Selective Adsorption Of Water Research Articles

Effective separation of water-in-oil emulsions using an under-medium superlyophilic membrane with hierarchical pores

Separating water-in-oil emulsions is important in terms of environmental protection and resource recovery. To address the challenges posed by the water–oil interface, superwetting materials have been designed to accomplish separation through filtration and adsorption. Superhydrophobic membranes prevent the permeation of water droplets owing to extreme repellence and their size-sieving abilities. However, their use in remediating water-contaminated oil is limited by high oil viscosities. Meanwhile, in-air superhydrophilic sorbents are rarely employed for the separation of water-in-oil emulsions due to the thermodynamic and kinetic limitations of water adsorption in oil. Herein, the integration of an under-medium superlyophilic membrane with the hierarchical porous structure of wood is presented for filtration-driven selective adsorption of water from surfactant-stabilized (10 g/L) water-in-oil emulsions. Compared to filtration through a natural wood membrane or direct adsorption using an under-oil superhydrophilic wood membrane, the under-medium superlyophilic wood membrane demonstrated high separation efficiencies of > 99.95% even when applied to the regeneration of high-viscosity lubricating (6.3 mPa s) and edible (50.5 mPa s) oils, exhibiting viscosity-dependent fluxes and excellent stability. Moreover, the cost of purifying 200 mL of lubricating oil using the modified wood membrane was much lower than the oil’s market price and required a low energy consumption of ca. 1.72 kWh. Environmental implicationThe ever-growing use of petroleum and industrial/domestic oil products has led to excessive (estimated at a million tons per year) output of waste oils. Because direct discharge of waste oils into the environment causes serious pollution problems, separating water-in-oil emulsions is important in terms of environmental protection and resource recovery. Here filtration-driven water adsorption has been demonstrated to be a feasible method for the remediation of water-contaminated waste oils, even those that are highly viscous.

Elucidating the Aromatic Properties of Covalent Organic Frameworks Surface for Enhanced Polar Solvent Adsorption.

Covalent organic frameworks (COFs) have a distinguished surface as they are mostly made by boron, carbon, nitrogen and oxygen. Many applications of COFs rely on polarity, size, charge, stability and hydrophobicity/hydrophilicity of their surface. In this study, two frequently used COFs sheets, COF-1 and covalent triazine-based frameworks (CTF-1), are studied. In addition, a theoretical porous graphene (TPG) was included for comparison purposes. The three solid sheets were investigated for aromaticity and stability using quantum mechanics calculations and their ability for water and ethanol adsorption using molecular dynamics simulations. COF-1 demonstrated the poorest aromatic character due to the highest energy delocalization interaction between B–O bonding orbital of sigma type and unfilled valence-shell nonbonding of boron. CTF-1 was identified as the least kinetically stable and the most chemically reactive. Both COF-1 and CTF-1 showed good surface properties for selective adsorption of water via hydrogen bonding and electrostatic interactions. Among the three sheets, TPG’s surface was mostly affected by aromatic currents and localized π electrons on the phenyl rings which in turn made it the best platform for selective adsorption of ethanol via van der Waals interactions. These results can serve as guidelines for future studies on solvent adsorption for COFs materials.

Optimization of Mordenite Membranes Using Sucrose Precursor for Pervaporation of Water-Ethanol Mixtures.

Post-treated mordenite membranes were prepared using sucrose (C12H22O11) as a carbon precursor to block any pinholes and defects in the zeolite layer. The pervaporation (PV) process was used to separate ethanol from the water. The effects of the sucrose concentration and the pyrolysis temperature (650–850 °C) were investigated, and the resulting high separation performance compared to those post/pre-treated membranes was reported in the literature. In this study, mordenite carbon membranes yielded a water/ethanol separation factor of 990.37 at a water flux of 9.10 g/m2h. The influence of the operating temperature on the performance of the membrane also was considered. It was concluded that the selective adsorption of water through zeolite pores was achieved. The entire preparation procedure was achieved using a rapid, low-cost preparation process.

