Automotive Catalytic Converters Research Articles

Turbulence generation after a monolith in automotive catalytic converters

This work reports theoretical studies of flow behaviour in a monolith outlet zone for different Reynolds numbers covering laminar and transitional/turbulent flow regimes. Monolith type substrate is the core part of the automotive catalytic converter. Due to computational limitations, most numerical models of the converter represent the monolith as a continuum, averaging the effect of the solid and the open space on the flow. This strategy is useful to study the macro-structure of the flow, however, it does not capture the exact behaviour of an actual honeycomb type structure, especially at its entrance and exit. In this work, which is a continuation of the publication by Cornejo et al. (2018), a series of 3D LES and RANS simulations are performed using different discrete channel geometry to study and quantify the velocity fluctuations of flow leaving a monolith. The results show that above a certain Reynolds number the instability of the flow after the monolith is significant, leading to turbulence generation. The velocity fluctuations are mainly explained by the flow past the outlet of the monolith, and their magnitude is related to the Reynolds number based on the thickness of the walls between channels. An expression for this critical Reynolds number has been designed and verified against numerical simulations. Parametric studies are carried out to illustrate the influence of the Reynolds number on the appearance of flow fluctuations at the outlet zone of the monolith.

Spatial and temporal distribution of platinum, palladium and rhodium in Zagreb air

Platinum (Pt), palladium (Pd) and rhodium (Rh) are most widely used in the production of automotive catalytic converters that serve to reduce toxic emissions from motor vehicles. The aim of this study was to quantitatively determine the levels of platinum, palladium and rhodium in the PM10 and PM2.5 fraction of airborne particle matter and find their spatial and temporal distribution at different polluted areas of the city of Zagreb, Croatia. The method used in this paper included weekly sampling of airborne particle matter on quartz filters, microwave digestion in acid under high pressure and temperature, and analysis by inductively coupled plasma mass spectrometry (ICP MS). The results have shown that the highest mean values at all three sampling stations (North, Center, South) were obtained for palladium (3.856 pg m−3, 5.396 pg m−3, 5.600 pg m−3) and the lowest for rhodium (0.444 pg m−3, 0.643 pg m−3, 0.750 pg m−3). The average mass concentrations of platinum group elements (PGE) in PM10 increased for all three elements in the direction North < Center < South which had to do with the traffic load nearby the monitoring stations. The ratio of measured mass concentrations to all measuring stations was similar to platinum, palladium and rhodium content in automotive catalytic converters. Factor analysis grouped platinum, palladium and rhodium at all of the monitoring stations, and their relation to other metals together with the aforementioned results indicate that their main source of pollution is traffic or precisely automotive catalytic converters. At all three of the monitoring sites, higher values were measured during the colder part of the year. The results of measuring platinum, palladium and rhodium levels in the city of Zagreb are the first results of their kind for this area and will provide insights into the contribution of catalytic converters to the presence of these elements in the environment.

(Invited) Multifunctional Nano-Array Integrated Monolithic Devices: Toward Rational Engineered Nanomaterials Design and Scalable Nanomanufacturing

The scalable three-dimensional (3-D) integration of functional nanostructures into applicable platforms represents a promising technology to meet the ever-increasing demands of fabricating high performance devices featuring cost-effectiveness, structural sophistication and multi-functional enabling. Such an integration process generally involves a diverse array of nanostructural entities (nano-entities) consisting of dissimilar nanoscale building blocks such as nanoparticles, nanowires, and nanofilms made of metals, ceramics, or polymers. Various synthetic strategies and integration methods have enabled the successful assembly of both structurally and functionally tailored nano-arrays into a unique class of monolithic devices. The performance of nano-array based monolithic devices is dictated by a few important factors such as materials substrate selection, nanostructure composition and nano-architecture geometry. Therefore, the rational material selection and nano-entity manipulation during the nano-array integration process, aiming to exploit the advantageous characteristics of nanostructures and their ensembles, are critical steps towards bridging the design of nanostructure integrated monolithic devices with various practical applications. In this talk, we highlight the latest research progress of the two-dimensional (2-D) and 3-D metal and metal oxide based nanostructural integrations into prototype devices and systems applicable with ultrahigh efficiency, good robustness and improved functionality. Selective examples of nano-array integration, scalable nanomanufacturing and representative monolithic devices will be highlighted, including automotive catalytic converters, thermo-catalytic and photo-activated reactors for fuel/chemical production, and sensors, with practical nanotechnology implications ranging from energy, environmental, to chemical and biotechnology areas.

