Chemical composition and minerals in pyrite ash of an abandoned sulphuric acid production plant

The extraction of sulphur produces a hematite-rich waste, known as roasted pyrite ash, which contains significant amounts of environmentally sensitive elements in variable concentrations and modes of occurrence. Whilst the mineralogy of roasted pyrite ash associated with iron or copper mining has been studied, as this is the main source of sulphur worldwide, the mineralogy, and more importantly, the characterization of submicron, ultrafine and nanoparticles, in coal-derived roasted pyrite ash remain to be resolved. In this work we provide essential data on the chemical composition and nanomineralogical assemblage of roasted pyrite ash. XRD, HR-TEM and FE-SEM were used to identify a large variety of minerals of anthropogenic origin. These phases result from highly complex chemical reactions occurring during the processing of coal pyrite of southern Brazil for sulphur extraction and further manufacture of sulphuric acid. Iron-rich submicron, ultrafine and nanoparticles within the ash may contain high proportions of toxic elements such as As, Se, U, among others. A number of elements, such as As, Cr, Cu, Co, La, Mn, Ni, Pb, Sb, Se, Sr, Ti, Zn, and Zr, were found to be present in individual nanoparticles and submicron, ultrafine and nanominerals (e.g. oxides, sulphates, clays) in concentrations of up to 5%. The study of nanominerals in roasted pyrite ash from coal rejects is important to develop an understanding on the nature of this by-product, and to assess the interaction between emitted nanominerals, ultra-fine particles, and atmospheric gases, rain or body fluids, and thus to evaluate the environmental and health impacts of pyrite ash materials

Rare Earth Elements and carbon nanotubes in coal mine around spontaneous combustions

Abstract Increasing population growth and rise global energy petition have made congregation the requests of energy generation and safety a major challenge global. In another hand nanogeoscience is commencing to develop a viable remediation approach of attention in coal mine drainage (CMD) around spontaneous coal combustion (SCC). On the ecological context, nanophases (minerals and/or amorphous phases) are more reactive than bulk compounds, a property that powerfully influences the fate of pollutants in topsoils and drainages. In this work petrographic and geochemical investigations of selected CMD sediments were conducted. The substitution of As, Cd, Hg, and Se in pyrite was most apparent in the CMD sediments. The sampled CMD contained carbon nanotube (CNTs) structures and many others C-nanophases. The CNTs contained several elements, including Hg, Pb, F, Cl, and halogens. While CNTs are known to be produced from coal fires of varying ranks, this seems to be the first report of naturally occurring CNTs. This work also denotes the occurrence of historical NPs-locations in near vicinity to all other, as for illustration deposits of C-NPs and non-crystalline compounds appear only nano-meters separately from each other on the contradictory sides of non-altered amorphous phases. In addition, non-conventional sources, including CMD hosting elevated concentrations of Rare Earth Elements and Yttrium (REY), have been explored as attractive secondary sources for elements recovery. Consequently, in this study we investigate CMD from abandoned coal mines in the South America as a potential REY resource. It is suggested that more work is required on CMD and a few research areas are proposed for future research

A three-dimensional nanoscale study in selected coal mine drainage

Sediments from coal mine drainages (CMDs) contain large quantities of suspended pollutants (possibly numerous chemical substances) along with sulfates and hazardous elements (e.g., chromium, zinc, copper, lead) that irreversibly accumulate in the water. As this accumulation can continue for decades after discontinuation of coal extraction, it is necessary to employ multidisciplinary approaches to control the threat in such zones. The quantity of amorphous material in some CMDs was evaluated by X-ray powder diffraction (XRD) using the Rietveld-based SIROQUANT software package. Modern Dual Beam Focused Ion Beam (FIB), field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscope (H-TEM), and energy-dispersive X-ray spectrometer (EDS) were used to evaluate the occurrence and transformation of nanophases (NPs). FIB is used to determine the 3D distribution of different species (internal structure) within individual NPs, whereas EDS is used to observe NP features (e.g., shape, constituent, range, assembly, and form of polymerization). The mineralogy of the sediment from the Brazilian CMDs, including the proportions of quartz, clays, Al–Fe-oxides, and amorphous NPs, appears to be related to the nature of the mineral matter in the relevant coal cleaning rejects (CCRs). The sediments of CMDs from the Brazilian coal area derived at a lower-pH range have different amorphous compositions as compared to those derived at a higher pH range. These special amorphous compositions are shown to be related to several other sediment properties such as particle surface area. The information gleaned in this study will be useful for further geochemical evaluation of CMDs in other parts of the world

