Recovery Of Platinum Group Metals Research Articles

Recovery of platinum-group metals (PGMs) from spent automotive catalysts: Part I: The primary and secondary sources of PGMs and their use

This paper presents a review of the present situation and perspectives in the production of platinum-group metals from primary and secondary sources, as well as in their use. The need and significance of recycling have been highlighted in view of the demand and supply of platinum-group metals. It has been shown that platinum-group metals are mostly used for the manufacture of autocatalysis and that their recycling is important for the conservation of natural resources.

Behavior of Platinum Group during Their Pyrometallurgical Recovery from Spent Automotive Catalysts

The behavior of platinum group metals (PGMs) during their recovery with smelting of spent automotive ceramic catalysts powder in the presence of metallic copper at elevated temperatures is studied in this paper. Two different metal recovery mechanisms proved to be active in this process: 1) Wetting of micro-dispersed particulates of PGMs in the slag by molten copper, formation of copper droplets with attracted microparticles of PGMs and settling of the molten droplets of Cu-PGMs alloy through the slag at the bottom of the crucible (“wetting”); 2) Settling of solid PGMs microparticles through the molten slag and formation of a solid solution with the molten copper at the bottom of the crucible (“settling”). The PGMs are divided in two separate groups. Platinum has under the same experimental conditions substantially higher recovery in comparison with the palladium and rhodium that behave as a group having almost identical recoveries. The heavier Pt is recovered primarily in big extent (almost 88%) through the “settling” mechanism while Pd and Rh are recovered following a more balanced mixture of both mechanisms with the “settling” one to be again more important (66% for Pd and 57% for Rh). Slag viscosity is the most important physical property and the design of an appropriate slag system is the most important issue in developing an efficient process for the recovery of PGMs.

폐촉매(廢觸媒) 염산침출액(鹽酸浸出液)에서 컬럼형 추출기(抽出器)에 의한 백금(白金) 회수(回收)

Abstract In order to recover Pt from the hydrochloric acid leaching solution of spent catalysts, bench scale Karr reciprocating columnwas employed. At an optimum flow rate and vibration frequency, iron and Pt was completely extracted by using TBP and Aliquat336. At the same vibration frequency, iron and Pt was completely stripped by HCl and HClO 4 after adjusting the flow rate. Inthe case of extraction of HCl from the raffinate with TEHA, it was difficult to maintain the stability of the column extractor.A comparison of the operation results between column extractor and mixer-settler is reported. Key words : Pt, Fe, HCl, Karr reciprocating column 1. Introduction Spent catalysts are valuable secondary resourcesfor the platinum group metals (PGMs). Much workhas been done on the recovery of PGMs from spentcatalysts by hydrometallurgical method. First, PGMsare dissolved by chloride based solution and thenare separated by employing solvent extraction or * Received : July 9, 2013·Revised : August 7, 2013·Accepted : August 21, 2013Corresponding Author : Man-Seung Lee (E-mail : mslee@mokpo.ac.kr)Department of Advanced Materials Science & Engineering, Mokpo National University, 61 Dorim-ri, Chungkye-myun, Muan-gun, Chonnam, 534-729, KoreaTel : +82-62-450-2492 / Fax : +82-62-450-2498ⓒThe Korean Institute of Resources Recycling. All rights reserved. This is an open-access article distributed under the termsof the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/), which permitsunrestricted non-commercial use, distribution and reproduction in any medium, provided the original work is properly cited.

Cationic polymer-immobilized polysulfone-based fibers as high performance sorbents for Pt(IV) recovery from acidic solutions

This work reports a novel concept for the development of a polysulfone (PS)-based fiber as a high-performance acid-tolerant adsorbent for the recovery of platinum group metals (PGMs), particularly Pt(IV), in acidic media. Polyethylenimine (PEI)-coated PS-Escherichia coli biomass composite fiber (PEI-PSBF) was prepared by spinning biomass-PS blends in water, coating with PEI and cross-linking with glutaraldehyde. The E. coli biomass on the fiber was executed as a functional group donor for binding PEI. PS fiber (PSF), PS-biomass composite fiber (PSBF), and PEI-modified PSF (PEI-PSF) were also prepared and compared with PEI-PSBF. The results of SEM and FTIR analyses revealed the presence of PEI on the surface of PEI-PSBF. Kinetic and isotherm experiments showed the negligible sorption capacity of PSF. In contrast, adsorption equilibrium on PSBF and PEI-PSBF was attained after 40min and 6h, respectively. The maximum Pt(IV) uptake of PEI-PSBF was 6.6 times higher than that of PSBF. Pt(IV) ions were completely recovered from loaded PEI-PSBF by 0.1M thiourea in 1M HCl solution. The PEI-PSBF was also stable in 0.1M and 1M HCl solutions. The PEI-PSBF exhibited promising properties as an adsorbent for PGMs-containing acidic wastewaters.

