Simultaneous metal adsorption on tannin resins

Vegetable tannin sorbent is evaluated as ion exchange resin using a multitracer study on the adsorption behavior of various elements. Lisiloma latisiliqua L. tannins, polycondensated into spherical pellets were chosen as sorbent resin material. Sorption evaluation of Ce, Cu(II), U(VI), Eu, Fe(III), Th, Nd as representatives of different classes of metal ions were done at different pH values. The distribution ratio of the studied elements was calculated from laboratory experiments. Tannic ion exchange material shows excellent ability for actinides and rare earth elements adsorption from waters. Using radiotracers, the number of catechins subunits involve in each tannin-metal complex was determined.     

胶原纤维固化黑荆树单宁吸附V(V)的研究

研究了胶原纤维固化黑荆树单宁对V(V)的吸附。采用不同温度、pH值等条件进行吸附研究,并进一步探讨了固化黑荆树单宁的吸附动力学和吸附柱动力学及其吸附机理。结果表明,该材料对V(V)的吸附平衡符合Freund lich方程,温度对吸附平衡的影响不明显;吸附动力学可用拟二级速度方程来描述,该材料同时具有良好的柱动力学特性;V(V)的吸附过程可能存在三个反应,即V(V)与吸附剂之间发生氧化还原反应生成V(IV),V(IV)和-COOH之间发生离子交换反应,以及V(IV)与单宁的邻位羟基发生螯合。     

Recovery of Th(IV) from aqueous solution by reassembled collagen-tannin fiber adsorbent

A novel adsorbent, collagen immobilized tannin adsorbent (CITA), was prepared and its adsorption behaviors to Th(IV) were investigated. CITA was in fibrous state due to the reassembly of collagen molecules by the inducement of tannin. This adsorbent loaded a greater amount of tannin and exhibited higher adsorption capacity to Th(IV) than the tannin immobilized adsorbent prepared from collagen fiber. The adsorption of CITA to Th(IV) is mainly attributed to surface complexation, which is a pH- rather than an ionic strength-dependent process. The adsorption kinetics and isotherms were described by pseudo-second-order rate model and Freundlich equation, respectively. Column adsorption studies indicated that CITA is available for effectively recovering Th(IV) from aqueous solution.     

Selective preconcentration of trace thorium from aqueous solutions with Th(IV)-imprinted polymers prepared by a surface-grafted technique

A novel ion-imprinted adsorbent for selective solid phase extraction of thorium(IV) based on the surface of silica gel was prepared by a surface-grafted technique with methacrylic acid (MAA) as a functional monomer. After removal of Th(IV) ions with 3?mol?L^?1 HCl solution, the obtained imprinted particles for Th(IV) exhibited specific recognition and relatively rapid kinetic process. The maximum static and total dynamic adsorption capacity of the ion-imprinted polymers (IIPs) for Th(IV) was 33.2 and 17.3?mg?g^?1, respectively. A comparison of the selectivity coefficient of the imprinted polymers with that of non-imprinted polymers showed that the imprinted matrix for Th(IV)/U(VI), Th(IV)/Ce(III), Th(IV)/La(III) and Th(IV)/Zr(IV) was 58.8, 107, 106.4 and 151.7 times greater than non-imprinted matrix, respectively. With a series of samples loading flow rate of 3?mL?min^?1 for preconcentration, an enrichment factor of 14.6 and the detection limit of 0.59?µg?L^?1 were obtained. The relative standard deviation of the method under optimum conditions was 2.1% (n?=?7). The developed method was successfully applied to the determination of trace Th(IV) in real water samples with satisfactory results.     

Poly(hydroxyethyl methacrylate) membranes: as a hydrogel support for use in immobilized metal affinity chromatography

Lysozyme adsorption onto a dye ligand (Procion Red HE-3B) immobilized and Cu(II) incorporated poly(2-hydroxyethylmethacrylate) (pHEMA) membrane, were investigated. The membranes were prepared by UV initiated photopolymerization of HEMA in the presence of an initiator (α-α′-azoisobutyronitrile; AIBN). The amount of immobilized dye on the membrane was 112.2 μmol g⁻¹. Lysozyme adsorption on to these membranes from aqueous solutions containing different amounts of lysozyme at different pH was investigated in batch system. Lysozyme adsorption capacity of the dye-ligand immobilized membrane was 45.6 mg g⁻¹. Lysozyme adsorption capacity of the Cu(II) incorporated membranes (112.3 mg g⁻¹) was greater than that of the Procion Red HE-3B immobilized membranes. The non-specific adsorption of lysozyme on the pHEMA membranes was 0.14 mg g⁻¹. More than 97% of the adsorbed lysozyme were desorbed in 60 in the desorption medium containing 1.0 M KSCN at pH 8.0.     