Unusual Atmospheric Water Trapping and Water Induced Reversible Restacking of 2D Gallium Sulfide Layers in NaGaS2 Formed by Supertetrahedral Building Unit

Two new ternary materials NaGaS2 (1) and the Fe-doped phase of NaGaS2, NaFe0.135Ga0.865S2 (2), have been synthesized by employing polysulfide flux. Single crystal XRD analyses of 1 and 2 show that the structure is built up of adamantane-like Ga4S10 super tetrahedral fundamental building units. These admantane-like units are connected through their corners to form [GaS2]∞– layers that are stacked one over the other with Na ions residing in between the layers to balance the charge. Both the materials have the remarkable ability to absorb atmospheric water molecules and moisture from undried solvents as verified by TG analysis and FT-IR and XPS studies. The process of water absorption leads to stable distinct material NaGaS2·∼H2O (1·H2O) and NaFe0.135Ga0.865S2·∼H2O (2·H2O) with restacked layers different from original crystal structure. This structural transformation is reversible as the transformed structures 1·H2O and 2·H2O can be returned to their original structures 1 and 2, respectively, upon heating. DFT calculation study reveals that a spontaneous exergonic hydration reaction takes place as outlined in NaGaS2 + H2O → NaGaS2·H2O with the energy release, ΔE of −73.9 kJ mol–1. DFT calculation predicts an increase in the unit cell parameters of b and c directions and shrinkage along the a direction of hydrated phase 1·H2O with an overall volume increase of 36.6%. Structural transformation affects their physical properties as the pristine compound 1 possess Na+ ion conductivity of 2.88 × 10–7 S cm–1 at 22 °C, whereas the hydrated compound 1·H2O displays ∼40 times increased ion conductivity of 1.25 × 10–5 S cm–1 at the same temperature. DRS studies show very similar optical band gaps of ∼4 eV for compounds 1 and 1·H2O, respectively, in reasonable agreement with the DFT­(HSE) band gap estimation but more than 1 eV above the DFT­(PBE)-predicted band gaps of ∼2.4 eV. A sorption study indicates selective adsorption of water over MeOH, EtOH, and CH3CN with a maximum water uptake of 2.6 H2O per formula unit at P/P0 = 0.9. A Karl Fischer titration study shows that NaGaS2 (1) is certainly capable of adsorbing water from wet methanol and can be useful as a fast desiccating agent.

Selective Adsorption of Water, Methanol, and Ethanol by Naphthalene Diimide-Based Coordination Polymers with Constructed Open Cu2+ Metal Sites and Separation of Ethanol/Acetonitrile.

The selective separation of ethanol/acetonitrile by porous materials has rarely been observed owing to their similar physicochemical properties. In this work, we report a new coordination network, [Cu2(4-pmntd)2(opd)2](4-pmntd = N,N′-bis(4-pyridymethy)naphthalene diimide, opd = disodium 1,2-benzenedicarboxylate), which exhibits selective separation of ethanol over acetonitrile. The weak coordination bonds formed by unsaturated Cu2+ sites and hydroxyl groups are the key to such performance.

Selective adsorption of water from aqueous butanol solution using canola-meal-based biosorbents

In the present paper, the capabilities of canola meal (CM)-based biosorbents for the selective water removal from aqueous solution of butanol were investigated for purifying butanol. The raw canola meal (RCM) after protein extraction was pretreated using 5% (v/v) sulfuric acid to enhance the water adsorption characteristics of CM. This pretreated canola meal (PCM) was used as an adsorbent along with the RCM adsorbent for selective water removal. Biosorbents were characterized by Fourier transform infrared, carbon hydrogen nitrogen sulfur (CHNS), Brunauer, Emmett, and Teller surface area, and X-ray diffraction. The surface area and micropore volume were increased in PCM. In addition, crystallinity index and CHNS content in PCM were also increased. Both the adsorbents were able to selectively adsorb water from the aqueous solutions of butanol. PCM demonstrated a higher water uptake and a higher final butanol concentration than RCM. The adsorption diffusion model better fits the kinetic data of water adsorption by PCM in a butanol solution containing 95.3 wt% water. The adsorption isotherm was also investigated. The mean free energy per molecule of adsorbate () based on Dubinin–Radushkevich theory indicated that water adsorption is favorable and water or butanol adsorption was physical in nature.

