simple electrophoretic deposition route from a nonaqueous colloidal suspension consisting of polyaniline nanofibers. The prepared coating material was then characterized by field emission scanning electron microscopy equipped with energy dispersive spectroscopy and elemental mapping analysis. The fabricated polyaniline film-coated stainless steel wire was then utilized as an effective and novel sorbent phase for solid-phase microextraction of tamoxifen for subsequent gas chromatography/flame ionization detection of this anticancer drug. Parameters consisting of the temperature, extraction time, salt concentration, agitation speed, pH, temperature and time of desorption were studied and optimized using a one-at-a-time strategy. Under the optimum conditions, detection limit (S/N =3), the limit of quantification (10/3 limit of detection), linear dynamic range, repeatability and reproducibility values of 0.51 μg L-1 , 1.7μg L-1 , 2-1,130 μg L-1 , 5.7% and 8.6% were attained, respectively. The prepared fiber can preserve 90% of its efficacy after 20 consecutive cycles, demonstrating the suitable thermal stability and cyclability of the proposed solid-phase microextraction coating material for the determination of tamoxifen by gas chromatography/flame ionization detection. The route was effectively utilized to determine tamoxifen in urine samples, with relative recoveries ranging from 89 to 106%.

A Strategy of Liquid‐Grafted Slippery Sponges with Simultaneously Enhanced Absorption and Desorption Performances for Crude Oil Spill Remediation

AbstractCrude oil spill accidents pose a worldwide environmental threat. Oleophilic and hydrophobic absorbents that can selectively absorb oil from water have shown promising application potential in oil spill remediation. Simultaneous optimization of the absorption and desorption speed of absorbents towards oil is highly desirable for their recyclable usage, but remains a great challenge, because these two properties are generally conflicting. Here, a facile and ingenious strategy is proposed to tackle the above challenge via surface modification of porous sponges with highly flexible linear polydimethylsiloxane (LPDMS) brushes. The LPDMS brushes feature liquid‐like properties at room temperature owing to its extremely low glass transition temperature, and act as a covalently‐grafted lubrication layer throughout the 3D network channels of the sponge, which can minimize contact angle hysteresis and reduce friction between oil and sponge channel. Compared to the prevalent cross‐linked polydimethylsiloxane (CPDMS) modification strategy, sponges modified with LPDMS brushes not only shows significantly enhanced absorption speed, but also exhibits superior desorption dynamics towards viscous crude oils. The design strategy of slippery sponges with liquid‐like molecules may open a new avenue for developing advanced absorbents with simultaneously enhanced absorption and desorption performances for liquid separation and purification applications.

SYNTHESIS OF BIO-NANOMAGNETITE AND ITS OPTIMIZED CONDITIONS FOR PHTHALATE ABSORBTION

Motivation/Background: Magnetic polymeric nanoparticles have vast range of applications in various fields. Coating or encapsulating of magnetic particles with polymers is one of the most useful methods of modifying magnetic nanoparticles. As these coated particles have magnetic characteristics, they can be easily collected with a single magnet instead of burdensome and time-consuming methods such as centrifugation.
 Method: In this work, nano magnetite particles were synthesized using co-precipitation method and then they were firstly coated with a single biodegradable co-polymer, i.e. poly(butylene adipate-co-terephthalate) (PBAT), and secondly with a mixture of two biodegradable polymers of PBAT and poly(butylene adipate) (PBA).
 Results: Fourier Transform Infrared (FTIR) spectrum of these two bio-nanoparticles showed their characteristics. They were also used to absorb dibutyle phthalate and dioctyle phthalate from aqueous solutions. UV-Vis was used to characterize optimization of particle mass, time and stirring speed during absorption. XRD spectrum was also taken. Volume, time and stirring speed of desorption were also optimized. In addition, calibration was performed, and the isotherm was plotted for two particles.
 Conclusions: According to XRD spectrum, particles were in nano range. They had acceptable biodegradation characteristics. They also were efficient in absorbing and desorbing phthalates and were collected easily through magnet.

Adsorption and desorption characteristics of ginsenosides from Panax ginseng C. A. Meyer on middle-pressure chromatogram isolated gels.

