Adsorption Hysteresis in Open Slit-like Micropores

Adsorption hysteresis in the low-pressure range is only rarely described in the literature. To optimise, for example, heat storage technologies, a deeper understanding of the low-pressure hysteresis (LPH) process is necessary. Here, two thermodynamically based approaches are further developed for analysing the LPH within the framework of thermodynamically irreversible processes and fractal geometry. With both methods developed, it is possible to obtain the description of the adsorption and desorption branches with high accuracy. Within the framework of the two thermodynamic models of the hysteresis loop, generalised equations are obtained with the control parameter in the form of the degree of irreversibility. This is done by taking the adsorption of water on alumina as an example. It is shown that the fractal dimension of the adsorption process is larger than the fractal dimension of the desorption branch, meaning that the phase state of the adsorbate is more symmetric during the adsorption step than in the desorption process.

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Investigation of competitive adsorption and desorption of heavy metals from aqueous solution using raw rock: Characterization kinetic, isotherm, and thermodynamic

MATEC Web of Conferences ◽

10.1051/matecconf/202134801016 ◽

2021 ◽

Vol 348 ◽

pp. 01016

Author(s):

Rajaa Bassam ◽

Marouane El Alouani ◽

Nabila Jarmouni ◽

Jabrane Maissara ◽

Mohammed El Mahi Chbihi ◽

...

Keyword(s):

Heavy Metals ◽

Adsorption Process ◽

Freundlich Isotherm ◽

Langmuir Model ◽

Second Order ◽

Isotherm Models ◽

Desorption Process ◽

Pseudo Second Order ◽

Rock Characterization ◽

Metals Adsorption

Heavy metals are the most dangerous inorganic pollutants Due to their bioaccumulation and their nonbiodegradability, for this, several studies have focused on the recovery of these metals from water using different techniques. In this context, our study consists of evaluating an efficient and eco-friendly pathway of competitive recovery of heavy metals (Cd, Cr and As) from aqueous solutions by adsorption using raw rock. This adsorbent was characterized before and after the adsorption process by several techniques. The multi-metals adsorption process in the batch mode was undertaken to evaluate the effect of adsorbent mass, contact time, pH, Temperature, and initial heavy metals concentration. The kinetic data were analyzed using the pseudo-first-order, pseudo-second-order and intra-particle diffusion kinetic models. According to the modeling of the experimental results, the adsorption kinetics of heavy metals were adapted to the pseudo-second-order model. The adsorption isotherms were evaluated by the Langmuir and Freundlich isotherm models. The experimental isotherm data of heavy metals were better fitted with the Langmuir model rather than Freundlich isotherm models. The maximum experimental adsorption capacities (Qmax) predicted by the Langmuir model are 15.23 mg/g for Cd (II), 17.54 mg/g for Cr (VI) and 16.36 mg/g for As (III). The values of thermodynamic parameters revealed that the heavy metals adsorption was exothermic, favorable, and spontaneous in nature. The desorption process of heavy metals showed that this raw rock had excellent recycling capacity. Based on the results, these untreated clays can be used as inexpensive and environmentally friendly adsorbents to treat water contaminated by heavy metals.

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Pickett Equation for the Description of Adsorption on Arbitrary Surfaces

Colloids and Interfaces ◽

10.3390/colloids4020017 ◽

2020 ◽

Vol 4 (2) ◽

pp. 17

Author(s):

Volodymyr V. Kutarov ◽

Eva Schieferstein ◽

Shanath A. A. Jayaweera

Keyword(s):

Fractal Dimension ◽

Water Vapor ◽

Coal Sample ◽

Lunar Regolith ◽

Theoretical Models ◽

Multilayer Adsorption ◽

Topological Approach ◽

Adsorption Of Water ◽

Adsorption Of Gases ◽

Adsorption Of Water Vapor

The theory of multilayer adsorption of gases, namely the Pickett equation, has been developed to the case of adsorption on arbitrary surfaces in a molecular and a topological approach. We present the prediction of the fractal dimension for the surface of an adsorbent and for the set of interfaces generated by the growing of layers. The theoretical models correctly predict quantities and qualitative features of the experiment for two systems: adsorption of water vapor (T = 298 K) on the sample of lunar regolith and of nitrogen (T = 77 K) on a coal sample.