Hierarchically Porous Carbon Photonic Structures

AbstractHierarchically porous carbon holds promise for many applications involving not only electrical, catalytic, power storage and related functionalities but, despite absorption in the visible and near‐infrared, also optical and sensing uses are envisaged. In this paper, the self‐assembly of heterogeneous core–shell and hollow carbon spheres based on polystyrene cores, their optical properties and their response to humidity are described. The remarkable high quality of the crystals permits to exploit their singular optical properties among which a very high sensitivity to adsorption of guest materials stands out. In this regard, an original characterization of the system response is performed by means of the photonic bandgap variation with the relative gas pressure. Controlled pyrolysis enables to create and tune the features of the porosity brought about by degassing and the restructuring of the carbon lattice. Functionality associated with diverse pore populations reveals sensitivity to diverse ranges of humidity owing to selective adsorption of water in different size pores.

Thermal resonant zeolite-based gas sensor

New concept of microfabricated thermal resonant gas sensor comprising of a cantilever-like thermal device covered with a selective zeolite layer associated to heat feedback electronics is presented. Sensing principle exploits the thermal resonant frequency shift caused by mass variations upon gas adsorption in the zeolite layer; the proof-of-concept is demonstrated by selective adsorption of water and ethanol in hydrophilic FAU type zeolite layer. Hollow silicon supporting structures were fabricated in order to enhance the zeolite to silicon mass ratio, thus improving the relative thermal mass variation under gas adsorption.

A Stable Polyoxometalate-Pillared Metal-Organic Framework for Proton-Conducting and Colorimetric Biosensing.

A stable metal-organic framework pillared by Keggin-type polyoxometalate, Cu6 (Trz)10 (H2O)4 [H2 SiW12 O40 ]⋅8 H2O (Trz=1,2,4-triazole) (1), has been prepared under hydrothermal condition. The 2D layer structure with a 22-member ring was formed by Cu(2+) ions, which are connected with each other via the Trz ligands on the ab plane. Thus, the 2D layers are further interconnected through Keggin polyoxoanions to generate a 3D porous network with a small 1D channel. Moreover, the presence of polyoxoanions make it exhibit selective adsorption of water and proton-conducting properties. Additionally it showed efficient intrinsic peroxidase-like activity, providing a simple and sensitive colorimetric assay to detect H2O2 .

Selective Adsorption of Water from Mixtures with 1-Alcohols by Exploitation of Molecular Packing Effects in CuBTC

The selective removal of water from mixtures with methanol, ethanol, and 1-propanol is an important task in the processing industries. With the aid of configurational-bias Monte Carlo simulations of unary and mixture adsorption, we establish the potential of CuBTC for this separation task. For operations close to pore saturation conditions, the adsorption is selective to water that has a significantly higher saturation capacity compared to that of 1-alcohols. The water-selective separation relies on subtle entropy effects that manifest near pore saturation conditions. A further distinguishing feature is that mixture adsorption is determined to be strongly nonideal, and the activity coefficients of the constituent components deviate strongly from unity as pore saturation is approached. The predictions of the ideal adsorbed solution theory (IAST), though qualitatively correct, do not predict the component loadings for mixture adsorption with adequate accuracy. Consequently, the activity coefficients, after ...

