Multi step energy transfer between three Si_LTL and SiGe_LTL zeolite-loaded dyes

We report a novel potential light-harvesting antenna material constructed with three dyes loaded on two types of zeolite LTL (SiGe_LTL and Si_LTL). Fluorescence resonance energy transfer (FRET) occurs from acridine hydrochloride (Ac) to Thionine acetate (Th) via Acriflavine hydrochloride (AF), which acts as an antenna to receive and transfer energy from Ac to Th. We compared multistep FRET systems based on dye-loaded SiGe_LTL paired with an Si_LTL-based system. Our results show that in both cases, FRET efficiency increases with Th loading and decreases with increasing AF loading. Moreover, the zeolite LTL microenvironment causes a red shift in the fluorescence spectra of the three SiGe_LTL-loaded-dyes compared to those of the Si_LTL-based dyes.     

Tailoring Chitosan/LTA Zeolite Hybrid Aerogels for Anionic and Cationic Dye Adsorption

Chitosan (CS) is largely employed in environmental applications as an adsorbent of anionic dyes, due to the presence in its chemical structure of amine groups that, if protonated, act as adsorbing sites for negatively charged molecules. Efficient adsorption of both cationic and anionic dyes is thus not achievable with a pristine chitosan adsorbent, but it requires the combination of two or more components. Here, we show that simultaneous adsorption of cationic and anionic dyes can be obtained by embedding Linde Type A (LTA) zeolite particles in a crosslinked CS-based aerogel. In order to optimize dye removal ability of the hybrid aerogel, we target the crosslinker concentration so that crosslinking is mainly activated during the thermal treatment after the fast freezing of the CS/LTA mixture. The adsorption of isotherms is obtained for different CS/LTA weight ratios and for different types of anionic and cationic dyes. Irrespective of the formulation, the Langmuir model was found to accurately describe the adsorption isotherms. The optimal tradeoff in the adsorption behavior was obtained with the CS/LTA aerogel (1:1 weight ratio), for which the maximum uptake of indigo carmine (anionic dye) and rhodamine 6G (cationic dye) is 103 and 43 mg g⁻¹, respectively. The behavior observed for the adsorption capacity and energy cannot be rationalized as a pure superposition of the two components, but suggests that reciprocal steric effects, chemical heterogeneity, and molecular interactions between CS and LTA zeolite particles play an important role.     

Adsorption of CO2 on Zeolite 13X and Activated Carbon with Higher Surface Area

In this work, adsorption isotherms and adsorption kinetics of CO₂ on zeolite 13X and activated carbon with high surface area (AC-h) were studied. The adsorption isotherms and kinetic curves of CO₂ on the adsorbents were separately measured at 328 K, 318 K, 308 K, and 298 K and with a pressure range of 0–30 bar by means of the gravimetric adsorption method. The mass transfer constants and adsorption activation energy E_a of CO₂ on the adsorbents were estimated separately. Results showed that at very low pressure the amounts adsorbed of CO₂ on the zeolite 13X was higher than that on the AC-h, while at higher pressure, the amounts adsorbed of CO₂ on the AC-h was higher than that on the zeolite 13X since the AC-h has a larger surface area and a larger total pore volume compared to the zeolite 13X. The adsorption kinetics of CO₂ can be well described by the linear driving force (LDF) model. With the increase of temperature, the mass transfer constants of CO₂ adsorption on both samples increased. The adsorption activation energy E_a for CO₂ on the two adsorbents decreased with the increase of pressure. Furthermore, at low pressure the E_a for CO₂ adsorption on the zeolite 13X was slightly lower than that on the AC-h, while at higher pressure the E_a for CO₂ adsorption on the zeolite 13X was higher than that on the AC-h.     

n-Octane aromatization on Pt-containing non-acidic large pore zeolite catalysts

Platinum catalysts supported on the potassium-form of different large-pore zeolites (i.e. K-LTL, K-BEA, K-MAZ, and K-FAU) have been tested for n-octane aromatization at 500 °C. All catalysts were prepared by the vapor phase impregnation (VPI) method. It was found that the Pt/K-LTL catalyst exhibit a better aromatization performance than the other zeolite catalysts. However, due to secondary hydrogenolysis, the C8 aromatics produced inside the zeolite are converted to benzene and toluene. By contrast, a non-microporous Pt/SiO₂ catalyst did not present the secondary hydrogenolysis. Therefore, despite a lower initial aromatization activity, Pt/SiO₂ results in higher selectivity to C8 aromatics than any of the other zeolite catalysts. All fresh catalysts were characterized by hydrogen chemisorption and FT-IR of adsorbed CO. In addition, the residual acidity of the supports was analyzed by temperature programmed desorption (TPD) of ammonia. In agreement with previous studies, it was found that after reduction at either 350 or 500 °C, the Pt/K-LTL showed much higher Pt dispersion than other catalysts. It is known that the structure of L zeolite can stabilize the small Pt clusters inside the zeolite channel. By contrast, FT-IR indicated that a large fraction of platinum clusters were located outside the zeolite channels in the case of Pt/K-BEA and Pt/K-MAZ catalysts.     

