Grafting of ion-imprinted polymers on the surface of silica gel particles through covalently surface-bound initiators: a selective sorbent for uranyl ion

A new ion imprinted polymer coated silica gel sorbent has been prepared using the radical "grafting from" polymerization method through surface-bound azo initiators for selective uranyl uptake. The introduction of azo initiator onto the silica surface was achieved by the reaction of surface amino groups with 4,4'-azobis(4-cyanopentanoic acid chloride). The grafting step was then carried out in a stirred solution of initiator-modified silica particles in the presence of uranyl ion and functional and cross-linking monomers. The prepared sorbent was characterized using FT-IR spectroscopy, scanning electron microscopy (SEM), elemental analysis (EA), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and BET adsorption isotherm analysis. The influence of the uranyl concentration, pH, and flow rate of solution on the grafted polymer affinity has been investigated. Maximum uptake of uranyl ion was observed at a pH 3.0. The rebinding behavior of the sorbent has been successfully described by the Langmuir-Freundlich isotherm. The dynamic column capacity of sorbent and enrichment factor for uranyl ion were 52.9 +/- 3.4 micromol g(-1) and 52, respectively. It was found that imprinting results in increased affinity of the sorbent toward uranyl ion over strong competitor metal ions such as Fe(III) and Th(IV). The sorbent was repeatedly used and regenerated for 3 months without any significant decrease in polymer binding affinities. Finally the sorbent was applied to the preconcentration and determination of uranyl ion in real water samples.     

Selective adsorption and separation of dibenzothiophene by molecularly imprinted polymer on the surface of porous magnetic carbon nanospheres

A molecularly imprinted polymer was deposited on the surface of porous magnetic carbon nanosphere to obtain a sorbent for dibenzothiophene. The molecularly imprinted polymer was synthesized by using porous magnetic carbon nanosphere as the support, dibenzothiophene as the template, methacrylic acid as the functional monomer and ethylene glycol dimethacrylate as the cross-linker. Field-emission scanning electron microscopy and Fourier-transformation infrared spectroscopy were used to characterize the morphology and structure of the sorbent. Adsorption results in terms of kinetics, isotherms and selective recognition adsorption indicate that the saturated adsorption amount of the sorbent towards dibenzothiophene reaches 32.00?mg g^?1 at 318 K within 40?min. The sorbent presents good selectivity for dibenzothiophene over benzothiophene with a relative selectivity coefficient of 1.70. The adsorption capacity of the sorbent towards dibenzothiophene still maintains 81.5% after five times of recycle, indicating that the obtained sorbent has excellent regeneration ability.     

Removal of chromium and toxic ions present in mine drainage by Ectodermis of Opuntia

This work presents conditions for hexavalent and trivalent chromium removal from aqueous solutions using natural, protonated and thermally treated Ectodermis of Opuntia. A removal of 77% of Cr(VI) and 99% of Cr(III) can be achieved. The sorbent material is characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, infrared spectroscopy, thermogravimetric analysis, before and after the contact with the chromium containing aqueous media. The results obtained from the characterization techniques indicate that the metal ion remains on the surface of the sorbent material. The percentage removal is found to depend on the initial chromium concentration and pH. The Cr(VI) and Cr(III) uptake process is maximum at pH 4, using 0.1g of sorbent per liter of aqueous solution. The natural Ectodermis of Opuntia showed a chromium adsorption capacity that was adequately described by the Langmuir adsorption isotherm. Finally, an actual mine drainage sample that contained Cd, Cr, Cu, Fe Zn, Ni and Pb was tested under optimal conditions for chromium removal and Ectodermis of Opuntia was found to be a suitable sorbent material. The use of this waste material for the treatment of metal-containing aqueous solutions as well as mine drainage is effective and economical.     

A packaging technique for polymer microfluidic platforms

A new technique, resin-gas injection, has been developed for bonding and surface modification of polymer microfluidic devices. This method can easily bond biochips with complex flow patterns. A cascade micromixer and a multichannel DNA sequencing chip were demonstrated experimentally. By adding surface modification agents, the interfacial free energy of the substrate with water can be controlled. Local modification of the channel surface can also be achieved through sequential resin-gas injection in conjunction with a masking technique. For application, this technique is used to form a layer of dry monolithic stationary hydrogel on the walls of a microchannel, serving as a sieving material for electrophoresis separation of DNA fragments. The reagent loading and the electrophoresis separation efficiency of this technique were compared experimentally with the conventional linear polymer solution method used in the microchannel-based DNA sequencing process. It is found that our method has the advantages of more user-friendly operation, easier and faster sample loading, but slightly less separation efficiency.     