DETERMINATION OF LEACHING PARAMETERS FOR THE RECOVERY OF PLATINUM GROUP METALS FROM SECONDARY MATERIALS

The leaching parameters for the recovery of platinum group metals were investigated with potentiostatic measurements using wire electrodes. The dissolution rates of Pt, Pd and Rh were measured in concentrated NaCl solution. The parameters inspected were the temperature, redox potential and chloride content. Measurements were done at temperatures 25-94 °C using four different NaCl concentrations, 62.5-250 g/l. Measurements were done at potentials of 950-1250 mV vs. SCE for Pt and Rh and 380-470 mV vs. SCE for Pd. Although higher temperature, potential and chloride content generally increased the dissolution rate, the effect was found to be nonlinear and slightly different for different metals. Based on the results, strongly oxidizing conditions are needed for the leaching process in order to achieve reasonable dissolution rates.

Selective Recovery of Platinum Group Metals from Spent Automobile Catalyst by Integrated Ion Exchange Methods

Selective recovery of platinum group metals (PGMs), such as Pd, Pt, and Rh, from spent automobile catalyst has been investigated by integrated ion exchange method using dihexyl sulfide (DHS) impregnated resin and commercial weak anion exchange resin (Diaion WA-21) as adsorbents. Batchwise adsorption revealed that the DHS impregnated resin possesses the selective adsorption ability for Pd and WA-21 possesses selectivity for all PGMs, especially Rh. Chromatographic separation of Pd with column packed with DHS impregnated resin can be selectively achieved. The chromatographic separation of Pd and Pt with a column packed with WA-21 is effectively progressed, while that of Rh is insufficient yield due to a slow adsorption rate. Separation of Rh from other two PGMs can therefore be achieved by switching the eluent. Both adsorbents show almost no adsorption abilities for other heavy metals containing in the spent automobile catalyst. Sequential chromatographic operation of the column packed with DHS impregnated resin followed by the column packed with WA-21 can be finally achieved to recover mutual PGM from leaching solution of spent automobile catalyst.

자동차(自動車) 폐촉매(廢觸媒)의 침출액(浸出液)으로부터 시멘테이션에 의한 백금족(白金族) 금속(金屬)의 회수(回收)

금속분말을 환원제로 사용하는 시멘테이션에 의하여 자동차 폐촉매의 침출액과 침출잔사의 세척액으로부터 백금족 금속을 환원 석출시켜 회수하는 연구를 수행하였다. 환원제로 사용한 알루미늄, 마그네슘 그리고 아연이 백금족 금속의 시멘테이션에 미치는 영향을 조사하였으며 알루미늄을 최적 환원제로 선정하였다. 침출액에 19.3 당량의 알루미늄을 첨가하고 <TEX>$50{\sim}60^{\circ}C$</TEX>에서 10분간 시멘테이션을 행하였을 때 백금, 팔라듐, 로듐의 환원석출율은 각각 99.3%, 99.4%, 90.2% 정도 이었다. 또한 세척액에 알루미늄을 45 당량 투입한 후 시멘터이션 반응을 통해 백금, 팔라륨, 로듐을 각각 97%, 97%, 90% 회수할 수 있었다. 그리고 회수한 환원석출물의 금속불순물들을 질산침출로 제거함으로써 백금족 금속의 품위를 약 10% 정도 향상시킬 수 있었다. The recovery of platinum group metals (PGMs) from the leach solution of spent auto-catalyst and the wash solution of the leach residue was investigated in the laboratory scale experiments by the cementation process using metal powders as the reductant. In this study, the effect of Al, Mg and Zn powders on the cementation process was particularly examined. Aluminum powder was selected as the most suitable reductant for the cementation of PGMs. At the cementation time of 10 minute under the aluminium stoichimetric amount of 19.3 and the reaction temperature of <TEX>$50{\sim}60^{\circ}C$</TEX>, the recovery of platinum group metals from the leach solution of the spent auto-catalyst was found to be 99.3%, 99.4%, 90.2% for Pt, Pd and Rh, respectively. Under the same conditions with the aluminium stoichimetric amount of 45, the recovery of platinum group metals from the wash solution of the leach residue of spent catalyst was observed to be 97%, 97% and 90% for Pt, Pd and Rh, respectively. In addition, it was possible to upgrade the platinum group metals in the precipitates obtained from the cementation process by about 10% through the removal of metal impurities by the nitric acid leaching at ambient temperature.

