A long-term study on structural changes in calcium aluminate silicate hydrates.

Production of blended cements in which Portland cement is combined with supplementary cementitious materials (SCM) is an effective strategy for reducing the CO2 emissions during cement manufacturing and achieving sustainable concrete production. However, the high Al2O3 and SiO2 contents of SCM change the chemical composition of the main hydration product, calcium aluminate silicate hydrate (C-A-S-H). Herein, spectroscopic and structural data for C-A-S-H gels are reported in a large range of equilibration times from 3 months up to 2 years and Al/Si molar ratios from 0.001 to 0.2. The 27Al MAS NMR spectroscopy and thermogravimetric analysis indicate that in addition to the C-A-S-H phase, secondary phases such as strätlingite, katoite, Al(OH)3 and calcium aluminate hydrate are present at Al/Si ≥ 0.03 limiting the uptake of Al in C-A-S-H. More secondary phases are present at higher Al concentrations; their content decreases with equilibration time while more Al is taken up in the C-A-S-H phase. At low Al contents, Al concentrations decrease strongly with time indicating a slow equilibration, in contrast to high Al contents where a clear change in Al concentrations over time was not observed indicating that the equilibrium has been reached faster. The 27Al NMR studies show that tetrahedrally coordinated Al is incorporated in C-A-S-H and its amount increases with the amount of Al present in the solution. Supplementary Information: The online version contains supplementary material available at 10.1617/s11527-022-02080-x.

Real-Time Detection of Aerosol Metals Using Online Extractive Electrospray Ionization Mass Spectrometry.

Metal emissions are of major environmental and practical concern because of their highly toxic effects on human health and ecosystems. Current technologies available in the market for their detection are typically limited by a time resolution of 1 h or longer (e.g., via semicontinuous X-ray fluorescence measurements) or are nonquantitative (e.g., laser ablation mass spectrometry). In this work, we report the development of a novel technique for the real-time detection and monitoring of metal particles in situ using an extractive electrospray ionization (EESI) source coupled to a high-resolution time-of-flight mass spectrometer (TOF-MS). The experiments were conducted in negative ionization mode using disodium ethylenediamine tetraacetic acid (EDTA) dihydrate to chelate with metals and form stable metal complexes. Results for water-soluble metal compounds were obtained. The following representative metal ions were examined: Pb, Cd, Zn, Ce (III), Ba, Ni, Fe(II), Fe(III), Cu(II), Cr, Mo, Co(II), Mg, Nd, Li, Ti, Ca, Cs, Ag, Tm, Er(III), La(III), Yb(III), Eu(III), Pr(III), Gd(III), Lu(III), Dy(III), Tb(III), Ho, and Ru(III). The results showed a very good linear mass response (R2 = 0.9983), low ng/m3 limits of detection (LoD), and a fast response time (1 s). The stability and repeatability of the developed EESI-TOF-MS were tested under complex dynamic and periodic experimental conditions, and negligible matrix effects were measured for internally and externally mixed metal particles. Benchmark testing against inductively coupled plasma-mass spectrometry (ICP-MS) was also performed, highlighting the online measurement capabilities of aerosol metals with a LoD lower than those of ICP-MS. Proof-of-concept ambient measurements were performed in New Delhi, India, and very promising results were obtained, allowing further exploitation elsewhere.

Evaporation of Metals during the Thermal Treatment of Oxide Nanomaterials in Cellulose-Based Matrices.

Like conventional material products, waste is the last stage of the life cycle of engineered nanomaterials, which are then incinerated or stabilized before disposal. However, because of their special physical characteristics, the fate of the thermally treated nanomaterials may differ or not from the conventional ones. In this study the thermal release of metals from three nanomaterials, namely CuO, ZnO, and TiO2, embedded in matrices containing organic and inorganic compounds was investigated by using an in-house developed setup. The latter, which combines a TGA (Thermogravimetric Analyzer) and an ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometer), offers the possibility to gain simultaneously thermogravimetric and elemental information. It is shown that the matrix composition, such as chlorine and silicon, plays a key role in the evaporation of Cu and Zn at temperatures above 700 °C, while at relatively low temperatures (250 to 450 °C) the nanomaterials are most probably entrained in the flue gas independently of their chemical properties. Incineration experiments using a tubular furnace and subsequent ICP-MS (ICP Mass Spectrometry) analysis of the obtained residues allowed for quantification of the metal evaporation from the three nanomaterials.

