Terms Of Sorption Capacity Research Articles

Enhanced Water Sorption Performance of Polyacrylamide & Glass Fiber Paper Composites: Investigation and Comparison of Application in Desiccant Wheels.

The water sorption and desorption properties of solid adsorbent materials are crucial in rotary dehumidification systems. Metal organic frameworks (MOFs) and hydrogels are mostly at the laboratory stage due to factors like the synthesis process and yield. In this study, we utilized an eco-friendly and large-scale synthesis method to prepare polyacrylamide (PAM) hydrogels (yielding approximately 500 mL from a single polymerization). Subsequently, PAM was then coated onto glass fiber paper (GFP), which serves as a commonly employed substrate in desiccant wheels. By incorporating the hygroscopic salt LiCl and optimizing the content of each component, the water sorption performance of the composite was notably improved. The water sorption and desorption performances, as well as cycling stability, were evaluated and compared with composites containing aluminum fumarate, LiCl, and GFP (AlFum-LiCl&GFP). The results revealed that PAM-LiCl&GFP outperformed AlFum-LiCl&GFP in terms of sorption capacity throughout various relative humidity (RH) levels. It achieved a water uptake of 1.06 g·g-1 at 25 °C and 30% RH, corresponding to a water sorption rate coefficient K of 15.32 × 10-4 s-1. Furthermore, the lower desorption temperature (60 °C) resulting in a desorption ratio of 82.6%, along with the excellent cycling stability and effective performance as a desiccant wheel module, provide evidence for the potential application of PAM-LiCl&GFP in desiccant wheels.

Alkali metal (Na, Cs and K) promoted hydrotalcites for high temperature CO2 capture from flue gas in cyclic adsorption processes

A hydrotalcite (HT) with a Mg2+/Al3+ molar ratio of 2 was prepared and promoted with different loadings of Na and Cs. After calcination (denoted as CHT), the samples were tested for CO2 sorption at 573 K and 0.15eg bar of CO2 (typical of flue gas). Their performance was compared to that achieved with a commercial HT, MG63, and with a K-doped material for which a significant increase of CO2 sorption capacity has been frequently reported in the literature. However, the presence of K slows down the sorption kinetics, which might compromise the cyclic separation process productivity. In this work, it is aimed to find out a CO2 HT-based sorbent with promising behaviour during continuous sorption/desorption cycles, in terms of sorption capacity, sorption kinetics and cyclic stability. The best compromise was observed for a CHT doped with 9.4 wt% of Cs. A study of the cyclic stability of this material was performed and a kinetic model that can predict the loss of sorption capacity with cycles has been successfully developed. The performance of this sorbent was further investigated in a scenario where other species found in flue gas streams (i.e. O2, H2O and/or CO) are also present.

Evaluation of Electrospun Self-Supporting Paper-Like Fibrous Membranes as Oil Sorbents.

Presently, adsorption/absorption is one of the most efficient and cost-effective methods to clean oil spill up. In this work, self-supporting paper-like fibrous membranes were prepared via electrospinning and carbonisation at different temperatures (500, 650 or 800 °C) by using polyacrylonitrile/polymethylmethacrylate blends with a different mass ratio of the two polymers (1:0, 6:1 or 2:1). After morphological and microstructural characterisation, the as-produced membranes were evaluated as sorbents by immersion in vegetable (sunflower seed or olive) and mineral (motor) oil or in 1:4 (v:v) oil/water mixture. Nitrogen-rich membrane carbonised at the lowest temperature behaves differently from the others, whose sorption capacity by immersion in oil, despite the great number of sorbent and oil properties involved, is mainly controlled by the fraction of micropores. The encapsulation of water nanodroplets by the oil occurring during the immersion in oil/water mixture causes the oil-from-water separation ability to show an opposite behaviour compared to the sorption capacity. Overall, among the investigated membranes, the support produced with 2:1 mass ratio of the polymers and carbonisation at 650 °C exhibits the best performance both in terms of sorption capacity (73.5, 54.8 and 12.5 g g−1 for olive, sunflower seed and motor oil, respectively) and oil-from-water separation ability (74, 69 and 16 for olive, sunflower seed and motor oil, respectively).