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Functionalizingλ-AlOOH Surface with Silanol -- an Ab-initio Study

MRS Proceedings ◽

10.1557/proc-1000-l06-01 ◽

2007 ◽

Vol 1000 ◽

Author(s):

Petri Lehtinen ◽

Guido Grundmeier ◽

Alexander Blumenau

Keyword(s):

Ab Initio ◽

Adsorption Process ◽

Water Environment ◽

Water Molecules ◽

Organic Film ◽

Oh Groups ◽

Inorganic Films ◽

Adsorption Of Water ◽

Zinc Coatings ◽

Insight Into

AbstractOn HDG-steel, zinc coatings are used for corrosion protection. Part of that coating is composed of aluminum and this leads to the creation of aluminum oxide film on the coating with thicknesses of 2-3 nanometers. This layer is an amorphous boehmite film.Boehmite, or λ-AlOOH, has several application areas, but for us the interesting ones are related to an area where the surface is functionalized, for example in a way that the organic and inorganic films can be “glued” together. A good candidate for the interface is the silanol molecule. The idea is that the OH-groups of the molecule attach on the inorganic film and the methyl groups on the organic film and hence promote adhesion between the two.We present theoretical ab-initio results of adsorption of water and silanol molecules on the λ AlOOH (0001)-surface. Since the experimental adsorption of the silanol on the boehmite surface is done in water environment, the adsorption process is therefore a competing process. We will present some result of adsorption of silanol in the presence of water molecules to get an insight into this process.

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Trends in COP for Adsorption Cooling Cycles With Thermal Regeneration and Finite Number of Beds

ASME 2008 2nd International Conference on Energy Sustainability, Volume 1 ◽

10.1115/es2008-54039 ◽

2008 ◽

Author(s):

Derek K. Baker ◽

Bilgin Kaftanog˘lu

Keyword(s):

Finite Number ◽

Silica Gel ◽

Thermodynamic Model ◽

Adsorption Process ◽

Optimum Distribution ◽

Thermal Regeneration ◽

Desorption Process ◽

Cooling Cycle ◽

Bed Temperature ◽

Ability To Regenerate

A thermodynamic model is developed to predict trends in limiting COP of an adsorption cooling cycle with thermal regeneration between n beds, where n is any even number and each bed is spatially isothermal. The results of the model indicate the optimum distribution of beds throughout the cycle to maximize thermal regeneration. Simulations were run for silica gel-water and zeolite-water adsorbent-refrigerant pairs as the maximum bed temperature and the bed’s sensible load were varied. For the silica gel-water pair, the exothermic adsorption process occurs at lower temperatures than the endothermic desorption process, which prevents the latent loads from being thermally regenerated. This inability to regenerate latent loads results in a relatively small opportunity to increase COP through thermal regeneration, and this opportunity decreases rapidly with increasing number of beds. Conversely, for the zeolite-water pair much of the exothermic adsorption process occurs over the same temperature range as the endothermic desorption process, which allows a significant portion of the latent loads to be thermally regenerated. This ability to regenerate latent loads results in a much larger opportunity to increase COP through thermal regeneration, and this opportunity decreases much more gradually with increasing number of beds.

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Adsorption of water molecules on the surface of photo-catalyst: a first principles theoretical comparison between InVO4 and rutile TiO2

MRS Proceedings ◽

10.1557/proc-751-z3.55 ◽

2002 ◽

Vol 751 ◽

Author(s):

M. Oshikiri ◽

M. Boero ◽

J. Ye

Keyword(s):

First Principles ◽

Water Adsorption ◽

Adsorption Process ◽

Catalyst Surface ◽

Chemical Reactivity ◽

Water Molecules ◽

Activation Energy Barrier ◽

Reaction Proceeds ◽

Adsorption Of Water ◽

Dynamics Simulations

ABSTRACTThe adsorption process of water molecules on the surface of InVO4 has been investigated via first principles molecular dynamics simulations and compared with that of the well-known rutile TiO2. We have found that the surface of InVO4 shows a remarked chemical reactivity whenever comes in contact with water and H2O molecules are often adsorbed dissociatively on its surface. The reaction proceeds spontaneously in a way similar to the case of TiO2 and does not require the overcoming of an activation energy barrier. The peculiar atomic connectivity of the InVO4 bulk crystal structure and the changes at the catalyst surface induced by the water adsorption are discussed and compared with the TiO2 system.

