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.     

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.     

Chelating ion-exchangers containing n-substituted hydroxylamine functional groups: Part 6. Sorption and separation of gold and silver by a polyhydroxamic acid

The sorption and desorption characteristics of gold and silver on a polyhydroxamic acid chelating resin are described. Gold is quantitatively sorbed from 0.5 M nitric acid or neutral solutions, and readily eluted with 0.5% ($\text{w}\text{v}$) potassium cyanide solution. Silver is removed from 0.05 M nitric acid or neutral solutions, and can be eluted with the cyanide solution or with 0.5 M nitric acid. Gold can be quantitatively separated from copper, iron and silver; gold and silver are sorbed from dilute cyanide solutions. Tests with river water and other eluting systems are reported.     

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 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.     

Preparation and properties of macroreticular resins containing thiazole and thiazoline groups

Three macroreticular polystyrene-based resins with amino- or imino-thiazole and thiazoline groups as the functional groups have been prepared. The resins are highly stable in acid and alkaline solutions and have high selectivity for mercury(II). In the presence of hydrochloric acid, sorption of mercury attains equilibrium fairly rapidly, the time for 50% uptake of mercury being 3-6 min. There are practically no interferences. In a column operation, mercury is quantitatively recovered by elution with 0.1M hydrochloric acid containing 5% thiourea. The thiazoline resin column can be used to concentrate mercury from sea-water.     

Modification of epoxy-novolac resins with polysiloxane containing nitrile functional groups: synthesis and characterization

Synthesis of the statistical epoxidized polycyanopropylmethylsiloxane-co-polydimethylsiloxanes (PCPMS-co-PDMS) has been demonstrated. The modified polysiloxanes were prepared via a two-step method; (1) the ring-opening polymerization of octamethylcyclotetrasiloxane (D₄) and tetramethylcyclotetrasiloxane (D₄H), (2) hydrosilylation reaction of the polysiloxane prepolymers with allyl cyanide and allyl glycidyl ether. Molar ratios of D₄H and D₄ were varied to produce the modified polysiloxanes with differences in polarity. ¹H-NMR, ²⁹Si-NMR, ¹³C-NMR and FTIR were used to monitor the formation of the modified polysiloxanes and DSC was used to study their thermal behaviors (T_g, −118 to −68 °C). The use of the modified polysiloxanes as an elastomeric component in epoxy-novolac networks was also investigated. TEM and their transition temperatures suggested that the epoxy-novolac networks with high content of PDMS modifiers exhibited microphase separation. The fracture toughness properties of the networks with the polysiloxane modifiers were improved over the controls without polysiloxanes.     

Extraction of 1:1 electrolytes from aqueous solutions by resins containing dibenzo-18-crown-6 as anchor groups

The electrolyte concentration dependence of the distribution ratio of 1:1 electrolytes between resins containing dibenzo-18-crown-6 and water at 298 K was studied. The apparent equilibrium constants for the process taking place when the resin is equilibrated with aqueous solutions of different electrolytes are reported. The results obtained clearly reflect the influence of the anion on the extraction of cations by the resin containing the macrocyclic ligand.     

Ion-exchange foam chromatography: Part I. Preparation of rigid and flexible ion-exchange foams

In order to be able to apply the principles of foam chromatography to ion-exchange processes, preparative methods for open-cell ion-exchange foams, were investigated. Homogeneous ion-exchange foams were prepared by introducing ion-exchange groups on previously prepared phenol-formaldehyde, polyurethane and polyethylene foams. The maximum capacity of the produced sulfonated phenol-formaldehyde cation-exchange foams was 1.85 meq g^-1; that of the styrene-polyurethane interpolymer anion-exchange foams was 2.2 meq g^-1. Weak carboxylic ion-exchange foams were prepared by radiation grafting of polyurethane and polyethylene foams; the maximum capacity of these foams was 4.02 meq g^-1. Heterogeneous ion-exchange foams were prepared by foaming a fine powder of a commercially available cation exchanger with the precursors of open-cell polyether-type polyurethane foam. The capacity of such a foam containing 26% ion-exchange powder was 1.0 meq g^-1. The kinetics of the cation-exchange process on the heterogeneous foams was measured with ⁸⁵Sr.     

Ion-exchange resins in non-aqueous solvents-I Sorption rates of p-nitroaniline and the effects of small amounts of water

The rates of sorption of p-nitroaniline onto three hydrogenform resins in methanol, ethanol, n-propanol, isopropanol, n-butanol, acetonitrile, benzene, acetic acid and dioxan are reported. Two of the resins are typical gel-type, microreticular, sulphonated resins and the third is a new, highly porous and rigid, macroreticular, sulphonated resin, Amberlyst 15. There appears to be a correlation between viscosity or dielectric constant and the time for maximum sorption or maximum distribution coefficient when the alcohols are used, but no correlation for all the solvents is apparent. The macroreticular resin still functions when dry, even in the presence of non-polar solvents, but the microreticular resin does not. Small amounts of water present in the solvent or resin aid the sorption of the amine onto both types of resin. The effect of mesh size and cross-linkage are examined.     