Adsorption of volatile organic compounds by ZIF-8, Cu-BTC and a Prussian blue analogue: A comparative study

In this paper, a Prussian blue analogue Co[CoIII(CN)6]0.66·5.2H2O and commercial Cu-BTC and ZIF-8 materials are compared in terms of their sorption capabilities for water or hydrocarbons. Experimental and theoretical approaches were combined in order to better understand the microscopic mechanisms ruling their different sorption properties. It was first demonstrated that amongst the three materials investigated, ZIF-8 was the most hydrophobic, whereas the PBA was more hydrophilic. In terms of sorption capacities, Cu-BTC is highly efficient for adsorption of the investigated hydrocarbons with large adsorption capacities (150 mg.g−1), however, it has proven unstable in the presence of water and cannot be used for humid hydrocarbons adsorption and separation. n-Hexane is preferentially adsorbed (250 mg.g−1 at saturation) in the hydrophobic ZIF-8, whereas cyclohexene is not, due to the size of the windows. Even if ZIF-8 did not adsorb water, its porosity decreased in the presence of water. On the contrary, CoCo is stable in humid conditions and even if its sorption capacity is lower than that found for the other MOFs investigated, it seems more appropriate for humid hydrocarbons sorption or separation.

Effect of ageing on the availability of heavy metals in soils amended with compost and biochar: evaluation of changes in soil and amendment properties.

Remediation strategies using soil amendments should consider the time dependence of metal availability to identify amendments that can sustainably reduce available pollutant concentrations over time. Drying-wetting cycles were applied on amendments, soils and soil+amendment mixtures, to mimic ageing at field level and investigate its effect on extractable Cd, Cu, Ni, Pb and Zn concentrations from three contaminated soils. The amendments investigated were municipal waste organic compost and biochars. The amendments, soils and mixtures were characterised by their physicochemical properties at different ageing times. The amendments were also characterised in terms of sorption capacity for Cd and Cu. The sorption capacity and the physicochemical properties of the amendments remained constant over the period examined. When mixed with the soils, amendments, especially the compost, immediately reduced the extractable metals in the soils with low pH and acid neutralisation capacity, due to the increase in pH and buffering capacity of the mixtures. The amendments had a relatively minor impact on the metal availability concentrations for the soil with substantially high acid neutralisation capacity. The most important changes in extractable metal concentrations were observed at the beginning of the experiments, ageing having a minor effect on metal concentrations when compared with the initial effect of amendments.

Cesium uptake by pentacyanoferrate(II) complexes with O-containing derivatives of chitosan

ABSTRACTHere we report on synthesis of new organic-inorganic materials based on products of interaction between sodium aminoprusside and polymer ligands. Fourier transform infrared (FT-IR) and UV-visible spectroscopy and thermogravimetry were used to investigate the structure and stability of the complexes. It was found that ion and ligand exchange were the main reactions of the interaction of sodium aminoprusside with water-soluble polymer salts. All other composites in the Co(II) form were characterized in terms of sorption capacities and distribution coefficients (Kd) for cesium ions. The highest values of distribution coefficients were obtained for polyampholyte chitosan derivatives.

Visualizations and Optimization of Iron–Sand Mixtures for Permeable Reactive Barriers