용융기술(熔融技術)을 이용(利用)한 자동차폐촉매(自動車廢觸媒)에서의 백금족(白金族) 금속(金屬) 회수(回收) 연구(硏究)

자동차 폐촉매로부터 폐촉매 중에 함유되어 있는 백금족 금속(Pt, Rh, Pd)를 회수하는 방법으로는 크게 건식법과 습식법이 현재 이용되고 있다. 본 연구에서는 건식 용융법으로 폐촉매로부터 백금족 금속 회수하기 위한 기초 실험으로 포집금속으로 Fe와 Cu을 사용하여 폐촉매를 용융하였을 때 각각의 농도 변화를 비교함으로써 용융 조건과 적정 포집금속으로 찾는 것을 목적으로 하였다. 본 실험으로 얻어진 결과를 요약하면 Fe을 포집금속으로 히는 것이 Cu을 포집금속으로 사용하는 것보다 회수율 측면에서 유리하였으며, 용융 처리 온도는 <TEX>$1,500^{\circ}C$</TEX>에 비교하여 <TEX>$1,600^{\circ}C$</TEX> 용융 하였을 때 슬래그 중 잔류하는 백금족 금속의 농도 변화율이 크게 향상되었다. 용융 온도 <TEX>$1,600^{\circ}C$</TEX>의 경우 처리 후 슬래그 중 백금족 원소인 Rh, Pd, Pt의 평균 농도는 각각 6.21 ppm, 5.98 ppm, 6.97ppm으로, 이는 용융 온도 <TEX>$1,500^{\circ}C$</TEX>시 보다도 슬래그 백금족 원소 중 Rh와 Pd는 농도변화율 측면에서 각각 50.58%, 55.31%향상되었다. 그러나 폐촉매 중의 Pt의 초기농도가 12.9 ppm으로 낮아 용융처리 후 농도변화율의 비교가 어려웠다. The dry method and wet method are currently used for the recovery of platinum group metals (Pt, Rh, Pd) contained in spent automobile catalysts. The study herein aims to identify the melting condition and optimum collector metal in accordance with a comparison of each concentration change in melting waste catalysts, using Fe and Cu in a basic experiment to recover waste catalysts through application of the dry melting method. As a summarized result of the experiment herein, it was determined to be more advantageous to use Fe as a parent material rather than Cu from the aspect of recollection rate, and the concentration change rate of platinum group metals within slag was greatly enhanced at <TEX>$1,600^{\circ}C$</TEX> melting condition rather than at <TEX>$1,500^{\circ}C$</TEX> in terms of melting processing temperature. The mean concentration of platinum group metals - Rh, Pd and Pt - within slag after a melting process at <TEX>$1,600^{\circ}C$</TEX> were 6.21 ppm, 5.98 ppm and 6.97 ppm. The Rh and Pd were 50.58% and 55.31% respectively greater than the concentration change rate of platinum group metals in slag at a melting temperature of <TEX>$1,500^{\circ}C$</TEX>. However, since the initial concentration of Pt within the waste catalysts was 12.9 ppm, is relatively low, it was difficult to compare concentration change rates after the melting process.

Electrodeposition of ruthenium, rhodium and palladium from nitric acid and ionic liquid media: Recovery and surface morphology of the deposits

Electrodeposition is a promising technique for the recovery of platinum group metals with unique surface morphologies. The electrodeposition of palladium, ruthenium and rhodium from aqueous nitric acid, and non-aqueous 1-butyl-3-methylimidazolium chloride ionic liquid medium was studied at stainless steel electrode. The surface morphology and elemental composition of the resultant deposit were probed by scanning electron microscopy (SEM) and energy dispersive X-ray (EDS) analysis. Deposits with diverse surface morphologies and metal compositions were obtained by varying the composition of the electrolytic medium and applied potential. The results demonstrate the possibility of tailoring the morphologies of PGMs by controlling the composition and potential needed for electrodeposition.