Facile preparation of agaraldehyde chitosan-based composite beads as effectual adsorbent especially towards amido black

Agaraldehyde and chitosan (CHI) functional beads as dye adsorbent were prepared under aqueous medium under ambient temperature and used for removing seven dyes from aqueous solutions. The resulting porous CHI-A_ald (R-A_ald-CHI) bio-beads were characterized by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and scanning electron microscope. The dye removal efficiency was studied using seven dyes (amido black [AB], bromophenol blue, crystal violet, bismarck brown, cotton blue, methyl orange, methylene blue), but detail study was done on AB. AB adsorption was followed the Langmuir-isotherm and pseudo-second order kinetics. The effects of adsorption parameters were investigated, and maximum AB 1506 mg/g was adsorbed under the optimum conditions. The linear and nonlinear forms of Langmuir and Freundlich isotherms and two kinetic models pseudo-first-order and pseudo-second-order were studied. The results show that adsorption follow both isotherm model while for kinetics of adsorption follow pseudo-second-order. The results of this work showed that R-A_ald-CHI was encouraging adsorbent to remove dyes from wastewater, especially AB.     

Removal of Acid Dyes from Aqueous Solutions using Chemically Activated Carbon

Abstract

Textile dyes (Acid Yellow 17 and Acid Orange 7) were removed from its aqueous solution in batch and continuous packed bed adsorption systems by using thermally activated Euphorbia macroclada carbon with respect to contact time, initial dye concentration, and temperature. The activated carbon was prepared using a cheap plant-based material called Euphorbia macroclada, which was chemically modified with K₂CO₃. Lagergren-first-order and second-order kinetic models were used to fit the experimental data. Equilibrium isotherms were analyzed by Langmuir and Freundlich isotherms. Equilibrium data fitted well the Langmuir model in the studied temperature (25–55°C) ranges. The maximum adsorption capacity of AY17 and AO7 onto activated carbon was found to be 161.29 and 455 mgg^?1, respectively by Langmuir isotherm at 55°C. Breakthrough curves for column adsorption have also been studied. The desorption of dyes has been experimentally investigated using NaOH solution of pH 11.     

Bamboo charcoal modified with Cu2+ and 3-aminopropyl trimethoxy silane for the adsorption of acid fuchsin dye: Optimization by response surface methodology and the adsorption mechanism

The bamboo charcoal modified with Cu²⁺ and 3-aminopropyl trimethoxy silane (BC-Cu/Si-NH₂) was synthesized and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, and surface acid–base potentiometric titration. The adsorption for acid fuchsin (AF) dyes onto BC-Cu/Si-NH₂ was investigated. Moreover, response surface methodology was performed to optimize the process parameters including pH, initial dye concentration, adsorbent dosage, and temperature. The results presented that the adsorption process was mainly influenced by initial AF concentration and adsorbent dosage. Isotherm studies revealed that the adsorption data fitted well with the Sips model and Dubinin–Radushkevich (D–R) model, which indicated the monolayer, homogeneous, and physical nature of the adsorption process. The maximum adsorption capacity calculated from D–R model could approach approximately to 14.91 mg g⁻¹ at 40 °C, and the maximum adsorption capacity of Sips reached to 10.77 mg g⁻¹ at 40 °C. The kinetic experimental data matched well with Spahn and Schlunder model as well as pseudo-second-order model. In addition, intraparticle diffusion was not the only rate-controlling step of adsorption process. Thermodynamic parameters revealed the feasibility, spontaneity, and endothermic nature of adsorption. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47728.     

