Chelating ion-exchangers containing n-substituted hydroxylamine functional groups : Part II. N-acylphenylhydroxylamines

The problems associated with the conversion of commercial carboxylic acid ion exchangers to the acid chloride have been studied and a synthesis of a cross-linked poly(acryloyl chloride) is described. Reaction with phenylhydroxylamine produced a chelating ion exchanger, possessing acyl oxime functional groups, whose properties are compared with those of an aroyl oxime exchanger described earlier. Resin capacity from the acyl oxime group was 0.45 mmole g^-1, and the resin had a rapid equilibration rate. A column separation of mercury and lead is discussed.     

Chelating ion-exchangers containing n-substituted hydroxylamine functional groups : Part IV. Column separations on a hydroxamic acid resin

Ion exchange separations on a new hydroxamic acid ion exchanger are described. Quantitative separation of iron(III) from various salts and from several analytical standards has been achieved, and sources of interference in the colorimetric determination of iron with thioglycollic acid can be eliminated. Quantitative separations of copper from iron and from cobalt and nickel are possible. Recoveries and separations of iron and uranium from simulated sea-water samples are demonstrated.     

Chelating ion-exchangers containing N-substituted hydroxylamine functional groups: Part I. N-aroylphenylhydroxylamines

Chelating ion exchangers containing N-carbonylphenylhydroxylamine functional groups have been synthesized and their exchange behaviour with copper, cobalt, iron, vanadium and uranium investigated. Of the two polymers described, a linear oxime-carbonyl polymer exhibited chelating capacity as a function of pH analogous to the chelates formed by BPHA. An oxime-carbonyl polymer based on polyethyleneimine had high capacities for the metal ions studied, but the principal mode of reaction was by electron donation from nitrogen atoms. The absence of co-ion in metal ion capacity studies indicates the possibility of formation of 1:2 and 1:3 metal complexes with the resin. Separations of iron(II)-iron(III) and vanadium-iron appear possible.     

Chelating ion-exchangers containing n-substituted hydroxylamine functional groups: Part V. Iron,copper, and uranium separations on Duolite CS-346 resin

The separation of iron(III), copper(II) and uranyl(II) ions from a series of salt solutions by chelating ion exchange on Duolite CS-346 resin by pH control is described. Recoveries of these ions from cobalt and nickel salt solutions were quantitative. Iron may also be separated from copper by selective sorption with pH control, and uranium from iron and copper by selective desorption with sodium carbonate solution as eluent.     

Sorption of ethanesulfonic acid by nylon-6 containing various numbers of end groups

From the analysis of the permeation of ³⁵S labeled ethanesulfonic acid, through nylon-6 films sorption isotherms were obtained. The films are characterized by their largely different content of carboxyl and amino end groups. It was found that the shape of the isotherm depends on the molar ratio of the two end groups: an S-shape curve for the film containing the carboxyl end group larger than the amino end group and a Langmuir-type curve for the film containing comparable numbers of end groups. These results were explained by the McGregor-Harris theory in which the acid dissociation constants of the two end groups in nylon were estimated experimentally.     

Ion-exchange resins containing s-bonded dithizone and dehydrodithizone as functional groups : Part 2. Desoprtion properties and development of separation procedures for gold and platinum group metals

The desorption of precious metals from the PD and PTD ion-exchange resins, containing S-bonded dithizone and dehydrodithizone as functional groups, is described. Each sorbent was loaded batchwise with individual or combined metals and then treated with excess of various extracting agents (6 M hydrochloric acid, 2 M perchloric acid, ammonium nitrate, sodium thiocyanate, thiourea). Strong retention of some adsorbed metals and instability during the loading and elution stages were found with the PD resin, but a selective separation of palladium and gold from accompanying metals was possible. The PTD resin had superior properties. Unsual effects were detected when elution rates were compared for individual metals and mixtures. While Pd and Pt, loaded individually, were desorbed quantitatively by thiourea, co-extracted Ir(IV) completely inhibited their elution. The regeneration of PTD by special sequences of eluents was utilized for selective chromatographic separation of Pd, Pt, Os, Au and (with restrictions) Ir from each other and also from large amounts of base metals and salts.     

