Dorota Jermakowicz-Bartkowiak

Gold sorption on weak base anion exchangers with aminoguanidyl groups

Abstract Two resins with different matrices, both bearing aminoguanidyl ligands, were obtained and used for gold sorption from hydrochloric acidic and from alkali solutions. Resin 1 was a aminoguanidine derivative of poly(acrylonitril-co-vinyl acetat-co-divinyl benzene) terpolymer (AN/VA/DVB), (67:27:10 wt.%), and Resin 2 the same derivative of gel expanded poly(vinylbenzyl chloride-co-divinylbenzene) copolymer (VBC/DVB). The resins sorption capacity and sorption isotherms of both resins were determined for AuCl 4 − and Au(CN) 2 − anions. Resin 2 revealed the best sorption of gold from acidic and alkali solutions: 68 and 23 mg/g, respectively. The effect of the HCl concentration on AuCl 4 − removal from solution was investigated. Gold was recovered quantitatively from both resins using a 5% thiourea solution in 0.1 HCl. Both resins remained ability of multiple gold sorption and desorption under acidic conditions.

Anion exchangers with alkyl substituted guanidyl groups ☆: Gold sorption and Cu(II) coordination

Abstract Two methods of introducing guanidyl groups into polymer matrix were investigated in this work: the reaction of cyanamide (alkyl substituted cyanamides) and carbodiimides with amino groups in modified polystyrene. The new anion exchangers (AEG) with alkyl substituted guanidyl groups contain 1.5–2.3 mmol/g of ligands and exhibit high selectivity towards Au(CN) 2 − anions. From the solution containing 2 ppm of gold the sorption is as high as 30 mg/g. Furthermore, AEG reveal high affinity towards tetrachloroaurate anions. The log K in diluted solution is about 5. The values of gold sorption as dicyanoaurate or tetrachloroaurate anions on AEG with alkyl substituted hydrogen atoms in guanidyl groups is two–four times higher than sorption on anion exchangers synthesized previously by exchange of chlorine with guanidine or aminoguanidine. The EPR studies of Cu(II)-loaded AEG were undertaken to correlate the structural properties of the formed complexes with the nature of the ligands, the ligand concentration, water regain of the resins and pH.

Sorption of aurocyanide and tetrachloroaurate onto resin with guanidine ligand—an XPS approach

The guanidine ligand attached to vinylbenzyl chloride matrix as well as its sorption ability to tetrachloroaurate and dicyanoaurate ions were investigated upon using X-ray photoelectron spectroscopy. The form of metallic gold, Au(0), was not observed on gold loaded resin surface when solutions of tetrachloroaurate or potassium dicyanoaurate were used. Complete elution of gold was achieved for both regeneration media: thiourea solution and mixture of sodium hydroxide and benzoate. The results demonstrate that XPS can also be a powerful technique for the analysis of the oxidation state of sorbed metal and can be a suitable method for the confirmation of functional groups incorporated in the polymer.

Influence of the structure of chelating resins with guanidyl groups on gold sorption

Abstract The chemical composition and structure of copolymers determines modification degree, concentration of ligands, their accessibility and hence capacity and selectivity of chelating resins. In order to investigate all such influences, a new series of copolymers have been obtained: one with increased polarity and hydrophilicity of polymer surface has been synthesized from vinyl benzyl chloride (VBC), methyl methacrylate (MM) and divinylbenzene (DVB) mixture, another one with toluene and hexadecane as inert diluents. As was expected copolymers synthesized in the presence of hexadecane, which is thermodynamically poor for the mixture of monomers, are porous with small pores (less than 1.8 nm radius) and with macropores (radius bigger than 17 nm). After modification with aminoguanidine bicarbonate, resins with the ligand concentration in the range 1–2 mmol/g are more hydrophilic but porosity decreases due to the elasticity of networks. The copolymers and resins obtained in the presence of toluene have a gel expanded structure. The ability of resins to remove dicyanoaurate complexes has been tested under the following conditions: an excess of potassium cyanide, 50 mg/l of dicyanoaurate concentration and ratio of aminoguanidine ligands to gold complexes 7.7:1. Under these conditions the sorption for the concentration of ligands of 1.2 mmol/g was about 23 mg/g and for 2.0 mmol/g it was 30 mg/g. Sorption of gold increases with increased ligand content. Sorption of gold at pH 7 is higher than at pH 9.5 and at 13.5 comparable to that at pH 9.5. Lowering dicyanoaurate concentration to 5 mg/l decreases the sorption of gold, but when the ligand to dicyanoaurate anions ratio is 1.1:1 the sorption reaches 30 mg of gold/g, which corresponds to a distribution coefficient of 6900. However, better sorption at low ligand to dicyanoaurate ratio is accompanied by much lower extraction degree and distribution coefficient.