Dimethyl ether synthesis in a gas–solid–solid trickle flow reactor with continuous adsorbent regeneration

Dimethyl ether (DME) as a green fuel is commercially produced by methanol dehydration in an adiabatic fixed bed reactor. This work describes a mathematical modeling and simulation of DME reactor in which Zeolite 4A, with the composition of Na12(Si12Al12O48)·27H2O, is considered as water adsorbent. For this purpose, a gas–solid–solid trickle flow reactor (GSSTFR) is used instead of conventional DME synthesis reactor (CR). The main advantage of GSSTFR over the conventional sorption-enhanced reaction process is the continuous adsorbent regeneration in this novel configuration. The result demonstrates that selective adsorption of water from DME synthesis in the proposed configuration leads to 11.17% enhancement in DME production rate compared to CR. Subsequently, the effect of operating conditions on the performance of the aforementioned reactor is investigated. This paper shows how the concept of in-situ water adsorption is feasible and beneficial for dimethyl ether synthesis.

Sorption-enhanced methanol synthesis in a dual-bed reactor: Dynamic modeling and simulation

This work considers a dynamic mathematical model of a dual-bed multifunctional methanol reactor (DMMR) in the face of long term catalyst deactivation. A configuration of two catalyst beds instead of one single bed with selective adsorption of water inside the first bed is developed for methanol production. Synthesis gas and flowing adsorbents are both fed to the first reactor of DMMR. Contact of gas and fine solid particles inside packed bed results in the selective adsorption of water from the methanol synthesis system which increases temperature and methanol production. This reactor functions at a higher than normal operating temperature and at very high yield. In the second converter, the heat of reaction is used to pre-heat the synthesis gas to the first bed. Thus, a more favorable temperature profile is observed in DMMR compared to single-bed multifunctional methanol reactor (SMMR), and conventional methanol reactor (CMR). This way, the catalysts are exposed to less extreme temperatures and hence, declining the catalyst deactivation via sintering. Moreover, a differential evolution (DE) algorithm as a robust method is applied to optimize the reactors length ratio. The results of this study show a higher methanol production and longer catalyst lifetime for DMMR.

Sorption-enhanced methanol synthesis: Dynamic modeling and optimization

Owing to the global energy concerns in today's world, alternative fuels such as methanol have become an increasingly attractive option to meet the growing power demand. This work considers a dynamic mathematical model of a gas-flowing solids-fixed bed reactor (GFSFBR) with in situ water adsorption for methanol synthesis in the face of long term catalyst deactivation. Contact of gas and fine solid particles inside packed bed results in the selective adsorption of water from the methanol synthesis that leads to higher methanol production compared to the conventional methanol reactor (CMR). Moreover, a theoretical investigation has been performed in order to evaluate the optimal operating conditions and maximize the methanol production in a GFSFBR using differential evolution (DE) algorithm as a robust method. Dynamic optimization result has shown that under optimum values of inlet temperature of gas phase, inlet temperature of flowing solid phase, and inlet temperature of shell side the highest methanol production can be achieved during the operating period.

Membrane/sorption-enhanced methanol synthesis process: Dynamic simulation and optimization

In this study, a dynamic mathematical model of a Membrane-Gas-Flowing Solids-Fixed Bed Reactor (Membrane-GFSFBR) with in-situ water adsorption in the presence of catalyst deactivation is proposed for methanol synthesis. The novel reactor consists of water adsorbent and hydrogen-permselective Pd-Ag membrane. In this configuration feed gas and flowing adsorbents are both fed into the outer tube of the reactor. Contact of gas and fine solids particles inside packed bed results in selective adsorption of water from methanol synthesis which leads to higher methanol production rate. Afterwards, the high pressure product is recycled to the inner tube of the reactor and hydrogen permeates to the outer tube which shifts the reaction towards more methanol production. Dynamic simulation result reveals that simultaneous application of water adsorbent and hydrogen permeation in methanol synthesis process contributes to a significant enhancement in methanol production. The notable advantage of Membrane-GFSFBR is the continuous adsorbent regeneration during the process. Moreover, a theoretical investigation has been performed to evaluate the optimal operating conditions and to maximize the methanol production in Membrane-GFSFBR using differential evolution (DE) algorithm as a robust method. The obtained optimization result shows there are optimum values of inlet temperatures of gas phase, flowing solids phase, and shell side under which the highest methanol production can be achieved.

