The Development of Palladium(II)-Specific Amine-Functionalized Silica-Based Microparticles: Adsorption and Column Separation Studies

The adsorption and separation of platinum(IV) and palladium(II) chlorido species ([PtCl₆]^2? and [PdCl₄]^2?) on silica-based microparticles functionalized with ammonium centers based on ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetriamine (TETA) and tris-(2-aminoethyl)amine (TAEA) were investigated. The functionalized sorbent materials were characterized using SEM, XPS, BET, and FTIR. The sorbents were used in the batch and column study for adsorption and selective separation of [PtCl₆^2? and PdCl₄]^2?. The adsorption model for both [PtCl₆]^2? and [PdCl₄]^2? on the different sorbent materials fitted the Freundlich isotherm with R² values > 0.99. The S-TETA sorbent material was palladium(II) specific. Pd(II) loaded on the silica column was recovered using 3% m/v thiourea solution as the eluting agent. Separation of platinum and palladium was achieved by selective stripping of [PtCl₆]^2? with 0.5 M of NaClO₄ in 1.0 M HCl while Pd(II) was eluted with 0.5 M thiourea in 1.0 M HCl. The separation of palladium (Pd) from a mixture containing platinum (Pt), iridium (Ir), and rhodium (Rh) was successful on silica functionalized with triethylenetriamine (TETA) showing specificity for palladium(II) and a loading capacity of 0.27 mg/g. S-TETA showed potential for use in the recovery of palladium from platinum group metals such as from solutions of worn out automobile emission control catalytic convertors and other secondary sources.     

EXTRACTION OF PALLADIUM(II) AND PLATINUM(IV) AS CHLOROCOMPLEX ACIDS INTO BASIC ORGANIC SOLVENTS

Solvent extraction of platinum(IV) and palladium(II) with tri-n-octylamine(TOA) in o-xylene from 4.0M (Na,H)(Cl, HSO₄) has been investigated at 298K in order to compare with similar extraction by trioctylphosphine oxide(TOPO). The dependence of the distribution ratio of platinum(IV) and pal 1adium(II) on TOA, hydrogen ion and chloride ion concentrations suggests the dominant extracted species of these metals would be 2:1 for proto-nated amine : chlorocomplex anion and the extraction should be essentially anion exchange reaction. The extraction constants (Kex = D[H⁺(T0A)C1 ] ²[C1 ]²), were evaluated as 10^6-3 and 10^5.8 for platinum(IV) and pal ladium(II), respectively. The anion exchange with protonated TOPO salt represented by H(T0P0)₂ ⁺C1  is less than that with protonated TOA salt by a factor of one order.     

EQUILIBRIUM OF PALLADIUM(II) EXTRACTION WITH 1-OCTYLTHEOBROMINE

ABSTRACT

1-Octyltheobromine was synthesized to study extraction equiliburium of palladium(II). To evaluate its efficiency as an extractant, the extraction of palladium(II) from acidic chloride media was studied at 303K using toluene. The extraction of palladium(II) from hydrochloric acid media by 1-octyltheobromine exhibited high selectivity for palladium(II) over the platinum group metals. The stoichiometrics of the extraction of palladium(II) with 1-octyltheobromine was elucidated by examining the effects of hydrochloric acid, chloride ion, hydrogen ion, extractant and metal ion concentrations on its extractability. Palladium(II) was found to be extracted as two molecules of 1-octyltheobromine reacted with PdCl₂ as follows: PdCl₂ +{2}¯RN ? ¯PdCl₂(RN)₂. The extraction equilibrium constant was K=2.72?×?10⁸(mol?dm^?3)^?2. The complex of 1-octyltheobromine with PdCl₂ was confirmed by mass spectrometric analysis. The stripping of palladium(II) was performed over 60% by a single batchwise treatment with an aqueous solution of thiourea or ammonia.     

