The effects of spacer arms in cross-linked hyaluronan hydrogel on Fbg and HSA adsorption and conformation

Four hyaluronan based hydrogels with different cross-linking agents were synthesised. Compounds with an increasing hydrophobic character and length as spacer arms were chosen, i.e. O,O′-bis(2 aminopropyl)polyethylen glicol, 1.3 diaminopropane, 1.6 diaminohexane, and 1.12 diaminedodecane. The cross-linking reaction involved 50% of the carboxylate groups present in the hyaluronan macromolecule chain. Hydrogels were characterised by water-uptake measurements and SEM analysis. The adsorption of two plasma proteins (HSA and Fbg) was analysed onto the four hydrogels in flow conditions by ATR-FTIR, evaluating the adsorption kinetics and the eventual protein conformational changes. The increasing hydrophobic character of the surface imposes a clear trend to the protein adsorption kinetics. The influence of the spacer arms on the protein conformation is evident on HSA, whereas Fbg does not seem to be significantly influenced by the change of the substrate hydrophobic properties.     

Adsorption and recognition of protein molecular imprinted calcium alginate/polyacrylamide hydrogel film with good regeneration performance and high toughness

Protein imprinted calcium alginate/polyacrylamide hydrogel film (CA/PAM MIP) with high toughness was prepared using bovine serum albumin (BSA) as template molecule, sodium alginate and acrylamide as functional monomers, N,N′-methylenebisacrylamide (MBAA) as the covalent cross-linker and CaCl₂ as the ionic cross-linker via UV radiation-reduced polymerization. Factors affecting the adsorption capacity and imprinting efficiency of the BSA-imprinted CA/PAM hydrogel films were investigated, such as ratio of polyacrylamide/sodium alginate, film thickness, MBAA concentration and CaCl₂ concentration. Results showed that the CA/PAM MIP exhibited an obvious improvement in terms of adsorption capacity for BSA compared with non-imprinted polymer (NIP). The adsorption capacity of MIP for BSA reached 22.49 mg/g, which was 2.7 times higher than NIP. The regeneration property of the BSA-imprinted CA/PAM hydrogel was distinctly improved and the imprinting efficiency of CA/PAM MIP maintained 77.95% of the initial value after five repetitions. Single and binary proteins rebinding indicated that the CA/PAM MIP exhibited good recognition performance. Cell culture experiments showed CA/PAM MIP was more suitable for cell culture than CA/PAM NIP. The residual sodium dodecyl sulfate (SDS) in the elution process leaded to the death of mouse fibroblast cells (L929) after 3 days. A moderate elution solution without residue eluent should be used to prepare MIP for cell culture.     

Preparation of starch/poly(N,N-Diethylaminoethyl methacrylate) hydrogel and its use in dye removal from aqueous solutions

Starch/poly(N,N-Diethylaminoethyl methacrylate) graft copolymer was synthesized by graft polymerizing N,N-Diethylaminoethyl methacrylate monomers onto cooked starch using ceric ammonium nitrate/nitric acid mixture as an initiator. After extracting the graft copolymer from the homopolymer and evaluating the graft yield, the graft copolymer was subjected to crosslinking treatment using epichlorohydrin in alkaline medium to convert it to hydrogel. The so prepared hydrogel was evaluated for its swelling ratio which was found to be 100. The hydrogel with its cationic functionality was tried for removing the anionic dye Direct Red 81 from its aqueous solution and all factors affecting the hydrogel adsorption capacity towards the anionic dye, like the hydrogel graft yield, the adsorbate pH, the immersion time and the hydrogel dose were studied. The data obtained from the adsorption results were found to fit well to the Langmuir adsorption model.     

Effective adsorption of phenolic compounds by functional group modified resins: behavior and mechanism

A series of functional hyper-crosslinked resins were successfully synthesized by incorporating amino, hydroxyl, and complex functional groups into post-crosslinked polymer. Possessing high specific surface area and effective functional groups, the newly synthesized resins showed excellent adsorption capacity toward various phenolic compounds. HC-IT displayed huge advantage over the others. Its adsorption capacity for salicylic acid was up to 336 mg/g, which was 3.01–6.64 times higher than that of the commercial resins and 2.33 times higher than its non-functionalized precursor HCLR (144 mg/g). The improved adsorption capacity was attributed to its high specific surface area, good polarity, and proper pore structure.     

