Comparative analysis of coal fatalities in Australia, South Africa, India, China and USA, 2006-2010

Coal mining (especially underground) is considered one of the most hazardous industries, and as a result considerable focus is applied to eliminating or mitigating hazards through careful mine planning, equipment selection and certification, and development of management systems and procedures. Regulatory agencies have developed in-house methods for reporting, classification and tracking of fatalities and other incidents according to the type of event, often including consideration of different hazard types. Unfortunately, direct comparison of mining safety statistics between countries is confounded by considerable differences in the way that individual countries classify specific fatalities or incidents. This paper presents a comparative analysis of coal mining fatality data in Australia, South Africa, India, China and the United States from 2006 to 2010. Individual classification definitions are compared between the five countries, and methods presented to normalise each country’s hazard definitions and reporting regimes around the RISKGATE framework of seventeen different priority unwanted events (or topics). Fatality data from individual countries is then re-classified according to the different RISKGATE topics, thereby enabling a comparative analysis between all five countries. This paper demonstrates the utility and value of a standard classification approach, and submits the RISKGATE framework as a model for classification that could be applied globally in coal mining. RISKGATE is the largest health and safety project ever funded by the Australian coal industry (http://www.riskgate.org) to build an industry body of knowledge to assist in managing common industry hazards. A comprehensive knowledge base has been captured for risk management of tyres, collisions, fires, isolation, strata underground, ground control open cut, explosions, explosives, manual tasks and slips/trips/falls. This has been extended to outburst, coal burst and bumps, interface displays and controls, tailings dams and inrush

Green synthesis and photocatalytic properties of manganese-based oxides

In recent years, manganese-based oxides, particularly calcium manganese oxides, have attracted significant interest as a new class of bio-mimetic catalysts, due to their elemental and structural similarity to the natural photocatalytic centre in plant cells. In natural photosynthesis, bio-electricity decomposes water into hydrogen and oxygen within a unique catalytic centre composed of a CaMn4O5 cluster, in the oxygen evolving complex (OEC) enzyme hidden in the Photosystem II protein. Inspired by this nature's solar technology, calcium manganese oxides have been explored as photo catalysts in sustainability-related application including the generation of clean hydrogen fuel through water splitting. For this application, calcium manganese oxides have some unique advantages over other common photocatalysts, (i) bang gap energy allowing the absorption of visible light to utilise a wide range of solar spectrum, and (ii) constitution of low cost, Earth abundant and environment friendly elements. The combination of these unique properties makes calcium manganese oxides a suitable choice as a photocatalyst for a large-scale operation in an eco-friendly manner. However, there are still considerable research gaps in the catalytic applications of calcium manganese oxides. For example, investigation into the catalysis of calcium manganese oxides has been carried out mostly without light irradiation and there is little knowledge about how and which calcium manganese oxides behave as a photocatalyst or as an electrode material in photo-electrochemical cells. Furthermore, information critical to these light-driven applications, such as band edge position and bandgap energy, is still lacking for calcium manganese oxides. Moreover, the relationship between catalytic performance under light and different structural parameters such as manganese oxidation states, structural similarity to the natural OEC cluster, and morphology of the catalyst, is not fully understood. Also, the role of calcium in the catalysis is not known. There is also a strong need to develop new techniques to synthesise nanoscale catalysts that have less environmental impacts than conventional solvent-based methods. In this study, a solvent-free method to synthesize manganese-based oxide catalysts was developed. MnO2, Ca2Mn3O8, CaMn2O4 and CaMnO3 ultrafine particles were successfully synthesized in two steps; mechanochemical processing and subsequent heat treatment. The study of band-edge position and bandgap energy revealed that theoretically the selected manganese-based oxide catalysts can absorb the visible solar spectrum, degrade organic pollutants by free-radical generation, and generate oxygen through photo-electro-catalytic water splitting. However, experimentally, at pH 7, manganese oxides and calcium manganese oxides showed poor charge transfer efficiency, leading to poor photo-catalytic dye degradation. For the study of photo-electrochemical water splitting, polypyrrole, a conducting polymer, was used along with catalyst powders in the anode of a photo-electrochemical cell, to increase charge separation efficiency. This study also identified that oxygen evolution catalysis by CaMn2O4 is affected more by surface area than particle morphology. This work has added new knowledge into the research field of bio-inspired photocatalysts. In this work, potentially green and scalable techniques to produce manganese-based oxide catalysts were developed. The photocatalytic performance of manganese-based oxides in dye decolourisation were investigated under various conditions. Their catalytic and photocatalytic water oxidation performance was investigated using a photo-electrochemical cell and the effects of particle morphology, manages oxidation states and crystal structures on the water splitting reaction were elucidated. These findings will be helpful in designing sustainable technologies for the environment

Photo-Electrochemical Oxygen Evolution Reaction by Biomimetic CaMn2O4 Catalyst

Calcium manganese oxide catalysts are a new class of redox catalysts with significant importance because of their structural similarity to natural oxygen-evolving complex in plant cells and the earth-abundant elemental constituents. In the present study, the photo-electrocatalytic properties of CaMn2O4 in water-splitting were investigated. CaMn2O4 powders with irregular shapes and nanowire shapes were synthesised using mechanochemical processing and a hydrothermal method, respectively. The anode in a photo-electrochemical cell was fabricated by embedding CaMn2O4 powders within polypyrrole. The results showed that CaMn2O4 induced a higher dark and light current in comparison to the control sample (polypyrrole alone). CaMn2O4 nanowires exhibited higher dark and light current in comparison to irregular-shaped CaMn2O4 powders. The difference was attributable to the higher surface area of nanowires compared to the irregular-shaped particles, rather than the difference in exposed crystal facets