PERMEATION OF METAL IONS THROUGH HOLLOW-FIBER SUPPORTED LIQUID MEMBRANES: CONCENTRATION EQUATIONS FOR ONCE-THROUGH AND RECYCLING MODULE ARRANGEMENTS∗

ABSTRACT

p-(l,l,3,3-Tetramethylbutyl)phenyl hydrogen[N,N-di(2-ethylhexyl)amino-methylphosphonate was synthesized as a novel type of extractant to investigate the extraction behavior of base metals as well as of precious metals from aqueous chloride media into toluene. This reagent exhibited high selectivity for platinum (IV) and palladium (II) ions in the low acidic region (0·01 - 6?mol dm^?3) / over base metal ions except for trivalent iron over the whole concentration region under the present experimental conditions. The extraction of platinum and palladium with p-( 1,1,3,3-tetramethylbutyl)phenyl hydrogen[N,N-di(2-ethylhexyl)aminomethyl-phosphonate was higher than that with N,N-di(2-ethylhexyl)aminomethyl-phosphonic acid due to its high lipophilicity. Stripping of the loaded palladium was achieved with an aqueous mixture of I mol dm^?3 thiourea in combination with I mol dm^?3 hydrochloric acid. The extraction reaction of palladium from aqueous chloride media into toluene was found by slope analysis to be described as follows     

Fatty Imidazolines: A Novel Extractant for the Recovery of Palladium(II) from Hydrochloric Acid Solutions

The extraction of palladium(II) from hydrochloric acid solutions with a novel highly basic extractant, a mixture of homologous 1-[2-(alkanoylamino)ethyl]-2-alkyl-2-imidazolines (AAI) in toluene with 15% (v/v) of n-octanol was studied. Palladium(II) is rapidly and most effectively extracted with AAI hydrochloride at the low hydrochloric acid (chloride ions) concentration (up to 1 M) and can be completely separated from Fe(III), Cu(II), and Co(II). The palladium(II) extraction at the optimum acidity occurs via an anion-exchange mechanism with the formation of ionic associates (LH)₂PdCl₄ (K _ex = (1.5 ± 0.2) · 10⁴ at 0.5 M HCl) and is accompanied by the dimerization of palladium(II) in the organic phase with the formation of ionic associates (LH)₂Pd₂Cl₆ (K _dim = (3.9 ± 0.4) · 10^?4 at 0.5 M HCl). The anion-exchange extraction of palladium(II) at the acidity of 0.5 M HCl is temperature independent in the range 20–49°C. Complete stripping of palladium(II) can be performed using a 5% solution of thiourea in 0.1 M HCl.     

Adsorption of Some Platinum Group Metals on Some Complexane Types of Chemically Modified Chitosan

Abstract

A few kinds of complexane types of chemically modified chitosan, i.e., monocarboxymethylated chitosan (MCM-chitosan) and IDA- and DTPA-types of chitosan (IDA- and DTPA-chitosan) were synthesized to examine the adsorption of palladium(II), platinum(IV), and iridium(III) from hydrochloric acid solution as well as the elution of palladium and platinum and compared with those by crosslinked copper(II)-complexed chitosan (crosslinked chitosan). The adsorption of palladium(II) monotonously decreased with increasing hydrochloric acid concentration with all kinds of adsorbents. The adsorption of platinum(IV) also decreased with increasing hydrochloric acid concentration with all kinds of adsorbents except for DTPA-chitosan, with which it decreased in the low concentration region and increased in the high concentration region. The adsorption of iridium(III) also decreased with increasing concentration of hydrochloric acid with all kinds of adsorbents except for IDA-chitosan, but that on DTPA-chitosan was much smaller than other adsorbents. The adsorption on IDA-chitosan increased with increasing hydrochloric acid concentration in its low concentration region, and decreased in the high concentration region, different from other adsorbents. The magnitude of adsorption capacity of each adsorbent for palladium(II) was in the order MCM-chitosan = IDA-chitosan > DTPA-chitosan > crosslinked chitosan, while that for platinum(IV) was in the order, DTPA-chitosan > MCM-chitosan = IDA-chitosan > crosslinked chitosan. The elution of loaded palladium(II) and platinum(IV) with hydrochloric acid solution was much improved by chemical modification, especially that of platinum(IV) which was drastically improved by using IDA- and MCM-chitosan.     

