Adsorption最新文献

Perfluorinated compounds (PFCs) cause environmental pollution and serious health issues. Therefore, magnetic fluorinated porous carbons (M-FPCs) derived from the carbonization and further fluorination of Fe-Zr MOFs were used as novel adsorbents to investigate the possibility of PFC removal from wastewater. Investigation of the adsorption behavior of PFCs on M-FPCs revealed that the isotherms conformed to the Langmuir model and kinetics fit the pseudo-second-order model. Simulations using the Weber–Morris and Boyd diffusion models indicated that the adsorption of PFCs on M-FPCs involved external mass transfer first, followed by intraparticle diffusion, where film diffusion was the primary controlling process. M-FPCs with maximum adsorption ranging from 518.1 to 919.3 mg g^− 1 for studied PFCs were adopted to remove PFCs from simulated wastewaters of textile mill and leather factory. Up to 98.1–100.0% of PFCs were removed within 15 min, and the residual levels of PFCs reached drinking water standards after treatment, which suggests the promising application of M-FPCs in the removal of PFCs from wastewater.

Automated sorption balances are widely used for characterizing the interaction of water vapor with hygroscopic materials. These instruments provide an efficient way to collect sorption isotherm data and kinetic data. A typical method for defining equilibrium after a step change in relative humidity (RH) is using a particular threshold value for the rate of change in mass with time. Recent studies indicate that commonly used threshold values yield substantial errors and that further measurements are needed at extended hold times as a basis to assess the accuracy of abbreviated equilibration criteria. However, the mass measurement accuracy at extended times depends on the operational stability of the instrument. Published data on the stability of automated sorption balances are rare. An interlaboratory study was undertaken to investigate equilibration criteria for automated sorption balances. This paper focuses on the mass, temperature, and RH stability and includes data from 25 laboratories throughout the world. An initial target for instrument mass stability was met on the first attempt in many cases, but several instruments were found to have unexpectedly large instabilities. The sources of these instabilities were investigated and greatly reduced. This paper highlights the importance of verifying operational mass stability of automated sorption balances, gives a method to perform stability checks, and provides guidance on identifying and correcting common sources of mass instability.

In this study, mesoporous Montmorillonite-Silica composites prepared by using different amount Alginate as sacrificial template, for removal of Rhodamine B is investigated. By alternating Alginate amount it is aimed to switch the porosity of adsorbents thus the adsorption capacities of adsorbents. Synthesized adsorbents had been characterized by using Scanning Electron Microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and N₂-Ads/Des techniques. It is observed that beside the decrease in the micropore volume, the total pore volume of the adsorbents increased with the increasing of used Alginate amount. The total pore volumes of adsorbents synthesized with different Clay/Alginate ratio (10, 5, 1) were found as 0.116, 0.172, and 0.178 cm³/g, respectively. Batch adsorption studies showed that the maximum removal efficiencies were obtained at acidic conditions and the adsorbents had better fit with Freundlich isotherm. Qm values obtained from Langmuir isotherm were found as 24.47, 31.97 and 28.48 mg/g for synthesized adsorbents. Also, adsorption kinetic studies showed that for all adsorbents, experimental data had good fit to the pseudo-second order kinetics model. The model parameters were found as 5.9,6.3 and 6.5 (10^–3 g/ (mg min). Thermodynamic parameters were also investigated in the study. Negative ∆G^o values pointed out that the adsorption of RhB onto synthesized adsorbents was favorable process. Positive values of ∆Ho and ΔS indicated that the adsorption of RhB on adsorbents were endothermic and rising of randomness during the adsorption of RhB on the surface of the adsorbent. Adsorbents could be recovered at least five times without significant decrease in adsorption capacity.