Controlling microarray spot morphology with polymer liftoff arrays

Biological arrays are hindered by the lack of uniformity in the deposition of biomaterials. Efforts aimed at improving this deposition have focused on altering the composition of the solution or the tool used to deposit the material. However, little attention has been paid to controlling material deposition by constraining the physical and chemical topography of the surface. Here we present the use of a hybrid hydrophilic/hydrophobic micropatterned surface to direct the deposition of spotted DNA on microarrays. These polymer "liftoff" arrays combine the hydrophobic surface properties of di-p-xylylene (Parylene) with photolithographically etched hydrophilic openings within the polymer. We show that the flow pattern of solutes on these substrates favors the concentration of dissolved material into the mesoscopic openings underlying the printed spot, resulting in significantly improved uniformity of deposition. Moreover, the micropatterned surface allows for increased replication of spotted materials. Finally, these polymer liftoff arrays display reduced array-to-array variation, improving the reproducibility of data acquisition. We envision that these novel substrates can be generalized to produce more uniform arrays of other patterned biomaterials.     

Redox polymer and probe DNA tethered to gold electrodes for enzyme-amplified amperometric detection of DNA hybridization

The detection of nucleic acids based upon recognition surfaces formed by co-immobilization of a redox polymer mediator and DNA probe sequences on gold electrodes is described. The recognition surface consists of a redox polymer, [Os(2,2'-bipyridine)2(polyvinylimidazole)(10)Cl](+/2+), and a model single DNA strand cross-linked and tethered to a gold electrode via an anchoring self-assembled monolayer (SAM) of cysteamine. Hybridization between the immobilized probe DNA of the recognition surface and a biotin-conjugated target DNA sequence (designed from the ssrA gene of Listeria monocytogenes), followed by addition of an enzyme (glucose oxidase)-avidin conjugate, results in electrical contact between the enzyme and the mediating redox polymer. In the presence of glucose, the current generated due to the catalytic oxidation of glucose to gluconolactone is measured, and a response is obtained that is binding-dependent. The tethering of the probe DNA and redox polymer to the SAM improves the stability of the surface to assay conditions of rigorous washing and high salt concentration (1 M). These conditions eliminate nonspecific interaction of both the target DNA and the enzyme-avidin conjugate with the recognition surfaces. The sensor response increases linearly with increasing concentration of target DNA in the range of 1 x 10(-9) to 2 x 10(-6) M. The detection limit is approximately 1.4 fmol, (corresponding to 0.2 nM of target DNA). Regeneration of the recognition surface is possible by treatment with 0.25 M NaOH solution. After rehybridization of the regenerated surface with the target DNA sequence, >95% of the current is recovered, indicating that the redox polymer and probe DNA are strongly bound to the surface. These results demonstrate the utility of the proposed approach.     

Effect of the dielectric layer with photo-controllable surface relief on liquid crystal devices

We present experimental results for the dielectric layer effect on the electro-optical properties of liquid crystal (LC) devices together with numerical simulations. The photo-controllable polymer is used as a dielectric material on which the alignment agent of the LC is prepared. The surface relief structure can be induced on the dielectric polymer layer by photo-irradiation for fabricating LC microlens arrays or wide-viewing LC displays. It is found that the operation voltage of the LC device decreases with increasing the dielectric constant or with decreasing the layer thickness of the polymer. The experimental data agree well with theoretical results predicted from a simple dielectric model in the continuum theory.     

Sorption properties of hypercrosslinked polystyrene sorbents

Sorption properties of a new type of nonspecific sorbent—hypercrosslinked polystyrene—with respect to vapors of organic solvents (alkanes, acetone, methanol) and water have been studied. The sorption capacity of the hypercrosslinked sorbent is shown to be many times greater than that of conventional organic and inorganic porous sorbents. The polystyrene sorbent can be easily regenerated at 80°C. The ultimate values of vapor sorption reach 1.2 cm³/g; they do not depend on the type of organic solvent but are determined by the peculiarities of the hypercrosslinked sorbent structure. The sorption of vapors of organic substances is accompanied by swelling of the polymer, which is partially irreversible. Hysteresis loops do not arise from capillary condensation, but are rather caused by the rearrangement of the sorbent's internal structure in the course of vapor adsorption. Temperature decrease at small p/p₀ values is shown to lead to a decrease in the magnitude of sorption, which is explained by a decrease in the mobility of the hypercrosslinked polymer network in the temperature range of 0–10°C.     