Hydrogen/methanol production in a novel multifunctional reactor within situadsorption: modeling and optimization

SUMMARY This work proposes a novel multifunctional reactor for simultaneous production of hydrogen and methanol in which zeolite 4A is considered as water adsorbent. For this purpose, in the exothermic side of the proposed configuration, a gas-flowing solid-fixed bed reactor (GFSFBR) is used. The remarkable advantage of GFSFBR over the conventional sorption-enhanced reaction process is the continuous adsorbent regeneration in this novel reactor. MR takes the advantages of adsorption and couple technique simultaneously. The new configuration is designed as a double pipe reactor where highly exothermic methanol synthesis reactions in the exothermic side are coupled with dehydrogenation of cyclohexane. A one-dimensional, steady-state heterogeneous model is used to simulate the proposed reactor configuration. Simulation result demonstrates that selective adsorption of water in the exothermic side leads to 22.5%, 9.85% and 7.1% enhancement in methanol, benzene and hydrogen production, respectively, compared with the zero solid mass flux condition. Subsequently, the aforementioned reactor is optimized using differential evolution algorithm to maximize the hydrogen mole fraction in the endothermic side as well as the methanol yield in the exothermic side. Copyright © 2013 John Wiley & Sons, Ltd.

Sorption-enhanced reaction process in Fischer–Tropsch synthesis for production of gasoline and hydrogen: Mathematical modeling

This work proposes a sorption enhanced-thermally coupled reactor (SE-TCR) for simultaneous production of gasoline and hydrogen in which Zeolite 4A, with the composition of Na12(Si12Al12O48)·27H2O, is considered as water adsorbent. For this purpose, in the exothermic side of proposed configuration, a gas-flowing solids-fixed bed reactor (GFSFBR) is used. The main advantage of GFSFBR over the conventional sorption-enhanced reaction process is the continuous adsorbent regeneration in this novel configuration. SE-TCR takes the advantages of adsorption and couple technique simultaneously. The new configuration is designed as a double pipe reactor where exothermic Fischer–Tropsch synthesis (FTS) reactions in the exothermic side are coupled with dehydrogenation of cyclohexane. Simulation result demonstrates that selective adsorption of water from FTS in SE-TCR leads to 45% and 57% enhancement in gasoline and hydrogen yields and 84% reduction in CO2 production in comparison with the zero solid mass flux condition, respectively. This paper shows how the concept of in-situ water adsorption is feasible and beneficial for gasoline production in thermally coupled reactor.

Methanol synthesis via sorption-enhanced reaction process: Modeling and multi-objective optimization

Since liquid hydrocarbon fuels dominate the transportation sector for the foreseeable future, methanol could potentially be used as a much cleaner fuel than conventional petroleum-based fuels. Thus, development of methanol synthesis process to improve the methanol productivity has attracted increasing attention. This paper describes a steady-state mathematical model of a gas-flowing solids-fixed bed reactor (GFSFBR) with in situ water adsorption for methanol synthesis. Simulation result demonstrates that selective adsorption of water from methanol synthesis in GFSFBR leads to a significant enhancement in methanol production compared to zero solids mass flux condition. The remarkable advantage of GFSFBR over the conventional sorption-enhanced reaction process is the continuous adsorbent regeneration in this system. In the next step, a multi-objective optimization of GFSFBR is performed in order to maximize the methanol production rate and selectivity. Consequently, non-dominated sorting genetic algorithm-II (NSGA-II) is applied as a powerful method to optimize the GFSFBR. Optimization result has shown that there are optimal values of inlet temperature of gas and flowing solid phases, mass flux of flowing solids, flowing solid diameter, and pressure under which the highest methanol production rate and selectivity can be achieved. This paper shows how the concept of in situ water adsorption could be feasible and beneficial for methanol synthesis.