Sorption of silver,gold and palladium with a polythioether foam

Silver, gold and palladium can be sorbed by a thiopolymer of the type [HO(CH₂CH₂CH₂SS)_nCH₂CH₂OH]. The distribution coefficient for palladium increases with halide concentration, with iodide having the largest effect. Silver can be extracted from chloride, nitrate or picrate media. The different distribution coefficients for gold in hydrochloric acid and in sodium chloride suggest that different sorption mechanisms predominate.     

Ion-exchange resins containing S-bonded dithizone and dehydrodithizone as functional groups : Part 1. Preparation of the Resins and Investigation of the Sorption of Noble Metals and Base Metals

The one-step reaction of dehydrodithizone with chloromethylated polystyrene yields the anion-exchanger P-TD. Reduction of the immobilized tetrazolium groups of P-TD produces a chelating resin, P-D, containing S-bonded dithizone as the functional group. Distribution coefficients as a function of acidity are presented for 27 metal ions, to establish the selectivity of these sorbents for noble metals. For gold and platinum group metals, the ion-exchangers show marked differences in loading capacities, rates of simultaneous sorption in static conditions and efficiencies in column tests. The P-TD anion exchanger seems to be more profitable than the P-D chelating resin for most purposes.     

Sorption of silver and thallium salts by a polymer on dibenzo-18-crown-6

Complexes of 11 composition are formed by sorption of silver and thallium salts from solution by a polymer containing immobilized dibenzo-18-crown-6. The anions are not coordinated. The hydration energy of the anions determines their effect on the transfer coefficients of Ag and Tl from aqueous solutions into the sorbentcontaining crown.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 759–761, April, 1990.     

Synthesis and characterisation of novel functional polyolefin containing sulfonic acid groups

The strong polar group, sulfonic acid, has successfully been introduced into ethylene/allylbenzene copolymers without degradation or crosslinking via chlorosulfonation reaction with chlorosulfonic acid as a chlorosulfonating agent in 1,1,2,2-tetrachloroethane followed by hydrolysis. The degree of sulfonation (DS) can be easily controlled by changing the ratio of chlorosulfonic acid to the pendant phenyls of the copolymer. The microstructure of sulfonated copolymers were unambiguously revealed by ¹H NMR and ¹H-¹H COSY spectral analyses, which indicates that all the sulfonation reactions exclusively took place at the para-position of the aromatic rings. The thermal behaviors were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC data exhibit a systematic trend of melting temperature increasing with DS. TGA data of sulfonated copolymers show an increase in degradation temperature from 444 to 460 °C compared to the received copolymer. Sulfonated copolymers also show an additional minor loss of mass at approximately 261 °C, which is not observed in the received copolymer. The wetting properties of the sulfonated copolymers were also evaluated by contact angle measurement, and a notable increase in surface hydrophilicity was identified.     

Sorption characteristics and chromatographic separation of gold (I and III) from silver and base metal ions using polyurethane foams