Studies on sorption of Cd(II) on Tata chromite mine overburden

Chromite mine overburden containing iron as oxide/hydroxide, a waste material generated in chromite mines was used as sorbent for cadmium. The iron content of material was 43.75% with a specific surface area of 50.8m(2)/g. Batch experiments were conducted to study the sorption behavior of Cd(II) on this material. The variable experimental parameters were: time, pH, temperature, Cd(II) and sample concentration. The point of zero charge (PZC) of the overburden sample was experimentally determined as 6.48 which shifted to a pH of 7.8 when the sample was equilibrated with 100 mg/L Cd(II) solution. Maximum loading capacity of the overburden sample was found to be approximately 19 mg Cd/g of material. It was observed that within 30 min the sorption attains equilibrium. Hence, the sorption data generated at 30 min with various initial Cd(II) concentrations and temperatures were taken to evaluate the thermodynamic parameters, i.e., DeltaG degrees , DeltaH degrees and DeltaS degrees . The DeltaG degrees values reflect the feasibility of the metal removal from aqueous solution. The negative values of DeltaH degrees confirmed the exothermic sorption of cadmium and the positive DeltaS degrees values suggested the increased randomness at the solid-solution interface. The sorption data fitted well to both the Langmuir and Freundlich isotherm models indicating a monolayer sorption. The value of Freundlich parameter 'n' (n is indicative of sorption intensity) lying between 1.46 and 1.59 shows that the surface of the sorbent is heterogeneous in nature.     

Evaluation of various additives on the preparation of rice husk ash (RHA)/CaO-based sorbent for flue gas desulfurization (FGD) at low temperature

This paper examines the effectiveness of 10 additives toward improving SO2 sorption capacities (SSC) of rice husk ash (RHA)/lime (CaO) sorbent. The additives examined are NaOH, CaCl2, LiCl, NaHCO3, NaBr, BaCl2, KOH, K2HPO4, FeCl3 and MgCl2. Most of the additives tested increased the SSC of RHA/CaO sorbent, whereby NaOH gave highest SSC (30mg SO2/g sorbent) at optimum concentration (0.25mol/l) compared to other additives examined. The SSC of RHA/CaO sorbent prepared with NaOH addition was also increases from 17.2 to 39.5mg SO2/g sorbent as the water vapor increases from 0% RH to 80% RH. This is probably due to the fact that most of additives tested act as deliquescent material, and its existence increases the amount of water collected on the surface of the sorbent, which played an important role in the reaction between the dry-type sorbent and SO2. Although most of the additives were shown to have positive effect on the SSC of the RHA/CaO sorbent, some were found to have negative or insignificant effect. Thus, this study demonstrates that proper selection of additives can improve the SSC of RHA/CaO sorbent significantly.     

Novel Magnetic Cobalt Cyanoferrate Nanoparticles as Potential Sorbent for Solid-Phase Extraction of Radionuclides from Aqueous Samples

A composite material based on magnetite and K₂[CoFe(CN)₆] was prepared. Structural and morphological studies of the sorbent were carried out, and the specific surface area was determined. The crystal structure of the material was studied by X-ray diffraction, and the composition was evaluated by energy-dispersive X-ray spectroscopy. Sorption of radionuclides was studied in batch experiments in relation to pH of the solution, mass of the adsorbent, and contact time. The adsorption kinetics was examined, the adsorption isotherm was constructed, and the adsorption capacity was determined. The resistance of the material to radiation to a dose of 250 kGy was evaluated. The material efficiently removes Cs and Am radionuclides from aqueous solutions. The sorbent seems to be sufficiently stable for practical use in the treatment of radioactive waste.     

