Application of a new nanoporous sorbent for extraction and pre-concentration of lead and copper ions

The authors describe a method for the trace determination of copper (II) and lead (II) in water and fish samples using solid-phase extraction via siliceous mesocellular foam functionalised by dithizone. Siliceous mesocellular was functionalised with dithizone, and the resulting sorbent was characterised by scanning electron microscopy, surface area analysis, thermogravimetric/differential thermal analysis and FTIR. Following solid-phase extraction of target ions by the sorbent, copper and lead ions were quantified by flame atomic absorption spectrometry. Factors affecting the sorption and desorption of target ions by the sorbent were evaluated and optimised. The calibration plot is linear in the 1 – 500 μg L^?1 copper (II) and 3–700 μg L^?1 lead (II) concentration range. The relative recovery efficiency in real sample analysis is in the range from 96 to 102%, and precision varies between 1.7 and 2.8%. It is should be noted that the limits of detection for the copper and lead analysis were 0.8 and 1.6 μg L^?1, respectively. Also, the adsorption capacities for copper and lead ions were 120 and 160 mg g^?1, respectively. The obtained pre-concentration factor for the lead and copper ions by the proposed solid-phase extraction was 75. The method was successfully applied to the determination of low levels of copper (II) and lead (II) in tap, Caspian sea, Persian gulf and lake water and also their detection in fish samples.     

Highly branched polyethylene used as sorbents for oil-spill cleanup and separation

Highly branched polyethylene (HBPE) was developed into practical application as highly efficient sorbent material for oil-spill cleanup and oil/water separation. To obtain large-scale production of HBPE, a thermal stable Ni(II)-α-diimine catalyst for ethylene polymerization in our previous work has been employed to prepare the polyolefin material in a 10-liter polymerization reactor with a high activity (>10⁶ g_PE/mol_[Ni] h). The structure, molecular weight and distribution, thermal and mechanical properties were systematically characterized by NMR, ATR-FTIR, GPC, DSC, DMA, and TGA, respectively. Through simple but feasible cross-linking process, the HBPE-based oil-absorption materials with contact angles up to 111.5° were directly applied into absorption test using various oil and pure hydrocarbons. Reusability and recovery of the absorption materials and oil or solvents were probed by drying or using the distillation method. Oil/water separation was made to determine the hydrophobic and oleophilic nature of this material. Flory-Rehner polymer swelling theory is employed to study the structure–property relationship via determining the network structure including cross-linking density ρ_c and average molecular weight M_c between two cross-links. The mixture of sorbent material after absorbing oil was regarded as crude oil component to simulate oil refinery process by thermogravimetric analysis, providing an alternative approach for oil-collection.     

Well-defined nanoporous palladium for electrochemical reductive dechlorination

Well-defined nanoporous palladium (np-Pd) fabricated by a modified electrochemical dealloying procedure is demonstrated to be an excellent electrocatalyst material for reductive degradation of both carbon tetrachloride and chlorobenzene.     

Sorption and diffusion of phenols onto well-defined ordered nanoporous monolithic silicas

The sorption of phenol, and o-, m-, and p-aminophenol (o-, m-, and p-AP) onto highly ordered mesoporous silicas (HOM) with cubic Im3m (HOM-1), hexagonal H(I) (HOM-2), 3-D hexagonal p6(3)/mmc (HOM-3), cubic Ia3d (HOM-5), lamellar L( infinity ) (HOM-6), and solid phase S (HOM-8) materials has been investigated kinetically. Nanostructured silica molecular sieves have been prepared at 25 and 60 degrees C with lyotropic liquid-crystalline phases of the nonionic surfactant (Brij 76) that was used as a structure-directing agent. Such nanostructured silicas have been studied by 29Si nuclear magnetic resonance (29Si NMR), powder X-ray diffraction (XRD), the Brunauer-Emmett-Teller (BET) method for nitrogen adsorption and surface area measurements, and transmission electron microscopy (TEM) techniques after synthesis and sorption. It was found that all materials exhibit well-defined long-range porous architectures without significant loss of the ordered texture during phenol sorption. The kinetics of phenol sorption has been studied spectrophotometrically at different temperatures (25-40 degrees C; +/-0.1 range). The sorption rate is zero order in all phenols sorbed, and increases directly in the pattern P >m-AP > o-AP > p-AP, which reflects the mobility of the phenol compounds on the particle pores. The isothermal sorption and the kinetic parameters were discussed and it was established that a diffusion-controlled process characterizes phenol sorption. Furthermore, the mechanism of phenol sorption was deduced to be predominantly particle diffusion. The diffusion coefficients were determined using Fick's equation. The trend of diffusion of all phenols onto nanoporous silica was HOM-8 > HOM-2 > HOM-6 > HOM-5 > HOM-1 > HOM-3, reflecting the effect of the uniform pore size distribution and the internal surface area of the nanostructured silicas on the diffusion process.     