Sorption of nitrogen,oxygen, and argon in Cd (II) exchanged zeolite X: volumetric equilibrium adsorption and grand canonical Monte Carlo study

The adsorption of nitrogen, oxygen and argon has been studied in cadmium (II) cations exchanged zeolite X at 288.2 and 303.2 K. Experimentally measured adsorption isotherms are compared with theoretically calculated data using grand canonical Monte Carlo (GCMC) simulation. Nitrogen showed higher adsorption capacity and selectivity than oxygen and argon in these zeolite samples. The cadmium exchanged zeolite X was showed that increased adsorption capacity for nitrogen, oxygen, and argon with increase in Cd (II)-exchange levels, indicating as charge density increases adsorption capacity also increase. Isosteric heat of adsorption data showed stronger interactions of nitrogen molecules with cadmium cations in zeolite samples. These observations have been explained in terms of higher electrostatic interaction of nitrogen with extra framework zeolite cations. The selectivity of oxygen over argon is explained in terms of its higher interaction with Cd (II)-exchanged zeolites than argon molecules. The selectivity of N₂/O₂ of cadmium-exchanged zeolite X is better than only sodium containing zeolite-X. Heats of adsorption and adsorption isotherms were also calculated using GCMC simulation algorithm. Simulation studies expectedly show the proximity of nitrogen molecules to the locations of extra framework sodium and cadmium cations.     

Adsorption characteristics of superplasticizers on cement component minerals

Adsorption characteristics of various superplasticizers on portland cement component minerals were investigated. Adsorption isotherms of various types of superplasticizers and ζ-potentials of cement component minerals at the maximum adsorption of the superplasticizers were measured. The value of the adsorption isotherm was calculated from the amount of the superplasticizer adsorbed on a cement component mineral in an equilibrated solution. The maximum amounts of adsorption and the adsorption isotherms varied with types of component mineral and superplasticizer. For all types of superplasticizers, a larger amount of superplasticizer was adsorbed on C₃A and C₄AF than C₃S and C₂S. However, the equilibrated concentration of each superplasticizer at the maximum adsorption was not influenced by types of superplasticizer. Without superplasticizer, C₃S and C₂S had negative ζ-potential. On the contrary, C₃A and C₄AF had positive ζ-potential. Therefore, accelerated coagulation of cement particles might occur due to their electrostatic potentials that are opposite each other. However, all component minerals of cement had negative ζ-potential when they were mixed with any superplasticizer. Fluidity of fresh cement paste is improved due to electrostatic repulsion acting between particles.     

Adsorption behavior of methylene blue on amine-functionalized ordered mesoporous alumina

Amine-functionalized ordered mesoporous alumina (NH₂-OMA) was synthesized through a facile and reproducible method. Its organic dyes adsorption characteristics, including adsorption isotherms, adsorption kinetics, the stability and reusability of the adsorbents were investigated. This material exhibited strong affinity to methylene blue and extremely high adsorption capacity. The maximum adsorption capacity value reached 657.89 mg g^?1. Adsorption kinetics was best described by the pseudo-second-order model. Equilibrium data were well fitted to the Langmuir isotherm model.     

Adsorption of Cr (VI) Oxyanions onto Modified Wood Pulp

A new adsorbent was prepared from wood pulp (WP) after reaction with epichlorohydrin and dimethylamine in the presence of pyridine and N,N-dimethylformamide (DMF). The adsorption of Cr (VI) from aqueous solutions by the so-prepared wood pulp adsorbent (WP-A) was investigated. Various factors affecting adsorption, such as pH, adsorbent concentration (1–5 g/L), agitation time (5–60 min), and Cr (VI) concentration (50–700), were taken into consideration. The adsorption of Cr (VI) onto (WP-A) was found to be pH-dependent and maximum adsorption was obtained at pH 3. The adsorption data obeyed Langmuir and Freundlich adsorption isotherms. The Langmuir adsorption capacity (Q_max) was found to be 588.24 mg/g. Freundlich constants, K_F and n, were found to be 55.03 and 2.835, respectively.     

Adsorption of different dyes from aqueous solution using Si-MCM-41 having very high surface area

Adsorption characteristics of four different dyes Safranin O (cationic), Neutral Red (neutral), Congo Red (anionic) and Reactive Red 2 (anionic) on Si-MCM-41 material having very high surface area are reported. The surface morphology of Si-MCM-41 material before and after adsorbing dye molecules are characterised by FTIR, HRXRD, nitrogen adsorption–desorption isotherms, FESEM, and HRTEM. The adsorption capacities of Si-MCM-41 for the dyes followed a decreasing order of NR > SF > CR > RR2. The adsorption kinetics, isotherm and thermodynamic parameters are investigated in detail for these dyes using calcined Si-MCM-41. The kinetics and isotherm data showed that both SF and NR adsorb more rapidly than CR and RR2, in accordance with pseudo-second-order kinetics model as well as intraparticle diffusion kinetics model and Langmuir adsorption isotherm model respectively. The thermodynamic data suggest that the dye uptake process is spontaneous. The high adsorption capacities of dyes on Si-MCM-41 (q_m = 275.5 mg g^?1 for SF, q_m = 288.2 mg g^?1 for NR) is explained on the basis of electrostatic interactions as well as H-bonding interactions between adsorbent and adsorbate molecules. Good regeneration capacity is another important aspect of the material that makes it potent for the uptake of dyes from aqueous solution.     

