Dithiooxamide-Immobilized Microalgal Residue for the Selective Recovery of Pd(II) and Pt(IV)

Microalgal residue was chemically modified by immobilizing a functional group of dithiooxamide to prepare a novel type of adsorbent. This adsorbent exhibited high adsorption affinity and selectivity for Pd(II) and Pt(IV) whereas the adsorption of coexisting base metal ions was negligible. From the adsorption isotherms, this adsorbent was found to exhibit remarkably high adsorption capacity. The thermodynamic parameters indicated that the adsorption is governed by an endothermic reaction. The effective separation of Pd(II) and Pt(IV) from Cu(II) was confirmed also by a dynamic adsorption test. The effectiveness of elution of adsorbed Pd(II) and Pt(IV) was 85% and 96%, respectively.     

Quaternary Amine Modified Persimmon Tannin Gel: An Efficient Adsorbent for the Recovery of Precious Metals from Hydrochloric Acid Media

Persimmon tannin was chemically modified to prepare a quaternary amine type of adsorption gel, named as quaternary amine modified persimmon tannin (QAPT) gel. The QAPT gel has been used to investigate the adsorption behaviors for Au(III), Pd(II), and Pt(IV) from HCl media. It was found that the gel exhibited good selectivity towards precious metals over a wide concentration range of HCl. However, it exhibited poor affinity towards base metals such as Cu(II), Fe(III), Ni(II), and Zn(II). The adsorption isotherms of the gel for precious metal ions were described by the Langmuir model. The maximum adsorption capacities for Au(III), Pd(II), and Pt(IV) were evaluated as 4.16, 0.84, and 0.52 mmol g^?1, respectively. Although the anion exchange is the main mechanism for the adsorption of anionic species of Au(III), Pt(IV), and Pd(II), adsorption of Au(III) is followed by subsequent reduction, which results in the extraordinary high adsorption capacity for Au(III). Adsorption behavior of QATP gel for Au(III) was also compared to that of the persimmon tannin, the feed material.     

Polybenzimidazole resin based new chelating agents. Palladium(II) and platinum(IV) sorption on resin with immobilized dithiooxamide

Microporous polybenzimidazole (PBI) of 250–500 μm bead size has been epoxidized and subsequently reacted with dithiooxamide in the presence of a phase-transfer catalyst to obtain a sorbent with immobilized dithiooxamide, EPBI(DTOX). The sorption of Pd(II) and Pt(IV) in HCl solutions has been measured on both PBI and EPBI(DTOX) resins, employing the sorbate species singly, in mixtures, and in the presence of a number of base metal ions, which include Cu(II), Ni(II), Zn(II), Co(II), Fe(II) and Fe(III). The saturation sorption capacities (mg/g dry resin) of PBI for Pd(II) and Pt(IV) in 0.1 N HCl are 276 and 288, respectively, the corresponding values for EPBI(DTOX) being 157 and 168. The sorption capacities decrease with the acid strength of the medium, the change, however, being relatively more pronounced for PBI, so much so that in concentrated (> 1 N) acids the sorption of EPBI(DTOX) is higher than that of PBI. In mixtures of Pd(II) and Pt(IV) with 10-fold molar excess of Pt(IV), PBI and EPBI(DTOX) show, respectively, 80% and 85% selectivity for Pd(II). While EPBI(DTOX) exhibits high selectivity (> 85% and > 80%, respectively) for Pd(II) and Pt(IV) in the presence of 100-fold molar concentration of any of the above base metal ions, on PBI, however, the Pd(II) and Pt(IV) selectivities are reduced to 50% and 20%, respectively, by 100-fold molar concentration of Fe(II).The neutral chelating ligand thiourea causes rapid stripping of Pd(II) and Pt(IV) from PBI and EPBI(DTOX) resins. The sorbed metal ions on PBI, being bound as complex anions by ionic forces, are more easily stripped by strong acids than the sorbed metal ions which are bound to EPBI(DTOX) by chelation. Having a relatively lower binding constant, Pt(IV) is however more easily stripped than Pd(II), thus permitting a selective stripping of Pt(IV) on PBI. On the other hand, a selective stripping of Pd(II) can be achieved with a strong solution of thiocyanate, which prevents stripping of Pt(IV) while allowing that of Pd(II). Thus, separation of Pd(II) and Pt(IV) in mildly acidic solutions in the absence of Fe(II) can be conveniently achieved by sorption on PBI followed by stripping with a strong solution of thiocyanate. EPBI(DTOX), on the other hand, is more useful for separation in concentrated acid solutions and in the presence of large concentrations of base metal ions including Fe(II).     

