Kinetic Study on the Leaching of Pt, Pd and Rh from Automotive Catalyst Residue by Using Chloride Solutions

Abstract

Recycling platinum group metals (PGMs) from waste and/or secondary resources is becoming quite important due to the limitation of the natural resource deposits of PGMs. Among the processes of PGMs' recycling from secondary resources, the hydrometallurgical method draws extensive concerns, particularly for the selection of leaching solution. The present work evaluated the ability of chloride leaching solutions, i.e. HCl-H 2 O 2 and NaClO-HCl-H 2 O 2 to extract Pt, Pd and Rh from a kinetic point of view. The effect of temperature in the range of 277-307 K and time were also examined under the conditions of À500 mm of particle size and 100 g L À1 of pulp density.The kinetic model (I):was found to be the most suitable to describe the leaching process of Pt, Pd and Rh in the NaClO contained solution. In this model the interface transfer and diffusion across the leached support layer both affect the rate of leaching reaction.fits the kinetic data very well for the dissolution of Pd in the HCl-H 2 O 2 solution, showing that the diffusion across the leached support layer mainly affect the kinetic behaviors and the diffusion coefficient is inversely proportional to leaching time t. The NaClO contained solution and HCl-H 2 O 2 solution leaching of Pt, Pd and Rh are strongly dependent on the leaching temperature. In the case of the NaClO contained solution, the activation energy based on model (I) for Pd, Pt and Rh was 63.5, 59.1 and 77.9 kJ mol À1 , respectively. It is probably because of that the diffusion of NaClO contained solution across the leached support layer was very slow due to the micro-porous structure of the catalyst; and a high activation energy was needed in effect. Regarding to the leaching in the HCl-H 2 O 2 solution, the activation energy for Pd was 13.4 kJ mol À1 on the basis of model (II).

Silicon nitride coating and crucible—effects of using upgraded materials in the casting of multicrystalline silicon ingots

“…The content of trace elements in silicon nitride coating powder before and after treatment with mixtures of HF/HCl in DI-water as determined by LECO (O) and GDMS Untreated HF/HCl 1Á5%/10% HF/HCl 2Á5%/10% HF/HCl 5%/10% respectively. The lifetimes were measured at an injection level of 1Á10 15 and with a low pass optical filter with a cut off frequency of 1000 nm as described above. The values vary from a maximum value of around 7 ms in the ingot solidified in the crucible of normal, photovoltaic grade and with untreated coating to a value of 135 ms in the ingot made with the clean materials.…”

“…3,5 Elements from the crucible and coating will diffuse into the bottom and sides of the ingot while elements having accumulated in the top of the ingot by segregation during the directional solidification will diffuse back into the bulk of the ingot from the top. 3 A method for the cleaning of the nitride powder based on the well known principle of aqueous acid leaching [13][14][15][16][17] was therefore developed. In the leaching solution HF was added to dissolve oxide on the surface of the nitride particles and HCl was added for extraction of metallic impurities as described by other authors.…”

Recovery and Then Individual Separation of Platinum, Palladium, and Rhodium from Spent Car Catalytic Converters Using Hydrometallurgical Technique followed by Successive Precipitation Methods

“…Spent catalytic converters are good candidates for such requirement. Several works have been conducted to recover PGMs from spent catalytic converters using different metallurgical and refining methods through the use of smelting furnaces, hydrogen pretreatment, and/or direct leaching of PGMs [4,[7][8][9]. Several leaching processes have been developed based on the selective dissolution of the honeycomb unit consisting of PGMs after its crushing and milling [10].…”

Electrochemical Dissolution of Platinum and Ruthenium from Membrane Electrode Assemblies of Polymer Electrolyte Fuel Cells

“…In general, recycling Pt from products, such as automotive catalysts, is conducted by using a leaching method with chloride-based solutions, such as oxyacids. [1][2][3] The method is technically reliable and applicable to most products, including PEFCs. 4) However, there are some problems with the leaching method, for example, generation of large quantities of acidic waste and corrosion of the materials by strong acid media.…”