Zeolite Adsorption Research Articles

An initial evaluation of the thermodynamic or kinetic separation performance of cation-exchanged LTA zeolites for mixtures of propane and propylene

Adsorptive separation of propylene (C3H6) and propane (C3H8) may represent an energy-efficient alternative to conventional cryogenic distillation. In this perspective, a set of zeolitic adsorbents of LTA type structure (pure-silica zeolite (Si-LTA) and cation- (Na+, 33% of Li+, 50% of Mg2+ and 50% of Ca2+) containing zeolites) were prepared, then characterized using various techniques such as PXRD, gas adsorption measurement, TGA, XRF, SEM and EDX mapping. Thanks to an in-house manometric dosing setup coupled with a Tian-Calvet type microcalorimeter, the pure gas adsorption isotherms and their corresponding differential enthalpies of adsorption were measured at 303 K and for pressures up to 5 bar. To fit those adsorption data, the dual-site Langmuir was selected as the best fit model, and by using the Ideal Adsorbed Solution Theory (IAST), thermodynamic selectivities were determined. The mass transfer constants were also estimated by fitting, separately, the Linear Driving Force (LDF) and isothermal micropore diffusion models to adsorption kinetic curves, thus allowing kinetic type selectivities to be calculated. The combination of those selectivities reveals that the thermodynamic separation of C3H6 from C3H8 is highly favorable on CaNa-LTA, followed by its MgNa-LTA counterpart with IAST selectivities around 15 and 5, respectively. On the other hand, the monovalent cationic zeolites (i.e., Na- and LiNa-LTA) show a predominance of steric effects. Also, except for Si-LTA which shows a moderate kinetic separation, the studied materials are potential candidates, in the following order CaNa- > MgNa- > LiNa- > Na-LTA, for the separation of C3H6 from C3H8 by adsorption-based technologies.

H-beta zeolite-based dispersive solid-phase strategy for the multi-residue determination of pesticides

In this work, electrostatic interactions, hydrogen bonding and other interactions between a variety of pesticides and H-beta zeolite are discussed based on thermodynamics (Gibbs free energy, enthalpy, and entropy). Combined with the physical properties of the target compounds (octanol-water partition coefficient and molar volume), the characteristics of the physical adsorption on the synthetic zeolite were analyzed, the results of H-beta zeolite adsorption showed that the adsorption rate had a nonlinear relationship with the physical properties, and the adsorption reaction was dominated by the adsorption on the surface and in the pores of the H-beta zeolite. Based on the principle of zeolite adsorption, the parameters of absorbent amount, adsorption time, sample pH, ion strength, sample volume and desorption solvent were optimized, a vortex-assisted dispersive solid-phase extraction procedure coupled with liquid chromatography-tandem mass spectrometry was developed for the analysis of multiple pesticides in surface water. The sample was adjusted by phosphate buffer or hydrochloric acid to pH 4, then adsorbed by 50 mg of zeolite within 10 min, adding 2% (g/v) sodium chloride to the solution. The absorbent was eluted with a mixture of acetonitrile-methanol containing 0.5% formic acid after separation, then filtered prior to analysis. The optimized vortex-assisted dispersive solid-phase extraction method simultaneously achieved a low adsorbent dosage, a high enrichment factor of 25, rapid pre-concentration for 30 min, a low solvent usage of 2 mL and multi-target simultaneous analysis. Method performance in terms of accuracy, precision, limit of detection, and limit of quantitation was performed to validate the reliability of the procedure. The proposed protocol achieved acceptable accuracy (recoveries between 62% and 107%), and precision (relative standard deviation < 20%). The limit of detection of the method was below 0.1 μg/L, and the limit of quantitation was 0.08 μg/L or 0.2 μg/L. The results indicated that zeolite is a promising adsorbent with high adsorption capacity. It has the advantages of being a fast, simple, green and economical method for determining residual pesticides in water.

