Fiber Adsorbent Research Articles

OPTIMUM PRESSURE DISTRIBUTION IN DESIGN OF CRYOGENIC NGL RECOVERY PROCESSES

A type of novel hypercross-linked fiber adsorbent was obtained by sulfonation and cross-linking reaction of polypropylene fiber grafted styrene-divinylbenzene. The aim of the fiber sulfonation and cross-linking method was to prepare rigid three dimensional networks in the entire fiber and change the ion exchange capacity of fiber. The hypercross-linked fiber adsorbent possesses a principally different structure and could offer new possibility for adsorption, which is characterized by high adsorption capacity for aniline in this paper. A series of static adsorption tests were made. The results showed that the adsorbent has excellent adsorption capacity for aniline and the adsorption equilibrium data can be well fitted by Freundlich model. Adsorption of aniline on adsorbent was chemical adsorption and high temperature was favourable to endothermic chemisorption process. In addition, the kinetic studies were also carried out. The hypercross-linked fiber adsorbent showed faster adsorption rate than the base fiber. The quicker attainment of adsorption equilibrium (within 20 minutes) for aniline on adsorbent is advantageous for practical use. The pseudo-second-order rate model was suitable to describe the process. The pseudo-second-order model gave an excellent fit to all experimental data and adsorption capacities calculated by pseudo-second-order rate model were close to the values actually measured.

De-coloration of hazardous dye from water system using chemically modified Ficus carica adsorbent

Batch adsorption studies were carried out using a novel chemically modified Ficus carica fiber adsorbent for the removal of toxic methylene blue dye from aqueous solution. The modification of F. carica fiber was carried out using acrylic acid in the presence of ceric ammonium nitrate as the initiator to change the surface morphology of the natural fibers for the improvement of interfacial adhesion between matrix and fibers. The adsorbent was characterized by scanning electron microscopy and Fourier transformer infrared spectrometer. The effect of process parameters such as pH, adsorbent dosage, concentration, reaction temperature, contact time, electrolyte and surfactants were studied. The adsorption equilibrium was represented with Langmuir, Freundlich, Tempkin, and Harkin's–Jura and Dubinin–Radushkevich isotherm models. The maximum adsorption capacity of methylene blue onto adsorbent was 75.87mgg−1. The pseudo-first order, pseudo-second order and intraparticle diffusion models were tested and it is revealed that adsorption of methylene blue onto adsorbent follows the intraparticle diffusion model. Thermodynamic parameters such as enthalpy change (∆H), entropy change (∆S) and free energy change (∆G) were evaluated to predict the nature of adsorption. The calculated values of ∆H, ∆S and ΔG for uptake of MB were 33.13kJmol−1, 173.46Jmol−1K−1 and −19.43kJmol−1, respectively. This indicated the endothermic and spontaneous nature of the adsorption process. The desorption experiment showed that 60.04% of dye was recovered from the aqueous system.

Adsorption Mechanism for Aniline on the Hypercross-Linked Fiber

A type of novel hypercross-linked fiber adsorbent was obtained by sulfonation and cross-linking reaction of polypropylene fiber grafted styrene-divinylbenzene. The aim of the fiber sulfonation and cross-linking method was to prepare rigid three dimensional networks in the entire fiber and change the ion exchange capacity of fiber. The hypercross-linked fiber adsorbent possesses a principally different structure and could offer new possibility for adsorption, which is characterized by high adsorption capacity for aniline in this paper. A series of static adsorption tests were made. The results showed that the adsorbent has excellent adsorption capacity for aniline and the adsorption equilibrium data can be well fitted by Freundlich model. Adsorption of aniline on adsorbent was chemical adsorption and high temperature was favourable to endothermic chemisorption process. In addition, the kinetic studies were also carried out. The hypercross-linked fiber adsorbent showed faster adsorption rate than the base fiber. The quicker attainment of adsorption equilibrium (within 20 minutes) for aniline on adsorbent is advantageous for practical use. The pseudo-second-order rate model was suitable to describe the process. The pseudo-second- order model gave an excellent fit to all experimental data and adsorption capacities calculated by pseudo-second-order rate model were close to the values actually measured.