The Role of Oxides in Catalytic CO Oxidation over Rhodium and Palladium

Catalytic CO oxidation is a seemingly simple reaction between CO and O2 molecules, one of the reactions in automotive catalytic converters, and the fruit-fly reaction in model catalysis. Surprisingly, the phase responsible for the catalytic activity is still under debate, despite decades of investigations. We have performed a simple but yet conclusive study of single crystal Rh and Pd model catalysts, resolving this controversy. For Rh, the oxygen-covered metallic surface is more active than the oxide, while for Pd, thin oxide films are at least as active as the metallic surface, but a thicker oxide is less active. Apart from resolving a long-standing debate, our results pinpoint important design principles for oxidation catalysts as to prevent catalytic extinction at high oxygen exposures.

Quantum Chemical Evaluation of Deep Eutectic Solvents for the Extractive Desulfurization of Fuel

Sulfur compounds in fuels are converted to SOx during combustion, poisoning automotive catalytic converters and creating serious environmental concerns (e.g., acid rain). The efficient desulfurization of liquid fuel is thus a critical step toward minimizing SOx emissions and their associated environmental impact. To address this problem, governments worldwide have passed stringent legislation regulating the maximal sulfur levels allowable in fuels. In the petroleum refining industry, the conventional method for removing sulfur from fuel is catalytic hydrodesulfurization which, while highly efficient for removing mercaptans, thioethers, and disulfides, shows limited performance in removing aromatic organosulfur compounds exemplified by dibenzothiophene. To meet these strict environmental targets, innovative strategies beyond hydrodesulfurization for the deep desulfurization of fuel are sought. One key strategy entails the oxidation of refractory organosulfur compounds in liquid fuel, coupled with efficient...

In vitro permeation of palladium powders through intact and damaged human skin

The use of palladium (Pd) has grown in the last decades, commonly used in automotive catalytic converters, jewellery and dental restorations sectors. Both general and working population can be exposed to this metal, which may act as skin sensitizer. This study investigated in vitro palladium powders permeation through excised intact and damaged human skin using the Franz diffusion cell method and the effect of rapid skin decontamination using sodium laureth-sulphate. 1 mL of a 10 min sonicated suspension made of 2.5 g of Pd powder in 50 mL synthetic sweat at pH 4.5 and room temperature was applied to the outer surface of the skin membranes for 24 h. Pd permeation, assessed by ICP-MS, was higher when damaged skin was used (p = 0.03). Final flux permeation values and lag times were 0.02 ± 0.01 μg cm−2 h−1 and 6.00 ± 3.95 h for intact, and 0.10 ± 0.02 μg cm−2 h−1 and 2.05 ± 1.49 h for damaged skin samples, respectively. Damaged skin protocol enhances Pd skin penetration inside dermal layer (p = 0.04), thus making the metal available for systemic uptake. Pd penetration (p = 0.02) and permeation (p = 0.012) through intact skin decreased significantly when a cleaning procedure was applied. This study demonstrates that after skin exposure to Pd powders a small permeation of the metal happen both through intact and damaged skin and that an early decontamination with a common cleanser can significantly decrease the final amount of metal available forsystemic uptake.

Uncovering the 3 D Structure of Combustion‐Synthesized Noble Metal‐Ceria Nanocatalysts

AbstractWith its unique redox properties, ceria is an oxide with a range of applications, including automotive catalytic converters, which consist of platinum‐group metal nanoparticles on ceria‐containing supports. In this work, the 3 D architecture of a ceria‐based material synthesized by the widely employed glycine‐nitrate solution combustion method is revealed for the first time. Together with N2 adsorption volumetry, scanning transmission electron microscopy (STEM) and scanning electron microscopy (SEM), STEM tomography provides a comprehensive picture of the multimodal porous network of a pre‐reduced Pt‐CeO2 catalyst, from the nanometer to the micrometer scale. This material consists of ceria nanocrystallites forming 3 D aggregates and puzzle‐like 2 D walls separating large roundish mesopores and macropores. The small voids between imperfectly assembled crystallites give rise to some microporosity. In addition, it is demonstrated that a significant proportion of platinum nanoparticles (3–4 nm) are not located at the ceria surface following the one‐step synthesis process, about half of them are buried within ceria. This result is valid for another metal (Rh) and another fuel (oxalyl dihydrazide), and has important implications for heterogeneous catalysis.