粉煤灰陶粒在污水处理中的应用进展

粉煤灰陶粒是由粉煤灰为主要原料，掺加少量粘结剂和固体燃料，经混合、成球、高温焙烧而成。由于其比表面积大、表面能高，且内部存在着铝、硅氧化物等活性点，具有良好的吸附性能，并且易于再生，便于重复利用，因此粉煤灰陶粒是一种廉价的吸附剂。综述了粉煤灰陶粒用作水处理滤料以及其在含金属离子的废水、腐殖废水、含磷废水、含氟废水、含油废水处理中的应用，并对今后的研究方向进行了展望。     

The formation of nanostructured carbon material on a ferrocene-containing polymer surface induced by a high-power ion beam

The surface morphology and the composition of polymer layers based on chlorinated polyvinylchloride with addition of ferrocene (up to 10% of the polymer mass) subject to the action of a nanosecond high-power ion beam are studied. It is demonstrated that carbon material in the form of nanofibers with an average diameter of 80 nm and a length of up to 10 μm is formed on a surface singly irradiated by such beam with a current density of ～100 A/cm². A possible mechanism of the observed phenomenon is discussed.     

Sorption of As(V) from aqueous solution using acid modified carbon black

The sorption performance of a modified carbon black was explored with respect to arsenic removal following batch equilibrium technique. Modification was accomplished by refluxing the commercial carbon black with an acid mixture comprising HNO(3) and H(2)SO(4). Modification resulted in the substantial changes to the inherent properties like surface chemistry and morphology of the commercial carbon black to explore its potential as sorbent. The suspension pH as well as the point of zero charge (pH(pzc)) of the material was found to be highly acidic. The material showed excellent sorption performance for the removal of arsenic from a synthetic aqueous solution. It removed approximately 93% arsenic from a 50mg/L solution at equilibration time. The modified carbon black is capable of removing arsenic in a relatively broad pH range of 3-6, invariably in the acidic region. Both pseudo-first-order and second-order kinetics were applied to search for the best fitted kinetic model to the sorption results. The sorption process is best described by the pseudo-second-order kinetic. It has also been found that intra-particle diffusion is the rate-controlling step for the initial phases of the reaction. Modelling of the equilibrium data with Freundlich and Langmuir isotherms revealed that the correlation coefficient is more satisfactory with the Langmuir model although Freundlich model predicted a good sorption process. The sorption performance has been found to be strongly dependent on the solution pH with a maximum display at pH of 5.0. The temperature has a positive effect on sorption increasing the extent of removal with temperature up to the optimum temperature. The sorption process has been found to be spontaneous and endothermic in nature, and proceeds with the increase in randomness at the solid-solution interface. The spent sorbent was desorbed with various acidic and basic extracting solutions with KOH demonstrating the best result ( approximately 85% desorption).     

DNA Polymer Brush Patterning through Photocontrollable Surface‐Initiated DNA Hybridization Chain Reaction

The fabrication of DNA polymer brushes with spatial resolution onto a solid surface is a crucial step for biochip research and related applications, cell‐free gene expression study, and even artificial cell fabrication. Here, for the first time, a DNA polymer brush patterning method is reported based on the photoactivation of an ortho‐nitrobenzyl linker‐embedded DNA hairpin structure and a subsequent surface‐initiated DNA hybridization chain reaction (HCR). Inert DNA hairpins are exposed to ultraviolet light irradiation to generate DNA duplexes with two active sticky ends (toeholds) in a programmable manner. These activated DNA duplexes can initiate DNA HCR to generate multifunctional patterned DNA polymer brushes with complex geometrical shapes. Different multifunctional DNA polymer brush patterns can be fabricated on certain areas of the same solid surface using this method. Moreover, the patterned DNA brush surface can be used to capture target molecules in a desired manner.     