AbstractDiluting granular iron with sand is a common practice performed to minimize clogging and to reduce the cost of permeable reactive barrier (PRB) installations. This study used a pore‐scale image analysis technique and a reanalysis of previously published data to test the hypothesis of Bi et al. (2009) that the mixing of 15% by weight sand with a commercial, platy‐grained iron medium opens the pore space between grains, exposes more reactive grain surface to flowing water, and leads to a more reactive medium (i.e., promoting faster transformation rates per unit volume of medium) than 100% by weight granular iron. Four mixing ratios (100, 85, 75 and 50% iron by weight) were compared on the basis of two morphological parameters measured in section: (1) total grain area, which correlates with the total amount of iron present, and (2) grain perimeter, which is governed by both the mobile solution‐available surface and the total amount of iron present. As expected, grain areas exposed in section were highest for 100% iron packings and decreased with increasing sand content. The estimated iron grain effective perimeters (i.e., accessible to mobile water) for 85% iron‐by weight mixtures were similar to 100% iron and decreased in 75 and 50% iron mixtures. The section confirmed that the presence of 15% sand by weight opened up the pore structure, likely improving the mobile‐water to iron contact. The analysis of kinetic column experimental data indicated that the same trend was present in the sorption capacity term in the Kinetic Iron Model (KIM) equation, providing corroborating evidence that the iron surface availability was higher in the 85% iron medium than the 100% iron medium on a per gram of iron basis.

Influencing Factors for Organic Spill Recovery Performance with a Novel Polypropylene-Methacrylate Sorbent.

Insoluble organic matter released to the water body through accidental spillage imposes serious damage on the environment. Polypropylene (PP) fiber and methacrylate resin, however, end up in certain morphology or low sorption capacity after a single use. In this study, a novel sorbent was prepared by radiation-induced graft polymerization of butyl methacrylate (BMA) onto PP fiber matrix to retain the advantages of both PP fibers and methacrylate resins to overcome the shortcomings of each used alone. The different parameters including irradiation power, irradiation time and monomer concentration that effect the grafting degree of grafted fiber were studied. The resulting grafted fibers (PP-g-BMA) were evaluated in this study in terms of sorption capacity, retention behaviors and reusability properties. The investigation revealed that the homopolymerization rate, organic matter temperature and pH values of organic-over-water aqueous solution are the most important factors in the sorption performance of polypropylene grafted fiber sorbent.

Functionalized polymer sheet sorbent for selective preconcentration and determination of mercury in natural waters

Mercury is considered as a highly toxic and widespread heavy-metal pollutant. In the present work, two flat-sheet polymer sorbents have been synthesized for the selective preconcentration of mercury from natural waters. These are a silver nanoparticle (AgNP)-embedded poly(acrylamide)-grafted poly(propylene) sheet (Ag-PAM-PP) and a 1,8-octanedithiol-functionalized gold-coated poly(propylene) sheet (HS-octyl-S-Au-PP). The functional groups acrylamide and thiol provide the binding sites for Hg2+ ions; whereas silver nanoparticles reduce Hg2+ to Hg0 and it is held on the sheet by amalgam formation. Various factors that influence the preconcentration of Hg2+ from aqueous solution were investigated. Based on the comparison of the experimental results, it was observed that Ag-PAM-PP had superior performance for uptake of Hg2+ from natural water samples in terms of sorption capacity, sorption kinetics and working pH range. The uptake of Hg2+was found to be pH dependent with a maximum of 95% at pH 7.5. The preconcentration of Hg2+ from a large volume of aqueous solution was used to extend the lower limit of the concentration range that can be quantified by EDXRF and CV-AAS. The sorbed Hg(II) from aqueous samples was quantitatively detected within 1 min using EDXRF. The LOD (3σ) for CV-AAS (RSD = 2%) and EDXRF (RSD = 5%) were 6 and 30 μg L−1, respectively. The method was applied for the determination of Hg2+ in groundwater and seawater samples in the presence of a high concentration of interfering ions.

Adsorption of C5–C9 hydrocarbons in microporous MOFs MIL-100(Cr) and MIL-101(Cr): A manometric study