Preparation of Some Eco-friendly Corrosion Inhibitors Having Antibacterial Activity from Sea Food Waste

Chitosan is one of the important biopolymers and it is extracted from exoskeletons of crustaceans in sea food waste. It is a suitable eco-friendly carbon steel corrosion inhibitor in acid media; the deacetylation degree of prepared chitosan is more than 85.16 %, and the molecular weight average is 109 kDa. Chitosan was modified to 2-N,N-diethylbenzene ammonium chloride N-oxoethyl chitosan (compound I), and 12-ammonium chloride N-oxododecan chitosan (compound II) as soluble water derivatives. The corrosion inhibition efficiency for carbon steel of compound (I) in 1 M HCl at varying temperature is higher than for chitosan and compound (II). However, the antibacterial activity of chitosan for Enterococcus faecalis, Escherichia coli, Staphylococcus aureus, and Candida albicans is higher than for its derivatives, and the minimum inhibition concentration and minimum bacterial concentration of chitosan and its derivatives were carried out with the same strain.     

Construction and Performance Characteristics of Modified Screen Printed and Modified Carbon Paste Sensors for Selective Determination of Cu(II) Ion in Different Polluted Water Samples

Four new ion-selective electrodes (ISEs), based on N,N′-bis(salicylaldehyde)-p-phenylene diamine (SPD) as ionophore, are constructed for the determination of copper(II) ion. The modified carbon paste (MCPEs; electrodes I and II) and modified screen-printed sensors (MSPEs; electrodes III and IV) exhibit good potentiometric response for Cu(II) over a wide concentration range of 1.0 × 10^?6 – 1.0 × 10^?2 mol L^?1 for electrodes (I and II) and 4.8 × 10^?7–1.0 × 10^?2 mol L^?1 for electrodes (III and IV) with a detection limit of 1.0 × 10^?6 mol L^?1 for electrodes (I and II) and 4.8 × 10^?7 mol L^?1 for electrodes (III and IV), respectively. The slopes of the calibration graphs are 29.62 ± 0.9 and 30.12 ± 0.7 mV decade^?1 for electrode (I) (tricresylphosphate (TCP) plasticizer) and electrode (II) (o-nitrophenyloctylether o-NPOE plasticizer), respectively. Also, the MSPEs showed good potentiometric slopes of 29.91 ± 0.5 and 30.70 ± 0.3 mV decade^?1 for electrode (III) (TCP plasticizer) and electrode (IV) (o-NPOE plasticizer), respectively. The electrodes showed stable and reproducible potentials over a period of 60, 88, 120, and 145 days at the pH range from 3 to 7 for electrodes (II), (III), and (IV) and pH range from 3 to 6 for electrode (I). This method was successfully applied for potentiometric determination of Cu(II) in tap water, river, and formation water samples in addition to pharmaceutical preparation. The results obtained agree with those obtained with the atomic absorption spectrometry (AAS).     

Highly Efficient Extraction of Rhodium(III) from Hydrochloric Acid Solution with Amide-Containing Tertiary Amine Compounds

Extraction of Rh(III) from a HCl solution with N,N-disubstituted amide–containing tertiary amine (ACTA) compounds (N,N-di-n-hexyl(N-methyl-N-n-octyl-ethylamide)amine (MonoAA), N-n-hexyl-bis(N-methyl-N-n-octyl-ethylamide)amine (BisAA), and tris(N-methyl-N-n-octyl-ethylamide)amine (TrisAA)) was investigated. The ACTAs extract Rh(III) more efficiently than tri-n-octylamine (TOA), and the extraction efficiency increases with increasing number of amide groups: TrisAA > BisAA > MonoAA ? TOA. For all ACTAs, the predominant Rh(III) complex extracted from 2 M HCl is probably {[RhCl₅(H₂O)]·(ACTA·H)₂}. The apparent basicity of the ACTAs and TOA varies in the opposite order from that observed for the Rh(III) extraction efficiency. Rh(III) can be readily back-extracted using 10 M HCl solution possessing a high selectivity over similarly loaded Pd(II) and Pt(IV).     