PGE Production in Southern Africa, Part I: Production and Market Trends

Platinum group elements (PGEs) are an important resource for many applications, such as automotive catalytic converters for vehicles, jewelry, electrical devices and as catalysts in the chemical and petroleum industries. At present, the greatest share of global PGE supply is extracted from the South African Bushveld Complex and from the Zimbabwean Great Dyke. In this context, this article provides a comprehensive summary of detailed mining data between 2010 and 2015 and discusses these in regard to the global PGE market. On the supply side, the data reveal that the production volumes as well as the ore grades fluctuated in recent years, while the mining and processing of economically less favorable Upper Group 2 (UG2) ore increased. The average head grade from 2010 to 2015 was 3.58 g 6E/t. In the long term, the ore grades decreased. On the market side, PGE prices and increasing (primary) production costs can be observed. On the market side, the demand for vehicles is expected to grow globally resulting in an increase in PGE demand. At the same time, secondary production is expected to increase and will eventually compete with primary production. These findings indicate challenging conditions for the Southern African PGE industry.

Recovery of Platinum and Palladium from Scrap Automotive Catalytic Converters

Abstract&#x0D; &#x0D; The hydrometallurgical method was used to platinum and palladium leaching with aqua regia solution (3HCl: HNO3). The leaching experiments were designed to obtain the optimum conditions by using Taguchi method with 16 experiments at three different factors (time, temperature and solid to liquid ratio), and each factor has four different levels. In this study, leaching the powder sample of catalytic converter that contains platinum and palladium was conducted on the basis of the formation of chloro complexes platinum and palladium (PtCl62-, PdCl42-) with different concentrations in the acidic solution. The optimum conditions for leaching process are (time = 120 minutes, temperature = 100°C, and solid to liquid ratio = 1/20).The best efficiency for platinum and palladium leaching at these conditions were 97.58%, 93.23%, respectively. After leaching process at optimum conditions, platinum was firstly precipitated in the form of (NH4)2PtCl6 (ammonium chloroplatinate) by adding (5ml/l) of ammonium chloride (NH4Cl) as a precipitant agent .Then, palladium was precipitated in the form of (NH4)2PdClO3 (palladium ammonium chlorate) by adding (5g/l) of sodium chlorate (NaClO3) as a precipitant agent to the remaining solution after the removal of platinum. The best efficiency for platinum and palladium recovery at optimum leaching conditions were 91.94%, and 98.82%, respectively.&#x0D; &#x0D; Keywords: Aqua regia, catalytic converter, PGMs, Platinum, Palladium, recovery, catalytic converter, 3HCl:HNO3.

Pd model catalysts: Effect of air pulse length during redox aging on Pd redispersion

Nano-sized noble metal particles are an essential component in automotive catalytic converters. However, during customer in-use operation they agglomerate into larger particles and the performance of the catalytic converter is negatively affected. Engine control methods are needed to provide an environment capable of redispersing noble metal catalyst particles while the particle size is still small. In this study, Pd model powder catalysts, supported on three-way catalytic converter washcoat components of ceria-zirconia (Pd/CZO), 4wt% La2O3 stabilized γ-Al2O3 (Pd/Al) and unstabilized γ-Al2O3 (Pd/A) were exposed to redox cycling at 700°C for 16h (to simulate customer in-use operation engine exhaust) either continuously or interrupted with brief air pulses. The two goals of this research were to determine the air pulse length required so that any Pd redispersion gains achieved by air treatment in each 20min redox cycle will be retained by the end of the 16h aging, and to determine if these supports enable rapid Pd redispersion on the time scale of a common ∼10s engine fuel cut. Pd particle size and dispersion measurements were performed with three complimentary techniques of H2 chemisorption, XRD and electron microscopy since not one technique could be used exclusively. Catalyst activity was determined by CO oxidation with the Water Gas Shift (WGS) reaction and Oxygen Storage Capacity (OSC) measurements to probe the contact between the noble metal and support at a given state of catalyst deterioration, and a CO light-off test to confirm trends observed with Pd metal dispersion. We found that air pulses lasting for 1/6min applied to interrupt short redox aging spans enabled Pd redispersion only on the Pd/Al catalysts. Strong metal support interaction on the Pd/CZO catalysts by decoration of the Pd surface with support oxide was suspected to slow Pd redispersion by limiting metal mobility. Support oxides that promote the Pd2+ state may have been required on the Pd catalysts in order to exhibit Pd redispersion. The insight gained from this work could be used to develop engine control and aftertreatment systems that actively intervene and regenerate a catalyst capable of rapid Pd redispersion.