Potentialities of silane-modified silicas to regulate palladium nanoparticles sizes

A promising approach to control palladium nanoparticle sizes by application of silane modified silicas was suggested. The combination of reductive properties of silicon hydride groups and hydrophobic properties of alkylsilyl groups which act as agglomeration limiters for metal nanoparticles gives an opportunity to synthesize uniformly distributed particles with a specified size. Silicas modified with triethoxysilane (TES) and diisopropylchlorosilane (DIPCS), as well as, the combination of hexamethyldisilazane (HMDS) and triethoxysilane were applied for formation of such bifunctional matrices. Properties of the silane-modified silica samples and changes occurred during the formation of palladium nanoparticles were studied by IR spectroscopy. Thermal stability of surface chemical compounds was investigated by thermogravimetric analysis (TGA); low-temperature nitrogen adsorption was used to study structural properties of the applied materials. With the use of transmission electron microscopy (TEM) the dependence of palladium nanoparticle size on the nature of support surface layer was found.     

Oximidobenzotetronic acid as a reagent for the separation and gravimetric determination of palladium and cobalt

Oximidobenzotetronic acid is recommended for the separation and gravimetric determination of palladium and cobalt An ethanolic solution of the reagent quantitatively precipitates palladium(II) from solutions which are 0.75 N in acid up to pH 5.1, the complex is weighed as Pd(C₉H₅NO₄)₂. Cobalt(II) can be determined in the filtrate after the precipitation of palladium. With 0.5 N acid solutions, no interference was found from Pt(IV), Ir(IV), Rh(III), Ru(III), Os(IV), Au(III), Ag(I), Cu(II), Fe(III), Ni(II), Hg(II). Pb(II), Bi(III), Cd(II), As(V), Se(VI), Te(IV), Mo(VI), Sb(III), Al(III), Cr(III), Zn(II), Ti(IV), Zr(IV). acetate, oxalate, citrate, tartrate, phosphate and fluoride.     

Sulfophenylanthranylic acid as a new reagent for palladium

The use of diphenyl reagents bearing electron-withdrawing substituents in catalymetric analysis was studied using sulfophenylanthranilic acid as an example. A selective catalytic effect of palladium(II) on the oxidation of sulfophenylanthranilic acid by cerium(IV) sulfate in a weakly acid solution was found. The reaction rate was studied as a function of component concentrations, solution acidity, and temperature. A procedure for determining palladium(II) was developed and tested using model mixtures and a KP-5 sample of complex composition.Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 2, 2005, pp. 144–148. Original Russian Text Copyright © 2005 by Burmistrova, Mushtakova, Nikonorov.     

Ion-exchange high-performance liquid chromatography of nucleotides and polypeptides on new types of ion-exchange sorbents, based on polystyrene-coated silicas.

A novel type of ion exchanger was prepared by multipoint covalent binding of polystyrene chains onto the surface of porous silica followed by polymer-analogous modification of the bonded layer. Both anion and cation exchangers were synthesized and examined in the separation of nucleotides and proteins. Rapid and efficient separation of basic polypeptides on strong anion exchangers and that of acidic polypeptides on strong cation exchangers could be achieved. For the separation of complete mixtures of polypeptides the application of zwitter-ionic ion exchangers can be recommended.     

A new solvent extraction scheme for the separation of platinum,palladium, rhodium and iridium

A new scheme is proposed for the separation of platinum, palladium, rhodium and iridium in hydrochloric acid solutions, by solvent extraction. Platinum and palladium are complexed with 2-mercaptobenzothiazole and potassium iodide and simultaneously extracted into chloroform, thus separating them from rhodium and iridium. Palladium is separated from platinum by extracting its dimethylglyoxime complex into chloroform, while rhodium is separated from iridium by extracting its 2-mercaptobenzothiazole complex into chloroform after reduction with tin(II) chloride.     

Dithione as chelator in the flow injection separation and pre-concentration system of trace metals in biological samples

Dithione was used as chelator in the flow injection-knotted reactor separation and pre-concentration system coupled to flame atomic absorption spectrometry to determine trace amounts of Cu, Cd, Zn, Co in biological standard samples. Peak height was used for quantitative purpose. Alkali and alkaline earth elements, which could not chelate with dithione were separated from the objective metals; competition between trace metals were avoided for the strong chelating ability of dithione. Compared to diethyldithiocarbamate and pyrrolidine dithiocarbamate (APDC), dithione was used for multi-element detection with lower chelator concentration and better analytical performance. Concentration factors of 23.4-69.3 were obtained using dithione, with the detection limits of 1.06-2.56 μg/l. The system developed was used to determine trace metals in certified biological reference materials of human hair, pig liver and sea prawn after routine digestion, the results obtained agreed well with the certified values, relative standard deviations of the determinations were at the range of 2.10-3.02%.     

Modified nanoporous silicas for oral delivery of the water insoluble organotin compound: loading and release of methylphenyltin dichloride as an anti-tumor drug model

Different nanoporous silica materials, MCM-41, MCM-48 and SBA-15, were modified by pyridine and their applications for oral drug delivery system were evaluated. These pyridine functionalized nanoporous silicas were loaded with a water insoluble diorganotin(IV) dichloride complex as an antitumor drug model and its release from them were investigated by changing pH. An efficient pH-responsive carrier system was constructed by coordination of the pyridine group in modified nonoporous materials to tin complex. In vitro, releasing of loaded tin complex was studied in three different kinds of fluids, including a simulated gastric medium and a simulated body fluid. The loading and releasing of the diorganotin(IV) dichloride from various modified nanoporous silicas and also a non-porous silica (SiO₂) were investigated, and the results were compared. In addition, the effect of some factors such as pH, time of loading and releasing were investigated through this study.     