The adsorption of n-alkanes ( n-pentane to n-nonane) on the mesoporous MIL-100(Cr) and the MIL-101(Cr) rigid solids has been performed with a view of evaluating the influence of the alkyl chain length in terms of sorption capacity and sorbate/sorbent affinity. MIL-100(Cr) exhibits at first sight a classical type I behaviour towards the sorption of n-alkanes. These sorption isotherms have proven to be fully reversible. A direct relationship between amounts of alkane adsorbed at saturation and number of carbon atoms present in the adsorbed species has been found. At very low pressure ( p/ p 0 < 0.025), sub-steps are present in the isotherm curve, due to the presence of two sets of cages (≈24 Å and 29 Å) and windows (≈5 Å and 9 Å). In the case of MIL-101(Cr), the sub-steps are shifted to higher partial pressures ( p/ p 0 < 0.10) due to the larger size of the cages (≈27 Å and 34 Å) and windows (≈12 Å and 16 Å). For the same apolar sorbates, this outlines the effect of pore dimensions of the two MOFs, which are larger in the case of the MIL-101(Cr) structure, and gives rise to important differences in terms of affinity or sorption mechanisms. This is confirmed by the determination of the enthalpy of adsorption of n-hexane or n-heptane much lower in the case of MIL-100 as compared to MIL-101, at low coverage, −65 kJ mol −1 and −30 kJ mol −1, respectively. The kinetics of the sorption process has also been discussed by comparing the equilibration times of the different sorbates during their adsorption. n-Nonane exhibited much longer equilibration times as to compared to shorter n-alkanes.

Chemically modified olive stone: A low-cost sorbent for heavy metals and basic dyes removal from aqueous solutions

In the present work, we have investigated the sorption efficiency of treated olive stones (TOS) towards cadmium and safranine removal from their respective aqueous solutions. TOS material was prepared by treatment of olive stones with concentrated sulfuric acid at room temperature followed up by a subsequent neutralization with 0.1 M NaOH aqueous solution. The resulting material has been thoroughly characterized by SEM, energy-dispersive X-ray (EDX), MAS 13C NMR, FTIR and physicochemical parameters were calculated. The sorption study of TOS at the solid–liquid interface was investigated using kinetics, sorption isotherms, pH effect and thermodynamic parameters. The preliminary results indicate that TOS exhibit a better efficiency in terms of sorption capacities toward the two pollutants (128.2 and 526.3 mg/g for cadmium and safranine, respectively) than those reported so far in the literature. Moreover, the sorption process is ascertained to occur fast enough so that the equilibrium is reached in less than 15 min of contact time. The results found in the course of this study suggest that ion exchange mechanism is the most appropriate mechanism involved in cadmium and safranine removal. Finally, the sorption efficiency of TOS is compared to those of other low-cost sorbents materials yet described in the literature.

Removal of Hydrophobic Micro-Organic Pollutants from Municipal Wastewater Treatment Plant Effluents by Sorption onto Synthetic Polymeric Adsorbents: Batch Sorption Experiments

The use of a synthetic form polymer, polypropylene, as a sorbent for hydrophobic organic compounds present in municipal wastewater treatment plant effluent was investigated. To enhance the sorption capacity of polypropylene for hydrophobic organic compounds, polypropylene was coated with a thin layer of n-hexane. Sorption of target compounds onto polypropylene and polypropylene coated with n-hexane was evaluated by carrying out equilibrium and kinetic batch experiments. Three polycyclic aromatic hydrocarbons, namely, phenanthrene, fluorene and naphthalene, were selected as representative hydrophobic organic compounds for experimental purposes. The effect of pH, ionic strength and dissolved organic matter on sorption was investigated. The results showed that polypropylene coated with n-hexane performed better than polypropylene as a sorbent for polycyclic aromatic hydrocarbons, in terms of sorption capacity and sorption kinetics. Ionic strength and pH did not have a significant effect on the sorption of polycyclic aromatic hydrocarbons. Dissolved organic matter in the form of humic acid did not sorb onto polypropylene or polypropylene coated with n-hexane, and the presence of dissolved organic matter in the aqueous phase did not significantly affect sorption of polycyclic aromatic hydrocarbons.

