Separation of different forms of proteose peptone 3 by hydrophobic interaction chromatography with a dual salt system

A panel of four hydrophobic adsorbents (butyl-, octyl-, phenyl- and epoxy-Sepharose) was used to examine the selectivity and fractionation of several proteose peptone 3 (PP3) forms from a freeze-dried extract of whey bovine milk. In particular, the effects of altering the ligand type and salt were investigated. The chromatographic studies suggest that PP3 strongly interacts among the three commercial hydrophobic resins leading to a drop off in selectivity, while a complete binding was achieved at low salt concentrations (below 0.5 m) and total elution only with phosphate buffer and/or water stepwise conditions. Only in epoxy-Sepharose was an appreciably selectivity of the several fractions of PP3 present in the initial feedstock attained. Despite the high salt concentration for a complete binding of PP3 (above 1.5 m ammonium sulfate) onto this support, the dual salt system (ammonium sulfate 1 m and sodium citrate 0.8 m) led to a high separation degree of high and low molecular weight forms of PP3.     

Chitosan macroporous asymmetric membranes—Preparation,characterization and transport of drugs

Chitosan macroporous membranes with asymmetric morphology were obtained by using an inorganic porogen agent (SiO₂). Chitosan/silica ratios used were 1:1, 1:3, and 1:5 w/w. A methodology to obtain asymmetric membranes with control of porosity and average pore size was proposed. The porous membranes were obtained taking advantage of the opposite solubility characteristics of chitosan and silica (4–20 μm). The membranes were characterized by SEM and water sorption capacity. The porosity was calculated by the relationship between dense and macroporous membranes. The SEM images of both surfaces and cross-section of the membranes confirmed their asymmetric morphology. Using a double-cell method, the permeability coefficients of two model drugs (sodium sulfamerazine and sulfametoxipyridazine) were determined. The effects of porous layer, drug type, concentration and temperature were evaluated. The results revealed that the increase in porosity results in significant differences in permeability and that the effects of drug concentration and bath temperature become less pronounced as porosity increases. The mass transport was analyzed in terms of pore-flow mechanism and the solution-diffusion mechanism. The results showed that the methodology was very efficient to yield asymmetric membranes with good mechanical resistance, control of porous size and dense layer thickness and that these membranes can potentially be used to the transport of drugs.     

Adsorption of toluene, methylcyclohexane and neopentane on silica MCM-41

Adsorption-desorption isotherms of toluene, methylcyclohexane and neopentane were determined on a silica MCM-41 material of pore diameter ∼3.4 nm over the temperature range 258 K to 308 K (278 K for neopentane). The isosteric enthalpies of adsorption were determined from the isotherms at the various temperatures. It was found that the isotherms of toluene and methylcyclohexane have a similar variation with the temperature, exhibiting hysteresis at 268 K and at lower temperature, while the adsorption of neopentane is reversible at all temperatures. The three organic adsorptives interact differently with the silica surface and the isosteric enthalpies of adsorption indicated that methylcyclohexane has the weakest interaction and toluene the strongest. A slight increase in the adsorption enthalpy at the beginning of the capillary condensation step is observed with methylcyclohexane and neopentane but not with toluene.     

Effect of thermal annealing on Nd<Subscript>2</Subscript>O<Subscript>3</Subscript>-doped silica powder prepared by the solgel process

A novel sorbent for the removal of heavy metals, hydroxyapatite/poly (vinyl alcohol) cryogel, was studied. The HAp/PVA cryogel was characteristic of macroporous structure. The experiments for Cd²⁺ sorption by HAp/PVA cryogel were conducted at various operating conditions such as sonication, sorption time, Cd²⁺ concentration, temperature, pH, and HAp/PVA mass ratio. It was concluded that the sorption was considerably affected by sorption time, Cd²⁺concentration, temperature and HAp/PVA mass ratio. Nevertheless, there was slight dependence of sorption on sonication and pH. The influences of different parameters were discussed in detail in the paper. The main mechanism was suggested to be ion-exchange.     