Cyclic Sorption and Desorption of Cu(II) onto Coconut Shell and Iron Oxide Coated Sand

Sorption is a viable treatment technology for copper-rich gold mine tailings wastewater. For continuous application, the sorbent should be regenerated with an appropriate desorbent, and reused. In this study, the sequential sorption/desorption characteristics of Cu(II) on coconut shell (CS) and iron oxide coated sand (IOCS) were determined. In batch assays, CS was found to have a Cu(II) uptake capacity of 0.46 mg g^?1 and yielded a 93% removal efficiency, while the IOCS had a Cu(II) uptake capacity and removal efficiency of 0.49 mg g^?1 and 98%, respectively. Desorption experiments indicated that HCl (0.05 M) was an efficient desorbent for the recovery of Cu(II) from CS, with an average desorption efficiency of 96% (sustained for eight sorption and desorption cycles). HCl (0.05 M) did not diminish the CS's ability to sorb copper even after eight sorption/desorption cycles, but completely deteriorated the iron oxide structure of the IOCS within six cycles. This study showed that CS and IOCS are both good sorbents for Cu(II); but cyclical sorption/desorption using 0.05 M HCl is only feasible with CS.     

Studies on the synthesis and properties of hydroxyl azacrown ether‐grafted chitosan

The chitosan hydroxyl azacrown ether was synthesized by reaction of hydroxyl azacrown ether with epoxy‐activated chitosan. The C₂ amino group in chitosan was protected from the reaction between benzaldehyde and chitosan to form N‐benzylidene chitosan. After reaction with epichlorohydrin and azacrown ether, reacting O‐aryl mesocyclic diamine‐N‐benzylidene chitosan and dilute ethanol hydrochloride solution to obtain novel chitosan‐azacrown ether bearing hydroxyl removed the Schiff base. Its structure was confirmed with elemental analysis, FTIR spectra analysis, X‐ray diffraction analysis, and solid‐state ¹³C NMR analysis. Its static adsorption properties for Ag(I), Cd(II), Pb(II), and Cr(III) were also investigated. The experimental results showed that the hydroxyl azacrown ether grafted chitosan has good adsorption capacity and high selectivity for Ag(I) in the coexistence of Pb(II) and Cd(II), the selectivity coefficients of hydroxyl azacrown ether chitosan were K_Ag(I)/Pb(II) = 32.34; K_Ag(I)/Cd(II) = 56.12. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1838–1843, 2001     

NEW XANTHIC ACID DERIVATIVES AS POTENTIAL REAGENTS IN THE SOLVENT EXTRACTION OF PRECIOUS METAL IONS: EXTRACTION OF PALLADIUM(II) WITH 13-BIS(0-BUTYLXANTHATO)PROPANE

ABSTRACT

Two series of new xanthic acid derivatives namely, the bis (O-butylxanthato) alkanes ( abbreviated as BBXAs or simply as bis-xanthates in this paper) have been synthesized in connection with the solvent extraction of precious metal ions. From an aqueous medium containing 0.1 M NaC10₄ (1 M=l mol dm^-3), these compounds exhibited high selectivity for extraction of Pd(II) and Ag(I) in dichloroethane, over most of the base metals as well as Pt(IV) and Au(III) ions. Towards Pd(II) and Ag(I) ions, the bis compounds act as SS chelating agents where the stabilities of the extractable complexes are determined by the length of the alkylene chain existing between the donor atoms. Pd(II) extraction has been studied in detail taking 13-bis(O-n-butylxanthato)propane (BnBXP) as the representative member of the series of bis-xanthates synthesized in this work. The extraction of palladium(II) was found to be quite slow in pure chloride medium. But, a mixed acid medium containing H₂SO₄ or HNO₃ in the presence of smaller amount of chloride ion provided optimum reversible extraction of palladium in dichloroethane, where Pd(II) forms 1:1 extractabic complexes with BnBXP. Pd(II) extraction is described in terms of the aqueous phase compositions, extraction and back-extraction data, extraction equilibrium, selectivity considerations and probable mechanisms of extraction.     