Highly selective adsorption of Pt(IV) from spent catalyst by polyethyleneimine functionalized polyethylene/polypropylene non-woven fabric

Aiming at efficient recovery of platinum (Pt) from aqueous solution, the aminated polyethylene/polypropylene non-woven fabric (PE/PP NWF) was synthesized via radiation grafting of glycidyl methacrylate (GMA), followed by ring-opening reaction with polyethyleneimine (PEI). The effects of different parameters, including pH, sorption time, initial Pt(IV) concentration, competing ions and adsorbent dosage on the Pt(IV) adsorption performance were investigated by batch adsorption tests. A high Pt(IV) adsorption capacity of 485.0 mg g⁻¹ (initial concentration: 263.5 mg L⁻¹) was achieved, and the adsorption kinetics and isotherm conformed to the pseudo-second-order model and the Langmuir isotherm model, respectively. Moreover, the PEI functionalized PE/PP NWF exhibited excellent adsorption performance over the wide pH range (1–6), and also good selectivity for Pt(IV) over multiple coexisting metal cations (Ni, Cu, Co, Pb, Mg, and Zn). The recovery ratio of Pt from spent proton exchange membrane fuel cell (PEMFC) catalysts reached 89.7% after three cycles of regeneration.     

Synthesis of chemically modified chitosan with 2,5‐dimercapto‐1,3,4‐thiodiazole and its adsorption abilities for Au(III), Pd(II), and Pt(IV)

A new chemically modified chitosan hydrogel with 2,5‐dimercapto‐1,3,4‐thiodiazole (CTS‐DMTD) has been synthesized. The structure of CTS‐DMTD was confirmed by elemental analysis and FTIR. It was found that adsorption capacities were significantly affected by the pH of solution, with optimum pH values of 3.0 for Au(III), 2.0 for Pd(II) and Pt(IV). The saturated adsorption capacities were 198.5 mg/g for Au(III), 16.2 and 13.8 mg/g for Pd(II) and Pt(IV), respectively. Langmuir and Freundlich isotherm adsorption models were applied to analyze the experimental data. The results showed that adsorption isotherms of Pd(II) and Pt(IV) could be well described by the Langmuir equation. The adsorption kinetic investigations indicated that the kinetic data correlated well with the pseudo‐second‐order model. The recovery experimental data showed that CTS‐DMTD had a higher affinity toward Au(III), Pd(II), and Pt(IV) in the coexistence system containing Cu(II), Fe(III), Cd(II), Ni(II), Mg(II), and Zn(II). The studies of desorption were carried out using various reagents and the optimum effect was obtained using thiourea. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation of chemically active mesoporous adsorbent for pt(II) and pd(II) adsorption from aqueous solutions

Chemically active mesoporous silica was prepared via grafting of N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole. Binding behavior of the adsorbent toward Pt(II) and Pd(II) ions was investigated. In addition, the properties of the adsorbent, such as pore structure and pore uniformity, were also examined. Results showed that the adsorbents developed in this study have high affinity for noble metal ions, such as Pt(II) and Pd(II), in aqueous solutions. This paper is dedicated to Professor Wha Young Lee on the occasion of his retirement from Seoul National University.     

Highly efficient and fast adsorption of Au(III) and Pd(II) by crosslinked polyethyleneimine-glutaraldehyde

An adsorbent (PEI-GA) is prepared by crosslinking polyethyleneimine with glutaraldehyde. PEI-GA shows outstanding adsorption performance towards Au(III) and Pd(II). PEI-GA presents large adsorption capacity towards Au(III) in a wide application pH range from 1 to 9. The adsorption capacities of PEI-GA for Au(III) and Pd(II) at 25°C reach 2575 and 497 mg/g, respectively. Au(III) and Pd(II) can be adsorbed completely within 10 min for 8.3 mg/L Au(III) and 20 min for 9.7 mg/L Pd(II). The adsorption equilibrium time required for 523.9 mg/L Au(III) and for 565.6 mg/L Pd(II) is 2 and 9 h, respectively. The Sips model is the most suitable to describe the adsorption isotherms which leads to more realistic adsorption capacities for both metals. PEI-GA also exhibits high selectivity and repeatability towards Au(III) and Pd(II). The adsorption mechanism involves redox, chelation coordination, and electrostatic interactions for Au(III), and coordination and electrostatic interactions for Pd(II).     