Hollow fiber adsorbents for CO 2 capture: Kinetic sorption performance

We describe a CO 2 capture platform based on hollow polymeric fibers with sorbent particles embedded in the porous fiber wall for post-combustion CO 2 capture. These fibers are intended for use in a rapid temperature swing adsorption (RTSA) process. The RTSA system utilizes the hollow fiber morphology by flowing cooling water on the bore-side of the fibers during sorption to prevent temperature rise associated with the sorption enthalpy. Steam or hot water is flowed through the bores during desorption to desorb CO 2 rapidly. To minimize material transfer between the bore and the fiber wall, a dense Neoprene ® lumen layer is cast on the bore-side of the fiber wall. In this paper, the key sorption step and associated kinetic resistances for the uncooled fibers are examined and evaluated for this portion of the RTSA process. Chopped fibers in a packed bed, as well as fibers assembled into a parallel flow module, have been tested in a simulated flue gas stream. Kinetic limitations in the hollow fiber modules are largely overcome by increasing the superficial gas velocity and the fiber packing in the module—indicating that film diffusion is the controlling mass transfer limitation in the fiber system. The un-cooled fiber modules lose apparent capacity as superficial velocities are increased, likely indicating non-isothermal operation, whereas the actively-cooled fibers in the packed bed maintain apparent capacity at all flowrates studied.

Separation of flavonoid and alkaloid using collagen fiber adsorbent

Flavonoids and alkaloids are two major classes of plant compounds with biological activities, and they usually coexist in many medicinal herbs. In this study, a novel collagen fiber adsorbent (CFA) was prepared, and its application for adsorption chromatography separation of flavonoids and alkaloids was systematically investigated. The typical flavonoids, rutin and baicalin, and the typical alkaloids, matrine and caffeine, were selected as probe molecules for the investigations. The batch adsorption behaviors of these compounds on CFA in different solvents indicated that hydrogen bond plays a predominant role for the adsorption of flavonoid and alkaloid in pure ethanol, while the hydrophobic interaction plays a predominant role for the adsorption in water. In column chromatography separation, flavonoids were completely separated from alkaloids by a stepwise elution process with pure ethanol followed by aqueous ethanol solution. The two flavonoids, rutin and baicalin, were also well separated although the two alkaloids, matrine and caffeine, were washed out together. The optimal loading volume of sample solution (10 mg/mL) for the separation was determined as 0.66 mL/g CFA. Under these conditions, flavonoid and alkaloid were effectively separated with a recovery higher than 90% in 8 times repeated applications.

Preparation and characterization of PAN-based ultra-fine activated carbon fiber adsorbent

Polyacrylonitrile-based (PAN) ultra-fine fibers were made from electrospining with dimethylformamide as a solvent. And then the fibers were processed via pre-oxidization, carbonization, and steam activation to produce the PAN-based ultra-fine activated carbon fiber (UFACF) adsorbent. According to the specific surface area, pore volume, pore size distribution and phenol adsorption value, the effects of different factors on the yield of activation and adsorption properties of UFACF were investigated through the orthogonal experiment. TG, field emission-scanning electron microscope, FTIR, XRD were employed to characterize the morphology and structure evolvement of UFACF during thermal treatment process. At the optimal conditions, the yield of activation of UFACF was from 37.2 to 58.5%, the maximal specific surface area 1075.1 m2 g−1, and the maximal phenol adsorption value 377.1 mg g−1.

Selective removal of tannins from Polygonum cuspidatum extracts using collagen fiber adsorbent

To investigate the selective removal of tannins from Polygonum cuspidatum extracts by using collagen fiber adsorbent, and to evaluate the adsorption and desorption performances of collagen fiber adsorbent to tannins. The adsorbent was prepared from bovine skin collagen fiber through crosslinking reaction of glutaraldehyde, and then used for the selective removal of tannins from P. cuspidatum extracts. Gelatin-turbidity method, gelatin-ultraviolet spectrometry method and HPLC were used for detection of tannins in the solutions. Ethanol-water solutions with varying concentration were used to test their desorption ability of tannins in order to choose proper desorption solution. On the basis of batch experimental results, the column adsorption and desorption tests were carried out, by using gelatin-turbidity method for detection of tannins. The collagen fiber adsorbent exhibited excellent adsorption selectivity to tannins. It was found that tannins of P. cuspidatum were completely removed, while nearly no adsorption of active components (resveratrol as representative) was found. Moreover, the collagen fiber adsorbent could be regenerated by using 30% ethanol-water solution and then reused. The collagen fiber adsorbent can be considered as a promising material for selective removal of tannins from P. cuspidatum extracts.