Biosorption of Pb(II) and Cu(II) from aqueous solutions by pretreated biomass of Neurospora crassa

The sorption of Pb(II) and Cu(II) ions from aqueous solutions by raw and pretreated Neurospora crassa fungal biomass was investigated in the batch mode. The influence of solution pH, equilibrium time and initial metal ion concentration using dried N. crassa cells as well as pretreatment on the sorption capacity of the biomass at optimum conditions were studied. The optimum conditions were pH 4.0 for Pb(II) and 5.0 for Cu(II) ions at initial metal ion concentration of 200 mg l −1 with equilibrium time of 15 min for both metal ions. Dried fungal cells exhibited the maximum sorption capacity (49.06 mg g −1) for Pb(II) ions while detergent treated cells showed the maximum sorption capacity (12.28 mg g −1) for Cu(II) ions. The experimental equilibrium data were evaluated by Freundlich and Langmuir isotherm models. Competitive biosorption of these metals was investigated in terms of sorption capacity and found that the biosorption capacity of biomass decreased with increasing the competing metal ion concentration. The involvement of functional groups on the surface of dried biomass in biosorption process is also discussed.

Improved design and optimization models for the fixed bed adsorption of acid dye and zinc ions from effluents

AbstractThe bed depth service time (BDST) design model, which accounts for the change of bed adsorption capacity with service time, has been modified to expand its application and overcome the limiting assumptions of the original BDST analysis. Column experiments were undertaken to test the new model for two adsorption systems, namely zinc ion–bone char and Acid Blue 80 dye‐activated carbon. It was found that the percentage of saturation capacity could be correlated using a square‐root dependence on the service time and this correlation was incorporated into the original BDST analysis to replace the total sorption capacity term, giving the model a much wider application to real systems. The empty bed residence time optimization approach was modified using the same time‐dependent capacity expression and was successfully applied to the metal ion–bone char and the dye‐activated carbon system with the use of equilibrium saturated bed capacity. These modifications to the BDST design model and the EBRT optimization model will give more accurate scale‐up data for the design of large‐scale column adsorption systems.© 2002 Society of Chemical Industry

The influence of ionic strength on the facilitated transport of cesium by kaolinite colloids

We report results of laboratory experiments on the co‐transport of137Cs by inorganic colloids composed of kaolinite. We find that under conditions of low pore water ionic strength, the kaolinite colloids significantly accelerate137Cs transport through columns packed with quartz sand, kaolinite mobility and the affinity of kaolinite for binding137Cs diminish with increasing ionic strength. As a result, kaolinite exerts a progressively smaller influence on137Cs transport as the ionic strength increases from 0.002 to 0.1 m. The137Cs breakthrough data are used to test a model that incorporates advection‐dispersion equations for the movement of kaolinite colloids, dissolved137Cs, and kaolinite‐associated137Cs and mass transfer equations for kaolinite deposition,137Cs adsorption by kaolinite, and137Cs adsorption by quartz sand; The partition coefficient for137Cs retention by kaolinite colloids and the first‐order rate coefficient for kaolinite deposition vary in a discernible fashion with changes in ionic strength. The adsorption rate coefficient and the sorption capacity term of the second‐order rate law taken to describe137Cs adsorption to the quartz sand are independent of ionic strength; however, the magnitude of the desorption coefficient varies logarithmically with ionic strength. This work indicates the need to account for enhanced movement of sorbing solutes by inorganic colloids and provides a basis for quantifying the response of colloid‐associated solute transport to changes in pore Water chemistry.

Solubility and permeability of quenched poly (2,6-dimethyl phenyleneoxide) with various microvoids

Solubility and permeability of poly(2,6-dimethyl phenyleneoxide) (PPO) membranes glassifled under various quenching conditions were examined with respect to the occurrence of microvoids in order to clarify the mechanism and enhancement of permeation of glassy polymer membranes. Various PPO membranes were prepared by quenching from various holding temperatures above its glass transition temperature to a temperature in the glassy state, e.g. 0°C. The CO 2 sorption in quenched PPO membranes increased with the increase of the holding temperature and was greater than that in slowly cooled PPO membranes. Sorption behavior of quenched PPO membranes was analysed by dual mode sorption model. The increase in sorption was interpreted in terms of increasing microvoid content; in other words Langmuir sorption capacity term caused by the quenching. The permeability of quenched PPO membranes was also enhanced by the increase in size of the microvoids. The permeability increased with an increase of the holding temperature and was greater than that of slowly cooled PPO membranes. The permeation mechanism is explained by a partial immobilization model.