Turbulence Decay Inside the Channels of an Automotive Catalytic Converter Monolith

This paper reports a multi-scale study of the turbulence decay inside of a monolith. It is a well-known fact that the turbulence at the automotive catalytic converters affects the conversion of chemical species, the composition of the exhaust gas, and the performance of the engine significantly. Basically, the flow is highly turbulent before the monolith; nevertheless, it is usually assumed to be fully laminar inside of it. The present work uses numerical simulations at two different scales: a Reynolds-averaged version of the Naiver-Stokes (RANS) model is used to model gas flow inside the whole converter and LES model is applied to study the decay of turbulence inside a single channel. The inflow boundary conditions for LES are taken from the large-scale simulations carried out using RANS. Results of RANS were validated against published experimental data. CFD software ANSYS-Fluent 17.2 was used for RANS and LES simulations. The results for the channels with the highest and the lowest Reynolds number shows that the turbulence intensity decays quickly, but, can remain high for a significant distance, depending on its position and the duty of the converter, the turbulence intensity can remain high through its entire length.

Improvement of the gas sensing response of nanostructured LaCoO3 by the addition of Ag nanoparticles

LaCoO3 decorated with nanoparticles of noble metals has been proposed as catalyst in Suzuki reactions, automotive catalytic converters and gas sensors. In this work, LaCoO3 decorated with silver nanoparticles (AgNPs) was prepared by the solution-polymerization method, using polyvinyl alcohol (PVA) as polymerizing agent. For comparative purposes, LaCoO3 was also synthesized by this method. Calcination at 500°C produced LaCoO3; however, better crystallinity was obtained at 700°C. To attach AgNPs to LaCoO3, a simple wet impregnation process was used. The microstructure of samples displayed interconnected nanoparticles and extensive porosity. Ag-LaCoO3 shows AgNPs with average size of 10nm. Gas sensing characterization performed at 250°C revealed high reproducibility for detecting CO, CO2 and excess O2 (in air). The results obtained from Ag-LaCoO3 exhibit better stability and the quantitative detection of the test gases. In conclusion, surface decoration of LaCoO3 with AgNPs resulted in an effective and low-cost approach to improve the gas sensing properties of LaCoO3. This process can also be used to enhance the gas response of other oxide perovskites.

Simultaneous leaching of Pt, Pd and Rh from automotive catalytic converters in chloride-containing solutions

Dissolution of platinum group metals (PGM; herein Pt, Pd and Rh) in different chloride-based leaching systems from spent auto catalysts was performed. Response surface methodology and a five-level-five-factor central composite design were used to evaluate the effects of 1) temperature, 2) liquid-to-solid ratio, 3) stirring speed, 4) acid concentration and 5) particle size on extraction yield of PGM by aqua regia. Analysis of variance was used to determine the optimum conditions and most significant factors affecting the overall metal extraction. In the optimum conditions, leaching of Pt, Pd and Rh was 91.58%, 93.49% and 60.15%, respectively. The effect of different oxidizing agents on the PGM dissolution in chloride medium was studied comparatively in the following leaching systems: a) aqua regia/sulfuric acid mixture, b) hydrogen peroxide in sulfuric acid (piranha solution), c) sodium hypochlorite and d) copper(II). Dissolution of Rh is increased in both aqua regia and hydrogen peroxide/hydrochloric acid solutions by adding sulfuric acid.

A Multimethod Approach for Investigating Algal Toxicity of Platinum Nanoparticles.