Recovery by hydrometallurgical extraction of the platinum-group metals from car catalytic converters

The car industry is one of the technological applications which more platinum-group metals (PGM) employs. Therefore, the recovery of the PGMs from the car catalytic converters could be an important source to obtain these precious metals, with economic and environmental consequences. In this work, the car catalytic converters were characterized through different techniques as X-ray diffraction, scanning electron microscopy and inductively coupled plasma. In order to suggest an environmentally friendly method for the recovery of PGMs, some conditions such as the reagents concentration and composition, energy optimization, pre-treatment in hydrogen atmosphere and a thermal pre-treatment were studied. In addition, a new alternative to recover at least the 95% of the PGMs present in the car catalytic converters by the application of lees aggressive, corrosive or expensive reagents and conditions is proposed.

A case study of optimising UG2 flotation performance part 2: Modelling improved PGM recovery and Cr 2O 3 rejection at Northam’s UG2 concentrator

In Part 1 of this 2 part series of papers the relationships between Platinum Group Metals (PGM), mass and water recovery and %Cr 2O 3 (as chromite) in concentrate were defined for laboratory, pilot and plant scales. The entrainment of chromite in final concentrate was shown to be related to its slow floating kinetics. In 2004, Northam Platinum mine embarked upon an upgrading program on its UG2 plant which included the installation of two column cells with external spargers as final cleaners. Optimisation resulted in a PGM recovery increase of 6% whilst %Cr 2O 3 in final concentrate was reduced from 4.0% to 2.2%. In this second paper, the Northam circuit is modelled before and after modification and installation of the final cleaner column cells. Simulation shows that the external sparger, driven by a dedicated recirculation pump, imparts energy into the system and provides the column with a PGM recovery capability equal to that of a mechanically driven cell. The deep froth bed of the columns enhances chromite rejection. As a result of this, greater operating flexibility has allowed PGM recovery at Northam to be increased by increasing mass pull whilst at the same time reducing %Cr 2O 3 in concentrate. Modelling shows that Northam’s reduction in %Cr 2O 3 can be fully described by reducing only the laboratory to plant scale-up factor for slow floating rate of chromite by 25%, whilst leaving the normal scale-up factors for fast floating fraction and rate unchanged. The improvement in PGM recovery was simulated using the same set of rougher and cleaner feed PGM kinetics and scale-up factors. This suggests that chromite entrainment is modelled via its slow floating rate and PGM recovery by true flotation is primarily modelled via its fast floating fraction and rate. Floatable gangue is modelled via its full set of fast and slow kinetics as its passage into final concentrate (and cleaner tailings circulating load) is a mix of true flotation and entrainment. This case study shows that a standard flotation circuit and one incorporating Northam’s column cell may be predicted from laboratory scale rate tests and flotation kinetics. The impact of Northam’s technology on other UG2 ores may be predicted by applying the change in chromite scale-up factors determined by simulation. The degree of improvement is dependant on the ore’s mineralogy and specifically its selectivity between PGM minerals, chromite and floatable gangue. This is illustrated by simulating the impact of the Northam column cell on Barrick’s Sedibelo UG2 ore.

Selective recovery of catalyst layer from supporting matrix of ceramic-honeycomb-type automobile catalyst

Natural resources of platinum group metals (PGMs) are limited and their demand is increasing because of their extensive uses in industrial applications. The low rate of production of PGMs due to low concentration in the related natural ores and high cost of production have made the recovery of PGMs from previously discarded catalytic converters a viable proposition. The ceramic-honeycomb-type automobile catalytic converter contains appreciable amount of PGMs. These valuable substances, which are embedded in the catalyst layer and covered on the surface of the supporting matrix, were selectively recovered by attrition scrubbing. The attrition scrubbing was effective for the selective recovery of catalyst layer. The process was convinced as the comminution and separation process by physical impact and shearing action between particles in the scrubbing vessel. The catalyst layer was dislodged from the surface of the supporting matrix into fine particles by attrition scrubbing. The recovery of Al 2O 3 and total PGMs in the fraction less than 300 μm increased with the residence time whereas their contents in the recovered materials slightly decreased. The interparticle scrubbing became favorable when the initial input size increased. However, the solid/liquid ratio in the mixing vessel was slightly affected by the low density of converter particles.

