Bulk synthesis of ordered macroporous silica particles for superhydrophobic coatings

The molecular interaction between tetrabutylammonium iodide (TBAI) and cellulose and its potential application for the adsorption of chromium is discussed in this paper. The biosorbent was prepared under solvent free conditions using microwave irradiation. A subtle balance between electrostatic and the hydrophobic effects governs the interaction of biopolymer with the surfactant. The interaction between the biosorbent and chromium was comprehensively studied using spectroscopic, thermal and surface analysis techniques. The various analytical parameters that influence the adsorption were optimized, and the maximum adsorption capacity of Cr(VI) obtained from the Langmuir isotherm model was found to be 16.67 mg g(-1). The sorption thermodynamics indicated the spontaneity and exothermic nature of adsorption. The biosorbent could be effectively regenerated using NaOH, which imparts greener aspect to the overall process.     

Ultrasound-assisted preparation and characterization of crystalline cellulose-ionic liquid blend polymeric material: a prelude to the study of its application toward the effective adsorption of chromium

The molecular interaction of biopolymers with an array of substrates offers interesting insight into the adsorption phenomenon. The present work proposes the preparation and characterization of cellulose-methyltrioctylammonium chloride (MeTOACl)-a room temperature ionic liquid (IL) blend polymeric sorbent and its application for the adsorption of carcinogenic chromium(VI). The blend adsorbent material was synthesized in a relatively green solvent (methylisobutylketone) medium by ultrasonication. The mechanism of interaction of biopolymer with the ionic liquid could be conceptualized as electrostatic attraction, hydrogen bonding, and Van der Waals force of attraction with the hydroxyl groups of cellulose as a bilayer assembly. The composition, crystallinity, and the surface area of the prepared material were comprehensively characterized using FT-IR, solid-state (13)C NMR, TGA, XRD, SEM, EDX, XPS, and BET isotherm study. The adsorption capacity of chromium(VI) calculated from Langmuir isotherm model was found to be 38.94 mg g(-1) with adherence to the second-order kinetics. The study of thermodynamic parameters that affect the sorption process indicated the spontaneity and exothermic nature of adsorption. The green aspect in the methodology is brought out in the regeneration of the adsorbent, where Cr(VI) could be effectively reduced to the less toxic Cr(III) using ascorbic acid.     

Solid phase extraction of chromium(VI) from aqueous solutions by adsorption of its diphenylcarbazide complex on a mixed bed adsorbent (acid activated montmorillonite-silica gel) column

A novel approach has been developed for the solid phase extraction of chromium(VI) based on the adsorption of its diphenylcarbazide complex on a mixture of acid activated montmorillonite (AAM)-silica gel column. The effect of various parameters such as acidity, stability of the column, sample volume, interfering ions, etc., were studied in detail. The adsorbed complex could be easily eluted using polyethylene glycol-sulfuric acid mixture and the concentration of chromium has been determined using visible spectrophotometry. The calibration graph was linear in the range 0-1microgmL(-1) chromium(VI) with a detection limit of 6microgL(-1). A highest preconcentration factor of 25 could be obtained for 250mL sample volume using glass wool as support for the mixed bed adsorbent. Chromium(VI) could be effectively separated from other ions such as nickel, copper, zinc, chloride, sulfate, nitrate, etc., and the method has been successfully applied to study the recovery of chromium in electroplating waste water and spiked water samples.     

Reusable chromium-coated quartz crystal microbalance for immunosensing

The application of oxidized chromium as a reusable platform for the development of immunosensors is presented. Chromium films were deposited on quartz crystal microbalances to study the affinity interaction between rabbit immunoglobulin G (IgG) and goat anti-rabbit IgG. A covalent approach, based on the silane chemistry, was followed for the grafting of either the rabbit IgG or the anti-rabbit IgG on the silane-modified chromium surface. Next the differences between the deposition of rabbit IgG on immobilized anti-rabbit IgG and the deposition of anti-rabbit IgG on immobilized rabbit IgG were investigated. The chromium layer could be reused between experiments, after the proper removal of the organic layers with piranha etch, obtaining a high repeatability in the steps of the functionalization protocol.     