The influence of different parameters on the sorption profiles of trace and ultra traces of gold (I) species from the aqueous cyanide media onto the solid sorbents ion exchange polyurethane foams (IEPUFs) and commercial unloaded polyurethane foams (PUFs) based polyether type has been investigated. The retention of gold (I) species onto the investigated solid sorbents followed a first-order rate equation with an overall rate constant k in the range 2.2-2.8 ± 0.2 s⁻¹. The sorption data of gold (I) followed Freundlich and Langmuir isotherm models. Thus, the a dual-mode of sorption mechanism involving absorption related to “weak base anion exchanger” and an added component for “surface adsorption” seems the most likely proposed dual mechanism for retention profile of gold (I) by the IEPUFs and PUFs solid sorbents. The capacity of the IEPUFs and PUFs towards gold (I) sorption calculated from the sorption isotherms was found to be 11.21 ± 1.8 and 5.29 ± 0.9 mg g⁻¹, respectively. The chromatographic separation of the spiked inorganic gold (I) from de ionized water at concentrations 5-15 μg mL⁻¹ onto the developed IEPUFs and PUFs packed columns at 10 mL min⁻¹ flow rate was successfully achieved. The retained gold (I) species were then recovered quantitatively from the IEPUFs (98.4 ± 2.4%, n = 5) and PUFs (95.4 ± 3.4%, n = 5) packed columns using perchloric acid (60 mL, 1.0 mol L⁻¹) as a proper eluating agent. Thiourea (1.0 mol L⁻¹)-H₂SO₄ (0.1 mol L⁻¹) system was also used as eluating agent for the recovery of gold (I) from IEPUFS (95.4 ± 5.4%, n = 3) and also PUFs (93.4 ± 4.4%, n = 3) packed columns. The performance of the IEPUFs and PUFs packed columns in terms of the height equivalent to the theoretical plates (HETP), number of plates (N), and critical and breakthrough capacities towards gold (I) species were evaluated. The developed IEPUFs packed column was applied successfully for complete retention and recovery (98.5 ± 2.7) of gold (III) species spiked onto tap- and industrial wastewater samples at <10 μg Au mL⁻¹ after reduction to gold (I). The IEPUFs packed column was applied satisfactorily for complete retention and recovery (98.5 ± 2.7) of total inorganic gold (I) and/or gold (III) species spiked to tap- and industrial wastewater samples at <10 μg mL⁻¹ gold. Chromatographic separation of gold (I) from silver (I) and base metal ions (Fe, Ni, Cu and Zn) using IEPUFS packed columns was satisfactorily achieved. The proposed method was applied successfully for the pre-concentration and separation from anodic slime and subsequent FAAS determination of analyte with satisfactory results (recoveries >95%, relative standard deviations <4.0%).     

Application of a macroporous resin containing imidazoline groups to preconcentration and separation of gold, platinum and palladium prior to ICP-AES determination

A new functional resin with a long functional side chain was synthesized by modification of aminated macroporous poly(vinyl chloride) resin with cyanoethylene and ethylenediamine. Traces of Au(III), Pt(IV) and Pd(II) in aqueous solution were quantitatively adsorbed in the acidity range of pH 4 and C(H(+)) 3 M. The rate of equilibration is high; Cu(2+), Fe(3+), Ni(2+), etc. exhibit little interference on the adsorption of the sought noble metals. The saturated adsorption capacities for Au(III), Pt(IV), Pd(II) and Ir(IV) in 2 M HCl were 4.0, 1.57, 2.26, 1.85 mmol g(-1). Adsorbed ions can be quantitatively desorbed by 4% thiourea +0.25 M H(2)SO(4). The resin has good reusability, and can be used for preconcentration and separation of Au(III), Pt(IV) and Pd(II) prior to their determination by ICP-AES with satisfactory results.     

Electro-chromatography in the separation of ions : Part III. Separation of silver group metals

The migration sequences of silver group ions Ag⁺, Hg₂⁺², Pb⁺²and Ti⁺ have been studied in a number of complex-forming electrolytes. Based on the migration sequences, the ions in a mixture can be separated into distinct zones using a decinormal solution of sodium chloride, potassium chloride or potassium cyanide as the electrolyte. The sequence is Hg — Ag— Pb—Ti, while in KCN at pH 7.0 the sequence becomes Ag—Hg—Pb—Ti.     

Pd(II)-catalyzed deprotection of acetals and ketals containing acid sensitive functional groups

The pincer complex [Pd(C¹,O¹,N¹-L)(NCMe)]ClO₄ (L = monoanionic ligand resulting from deprotonation of the acetyl group of the dimethyl monoketal of 2,6-diacetylpyridine) is used for the high-yield and selective catalytic hydrolysis of aliphatic, aromatic, cyclic, and acyclic dimethyl-acetals, -ketals, and dioxolanes, even in the presence of large substituents. Other protecting groups, such as THP or TBDMS, or very acid-sensitive alcohols were not affected. The catalyst is easily prepared in high yield from Pd(AcO)₂ and 2,6-diacetylpyridinium perchlorate stable to air and moisture, easily and fully recoverable and reusable.     