Preparation of immobilized tannins for protein adsorption

Preparation and adsorption specificity of tannins immobilized by covalent binding on water-insoluble matrices were investigated. Immobilized tannins were prepared by condensing cyanogen bromide activated tannins with aminohexyl derivatives of several kinds of matrices. The most suitable matrix for the immobilization of tannin was alkali-treated cellulose powder. The concentration of sodium hydroxide solution for alkali treatment influenced the adsorption capacity of immobilized tannin for a protein, but temperature and time for alkali treatment did not. Immobilized tannins having spacers of long chain length exhibited high adsorption capacity for a protein. Chinese gallotannin was the most favorable ligand for protein adsorption. The immobilization of tannin on aminohexyl matrices was also possible by using epichlorohydrin instead of cyanogen bromide. The maximum adsorption capacity of the immobilized tannin for a protein was about 50 mg/ml of the absorbent. Immobilized tannin adsorbed proteins specifically but did not absorb low molecular weight compounds.     

Removal of Th(IV), Ni(II)and Fe(II) from aqueous solutions by a novel PAN–TiO<Subscript>2</Subscript> nanofiber adsorbent modified with aminopropyltriethoxysilane

A novel polyacrylonitrile (PAN)–titanium oxide (TiO₂) nanofiber adsorbent functionalized with aminopropyltriethoxysilane (APTES) was fabricated by electrospinning. The adsorbent was characterized by SEM, FTIR, TEG and BET analyses. The pore diameter and surface area of the adsorbent were 3.1 nm and 10.8 m² g^?1, respectively. The effects of several variables, such as TiO₂ and amine contents, pH, interaction time, initial concentration of metal ions, ionic strength and temperature, were studied in batch experiments. The kinetic data were analyzed by pseudo-first-order, pseudo-second-order and double-exponential models. Two isotherm models, namely Freundlich and Langmuir, were used for analysis of equilibrium data. The maximum adsorption capacities of Th(IV), Ni(II) and Fe(II) by Langmuir isotherm were found to be 250, 147 and 80 mg g^?1 at 45 °C with pH of 5, 6 and 5, respectively, and greater adsorption of Th(IV) could be justified with the concept of covalent index and free energy of hydration. Calculation of ΔG°, ΔH° and ΔS° demonstrated that the nature of the Th(IV), Ni(II) and Fe(II) metal ions adsorption onto the PAN–TiO₂–APTES nanofiber was endothermic and favorable at a higher temperature. The negative values of ΔG° for Th(IV) showed that the adsorption process was spontaneous, but these values for Ni(II)and Fe(II) were positive and so the adsorption process was unspontaneous. Increasing of ionic strength improved the adsorption of Ni(II) and Fe(II) on nanofiber adsorbent but decreased the adsorption capacity of Th(IV). The adsorption capacity was reduced slightly after six cycles of adsorption–desorption, so the nanofiber adsorbent could be used on an industrial scale. The inhibitory effect of Ni(II) and Fe(II) on the adsorption of Th(IV) was increased with an increase in the concentration of inhibitor metal ions.     

Adsorption syntax of Au(III) on unloaded polyurethane foam

The nature of adsorption behavior of Au(III) on polyurethane (PUR) foam was studied in 0.2M HCl aqueous solution. The effect of shaking time and amount of adsorbent were optimized for 3.16·10⁻⁵M solution of Au(III) in 0.2M HCl. The classical Freundlich and Langmuir adsorption isotherms have been employed successfully. The Freundlich parameters 1/n and adsorption capacityK are 0.488±0.016 and (1.40±0.22)·10⁻² mol·g⁻¹, respectively. The Langmuir constants of saturation capacityM and binding energyb are (1.66±0.08)·10⁻⁴mol·g⁻¹ and 40294±2947 l·g⁻¹, respectively, indicating the monolayer chemical sorption. The mean free energy (E) of adsorption of Au(III) on PUR foam has been evaluated using D-R isotherm and found to be 11.5±0.16 kJ·mol⁻¹ reflecting the ion exchange type of chemical adsorption. The effect of temperature on the adsorption has also been studied. the isosteric heat of adsorption was found to be 44.03±1.66 kJ·mol⁻¹. The thermodynamic parameters of ΔG, ΔH, ΔS and equilibrium constantK _c have been calculated. The negative values of ΔG, ΔH and ΔS support that the adsorption of Au(III) on PUR foam is spontaneous, exothermic and of ion exchange chemisorption. The nature of the Au(III) species sorbed on PUR foam have been discussed.     