Characterization Biofuel from Empty Fruit Bunch through Thermal Cracking

Empty Fruit Bunches (EFB) are oil palm waste that has the potential as a source of bioenergy because it contains lignocellulose (cellulose, hemicellulose, and lignin) so that it can be converted into biofuel through thermal cracking, adsorption, and distillation processes. Thermal cracking is the decomposition of the chemical content of biomass by utilizing heat without a mixture of oxygen at a temperature of 200oC–600oC. This study aims to obtain the characteristics of the raw material of EFB in the form of proximate, ultimate, lignin, and biofuel produced. The research was conducted using a thermal cracking reactor designed to control the temperature at 300oC, 350oC, 400oC, and 450oC. The results showed that the raw material characteristics of EFB from proximate were 13.66% water content, 8.74% ash content, 58.66% volatile matter and 18.90% fixed carbon. This water content is relatively high. This is because the drying process on the material has not run perfectly. The ultimate result showed that the EFB had a C content of 54.45%, H content of 5.00%, and O content of 16.27%. The atomic ratio obtained from the ultimate analysis can indicate the amount of calorific value that can be used for certain fuels. The smaller the atomic ratio value contained, the more significant the calorific value contained in a particular fuel. Klason method was carried out to decrease the level of lignin through 4 stages; the lignin content without delignification was resulting into 24.87%, the addition of aquadest was resulting into18.71%, the addition of 5% HCl resulting into 15.34%, and 10% HCl resulting into 14.49%. Delignification of 10% HCl is the pretreatment process before the thermal cracking. The thermal cracking process forms steam; the steam is then condensed to obtain bio-oil. The formed bio-oil was kept to separate the oil from tar. In order to obtain good biofuel quality, adsorption is carried out with zeolite adsorbent, which has been activated with HCL. A comparison of the physical properties of bio-oil before and after adsorption shows a color difference from brownish black to the adsorbed bio-oil, which is distilled to separate the heavy and light fractions. The temperature of 450oC at thermal cracking is close to optimum; when the temperature is increased, the cracking process will be more straightforward and occur optimally. The biofuel produced in this study was tested for its characteristics such as, density (927-1086.68 Kg/m3), kinematic viscosity (1.17-1.43 mm2/s), and flash point (66.00-70, 23oC). The biofuel product produced is dominated by C5-C15 compounds (45.07%) according to the results of GC-MS analysis.

Natural zeolites as host matrices for the development of low-cost and stable thermochemical energy storage materials

Advanced thermal energy storage technologies based on physical adsorption and chemical reactions of thermochemical materials (TCMs) are capable of storing large shares of renewable energy with high energy density. Further research and development is required to improve the performance and reduce the cost of these materials. A promising approach to developing low-cost TCM is to use natural zeolite adsorbents as host matrices in the development of salt-loaded composite TCM. In this study, the thermal properties of various species of low-cost zeolites from natural deposits across Canada were investigated. Two high purity crystal (HPC) zeolites from the Trans Canada (TC-HPC) and Juniper Creek (J-HPC) deposits in British Columbia were determined to have the highest water uptake capacity (0.145 g/g and 0.113 g/g, respectively) and enthalpy of adsorption (408 J/g and 304 J/g, respectively). Despite having approximately half of the water uptake capacity and adsorption enthalpy of the commercially available synthetic zeolite 13X, the cost of thermal energy storage ($CAD/kWhth) of the natural zeolites was determined to be 72–79% lower than that of the synthetic zeolite. Repeated adsorption and desorption experiments demonstrated the hydrothermal stability of the HPC zeolites over multiple charge and discharge cycles. Overall, the experimental results and cost analysis indicate that Canadian HPC zeolites are promising alternatives to synthetic zeolites in the pursuit of low-cost and stable TCM.

Breakthrough Curves Prediction of Selenite Adsorption on Chemically Modified Zeolite Using Boosted Decision Tree Algorithms for Water Treatment Applications