Adsorption kinetics for arsenic removal from aqueous solutions by untreated powdered eggshell

The batch removal of arsenic from aqueous solution using low-cost adsorbent (powdered eggshell) under the influences of initial arsenic ion concentrations (0.50 to 1.50 mg/L), pH (3.2 to 11.5) and particle size of eggshells (63 to 150 μm) were investigated. Eggshells were collected from Obafemi Awolowo University, Ile-Ife, washed with distilled water, air dried, ground into powder and sieved into different sieve sizes using British standard sieve. Powdered eggshells were stored in a desiccator for use. Adsorption isotherms and dynamics of arsenic onto PES were studied. The study revealed that there was a slight reduction in the rate of adsorption of arsenic ion onto the larger particle size, but adsorption capacity and parameters were unaffected. Powdered eggshell with particle size of 63 μm removed up to 99.6% of the 1.5 mg/L of arsenic ion in synthetic water within the first 6 hours but decreased to 98.4% and 97.4% when the powdered eggshell particle sizes were increased to 75 and 150 μm respectively. The pH optimum for arsenic removal was 7.2. The adsorption isotherms and adsorption dynamic kinetic studied through the use of graphical method revealed that Freundlich, activated sludge adsorption and pseudo second-order kinetic models correlate significantly with the experimental data with correlation coefficient of not less than 0.964.     

大孔吸附树脂分离纯化香椿叶总黄酮的研究

比较了AB-8、S-8、X-5、NKA-9、D-3520、NKA、聚酰胺、硅胶8种吸附剂对香椿叶黄酮类化合物的吸附及脱附性能.在静态吸附试验的基础上,筛选出效果较好的X-5树脂进行动态试验研究.结果表明,X-5树脂在约15℃下对香椿叶总黄酮动态吸附-脱附较优的工艺参数为:上柱液pH值5～6,上柱速度3BV/h,溶液处理量6BV/次;脱附剂为70%乙醇,脱附剂的流速3BV/h,脱附剂用量6BV/次.此工艺条件能够分离纯化香椿叶黄酮类化合物,树脂使用1次时,总黄酮的收率达95.5%,总黄酮的纯度由7.2%提高到43.5%;树脂重复使用5次时,总黄酮的收率仍达80%以上,总黄酮的纯度可由7.2%提高到20%以上.     

Bilirubin Removal by Polymeric Adsorbents for Hyperbilirubinemia Therapy

Hyperbilirubinemia, presenting as jaundice, is a life-threatening critical illness in newborn babies and acute severe hepatic failure patients. Over the past few decades, extracorporeal hemoadsorption by adsorbent therapy has been widely applied in the treatment of hyperbilirubinemia. The capability of hemoadsorption depends on the adsorbents. Most of the clinically used bilirubin adsorbents are made up of styrene/divinylbenzene copolymer and quaternary ammonium salt, which usually have poor biocompatibility and weak mechanical strength. To overcome the drawbacks of commercial polymer adsorbents, advanced synthetic and natural polymers with/without nanomaterials have been designed, and novel adsorbent fabrication technologies have also been developed. In this review, the adsorption mechanism of bilirubin adsorbents has been summarized, which is the basic criterion in adsorbent development. Furthermore, the preparation method, adsorption mechanism, relative merits and practicability of the emerging bilirubin adsorbents have been evaluated. Based on the existing studies, this work highlights the future direction of the efforts on how to design and develop bilirubin adsorbents with good overall clinical performance. Perhaps this study can change traditional perspectives and propose new strategies for bilirubin clearance from the aspects of pathogenic mechanisms, metabolic pathways, and material-based innovation.     

The preparation of high-capacity boronate affinity adsorbents by surface initiated reversible addition fragmentation chain transfer polymerization for the enrichment of ribonucleosides in serum

Boronate affinity adsorption is uniquely selective for cis-diol-containing molecules. The preparation and application of boronate affinity materials has attracted much attention in recent years. In this work, a high-capacity boronate affinity adsorbent was prepared by surface-initiated reversible addition–fragmentation chain transfer polymerization (SI-RAFT). Commercial aminated poly(glycidyl methacrylate) (PGMA) microspheres were modified with the chain transfer agent (CTA) S-1-dodecyl-S-(α,α-dimethyl-α-acetic acid)trithiocarbonate (DDATC). Boronate-affinity adsorbents were then prepared via SI-RAFT polymerization employing 3-acrylamidophenylboronic acid (AAPBA) as the monomer. The Fourier transform infrared spectroscopy (FT-IR), nitrogen adsorption and desorption measurements have proven the successful grafting of AAPBA on PGMA microspheres surface. The boronate affinity adsorbents thus prepared possess much higher adsorption capacity (99.2 µmol/g of adenosine) and both faster adsorption and desorption speed towards ribonucleosides, the adsorption and desorption could be completed in 2 min. The high selectivity of the adsorbents to ribonucleosides was verified in the presence of a large excess of deoxynucleosides. The boronate affinity adsorbents were then employed for sample pretreatment before HPLC analysis of ribonucleosides in serum. The ribonucleosides were effectively enriched by boronate affinity dispersive solid-phase extraction (BA-DSPE), with high mass recoveries and good precision. The simultaneous determination of uridine and guanosine in calf serum was achieved by utilizing the standard addition method, their contents were determined to be 170 ± 11.6 ng/mL and 39.6 ± 4.4 ng/mL respectively. The results proved that the prepared boronate affinity materials could be applied for sample pretreatment of cis-diol containing molecules in biological samples.     

