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Our ability to produce and transform engineered materials over the past 150 years is responsible for our high standards of living today, especially in the developed economies. Yet, we must carefully think of the effects our addiction to creating and using materials at this fast rate will have on the future generations. The way we currently make and use materials detrimentally affects the planet Earth, creating many severe environmental problems. It affects the next generations by putting in danger the future of economy, energy, and climate. We are at the point where something must drastically change, and it must change NOW. We must create more sustainable materials alternatives using natural raw materials and inspiration from Nature while making sure not to deplete important resources, i.e. in competition with the food chain supply. We must use less materials, eliminate the use of toxic materials and create a circular materials economy where reuse and recycle are priorities. We must develop sustainable methods for materials recycling and encourage design for disassembly. We must look across the whole materials life cycle from raw resources till end of life and apply thorough life cycle assessments based on reliable and relevant data to quantify sustainability.
The presence of micro- and nanoplastic particles (MNP) in our environment has raised increasing public and political concern. Increasing evidence suggests that humans are exposed to these MNP, mostly via inhalation or ingestion. The EC-Horizon project POLYRISK (https://polyrisk.science) aims to establish an IATA/AOP-based tiered approach to assess human health risks of MNP. In our research, we focus on assessing immunotoxicological effects of MNP.
We have tested a series of primary, secondary, environmentally aged (incubated in River Rine water) and chemically altered MNP for their potential to affect dendritic cells or macrophages. MNP used in this study include primary and weathered PS, secondary PVC, PA, PP (with or without talc) and PE. The secondary PE and PP (w/o talc) particles appeared to have oxidized groups on their surface.
Data shows that MNP can be engulfed by macrophages (PMA-stimulated human THP1 cells) and human blood-derived dendritic cells (DCs). The effects of virgin as well as secondary MNP (0, 10 or 100 μg/ml) on THP1 macrophages were limited to decrease of mitochondrial activity (Alamar blue), increase of cellular leakage (LDH), and stimulation of lysosomal activity. None of these MNP stimulated gene expression of NFκB or release of pro-inflammatory cytokines (IL-6, TNFα, IL-1β). On the other hand, secondary PP and PE with oxidized surface groups did increase NFκB gene expression and release of cytokines by THP1 macrophages. Virgin and weathered PS particles were tested using DCs, and only weathered PS did stimulate DC activity (increased costimulatory molecules CD83, CD86) and as consequence allogeneic T cells. DC activation appeared to result from environmental contaminants.
In conclusion, of all MNPs tested only those that contained active surface groups or environmental components appeared to be immunostimulatory, whereas primary and secondary MNP rather reduced macrophage activity and viability (at relatively high concentrations of 100 μg/ml). Further research is needed to reveal molecular mechanisms and to translate in vitro findings to real-world exposure scenarios.
Atomically dispersed Fe in N-doped carbon (Fe–N–C) catalysts are leading platinum-group-metal-free candidates for the O2 reduction reaction in proton exchange membrane fuel cells (PEMFCs). Zeolitic imidazolate framework (ZIF-8) derived Fe–N–C present the most promising performance; however, they possess a narrow distribution of small micropores, which limits active site accessibility. Here, to induce hierarchical porosity in Fe–N–C, we report a systematic study on MgCl2·6H2O-templated ZIF-8-derived Fe–N–C catalysts for the O2 reduction reaction. MgCl2·6H2O addition induced complete Zn removal, collapse of the ZIF-8 framework, and formation of large micro- and mesopores, with graphene-like structures. N content was markedly reduced, with conversion from pyridinic to pyrrolic N species. Rotating disc electrode tests showed a progressive increase in O2 reduction activity with MgCl2·6H2O, which is strongly correlated (R2 = 0.98) to the formation of large micropores and small mesopores (1–4 nm). This introduces an indirect structure–activity design principle for Fe–N–Cs. The enhanced Fe–N–C porosity also leads to increased degradation rates under accelerated stress test conditions, which we attributed to the oxidation of disordered carbon domains and active Fe loss. This study highlights a key trade-off between porosity-driven O2 reduction activity and durability in Fe–N–C catalysts.
Lead(II) is a toxic pollutant often found in metalcontaminated soils and wastewaters. In acidic aqueous environments, Pb(II) is highly mobile. Chemical treatment strategies of such systems therefore often include neutralization agents and metal sorbents. Since metal solubility and the retention potential of sorbents depend on the redox state of the aqueous system, we tested the efficiency of the naturally occurring redox-sensitive ferrous iron carbonate mineral siderite to remove Pb(II) from acidic aqueous solutions in batch experiments under oxic and anoxic conditions over a total of 1008 h. Siderite dissolution led to an increase in reactive solution pH from 3 to 5.3 and 6.9, while 90 and 100% of the initial aqueous Pb(II) (0.48 × 10−3 mol kg−1) were removed from the oxic and anoxic systems, respectively.
Scanning and transmission electron microscopy, combined with X-ray absorption and photoelectron spectroscopy, indicated that under oxic conditions, Pb(II) was consumed by cerussite precipitation and inner-sphere surface complexation to secondary goethite.
Under anoxic conditions, Pb(II) was removed by the rapid precipitation of cerussite. This efficient siderite dissolution-coupled sequestration of Pb(II) into more stable solid phases demonstrates this potential method for contaminated water Treatment regardless of the redox environment.