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Chemisorption of Ammonia on Silica

Canadian Journal of Chemistry ◽

10.1139/v73-265 ◽

1973 ◽

Vol 51 (11) ◽

pp. 1771-1781 ◽

Cited By ~ 39

Author(s):

G. A. Blomfield ◽

L. H. Little

Keyword(s):

Adsorption Process ◽

Ammonia Adsorption ◽

Adsorption Sites ◽

Added Water ◽

Adsorption Of Water ◽

Amine Groups

The interaction of ammonia with silicas prepared by a variety of methods was studied to resolve conflicting reports of the mode of ammonia adsorption and to determine the role of chlorine impurities (present in the silica) in the adsorption process. Results for the adsorption of water on silica assisted in making band assignments and competition between ammonia and water for silica adsorption sites was observed. It was concluded that dehydroxylated silicas contain sites which dissociate ammonia to form Si—NH2 groups having infrared bands at 3540, 3450, and 1550 cm−1 (the surface amine groups are not displaced by added water). The presence of chlorine in the silica is not a prerequisite for chemisorption of ammonia.

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EFFECT OF GRAIN SIZE AND ACTIVATION TIME OF ZEOLITE TO ADSORPTION AND DESORPTION OF NH4OH AND KCL AS MODEL OF FERTILIZER-ZEOLITE MIX

Konversi ◽

10.20527/k.v6i2.4758 ◽

2018 ◽

Vol 6 (2) ◽

pp. 21 ◽

Cited By ~ 1

Author(s):

Muhammad Prasanto Bimantio

Keyword(s):

Grain Size ◽

Rate Constant ◽

Adsorption Process ◽

Activation Time ◽

Desorption Process ◽

Adsorption And Desorption ◽

Catalyst Carrier ◽

Three Samples ◽

Research Procedure ◽

Desorption Rate Constant

Abstract - Zeolites can be used as adsorbent, ion exchange, catalyst, or catalyst carrier. Application of fertilizer use in the zeolite also be one of the interesting topic. Zeolites in a mixture of fertilizer can use to control the release of nutrients. The purpose of this research is to study the effect of grain size and time of the activation of zeolite to adsorption and desorption of NH4OH and KCl as modeling of ZA and KCl fertilizer, to obtain the value of adsorption rate constant (ka) and desorption rate constant (kd). This research procedure include: the process of adsorption by adding zeolite with various size and time of activation into a sealed beaker glass and let the adsorption process occurs for 24 hours. After 24 hours, the solution was filtered, the zeolite then put in 100 ml of aquadest into a sealed beaker glass and let the desorption process happened for another 24 hours. Three samples with the largest difference solution concentrations looked for the value of the ka and kd. Zeolite configuration with the largest ka is trialed with fertilizer and compared with the value of ka obtained from modeling. The result for NH4OH adsorbate, -50+60 mesh 2 hours configuration zeolite give the largest ka. For KCl adsorbate, -30+40 mesh 4 hours configuration zeolite give the largest ka. The value between modeling and trials with fertilizers are not much different. Keywords: zeolite, ZA fertilizer, KCl fertilizer, mathematical modelling.

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Preparation and Desorption Performance of Gelatin Microspheres

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.664.609 ◽

2013 ◽

Vol 664 ◽

pp. 609-613

Author(s):

Xue Chuan Wang ◽

Xiao Li Hao ◽

Tao Tao Qiang

Keyword(s):

Adsorption Process ◽

Crosslinking Agent ◽

Alkali Solution ◽

Raw Material ◽

Alkali Resistance ◽

Regeneration Ability ◽

Gelatin Microspheres ◽

Desorption Process ◽

Acid And Alkali Resistance ◽

Regeneration Effect

A novel microspheres adsorbent was prepared by the emulsion-congealed crosslinking method. The gelatin was as raw material and glutaraldehyde was as the crosslinking agent. The product was characterized by AFM, Zeta Potential Tester and SEM. These results showed that there were some irregular protuberances and grooves on the surface of gelatin microspheres. The relative surface roughness namely Ra was equal to 2.469E+01nm. The isoelectric point of gelatin microspheres was 3.2. Their morphology was almost not affected by treatment of the acid and alkali, and the performance of the acid and alkali resistance was superior. The result of desorption experiment showed that the regeneration ability of gelatin microspheres was stronger in the alkali solution than that in the distilled water. The optimum desorption temperature was 30°C. The desorption process got to balance for 80min. The desorption rate got to 88% in the alkali solution and regeneration effect was obvious. The result of the second-adsorption experiment showed that the desorbed adsorbent which was used in the second-adsorption experienced the same as the first-adsorption process. And the saturated adsorption capacity changed a little. So the gelatin microspheres can be recycled.