Synthesis of N-(aminoalkyl) chitosan for microcapsules

Chitosan was chemically modified by alkylation with N-(2-bromoethyl) phthalimide, N-(3-bromopropyl) phthalimide, and N-(4-bromobutyl) phthalimide. The resulting N-(phthalidimidoalkyl) chitosans were treated with hydrazine to remove the phthalidimido group resulting in the final N-(aminoalkyl) chitosan products. For comparison purposes, poly(vinyl alcohol) (PVA) was alkylated with N-(3-bromopropyl) phthalimide, then treated with hydrazine to give the N-(3-aminopropyl) PVA product. All alkylation products were characterized by solution ¹H- and ¹³C-NMR and by solid-state CP-MAS ¹³C-NMR. The above synthetic polymer derivatives, as well as chitosan, polyallyl amine, and polyethylen-imine, were used to form membrane coatings around calcium alginate beads in which blue dextran of molecular weight 7.08×10⁴ or 26.6×10⁴ was entrapped. These microcapsules were prepared by extrusion of a solution of blue dextran in sodium alginate into a solution containing calcium chloride and the membrane polymer. Membrane integrity and permeability were assessed by measuring the elution of the blue dextran from the capsules, spectrophotometrically. © 1993 John Wiley & Sons, Inc.     

Recovery of Platinum and Palladium from Chloride Solutions by a Thiodiglycolamide Derivative

The liquid-liquid extraction of platinum(IV) and palladium(II) from hydrochloric acid media was carried out using N,N’-dimethyl-N,N’-dicyclohexylthiodiglycolamide (DMDCHTDGA) in 1,2-dichloroethane (1,2-DCE). Pt(IV) is efficiently extracted from 5 M HCl onwards (%E ≥ 97%), whereas Pd(II) is quantitatively recovered from 1 to 8 M HCl solutions. Both Pt(IV) and Pd(II) can be successfully stripped from the loaded organic phases, the former with a 1 M HCl solution, the latter with 0.1 M thiourea in 1 M HCl. The maximum loading capacity of DMDCHTDGA for Pt(IV) could not be determined but it is high, since molar ratios extractant:Pt(IV) within 2 and 3 have been achieved. Data obtained from successive extraction-stripping cycles suggest a good stability profile of DMDCHTDGA towards Pt(IV) recovery. Attempts to replace 1,2-DCE by more environmentally-friendly diluents showed, in general, comparable %E for Pt(IV). The study of the influence of acidity, as well as chloride ion and DMDCHTDGA concentrations, allows a proposal for the composition of the Pt(IV) species formed upon extraction. Results obtained with binary metal ion solutions point out that Pt(IV) and Pd(II) can be efficiently separated from DMDCHTDGA loaded organic phases through sequential selective stripping.     

Study of Chromatographic Separation of Cesium,Europium, and Cobalt on Different Types of Tungstocerate Column Matrices

Interactions of ¹³⁴Cs(I), ^152,154Eu(III), and ⁶⁰Co(II) ions from HCl acid solutions with tungstocerate(IV) gel matrices, dried at 50°C, have been individually investigated by the batch equilibration method. The selectivity sequence was found to be in the order: Cs(I) >Eu(III) >Co(II). The breakthrough capacities of 12‐tungstocerate(IV) for Cs(I), Eu(III), and Co(II) were found to be 1.00, 0.55, and 0.26 mmol/g of the sorbent, respectively. In addition, a mixture of these radionuclides [6.20 × 10^?3 M Cs(I), 3.53 × 10^?3 M Eu(III), and 1.4 × 10^?3 M Co(II)], in 150 ml of 0.02 M HCl solution was passed through 1‐g 12‐tungstocerate(IV) chromatographic column. Quantitative uptake of both ¹³⁴Cs(I) and ^152,154Eu(III) has been achieved, while only ?22% of ⁶⁰Co(II) has been retained. Then, quantitative elution of the retained fraction of Co(II) was achieved with 14 ml of 0.1 M HCl acid solution leaving Eu(III) and Cs(I) strongly retained onto the column. Quantitative elutions of Eu(III) and Cs(I) were achieved by passing 20 ml of 0.3 M HCl and 16 ml of 2 M HCl acid solutions, respectively.     