Gas transport properties in polycarbonate films with various unrelaxed volumes

The unrelaxed volume in polycarbonate (PC) was varied by thermal or pressure conditioning, and the sorption and permeation of CO 2 in PC films with various unrelaxed volumes were investigated. The dual-mode sorption and the partial immobilization models were used to analyse sorption and permeation behaviour. The amount of CO 2 sorption in PC films quenched from various temperatures above the glass transition temperature ( T g) was increased with increasing holding temperature above T g, and was larger than that in PC film cooled slowly from a temperature above T g. The increase in the amount of CO 2 sorption caused by the quenching was explained by the increase of the Langmuir sorption capacity term ( C′ H). In contrast, other dual-mode sorption parameters were found to be unchanged by conditioning. The values of C′ H of various quenched PC films, which were obtained from CO 2 sorption isotherms, agreed with those evaluated from the specific volume-temperature curve. The amount of CO 2 sorption in PC film conditioned under 60 atm CO 2 was larger than that in quenched PC film. The two diffusion coefficients, D D and D H, of the partial immobilization model, for CO 2 of quenched PC film were also larger than those of slowly cooled PC film. The difference in D H was found to be larger than that in D D. The two diffusion coefficients of PC film conditioned under 60 atm CO 2 were also greater than those of quenched PC films.

Gas Transport Properties of Various Imidized Polyamic Acid Films

The sorption and permeation of CO2 in and through various imidized polyamic acid [PAA] films were investigated. Dual-mode sorption and partial immobilization models were applied to their phenomena and their behavior and structure are discussed. The amount of CO2 sorption increased with imidization in PAA film up to the imide content of ca. 40%, and then decreased. This behavior can be attributed mainly to the variation of the Langmuir sorption capacity term (CH′). In other words, it can be regarded that an unrelaxed volume and/or a microvoid fraction [(Vg−Vl)/Vg] vary with imidization, which are functions of Tg and difference in the expansion coefficient between liquid and glassy states. CH′ was described by the product (Tg−25) and ΔCp, difference of heat capacity between liquid and glassy states used instead of the expansion coefficient. On the other hand, the diffusion coefficient of Henry’s law mode (DD) is enhanced by the decrease of carboxyl group in PAA reducing the diffusion of penetrant with imidization up to ca. 40%, and then is depressed by restricted thermal mobility caused by considerably increased rigidity in the polymer chain with imidization. Variation in the diffusion coefficient of Langmuir mode behaved parallelly to DD.

O2 and N2 gas permselectivity of alternating copoly(vinylidene cyanide–vinyl acetate)

AbstractThe sorption and permeation of oxygen and nitrogen in and through alternating copoly(vinylidene cyanide–vinyl acetate) [copoly(VDCN–VAc)] (Tg = 176°C) membranes annealed for different periods just below Tg, 160°C, were investigated over the pressure range from 100 to 1000 cmHg. The dual‐mode sorption and mobility models were used to analyze the results. A sub‐Tg annealing of copoly(VDCN–VAc) caused a slight decrease in the amount of sorption in the membranes. This decrease in the amount of oxygen and nitrogen sorption can be attributed to a decrease in the Langmuir sorption capacity term, C′H, with increasing sub‐Tg annealing period. The densification of copoly(VDCN–VAc) membranes caused simultaneously by the annealing remarkably reduced diffusion coefficients for both gases. The reduction in diffusion coefficients of Langmuir mode, DH, for both gases was found to be larger than that of Henry's law mode, DD. Furthermore, permselectivity of oxygen to nitrogen, the ratio of permeability coefficient of oxygen to nitrogen (PO2/PN2), reached to 11.8 for the copoly(VDCN–VAc) annealed for 30 h. Evidently the reduction of DH and DD for nitrogen with increasing annealing period was much larger than that for oxygen.