Separation,preconcentration and speciation of chromium by solid phase extraction on immobilised ferron

A sensitive and simple method for determination of chromium species after separation and preconcentration by solid phase extraction (SPE) has been developed. For the determination of the total concentration of chromium in solution, Cr(VI) was efficiently reduced to Cr(III) by addition of hydroxylamine and Cr(III) was preconcentrated on a column of immobilised ferron on alumina. The adsorbed analyte was then eluted with 5?mL of hydrochloric acid and was determined by flame atomic absorption spectrometery. The speciation of chromium was affected by first passing the solution through an acidic alumina column which retained Cr(VI) and then Cr(III) was preconcentrated by immobilised ferron column and determined by FAAS. The concentration of Cr(VI) was determined from the difference of concentration of total chromium and Cr(III). The effect of pH, concentration of eluent, flow rate of sample and eluent solution, and foreign ions on the sorption of chromium (III) by immobilised ferron column was investigated. Under the optimised conditions the calibration curve was linear over the range of 2–400?µg?L^?1 for 1000?mL preconcentration volume. The detection limit was 0.32?µg?L^?1, the preconcentration factor was 400, and the relative standard deviation (%RSD) was 1.9% (at 10?µg?L^?1; n?=?7). The method was successfully applied to the determination of chromium species in water samples and total chromium in standard alloys.     

Kinetics of autocatalytic acid hydrolysis of cellulose with crystalline and amorphous fractions

The acid hydrolysis of cellulose with crystalline and amorphous fractions is analyzed on the basis of autocatalytic model with a positive feedback of acid production from the degraded biopolymer. In the condition of low acid rate production compared with hydrolysis rate, both fraction of cellulose decrease exponentially with linear and cubic time dependence, and the normalized number of scissions per cellulose chain follows a sigmoid behavior with reaction time. The model predicts that self generated acidic compounds from cellulose accelerate the degradation of the biopolymer. However, if the acidic compounds produced are volatile species, then their release under low pressure will reduce the global rate of degradation of cellulose toward its intrinsic rate value determined by the residual acid catalyst present in the starting material.     

Interaction of carboxylated polyacrylamide with chromium(III) acetate: 13C NMR study of mechanism

The interaction of chromium(III) acetate with poly(acrylamide-co-acrylic acid) in aqueous medium leads to formation of three-dimensional network of crosslinked macromolecules. Formation of the complex between chromium(III) cation and carboxylate groups is a driving force of the interaction. Depending on the reagents ratio, the complex contains two or three carboxylate groups. The amide units are not involved in any specific interaction with the cation.     

Chromatography of inorganic ions on sulfoethyl cellulose layer in mixed sulfuric acid-organic solvent media

Summary The thin-layer chromatographic behavior of 49 inorganic ions has been systematically studied on layers of sulfoethyl (SE) cellulose, a strongly acidic cation-exchanger, with binary solvent mixtures consisting of sulfuric acid and an organic solvent such as methanol or acetone. The characteristic retention on the cellulose layer can be recognized for some ions forming sulfato complexes in the acid-organic solvent medium, and some aspects of the behavior are discussed. Chromatographic separations of analytical interest are also demonstrated on the SE-cellulose layer with acid-methanol and acid-acetone solutions used as mobile phases.     

Spectrophotometric determination of inorganic mercury (II) after preconcentration of its diphenylthiocarbazone complex on a cellulose column

A simple and a relatively green methodology have been developed for the preconcentration of mercury based on the adsorption of its diphenylthiocarbazone complex on a cellulose column. The effects of various parameters such as effect of acidity, eluting agents, stability of the column, sample volume, interfering ions, etc. have been studied in detail. The adsorbed complex could be easily desorbed using environmentally benign polyethylene glycol-400 and the concentration of mercury was determined using visible spectrophotometry. The calibration graph was linear in the range 0-2mugmL(-1) of mercury with a detection limit of 2mugL(-1) and the validity of the proposed method was checked by studying the recovery of mercury in spiked tap water, well water and sea water samples. The highest preconcentration factor achieved for quantitative recovery (>95%) of mercury (II) was 33 for a 500mL sample volume. The method was also applied to the analysis of mercury content in city waste incineration ash (CRM176). The relative standard deviation of the method was found to be 3.5%.     