Effective and Selective Recovery of Precious Metals by Thiourea Modified Magnetic Nanoparticles

Adsorption of precious metals in acidic aqueous solutions using thiourea modified magnetic magnetite nanoparticle (MNP-Tu) was examined. The MNP-Tu was synthesized, characterized and examined as a reusable adsorbent for the recovery of precious metals. The adsorption kinetics were well fitted with pseudo second-order equation while the adsorption isotherms were fitted with both Langmuir and Freundlich equations. The maximum adsorption capacity of precious metals for MNP-Tu determined by Langmuir model was 43.34, 118.46 and 111.58 mg/g for Pt(IV), Au(III) and Pd(II), respectively at pH 2 and 25 °C. MNP-Tu has high adsorption selectivity towards precious metals even in the presence of competing ions (Cu(II)) at high concentrations. In addition, the MNP-Tu can be regenerated using an aqueous solution containing 0.7 M thiourea and 2% HCl where precious metals can be recovered in a concentrated form. It was found that the MNP-Tu undergoing seven consecutive adsorption-desorption cycles still retained the original adsorption capacity of precious metals. A reductive adsorption resulting in the formation of elemental gold and palladium at the surface of MNP-Tu was observed.     

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.     

Syntheses and characterization of polystyrene‐supported 2,5‐dimercapto‐1,3,4‐thiodiazole and its sorption behavior for Pd(II), Pt(IV), and Au(III)

A type of chelating resin crosslinking polystyrene‐supported 2,5‐dimercapto‐1,3,4‐thiodiazole (also called bismuththiol I, BMT), containing sulfur and nitrogen atoms, was prepared. The structure of PS‐BMT was confirmed by FTIR, elemental analysis, and X‐ray photoelectron spectroscopy (XPS). Adsorption of Pd(II), Pt(IV), and Au(III) was investigated. The capacity of PS‐BMT to adsorb Pd(II) and Pt(IV) was 0.190 and 0.033 mmol/g, respectively. The adsorption dynamics of Pd(II) showed that adsorption was controlled by liquid film diffusion and that the apparent activation energy, E_a, was 32.67 kJ/mol. The Langmuir model was better than the Freundlich model in describing the isothermal process of Pd(II), and the ΔG, ΔH, and ΔS values calculated were ?0.33 kJ/mol, 26.29 kJ/mol, and 87.95 J mol^?1 K^?1, respectively. The mechanisms of adsorption of Pd(II), Pt(IV), and Au(III) were confirmed by XPS. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 631–637, 2006     

Adsorption of platinum(IV) from an aqueous solution with magnetic cellulose functionalized with thiol and amine as a nano‐active adsorbent

In this study, magnetic cellulose was prepared and then functionalized by the grafting of glycidyl methacrylate and reaction with thiourea/amine [to produce grafted magnetic cellulose with thiol/amine (GMC–N/S)]. Thus, GMC–N/S as a nano‐active adsorbent was investigated for the adsorption of Pt(IV) in a batch system. A response surface methodology was used to study the effects of four independent variables [Pt(IV) concentration, temperature, pH of the solution, and adsorbent dose] and to optimize the process conditions for the maximum adsorption of platinum(IV) from aqueous solutions by GMC–N/S. A high coefficient of determination (R² = 98.46) implied the adsorption of Pt(IV) onto the adsorbent in a valid manner, and only 1.54% of the total variable was not explained by the model. The equilibrium adsorption data were fitted to the Langmuir isotherm. The maximum monolayer adsorption capacity of the adsorbent (GMC–N/S) for Pt(IV) was determined to be 40.48 mg/g. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45361.     

CHARACTERISATION OF METALFIX-CHELAMINE AND ITS APPLICATION IN PRECIOUS METAL ADSORPTION

ABSTRACT

The physical and chemical characteristics of the chelating resin Chelamine, which contains a pentamine ligand, are investigated in order to consider its application in the separation of precious metals- Adsorption isotherm experiments for Pt, Pd and Au and kinetic experiments were carried out under batch procedures. The resin presents a high level of adsorption selectivity for Pt(IV), Au(III) and Pd(II) giving a capacity of 2.8 mmol/g, 3.1 mmol/g and 2.0 mmol/g respectively. Acidic solutions, complexing agents, lipophilic anions and ammonia were used for metal elution. NaClO₄ solutions are the most effective eluting agents for Pt(IV) while thiourea is the best stripping agent for both Pd(II) and Au(III). Selective separation of the three metals can be achieved by sequential elution from the resin with NaClO₄ solutions in different HCl concentrations and thiourea 0.5 M.     