Impregnation synthesis of a novel macroporous silica-based TODGA polymeric composite and its application in the adsorption of rare earths in nitric acid solution containing diethylenetriaminepentaacetic acid

A macroporous silica-based N,N,N′,N′-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) polymeric composite (TODGA/SiO₂-P) was synthesized. It was done through impregnation and immobilization of TODGA molecule into the pores of the SiO₂-P particles utilizing a vacuum sucking technique. The macroporous SiO₂-P particles were the silica-based organic/inorganic composite synthesized by immobilizing styrene-divinylbenzene copolymer inside SiO₂ through the complicated polymerization reaction. The adsorption of rare earth (RE(III)) elements onto TODGA/SiO₂-P was investigated in HNO₃ solution containing diethylenetriaminepentaacetic acid (DTPA), an acidic multi-dentate chelating agent. It was found that in the presence of 0.05 M DTPA, and H⁺ had significant effect on the TODGA/SiO₂-P adsorption due to the competition reactions of RE(III) with different species, H₄DTPA⁻ and H₂DTPA³⁻. With an increase in the concentration of from 0.115 M to 3.015 M, the adsorption of RE(III) onto TODGA/SiO₂-P increased noticeably. On the other hand, RE(III) showed strong adsorption at 0.1 M H⁺, weak adsorption at around pH 2, and no adsorption in excess of pH 2.3. In a 0.1 M H⁺-0.115 M -0.05 M DTPA solution, a change of the distribution coefficient of RE(III) onto TODGA/SiO₂-P with an increase in atomic number of RE(III) from La(III) to Lu(III) was investigated. The silica-based TODGA/SiO₂-P polymeric composite showed strong adsorption for heavy RE(III) over the light one. In a 0.01 M H⁺-1.0 M -0.05 M DTPA solution, the effect of the ratio of solid phase to liquid one on the relationship of the distribution coefficient of RE(III) with the change in atomic number of RE(III) was also studied. Based on the complicated disassociation equilibrium of DTPA, the influence of the concentrations of and H⁺ on the adsorption of TODGA/SiO₂-P for RE(III) was demonstrated. This makes the partitioning of RE(III) and MA(III) together from high level liquid waste (HLLW) by the polymeric composite TODGA/SiO₂-P promising.     

One-Step Preparation of Chitosan-Based Magnetic Adsorbent and Its Application to the Adsorption of Inorganic Arsenic in Water

Chitosan is a kind of biodegradable natural polysaccharide, and it is a very promising adsorber material for removing metal ions from aqueous solutions. In this study, chitosan-based magnetic adsorbent CMC@Fe₃O₄ was synthesized by a one-step method using carboxymethyl chitosan (CMC) and ferric salts under relatively mild conditions. The Fe₃O₄ microspheres were formed and the core–shell structure of CMC@Fe₃O₄ was synthesized in the meantime, which was well characterized via SEM/TEM, XRD, VSM, FT-IR, thermo gravimetric analysis (TGA), XPS, size distribution, and zeta potential. The effects of initial arsenic concentration, pH, temperature, contact time, and ionic strength on adsorption quantity of inorganic arsenic was studied through batch adsorption experiments. The magnetic adsorbent CMC@Fe₃O₄ displayed satisfactory adsorption performance for arsenic in water samples, up to 20.1 mg/g. The optimal conditions of the adsorption process were pH 3.0, 30−50 °C, and a reaction time of 15 min. The adsorption process can be well described by pseudo-second-order kinetic model, suggesting that chemisorption was main rate-controlling step. The Langmuir adsorption model provided much higher correlation coefficient than that of Freundlich adsorption model, indicating that the adsorption behavior is monolayer adsorption on the surface of the magnetic adsorbents. The above results have demonstrated that chitosan-based magnetic adsorbent CMC@Fe₃O₄ is suitable for the removal of inorganic arsenic in water.