PCEC-CaO-SiO_2-P_2O_5杂化材料

采用分子量为1 500的聚乙二醇(PEG)为大分子引发剂,引发ε-己内酯开环聚合,合成了分子量为2 900、3 400、4 700的端羟基的聚己内酯-聚乙二醇-聚己内酯(PCEC)嵌段共聚物,并用异氰酸基丙基三乙氧基硅烷(IPTS)将该共聚物端羟基修饰。红外结果表明,该聚合物在3 440、1 732、1 242、1 106cm-1等处有羟基、酯键、醚键的特征峰,与IPTS反应后在3 350cm-1、1 531cm-1处出现了N—H的伸缩振动峰和(N—H)+(C—N)的弯曲振动峰,证实了PCEC以及端基为三乙氧基硅基的PCEC结构。采用溶胶-凝胶法将该产物与生物玻璃前躯体进行反应,获得PCEC-CaO-SiO2-P2O5有机-无机杂化材料。PCEC-CaO-SiO2-P2O5杂化材料在模拟体液(SBF)中浸泡24h后,表面就开始覆盖钙磷沉淀物。XRD测试结果表明,PCEC-CaO-SiO2-P2O5杂化材料表面覆盖的沉淀物主要成分为羟基磷灰石,表面沉积物随着杂化材料中亲水性成分的增加而增加。力学性能测试表明,随着高分子中PEG含量的增加,PCEC-CaO-SiO2-P2O5有机-无机杂化材料的压缩模量从6.9 MPa上升到65 MPa。细胞毒性表明,PCEC-CaO-SiO2-P2O5杂化材料对细胞没有明显的毒性。     

香蒲绒纤维对大豆油的吸收性能研究

利用蒲绒纤维作为吸油材料对含油废水中的大豆油进行处理.研究了该材料对纯大豆油以及含水大豆油的吸收能力,并研究了材料的重复利用性能,结果表明,香蒲绒纤维对大豆油有很好的吸收能力,1g纤维能吸收15～20g的油.吸油后纤维通过挤压即可重复利用,且经过5次重复试验后1g纤维仍能吸收6～10g的油.     

Characterization of a polymeric adsorbed coating for DNA microarray glass slides

A new method was developed to covalently attach target molecules onto the surface of glass substrates such as microwell plates, beads, tubes, and microscope slides, for hybridization assays with fluorescent targets. The innovative concept introduced by this work is to physically adsorb onto underivatized glass surfaces a functional copolymer, able to graft amino-modified DNA molecules. The polymer, obtained by radical copolymerization of N,N-dimethylacrylamide, N-acryloyloxysuccinimide, and 3-(trimethoxysilyl)propyl methacrylate, copoly(DMA-NAS-MAPS), self-adsorbs onto the glass surface very quickly, typically in 5-30 min. The film, formed on the surface, bears active esters, which react with amino-modified DNA targets. The surface layer is stable in an aqueous buffer containing various additives (SDS, urea, salt), even at boiling temperature. It should be emphasized that the coating is formed by the immersion of glass slides in a diluted aqueous solution of the polymer. Therefore, the procedure is fast, inexpensive, robust, and reliable, and it does not require time-consuming glass pretreatments. Slides, coated with copoly(DMA-NAS-MAPS), were profitably used as substrates for the preparation of low-density DNA microarrays. The density and the thickness of the films were evaluated by X-ray reflectivity measurements whereas the extent of reaction of functional groups with DNA molecules was determined by a functional test. The experiments indicate that half of the active groups present on the surface reacts with oligonucleotide probes.     

Outgassing characteristics of a polycarbonate core material for vacuum insulation panels

Performance deterioration with time is one of the most important issues in a vacuum insulation panel (VIP), which is mostly due to the inner gas pressure rise. Outgassing from the interior of core materials is the major gas source when the core material is a polymer. Outgassing characteristics of a polycarbonate as the VIP’s core material are examined theoretically and experimentally. To measure the outgassing rate, specific outgassing tests are carried out using a pressure rise method. Diffusive outgassing mechanism is discussed based on the Fick’s law. As the result, the total amount of dissolved gas and the diffusion coefficients of various gases in the polycarbonate are obtained by using the measured outgassing rate. Temperature dependence of the diffusion coefficient of nitrogen is also examined. It is shown that the outgassing rate of polymer core materials can be significantly reduced to a negligible level by a baking pre-treatment in vacuum and/or by a metal coating on the polymer surface.     

The visualization of water transport through hydrophobic polymer coatings applied to building sandstones by broad line magnetic resonance imaging

It is shown that broad line gradient echo magnetic resonance imaging is an ideal tool with which to study the ingress of hydrophobic polymer surface treatments into porous building materials, specifically in this case sandstone. It is further shown that the method can be used to quantitatively visualize the movement of water into and through the treated material, both from the surface and bulk, as a function of time. The influence of treatment cure time, cure temperature and substrate hydration on the subsequent water transport have been investigated. For the first time direct evidence of water pumping through a treated surface is presented.