Adsorption of Noble Metals Using Silica Gel Modified with Surfactant Molecular Assembly Containing an Extractant

Silica gel modified with a surfactant, Triton X-100 molecular assembly containing an extractant, 1-(2-pyridylazo)-2-naphthol, was prepared as an adsorbent to adsorb palladium, platinum, and gold. In this study, methods of metal recovery and mutual separation from the metal coexisting solution were studied by using the modified silica gel (PT100S). The effects of pH, chloride-ion, and metal-ion concentrations on the metal adsorption rate were evaluated through batch experiment. Pd(II) and Au(III) were adsorbed on PT100S, while Pt(IV) was not adsorbed. Furthermore, it was found that Pd(II) reacted with an adsorption site on PT100S, and that Au(III) reacted with a different adsorption site from Pd(II). These results enabled to separate the metals using a column packed with PT100S.     

Selective Pd(II) and Pt(IV) sorption using novel polymers containing azamacrocycle functional groups

The synthesis of a new coordinating polymer containing nitrogen atoms by the copolymerization of a 15-membered triolefinic azamacrocycle, 9, named (E,E,E)-1-[(4-methylphenyl)sulfonyl]-6-[(2-trimethylsilylethyl)sulfonyl]-11-[(4-vinylphenyl)sulfonyl)]-1,6,11-triazacyclopentadeca-3,8,13-triene, with styrene is achieved. The novel polymeric material is characterized by means of elemental analysis, IR, ¹³C-CP MAS, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) techniques. We also report the study of palladium and platinum sorption from acidic solutions. A capacity of 0.36 mmol g⁻¹ of polymer for Pd(II) and 0.28 mmol g⁻¹ of polymer for Pt(IV) is determined by the batch-mode. The functionalised polymer presents a high selectivity towards precious metals over base metals such us Cu(II) and Ni(II).     

1,3,5-Triazine-pentaethylenehexamine polymer for the adsorption of palladium (II) from chloride-containing solutions

A triazine-hexamine (TAPEHA) polymer demonstrating high acid-resistance, good affinity to noble metals, and a high density of amine and triazine functional groups has been designed and synthesized. The obtained polymer was used as an adsorbent for the recovery of palladium (II) ions from chloride-containing solutions. Effects of pH, pCl, contact time, initial Pd(II) concentration, and temperature on adsorption were investigated and optimized by batch adsorption experiments. The pseudo second-order kinetic equation provides the best correlation for the process. While five isotherms were used, the nonlinear resolution of the Langmuir isotherm equation has been found to provide the closest fit to the equilibrium data. The monolayer adsorption capacity which is highest among literature is 517.2 mg/g. All thermodynamic parameters suggest that Pd(II) adsorption onto TAPEHA particles is a spontaneous, physisorptive, and exothermic process. The formation of TAPEHA and Pd-adsorbed TAPEHA has been characterized by FE-SEM, EDAX, XRD, and FTIR instrumentations. Adsorption of the negatively charged chloropalladium (II) species mostly takes place via ligand exchange mechanism. Ease of synthesis and low cost, coupled with highly efficient and rapid removal of Pd(II) ions, make TAPEHA an attractive adsorbent.     

Temperature-swing adsorption of precious metal ions onto poly(2-(dimethylamino)ethyl methacrylate) gel

The temperature-swing adsorption (TSA) of heavy metal ions onto 2-(dimethylamino)ethyl methacrylate (DMAEMA) gel has been examined. The DMAEMA gel adsorbs precious metal ions (Pt(IV), Au(III), and Pd(II)) in HCl aqueous media as a result of the electrostatic interactions between the protonated amino groups in the gel and the anionic chloro complexes, while it is inactive against Cu(II) and Ni(II) cations. The amount of Pt(IV) ions adsorbed onto the DMAEMA gel decreases linearly with an increase in temperature. The TSA operation was successfully carried out; the DMAEMA gel repeatedly adsorbed and desorbed Pt(IV) ions in the temperature-swing operation between 20 °C and 60 °C. The TSA technique using the DMAEMA gel is simple, environment-friendly, and potentially applicable in various separation processes for precious metals in industries.     