This work describes an experimental and machine learning approach for the prediction of selenite removal on chemically modified zeolite for water treatment. Breakthrough curves were constructed using iron-coated zeolite adsorbent and the adsorption behavior was evaluated as a function of an initial contaminant concentration as well as the ionic strength. An elevated selenium concentration in water threatens human health and aquatic life. The migration of this metalloid from the contaminated sites and the problems associated with its high releases into the water has become a major environmental concern. The mobility of this emerging metalloid in the contaminated water prompted the development of an efficient, cost-effective adsorbent for its removal. Selenite [Se(IV)] removal from aqueous solutions was studied in laboratory-scale continuous and packed-bed adsorption columns using iron-coated natural zeolite adsorbents. The proposed adsorbent combines iron oxide and natural zeolite’s ability to bind contaminants. Breakthrough curves were initially obtained under variable experimental conditions, including the change in the initial concentration of Se (IV), and the ionic strength of solutions. Investigating the effect of these parameters will enhance selenite mobility retardation in contaminated water. Continuous adsorption experiment findings will evaluate the efficiency of this economical and naturally-based adsorbent for selenite removal and fate in water. Multilinear and non-linear regressions approaches were utilized, yet low coefficients of determination values were respectively obtained. Then, a comparative analysis of five boosted regression tree algorithms for a selenite breakthrough curve prediction was performed. AdaBoost, Gradient boosting, XGBoost, LightGBM, and CatBoost models were analyzed using the experimental data of the packed-bed columns. The performance of these models for the breakthrough curve prediction under different operation conditions, such as initial selenite concentration and ionic strength, was discussed. The applicability of these models was evaluated using performance metrics (i.e., Mean Absolute Error (MAE), Root Mean Square Error (RMSE), Mean Absolute Percentage Error (MAPE), and coefficient of determination (R2). The CatBoost model provided the best fit for a breakthrough prediction with a coefficient of determination R2 equal to 99.57. The k-fold cross-validation technique and the statistical metrics verify this model’s accurateness. A feature importance assessment indicated that Se (IV) initial concentration was the most influential experimental variable, while the ionic strength had the least effect. This finding was consistent with the column transport results, which observed Se (IV) sorption dependency on its inlet concentration; simultaneously, the ionic strength effect was negligible. This work proposes implementing machine learning-based approaches for predicting water remediation-associated processes. The significance of this work was to provide an alternative method for investigating selenite adsorption behavior and predicting the breakthrough curves using a machine-based approach. This work also highlighted the importance of management practices of adsorption processes involved in water remediation.

Effect of O2/N2 glow discharge plasma on zeolite extrudates as water adsorbent

The suitable desiccant for olefinic compounds is a hydrophilic zeolite adsorbent with low catalytic activity. In the present study, the surface modification of attapulgite-bounded zeolite A by the N2/O2 glow discharge plasma was investigated. The N2 and O2 plasma treatment was applied individually on prepared extrudates before and after calcination. Plasma treatment increased the specific surface area and pore volume of the extrudates, but did not affect the crystallinity of the samples. It was found that the O2 plasma treatment increased the surface acidity. In contrast, the N2 plasma treatment decreased the acidity. The catalytic performances of untreated and N2 plasma-treated extrudates were evaluated in terms of coke formation by using a reactive alkene (1-butene). The coke formation was reduced by 39% in the N2 plasma-treated samples compared to the untreated sample. Moreover, the water sorption capacity of plasma-treated extrudates was higher (∼ 20%) than the untreated ones due to their higher surface area and pore volume.

AKTIVASI ZEOLIT ALAM SEBAGAI ADSORBEN PEWARNA ALAMI KULIT BUAH NAGA (PITAYA)

Natural zeolite is one of the alternative adsorbents with good absorption capabilities, including in absorbing color. The adsorption ability of zeolite can be increased by the activation process because it can increase the Si/Al ratio and pore size. Dragon fruit peel is a natural material that can be used as a natural dye because it contains betacyanin pigments which are equivalent to synthetic dyes. This study aimed to investigate the characteristics of activated green and brown zeolite and their adsorption ability on natural dyes of dragon fruit peel. Zeolite was activated chemically using 3M HCl solution and physically through a heating process of 500°C, then characterized using XRD and FTIR. The zeolite adsorption process was carried out with variations in contact time of 30, 60 and 90 minutes and variations in the mass of the adsorbent 0.1, 0.3 and 0.5 grams. The results of XRD analysis showed that the green and brown zeolite contained mordenite, nepheline and quartz minerals. The highest percentage of color degradation in the adsorption process was in brown zeolite at 27.70% at a contact time of 90 minutes and 88.2% at an adsorbent mass of 0.5 grams. Differences in brown zeolite before and after adsorption can be seen from the shift in the wavelength of each functional group due to the interaction with dragon fruit peel.