Scalar Casimir Effect on a D-dimensional Einstein Static Universe

We compute the renormalised energy momentum tensor of a free scalar field coupled to gravity on an (n+1)-dimensional Einstein Static Universe (ESU), RxS^n, with arbitrary low energy effective operators (up to mass dimension n+1). A generic class of regulators is used, together with the Abel-Plana formula, leading to a manifestly regulator independent result. The general structure of the divergences is analysed to show that all the gravitational couplings (not just the cosmological constant) are renormalised for an arbitrary regulator. Various commonly used methods (damping function, point-splitting, momentum cut-off and zeta function) are shown to, effectively, belong to the given class. The final results depend strongly on the parity of n. A detailed analytical and numerical analysis is performed for the behaviours of the renormalised energy density and a quantity `sigma' which determines if the strong energy condition holds for the `quantum fluid'. We briefly discuss the quantum fluid back-reaction problem, via the higher dimensional Friedmann and Raychaudhuri equations, observe that equilibrium radii exist and unveil the possibility of a `Casimir stabilisation of Einstein Static Universes'.Comment: 37 pages, 15 figures, v2: minor changes in sections 1, 2.5, 3 and 4; version published in CQ

Atmospheric nanocompounds on lanzarote island: vehicular exhaust and igneous geologic formation interactions

Atmosphere contamination management is one of the most important features in pollution risk management. The worldwide rise in tourism increases apprehension about its probable destructive conservation influence on various aspects of global conservation. One of the principal dangers increased by tourism-based modes of travel are nanoparticles (NPs) containing potentially hazardous elements (PHEs) contamination. One example of this is island destination of Lanzarote, in Spain's Canary Islands in which we examined contamination of the local atmosphere, water and soil. Important NPs containing PHEs, (e.g. arsenic, chromium, lead, and mercury), were found in this locale. It is reasonable to assume that this pollution poses an increased environmental danger to the local biome(s). Modes of transport (i.e. by car, airplane, bus) were shown to be an important contributor to this localized contamination as demonstrated by particulate matter (PM) readings collected near the island's airport. If no measures are taken to reduce vehicle and aircraft traffic, the tendency is to increase environmental degradation will continue unabated. As this particular area of Lanzarote is also one of wine production, increased pollution has the potential for negative impacts on the region's economy

Occurrence of carbon nanotubes and implication for the siting of elements in selected anthracites

Petrographic, geochemical, and electron microbeam investigations of selected anthracites and anthracite-rank coaly shales were conducted. The Pennsylvania, Rhode Island, and KwaZu-Natal anthracites show an enrichment in the middle to heavy rare earths (REE) while the Virginia semi-anthracite exhibited a decreasing trend through the light REE, a peak in Gd, and a depletion in the heavy REE. Substitution of As, Hg, and Se in pyrite was most apparent in the Virginia coal. The Pennsylvania, Rhode Island, and KwaZu-Natal anthracites contained spherical carbon nanotube (CNT) structures. The CNTs contained several elements, including Hg, Cd, F, Cl, and Br. While CNTs are known to be produced from coals of varying ranks, this seems to be the first report of naturally occurring CNTs

Nanometric particles of high economic value in coal fire region: Opportunities for social improvement