The ecotoxicity of platinum nanoparticles (PtNPs) widely used in for example automotive catalytic converters, is largely unknown. This study employs various characterization techniques and toxicity end points to investigate PtNP toxicity toward the green microalgae Pseudokirchneriella subcapitata and Chlamydomonas reinhardtii. Growth rate inhibition occurred in standard ISO tests (EC50 values of 15-200 mg Pt/L), but also in a double-vial setup, separating cells from PtNPs, thus demonstrating shading as an important artifact for PtNP toxicity. Negligible membrane damage, but substantial oxidative stress was detected at 0.1-80 mg Pt/L in both algal species using flow cytometry. PtNPs caused growth rate inhibition and oxidative stress in P. subcapitata, beyond what was accounted for by dissolved Pt, indicating NP-specific toxicity of PtNPs. Overall, P. subcapitata was found to be more sensitive toward PtNPs and higher body burdens were measured in this species, possibly due to a favored binding of Pt to the polysaccharide-rich cell wall of this algal species. This study highlights the importance of using multimethod approaches in nanoecotoxicological studies to elucidate toxicity mechanisms, influence of NP-interactions with media/organisms, and ultimately to identify artifacts and appropriate end points for NP-ecotoxicity testing.

Influence of Hydrogen Adsorption on Electrodeposition of Platinum from Chloro Complex Solution

Platinum (Pt) is widely used as insoluble and catalytic electrodes for electrolysis, automotive catalytic converters, and fuel cells. We have been investigating hydrogen incorporation in electrodeposited metal films and its influence on crystal structure of metals (1-3). It was reported that large amount of hydrogen (content in atomic ratio: x = H/Pt = 0.1) is incorporated in the Pt films electrodeposited from a solution including dinitrosulfatoplatinate(II) (H2Pt(NO2)2SO4, DNS) as a metal source. In this study, an electrochemical quartz crystal microbalance (EQCM) method (4) is used to examine influence of hydrogen adsorption on the electrodeposition and hydrogen incorporation into deposited films of Pt from a chloro complex solution. The current-potential and mass increase (Pt deposition rate)-potential curves in 0.024 mol dm-3 K2PtCl4solution adjusted at pH of 0.8 with HCl were measured using an EQCM system (Hokuto Denko, HQ-101D and HZ-5000). A quartz electrode coated with Au, an Ag/AgCl electrode, and a Pt wire were used as the working, reference, and counter electrodes, respectively. The hydrogen content of samples was measured by thermal desorption spectroscopy (TDS). Figure 1 shows the current density and mass increase rate versus electrode potential curves for the chloro complex solution. In the first forward potential sweep toward negative potentials of Fig. 1(a), the cathode current and deposition rate of Pt started increasing at +0.3 V vs. Ag/AgCl. Peaks for cathode current and deposition rate appeared at -0.19 V. The current efficiency was 74% at this peak. Then, as the potential was swept to lower potentials, the deposition rate and current efficiency decreased. This decrease in the current efficiency of Pt deposition is caused by hydrogen adsorption. In the return potential sweep (Fig.1 (b)), the cathode current and Pt deposition steeply increased by hydrogen desorption from the Pt surface, and the current efficiency was 113% at the potential of -0.25 V. The hydrogen content of Pt-electrodeposited Au foil (Pt: 1 μm and Au: 20 μm in thickness) increased as the deposition potential of Pt decreased from 0 to -0.3 V, and was much lower than that deposited from the DNS solution. Acknowledgements The present work was partly supported by JSPS KAKENHI (26289276). References N. Fukumuro, M. Yokota, S. Yae, H. Matsuda, Y. Fukai, J. Alloys Compd., 580, S55 (2013). N. Fukumuro, S. Kojima, M. Fujino, Y. Mizuta, T. Maruo, S. Yae, Y. Fukai, J. Alloys Compd., 645, S404 (2015). N. Hisanaga, N. Fukumuro, S. Yae, H. Matsuda, ECS Trans., 50, 77 (2013). T. Hagihara, K. Yaori, K. Iwakura, N, Fukumuro, S. Yae, Electrochim. Acta, 176, 65 (2015). Figure 1

Development of Mn-based perovskite materials: Chemical structure and applications

ABSTRACTIn this article, we summarize current progress on the bulk and surface characteristics of Mn-containing perovskite oxides known for their good catalytic activity in atmospheric pollutant abatement. These materials are emphasized as serious alternatives for noble metal-based catalysts (Pt, Rh, Pd) in many catalytic applications particularly in automotive exhaust catalytic converters, mainly due to their low cost, good thermal stability at high temperature and ease of preparation compared to supported noble metal catalysts. The success of such materials is mainly related to Mn3+ and Mn4+ mixed valence and the resulted point defects formed after incorporation of a large variety of metals with different size and charge in the perovskite structure. These parameters could also affect the Mn reducibility and oxygen species mobility considered as one of the most determining factors in catalytic activity. The effect of perovskite metallic composition on the surface Mn oxidation state and relative cations segregation as well as applications of Mn-containing perovskite oxides as catalysts for several deep oxidation reactions at low and high temperatures are presented. Particular attention is devoted to the solution combustion synthesis for Mn-containing perovskite catalysts due to its time and energy saving characteristics and high surface areas of the obtained products. These advantages open new attractive opportunities for the use of this economic process to prepare supported perovskite oxide catalysts with the aim to better control morphology and stability of both surface catalyst and supports.