ADSORPSI ASAM LEMAK BEBAS PADA MINYAK JELANTAH DENGAN TiO2/ZEOLIT ALAM

This research was conducted to determine the ability of TiO2/natural zeolite in adsorbing free fatty acids in used cooking oil. The studies included the synthesis of TiO2/natural zeolite adsorbent, characterization, and its application to adsorb free fatty acids with variations of contact time, oil volume, and adsorbent mass. The adsorbents’ functional groups were characterized by FTIR, active site by acid-base titration, and surface area by adsorption of methylene blue. The best character of adsorbent was TiO2/natural zeolite 9:100 which had a basicity active site of 11.6048 x 1020 sites/g and a surface area of ??45.6979 m2/g. The results showed that the optimum adsorption process occurred at a contact time of 60 minutes with an oil volume of 100 mL and an adsorbent mass of 0.30 grams resulting in an adsorption capacity and adsorption efficiency (%EE) of (1,00 ± 0.00) mg/g and (79.57 ± 0.17)%, respectively. The type of adsorption isotherm that occurred was Freundlich isotherm with a correlation coefficient (R2) of 0.9910 and Gibbs free energy (?G0) of -3.5571 kJ/mol, which indicated the adsorption process occurred spontaneously and it was a physical adsorption (heterogeneous and multilayers pores).&#x0D; Keywords: adsorption, adsorption isotherm, free fatty acids, TiO2/natural zeolite, used cooking oil.

A study of the thermal regeneration of carbon and zeolite adsorbents after adsorption of 1-hexene vapor

The adsorption isotherms of 1-hexene (HEX) vapor on BPL and Sorbonorit activated carbons (AC), and HiSiv3000 (HS) zeolite exhibit an almost rectangular shape, which favors the application of the thermal method to regenerate the loaded adsorbent. The minimum desorption energy was estimated in the range of 51–63 kJ/mol. The thermal stability and the possibility of adsorbed particles detection in loaded adsorbents were studied using TGA, XRD and NIR/DRS methods. The maximum temperatures on the DTG desorption curves of 120 °C for HS and 150 °C for AC correspond to the optimal desorption temperatures. These temperatures ensure the safe regeneration of the adsorbent in the air and the recovery of the HEX unchanged. The regeneration degree of the loaded HS calculated with an alternative method based on isotherms on fresh and regenerated adsorbent reaches 75 %, which is in line with the observed changes on NIR/DRS spectra. The obtained results revealed the potential of the still underestimated NIR/DRS spectroscopic method in non-destructive testing of adsorbents in their original shape and size, the possibility of confirming the chemical identity of adsorbed particles, assessing the hydrophobicity of the adsorbent and investigating the mechanism of the adsorbent-adsorbate interaction during the adsorption and thermal regeneration processes.

Development of Zeolite Loaded Mg-La-Fe Ternary (hydr) oxides for Treatment of Low Concentration Phosphate Wastewater

A novel Mg-La-Fe ternary (hydr)oxide magnetic zeolite adsorbent (MLFZ) was prepared using the hydrothermal method and employed for effective phosphate removal in this study. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) indicated that the MLFZ presented an amorphous surface with Mg, Fe, and La dispersed on the surface of the zeolite. The isothermal adsorption and kinetics results showed that the adsorption behavior of the MLFZ was consistent with that of the Langmuir isothermal model and quasi-second-order kinetics model. A relatively fast adsorption of phosphate with a short equilibrium time of 30 min was observed in the kinetics experiment, and the maximum adsorption capacity of the MLFZ was 13.46 mg·g-1 in the equilibrium adsorption isotherm study. The MLFZ showed effective adsorption performance over a wide pH range from 3.0 to 9.0. Moreover, the coexisting ions had an insignificant effect on phosphate adsorption. The MLFZ could easily be recovered using a magnet. After five adsorption-desorption cycles, the phosphate removal efficiency was maintained at approximately 90%. The FTIR, XPS, and Zeta potential analysis confirmed that the adsorption mechanisms were attributed to the surface deposition, electrostatic adsorption, and the inner complex formation by ligand exchange between lanthanum and phosphate. Furthermore, the MLFZ demonstrated high efficiency in scavenging phosphate from a natural pond (phosphate concentration decreased from 0.86 mg·L-1 to 0.013 mg·L-1), indicating that the MLFZ was an ideal material for phosphate management and treatment.