Study on adsorption of Th(IV) using surface modified dibenzoylmethane molecular imprinted polymer

The adsorption of Th(IV) was studied using a novel dibenzoylmethane molecular imprinted polymers, which was prepared using acryloyl-β-cyclodextrin as a monomer on surface modified functional silica gel. X-ray photoelectron spectroscopy and FTIR were employed to confirm the reliability of the synthetic polymer. Scanning electron microscope was used to analyze the surface properties of the experimental materials. UV-spectrophotometer was employed to investigate the adsorption property and the concentration of Th(IV). Adsorption kinetics and adsorption isotherm were carried out. In pH 3.5, the adsorption equilibrium could reach a balance in 45 min, the resultant adsorbing capacity was 30.8 mg g^?1, and the remove ratio of Th(IV) was 88.1 %.     

Effect from Mechanical Stirring Time and Speed on Adsorption Performance of ZIF‐90 for n‐Hexane

Zeolite imidazolate frameworks (ZIFs) represent a class of metal‐organic frameworks (MOFs) for various potential applications due to their outstanding properties. However, to date, the creation of nanoframes with tunable structure faces a challenge. Herein, we develop a facile and efficient physical method that allows the preparation of ZIF‐90 with controllable surface area. In this study, the effect of various stirring time and speed in the acceleration of the precursor dissolution are revealed. The study shows that a moderate stirring speed (640 r · min^–1) and reaction time (6 h) are the optimal conditions to synthesize ZIF‐90 with a high adsorption capacity. More importantly, the maximum adsorption amount of n‐hexane is up to 211 mg · g^–1 by using this as‐prepared sample, which increases by 60 % in comparison with that of the minimum from other sample (133 mg · g^–1).     

Adsorptive removal of thorium from aqueous solution using diglycolamide functionalized multi-walled carbon nanotubes

Multi-walled carbon nanotubes (MWCNTs) were functionalized with diglycolamide (DGA) through chemical covalent route. The adsorption behavior of the DGA-functionalized-MWCNTs (DGA-MWCNTs) towards thorium from aqueous solution was studied under varying operating conditions of pH, concentration of thorium, DGA-MWCNTs dosages, contact time, and temperature. The effective range of pH for the removal of Th(IV) is 3.0–4.0. Kinetic data followed a pseudo-second-order model. The equilibrium data were correlated with the Langmuir, Freundlich, Dubinin-Radushkevich and Temkin models. The equilibrium data are best fitted with Langmuir model. The equilibrium Th(IV) sorption capacity was estimated to be 10.58 mg g^?1 at 298 K. The standard enthalpy, entropy, and free energy of adsorption of the thorium with DGA-MWCNTs were calculated to be 8.952 kJ mol^?1, 0.093 kJ mol^?1 K^?1 and -18.521 kJ mol^?1 respectively at 298 K. The determined value of sticking probability (0.072) and observed kinetic and isotherm models reveal the chemical adsorption of thorium on DGA-MWCNTs.     

Vanillin-condensed tannin study using flow injection spectrophotometry

Studies involving the kinetic reaction between vanillin and condensed tannins were developed using a flow injection system with spectrophotometric determination. A solution of the monomeric compound (-)-epicatechin was used as the analytical standard. This compound was chosen due to its structure, which is similar to a polymeric unit of the condensed tannin present in plants. The results indicated that the vanillin-condensed tannin reaction is time dependent and affected by the degree of polymerization of the condensed tannin. The flow system allowed (-)-epicatechin to be used without overestimating the content of the tannin present in the forage legume, guandu (Cajanus cajan (L.) Millsp.), studied. A relative standard deviation (R.S.D.) of <1% was found for a 4 h period work and allowed the determination of about 60 samples h(-1) with a detection limit of 1.05 mg l(-1) for condensed tannin. When compared to the manual vanillin procedure, the proposed approach can be used with various advantages.     