Four types of middle-pressure chromatogram isolated gels are evaluated for adsorption or desorption characteristics of ginsenosides from Panax ginseng. Among them, SP207SS and SP2MGS were selected for dynamic investigations based on their static adsorption or desorption capacity of total ginsenoside. Their adsorption kinetics was better explained by pseudosecond-order model and isotherms were preferably fitted to Langmuir model. Dynamic breakthrough experiments indicated an optimum sample loading speed of 4bed volume/h for either SP207SS or SP2MGS. Desorption speed was determined to be 2 bed volume/h according to desorption amount of total ginsenoside in their effluents. Eight ginsenosides were identified and quantified by high performance liquid chromatography-triple quadropole-mass spectrometry in total ginsenoside extract and different fractions during stepwise dynamic elution. For SP207SS, 27.62% of loaded ginsenosides was detected in 40% ethanol fraction, while 59.12% of them were found in 60% ethanol fraction. As on SP2MGS, the number went to 53.71 and 44.43%, respectively. Recovery rate of ginsenosides were calculated to 78.65% for SP207SS and 89.53% for SP2MGS, respectively. Intriguingly, content of Rg1 and Re in 40% ethanol fraction from SP207SS became 20.1 and 18.6 times higher than that in total ginsenoside extract by one-step elution, which could be leveraged for the facile enrichment of these two ginsenosides from natural sources.

A Study of the Differences in the Gas Diffusion and Migration Characteristics of Soft and Hard Coal in High Gas Coal Seams

At the present time, it is of major significance to examine the differences in the gas diffusion and migration characteristics of soft and hard coal in order to prevent and control safety hazards in high gas coal seams. In this study, the differences in the gas diffusion and migration characteristics between soft coal and hard coal were examined in detail using macrostructural, mesostructural, and microstructural research methods. The root causes of the differences in the gas diffusion and migration between soft coal and hard coal were revealed in the obtained research results. The study shows that, in terms of the macrostructures, the soft coal particle grains were flakey and with shapes resembling fingernails. Meanwhile, the hard coal particle grains were observed to be in the shapes of complete blocks. In addition, in terms of the mesostructures of the different coal types, it was found that the proportion of granular coal below the particle size limit of 6 mm in the soft coal was much higher than that of the hard coal. Also, from the aspect of the characteristics of the microstructures, the pores and fissures on the soft coal surfaces were observed to be better developed, and the BJH specific surface areas of the soft coal were more than twice those of the hard coal. That is to say, the gas diffusion and migration conditions of the soft coal were better than those of the hard coal. At the same time, the increments of the specific surface areas and volumes of the pores of soft coal were above 100 nm, which provided channels for gas diffusion and migration at rates of more than twice those of the hard coal. Therefore, the soft coal was more conducive to gas emissions. This study conducted gas desorption experiments on both soft and hard coal samples and found that the initial gas desorption speed of the soft coal was significantly higher than that of the hard coal. Since the instantaneous gas emissions of the soft coal were significantly higher than those of the hard coal, it was considered to be more likely that gas outbursts and transfinite accidents could potentially occur in the soft coal layers of a project site. This study’s results provided a foundation and basis for effective gas control measures in coal seams composed of soft coal layers, which will be of major significance to the safety of coal mining activities in the future.

A study on dynamic desorption process of methane in slits

The desorption behavior of methane in slit was studied in this paper. We build a differential equation which describe dynamic desorption process, and propose a correction method. The mass transfer resistance in free region is considered and the accuracy of the result is improved using this correction method. Based on differential equation, the effects of pressure, temperature and solid material on dynamic desorption speed are analyzed. Desorption becomes faster when pressure increases. When pressure is low, desorption speed increases with increasing temperature; oppositely, desorption speed decreases with increasing temperature. When pressure is low, the desorption speed at different wall material is quartz > kaolinite > graphite; when pressure is high, the desorption speed is quartz > graphite > kaolinite.

Development and Performance Evaluation of a New Compound Humidity Control Building Material

A power-free “precise” humidity control building material is made of porous inorganic minerals as carriers to be coated with the liquid of the humidity control composition, which is used to regulate humidity in indoor environment. The selected mineral substrates are made of inorganic materials such as fibers, cement, quartz sand and expanded vermiculite. Porous vermiculite is the main adsorption carrier. In order to increase the speed of moisture absorption and desorption, mineral substrates with thickness of 5mm and weight of 7kg/m2 are selected. According to the actual conditions of museums all over the country, the design requirement of suitable humidity-regulating board should involve the following points: it does not need to depend on the maintenance of power system, and can presuppose “intelligent” humidity-regulating board with “precise humidity”. It has the characteristics of large humidity-regulating capacity, rapid moisture absorption and desorption, high cost performance and convenient construction.