Emissions of Secondary Formed ZnO Nano-Objects from the Combustion of Impregnated Wood. An Online Size-Resolved Elemental Investigation.

The release of secondary nano-objects formed during waste combustion processes is becoming a matter of concern, considering their known toxicity and the fact that the 100% efficiency of filtering systems is not always ensured. An increased cytotoxicity and genotoxicity on human peripheral blood lymphocytes is known particularly in the case of ZnO, which is often contained in paints and waterproof agents, heading to a relevant quantity present in the waste wood material. In this study, the behavior of ZnO nanoparticles during wood combustion and the effect of the reduction potential of generated carbon species on the release of secondarily formed ZnO-containing nano-objects were investigated. By hyphenating a modified scanning mobility particle sizer (SMPS) and inductively coupled mass spectrometry (ICP-MS), it was possible to obtain simultaneously size-resolved and chemical information on the emitted nanoparticles. Through the established correlation between SMPS and ICP-MS signals, Zn-containing particles were efficiently resolved from the combustion generated particles. Transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS) on size-selected particles confirmed the SMPS and ICP-MS data. The use of electron diffraction allowed determining the structure of the crystalline materials as hexagonal ZnO. A possible mechanism of reduction of ZnO to Zn and further reformation as secondary nano-objects is proposed.

Investigating active phase loss from supported ruthenium catalysts during supercritical water gasification.

Active phase loss mechanisms from Ru/AC catalysts were studied in continuous supercritical water gasification (SCWG) for the first time by analysing the Ru content in process water with low limit-of-detection time-resolved ICP-MS. Ru loss was investigated alongside the activity of commercial and in-house Ru-based catalysts, showing very low Ru loss rates compared to Ru/metal-oxides (0.2-1.2 vs. 10-24 µg gRu -1 h-1, respectively). Furthermore, AC-supported Ru catalysts showed superior long-term SCWG activity to their oxide-based analogues. The impact on Ru loss of several parameters relevant for catalytic SCWG (temperature, feed concentration or feed rate) was also studied and was shown to have no effect on the Ru concentration in the process water, as it systematically stabilised to 0.01-0.2 µgRu L-1 for Ru/AC. Looking into the type of Ru loss in steady-state operation, time-resolved ICP-MS confirmed a high probability of finding Ru in the ionic form, suggesting that leaching is the main steady-state Ru loss mechanism. In non-steady-state operation, abrupt changes in the pressure and flow rate induced important Ru losses, which were assigned to catalyst fragments. This is directly linked to irreversible mechanical damage to the catalyst. Taking the different observations into consideration, the following Ru loss mechanisms are suggested: 1) constant Ru dissolution (leaching) until solubility equilibrium is reached; 2) minor nanoparticle uncoupling from the support (both at steady state); 3) support disintegration leading to the loss of larger amounts of Ru in the form of catalyst fragments (abrupt feed rate or pressure variations). The very low Ru concentrations detected in process water at steady state (0.01-0.2 µgRu L-1) are close to the thermodynamic equilibrium and indicated that leaching did not contribute to Ru/AC deactivation in SCWG.

Elemental and Thermo-gravimetric Characterization of Trace Metals in Leaves and Soils as Bioindicators of Pollution in Kyiv City.