酸性离子液体催化纤维素在生物丁醇中转化为乙酰丙酸丁酯

研究了几种磺酸功能化离子液体催化纤维素在生物丁醇中转化为乙酰丙酸丁酯的性能. 系统考察了催化剂的酸强度, 用量, 反应温度, 时间和溶剂对纤维素转化效率和产物分布规律的影响. 实验结果表明酸度最强的磺酸功能化离子液体1-(4-磺酸丁基)-3-甲基咪唑硫酸氢盐([C₄H₈SO₃Hmim]HSO₄)能够有效地催化纤维素转化为乙酰丙酸丁酯, 且在优化的反应条件下纤维素的转化率高达98.4%, 乙酰丙酸丁酯的产率为31.1%, 同时共生产物甲酸丁酯、水溶性产物和生物油的产率分别为33.4%、20.6%和23.8%. 该催化体系具有一定的耐水性能, 水的添加量为0.2 mL时并不会严重影响纤维素的转化率. 此外, 酸性离子液体催化剂还表现出了良好的重复使用性能, 使用六次后仍然保持较高的活性.     

Preconcentration of chromium(III) and speciation of chromium by electrothermal atomic absorption spectrometry using cellulose adsorbent

A simple and sensitive method has been developed for species selective determination of chromium(III) and chromium(VI) in water by electrothermal atomic absorption spectrometry. The procedure is based on selective absorption of Cr(III) on a cellulose micro column (pH 11, 0.5 mol L(-1) NaCl). Total chromium was subsequently determined after appropriate reduction of Cr(VI) to Cr(III). Recoveries of more than 97% were found. A concentration factor of 100 was achieved. The relative standard deviations (n=10) at the 40 ng L(-1) level for chromium(III) and chromium(VI) were 2.3% and 1.8% and corresponding limits of detection (based on 36) were 1.8 ng L(-1) and 5.1 ng L(-1), respectively. No interference effects have been observed from other investigated species and the method has been successfully applied to natural water samples.     

Enhanced bacterial cellulose production from <Emphasis Type="Italic">Gluconobacter xylinus</Emphasis> using super optimal broth

The bacterial cellulose (BC) produced by Gluconobacter xylinus due to its versatile properties, is used in healthcare and industrial applications. However, its use is restricted owing to the limited yield from the existing culture protocols. In the current study, BC production is studied in the presence of Super Optimal Broth with catabolite repression (SOC) medium which is used to revive Escherichia coli cells after electroporation or chemoporation. In SOC medium, Gluconobacter xylinus produces cellulose pellicles within 5 days of incubation with an enhanced conversion of the carbon source to cellulose compared to traditional Hestrin–Schramm (HS) medium. SOC medium also maintains the pH close to 7.0 in static cultures unlike in HS medium where the pH is acidic. The physico-chemical and morphological characteristics of the BC produced in SOC are determined using powder X-ray diffraction (pXRD), thermo gravimetric analysis (TGA), Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH), and scanning electron microscopy (SEM) analyses. Our results indicate that SOC enhance the yield of bacterial cellulose and allows conversion of 50% of the carbon source to bacterial cellulose, compared to only 7% conversion in the case of traditional HS medium after 7 days of interaction. We also observe an increase in hydration capacity of BC produced using SOC as compared to HS media.     