Balancing the reagent suite to optimise grade and recovery

The recovery of Platinum Group Metals and Gold (PGM + Au) from the UG-2 reef of the Bushveld Complex is an interesting challenge when the selection and optimisation of the reagent suite is considered. The UG-2 reef is characterised by two predominant gangue phases i.e. chromite and silicate, that have significantly different physical and chemical properties. A strategy needs to be devised to address concentrate grade that will reduce the recovery of gangue without significantly affecting the recovery of the valuable species. Recovery of the valuable species is complicated by the fact that PGM + Au occurs as a variety of different minerals having varying chemical and physical properties. The operating strategy has to consider the characteristics of the valuable mineral species and maximise recovery while meeting stringent grade specifications. Laboratory tests are conducted to illustrate the effect of the various flotation parameters. Applications of the findings on existing concentrators are discussed illustrating the need for a better understanding of the contribution of the various mechanisms occurring in the flotation cell. The paper demonstrates the significance of entrainment in the recovery of both valuable species and gangue species, and the need for a greater understanding of this non-selective sub-process on overall circuit performance. This paper forms part of a postgraduate study through the University of Cape Town into the development of a mechanistic model for the entrainment process. Although much work has been done in this study of the effect of various other parameters on the flotation of UG-2 ore, this paper focuses on the effect of frother, depressant and water on the flotation results.

Recovery of platinum group metals from secondary materials. I. Palladium dissolution in iodide solutions

Thermodynamic predictions are reported for platinum and palladium in aqueous ammonia and iodide solutions, to define less aggressive conditions than used hitherto for leaching palladium and platinum from secondary materials. Cyclic voltammetry and amperometry of thin films of palladium, electrodeposited onto rotating vitreous carbon disc electrodes, indicated that partially oxidised adsorbed species passivated dissolution in aqueous ammonium sulfate. By contrast, dissolution rates in aqueous potassium iodide solutions were a significant fraction of that corresponding to the mass transport controlled rate of reduction of tri-iodide, which was demonstrated to be a suitable oxidant for the envisaged metal recovery process. However, iodide concentrations > 1 m were required to achieve adequate solubility of the oxidation products, assumed to be PdI42− ions, thereby avoiding inhibition by PdI2. The reduction of tri-iodide on palladium was very facile, with large exchange current densities and Tafel coefficients; two alternative mechanisms are proposed that fitted experimental results well. In addition, a kinetic model to predict dissolution rates of Pd in tri-iodide solutions gave good agreement with experimental data, provided an equilibrium constant of 10−4.5 was used for the PdI2/PdI42− reaction, rather than the value of 10−2.8 derived from thermodynamic data.

Adsorption Behavior of Platinum Group Metals (Pd, Pt, Rh) on Nonylthiourea‐Coated Fe3O4 Nanoparticles

Magnetite nanoparticles coated with nonylthiourea (NTH) were synthesized and analyzed for the separation and recovery of platinum group metals (PGMs) from diluted aqueous chloride solutions. Physical characterizations of the coated nanoparticles were performed by Transmission Electron Microscopy (TEM), Thermogravimetric Analysis (TGA) and FT‐IR Spectrometry. Separation efficiency of the coated nanoparticles and the equilibrium adsorption isotherm of PGMs were investigated. The maximum adsorption was attained in less than 30 minutes, and the maximum loading capacity of NTH‐coated Fe3O4 nanoparticles for Pt(IV) and Pd(II) was determined to be 10.7 and 8.1 mg g−1, respectively. The recovery of PGMs from the loaded nanoparticles was examined using different eluting solutions, including HNO3, thiourea, and NaClO4.

Guanidinium functionalised silica-based anion exchangers significantly improve the selectivity of platinum group metal recovery from process solutions

Guanidinium-containing silica-based anion exchangers show great potential for the selective extraction of platinum group metals from authentic precious metal refinery solutions. The pH range for selective palladium extraction over Cu and Ni was found to be increased by as much as 2 pH units compared to previously reported (poly)amine-containing ion exchangers without efficiency loss.