Preparation and characterization of macroporous polystyrene resins containing ethynyl groups and transition metal acetylide complexes

Ethynylated polystyrene resins were prepared as functionalized polymer supports by the iodination reaction of macroporous polystyrene resins and reacted with transition metal diethynyl complex (Mt = Ni) and metal halides (Mt = Rh, Pd, and Pt) in a basic solvent using cuprous iodide as a catalyst to obtain macroporous polystyrene resins containing organotransition metals. The distribution of the metal acetylide complexes in the modified macroporous resins was determined by an electron probe microanalyzer. A gradient in the transition metal distribution was observed in any case of the modified resins. The stability of the organotransition metal complexes in the polymer matrix could be compared with a low molecular weight analogous complex quantitatively.     

Studies with dithizone: Part 35. A new look at the structure of dithizone in solution

The traditional view that solutions of dithizone in organic solvents comprise equilibrium mixtures of thione- and thiol-forms which are individually responsible for the characteristic strong absorption bands around 620 and 440 nm is examined critically. It is shown that experimental values of pH_{$\text{1}\text{2}$}, pK and R (the peak ratio) can legitimately be used in calculations although they are compounded of parameters (partition coefficients, acid dissociation constants, etc.) relating to both of the alleged tautomeric forms and the equilibrium constant, K_T governing the interconversion. Published attempts to calculate K_T from spectral data alone are shown to be unreliable.     

Aromatic polyethers,polysulfones, and polyketones as laminating resins. V. Polymers containing acetylenic side groups

1,3-Bis(p-phenoxybenzenesulfonyl)benzene and 4,4′-diphenoxydiphenyl sulfone were polymerized with isophthaloyl and terephthaloyl chloride in Friedel-Crafts type polymerizations. These polymers had 2,4-diphenoxyacetophenone in the backbone. The acetyl group was then converted into an acetylene group. They were crosslinked effectively by cyclization of the acetylene groups with a catalyst or by cyclo-addition with bisnitrile oxides.     

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.     

Preparation and properties of a new chelating resin containing 1-nitroso-2-naphthol as the functional group

A macroreticular polystyrene-based chelating ion-exchanger containing 1-nitroso-2-naphthol as the functional group has been synthesized. The exchange-capacity of the resin for a number of metal ions such as copper(II), iron(III), cobalt(II), nickel(II), palladium(II) and uranium(VI) as a function of pH has been determined. The sorption and elution characteristics for palladium(II) and uranium(VI) have been thoroughly examined with a view to utilizing the resin for separation and concentration of uranium and palladium. Uranium(VI) has been separated from a mixture of ten other metal ions by sorption on the chelating resin and selective elution with 0.5M sodium carbonate. Palladium(II) has been separated from various metal ions by selective sorption on the resin in 1M hydrochloric acid medium.     

Investigations on the redox character of dithizone by voltammetric methods: Part II. The elucidation of the deterioration of dithizone solutions

The electrochemical redox behaviour of dithizone and its oxidation products have been examined in detail and the mechanisms of the electrochemical and aerial oxidation of dithizone are considered. All the oxidation products (tetrazolium and disulphide compounds) can be followed by voltammetric methods. The results of the electrochemical investigation of dithizone are useful for practical analytical and electroanalytical applications of dithizone.     

Investigations on the redox character of dithizone by voltammetric methods : Part I.The reduction of dithizone in aqueous solutions

The mechanism of the electrochemical reduction of dithizone to the corresponding hydrazo compound, diphenylthiocarbazide, has been examined in detail by polarographic and voltammetric techniques over a wide pH range. The reaction is reversible and dithizone can be determined polarographically in the range 10^-3–10^-5M. This polarographic behaviour suggests new applications of dithizone as an electroanalytical reagent.     

基于离子交换树脂制备多孔氧化铝球及在非水体系中分离银杏内酯

以磺酸型大孔离子交换树脂D072为模板, 设计合成了球形的多孔氧化铝, 利用XRD、SEM和氮气吸附仪对其结构进行了表征. 以这种球形多孔氧化铝作为分离材料, 考察了其在非水体系中对银杏黄酮和银杏内酯的吸附选择性, 在最佳分离条件下, 制备了纯度为58.5%, 且不含任何黄酮的银杏内酯. 利用红外光谱法证明了吸附机理为配位吸附.     

Preparation of macroreticular redox resins with hydroquinone and catechol units as pendant groups and their properties

Macroreticular redox resins with hydroquinone and catechol units as pendant groups were prepared by the Friedel-Crafts reaction of macroreticular styrene/divinylbenzene copolymer with 2,5- and 3,4-dimethoxybenzyl chlorides, followed by removal of the methyl groups with hydrobromic acid. The redox capacity of the macroreticular resins was determined by oxidation of hydrazobenzene with resins in oxidized form. Resins with 1,4-benzoquinone units were capable of oxidizing hydrazobenzene, whereas those with 1,2-benzoquinone (catechol quinone) units exhibited no apparent oxidative ability; this seems to be due to a complex formation between azobenzene and the catechol units in the reduced resins. Adsorption of metallic ions onto catechol-containing resins showed a high selectivity for Hg²⁺ ion. The effects of pH, reaction time, and ion concentration on the adsorption were also studied.