Enhancing adsorption of heavy metal ions onto biobased nanofibers from waste pulp residues for application in wastewater treatment

Biobased nanofibers are increasingly considered in purification technologies due to their high mechanical properties, high specific surface area, versatile surface chemistry and natural abundance. In this work, cellulose and chitin nanofibers functionalized with carboxylate entities have been prepared from pulp residue (i.e., a waste product from the pulp and paper production) and crab shells, respectively, by chemically modifying the initial raw materials with the 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) mediated oxidation reaction followed by mechanical disintegration. A thorough investigation has first been carried out in order to evaluate the copper(II) adsorption capacity of the oxidized nanofibers. UV spectrophotometry, X-ray photoelectron spectroscopy and wavelength dispersive X-rays analysis have been employed as characterization tools for this purpose. Pristine nanofibers presented a relatively low content of negative charges on their surface thus adsorbing a low amount of copper(II). The copper adsorption capacity of the nanofibers was enhanced due to the oxidation treatment since the carboxylate groups introduced on the nanofibers surface constituted negative sites for electrostatic attraction of copper ions (Cu²⁺). The increase in copper adsorption on the nanofibers correlated both with the pH and carboxylate content and reached maximum values of 135 and 55 mg g^?1 for highly oxidized cellulose and chitin nanofibers, respectively. Furthermore, the metal ions could be easily removed from the contaminated nanofibers through a washing procedure in acidic water. Finally, the adsorption capacity of oxidized cellulose nanofibers for other metal ions, such as nickel(II), chromium(III) and zinc(II), was also demonstrated. We conclude that TEMPO oxidized biobased nanofibers from waste resources represent an inexpensive and efficient alternative to classical sorbents for heavy metal ions removal from contaminated water.     

Complexes of chromium(III) with 2,3-dihydroxynaphthalene-6-sulfonic acid and 4,5-dihydroxynaphthalene-2,7-disulfonic acid in aqueous solution

The chromium(III) complex species formed, in acidic and basic solutions at 25.0+/-0.1 degrees C, between Cr(III) and 2,3-dihydroxynaphthalene-6-sulfonic acid (2,3-DHN-6-SA, H(2)L(2-)) and 4,5-dihydroxynaphthalene-2,7-disulfonic acid (4,5-DHN-2,7-DSA, H(2)L(-)) were determined. Over the acidic pH range, the coordination of 2,3-DHN-6-SA and 4,5-DHN-2,7-DSA to Cr(III) in 1 : 1 mole ratio occurs, and CrL and CrL(-) type complexes are formed. At near neutral pH, CrL(OH)(-) and CrL(OH)(2-) type hydroxo complexes are formed. The acid-dissociation constants of ligands and the formation constants of chromium(III) complexes were determined in 0.1 m KNO(3) ionic medium by potentiometric titration using the BEST computer program. Thus, the removing capacities of these ligands could be examined by calculating the equilibrium concentration of Cr(III) that exists in the discharge water of various industries since Cr(III) ions are the main pollutants present during waste water treatment in our city, Bursa.     

水溶液中制备分子印迹聚合物微球及其分子识别特性 研究

采用聚乙烯醇400作为分散剂,利用模板分子与功能单体/聚合物残基之间的离子键(静电)相互作用形成复合物,用水溶液微悬浮聚合法制备了4-氨基吡啶(4-AP)和甲氧苄氨嘧啶(TMP)分子印迹聚合物微球,并通过色谱行为表征,比较了它们对各自的模板分子作用的强弱。结果表明,采用甲基丙烯酸为功能单体制备的分子印迹聚合物微球(MIMs),对带有氨基的模板分子主要靠离子键(静电)相互作用,且作用力的大小与氨基的个数有关,色谱研究表明,模板分子中氨基数目越多,这种作用越强,而且这种作用不是简单的加合,而是协同增强作用。     

Production of bacterial cellulose from alternative low-cost substrates

Cellulose is the most widely used biopolymer on Earth. Its large-scale production is mainly from lignocellulosic material (plant origin), however, this plant material is not the only source of this valuable polymer, since microorganisms, like bacteria, naturally produce cellulose, especially those of the genus Komagateibacter (formerly Gluconacetobacter). This type of cellulose is of great interest because of its unique properties such as high purity and resistance, nevertheless, it has not been produced in a large-scale industrial process to date using low-cost substrates, one of the key aspects that should be considered for the industrial obtaining of any biotechnological product. As a main finding we found that the majority of low-cost culture media discussed could have the potential to produce bacterial cellulose on an industrial scale, since in most cases they yield more cellulose (with similar physical chemical characteristics) to those obtained in standard media. However, for an appropriate large-scale production, a specific knowledge about these by-products (since their composition and characteristics, which have a direct impact on the productivity of this biopolymer, are quite heterogeneous) and a proper standardization of them would also be required. Research staff of many industries could use the information presented here to help design a process to use their respective byproducts as substrate to obtain a product with a high added value as bacterial cellulose.     

