Enhanced release of palladium and platinum from catalytic converter materials exposed to ammonia and chloride bearing solutions

In-syringe low-density solvent dispersive liquid-liquid microextraction of Pd(II) from acidic solutions resulting from hydrometallurgical treatments and quantification by ICP-OES

An in-syringe low-density solvent dispersive liquid-liquid microextraction (IS-LDS-DLLME) is presented for the extraction of palladium from a highly acidic medium before its quantification by inductively coupled plasma optical emission spectroscopy. The extraction solvent was 1-undecanol, and benzil mono-(2-pyridyl) hydrazone was employed as a ligand. Here, no dispersive solvent is needed as the vortex disperses 1-undecanol in the aqueous sample solution. The experimental variables pH, concentration of the ligand, type and quantity of the extraction solvent, vortex time, and addition of NaCl were optimized. The described approach has detection and quantification limits of 0.13 and 0.43 μg L-1, respectively, an enrichment factor of 91, a linear analytical range from 0.4 to 250 μg L-1, and a precision of 1.7-2.0 % (25.0 μg L-1). The approach was used to analyze electronic waste samples and certified reference material.

Release of Nanoparticles in the Environment and Catalytic Converters Ageing

A Three-Way Catalyst (TWC) contains a cordierite ceramic monolith coated with a layer of Al₂O₃, Ce_xZr_1−xO₂ and platinoids mixture. Under standard operation, the platinoid concentration decreases, exposing the remaining washcoat structure. After that particle release stage, the sintering process follows where the crystalline Ce_xZr_1−xO₂ solution is broken and begins to separate into ZrO₂ and CeO₂ phases. ZrO₂ is released to the environment as micro and nanoparticles, while a small amount of CeO₂ generates a new Al_xCe_1−xO₂ composite. The main effect of Ce capture is the growth in the size of the polycrystal structure from 86.13 ± 16.58 nm to 225.35 ± 69.51 nm. Moreover, a transformation of cordierite to mullite was identified by XRD analysis. Raman spectra showed that the oxygen vacancies (Vö) concentration decreased as Ce_xZr_1−xO₂ phases separation occurred_. The SEM-EDS revealed the incorporation of new spurious elements and microfractures favouring the detachment of the TWC support structure. The release of ultrafine particles is a consequence of catalytic devices overusing. The emission of refractory micro to nanocrystals to the atmosphere may represent an emerging public health issue underlining the importance of implementing strict worldwide regulations on regular TWCs replacement.

Analysis of the palladium response relationship of a receiving water body under multiple scenario changes in rainfall-runoff pollution

Urban rainfall-runoff pollution is one of the main reasons for the deterioration of the receiving water quality. In this study, the lower reaches of the Meishe River on Hainan Island, China were adopted as the research area, and palladium (Pd) was selected as the target pollutant. The purpose of this study was to construct an input response model and to examine the Pd response relationship of receiving water bodies under multiple scenario changes of rainfall-runoff pollution combined with scenario analysis methods. The results showed that the mean absolute percent error (MAPE) and relative mean square error (RMSE) of the input response model were within 15%, which demonstrated the reliability of the model when applied to the simulation of the response of Pd in receiving water bodies to rainfall runoff. The dissolved Pd concentration in the receiving water body decreased in the following order: the moderate rain scenario > rainstorm scenario > the heavy rain scenario. The suspended Pd concentration in the receiving water body first increased and then decreased, and its decay rate was closely related to rainfall intensity and duration. Under the heavy rain and rainstorm scenarios, within 20 m downstream from the outfall, the occurrence time of the maximum suspended Pd concentration in the receiving water body was inversely proportional to the distance. The number of previous clear days was inversely proportional to the dissolved Pd concentration in the receiving water body and proportional to the suspended Pd concentration in the receiving water body. Under the short period of previous clear day scenario, the maximum suspended Pd concentration in each section of the receiving water body appeared earlier than that under the moderate and long periods of previous clear day scenarios.

Identification of refractory zirconia from catalytic converters in dust: An emerging pollutant in urban environments

Using catalytic converters is one of the most effective methods to control vehicle emissions. A washcoat of cerium oxide-zirconia (CeO₂-ZrO₂) has been used to enhance the performance of the catalytic converter device. To date, the prevalence of this material in the environment has not been assessed. In this study, we present evidence of the existence of inhalable zirconia in urban dust. Samples of the washcoat, exhaust pipe, topsoil, and road dust were analyzed by X-ray fluorescence, X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, photoluminescence (PL) spectroscopy, and thermally stimulated luminescence (TSL). The results showed a CeO₂-ZrO₂ phase separation after sintering. This causes the emission of ZrO₂, CeO₂, and CeZrO_x particles smaller than 1 μm, which can likely reach the alveolar macrophages in the lungs. The Ce-Zr content in road dust exceeds geogenic levels, and a significant correlation of 0.87 (p < 0.05) reflects a common anthropic source. Chronic exposure to such refractory particles may result in the development of non-occupational respiratory diseases. The inhalable crystalline compounds emitted by vehicles are a significant environmental health hazard, revealing the need for further investigation and assessment of zirconia levels generated by automobiles in urban areas worldwide.

Response of palladium in receiving water bodies to rainfall-runoff

Palladium (Pd) is widely used in automotive catalytic converters to reduce toxic gas emissions. The input of Pd in the rainfall-runoff is an important contributing factor to the accumulation of Pd in receiving water bodies. In this study, the Meishe River in Haikou, Hainan Province, China, was used as the research area, and palladium (Pd) was selected as the target pollutant. This study explored the response of Pd in the receiving water body to rainfall-runoff and to analyze the influencing factors. The results showed that the dissolved Pd concentration in the receiving water body had a corresponding relationship with that in rainfall-runoff. The response of suspended Pd in the receiving water body to rainfall-runoff was closely related to the location of the drainage outlet. Compared with that of suspended Pd, the response of dissolved Pd in the receiving water body to that in the rainfall-runoff was more obvious. Seven meters downstream from the outfall was the most sensitive response distance of dissolved Pd in receiving water bodies to rainfall-runoff, and the response time was approximately 0-10 min. The suspended Pd at 3 m downstream from the outfall also had a certain response to the rainfall-runoff, and the response time was approximately 15-25 min. The response time of the suspended Pd in the receiving water body depended largely on the first flush ability of the runoff. There was a moderately positive correlation between the dissolved Pd and Cl^- in the receiving water body (r = 0.687; p < 0.05). The effects of pH, Eh, and total suspended solids (TSS) on suspended Pd were reduced in the response process of the receiving water body. The synergistic effect of multiple factors increased the uncertainty of the Pd response.