纳米多孔钯催化亚胺化合物加氢还原反应研究

本文首次研究了以H2为氢源、纳米多孔钯催化亚胺化合物的加氢还原反应.结果表明:在氢气压力为101.325 kPa,溶剂为无水乙醇,反应温度为30℃,反应时间24 h,催化剂物质的量分数为5%的条件下,纳米多孔钯可以高效催化亚胺化合物的加氢还原反应,高选择性、高产率地生成一系列仲胺,仲胺的产率在93%~96%之间.该反应官能团兼容性好,底物范围广,带有甲基、甲氧基、氰基和羟基等基团的亚胺都可以顺利发生还原反应生成相应的仲胺.催化剂重复使用5次后,活性未出现明显降低.     

Application of carbon sorbents for the concentration and separation of metal ions.

Solid-phase extraction is an attractive approach in the preparation of many kinds of samples prior to analysis; highly selective sorbents are desirable for this purpose. The objective of this review is to provide updated information about carbon-based sorbents, their interaction modes and potential application for the concentration and separation of metal ions from environmental samples prior to their determination. New selective phases such as fullerenes and carbon nanotubes are described. Selected examples illustrate the potential of these sorbents.     

A new approach to separation and pre-concentration of some trace metals with co-precipitation method using a triazole

A new co-precipitation method was developed to separate and pre-concentrate Fe(3+), Cu(2+), Cr(3+), Zn(2+), and Pb(2+) ions using an organic co-precipitant, 3-benzyl-4-p-nitrobenzylidenamino-4,5-dihydro-1,2,4-triazole-5-on (BPNBAT) without adding any carrier element, following flame atomic absorption spectrometric (FAAS) determinations. Effect of some analytical conditions, such as pH of the solution, quantity of the co-precipitant, standing time, centrifugation rate and time, sample volume, and interference of concomitant ions were investigated over the recovery yields of the metal ions. The recoveries of the analyte ions were in the range of 95-102%. The detection limits, corresponding to three times the standard deviation of the blank, were found to be in the range of 0.3-2.0 microg L(-1). The precision of the method, evaluated as the relative standard deviation (R.S.D.) obtained after analyzing a series of 10 replicates, was between 1.6% and 6.0% for the trace metal ions. The method was validated by analyzing two certified reference materials and spiked addition. The proposed procedure was applied for the trace metal ions in some environmental samples.     

Retention of palladium and phosphine ligands using nanoporous polydicyclopentadiene thimbles

Thimbles composed of polydicyclopentadiene retained Pd and phosphines used in Buchwald-Hartwig and Sonogashira coupling reactions but allowed the products to permeate. The products were isolated in high yields on the exteriors of the thimbles with no detectable contamination from phosphine and with Pd loadings as low as < 5.5 ppm.     

Electrostatic interaction effect for human DNA separation with functionalized mesoporous silicas

This work describes the development of highly efficient human DNA separation with functionalized mesoporous silica (FMS) materials. To demonstrate the electrostatic interaction effect between the target DNA molecules and FMS, three aminofunctionality types comprised of a mono-, a di-, and a tri-amine functional group were introduced on the inner surfaces of mesoporous silica particles. Systematic characterization of the synthesized materials was achieved by solid-state ²⁹Si and ¹³C-NMR techniques, BET, FT-IR, and XPS. The DNA separation efficiency was explored via the function of the amino-group number, the amount used, and the added NaCl concentration. The DNA adsorption yields were high in terms of the use of triaminofunctionalized FMS at the 10 ng/L level, and the DNA desorption efficiency showed the optimum level at over 3.0 M NaCl concentration. The use of FMS in a DNA separation process provides numerous advantages over the conventional silica-based process.     

Prochlorperazine bismethanesulfonate as a new reagent for the spectrophotometric determination of palladium

A simple, rapid, and selective method for the determination of palladium is described. The orange-red palladium(II)-prochlorperazine bismethanesulfonate complex in the presence of hydrochloric acid-sodium acetate buffer exhibits maximum absorbance at 480 nm with a molar absorptivity of 4.32 × 10³ liters mol^?1 cm^?1. The sensitivity of the reaction is 24.62 ng cm^?2. The system obeys Beer's law over the concentration range 0.4–20 ppm of palladium with an optimum concentration range of 1–19 ppm. The apparent stability constant of the complex is found to be log K = 5.3 ± 0.1 at 27 °C. The effects of pH, time, temperature, order of addition of reactants, reagent concentration, and interferences from various ions are reported. The proposed method offers the opportunity to carry out the determination at room temperature without the need for an extraction step. The method is also found to be suitable for the determination of palladium in jewelry alloy.