厚朴酚键合硅胶液相色谱固定相的制备、表征与性能评价

通过γ-巯丙基三甲氧基硅烷(KH-590)的作用, 将具有抗菌功能的中草药厚朴的主要药用成分厚朴酚键合在硅胶表面上, 制备了厚朴酚键合硅胶液相色谱固定相. 采用红外光谱、元素分析和热重分析对该固定相进行了表征. 以苯同系物、5种吡啶、6种苯胺和8种芳香羧酸类化合物为溶质探针, 初步考察了该新型固定相的基本色谱性能, 研究了其对这些化合物的保留机理. 结果表明, 该固定相的反相色谱性能类似于十八烷基键合硅胶固定相(ODS), 分离原理与疏水性作用有关; 另外, 该固定相包含有别于疏水性作用的氢键作用、π-π电荷转移作用和偶极-偶极等作用, 多种作用力使其在分离某些可电离的碱性和酸性化合物时表现出更好的选择性和分离效果. 厚朴酚配体的多种作用位点对快速分离极性芳香化合物有重要贡献.     

Removal of cerium(III) species from solutions using granulated zeolites

The possibility of the use of granulated zeolites for the removal of cerium(III) species from solutions labelled with cerium-141 radioisotope, has been investigated. Measurements of cerium(III) species in solutions and of the distribution of cerium(III) species in column fillings (granulated zeolites), after passing the solution through columns filled with various granulated zeolites have shown that cerium(III) ions can be effectively removed from weakly acidic solutions using granulated mordenite. The influence of pH, of the concentration of cerium(III) ions in solution and of the flow rate of the solution through the column on the efficiency of cerium(III) species removal and on the distribution of cerium(III) species in the column has been investigated. The mechanism of exchange of cerium(III) ions from solution with sodium ions from granulated zeolites has been discussed.     

Analytical chemistry of chromium species in the environment, and interpretation of results

Valence-selective species determination of chromium in environmental and biological material presents intricacies primarily due to the complex nature of the samples and the instability of the oxidation states of chromium. In particular organic matter ubiquitously present in environmental samples introduces the risk of chromium(VI) reduction during analysis which takes place preferably in acidic solution. Also chromium(III) oxidation may occur in alkaline medium. Hence analytical methods should be adequately adapted to the reliable determination of chromium(VI) in blood, natural water, effluents, sediments and soil. It can be shown that polarography is most effectually suitable to the determination of chromium(VI) compounds. Chromium(VI) is electrochemically active over the entire pH range, so that medium pH can be selected for measuring, thus protecting samples most effectively from undergoing redox reactions during the analytical procedure. Other established methods such as spectrophotometry or valence-specific extraction are more crucial, because these generally require acidic medium. In some cases sample pre-treatment can be employed to eliminate reductants prior to final measurement. Very few methods are available to selectively measure chromium(III). Indirect determination is therefore preferred. Optimum conditions for the determination of total chromium by AAS are shortly outlined.     

Removal of gadolinium ions from solutions using granulated zeolites

The possiblity of the use of granulated zeolites for the removal of gadolinium ions from solutions has been investigated. Measurements of gadolinium ion concentrations in solutions and of the distribution of gadolinium ions in column filligns (granulated zeolites), after passing the solution through columns filled with various granulated zeolites (zeolite 4A, zeolite 13X and synthetic mordenite), have shown that gadolinium ions can be effectively removed from nearly neutral or acidic solutions using granulated mordenite. The influency of pH, column filling and the flow rate of the solution through the column on the efficiency of gadolinium ion removal and on the distribution of gadolinium ions in the columns has been investigated. On the basis of the results obtained, the conditions for the most efficient removal of gadolinium ions from solutions have been obtained.