Nitrogen and hydrogen adsorption of activated carbon fibers modified by fluorination

In this study, activated carbon fibers (ACFs) were surface modified with fluorine and mixed oxygen and fluorine gas to investigate the relationship between changes in surface properties by nitrogen and hydrogen adsorption capacity. The changes in surface properties of modified activated carbon fibers were investigated using X-ray photoelectron spectroscopy (XPS) and compared before and after surface treatment. The specific surface area and pore structures were characterized by the nitrogen adsorption isotherm at liquid nitrogen temperature. Hydrogen adsorption isotherms were obtained at 77 K and 1 bar by a volumetric method. The hydrogen adsorption capacity of fluorinated activated carbon fibers was the smallest of all samples. However, the bulk density in this sample was largest. This result could be explained by virial coefficients. The interaction of hydrogen-surface carbon increased with fluorination as the first virial coefficient. Also, the best fit adsorption model was found to explain the adsorption mechanism using a nonlinear curve fit. According to the goodness-of-fit, the Langmuir–Freundlich isotherm model was in good agreement with experimental data from this study.     

Separation of propene/1-alkene and ethylene/1-alkene copolymers by high-temperature adsorption liquid chromatography

A high performance liquid chromatography column (HPLC) Hypercarb^® packed with porous graphite has proven to discriminate polyolefin molecules due to differences in their adsorption and desorption behaviour. While linear polyethylene (PE) and syndiotactic polypropylene (sPP) are adsorbed on the graphite packing, isotactic polypropylene (iPP) is not adsorbed. The column operates at 160 °C with 1-decanol as sample solvent and mobile phase. We have now tested this HPLC system for separations of random propene/1-alkene and ethylene/1-hexene copolymers: While copolymers of propene with 1-butene, 1-hexene and 1-octene copolymers eluted in size exclusion mode without adsorption, propene/1-octadecene and ethylene/1-hexene copolymers are strongly retained and eluted only after application of a linear gradient starting from 1-decanol and ending with pure 1,2,4-trichlorobenzene. The retention of propene/1-alkene (>11 carbons in the side chain) copolymers increases with the concentration of comonomer, making this HPLC system suitable to separate these copolymers according to their chemical composition. In contrast, the retention of ethylene/1-hexene samples decreases with increasing 1-hexene content. Branching in this case shortens the length of continuous methylene sequences of the polymer backbone, which are expected to adsorb in a planar conformation to the graphite layers. This is the first report on the separation of short chain branched polyolefins by high-temperature adsorption liquid chromatography.     

Efficient adsorption to hexavalent chromium by iron oxalate modified D301:Characterization,performance and mechanisms

Chromium is a common harmful pollutant with high toxicity and low bearing capacity of soil and water. Excellent salinity resistance, a wide p H range, and high regeneration capacity were essential for qualified adsorbents used in removing hexavalent chromium(Cr(VI)) from polluted water. Herein, iron oxalate modified weak basic resin(IO@D301) for the removal of Cr(VI) was prepared by the impregnation method. The IO@D301 was characterized by scanning electron microscope(SEM), Fourier transform infrared spectroscopy(FTIR), X-Ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS). Owing to abundant amine, carboxyl groups and iron ions existing on the surface, IO@D301 possesses high adsorption and salinity resistance capacity for Cr(VI). The maximum adsorption capacity of IO301 towards Cr(VI) reached 201.30 mg·g~(-1) at 293 K and a p H of 5. The adsorption equilibrium was well fitted by the Freundlich model, and the adsorption process was described by the pseudofirst-order kinetics model as spontaneous and exothermic. The mechanism may be identified as electrostatic attraction, coordination, and reduction, which was confirmed by FT-IR and X-ray photoelectron spectroscopy.     

Effect of incorporation of crop residues and organic manures on adsorption/desorption and bio-availability of phosphate