설비공학 분야별 최근 연구 동향: 2021년 설비공학논문집 발표논문에 대한 종합적 고찰

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2021. The purpose of this article is to understand the status of current research issues in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Summary of this paper is follows.<BR> (1) The topics of the paper in the field of building mechanical system were the energy consumption, indoor environment analysis, building energy saving, ventilation system, renewable energy system and law of mechanical facilities.<BR> (2) The topics of the research in the field of indoor environment were the IAQ, ventilation, air cleaning, cooling/heating load, renewable energy, zero-energy building, building energy performance etc.<BR> (3) The research topics in the field of refrigeration in 2021 include robust temperature control of variable speed refrigeration system, R32 liquid-injection showcase vapor compression system, hybrid dessicant dehumidifying system, compressor torque calculation by differential pressure measurement, FAPO zeolite adsorbent, compression-adsorption hybrid refrigeration system and so on.<BR> (4) The topics of the papers published in the field of heat were heat transfer, a heat exchanger and a battery, etc. <BR> (5) The topics of the papers published in the field of heat transfer were the air flow rate inside drum of clothes dryer, the dynamic behavior and thermal performance of a solar water heater, a higher energy density storage system using sensible heat or phase change of water, factors affecting performance characteristics of falling film evaporation using R-1233zd(E) refrigerant and the underground seawater intake system in a power plant.

PURIFICATION OF ETHANOL BY CONTINUOUS ADSORPTION METHOD USING ZEOLITE 3A AND CALCIUM OXIDE

The depletion of oil reserves and the increasing need for fuel have become a problem in the supply of energy sources. One of the efforts to maintain the availability of fuel is to use ethanol fuel grade as an alternative fuel. Continuous adsorption is one method that can purify ethanol up to a concentration of 99.5% (v/v). This study aims to increase the purity of ethanol using adsorbent zeolite 3A and calcium oxide (CaO) with a continuous adsorption method. The feed used is technical ethanol with a concentration of 96% (v/v). The equipment used is a continuous adsorption apparatus with a fixed bed column. Parameters measured during the process were ethanol concentration, feed flow rate, temperature, and pressure. Variations carried out were variations in feed flow rate (5 mL/min, 12 mL/min, and 18 mL/min) and the type of adsorbent (zeolite 3A and CaO). The best continuous adsorption process at 5 mL/min flow rate using zeolite 3A adsorbent with the ethanol product concentration rated up to 99.54% on pycnometer analysis and 99.33% on GC-MS analysis. While using CaO adsorbent, the best results were obtained at 5 ml/min rate, with the highest ethanol product concentration of 99.54% in the pycnometer and 99.33% on GC-MS.

The Effect of Operating Conditions on the Purification of Waste Cooking Oil over a Natural Zeolite Catalyst

The waste of cooking oil is a danger to human health. The Heating of waste cooking oil at high temperatures will cause an increase in free fatty acid (FFA) and peroxide number in the oil. Therefore, waste cooking oil needs to be processed before being reused. This paper studies the effect of operation conditions on the purification of waste cooking oil over a natural zeolite catalyst. The stage of the purification process is despicing, neutralization, and bleaching process. The despicing process injected the steam to remove impurities. The effect of the mass flow rate of oil at 1.051; 0.456 and 0.139 Kg/s on FFA value was studied. After that, the neutralization and bleaching process. The Bleaching process was performed using zeolite adsorbent. The results show that the purification method of waste cooking oil decreases of the color of oil, free fatty acid, and peroxide value. In this study, the best performance of the despicing process at the mass flow rate of the oil is 0.139 Kg/s, a temperature of 60°C with 500 rpm stirring for the neutralization process and bleaching process of natural zeolite. The value of free fatty acid content (FFA) is 2.22 mg. KOH/mg fat, peroxide is 6.98 mekO 2 /kg, color degradation is 66.93% and water content is 0.32% (w/w).

Ammonium continuous removal by zeolite P synthesized using fly ash combined with bacteria in aqueous solution.