In this study, leaf and soil samples were used as bio-monitors for different alkali and heavy metals at six different locations in Kyiv city. Using x-y plots of the inductively coupled plasma optical emission spectroscopy (ICP-OES) data measured the discrepancy level in elemental composition between the different investigated areas; the correlation between the concentrations in tree leaves and the samples from the surrounding soils were investigated. While the concentration of essential mineral elements and metals was found to be similar in several leaf and soil samples, in other samples, their concentration spread up to more than one order of magnitude. The concentration of metals was found to be higher in soil samples than in leaves. Thermo-gravimetric analysis (TGA) data helped to further characterize both types of samples. The metal removal during the incineration of the leaves was investigated by coupling a thermo-gravimetric analyzer to an inductively coupled plasma optical emission spectrometer (TGA-ICP-OES). The release of Cd, K, Na, Pb, and Zn during incineration at temperatures up to 960 °C was online monitored, and some insights were drawn about the behavior of such metals and the chemistry involved in the volatilization process.

Cross-Talk-Suppressing Electrolyte Additive Enabling High Voltage Performance of Ni-Rich Layered Oxides in Li-Ion Batteries.

Control of electrode-electrolyte interfacial reactivity at high-voltage is a key to successfully obtain high-energy-density lithium-ion batteries. In this study, 2-aminoethyldiphenyl borate (AEDB) is investigated as a multifunctional electrolyte additive in stabilizing surface and bulk of both Ni-rich LiNi0.85 Co0.1 Mn0.05 O2 (NCM851005) and graphite electrodes in a cell operated with elevated upper cutoff voltage of 4.4 V vs. Li+ /Li. The presence of AEDB in a full-cell inhibits structural degradation of both cathode and anode materials, suppressing crack formation, and reduces metal dissolution at the cathode and metal deposition at the anode. As a consequence, the interfacial resistance is significantly reduced. Moreover, this is a case where "the whole is greater than the sum of the parts": the effect of AEDB in half-cells is rather modest, whereas in full-cells its addition results in tremendous performance improvement. The graphite‖NCM851005 full-cell in the presence of AEDB has a capacity retention of 88 % after 100 cycles, even when the upper cutoff voltage is set to 4.35 V, corresponding to 4.4 V vs Li+ /Li, whereas with standard electrolyte under the same conditions it is only 21 %. The study shows a simple and easy approach to using Ni-rich cathodes in an extended voltage window and demonstrates the importance of full-cell testing for electrolyte additive selection.

The effect of sodium hydroxide on Al uptake by calcium silicate hydrates (CSH).

To reduce the CO2 emissions from cement production, Portland cement (PC) is partially replaced by supplementary cementitious materials (SCM). Reactions of SCM with PC during hydration leads to the formation of CSH with more silicon and aluminum than in PC, which affects the stability and durability of such concrete. Therefore, it is crucial to determine the role of aluminum on CSH properties to predict the formed hydrate phase assemblages and their effects on durability. Aluminum sorption isotherms including very low Al concentrations have been determined for CSH with Ca/Si ratios from 0.6 to 1.4. Elemental measurements were performed with ICP-MS and ICP-OES. The presence of secondary phases was investigated by using thermogravimetric analysis and XRD. Higher dissolved concentrations of Al were observed at increased alkali hydroxide concentrations and thus higher pH values. High alkali hydroxide led to an increased Al(OH)4- formation, which reduced the Al uptake in CSH. This comparable behavior of Al and Si towards changes in pH values, points toward the uptake of aluminum within the silica chain both at low and high Ca/Si ratios. A higher Al uptake in CSH was observed at higher Ca/Si ratios, which indicates a stabilizing effect of calcium in the interlayer on Al uptake.

Siloxane compounds in biogas from manure and mixed organic waste: Method development and speciation analysis with GC-ICP-MS.

