"Pre-Earthquake" Micro-Structural Effects Induced by Shear Stress on α-Quartz in Laboratory Experiments

This paper presents the results of measurements performed on α-quartz subjected to shear stress in dry conditions, to understand the relationship between the shear intensity and the resulting physical and chemical effects. If a shear stress of intensity higher than 100 MPa is applied continuously to alpha quartz crystals, they will tend to lose their crystallinity, progressively reduce their friction coefficient (Cof) and change into a low-order material, apparently amorphous under X-ray diffraction, but with a structure different from silica glass. Raman and Pair Distribution Function analyses suggested a structure like cristobalite, a silica polymorph well-known for its auxetic behavior, i.e., having a negative Poisson ratio. This elastic parameter pre-eminently controls the friction coefficient of the material and, if it is negative, the Cof lowering. As a result, the increase in low crystallinity cristobalite is sufficientto explain the lowering of the quartz friction coefficient up to values able to contribute, in principle, to the triggering processes of active faults. This allows hypothesizing a slip induction mechanism that does not include the need to have the interposition of layers of hydrated silica, as invoked by many authors, to justify the low friction coefficients that are achieved in shear stress tests on rocks abundant in quartz

Electrochemical and Structural Characterization of Lanthanum-Doped Hydroxyapatite: A Promising Material for Sensing Applications

In the quest to find powerful modifiers of screen-printed electrodes for sensing applications, a set of rare earth-doped Ca10-xREx(PO4)(6)(OH)(2) (RE = La, Nd, Sm, Eu, Dy, and Tm and x = 0.01, 0.02, 0.10, and 0.20) hydroxyapatite (HAp) samples were subjected to an in-depth electrochemical characterization using electrochemical impedance spectroscopy and cyclic and square wave voltammetry. Among all of these, the inorganic phosphates doped with lanthanum proved to be the most reliable, revealing robust analytical performances in terms of sensitivity, repeatability, reproducibility, and reusability, hence paving the way for their exploitation in sensing applications. Structural data on La-doped HAp samples were also provided by using different techniques, including optical microscopy, X-ray diffraction, Rietveld refinement from X-ray data, Fourier transform infrared, and Raman vibrational spectroscopies, to complement the electrochemical characterization

Sustainable recovery of secondary and critical raw materials from classified mining residues using mycorrhizal-assisted phytoextraction

In this work, mycorrhizal-assisted phytoextraction (MAP, Helianthus annuus–arbuscular mycorrhizal fungus Rhizophagus intraradices–Zn-volcanic ashes) was applied for the recovery of secondary and critical raw materials (SRMs and CRMs, respectively) from Joda West (Odisha, India) mine residues, within a novel multidisciplinary management strategy. Mine residues were preliminarily characterized by using advanced analytical techniques, and subsequently mapped, classified and selected using multispectral satellite Sentinel-2A images and cluster analysis. Selected mine residues were treated by MAP at laboratory scale, and the fate of several SRMs (e.g., Zn, Cr, As, Ni, Cu, Ca, Al, K, S, Rb, Fe, Mn) and CRMs (such as Ga, Ti, P, Ba and Sr) was investigated. Bioconcentration factors in shoots (BCS) and roots (BCR) and translocation factors (TF) were: 5.34(P) > BCS > 0.00(Al); 15.0(S) > BCR > 0.038(Ba); 9.28(Rb) > TF > 0.02(Ti). Results were used to predict MAP performance at larger scale, simulating a Vegetable Depuration Module (VDM) containing mine residues (1 m3). Estimated bio-extracting potential (BP) was in the range 2417 g/m3 (K) > BP> 0.14 g/m3 (As), suggesting the eventual subsequent recovery of SRMs and CRMs by hydrometallurgical techniques, with final purification by selective electrodeposition, as a viable and cost-effective option. The results are promising for MAP application at larger scale, within a circular economy-based approach.Fil: Scotti, Adalgisa. Comisión Nacional de Energía Atómica; ArgentinaFil: Stefano, Milia. Consiglio Nazionale delle Ricerche; ItaliaFil: Silvani, Vanesa Analia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; ArgentinaFil: Giovanna, Cappai. Consiglio Nazionale delle Ricerche; ItaliaFil: Guglietta, Daniela. Consiglio Nazionale delle Ricerche; ItaliaFil: Francesca, Trapasso. Consiglio Nazionale delle Ricerche; ItaliaFil: Emanuela, Tempesta. Consiglio Nazionale delle Ricerche; ItaliaFil: Daniele, Passeri. Consiglio Nazionale delle Ricerche; ItaliaFil: Godeas, Alicia Margarita. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; ArgentinaFil: Gomez, Martin. Comisión Nacional de Energía Atómica; ArgentinaFil: Stefano, Ubaldini. Consiglio Nazionale delle Ricerche; Itali