The new composite product synthesized by zeolite P and bacteria consisting of nitrobacteria and denitrobacteria can efficiently and continuously remove ammonium in solution through zeolite adsorption and bacteria degradation. In this study, we used fly ash to prepared zeolite P, and then combined bacteria to synthesize the composite product. The adsorption efficiency and mechanism of products for ammonium were further studied by batch and dynamic experiments, and adsorption model. The zeolite P with a relative crystallinity of 84.7% was synthesized using fly ash by an alkali fusion-hydrothermal method. The synthetic zeolite P could combine with bacteria to be prepared an integral adsorption composite that had hierarchical pore structure including macropores, mesopores, and micropores, and its maximum compressive strength reached 106.2 N. The zeolite P could remove ammonium from solution, and Freundlich, Temkin, and Dubinin-Radushkevich models as well as thermodynamic models all showed that the ammonium adsorption by zeolite was mainly physical adsorption. Thus, the adsorbed ammonium was easy to be desorbed and became the nitrogen source for bacteria in composites. By batch experiments, the ammonium adsorption rate of composite product was significantly improved (P < 0.05) compared with zeolite P due to zeolite adsorption and the bacteria degradation. Through dynamic experiments, the composite product could efficiently and continuously remove ammonium from solution than zeolite P and bacteria alone. Therefore, the composite product could form a stable system for the adsorption, desorption, and degradation of ammonium in solution.

Application of the Dubinin–Radushkevich–Astakhov equation to calculate gases isotherms on zeolite adsorbents (on example of H2, CO2, CO, CH4, N2 adsorption on 13X and 5A)

ABSTRACT The paper demonstrates the prospects of using an approach for calculating adsorption isotherms of gases on micropore industrial zeolites based on the example of H2, CO2, CO, CH4, N2 adsorption on 13X and 5A zeolites using the Dubinin–Radushkevich–Astakhov (DRA) equation. Experimental adsorption isotherms of H2, CO2, CO, CH4, N2 gases on 13X and 5A zeolites of various manufacturers have been obtained, as well as ranges of the limiting adsorption volume and characteristic adsorption energy have been established. It made it possible to correctly calculate isotherms using the DRA equation in the temperature range 293–323 K and pressure range 0–30 atm. The paper proposes and solves the optimization problem of determining affinity coefficients, which allows the calculation of gas adsorption isotherms on zeolites using only one experimental isotherm of standard gas N2. The mismatch between the experimental isotherms and those calculated by the DRA equation is 14.69% for H2 (maximum) and 1.81% for CO2 (minimum). This approach makes it possible to significantly reduce the number of necessary expensive experiments in comparison with the traditional approach (using the Langmuir equations or equations derived from it), at the same time providing acceptable accuracy for practice.

Refining of Fish Oil from Fish Meal Processing By-product Using Zeolite and Bleaching Earth

As a by-product of the fish meal processing by-product industry, fish oil is a material that has the potential to be reused if it undergoes further processing. What can be done is the bleaching process. This study aims to determine the quality of fish oil before and after the addition of adsorbent, obtain information on the best bleaching process conditions, determine the effect of the best type and concentration of adsorbent on the quality of fish oil, obtain the best adsorbent and concentration. Crude fish oil is weighed and heated. Then, when the temperature has reached 55-60 °C, adsorbents with various concentrations are added. The oil was then reheated and stirred at 80 °C for 30 minutes. After that, the oil was centrifuged at 6500 rpm for 20 minutes. The best type and adsorbent for the bleaching process was obtained using zeolite adsorbent with a concentration of 5%. The interaction of adsorbent type and concentration significantly affected each test parameter of yield, density, viscosity, free fatty acid content, acid number, peroxide number, total oxidation number, and p-anisidine number on the quality of fish oil.