Transformations of applied phosphorus (P) to unavailable residual soil P is the major cause of limited P supply in most of the P-deficient soils. The effect of the incorporation of crop residues (rice straw [RS] and wheat straw [WS]) and organic manures (farmyard manure [FYM] and green manure [GM]) on P release in soil and its bio-availability to various summer and winter crops was investigated in laboratory and screen house experiments. Surface (0–0.15 m) soil samples collected after 32 years of differential fertilization to maize–wheat–cowpea fodder crop rotation, were examined for adsorption/desorption behavior of P, after incubating with organics of varying C:P ratios. Incorporation of crop residues increased P adsorption maxima as well as resistance to P release in soils. Increased buffering capacities in crop residue-incorporated treatments decreased P desorption in soil, whereas the incorporation of organic manures decreased P sorption, maximum buffering capacity (MBC), bonding energy, and increased P concentration in soil solution. Although the incorporation of crop residues decreased P release in soil its bio-availability in the soil–plant system was crop-specific and varied with the time of incorporation of organics. Raya showed increased P uptake with incorporation of both RS and WS, whereas in the case of berseem increased P uptake occurred only with wheat straw. Phosphorus uptake in rice, maize, and soybean decreased with the incorporation of both RS and WS. Incorporation of crop residues 1 day before the sowing of summer crops decreased P uptake, whereas incorporation 3 weeks prior to the sowing of winter crops improved P bio-availability. Incorporation of organic manures with a narrow C:P ratio, however, improved P uptake in all the crops under investigation, in both the seasons. The results thus emphasized that adsorption parameters calculated from the examination of soil samples should not be used independently for making fertilizer P recommendations. Crop effects (root exudates) and their interaction with P reaction products in soil and synchronization in P release from organics and crop uptake need to be considered to understand the virtual behavior of P bio-availability in the soil–plant system.     

Differential water sorption studies on Kevlar 49 and as-polymerised poly (p-phenylene terephthalamide): adsorption and desorption isotherms

We have conducted differential water vapour sorption experiments on Kevlar^TM 49 at 30°C over a series of water vapour pressures from 0 to 90% of saturation, and on the as-polymerised form of the material at 30°C, 45°C and 60°C over a series of water vapour pressures of 0-60%, 0-25% and 0-15%, respectively. The equilibrium isotherms obtained for both samples show a distinct hysteresis-type behaviour. For Kevlar^TM 49, the hysteresis loop can be divided into two regions, namely above 30%, which is indicative of the presence of microvoids, and below 30%, which suggests inclusion of water into the intimate structure of the surface layer of the polymer crystallites, in a process known as intercalation.     

氧化石墨烯改性热致液晶聚芳酯的结构性能研究

采用原位聚合法,通过熔融共聚制备了HBA/HNA-GO液晶聚酯复合材料。研究了不同添加量的氧化石墨烯对纳米复合材料形态、结构和性能的影响。通过对复合材料的研究发现,氧化石墨烯的添加不会破坏TLCP原有的微观结构,且能够提高HBA/HNA液晶聚酯的热稳定性,为进一步研制高性能热致液晶聚芳酯提供了一个很好的方向。     

Improvement of CO2 adsorption on ZIF-8 crystals modified by enhancing basicity of surface

The imidazolate framework ZIF-8 samples were modified separately by using ammonia impregnation and thermal treatment in atmosphere of N₂ or H₂ in order to improve its adsorption property toward CO₂, and the modified samples A-ZIF-8, N-ZIF-8 and H-ZIF-8 were correspondingly available. The modified ZIF-8 samples were characterized, and the surface chemical properties of the ZIF-8 samples were determined separately by FTIR, CO₂-TPD, NH₃-TPD and H₂O-TPD. The isotherms of CO₂ on the modified ZIF-8 samples were measured. Results showed that after surface modification, the total amounts of basicity of the modified samples significantly increased, and followed the order: A-ZIF-8>H-ZIF-8>N-ZIF-8>O-ZIF-8. The uptakes of CO₂ increased proportionally with the basic groups on the surfaces of the ZIF-8 samples due to CO₂ being an acidic molecule. As a consequence of that, the CO₂ adsorption capacity of the samples followed the order: A-ZIF-8>H-ZIF-8>N-ZIF-8>O-ZIF-8. The amount adsorbed of CO₂ on the modified ZIF-8 sample by ammonia impregnation is the highest, having an increase.     

Methylene blue adsorption onto an eco-friendly modified polyacrylamide/graphite composites: Investigation of kinetics,equilibrium, and thermodynamic studies

ABSTRACT

Batch adsorption system using eco-friendly glucose and glucosamine grafted polyacrylamide/graphite composites were investigated to eliminate methylene blue (MB) dye from aqueous solution. The effect adsorption parameters reveal that pseudo-second order and Langmuir model exhibited good correlation with the adsorption kinetic and isotherm data for pollutant, respectively. Furthermore, an increase in pH from 2 to 11 was accompanied by an approximately fourfold increase in the amount of dye adsorbed. The maximum removal efficiency of MB was 96.23% under optimum conditions with equilibrium time of 40 min. The thermodynamic data supported its spontaneous and endothermic property of adsorption process. A possible adsorption mechanism has been proposed, where H-bonding and electrostatic interactions dominated the adsorption of dye.     