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Si Delta Doped GaN Grown by Low-Pressure Metalorganic Chemical Vapor Deposition

MRS Internet Journal of Nitride Semiconductor Research ◽

10.1557/s1092578300002635 ◽

1999 ◽

Vol 4 (S1) ◽

pp. 305-309

Author(s):

Jong-Hee Kim ◽

Gye Mo Yang ◽

Sung Chul Choi ◽

Ji Youn Choi ◽

Hyun Kyung Cho ◽

...

Keyword(s):

Chemical Vapor Deposition ◽

Vapor Deposition ◽

Metalorganic Chemical Vapor Deposition ◽

Doping Concentration ◽

Chemical Vapor ◽

Low Pressure ◽

Voltage Measurement ◽

Desorption Process ◽

Delta Doping ◽

Metalorganic Chemical

Si delta-doping in the GaN layer has been successfully demonstrated by low-pressure metalorganic chemical vapor deposition at a growth temperature of 1040 . Si delta-doping concentration increases and then decreases with an increase in delta-doping time. This indicates that delta-doping concentration is limited by the desorption process owing to much higher thermal decomposition efficiency of silane at high growth temperatures of GaN. In addition, it was observed that the use of a post-purge step in the ammonia ambient reduces Si delta-doping concentration. From capacitance-voltage measurement, a sharp carrier concentration profile with a full-width at half maximum of 4.1 nm has been achieved with a high peak concentration of 9.8 1018 cm−3.

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Utilization of a Newly Developed Nanomaterial Based on Loading of Biochar with Hematite for the Removal of Cadmium Ions from Aqueous Media

Sustainability ◽

10.3390/su13042191 ◽

2021 ◽

Vol 13 (4) ◽

pp. 2191

Author(s):

Tunzeel Iqbal ◽

Shahid Iqbal ◽

Fozia Batool ◽

Dimitrios Thomas ◽

Malik Muhammad Hassnain Iqbal

Keyword(s):

Metal Ions ◽

Adsorption Process ◽

Low Cost ◽

Aqueous Media ◽

Freundlich Isotherm ◽

Batch Adsorption ◽

Type I ◽

Process Data ◽

Desorption Process ◽

Saccharum Munja

In order to conserve the energy used for remediation of harmful metals from aqueous media, an adsorption process was performed. It is efficient and low-cost method with zero carbon emissions as compared to other methods. A hematite-based novel nanomaterial loaded onto biochar was utilized for the remediation of toxic cadmium metal ions from aqueous media. Saccharum munja has been employed as low-cost feedstock to prepare the biochar. Three adsorbents i.e., raw Saccharum munja (SM), Saccharum munja biochar (SMBC) and hematite-loaded Saccharum munja bichar (HLSMBC) were used in batch adsorption tests to study uptake of metal ions by optimizing the experimental parameters. Experimental data and calculated results revealed maximum sorption efficiency of Cd(II) removal was given by HLSMBC (72 ppm) and SMBC (67.73 ppm) as compared with SM (48.7 ppm). Among adsorption isotherms applied on work best fit for Cd(II) adsorption on SM was found for a Freundlich isotherm with high values of correlation coefficient R2 ≥ 0.9 for all sorbents and constant 1/n values between 0–1. Equilibrium results were evaluated using five different types of errors functions. Thermodynamic studies suggested feasible, spontaneous and endothermic nature of adsorption process, while, the ∆H parameter < 80 kJ/mol indicated physiosorption and positive ∆S values promoted randomness of ions with increase in adsorption process. Data fitted into type I of pseudo second order kinetics having R2 ≥ 0.98 and rate constants K2 (0–1). Desorption process was also performed for storage, conservation and reuse of sorbent and sorbate materials.

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