The Solvent Extraction Performance of N,N’-Dimethyl-N,N’-Dibutylmalonamide Towards Platinum and Palladium in Chloride Media

The solvent extraction performance of N,N’-dimethyl-N,N’-dibutylmalonamide (DMDBMA) in 1,2-dichloroethane (1,2-DCE) towards platinum(IV) and palladium(II) in hydrochloric acid media was systematically evaluated. Pt(IV) extraction (%E) increases with the HCl concentration in the aqueous phases, being always higher than 72%, whereas Pd(II) extraction decreases from 65% at 1 M HCl to 22% at 8 M HCl. Several stripping agents for the two metals were tested: Pt(IV) is successfully recovered by a 1 M sodium thiosulfate solution, whereas the best result for Pd(II) was achieved with 0.1 M thiourea in 1 M HCl. The loading capacity of DMDBMA for Pt(IV) is high, and data obtained from successive extraction-stripping cycles suggest a good DMDBMA stability pattern. Attempts to replace 1,2-DCE by more environmentally-friendly diluents showed, in general, worse %E for Pt(IV). The dependence of Pt(IV) distribution coefficients on DMDBMA and chloride ion concentrations, as well as on acidity, are the basis of a proposal for the composition of Pt(IV) extracted species.     

Zinc(II) Extraction from Hydrochloric Acid Solutions using Amberlite XAD-7 Impregnated with Cyphos IL 101 (Tetradecyl(Trihexyl)Phosphonium Chloride)

Abstract

Cyphos IL 101 (tetradecyl(trihexyl)phosphonium chloride) was immobilized on Amberlite XAD-7. The extractant impregnated resin (EIR) was very efficient at removing Zn(II) from HCl solutions (optimum found between 2 and 4 M HCl). Metal ions were removed as anionic chlorocomplexes (ZnCl₄ ^2?) by ion exchange mechanism. The sorption strongly depended on the Cyphos IL 101 concentration in the EIR. The maximum sorption capacity was close to 20 mg Zn(II) g^?1 EIR (i.e. 0.40 mol Zn(II) mol^?1 Cyphos IL 101). The uptake kinetics were controlled by intraparticle diffusion (D_e: 1.2 10^?11 ? 6 10^?11 m² min^?1). Zn(II) can be easily desorbed using a number of eluents (including water and 0.1 M solution of HNO₃, H₂SO₄, and Na₂SO₄), which maintained performance levels over 5 cycles.     

Palladium(II) extraction from concentrated chloride media: Reactions involving thioamide derivatives

This work focuses on the detailed study of the palladium(II) extraction reactions by N-methyl-N-phenyl-octanthioamide (MPHTA) and N-methyl-N-cyclohexyl-octanthioamide (MCHTA) in toluene, since their ability to efficiently and selectively recover Pd(II) from a wide range of HCl concentrations is already known. Equilibrium data are presented and discussed, and further complemented by information depicted from UV–visible and NMR spectra. The determined apparent molar volumes show that MPHTA is monomeric, and MCHTA exhibits a slight tendency to aggregate. The Pd(II) extraction reactions by MPHTA and MCHTA are equivalent until 4.5 M HCl, passing through the formation of inner-sphere complexes with the metal ion.     

Separation of Palladium(II) and Platinum(IV) by Bulk Liquid Membranes during Electrodialysis

Abstract

The process of PdCl₄ ^2? and PtCl₆ ^2? separation extracting from binary hydrochloric mixtures as well as palladium(II) extraction from individual solutions by bulk liquid membranes containing diphenylthiourea and di‐o‐tolylthiourea in 1,2‐dichloroethane is studied at galvanostatic electrodialysis. The effects of the current density, the composition of the liquid membrane and of aqueous solutions on the rate of the metal transport are determined. It is shown that an effective separation of Pt(IV) from Pd(II) is achieved in the presence of an excess of the carrier. Maximum separation factor β_Pt/Pd of 380 is obtained in 1 hour of electrodialysis under optimal conditions. The transport of platinum(IV) is supposed to occur in the form of ionic associates (PdL₄Cl)₂PtCl₆. Platinum(IV) concentration and composition of the strip solution do not exert a considerable influence on the separation factor.