Mechanism of retention of hydrocarbons in reservoir rocks. Role of polar compounds and effect of additives

Evidence is given for the involvement of hydrophobic interactions in the retention of hydrocarbons in oil fields. A prerequisite is that the surface of the reservoir rock has to be hydrophobic. This was obtained through adsorption of lipophilic polar compounds. The isotherms for the adsorption of dodecylamine hydrochloride and N-hexadecylpyridine hydrochloride were plotted. The treated quartz could take up large amounts of toluene. The relationships between some features of the isotherms and the retention phenomenon have been analysed. The effect of water-structuring additives (e.g. LiF, CaCl₂, NaF and guanidine hydrochloride) on the recovery of hydrocarbons was investigated by means of static and dynamic methods.     

正己烷在5A分子筛上高温吸附/脱附及扩散性能

采用智能质量分析仪IGA,在较高温度(150—300℃)下,测定5A分子筛对正己烷的吸附/脱附等温线,考察吸附温度对吸附等温线的影响,研究改性5A分子筛的二次孔结构与正己烷吸附/脱附及扩散性能的关系。结果表明:5A分子筛对正己烷的吸附等温线随着吸附温度的升高优惠程度逐渐降低,在300℃下,5A分子筛对正己烷吸附等温线接近线性,压力从14 kPa降至1.4 kPa,被5A分子筛吸附的正己烷可脱附出45.95%;在200℃下,改性5A分子筛(5A-11)对正己烷的脱附质量比是未改性(5A-1)的3.5倍;正己烷在5A-11分子筛上的脱附扩散系数为8×10-13m2/s,约是未改性的20倍;5A-11分子筛拥有较小的二次孔孔径和较为合理的大孔分布,使其对正己烷有着良好的脱附性能。     

Removal of 4-nitro-phenol from wastewater using synthetic zeolite and kaolin clay

Adsorption techniques are widely used to remove certain classes of pollutants from wastewater. Phenolic compounds represent one of the problematic groups. Na-Y zeolite has been synthesized from locally available Iraqi kaolin clay. Characterization of the prepared zeolite was made by XRD and surface area measurement using N₂ adsorption. Both synthetic Na-Y zeolite and kaolin clay have been tested for adsorption of 4-Nitro-phenol in batch mode experiments. Maximum removal efficiencies of 90% and 80% were obtained using the prepared zeolite and kaolin clay, respectively. Kinetics and equilibrium adsorption isotherms were investigated. Investigations showed that both Langmuir and Freundlich isotherms fit the experimental data quite well. On the other hand, the adsorption of phenol was found to obey first-order kinetics.     

Characterization and selectivity for methane and carbon dioxide adsorption on the all-silica DD3R zeolite

Clathrasil Deca-dodecasil 3R (DD3R) zeolite was synthesized in this study. Then, adsorption properties of carbon dioxide and methane were examined on the all-silica DD3R zeolite. Pure component adsorption isotherms are reported at temperatures of 273–348 K and pressures as high as 3 MPa. The isotherms follow a typical Type-I shape according to the Brunauer classification. They are well described using Langmuir and multi-site Langmuir models. Isosteric heats of adsorption and Henry’s Law constants of all adsorbates were determined. High selectivity of adsorption for carbon dioxide over methane suggests that the all-silica DD3R is an effective adsorbent or zeolite membrane material that can separate carbon dioxide and methane gaseous mixtures.     

Molecular simulation for adsorption of chlorinated hydrocarbon in zeolites

Equilibrium and isosteric heat of adsorption for the system of chloroform and USY-type zeolite were studied. The USY-type zeolite (PQ Co., SiO₂/Al₂O₃=70) was used both as a pure crystalline powder and as granulated particles with binder. Chloroform was reagent grade. The adsorption equilibria were measured using a gravimetric method and were expressed as isotherms. A chromatographic method (i.e. pulse response of chloroform through the USY column with helium carrier) was used to get the initial slope of the isotherms. In the simulation, the GCMC method was used to calculate amounts adsorbed for various conditions. FF parameters were confidently applied. And modified structure model was effective for simulation. This paper was presented at The 5th International Symposium on Separation Technology-Korea and Japan held at Seoul between August 19 and 21, 1999.     