Toward a Multidisciplinary Strategy for the Classification and Reuse of Iron and Manganese Mining Wastes

The aim of this paper is to evaluate an integrated multidisciplinary strategy for the characterization of mining waste, their possible recycling and reuse. The use of Fe-Mn rich wastes in arsenic removal and phosphorus recovery from water and the phytoextraction potential of metals and their possible recovery from biomass are evaluated

Electromagnetic Emissions from Quartz Subjected to Shear Stress: Spectral Signatures and Geophysical Implications

Shear tests on quartz rocks and single quartz crystals have been conducted to understand the possible relationship between the intensity of detectable stress in fault areas and the energy released in the form of electromagnetic waves in the range 30 KHz-1 MHz (LF–MF). For these tests, a new type of piston-cylinder has been developed, instrumented to collect the electromagnetic signals generated by the quartz during shear stress tests and that allows energy measurements on electromagnetic emissions (EMR) to be performed. The data obtained indicate that shear-stressed quartz crystals can generate electromagnetic emissions in the LF–MF range. These emissions represent a tiny fraction of the total energy dissipated in the fracturing process. The spectrum of radio emissions consists of continuous radiation and overlapping peaks. For the first time, a characteristic migration of peak frequencies was observed, proportional to the evolution of the fracturing process. In particular, the continuous recording of the radio emission spectra shows a migration of the peaks toward higher frequencies, as stress continues over time and smaller and larger fractures form. This migration could be used to distinguish possible natural signals emitted by quartz in tectonically active environments from possible signals of other geophysical and possibly anthropogenic origin

Fracture Analysis of α-Quartz Crystals Subjected to Shear Stress

This study assesses the correlations between the intensity of stress undergone by crystals and the morphological characteristics of particles and fracturing products. The effects of the fractures on the microstructure of quartz are also studied. Alpha quartz, subjected to shear stress, is quickly crushed according to a fracturing sequence, with a total fracture length that is correlated to the stress rate. The shear stress generates a sequence of macro and microstructural events, in particular localized melting phenomena, never highlighted before on quartz and the formation of different polymorphs, such as cristobalite and tridymite together with amorphous silica

Improved reuse and storage performances at room temperature of a new environmental-friendly lactate oxidase biosensor made by ambient electrospray immobilization

A new, environmentally friendly lactate oxidase (LOX) based biosensor for lactate detection, with unprecedented reuse and storage capabilities at room temperature, has been manufactured using the ambient electrospray deposition (ESD) technique. This technology allows for an efficient, green and easy ambient soft-landing immobilization of the LOX enzyme on a cheap commercial screen-printed Prussian blue/carbon electrode (PB/C-SPE), employing sustainable chemistry. This study shows how ESD can confer the biosensor the ability to be stored at ambient pressure and temperature for long periods without compromising the enzymatic activity. The fabricated biosensor shows a storage capability for up to 90 days, without any particular care under storage conditions, and a reuse performance for up to 24 measurements on both the electrode just prepared and on a three-months-old electrode. The LOX-based biosensor has been tested for lactate detection in the linear range of 0.1–1 mM with a limit of detection of 0.07 ± 0.02 mM and does not show any memory effects. The absence of an entrapment matrix as well as any additional hazardous chemicals during the immobilization phase makes the process competitive in terms of environmental sustainability and toxicity. Moreover, the application of a new electrospray deposition cycle on the used biosensors makes the biosensors work again with performances comparable to those of freshly made ones. This demonstrates that the technique is excellent for recycling and eliminates the waste of disposable devices

