Commercially available mouthguards: Unearthing trace elements for the first time.

The use of mouthguards is advocated by the American Dental Association for orofacial injury prevention and teeth protection. However, the chemical environment in the mouth may cause harmful substances within the mouthguard's polymer material to leach out and be absorbed by the user. Considering this, the present study for the first time analyzed commercially available mouthguards and disclosed the presence of trace elements. Specifically, an analytical method was developed based on closed-vessel microwave-assisted digestion and plasma-based atomic spectrometry for determining toxic trace elements in mouthguard samples. Initially, 75 elements were assessed and, thereafter, quantified cadmium (Cd), copper (Cu) and lead (Pb) in each sample by inductively coupled plasma mass spectrometry (ICP-MS). Method validation was carried out by analyzing a certified reference material of Low-Density Polyethylene, and by addition and recovery experiments. Results for copper were further validated by ICP optical emission spectrometry (ICP-OES). While most samples exhibited elemental levels beneath the method's limit of quantification, Cd, Cu and Pb were detected in four samples. Remarkably, one sample had Cu levels exceeding safe limits by 109 times, highlighting potential toxicity risks. This initial research underscores the need for stricter contamination control in mouthguard materials to minimize potentially health hazards.

How ICP-OES changed the face of trace element analysis: Review of the global application landscape.

The 50th anniversary of Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) will be observed in 2024. ICP-OES was first commercially available in 1974, and since then, it has become one of the most widely used analytical techniques in the world. ICP-OES is a powerful tool for the determination of trace and ultratrace elemental concentrations in a wide variety of samples specifically for multielement analysis. It is used in a wide range of applications, including environmental monitoring, food analysis, and medical diagnostics. This review aims to explore recent applications of ICP-OES in areas such as food analysis, microplastics, materials, dietary supplements, human tissue, and bodily fluids. The utilization of ICP-OES in these fields has ignited the interest of prospective ICP-OES users and inspired current practitioners, as the 50th anniversary approaches, it is of value of providing an updated review. It is important to note that this work does not seek to encompass a comprehensive review of ICP-OES, given the vast number of published results in this field. Undertaking such a comprehensive task would be a daunting challenge. Consequently, an overview of the ICP-OES instrumental technique is provided, followed by a highlighting of recent significant applications in the aforementioned fields.

A novel and greener sequential column leaching approach for the treatment of two different Greek laterites.

Τhe present study investigates, from an environmental protection viewpoint, the efficiency of sequential column leaching of two different Greek laterites, i.e. a limonitic ore from central and a saprolitic ore from northern Greece. First, the most refractory limonitic laterite is leached in the first column for 15 days and the obtained pregnant leach solution (PLS) is further used for the leaching of the easier to treat saprolitic ore in the second column, thus achieving a significantly reduced acid consumption. The main parameters affecting the process efficiency, i.e. acid molarity (1.5 or 3 mol/L H2SO4) and addition of sodium sulfite (Na2SO3) in the leaching solution were studied. The extraction of Ni, Co, Fe, Al, Mg, Mn and Ca was determined by Atomic Absorption Spectroscopy (AAS), while the characterization of the ores and final residues was carried out by X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA/DTA), and Scanning Electron Microscopy/Energy Dispersive X-Ray Spectroscopy (SEM-EDS) analysis. The results confirm the efficiency of the proposed green approach, which with the use of leaching solution containing 1.5 mol/L H2SO4 and 20 g/L Na2SO3 resulted in 73.8 % Ni, 71.6 % Co and 8.4 % Fe extraction after a short period of time (33 days), while the acid consumption, which is a serious environmental concern, was very low and did not exceed 300 kg/t ore. Overall, the proposed process not only improves the efficiency of leaching of different types of laterites for the recovery of both Ni and Co but also reduces the environmental impacts due to the significantly lower acid consumption.

Quantification of trace elements in surgical and KN95 face masks widely used during the SARS-COVID-19 pandemic.

During the current coronavirus disease (COVID-19) pandemic, face masks have been the single most important protective equipment against the threat of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). While masks are worn, both the nose and the mouth of the user come in contact with the mask material, and as the latter mediates the inhaled air and may interfere with the swallowed saliva, it is of paramount importance to assure that the mask is free of toxic substances. As there are currently no studies on the total amount of trace elements in masks, the present study fills the void and investigates 24 surgical and KN95 face masks. Specifically, mask samples were analyzed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to determine the total concentrations of trace elements as well as to assess the possibility that any detected of the elements present could transfer into the human body, based on saliva leaching and breathing experiments. Accordingly, it is reported herein that although most masks analyzed in this study contain trace elements below their corresponding detection limits, a few masks did contain detectable levels of trace elements. In particular, the maximum values that were determined in certain analyzed samples were: Pb (13.33 µg g-1), Cu (410 µg g-1), Zn (56.80 µg g-1), and Sb (90.18 µg g-1). Finally, in the masks that Pb was present, it easily leached out (58% transfer during a 6-h exposure) during the saliva simulation experiments.

Factors affecting co-valorization of fayalitic and ferronickel slags for the production of alkali activated materials.