Archaeometric investigations on naturally and thermally-aged iron-gall inks using different tannin sources

This paper investigates the behavior of paper strips containing iron-gall inks prepared with tannins from different sources, subjected to natural and thermally-induced aging. Results indicate that inks containing initial concentrations of ferrous sulphate ranging from 0.2 to 10.0 g are amenable to treatment with calcium phytate, and thata good correlation exists between the recovery of excess iron and the initial concentration. Infrared spectra showed an absorption band at 1,750 cm^?1, typical of esther, solely in the samples prepared with a condensed tannin. The condensed nature of this tannin produced a different oxidation pattern, with iron removal inferior to those observed from inks produced with hydrolisable tannins. When tannic acid was used ferrous iron removals ranged from 0.050 to 1.800 g, decreasing to 0.5 g in the presence of copper; the same behavior was observed for the remaining hydrolisable tannins, with a lower recovery from the condensed tannin. The adopted natural aging procedure released a higher amount of ferrous iron compared to ASTM thermal aging. This was probably due to the marked effect of humidity, not considered in the thermal procedure. A series of archaeometric possibilities were used to help elucidate the degradation of cellulose strips impregnated with iron-gall inks.      

Recovery of Uranium(VI) from Sulfate Leach Liquor using Modified Duolite

Silicate mercapto Duolite composite ( SMDC ) and activated Duolite A 101 D ( AD ) were prepared, characterized, and tested for uranium removal from sulfate solution using batch experiment technique. The capability of newly adsorbents for sorption of uranium was estimated and optimized under different controlling variables, including the impact of uranium initial concentration, pH of the medium, equilibrium time, temperatures, dose and interfering ions. Testing of different adsorbents for adsorption isotherms revealed that the achieved experimental data were fitting well with the Langmuir isotherm model with 68.02 mg · g^–1 and 208.33 mg · g^–1 as theoretical capacity for AD and SMDC , respectively. Thermodynamic parameters have been resulted in negative values for ΔH and ΔS indicating an exothermic and decreased randomness behavior for uranium(VI) adsorption, while negative values of ΔG indicate spontaneous uranium adsorption. The kinetics studies showed that the adsorption process was controlled expressed by pseudo-second order model. Finally, the optimized factors have been applied for uranium(VI) recovery from Gattar leach liquor producing a uranium concentrate (Na₂U₂O₇) with uranium concentration of 70 % and purity of 93.33 %.     

A Novel Affinity Support Material for the Separation of Immunoglobulin G from Human Plasma

2‐Methacrylamidohistidine (MAH) as a pseudospecific ligand was synthesized from methacryl chloride and histidine. Spherical beads with an average size of 50–63 μm were obtained by the radical suspension polymerization of MAH and 2‐hydroxyethyl methacrylate (HEMA) conducted in an aqueous dispersion medium. Owing to the reasonably rough character of the bead surface, P(HEMA‐co‐MAH) beads had a specific surface area of 17.6 m²·g^–1. Synthesized MAH was characterized by NMR. P(HEMA‐co‐MAH) beads were characterized by swelling studies, FT‐IR spectroscopy, scanning electron microscopy (SEM) and elemental analysis. P(HEMA‐co‐MAH) affinity beads with a swelling ratio of 65% were used in the separation of human immunoglobulin G (HIgG) from aqueous solutions and human plasma. The maximum HIgG adsorption on the P(HEMA‐co‐MAH) adsorbents was observed at pH 7.4 for phosphate and at pH 6.0 for morpholinoethanesulfonic acid buffers. The HIgG adsorption onto the PHEMA adsorbents was negligible. Higher adsorption values (up to 46.5 mg·g^–1) were obtained when the P(HEMA‐co‐MAH) adsorbents were used in aqueous solutions. Much higher amounts of HIgG were adsorbed from human plasma (up to 73.8 mg·g^–1). Adsorption capacities of other blood proteins were obtained as 3.2 mg·g^–1 for fibrinogen and 4.6 mg·g^–1 for albumin. The total protein adsorption was determined to be 82.2 mg·g^–1. The pseudospecific affinity beads allowed one‐step separation of HIgG from human plasma. HIgG molecules could be repeatedly adsorbed and desorbed with these adsorbents without noticeable loss in their HIgG adsorption capacity.     