钛杂化笼型聚倍半硅氧烷吸附苯胺废水的动/热力学以及吸附机理研究

采用自行合成的一种新型钛硅固体材料——钛杂化笼型聚倍半硅氧烷,吸附处理质量浓度50 mg/L的苯胺废水。结果表明,当钛杂化笼型聚倍半硅氧烷用量2 g/L,pH值4.0,常温吸附20 min时,其吸附率达到64%。吸附符合Freundlich模型,属于优惠吸附等温线。通过计算获取ΔG0,ΔH0,ΔS0等吸附参数数据,证实了钛杂化笼型聚倍半硅氧烷吸附苯胺的趋势;同时依据参数值推测了苯胺分子在催化剂表面被吸附的机理。     

Application of numerical modeling of selective NOx reduction by hydrocarbon under diesel transient conditions in consideration of hydrocarbon adsorption and desorption process

A model of NO_x selective reduction by hydrocarbon (HC) was developed, which takes into account the adsorption and desorption of HC. The model was applied for predicting the performance of a De–NO_x catalytic reactor, working under transient conditions such as a legislative driving cycle. Diesel fuel was used as a supplemental reductant.

The behavior of HC and NO_x reactions and HC adsorption and desorption has been simulated successfully by our numerical approach under the transient conditions of the simulated Japanese 10–15 driving cycle. Our model is expected to optimize the design of selective diesel NO_x reduction systems using a diesel fuel as a supplemental reductant.     

Comprehensive evaluation of antibiotic tetracycline and oxytetracycline removal by Fe-metal organic framework/biopolymer-clay hydrogel

Tetracycline (TC) and oxytetracycline (OTC) are antibiotic compounds increasingly detected in various water sources. In this study, Fe-metal organic framework incorporated biopolymer-clay hydrogels (CAMIL-MMT and CAMIL-SEP) were prepared to remove TC and OTC from water. The physicochemical properties of the as-prepared hydrogels were thoroughly characterized, and the effect of various operating parameters on the adsorption performance was systematically examined. The CAMIL-MMT hydrogel showed the maximum adsorption capacity for TC and OTC (24.59 and 26.14 mg/g, respectively) compared to the CAMIL-SEP and other forms of biopolymer hydrogel precursors. The effects of the contact time and initial concentration on TC and OTC adsorption by CAMIL-MMT and CAMIL-SEP hydrogels were well suited to the pseudo-second-order kinetics and Freundlich isotherm models. The adsorption performance of CAMIL-MMT and CAMIL-SEP hydrogels slightly decreased with an increase in solution pH, while it was not much influenced by the co-existing anions. The thermodynamic study indicated that the reactions for the uptake of TC and OTC were spontaneous and highly favorable. Moreover, the as-synthesized CAMIL-MMT and CAMIL-SEP hydrogels demonstrated strong potential for reuse in TC and OTC removal with high reusability and strong stability. The photocatalysis study revealed that residual TC and OTC after adsorption could be further degraded by CAMIL-MMT and CAMIL-SEP hydrogels under visible light irradiation. From the above-mentioned results, the as-synthesized CAMIL-MMT and CAMIL-SEP hydrogels are promising to be considered alternative materials for the adsorptive and photocatalytic removal of TC and OTC in practical application of water and wastewater treatment.     

Cation transfer across a hydrogel/organic phase: Effect of cation size, hydrophobicity and acid-base properties

The transfers of tetraethylammonium (TEA⁺) and protonated triflupromazine (HTFP⁺) through a hydrogel/liquid interface (g/o) and a liquid/liquid interface (w/o) were compared using cyclic voltammetry. After the two phases were put in contact, the behavior of each molecule was analyzed at different pH values and at different time points. The gel induces hydrophobic and electrostatic interactions with TEA⁺ and HTFP⁺, shifting the peak potentials to more positive values. The diffusion coefficients, D, in both phases (g and w) at different pH values were calculated. In the case of TEA⁺, the D value remains constant in both systems. However, the D value of HTFP⁺ is lower in the gel phase than in the liquid phase.HTFP⁺ is transferred from the aqueous phase to the organic phase via a direct mechanism that involves coupled acid-base and partition processes. At the g/o interface, the coupled chemical reactions of HTFP⁺ were inhibited by the drug/gel interaction. The results demonstrate that the g/o system could be used as a model to study the controlled release of charged drugs.     