A Synthetic Pseudo-Rh: NOx Reduction Activity and Electronic Structure of Pd-Ru Solid-solution Alloy Nanoparticles.

Rh is one of the most important noble metals for industrial applications. A major fraction of Rh is used as a catalyst for emission control in automotive catalytic converters because of its unparalleled activity toward NOx reduction. However, Rh is a rare and extremely expensive element; thus, the development of Rh alternative composed of abundant elements is desirable. Pd and Ru are located at the right and left of Rh in the periodic table, respectively, nevertheless this combination of elements is immiscible in the bulk state. Here, we report a Pd–Ru solid-solution-alloy nanoparticle (PdxRu1-x NP) catalyst exhibiting better NOx reduction activity than Rh. Theoretical calculations show that the electronic structure of Pd0.5Ru0.5 is similar to that of Rh, indicating that Pd0.5Ru0.5 can be regarded as a pseudo-Rh. Pd0.5Ru0.5 exhibits better activity than natural Rh, which implies promising applications not only for exhaust-gas cleaning but also for various chemical reactions.

Recycling of automotive catalytic converters with application of magneto-hydrodynamic pump

Recycling of automotive catalytic converters with application of magneto-hydrodynamic pump

Platinum group element and cerium concentrations in roadside environments in Toronto, Canada.

Platinum (Pt), palladium (Pd) and rhodium (Rh) are accumulating globally in the environment, due to their use as catalysts to control automotive exhaust emissions. While environmental increases in platinum metal concentrations have been well documented for a number of countries, published data for Canada have been missing to date. The aim of this study is to examine the concentrations of Pt, Pd and Rh, as well as Ce, in soils and dust as a function of traffic volume in Toronto, Ontario. Soils and road and underpass dust were collected from two sites with medium and high volumes of traffic. Samples were acid digested and co-precipitated with Hg (for Pd) and Te (for Pt and Rh), prior to measurement using ICP-Q-MS. Palladium occurred at the highest levels in samples, followed by Pt and Rh. Median concentrations for all soil samples were 63 μg Pd/kg, 8.7 μg Pt/kg, 1.7 μg Rh/kg and 41 mg Ce/kg. The results support existing data regarding PGE accumulation trends in urban and roadside environments, due to their use as catalysts in automotive catalytic converters. This study also confirms a shift toward the heavier use of Pd as the catalyst of choice in recent years, as reflected in the higher concentrations measured for this metal relative to Pt and Rh. The results highlight a need to continue monitoring the accumulation of PGE, most notably Pd, in urban environments.

Potential for Conversion of Waste Platinum Group Metals in Road Dust into Biocatalysts for Cracking Heavy Oil

The oil industry increasingly exploits ‘heavy oils’ which are highly viscous and difficult to extract in a ‘clean’ way. Heat and ‘cracking’ catalysts facilitate extraction e.g. by applying the ‘Toe-to-Heel Air Injection’ (THAI) and ‘Catalytic Process In-Situ’ (CAPRI) techniques. Cracking catalysts include palladium. Use of Pd-catalyst is uneconomic but by using palladium deposited on bacterial cells (in combination with other PMs) a waste can be turned into a valuable product. Road dusts contain precious metals (PMs) which arise from automotive catalytic converters. Once washed from roads the PMs are dispersed to the environment. Model r oad dust solutions were produced to simulate acid leaching of road dust to solubilise the PMs. Bacteria cannot directly recover PMs from acidic leachate but by lightly depositing Pd(0) ‘seeds’ enzymatically the resulting ‘bio-Pd’-catalyst accumulates PMs from waste model leachate. The bio-catalyst was assessed in the reduction of heavy oil viscosity compared to a commercial catalyst, achieving this reduction with significantly less coke formation, which was not attributable to the biomass component alone.