Chinese steamed bread: Packaging conditions and starch retrogradation

AbstractBackground and objectivesThe starch retrogradation of Chinese steamed bread (CSB) under different packaging conditions (sealed package [SP], vacuum package [VP], and thermal‐vacuum package [T‐VP]) was compared in the present study. Parameters including moisture content, moisture migration, starch granule structure, and starch retrogradation were monitored by NMR, SEM, XRD, and FT‐IR.FindingsDuring storage, T‐VP steamed bread kept higher water content and had longer shelf life compared to SP and VP. T‐VP hindered the interactions among water molecules, gluten, and starch, thus relatively increasing the mobility of water molecules represented by T23 in NMR tests compared to SP. T‐VP decreased the speed of CSB starch granules getting narrowing in SEM, maintaining a good taste of steamed bread. Results from FT‐IR and XRD suggested a lower retrogradation rate of CSB starch with T‐VP as compared to SP and VP, and the retrogradation of CSB starch was affected by free water during storage.ConclusionsThermal‐vacuum package could delay the speed of water desorption, blocked the interaction among water molecules, gluten and starch and slowed the adhesion between starch granule, thus retard starch retrogradation of CSB.Significance and noveltyThermal‐vacuum package technology as an anti‐retrogradation packaging system for CSB preservation could extend the shelf life of CSB for at least 84 days at room temperature.

Coal Anisotropic Sorption and Permeability: An Experimental Study

Knowledge of the bedding plane properties of coal seams is essential for the coalbed gas production because of their great influence on the inner flow characteristics and sorption features of gas and water. In this study, an experimental study on the anisotropic gas adsorption–desorption and permeability of coal is presented. The results show that during the adsorption–desorption process, an increase in the bedding plane angle of the specimen expands the length and area of the contact surface, thereby increasing the speed and quantity of adsorption and desorption. With an increase in the bedding angle, the number of pores and cracks was found to increase together with the volumetric strain. The evolution of permeability of coal heavily depended on stress–strain stages. The permeability decreased with the increase of stress at the initial compaction and elastic deformation stages, while it increased with the increase of stress at the stages of strain-hardening, softening and residual strength. Initial permeability increased with increasing bedding angle.

Experimental study on desorption characteristics of SAPO-34 and ZSM-5 zeolite

The dynamic characteristics of SAPO-34 and ZSM-5 zeolite in the desorption process have been experimentally studied with the gravimetric method. The weight change of the test sample was recorded continually for different conditions of temperature and pressure. The curve of the desorption degree with the temperature and the pressure was obtained and discussed. With the intrinsic different micro-structure, the two zeolites showed distinguished characteristics of the desorption. In contrast to an S-shaped desorption curve of the SAPO-34, the ZSM-5 showed an exponential desorption curve. In comparison, the desorption characteristics of the ZSM-5 were better than that of the SAPO-34 in the temperature range of 40 °C ~ 90 °C. Nevertheless, the effect of the pressure on the desorption degree was stronger for the SAPO-34 than for the ZSM-5. Further analysis revealed that the desorption speed was affected more strongly by the temperature than by the pressure.

マグネトロンプラズマCVDによるグラフェンの成長と基板材料の効果

Graphene was synthesized by radio-frequency magnetron-plasma-enhanced chemical vapor deposition on Si and SiO2 substrates along with on Cu substrate. Although the incubation period was longer and the nucleation density was smaller than the growth on Cu substrate, graphene was grown on Si and SiO2 substrates. It was speculated that the incubation period and nucleation density depend on the density of carbon precursor on substrate that is affected by the desorption speed of carbon or hydrocarbon.

In-tube extraction for the determination of the main volatile compounds in Physalis peruviana L.

An analytical procedure based on in-tube extraction followed by gas chromatography with mass spectrometry has been developed for the analysis of 24 of the main volatile components in cape gooseberry (Physalis peruviana L.) samples. According to their chemical structure, the compounds were organized into different groups: one hydrocarbon, one aldehyde, four alcohols, four esters, and 14 monoterpenes. By single-factor experiments, incubation temperature, incubation time, extraction volume, extraction strokes, extraction speed, desorption temperature, and desorption speed were determined as 60°C, 20 min, 1000 μL, 20, 50:50 μL/s, 280°C, 100 μL/s, respectively. Quantitative analysis using authentic standards and external calibration curves was performed. The limit of detection and limit of quantification for the analytical procedure were calculated. Results shown the benzaldehyde, ethyl butanoate, 2-methyl-1-butanol, 1-hexanol, 1-butanol, α-terpineol, and terpinen-4-ol were the most abundant volatile compounds in analyzed fruits (68.6-585 μg/kg). The obtained data may contribute to qualify cape gooseberry to the group of superfruits and, therefore, increase its popularity.