Sustainable recovery of secondary and critical raw materials from classified mining residues using mycorrhizal-assisted phytoextraction

In this work, mycorrhizal-assisted phytoextraction (MAP, Helianthus annuus–arbuscular mycorrhizal fungus Rhizophagus intraradices–Zn-volcanic ashes) was applied for the recovery of secondary and critical raw materials (SRMs and CRMs, respectively) from Joda West (Odisha, India) mine residues, within a novel multidisciplinary management strategy. Mine residues were preliminarily characterized by using advanced analytical techniques, and subsequently mapped, classified and selected using multispectral satellite Sentinel-2A images and cluster analysis. Selected mine residues were treated by MAP at laboratory scale, and the fate of several SRMs (e.g., Zn, Cr, As, Ni, Cu, Ca, Al, K, S, Rb, Fe, Mn) and CRMs (such as Ga, Ti, P, Ba and Sr) was investigated. Bioconcentration factors in shoots (BCS) and roots (BCR) and translocation factors (TF) were: 5.34(P) > BCS > 0.00(Al); 15.0(S) > BCR > 0.038(Ba); 9.28(Rb) > TF > 0.02(Ti). Results were used to predict MAP performance at larger scale, simulating a Vegetable Depuration Module (VDM) containing mine residues (1 m3). Estimated bio-extracting potential (BP) was in the range 2417 g/m3 (K) > BP> 0.14 g/m3 (As), suggesting the eventual subsequent recovery of SRMs and CRMs by hydrometallurgical techniques, with final purification by selective electrodeposition, as a viable and cost-effective option. The results are promising for MAP application at larger scale, within a circular economy-based approach

Electrospray deposition as a smart technique for laccase immobilisation on carbon black-nanomodified screen-printed electrodes

Enzymes immobilisation represents a critical issue in the design of biosensors to achieve standardization as well as suitable analytical performances in terms of sensitivity, selectivity, and stability. In this work electrospray deposition (ESD) has been exploited as a novel technique for the immobilisation of laccase enzyme on carbon black modified screen-printed electrodes. The aim is to fabricate an amperometric biosensor for phenolic compound detection. The electrodes produced by ESD have been analysed by scanning electron microscopy and characterised electrochemically to prove that this immobilisation technique is suited to manufacture high performance biosensors. The results show that the laccase enzyme maintains its activity after undergoing the electrospray ionisation process and deposition and the fabricated biosensor has improved performances in terms of storage (up to 3 months at room temperature) and working (up to 25 measurements on the same electrode) stability. The laccase-based biosensor has been tested for phenolic compound detection, with catechol as target analyte, in the linear range 2.5–50 μM, with 2.0 μM limit of detection, without interference from lead, cadmium, atrazine, and paraoxon, and without matrix effect in drinking, surface, and wastewater

Structural Characterization of Low-Sr-Doped Hydroxyapatite Obtained by Solid-State Synthesis

Strontium-substituted Ca10(PO4)6(OH)2 hydroxyapatite (HAp) powders, with Sr wt% concentrations of 2.5, 5.6 and 10%, were prepared by a solid-state synthesis method. The chemical composition of the samples was accurately evaluated by using inductively coupled plasma (ICP) spectroscopy. The morphology of the samples was analyzed via optical microscopy, while structural characterization was achieved through powder X-ray diffraction (PXRD) and infrared (FTIR) and Raman spectroscopy. The PXRD structural characterization showed the presence of the Sr dopant in the Ca1 structural site for HAp with a lower Sr concentration and in the Ca2 site for the sample with a higher Sr concentration. FTIR and Raman spectra showed slight band shifts and minor modifications of the (PO4) bands with increasing the Sr doping rate