Release of Nanoparticles in the Environment and Catalytic Converters Ageing

Abstract

A Three-Way Catalyst (TWC) contains a cordierite ceramic monolith coated with a layer of Al2O3, CexZr1−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 CexZr1−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 AlxCe1−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 CexZr1−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.

Mites as a Potential Path for Ce-Ti Exposure of Amphibians

“…The presence of Zr at concentrations above LGB in the riverbank is relevant since there are no Zr-sources other than traffic in the area. Previous studies have shown the strong correlation of Ce and Zr in road dust collected at high traffic areas (Meza-Figueroa et al, 2021) and the Raman signature of ceria-zirconia particles (Navarro-Espinoza et al, 2021). Even though we did not obtain the total Ce composition of sediments, the UFP composed of Ce-Zr was identified by Raman spectroscopy and supported by the SEM-EDS analysis.…”

“…The elements Zr-Cu-V-Sb-Nb-Y-Fe have been previously described by Navarro-Espinoza et al (2021) as contaminant elements in TWCC that promote the detachment of the refractory washcoat made of Zr-Ce. This process is crucial for the release of UFP to the environment.…”

“…We used a Principal Component Analysis (PCA) to evaluate the chemical differences among sediments collected within the mining area and our study site where amphibians and mites were sampled. PCA has been employed for source apportionment of metals (Shi et al, 2022) and to assess chemical differences between used and new TWCC (Navarro-Espinoza et al, 2021). The suitability of the dataset was evaluated by the Kaiser-Meyer- Olkin (KMO) and Bartlett´s test of sphericity.…”

“…Catalytic converters have exhaustive and non-exhaustive emissions, the latter emissions associated with traffic are released from the catalytic converters, leading to contamination into soils and sediments (Meza-Figueroa et al, 2021). Chemical elements (Zr and Ce) used to manufacture threeway catalytic converters (TWCC) have low crustal abundances making the associated compounds valuable tracers of such sources in the environment (Meza-Figueroa et al, 2021;Navarro-Espinoza et al, 2021). A TWCC contains a honeycomb structure cordierite (2MgO•2Al 2 O 3 •5SiO 2 ) monolith, with a coating made of cerium oxide (CeO 2 or nanoceria) and zirconium oxide (ZrO 2 or zirconia).…”

Catalizadores de tres vías: historia, funcionamiento y ventajas ambientales

“…Adicionalmente, algunos elementos químicos presentes en los aditivos de las gasolinas se pueden incorporar a la superficie catalítica [18]. En algunos casos, las unidades convertidoras se sobrecalientan derritiendo la estructura interna de panal [19]. Por otra parte, el empuje a alta presión del flujo de gases y el golpeteo generado por el mal estado de calles y carreteras puede producir su desintegración, liberando la capa catalizadora a la atmósfera [16].…”