有序介孔碳的简易模板法制备与电化学电容性能研究

0引言电化学电容器(Electrochemical Capacitors),又称为超级电容器(supercapacitors)是介于传统电容器和二次电池之间的一种新型储能装置,它具有循环寿命长、比容量高、能快速充放电等优点[1,2]。近年来随着电子、电气设备的日趋小型化以及电动汽车工业的不断发展,作为后备电源和记忆候补装置的超级电容器日益引起了人们的广泛关注。碳材料由于具有成本低、比表面积大、导电性优良、制备电极工艺简单等特点,一直是超级电容器电极材料的首选。其中,活性炭是最早采用的多孔电极材料,其比表面积可高达2500￣3000m·2g-1[3]。然而,活性炭材料…     

化学-微波法制备高膨胀率膨胀蛭石及对亚甲基蓝的吸附机理

基于工业蛭石优异的热膨胀性及阳离子交换性,利用化学-微波法制备高膨胀率膨胀蛭石(HEV),采用对比分析法对亚甲基蓝(MB)的吸附性能进行了研究。结果表明,HEV膨胀率高(膨胀率K=60倍),比表面积大(80 m^2·g^-1),孔径主要分布在2~5 nm之间,仍保持蛭石、水金云母和金云母的物相结构,阳离子交换容量由原样的0.835 mmol·g^-1增加到1.005 mmol·g^-1。HEV对MB的吸附容量受MB初始浓度、吸附时间、溶液pH和吸附温度影响。当MB溶液初始浓度为300 mg·L-1、吸附时间为240 min、溶液pH值为9、吸附温度为298 K时,吸附量为419.87 mg·g^-1,远高于蛭石原矿。吸附过程符合Langmuir模型与准二级动力学模型,为单分子层吸附和吸附势垒较低的自发无序吸热反应过程。HEV具有优异的阳离子交换性和吸附性,是一种具有开发价值的高效低成本吸附剂。     

Improving the efficiency in the detection of gamma activities in environmental soil samples: influence of the granulometry and soil density

Ti(OH)₄ and TiCl₄ modified bentonite (Ti–Na-bent) were applied in the removal of Th(IV) from aqueous solution. Effect of different factors such as pH, contact time, temperature, initial concentration of Th(IV) and efficiency of them for thorium adsorption are investigated. Ti–Na-bent showed high adsorption capacity (q_m?=?231.37 mg/g) and quick adsorption kinetics at lower pH. The adsorption mechanisms involved are: (1) Th⁴⁺, [Th(OH)_4?n]ⁿ⁺ complexed on the outer-sphere of Na-bent and Ti–Na-bent. (2) Ion exchange between Th⁴⁺, [Th(OH)_4?n]ⁿ⁺ and exchangeable cations of Na-bent and the H on the hydroxyl group of Ti(OH)₄. Ti–Na-bent manifested high adsorption capacity for Th(IV), good acid resistance and long-term adsorption stability.

     

Competitive adsorption of uranium(VI) and thorium(IV) ions from aqueous solution using triphosphate-crosslinked magnetic chitosan resins

The triphosphate-crosslinked magnetic chitosan resins (TPP-MCR) with a diameter range of 200–350 nm were synthesized for the adsorption of U(VI) and Th(IV) ions from aqueous solutions. The adsorption experiments were conducted in both mono-component systems with pure actinide solution and bi-component systems with different U/Th mass ratios. The maximum adsorption capacities in mono-component systems determined by Langmuir model were 169.5 and 146.8 mg g^?1 for U(VI) and Th(IV), respectively. In bi-component systems, U(VI) and Th(IV) adsorption capacities were reduced significantly, and the combined sorption capacities were substantially lower (almost halved) compared to those obtained by the addition of sorption capacities using mono-component solutions, indicating that U(VI) and Th(IV) compete for the same sorption sites. Adsorption–desorption experiments for five cycles illustrated the feasibility of the repeated use of TPP-MCR for the adsorption of U(VI) and Th(IV) ions.     

A new sensitive and selective sensor for heavy metal ions based on tannin extracted from the skin of Punica granatum L

This article presents the development of a sensor made from a gold electrode and a receiving polymeric membrane based on tannin extracted from the skin of Punica granatum. L (pomegranate) for real-time detection of heavy metals in a hydrous environment. The basic principle of this device is the complexing (chelating) of metal ions through the adjacent hydroxyl groups contained in the chemical structures of the tannins. The electrochemical characterisation was performed by using electrochemical impedance spectroscopy and square wave voltammetry. Other morphological and structural analyses were performed by using Fourier transform infrared spectroscopy and atomic-force microscopy. The results obtained showed the high sensitivity of the developed device (detection limits of 6.35 × 10^?9 g L^?1 for Cu²⁺, 1.1 × 10^?8 g L^?1 for Cd²⁺ and 2 × 10^?7 g L^?1 for Pb²⁺) and the possibility of simultaneously detecting several heavy metals, each one in a highly selective manner with highly acceptable response time (48s).