A novel method for the determination of linear and cyclic siloxane compounds (L2, L3, D3, D4, D5, and D6) in biogas was developed by combining gas chromatography (GC) with inductively coupled plasma mass spectrometry (ICP-MS). Using a continuous liquid quench sampling system, biogas samples were collected from a Swiss biogas production plant processing manure and mixed organic wastes. Although significant concentrations of siloxanes are normally linked to biogas from wastewater treatment plants (WWTP) or landfill gas, manure and mixed organic waste samples also showed values in the range of 0.1 mgSi Nm-3, which would be particularly critical for appliances such as solid oxide fuel cells (SOFC). The GC-ICP-MS method showed very good linearity for all the investigated compounds (R2 between 0.999 and 1.000). The limits of detection and quantification (LOD and LOQ) in the gas for cyclic compounds, such as D5, vary based upon the used sampling conditions (approximate range of 0.002-0.004 mgSi Nm-3 and 0.007-0.014 mgSi Nm-3, respectively). To the best of our knowledge, these LOD and LOQ values are by far among the lowest reported in literature and they satisfy the EURAMET (the European Association of National Metrology Institutes) requirements, which fix recommended levels for Si total amounts between 0.1 and 0.3 mgSi Nm-3 for measurement in biogas or bio-methane. The GC-ICP-MS method was evaluated by comparing its performances with a flame ionization detector (FID), operated in parallel with ICP-MS, and with GC-MS (gas chromatography - mass spectrometry). The GC-FID showed higher detection limits and matrix effects than GC-ICP-MS. Nevertheless, it can still be suitable for an initial estimation of the siloxane compounds present in the biogas, at least for samples having relatively high concentration, by following some data treatment optimization. The GC-MS analyses were considered here as a further confirmation of the accuracy of the GC-ICP-MS results.

Metal-organic frameworks as kinetic modulators for branched selectivity in hydroformylation.

Finding heterogeneous catalysts that are superior to homogeneous ones for selective catalytic transformations is a major challenge in catalysis. Here, we show how micropores in metal-organic frameworks (MOFs) push homogeneous catalytic reactions into kinetic regimes inaccessible under standard conditions. Such property allows branched selectivity up to 90% in the Co-catalysed hydroformylation of olefins without directing groups, not achievable with existing catalysts. This finding has a big potential in the production of aldehydes for the fine chemical industry. Monte Carlo and density functional theory simulations combined with kinetic models show that the micropores of MOFs with UMCM-1 and MOF-74 topologies increase the olefins density beyond neat conditions while partially preventing the adsorption of syngas leading to high branched selectivity. The easy experimental protocol and the chemical and structural flexibility of MOFs will attract the interest of the fine chemical industries towards the design of heterogeneous processes with exceptional selectivity.

A Practical Guide on Coupling a Scanning Mobility Sizer and Inductively Coupled Plasma Mass Spectrometer (SMPS-ICPMS).

A large variety of analytical methods are available to characterize particles in aerosols and suspensions. The choice of the appropriate technique depends on the properties to be determined. In many fields information about particle size and chemical composition are of great importance. While in aerosol techniques particle size distributions of gas-borne particles are determined online, their elemental composition is commonly analyzed offline after an appropriate sampling and preparation procedure. To obtain both types of information online and simultaneously, a hyphenated setup was recently developed, including a Scanning Mobility Particle Sizer (SMPS) and an Inductively Coupled Plasma Mass Spectrometer (ICPMS). This allows first to classify the particles with respect to their mobility diameter, and then to determine their number concentration and elemental composition in parallel. A Rotating Disk Diluter (RDD) is used as the introduction system, giving more flexibility regarding the use of different aerosol sources. In this work, a practical guide is provided describing the different steps for establishing this instrumentation, and how to use this analysis tool. The versatility of this hyphenated technique is demonstrated in example measurements on three different aerosols generated out of a) a salt solution, b) a suspension, and c) emitted by a thermal process.

Iron phosphate nanoparticles for food fortification: Biological effects in rats and human cell lines.

Nanotechnology offers new opportunities for providing health benefits in foods. Food fortification with iron phosphate nanoparticles (FePO4 NPs) is a promising new approach to reducing iron deficiency because FePO4 NPs combine high bioavailability with superior sensory performance in difficult to fortify foods. However, their safety remains largely untested. We fed rats for 90 days diets containing FePO4 NPs at doses at which iron sulfate (FeSO4), a commonly used food fortificant, has been shown to induce adverse effects. Feeding did not result in signs of toxicity, including oxidative stress, organ damage, excess iron accumulation in organs or histological changes. These safety data were corroborated by evidence that NPs were taken up by human gastrointestinal cell lines without reducing cell viability or inducing oxidative stress. Our findings suggest FePO4 NPs appear to be as safe for ingestion as FeSO4.