Palladium and platinum recovery from bicomponent mixtures using chitosan derivatives

Chitosan has been used as a base material for the preparation of platinum and palladium sorbents. Chitosan derivatives were obtained by glutaraldehyde cross-linking (GA), by poly(ethyleneimine) grafting (PEI), and by thiourea grafting (TDC). These sorbents were tested for the recovery of platinum group metals (PGMs) in batch systems and column systems from bicomponent mixtures at the optimum pH (ca. pH 2). Sorption isotherms were determined in batch systems, considering the impact of the excess of one metal on the sorption of the second. The sorbents have a marked preference for palladium over platinum. In most cases, the total sorption capacity (taking into account both Pd and Pt sorption) was comparable to that of each metal individually, indicating that the metals compete for the same sorption sites, regardless of the type of sorbent. In fixed-bed systems, similar effects were observed, with typical profiles driven by the displacement of platinum by palladium, attributed to the greater affinity of the sorbents for palladium. The sorbents (especially GA and TDC) have a greater selectivity for Pd than for Pt, compared to PEI, which has greater sorption capacities. Metal desorption was tested using several eluants, none of which allowed the complete removal of the metals from loaded sorbent, nor the selective desorption of either. A complete separation of the metals was not obtained, but by combination of sorption and desorption conditions, a concentration of Pd of 10- to 20-fold was achieved.

Metal vapor treatment for enhancing the dissolution of platinum group metals from automotive catalyst scrap

A new process for dissolving platinum group metals (PGMs) from automotive catalyst scrap using metal vapor was proposed. To improve the PGMs dissolution ratio from scraps, vapor of reactive metals (R), such as magnesium (Mg) or calcium (Ca), was reacted with the automotive catalyst scrap in a closed stainless steel vessel at 1173 K for 3 hours. Under these experimental conditions, Mg and Ca vapor was supplied to the entire body of catalyst scrap. After the reactive metal treatment, the specimens were crushed and dissolved in aqua regia at 323 to 333 K for 1 hour. The PGMs dissolution ratios were improved after the reactive metal treatment, and the dissolution ratios reached 88 pct in Pt, 81 pct in Pd, and 72 pct in Rh, while they were 77 pct in Pt, 69 pct in Pd, and 38 pct in Rh without the treatment. Even when the specimens were dissolved in aqua regia without heating, the PGMs dissolution ratios from the catalyst scrap after reactive metal treatment showed high values, 78 pct in Pt, 74 pct in Pd, and 57 pct in Rh at a maximum. These results show that the reactive metal treatment is effective for the recovery of PGMs from automotive catalyst scrap.

Separation and Concentration of Pd, Pt, and Rh from Automotive Catalytic Converters by Combining Two Hollow-Fiber Liquid Membrane Systems

A new system combining two hollow-fiber-supported liquid membranes (HFSLMs) for the separation and concentration of platinum, palladium, and rhodium is presented. The best results were obtained when the feed solution was recirculated through a first module containing Cyanex 471 as the solvating extractant and then the depleted feed solution was recirculated through a second module containing the anion exchanger Aliquat 336 as the carrier. Under these conditions, palladium was selectively recovered in the stripping solution of module I, while platinum was recovered in the receiving phase of module II, and rhodium remained in the feed solution. It was observed that low concentrations of thiocyanate in the feed solution favored the permeability of platinum. This separation scheme was applied to the recovery of platinum-group metals from the leaching solutions of spent automotive pellet-type catalysts. Palladium and platinum were effectively separated and enriched, and only small amounts of aluminum were cotr...

Selective Uptake and Recovery of Palladium by Biopolymer Microcapsules Enclosing Cyanex 302 Extractant

Selective uptake and recovery of platinum group metals are an important subject in the high level liquid waste treatment. An extractant having a strong affinity for palladium, bis(2,4,4-trimethylpentyl) monothiophosphinic acid (Cyanex 302, HA), was enclosed into microcapsules by utilizing highly immobilizing ability of biopolymer (alginate and alginic acid gel polymers). The uptake of Pd2plus, Ru(NO)3+ and Rh3+ for granular microcapsules has been studied by batch and column methods. A relatively large distribution coefficient of Pd2plus, Kd,Pd, of above 104 cm3/g was obtained in the presence of 0.2–0.5 M HNO3 and the separation factors of Pd/Ru and Pd/Rh were estimated to be above 102. The uptake of Pd2+ on microcapsules followed a Langmuir-type uptake isotherm and the maximum uptake capacity was estimated to be 0.72–0.96 mmol/g. These metal cations were chromatographically separated through the column packed with HA-alginate microcapsules.