Spontaneous coal combustion in the La Guajira coals was studied for the presence of carbon nanophases (e.g., carbon nanotubes), occurrence of rare earth elements (REEs) in them, and the probable mechanisms for concentration of these rare compounds. For this purpose, various techniques such as scanning electron microscopy (SEM), Field-emission SEM, transmission electron microscopy (TEM), high-resolution TEM, and focused ion beam (FIB) were used. The development and alteration of the nanoparticles by geo-processes during the early modification periods of coal combustion were explored. Certain types of carbon nanophases and REE compounds may constitute nanominerals and ultra-fine particles accumulated in the coal peat. Assemblages of these nanophases (crystalline and amorphous compounds), predominantly the clay-monazite relationship and its connection to tonsteins in the coal combustion zones in the east region of the coal mines studied in this work, indicate that the coal area was subjected to REE concentration. The carbon nanophases contained several potential hazardous elements (PHEs), including, arsenic, bromine, cadmium, chlorine, fluorine, mercury, and other PHEs. While carbon nanotubes have been known to be produced from spontaneous combustion of coal of varying ranks, the present work is the first report on the naturally occurring REEs and carbon nanophases in the Colombian coal mining area

Casimir energy and a cosmological bounce

We review different computation methods for the renormalised energy momentum tensor of a quantised scalar field in an Einstein Static Universe. For the extensively studied conformally coupled case we check their equivalence; for different couplings we discuss violation of different energy conditions. In particular, there is a family of masses and couplings which violate the weak and strong energy conditions but do not lead to spacelike propagation. Amongst these cases is that of a minimally coupled massless scalar field with no potential. We also point out a particular coupling for which a massless scalar field has vanishing renormalised energy momentum tensor. We discuss the backreaction problem and in particular the possibility that this Casimir energy could both source a short inflationary epoch and avoid the big bang singularity through a bounce.Comment: 13 pages, LaTeX, 8 figure

Fire resistance performance of concrete-PVC panels with polyvinyl chloride (PVC) stay in place (SIP) formwork

Stay-in-place (SIP) formwork is a more-practical alternative to traditional steel or wood formworks due to its improved constructability and durability. The aim of this paper was to study the fire resistance performances of structural and non-structural concrete panels with polyvinyl chloride (PVC) SIP formwork. Three 124.01 in × 110.24 in × 3.15 in panels of PVC SIP formwork were tested and compared to one another. All panels were aged for 28 days, then exposed to the standard fire curve based on the ISO 834:2014 standard, and the temperatures in each panel surface recorded. The results indicate that concrete strength significantly influenced the structural stability and the fire resistance time of the panels (under load), even in this type of panels when exposed to high temperatures. It was found that the PVC encasement enhanced the thermal insulation property, one of the fire resistance performance criteria. Overall, the importance of this alternative formwork is the reduction in the use of forest resources, the raise of awareness of their conservation, and the promotion of their rational use as this a material is friendly to the environment

Radiation from a D-dimensional collision of shock waves: first order perturbation theory

We study the spacetime obtained by superimposing two equal Aichelburg-Sexl shock waves in D dimensions traveling, head-on, in opposite directions. Considering the collision in a boosted frame, one shock becomes stronger than the other, and a perturbative framework to compute the metric in the future of the collision is setup. The geometry is given, in first order perturbation theory, as an integral solution, in terms of initial data on the null surface where the strong shock has support. We then extract the radiation emitted in the collision by using a D-dimensional generalisation of the Landau-Lifschitz pseudo-tensor and compute the percentage of the initial centre of mass energy epsilon emitted as gravitational waves. In D=4 we find epsilon=25.0%, in agreement with the result of D'Eath and Payne. As D increases, this percentage increases monotonically, reaching 40.0% in D=10. Our result is always within the bound obtained from apparent horizons by Penrose, in D=4, yielding 29.3%, and Eardley and Giddings, in D> 4, which also increases monotonically with dimension, reaching 41.2% in D=10. We also present the wave forms and provide a physical interpretation for the observed peaks, in terms of the null generators of the shocks.Comment: 27 pages, 11 figures; v2 some corrections, including D dependent factor in epsilon; matches version accepted in JHE