Experimental investigation of dehumidification and regeneration of zeolite coated energy exchanger

Zeolite desiccant particles are well known for their strong affinity to adsorb water vapor molecules; however, they require significant regeneration energy to be created. This paper presents an experimental study of the adsorption and regeneration processes of a monolayer zeolite for indoor dehumidification to the 13X zeolite beads with a 4 × 8 mesh bead size and a pore opening 10 A⁰ were used as this monolayer. An experimental investigation was conducted to determine the effects of the relative humidity, temperature, and air flow rate on the adsorption and regeneration processes. The results show the effectiveness of the monolayer coating method and the relative humidity significantly affects the adsorption process, and that the airflow rate surrounding and through the zeolite beads increases the adsorption and desorption of the water vapor molecules. In the absence of the meniscus radius formation due to the monolayer arrangement prevents external condensation. With an airflow rate of Re = 1773, the full adsorption process at a relative humidity of 99% was obtained within 37 min; meanwhile, the regeneration process proceeded at 100 °C within 66 min. The adsorption time was reduced by 27% and 43% as the Reynold number increases to 2586 and 3325, respectively. Likewise, the effectiveness of the regeneration time is decreased by 0.07% and 14% within the same Reynold number increases. Results obtained from this research can be used to guide the future development of polymer-coated energy exchangers.

Removal of Iron and Manganese in Acid Mine Drainage Using Natural Zeolite

The environmental problem that often occurs in coal mining is acid mine drainage which can pose a serious threat to human health, animals and ecological systems. Acid mine drainage contains heavy metal contaminants such as iron and manganese. The purpose of this study was to determine the adsorption equilibrium carried out using natural zeolite adsorbents type mordenite from Klaten, Central Java. The application of natural zeolite with a volume of 100 mL synthetic acid mine drainage with concentrations of Fe 41.97 mg/L, Mn 21.75 mg/L and variations in dose of natural zeolite (2, 4, 6, 8, and 10 grams). The highest percent removal was at a dose of 10 grams of zeolite resulted in % removal of 97.94 % for Fe and 67.81 % for Mn. The results obtained using Langmuir and Freundlich adsorption isotherms. The results followed the Freundlich isotherm model with an adsorption parameters Kf = 0.427 mg/g, R2 = 0.991, n = 1.610 Fe metal and Mn metal adsorption parameters are Kf = 0.006 mg/g, R2 = 0.9971, and n = 0.578

Gas Adsorption in Zeolite and Thin Zeolite Layers: Molecular Simulation, Experiment, and Adsorption Potential Theory.

Molecular simulations and experiments are used to investigate methane adsorption in bulk and thin layers of MFI zeolite (silicalite-1). After comparing the theoretical adsorption data obtained using Grand Canonical Monte Carlo simulations for bulk MFI at various temperatures against experiments, zeolite layers with different crystalline orientations and levels of surface flexibility are considered. The data obtained for such prototypical systems allow us to rationalize both the qualitative and quantitative impact of external surface in nanoporous solids. In particular, due to strong confinement in zeolite pores, methane is found to adsorb at low pressures in the core of the zeolite while external surface adsorption occurs at pressures where the internal porosity of zeolite is saturated. Using Polanyi's adsorption potential theory, which is derived here from Hill's general scheme for adsorption, we provide a simple thermodynamic formalism to predict consistently adsorption both in the internal porosity and at the external surface of nanoporous solids. While this seminal theory has been already applied for gases in nanoporous solids, its extension to describe both surface and volume adsorption is important to provide a general rational framework for fluid adsorption in finely divided materials. We also discuss the applicability of this formalism for gas adsorption data under supercritical conditions.

Removal of polystyrene nanoplastics from aqueous solutions by a novel magnetic zeolite adsorbent

Nanoplastics (NPs) made from plastic fragments have attracted wide attention due to their extensive distribution and potential harm to organisms. In this study, the zeolite as raw samples, a new magnetic zeolite (MZ) adsorbent was successfully synthesized by co-precipitation method to remove polystyrene nanoplastics (PSNPs). The adsorption amounts of PSNPs by MZ sample enhanced with the increases of PSNPs initial concentration and the temperature in aquatic solutions. The maximum equilibrium adsorption amount could achieve 34.2 mg/g. The solution pH, co-existing anions, and ionic strength could significantly affect the removal of PSNPs. Comparing different adsorption models, it displays that the pseudo-second-order and Sips models could well fit the adsorption process of PSNPs by MZ. Based on the XPS analysis, the iron oxide functional groups exhibit an important role in capturing PSNPs. The potential adsorption mechanisms of PSNPs are summarized as electrostatic attraction, complexation, and π-π conjugation. Overall, the synthesized magnetic material can effectively remove NPs from aqueous solutions.