Adsorptive removal of 2,4-DCP from water by fresh or regenerated chitosan/ACF/TiO 2 membrane

In order to remove micro-pollutant 2,4-DCP (dichlorophenol, 1–50 mg/L) from aqueous solution using low pressure membrane separation process, and to study photocatalytic/oxidative cleaning of membrane fouled by adsorption, a new organic/inorganic hybrid composite membrane with adsorption, filtration and photocatalysis property was studied which contains coated chitosan (CS), activated carbon fiber (ACF) adsorbent and titanium dioxide on terylene fabrics. The scanning electron microscopy (SEM) of the membrane showed TiO 2 as the top layer, while CS and ACF were under TiO 2. FTIR spectrum analysis reflected the feature of CS, ACF and TiO 2, and water flux measurements indicated that the composite membrane with coating layer still possessed high filtration property. The adsorptive removal of 2,4-DCP using both static and dynamic modes (25–100 L m −2 h −1) was highly efficient. The CS/ACF/TiO 2 membrane adsorption capacity can be regenerated by oxidizing adsorbed 2,4-DCP via in situ or off-site photocatalysis and/or Fenton oxidation, and both off-site oxidation methods are more efficient than in situ oxidation.

Separation of Proanthocyanidins into Oligomeric and Polymeric Components Using a Novel Collagen Fiber Adsorbent

A novel collagen fiber adsorbent (CFA) was prepared by modification of natural collagen fiber using glutaraldehyde, and its adsorption behaviors to proanthocyanidins were investigated. Both batch and column adsorption experiments indicated that CFA has high adsorption selectivity to polymeric proanthocyanidins because of the stronger trend of these polymers to combine with collagen fiber through hydrophobic and hydrogen bonds. Based on this character of CFA, the purified oligomeric proanthocyanidins was obtained by using CFA as adsorbent. Meanwhile, it was found that the polymeric proanthocyanidins adsorbed on CFA can be easily desorbed by 50% (v/v) acetone-water solution. Thus, as a cost effective approach, CFA can be used to separate proanthocyanidins extracts into two parts, oligomeric proanthocyanidins and polymeric proanthocyanidins, which would favor the fine uses of proanthocyanidins extracts. Column adsorption studies showed that CFA used can be regenerated by using acetone-water solution as eluant, and its adsorption selectivity to polymeric proanthocyanidins was almost unchanged in 6 cycles.

Hollow Fiber Adsorbents for CO2 Removal from Flue Gas

The nation’s pulverized coal infrastructure is aging, and implementation of current retrofit postcombustion capture methods is extremely expensive. This paper describes a technology based on hollow polymeric fibers with sorbent particles embedded in the porous fiber wall to enable postcombustion CO2 capture via a rapid temperature swing adsorption (RTSA) system. The system takes advantage of the hollow fiber morphology by passing cooling water through the bores during sorption to maximize sorption capacities and steam through the bores during desorption to desorb CO2 efficiently. The thin-walled hollow fibers offer the advantage of rapid heat and mass transport. To avoid mass transfer between the core and the fiber sheath, a dense lumen layer is used on the interior of the fiber wall. This system has advantages over competing technologies. Specifically, the fiber sorbent contactor minimizes flue gas pressure drop across the bed, while maximizing sorption efficiencies via rapid thermal cycles and low regenerative thermal requirements.

Nickel (Ii) Ion Desorption Kinetic Modeling From Unmodified and Chemically Modified Oil Palm (Elaeis Guineensis) Fruit Fibre Adsorbents

The desorption of Ni2+ from three oil palm fruit fibre adsorbents (UOPF, 0.5MOPF and 1.0MOPF) using five desorbing solutions showed a desorption efficiency following the trend, 0.1M HCl > 0.1MH2SO4 > 0.1MHNO3 > 0.1MNaOH >hot deionized H2O. The Elovich desorption constant, β values for the 0.1MHCl desorbent were: 6.45 X10-1, 5.57 x 10-1 and 4.34 x 10-1g. mg-.min-1 for UOPF,0.5MOPF and 1.0MOPF adsorbents respectively. The surface residence time values for the 0.1MHCl desorbent were; 32.3, 28.6 and 26.8 seconds for UOPF, 0.5MOPF and 1.0MOPF adsorbents respectively. Kinetic modeling analysis of the Elovich and pseudo-first order desorption equations, indicates that the latter model described the desorption of Ni2+ better.Keywords: Nickel, desorption, modeling, kinetics, Elovich, oil palm.