Determination of adsorption and kinetic parameters for methyl acetate esterification and hydrolysis reaction catalyzed by Amberlyst 15

In this paper, the adsorption equilibrium constants, dispersion coefficients, and kinetic parameters were obtained for the liquid phase reversible reaction of methanol with acetic acid catalyzed by Amberlyst 15. The adsorption and kinetic parameters are determined corresponding to two different mobile phases, methanol and water. Such parameters are required for three different applications of the model reaction: namely, synthesis of methyl acetate, removal of dilute acetic acid from wastewater, and hydrolysis of methyl acetate. Experiments were conducted in a packed bed reactor in the temperature range 313–323 K using a rectangular pulse input. A mathematical model for a quasi-homogeneous kinetics was developed. The adsorption and kinetic parameters together with their dependence on temperature were determined by tuning the simulation results to fit the experimentally measured breakthrough curves of acetic acid, water (or methanol) and methyl acetate using a state-of-the-art optimization technique, the genetic algorithm. The mathematical model was further validated using the tuned parameters to predict experimental results at different feed concentrations and flow rates. The kinetics reported in this study was obtained under conditions free of both external and internal mass transfer resistance. The computed parameters were found to predict experimental elution profiles for both batch and plug flow reactors reasonably well.     

Poly(N-vinyl-2-pyrrolidone) hydrogel production by ultraviolet radiation: new methodologies to accelerate crosslinking

Poly(N-vinyl-2-pyrrolidone) hydrogels produced by high-energy radiation relies on water radiolysis as a primary process leading to crosslinks. Conversely, ultraviolet direct irradiation into PVP leads to crosslinking trough pyrrolidinone moiety photolysis. However, this process showed to be rather inefficient. This work describes the crosslinking of poly(N-vinyl-2-pyrrolidone) based on hydrogen peroxide photolysis, therefore mimicking water radiolysis, using UV-C (e.g. low pressure Hg lamp) or UV-A radiation sources. The process efficiency and the properties of the hydrogel formed are discussed and compared with other methods of hydrogel production.     

Systematic investigation of SO2 adsorption and desorption by porous powdered activated coke: Interaction between adsorption temperature and desorption energy consumption

Porous carbon materials have been widely used for the removal of SO₂ from flue gas. The main objective of this work is to clarify the effects of adsorption temperature on SO₂ adsorption and desorption energy consumption. Coal-based porous powdered activated coke (PPAC) prepared in the drop-tube reactor was used in this study. The N₂ adsorption measurements and Fourier transform infrared spectrometer analysis show that PPAC exhibits a developed pore structure and rich functional groups. The experimental results show that with a decrease in adsorption temperature in the range of 50–150?℃, the adsorption capacity of SO₂ increases linearly; meanwhile, the adsorption capacity of H₂O increases, resulting in the increase in desorption energy consumption per unit mass of adsorbent. The processes of SO₂ and H₂O desorption were determined by the temperature-programmed desorption test, and the desorption energies for each species were calculated. Considering the energy consumption per unit of desorption and the total amount of adsorbent, the optimal adsorption temperature yielding the minimum total energy consumption of regeneration is calculated. This study systematically demonstrates the effect of adsorption temperature on the adsorption–desorption process, providing a basis for energy saving and emission reduction in desulfurization system design.     

A visible light photoinitiator system to produce acrylamide based smart hydrogels: Ru(bpy)3 as photopolymerization initiator and molecular probe of hydrogel microenvironments

A novel visible light bimolecular photoinitiator system (tris(2,2′-bipyridine)ruthenium(II)/N,N-dimethylaniline) is shown to be able to polymerize N-isopropylacrylamide (NIPAM) and 2-Acrylamido-2-Methylpropanesulfonic Acid (AMPS), in aqueous solution, to render high molecular weight polymers and crosslinked gels. The photoinitiator is especially useful to synthesize thermosensitive polymers and gels, because it could be used at temperatures below the phase transition, allowing the polymer chain to grow in its uncoiled state. The polymerization and conversion rates are affected by the structure of the monomer, decreasing in the order NIPAM > AAm > AMPS. The properties of the gels agree with literature data, suggesting that the method is able to produce conventional and smart hydrogels. The microenvironments present near linear polymers and inside crosslinked gels were investigated by measuring fluorescence lifetimes and steady state anisotropy of the metallic complex (Ru(bpy)₃⁺², present in the solution. Clear effects of the polymer presence on the photophysical properties of the complex are observed. Therefore, the same metallic complex could be used as photoinitiator of vinyl polymerization and as molecular probe to sense the hydrogel microenvironments.