Highly selective separation and recovery of Pd(II) from the automotive catalyst residue with the thiocarbamoyl substituted azothiacalix[4]arene derivative

New ligand, namely, 5, 11, 17, 23-tetrakis-((p-chlorophenyl) azo)-25,26,27,28-tetrakis ((dimethylthio carbamoyl)oxy) thiacalix[4]arene (CADTTCA), has been investigated for separation and recovery of Pd(II) through solvent extraction technique. Experimental parameters such as contact time, diluents, effect of H⁺ and Cl^? concentration, and acid durability have been thoroughly investigated. The loading capacity toward Pd(II) was determined to be 113 mg/L using 0.25 mM CADTTCA. The extractant showed high selectivity and extractability for Pd(II) than the other metal ions present in automotive catalyst residue (ACR) solution containing platinum group (PGMs) metal ions (i.e., Pd(II), Pt(IV), Rh(II), La(III), Al(III) and Ce(III)). The recovery percentage of Pd(II) was 98% after five extraction-scrubbing-stripping cycles. The probable extraction mechanisms were established through the FT-IR spectral analysis.     

Efficient Removal of Hg(II) by Polymer-Supported Hydrated Metal Oxides from Aqueous Solution

Chelating PS-EDTA resins modified by metal (Fe, Al, and Zr) oxides were used as adsorbents to remove Hg(II) from aqueous solutions. The modified resins were characterized by BET, FTIR, and XPS. The amino, carboxylate, and the metal oxides on resins exhibited a synergistic effect for Hg(II) removal. It was observed that the modification of PS-EDTA resin not only increased the adsorption of Hg(II) but also accelerated the adsorption rate of Hg(II). The equilibrium data of Hg(II) were best described by the Freundlich isotherm, and the kinetics were found to follow the pseudo-second-order kinetic model. Also, thermodynamic parameters showed that Hg(II) adsorption was endothermic and spontaneous in nature. The increasing the concentration (0.1–2.0 g/L) of NaNO₃ in Hg(II) solution did not affect the adsorption of Hg(II). Moreover, the competitive adsorption indicated that the modified resins had higher selectivity towards Hg(II) over Cd(II), Pb(II), Zn(II), or Cu(II) in a binary system. All of the above results indicated that the modified resin was an efficient and reusable adsorbent for Hg(II) removal due to its simple preparation, high adsorption capacity, fast adsorption rate, ionic strength independence, high selectivity, and good reusability. These properties are of potential application in the fixed-bed continuous-flow column for Hg(II) removal from wastewaters.     

Selective separation and concentration of Pd(II) from Fe(III), Co(II), Ni(II), and Cu(II) ions using thiourea‐formaldehyde resin

Thiourea‐formaldehyde (TUF), a well‐known chelating resin, has been synthesized and it was used in the adsorption, selective separation, and concentration of Pd(II) ions from Fe(III), Co(II) Ni(II), and Cu(II) base metal ions. The composition of the synthesized resin was determined by elemental analysis. The effect of initial acidity/pH and the adsorption capacity for Pd(II) ions were studied by batch technique. The adsorption and separation of Pd(II) were then examined by column technique. FTIR spectra and SEM/EDS analysis were also recorded before and after the adsorption of Pd(II). The optimum pH was found to be 4 for the adsorption. The adsorption data fitted well to the Langmuir isotherm. The maximum adsorption capacity of the TUF resin for Pd(II) ions was found to be 31.85 mg g⁻¹ (0.300 mmol g⁻¹). Chelating mechanism was effective in the adsorption. Pd(II) ions could be separated efficiently from Fe(III), Cu(II), Ni(II), and Co(II) ions using TUF resin. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Adsorption Behaviors of Platinum Group Metals in Simulated High Level Liquid Waste Using Macroporous (MOTDGA-TOA)/SiO2-P Silica-based Absorbent

As fundamental research for separation of platinum group metals (PGMs) from high level liquid waste (HLLW) by macroporous silica-based adsorbent, (MOTDGA-TOA)/SiO₂-P adsorbent was prepared by impregnation of N,N′-dimethyl-N,N′-di-n-octyl-thiodiglycolamide (MOTDGA) and Tri-n-octylamine (TOA) into silica/polymer composite support (SiO₂-P). The adsorption behavior of Ru(III), Rh(III), and Pd(II) in simulated HLLW onto the adsorbent were investigated by the batch method to obtain their corresponding equilibrium and kinetic data. The adsorbent showed strong adsorption for Pd(II) and the adsorption reached equilibrium within 2 hr. High distribution coefficient (K _d) values for Pd(II) were obtained in 0.1–1 M HNO₃ concentration. In addition, the use of both MOTDGA and TOA improved adsorption of Ru(III) and Rh(III) better than individual use of them. Especially, the K _d value for Ru(III) towards (MOTDGA-TOA)/SiO₂-P adsorbent was three times larger than that in the adsorption using only with MOTDGA or TOA as extractant. The adsorptions of Ru(III), Rh(III), and Pd(II) followed the Langmuir adsorption model, and were found to be controlled by the chemisorption mechanism.