The study of the physicochemical properties of water and the removal of water contaminants using an active adsorbent material is a vital approach today. The purpose of this study is to modify orange peel (OP) using polyaniline (PANI) via in situ oxidative polymerization method and characterize it for wastewater treatment applications. The properties of water were analyzed according to the standard guideline published by APH before the adsorption study. The proposed materials were characterized by SEM, FTIR, and UV–VIS spectroscopy. The modification of orange peel using polyaniline was confirmed by electronic transition and stretching vibration peaks obtained from FT-IR and UV–Vis spectroscopies and its morphologies from SEM. The results of most of the physicochemical properties, nutrients, and heavy metals were above the acceptable range for wastewater discharge limits set by FAO, WHO, and EEPA. The Cu and Zn adsorption performance of as-synthesized materials was studied and depicted a high adsorption capacity for copper (176.9 mg/g) and zinc (151.3 mg/g) in wastewater solutions. When all parameters were optimized (pH at 6, contact time at 40 min, temperature at 300 K, and 1 gr of PANI-OP), 90.03% removal of copper and 85% (pH at 4, contact time at 60 min, temperature at 300 K, and 1 gr of PANI-OP) removal of zinc were observed. The adsorption equilibriums of both copper and zinc were best described by the Freundlich isotherm model. Therefore, the synthesized novel material PANI-OP is a promising candidate for the removal of Cu and Zn from wastewater.

This study aimed to evaluate the production of high purity oxygen (90–95%) through experiments in a PSA/VSA unit and develop a mathematical model to describe the dynamic behavior of the process. Different operational parameters and the dead volume were investigated for their impact on process performance. The experiments used a laboratory-scale unit filled with beads of a commercial LiX zeolite to obtain breakthrough and PSA/VSA data for model validation. Equilibrium isotherms of pure oxygen and nitrogen were measured at 288, 298 and 313 K for the pressure range of 0 to 3 bar. Single and multicomponent breakthrough curves were obtained at 298 K. Synthetic air (grade 5.0 purity, excluding argon) with a composition of 20% (± 0.5%) O₂ and 80% (± 0.5%) N₂ was used in the PSA/VSA experiments. A novel approach was developed using the mathematical model designed to simulate PSA/VSA cycles to account for the dead volume effects commonly found in units of this type. The model was implemented and solved using gPROMS® software. The simulation data matched well with the experimental data, accurately representing histories of concentration, pressure, temperature, and purity variations during the process. The validated model revealed optimal operating conditions for a VSA unit: 7.5 s adsorption time, 1.5 bar adsorption pressure, 0.1 bar desorption pressure, and a flow rate of 1 SLPM, producing a purity of approximately 94% and a recovery of about 20%. Increasing the adsorption duration negatively affected the oxygen purity but positively influenced process recovery and productivity. Adding an equalization stage improved process recovery by 18.9% for PSA and 14.5% for VSA. Additionally, increased dead volume in the column had adverse effects on purity, productivity, and recovery for both PSA and VSA units.

H₂S and CO₂ are considered two main impurities of natural gas and biogas. These impurities must be removed in order to achieve economic and environmental restrictions. Adsorption is a promising technology studied to achieve this goal. Among alternative adsorbents studied to capture H₂S and CO₂, porous aromatic frameworks (PAFs) had shown potential application because of suitable selectivity and remarkable adsorption capacity. However, H₂S and CO₂ adsorption/desorption data on PAF-30 are still scarce in literature. Thus, in this work, H₂S (up to 2.5 bar) and CO₂ and CH₄ (up to 50 bar) adsorption/desorption isotherms on PAF-30 were determined at 293, 303 and 313 K for the first time in literature. PAF-30 was synthesized and characterized by XRD, FTIR, ¹³C-NMR, Ar and CO₂ physisorption, SEM, TEM, TGA and DSC analyzes. Then, adsorption isotherms were determined gravimetrically. Experimental data were modelled with Jensen-Seaton equation. The results indicated that PAF-30 presents adsorption capacities in the order H₂S > CO₂ > CH₄. Adsorption/desorption branches do not match for systems studied, due to a hysteresis effect. Adsorption capacity decreases with temperature, indicating that physisorption is the main phenomenon observed. Experimental data were represented by Jensen-Seaton model. Thermodynamic analysis showed that all systems are exothermic and spontaneous. Working capacities obtained indicate that temperature reduces the performance for gas purification and that H₂S systems are affected by hysteresis loop. Moreover, cyclic adsorption results show that PAF-30 has potential to be applied and further studied in PSA simulations for H₂S and CO₂ capture under high-pressure conditions.