Recovery of Th(IV) from aqueous solution by reassembled collagen-tannin fiber adsorbent

A novel adsorbent, collagen immobilized tannin adsorbent (CITA), was prepared and its adsorption behaviors to Th(IV) were investigated. CITA was in fibrous state due to the reassembly of collagen molecules by the inducement of tannin. This adsorbent loaded a greater amount of tannin and exhibited higher adsorption capacity to Th(IV) than the tannin immobilized adsorbent prepared from collagen fiber. The adsorption of CITA to Th(IV) is mainly attributed to surface complexation, which is a pH- rather than an ionic strength-dependent process. The adsorption kinetics and isotherms were described by pseudo-second-order rate model and Freundlich equation, respectively. Column adsorption studies indicated that CITA is available for effectively recovering Th(IV) from aqueous solution.

Principles and basic trends in the use of carbon fibre adsorbents

The fundamental trends in development of activated carbons are formulated: selection of carbon raw materials, methods of activation and regulating the pore structure, and a study of the properties and areas of application. The basic properties of carbon fibre adsorbents (CFA) that determine the expediency and areas of their application are reported. The trends and areas of application of CFA are determined.

Adsorption Mechanism for 2‐Methylpyridine on Hypercross‐linked Fibers

AbstractTwo types of novel hypercross‐linked fiber adsorbents, ZH‐01 and ZH‐02, were prepared by cross‐linking PP‐ST‐DVB fibers in solution with p‐xylylenedichloride and monochloromethylether according to the Friedel‐Crafts reaction. A series of static adsorption tests were performed. The results showed that the adsorbents have excellent adsorption capacities for 2‐methylpyridine and the adsorption equilibrium data can be fitted well by the Freundlich model. The thermodynamic studies supported the conclusion that the mechanism of adsorption for 2‐methylpyridine on the adsorbents is physical adsorption and a lower temperature is favorable to the exothermic physisorption process. In addition, kinetic studies were also carried out. The hypercross‐linked fiber adsorbents showed a faster adsorption rate than the base PP‐ST‐DVB fiber. The faster attainment of adsorption equilibrium for 2‐methylpyridine on the adsorbents (within 2 h), is advantageous for practical use. A first‐order reaction rate equation was assumed for the adsorption system and was suitable to describe the process. The equilibrium rate constants of the adsorbents correlated well with their adsorption capacities.

Kinetics of Cd 2+ and Cr 3+ Sorption from Aqueous Solutions Using Mercaptoacetic Acid Modified and Unmodified Oil Palm Fruit Fibre( Elaeis guineensis) Adsorbents

The kinetics of the sorption of Cd 2+ and Cr 3+ from aqueous solutions by mercaptoacetic acid modified and unmodified oil palm fruit fibre adsorbents were investigated. The results indicate that sorption equilibrium was reached within 60 min for both metals. Also, the removal efficiency of the three adsorbents was observed to increase for both metals with stronger treatments with mercaptoacetic acid. This may be attributed to the influence of the thiolation of the adsorbents. Furthermore, Cr 3+ had higher removal percentages than Cd 2+ for all the adsorbents. The sorption mechanism based on the intraparticle diffusion model shows that Cd 2+ sorption is better described than Cr 3+. The intraparticle diffusion rate constants, K id, for Cd 2+ are 62.04 min −1 (untreated), 67.01 min −1 (treated with 0.5 mol/L mercaptoacetic acid), and 71.43 min −1 (treated with 1.0 mol/L mercaptocacetic acid) while those for Cr 3+ are 63.41 min −1 (untreated), 65.79 min −1 (0.5 mol/L acid treated), and 66.25 min −1 (1.0 mol/L acid treated).