Sorption-enhanced Fischer–Tropsch synthesis with continuous adsorbent regeneration in GTL technology: Modeling and optimization

Fischer–Tropsch synthesis (FTS) plays an important role in the production of clean liquid transportation fuels, chemicals, and other hydrocarbon products. This work proposes a novel configuration of FTS reactor in which zeolite 4A, with the composition of Na12(Si12Al12O48)·27H2O, is considered as water adsorbent. For this purpose, a gas-flowing solids-fixed bed reactor (GFSFBR) is used instead of conventional reactor. The main advantage of GFSFBR over the conventional sorption-enhanced reaction process is the continuous adsorbent regeneration in this novel configuration. Simulation result demonstrates that selective adsorption of water from FTS in GFSFBR leads to significant enhancement in the gasoline yield and reduction in CO2 production in comparison with the zero solid mass flux condition. Subsequently, the aforementioned reactor is optimized using differential evolution (DE) algorithm as an effective and robust optimization method. Optimization results show that there are optimum values for eight decision variables under which the highest gasoline productivity can be achieved. Afterwards, the simulation and optimization results are compared with the ones in conventional reactor. This paper shows how the concept of in situ water adsorption is feasible and beneficial for FTS.

Transformation of a Mother Crystal to a Daughter Crystal through Amorphous Phase: De-assembly of Coordination Helices upon Heating and Re-assembly through Aquation

The nonlinear optical active chiral complex 1 [{Co(2,5-pdc)(H2O)2}H2O]n (2,5-pdc = 2,5-pyridine dicarboxylate) has been synthesized via a solvothermal technique using the achiral 2,5-pdc ligand. Complex 1 (phase 1), a two-dimensional coordination polymer, undergoes crystalline to amorphous (phase 2) transformation upon deaquation, which under reaquation generates a new microcrystalline phase (phase 3). The crystal structure of phase 3 has been determined by powder X-ray diffraction analysis (PXRD), which reveals that the resultant microcrystalline phase 3 is an achiral complex consisting of one-dimensional coordination chains. Phase 3 undergoes reversible structural transformation via amorphous phase (phase 2) upon dehydration and subsequent rehydration. This amorphous phase shows selective adsorption of water from a water–DMF mixture and water–CCl4 mixture. Phase 1 to phase 3 structural transformation proceeds through selective bond breaking. The magnetic studies of the two crystalline and the amorphous ...

Equilibrium Isotherms of Water and Ethanol Vapors on Starch Sorbents and Zeolite 3A

An adsorption equilibrium apparatus (gravimetric method) was used to obtain the water vapor isotherms on zeolite 3A, potato starch, corn starch, cassava starch, and cellulose at room temperature. Experimental results show that at low relative pressure, P/P0 = 0.6, the water−ethanol sorption ratio in potato starch was the highest at 64.2. The obtained sorption ratios from high to low are potato starch, cellulose, corn starch, cassava starch, and zeolite 3A. It was found that starch biosorbents are a better choice than zeolite 3A for the selective adsorption of water and ethanol. Several isotherm models—Langmuir, modified Brunauer−Emmett−Teller (mod-BET), Halsey, Smith, Henderson, Oswin, Ferro−Fintan, Guggenheium−Anderson−De Boer (GAB), or Peleg—were applied to fit the water and ethanol vapor equilibrium data obtained from this study. The accuracy of the models was evaluated by using the average relative deviation. The Langmuir model was better for the zeolite 3A adsorption system. The starch biosorbent isotherms were fitted well using the GAB, Ferro−Fintan, or Peleg models. The Peleg model with four parameters gave the best fit for the starch system, and the Smith model was good for the cellulose system.