The carbonization temperature of carbon precursors before their activation is an important factor affecting the porous structure and properties of the resulting activated carbons. In this work сorrelation between the textural and adsorption properties of asphalt-based porous carbons and the carbonization temperature has been found. Additionally, the optimal carbonization temperature, and reasons why the carbonization temperature affects the main textural characteristics of the activated carbon were established. A series of porous carbons has been prepared from petroleum asphalt by a two-stage method, including carbonization of asphalt at different temperatures from 450 to 800 °C and KOH activation. To reveal the reasons of the correlation the carbonized samples were studied by TG-DTG, IR-Fourier, TEM methods. It is shown that the carbonization temperature effects on the structural defects, distance between the graphene layers, the reactivity and thermal stability of the carbonized asphalts. These specificities contribute to formation of porous structures of the activated carbons. The carbonization temperature 500–600 °С of the petroleum asphalt is found to be the optimal for further activation. The KOH activation of the petroleum asphalts carbonized at 500–600 °С provides microporous carbon with the high specific surface area (about 2000 m²g^-1) and the CO₂ uptake (3.3 mmolg^-1). Additionally, the specific surface area of the activated carbons is shown can be predicted from the temperature of 50% (T_50%) mass loss of the carbonized petroleum asphalt. The linear dependence of the T_50% on BET surface area can be fitted by T_50%=640–0.424S_BET with determination coefficient R² equal to 0.96.

Water adsorption capacities of various adsorbents reported in the literature were investigated to define a hydrophobicity index that was plotted vs. water capacity. In this plot, logarithmic curves were proposed to be used as indicators of performance limits of adsorbents, especially for adsorption heat pumps. In spite of their useful adsorption properties, zeolites generally exhibited quite low hydrophobicity, remaining well below the logarithmic curve. In this study, the use of composites of zeolite NaY was examined both theoretically and experimentally for improvements in the water capacity and hydrophobicity. Salt impregnation and hydrothermal synthesis experiments were performed to prepare composites of zeolite NaY with LiCl/MgCl₂ salts and activated carbon, respectively. Water capacity and hydrophobicity of zeolite NaY composites were generally superior to those of pure zeolite. Zeolite composites may be advantageous for enhancing adsorption capacity and hydrophobicity of zeolites while eliminating low stability and slow adsorption kinetics of other adsorbents. Interface between two different phases might indicate another opportunity to provide improved adsorption properties for zeolite composites.

Ion exchange is the reversible exchange of ions in which there is no significant change in the solid structure. Zeolites are aluminosilicates with a defined structure, including cavities occupied by cations and water molecules, both with great freedom of movement, which makes cation exchange possible. In this study, small-pore zeolites chabazite (CHA) and clinoptilolite (CLI) were ion-exchanged with potassium. Then, the samples were characterized by N₂ isotherms at 77 K, CO₂ adsorption microcalorimetry at 298 K, and water vapor isotherms at 313 K. A mathematical model was applied to evaluate the adsorption kinetics for water vapor uptakes. Textural analysis showed that the ion exchange with potassium decreased the porosity of both zeolites, but CO₂ microcalorimetric data showed that these samples had higher CO₂ adsorption enthalpy, indicating a greater sorbate-sorbent interaction as compared to the pristine zeolites. Uptake rate curves suggest water diffusion is not appreciably altered after ion exchange. Interestingly, despite the larger size of K⁺ cations as compared to Na⁺, effective diffusion time constant is on order of magnitude larger for the potassium-loaded CLI very likely due to the leaching of other contaminants upon ion-exchange.