Kinetics and mechanisms of oxidation of organic compounds by silver(II) species. Part VI: Iminodiacetic acid and N-methyliminodiacetic acid

The kinetics and mechanism of oxidation of iminodiacetic acid and N-methyliminodiacetic acid by aquasilver(II) and Ag(II)-2,2′-bipyridine complexes has been investigated. The results are discussed with reference to the active reaction pathways, the equilibrium quotient of the title reactions, the protolytic equilibria which involve the oxidizing complex, and the intrinsic self-exchange rates of the oxidants.     

Ion-exchange resins containing s-bonded dithizone and dehydrodithizone as functional groups : Part 3. Determination of Gold,Platinum and Palladium in Geological Samples by means of a Dehydrodithizone Resin and Plasma Emission Spectrometry

A procedure is described for the determination of gold, platinum and palladium in sulphide ores, concentrates and mattes. The method is based on chromatographic separation and selective elution of precious metals on small resin beds (0.7 × 2.5 cm) of the sorbent P-TD. After roasting, the samples were digested with aqua regia, and the residues fused with sodium peroxide. The acid leaching solutions obtained from both procedures were separately passed through an ion-exchange column. The metals were quantitatively retained after one loading step and eluted by a sequence of 2 M perchloric acid and 5% (w/v) thiourea solution. Preconcentrated Au, Pt and Pd were finally quantified with a d.c. plasma emission spectrometer. The effect of roasting temperature on the recovery of precious metals as well as the efficiency of the aqua regia leaching from the different materials were investigated in detail. Repeated analyses of standard reference samples proved the proposed method to be reliable.     

Polymeric cation-exchange monolithic columns containing phosphoric acid functional groups for capillary liquid chromatography of peptides and proteins

Two different monoliths, both containing phosphoric acid functional groups and polyethylene glycol (PEG) functionalities were synthesized for cation-exchange chromatography of peptides and proteins. Phosphoric acid 2-hydroxyethyl methacrylate (PAHEMA) and bis[2-(methacryloyloxy)ethyl] phosphate (BMEP) were reacted with polyethylene glycol diacrylate (PEGDA) and polyethylene glycol acrylate (PEGA), respectively, in 75-μm i.d. UV-transparent fused-silica capillaries by photo-initiated polymerization. The hydrophobicities of the monoliths were evaluated using propyl paraben under reversed-phase conditions and synthetic peptides under ion-exchange conditions. The resulting monoliths exhibited lower hydrophobicities than strong cation-exchange monoliths previously reported using PEGDA as cross-linker. Dynamic binding capacities of 31.2 and 269 mg/mL were measured for the PAHEMA–PEGDA and BMEP–PEGA monoliths, respectively. Synthetic peptides were eluted from both monoliths in 15 min without addition of acetonitrile to the mobile phase. Peak capacities of 50 and 31 were measured for peptides and proteins, respectively, using a PAHEMA–PEGDA monolith. The BMEP–PEGA monolith showed negligible hydrophobicity. A peak capacity of 31 was measured for the BMEP–PEGA monolith when a 20-min salt gradient rate was used to separate proteins. The effects of functional group concentration, mobile phase pH, salt gradient rate, and hydrophobicity on the retention of analytes were investigated. Good run-to-run [relative standard deviation (RSD) < 1.99%] and column-to-column (RSD < 5.64) reproducibilities were achieved. The performance of the monoliths in ion-exchange separation of peptides and proteins was superior to other polymeric monolithic columns reported previously when organic solvents were not added to the mobile phase.     

Analytical applications of the determination of hexacyanoferrate(III) with ascorbic acid: Part IV. Determination of hydroxylamine

Hydroxylamine can be determined by reaction with an excess of standard potassium hexacyanoferrate(III) solution at pH 8–10. After 30 min the excess is titrated with ascorbic acid solution in the presence of 2,6-dichlorophenolindophenol indicator.