The first objective of this experimental study is the assessment of the alkali activation potential of two types of fayalitic slags, an as-received one (FS) and the one obtained after plasma treatment (FSP) of the initial FS, for the production of alkali activated materials (AAMs). Furthermore, the second objective is the elucidation of the co-valorization potential of FS and FSP slags when mixed with ferronickel (FeNi) slag (LS). The alkaline activating solution used was a mixture of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). The effect of various operating parameters, such as H2O/Na2O and SiO2/Na2O ratios present in the activating solution, curing temperature, curing period and ageing period on the compressive strength, density, water adsorption, porosity and toxicity of the produced AAMs was explored. The structural integrity of selected AAMs was investigated after firing specimens for 6 h at temperature up to 500 °C, immersion in distilled water and acidic solution or subjection to freeze-thaw cycles for a period of 7 or 30 days. The results of this study show that FS- and FSP-based AAMs acquire compressive strength of 44.8 MPa and 27.2 MPa, respectively. When FS and FSP were mixed with LS at 50:50%wt ratios the compressive strength of the produced specimens increased to 64.3 MPa and 45.8 MPa, respectively. Furthermore, selected AAMs produced after co-valorisation of slags retained sufficient compressive strength after firing at 500 °C, 45-68 MPa, and exhibited very low toxicity. These findings prove the alkali activation potential of fayalitic slags as well as their co-valorization with ferronickel slag for the production of AAMs, an approach which is in line with the principles of zero-waste and circular economy.

Column leaching of low-grade saprolitic laterites and valorization of leaching residues.

Socio-economic data on nickel and cobalt show their importance throughout the entire metal value chain, from mining to end use, disposal and recycling. Thus, the extraction of both metals from primary and secondary raw materials as well as from wastes is currently considered strategically important for the industry and the society. In this paper heap leaching of Greek low-grade saprolitic laterites, with Ni content 0.97%, was investigated. The main parameters studied involved the strength of the H2SO4 solution used (49 and 147gL-1) and the effect of adding sodium sulfite (Na2SO3) in the leaching medium. The pregnant leach solution (PLS) was recycled several times during leaching in order to minimize acid consumption. The experimental results showed that within a period of 25days, and under the optimum conditions (147gL-1 H2SO4 and 20gL-1 Na2SO3), i) Ni and Co extractions were 72.5% and 47.4%, respectively and ii) Fe and Al co-extractions were 8.7% and 31.3%, respectively. Furthermore, valorization of the leaching residues through alkali activation using NaOH and Na2SiO3 and the addition of metakaolin (MK) for the production of inorganic polymers (IPs) was explored. X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, Differential scanning calorimetry (DSC/TG) and Scanning electron microscopy (SEM-EDS) were used to characterize the ore, its leaching residues and the IPs. The IPs produced demonstrated high compressive strength, almost 40MPa and are suitable for a wide range of applications in the construction sector.

Life cycle analysis of pistachio production in Greece.

In the present paper, a life cycle assessment (LCA) study regarding pistachio (Pistacia vera L.) cultivation in Aegina island, Greece, was performed to evaluate the energy use footprint and the associated environmental impacts. In this context, a detailed life cycle inventory was created based on site-survey data and used for a holistic cradle-to-farm gate LCA analysis using the GaBi 6.5 software. The main impact categories assessed were acidification potential (AP), eutrophication potential (EP), global warming potential (GWP), ozone depletion potential (ODP), photochemical ozone creation potential (POCP) and cumulative energy demand (CED). In order to reveal the main environmental concerns pertinent to pistachio production and in turn propose measures for the reduction of environmental and energetic impacts, three scenarios were compared, namely the Baseline scenario (BS) that involves current cultivation practices, the Green Energy (GE) scenario that involves the use of biological fertilizers i.e. compost, and the Waste Utilization (WU) scenario that involves the production of biochar from pistachio and other agricultural wastes and its subsequent soil application to promote carbon sequestration and improve soil quality. Based on the results of this study, the use of compost for fertilization (GE scenario), which results in approximately 9% savings in terms of energy consumption and the five environmental impact categories studied compared to BS scenario, is considered a promising alternative cultivation strategy. Slightly higher savings (10% on average) in terms of the five calculated environmental impact categories, compared to the BS scenario, were indicated when the WU scenario was considered. Regarding energy consumption, the WU scenario results in minor increase, 3%, compared to the BS scenario. Results of uncertainty analysis performed using the Monte Carlo technique and contribution analysis showed that GE and WU scenarios offer reliable and significant eco-profile improvements for pistachio production in the study area compared to the current situation.

Solid phase studies and geochemical modelling of low-cost permeable reactive barriers.

A continuous column experiment was carried out under dynamic flow conditions in order to study the efficiency of low-cost permeable reactive barriers (PRBs) to remove several inorganic contaminants from acidic solutions. A 50:50 w/w waste iron/sand mixture was used as candidate reactive media in order to activate precipitation and promote sorption and reduction-oxidation mechanisms. Solid phase studies of the exhausted reactive products after column shutdown, using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), confirmed that the principal Fe corrosion products identified in the reactive zone are amorphous iron (hydr)oxides (maghemite/magnetite and goethite), intermediate products (sulfate green rust), and amorphous metal sulfides such as amFeS and/or mackinawite. Geochemical modelling of the metal removal processes, including interactions between reactive media, heavy metal ions and sulfates, and interpretation of the ionic profiles was also carried out by using the speciation/mass transfer computer code PHREEQC-2 and the WATEQ4F database. Mineralogical characterization studies as well as geochemical modelling calculations also indicate that the effect of sulfate and silica sand on the efficiency of the reactive zone should be considered carefully during design and operation of low-cost field PRBs.