Synthesis and some sorption properties of anion exchangers bearing ligands of different length with guanidyl and biguanidyl end groups

In this work the influence of ligands length with guanidyl and biguanidyl end groups on the performance of anion exchangers is presented. These anion exchangers are synthesized in a two-step reaction. Firstly, the aminolysis of chlorine in a copolymer of vinylbenzyl chloride (VBC) and 2 wt% of divinylbenzene (DVB) with hexamethylenediamine (HMDA) or diethylenetriamine (DETA) is conducted. Thus obtained amine derivatives are subsequently reacted with cyanamide, carbodiimide or sodium dicyanamide. It is found that the most convenient method of biguanidine group introduction into polymer matrix is the reaction of amino groups with sodium dicyanamide. Properties of resins are studied using Cu(II) ions as a spin probe detected by EPR method. A higher complexing ability towards Cu(II) showed by anion exchangers with DETA ligands (DETA resins) is due to chelating function of their ligands. The anion exchanger with HMDA ligands (HMDA resins) requires higher pH (about 7) to provide sufficient number of deprotonated nitrogen donors of monodentate ligands for sorption of Cu(II). The ligands length and their hydrophilicity do not change significantly sorption properties of resins towards dicyanoaurate and tetrachloroaurate.

Metal ion uptake by ion-exchange/chelating resins modified with cyclohexene oxide and cyclohexene sulphide

Abstract A ring opening reaction with either cyclohexene oxide or cyclohexene sulphide has been used in the modification of two types of polymeric resins. Both resins contained amino groups, one being obtained by reacting the vinylbenzyl chloride/divinylbenzene (VBC/DVB) copolymer with ethylenediamine, the second by reacting the VBC/DVB copolymer with diethyl malonate followed by aminolysis with ethylenediamine. Modification resulted in a set of novel chelating resins, which has been characterised and used in metal ion uptake experiments. These resins are highly selective towards copper(II) in acetate buffered solutions. The selectivity of the modified resins decreases in the order, Cu(II)>Cd(II)>Zn(II)>Ni(II), which is different from the Irving–Williams series. The highest affinity towards Cu(II) ions has been found for the resin modified with cyclohexene oxide, for which log K d was 4.91 at pH 5.6.

Piperazine Functionalized Resins for Au(III), Pt(IV), and Pd(II) Sorption

The result of synthesis of anion exchangers bearing piperazine functionalities is presented in this paper. A series of new ion exchange resins was synthesized by modification of VBC/DVB copolymer with 1(2-aminoethyl)piperazine (resin 1P), 1-amino-4-methylpiperazine (resin 2P), and 1-methylpiperazine (resin 3P). Adsorption studies of gold, platinum, and palladium were conducted with batch and dynamic method from multicomponent solutions containing AuCl4−, PtCl62−, and PdCl42− in the concentration range 10 mg/dm3 to 919 mg/dm3. The resins revealed excellent sorption ability towards these metals. The greatest total sorption capacities were determined as 331 mg/g Au for 2P resin, 405 mg/g Pt for 3P resin, and 150 mg/g Pd for 1P resin. The examined 3P resin showed the best total sorption capacity 796 mg/g. Affinity studies were also conducted. The examined resin 1P revealed the greatest affinity to platinum and palladium (lgK 4.5-5) whereas resin 2P revealed the best affinity to gold where lgK were ca. 4.9.

GOLD RECOVERY FROM GUANIDINE RESINS

This article describes some studies of dicyanoaurate anion elution from vinylbenzyl chloride resins containing guanidine ligands. The elution of gold (I) cyanide anions from loaded guanidine resin (resin with guanidine ligands) using sodium hydroxide eluent and modified caustic eluent: mixture of sodium hydroxide and sodium benzoate were studied. Full elution of gold cyanide using dynamic method of elution was achieved.

Synthesis and characterization of resins with ligands containing guanidinine derivatives. Cu(II) sorption and coordination properties

A new modification direction of acrylonitrile, vinyl acetate and divinylbenzene terpolymers (A, B) are presented. The aminolysis of nitrile groups of the terpolymers using ethylenediamine or hydroxylamine hydrochloride was a first stage of the modification. The resulting amine groups reacted with dicyandiamide (DCDA), cyanamide (CA) and sodium dicyanimide (SDC) in order to obtain the biguanidyl, guanidyl or nitrilguanidyl derivatives in the polymer side chain, respectively. The properties of all obtained resin such as water regain, nitrogen content, amine and carboxyl group concentration and sorption properties towards Cu(II) from nitric acid solutions were determined. The studies of IR spectra of all the resins were performed. Structures of ligand complexes with Cu(II) were studied using electron paramagnetic resonance spectroscopy.

Synthesis and some sorption properties of the anion-exchangers with biguanidyl groups

Abstract In this work, a method of synthesis of the resins bearing biguanidyl groups is presented. It includes exchange of chlorine in the terpolymer of styrene–vinylbenzyl chloride and 2 wt.% of divinylbenzene for ethylenediamine and the reaction of the amino groups with sodium dicyanamide. Thus obtained groups were converted to biguanidyl ones with urotropine. Resins are displaying sufficiently high biguanidyl ligand content, 1.7 mmol/g. The presence of guanidyl and biguanidyl groups does not improve sorption of Cu(II), which is due only to the nitrogens originating in ethylenediamine, as indicated by the electron paramagnetic resonance (EPR) spectra. Obtained resins have negligible sorption of Ni(II) and Co(II) but they have high capacity towards dicyanoaurate anions and gold chlorocomplexes. The sorption of gold from diluted 2 ppm solution of dicyanoaurate reaches 19 mg of Au/g of dry resin.