Comparative evaluation of the structural and other features governing photo-electrochemical oxygen evolution by Ca/Mn oxides

Mn-Based oxides, particularly CaMn oxides, have recently attracted significant practical interest as a new class of catalyst due to their elemental and structural similarity to the natural oxygen evolving cluster (OEC) in photosynthetic plant cells. However, their performance as oxygen-generating anodes in photoelectrochemical cells has not been studied in detail. In this work, ultra-fine particles of amorphous MnO2, crystalline MnO2 nanorods, Ca2Mn3O8, CaMn2O4 and CaMnO3 were synthesised using a green and scalable mechanochemical method. The particles were comparatively studied as water oxidation photocatalysts in a photo-electrochemical cell at near-neutral pH. The oxides were immobilized on the anode surface using an organic, conducting polymer that facilitated electron exchange and catalytic turnover in a manner similar to redox-active tyrosine in the OEC. The differences in their photocatalytic performances were evaluated in terms of: (1) structural similarities to the natural OEC, (2) Mn oxidation state, (3) crystal structure, (4) specific surface area, (5) electron energy state, and (6) the presence/absence of Ca. The results confirmed the importance of having a local structure that is as similar as possible to the natural OEC cluster, including the presence of Ca. However, it also indicated that it is simplistic to focus only on this feature. The other factors listed above may also play a critical role in performance. Future design of biomimetic catalysts for solar fuel production needs to consider and concurrently optimize all of the relevant influences

Solvent free mechanochemical synthesis of MnO₂ for the efficient degradation of Rhodamine-B

MnO₂ nanorods were synthesized by mechanochemical processing with subsequent heat treatment and their photocatalytic activity was studied on the decolourization of aqueous solution of Rhodamine B at different pH levels. A solid state redox reaction 2KMnO₄ + MnCl₂ → 3MnO₂ + 2KCl + O₂ was activated during mechanical milling. Excess KCl salt was added in the starting powder mixture to prevent agglomeration of MnO₂ nanoparticles. The milling resulted in the production of amorphous MnO₂ nanoparticles with a high surface area of 204 m² g⁻¹. Crystalline MnO₂ nanorods of diameters about 15–20 nm were produced by heating the as-milled powder at 350 °C for 1 h in air. Amorphous MnO₂ nanoparticles showed higher degradation rate of Rhodamine B than crystalline MnO₂ nanorods under simulated sunlight. The degradation rate was higher under acidic conditions. This work demonstrates the potential for cost effective, green and scalable synthesis of MnO₂ nano-catalysts for environmental applications.Ankita Gagrani acknowledges the Ph.D. research fellowship from the Australian National University. Access to the facilities of the Centre for Advanced Microscopy (CAM) with funding through the Australian Microscopy and Microanalysis Research Facility (AMMRF) is gratefully acknowledged

Photo-Electrochemical Oxygen Evolution Reaction by Biomimetic CaMn₂O₄ Catalyst

Calcium manganese oxide catalysts are a new class of redox catalysts with significant importance because of their structural similarity to natural oxygen-evolving complex in plant cells and the earth-abundant elemental constituents. In the present study, the photo-electrocatalytic properties of CaMn2O4 in water-splitting were investigated. CaMn2O4 powders with irregular shapes and nanowire shapes were synthesised using mechanochemical processing and a hydrothermal method, respectively. The anode in a photo-electrochemical cell was fabricated by embedding CaMn2O4 powders within polypyrrole. The results showed that CaMn2O4 induced a higher dark and light current in comparison to the control sample (polypyrrole alone). CaMn2O4 nanowires exhibited higher dark and light current in comparison to irregular-shaped CaMn2O4 powders. The difference was attributable to the higher surface area of nanowires compared to the irregular-shaped particles, rather than the difference in exposed crystal facets

Photo-Electrochemical Oxygen Evolution Reaction by Biomimetic CaMn2O4 Catalyst

Calcium manganese oxide catalysts are a new class of redox catalysts with significant importance because of their structural similarity to natural oxygen-evolving complex in plant cells and the earth-abundant elemental constituents. In the present study, the photo-electrocatalytic properties of CaMn2O4 in water-splitting were investigated. CaMn2O4 powders with irregular shapes and nanowire shapes were synthesised using mechanochemical processing and a hydrothermal method, respectively. The anode in a photo-electrochemical cell was fabricated by embedding CaMn2O4 powders within polypyrrole. The results showed that CaMn2O4 induced a higher dark and light current in comparison to the control sample (polypyrrole alone). CaMn2O4 nanowires exhibited higher dark and light current in comparison to irregular-shaped CaMn2O4 powders. The difference was attributable to the higher surface area of nanowires compared to the irregular-shaped particles, rather than the difference in exposed crystal facets

Multiwavelength Single Nanowire InGaAs/InP Quantum Well Light-Emitting Diodes

We report multiwavelength single InGaAs/InP quantum well nanowire light-emitting diodes grown by metal organic chemical vapor deposition using selective area epitaxy technique and reveal the complex origins of their electroluminescence properties. We observe that the single InGaAs/InP quantum well embedded in the nanowire consists of three components with different chemical compositions, axial quantum well, ring quantum well, and radial quantum well, leading to the electroluminescence emission with multiple wavelengths. The electroluminescence measurements show a strong dependence on current injection levels as well as temperatures and these are explained by interpreting the equivalent circuits in a minimized area of the device. It is also found that the electroluminescence properties are closely related to the distinctive triangular morphology with an inclined facet of the quantum well nanowire. Our study provides important new insights for further design, growth, and fabrication of high-performance quantum well-based nanowire light sources for a wide range of future optoelectronic and photonic applications