On-line preconcentration cold vapour atomic absorption spectrometry for the determination of trace mercury in edible seaweeds

Possibilities for the use of an inexpensive sulfydryl cotton fiber (SCF) adsorbent to separate and preconcentrate traces of mercury from acid digests from edible seaweed have been evaluated. Commercial empty cartridges were filled with around 0.75 g of laboratory-made adsorbent and they were incorporated in the 5-way valve of an automatic flow injection analysis system. Traces of mercury in acid digests were pumped through the cartridges for 45 s (flow rate of 8.8 ml min−1) and then eluted from cartridges with 0.5 M hydrochloric acid and 1.0 M sodium chloride solution for 45 s at a flow rate of 5.8 ml min−1. At the same time that mercury is eluted from the cartridges, the eluate is mixed with a 0.05% (m/v) sodium tetrahydroborate solution and the mercury cold vapour is swept through the atomization cell with an argon flow of 50 ml min−1. The overall procedure (mercury separation/preconcentration and mercury cold vapour generation/atomization) is completed after around 90 s. The developed method implies an enrichment factor of 10.2 with a limit of detection of 5.23 ng g−1. Repeatability of the overall procedure and accuracy were successfully assessed.

Determination of methylmercury fluxes across the air–water and air–soil interfaces by gas chromatography with electron capture detection

A method for the determination of methylmercury (MeHg) fluxes across the air-water and air-soil interfaces was developed using an in situ chamber. The MeHg in the air coming out of the chamber was captured by a column containing sulfhydryl cotton fiber adsorbent. MeHg was then desorbed from the column by using 2 mol L(-1) HCl. The MeHg in the effluent was extracted with benzene, and determined by gas chromatography with electron capture detection. Finally, the MeHg flux was calculated using the chamber. The method was applied to simulated experiments, and the results showed that the MeHg fluxes in the air-water system were higher than those in the air-soil-water system. The method was also successfully applied to the field measurements of an environment polluted by a chemical factory, and the results showed that the MeHg fluxes across the air-soil and air-water interfaces were 0.21-3.09 and 0.14-0.79 ng m(-2) h(-1), respectively. The method will be a useful tool in the environmental study of MeHg.

Selective removal of tannins from medicinal plant extracts using a collagen fiber adsorbent

AbstractA novel adsorbent, used for the selective removal of tannins from medicinal plant extracts, was prepared from bovine skin collagen fiber. Some typical active constituents of medicinal plants were selected as probe molecules to investigate the adsorption selectivity of the collagen fiber adsorbent to tannins. In batch adsorption experiments, the extent of adsorption of condensed tannins, including larch tannin, black wattle tannin and bayberry tannin, was 100%. The extent of adsorption of tannic acid and the hydrolyzable tannins was also 100%. In contrast, for the most active constituents of medicinal plants, their amounts adsorbed by collagen fiber adsorbent were limited. For procyanidin, the common active constituents in medicinal plant extracts, its extent of adsorption was also low, although it has a similar basic structure to condensed tannins. In comparison with traditionally used polyamide adsorbent, the collagen fiber adsorbent exhibited an obvious advantage in adsorption selectivity over tannins. Therefore, this study provides a novel and effective method for selective removal of tannins from medicinal plant extracts. Copyright © 2005 Society of Chemical Industry

Methylmercury artifact formation during solid-phase extraction of water samples using sulfhydryl cotton fiber adsorbent

Preconcentration of methylmercury from dilute water samples by solid-phase extraction on a column packed with sulfhydryl cotton causes methylation of inorganic mercury. The effect is most severe for low concentrations of mercury in deionized water and environmental water samples, such as melted snow or rainwater, with low dissolved organic carbon (DOC) contents, resulting in up to 40% conversion of inorganic mercury to methylmercury. Although, in previous studies artifact methylmercury was attributed to the presence of naturally occurring DOC in the water, we find evidence for methylation especially in the absence of DOC. Indeed, high DOC content appears to suppress artifact formation. In such cases, binding of inorganic mercury by organic matter protects the mercury from methylation under the analysis conditions.

Preparation of a new type of fiber adsorbent attached with silica microparticles.

A new type of fiber adsorbent attached with silica microparticles was prepared. The silica microparticles were formed by the polymerization of silica oligomers on glass fibers, which were woven into a glass filter. The surface of the silica microparticles was chemically modified by bonding C18-ligands. SEM images indicated that the diameter of the uniform and spherical silica microparticles fixed on glass fibers was on the order of micrometers. It was confirmed that the glass filter adsorbent was effective for the adsorptive removal of toluene of low concentrations.