Chemically modified sunflower stalks as adsorbents for color removal from textile wastewater

Quaternary ammonium groups were chemically grafted onto sunflower stalks in order to improve their adsorption performance to anionic species in wastewater. The chemically modified sunflower stalks were evaluated as adsorbents for two basic dyes (Methylene Blue and Basic Red 9) and two direct dyes (Congo Red and Direct Blue 71) in aqueous solutions by using equilibrium isotherms and kinetic adsorption. Before the modification, sunflower stalks exhibited relatively low adsorption to the direct dyes but very high adsorption to the basic dyes. The modified sunflower stalks showed increased adsorption to the anionic dyes, but slightly reduced adsorption to the cationic dyes, due to the existence of quaternary ammonium ions on the surface of the residues. The maximum adsorption capacities of two direct dyes on the modified sunflower stalks are 191.0 and 216.0 mg g for Congo Red and Direct Blue 71 at 50°C, respectively, which were at least four times higher than that of the unmodified residues. The adsorption rates of two direct dyestuffs are much higher on the modified residues than on the unmodified ones. Within 30 min, about 80% of direct dyes were removed from the solutions by the residues. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1841–1850, 1999     

Equilibrium and Fixed Bed Adsorption of 1‐Butene,Propylene and Propane Over 13X Zeolite Pellets

Abstract

Propylene‐propane separation is one of the most difficult and demanding energetic operation currently practiced using cryogenic distillation. Extensive studies on various alternatives showed that cyclic adsorption processes, and particularly pressure swing adsorption (PSA), might be an option to replace the traditional distillation. In spite of the promising results of the PSA process, much attention is currently being paid to the simulated moving bed technology (SMB) for gas‐phase separations. The ingenious principle of this process is based on the choice of an adequate adsorbent‐desorbent couple. Thus, in the present work 1‐butene has been studied as an interesting desorbent to displace adsorbed propylene‐propane mixture on 13X zeolite. The measurements of pure 1‐butene adsorption isotherms over 13X zeolite were performed with a gravimetric experimental device for pressure ranging from 0 to 110 kPa and at temperature of 333, 353, 373, and 393 K. The experimental adsorption data were correlated using Toth model. The heat of adsorption at zero coverage and the maximum loading capacity of 1‐butene were found to be 54.4 kJ/mol and 2.10 mol/kg, respectively. The adsorption and desorption of 1‐butene on 13X zeolite packed on a fixed bed initially saturated either by a propane‐propylene mixture or a pure C₃ hydrocarbon has been studied. The performance of 1‐butene has been compared with isobutane that was previously proposed to be a highly effective desorbent for C₃H₆/C₃H₈ separation. A model based on a double LDF approximation for the mass transfer combined to a heterogeneous energy balance taking into account a variable velocity of the gaseous bulk phase, has been used to describe the breakthrough curves obtained experimentally at 373 K and 110 kPa.     

Preparation of copolymer brush-type restricted access microspheres with adjustable adsorption selectivity to variety of dyes

Restricted access materials (RAMs) with adjustable selectivity was developed for the removal and detection of residual dyes for the solve problems of dye contamination. In this work, using homemade poly(4-vinylbenzyl chloride-co-divinylbenzene) (P_VBC/DVB) microspheres as substrate and successive two-step surface-initiated atom transfer radical polymerization (SI-ATRP) as synthesis method, the two types of monomers, sodium 4-vinylbenzene sulfonate (Nass) and styrene (St) were first grafted for constructing mixed interactions of adsorption sites, and then the hydrophilic glycidyl methacrylate (GMA) was polymerized, following by hydrolysis to construct diol groups on the external P_VBC/DVB as the restricted access sites. The developed P_VBC/DVB@poly(St-co-Nass)@poly(GMA) of adsorption properties was investigated by six dyes including methylene blue (MB), basic fuchsin (BF), acid fuchsin (AF), neutral red (NR), methyl orange (MO), and Congo red (CR), the adsorption capacities of those dyes and the removal rate for the binary mixed dye solution both rely on the ratio of St/Nass, confirming the adjustable adsorption selectivity. When P_VBC/DVB@poly(St-co-Nass)@poly(GMA) was packed as solid phase extraction adsorbent in couple with UV–vis spectrum, it was applied to the determination of MB and BF in the water, fish and shrimp, good linearity with satisfactory recoveries for MB and BF are obtained to show the favorable practicability.