Red mud from Brazil : thermal behavior and physical properties

The main constituents of red mud produced in Aluminio city (S.P. – Brazil) are iron, aluminium and silicon oxides. It has been determined that the average particle diameter for this red mud is between 0.05 and 0.002mm. It is observed that a decrease in the percentage of smaller particles occurs at temperatures greater than 400°C. This observation corresponds with the thermal analysis and X-ray diffraction (XRD) data, which illustrate the phase transition of goethite to hematite. A 10% mass loss is observed in the thermal analysis patterns due to the hydroxide – oxide phase transitions of iron (primary phase transition) and aluminium (to a lesser extent). The disappearance and appearance of the different phases of iron and aluminium confirms the decomposition reactions proposed by the thermal analysis data. This Brazilian red mud has been classified as mesoporous at all temperatures except between 400 and 500°C where the classification changes to micro/mesoporous.

A study of environmental and management drivers of non-CO2 greenhouse gas emissions in Australian agro-ecosystems

Australian climate, soils and agricultural management practices are significantly different from those of the northern hemisphere nations. Consequently, experimental data on greenhouse gas production from European and North American agricultural soils and its interpretation are unlikely to be directly applicable to Australian systems. A programme of studies of non-CO2 greenhouse gas emissions from agriculture has been established that is designed to reduce uncertainty of non-CO2 greenhouse gas emissions in the Australian National Greenhouse Gas Inventory and provide outputs that will enable better on-farm management practices for reducing non-CO2 greenhouse gas emissions, particularly nitrous oxide. The systems being examined and their locations are irrigated pasture (Kyabram Victoria), irrigated cotton (Narrabri, NSW), irrigated maize (Griffith, NSW), rain-fed wheat (Rutherglen, Victoria) and rain-fed wheat (Cunderdin, WA). The field studies include treatments with and without fertilizer addition, stubble burning versus stubble retention, conventional cultivation versus direct drilling and crop rotation to determine emission factors and treatment possibilities for best management options. The data to date suggest that nitrous oxide emissions from nitrogen fertilizer, applied to irrigated dairy pastures and rain-fed winter wheat, appear much lower than the average of northern hemisphere grain and pasture studies. More variable emissions have been found in studies of irrigated cotton/vetch/wheat rotation and substantially higher emissions from irrigated maize.

Nanostructures for sensors, electronics, energy and environment

Nanoscale science is growing evermore important on a global scale and is widely seen as playing an integral part in the growth of future world economies. The daunting energy crisis we are facing could be solved not only by new and improved ways of getting energy directly from the sun, but also by saving power thanks to advancements in electronics and sensors. New, cheap dye-sensitized and polymer solar cells hold the promise of environmentally friendly and simple production methods, along with mechanical flexibility and low weight, matching the conditions for a widespread deployment of this technology. Cheap sensors based on nanomaterials can make a fundamental contribution to the reduction of greenhouse gas emissions, allowing the creation of large sensor networks to monitor countries and cities, improving our quality of life. Nanowires and nano-platelets of metal oxides are at the forefront of the research to improve sensitivity and reduce the power consumption in gas sensors. Nanoelectronics is the next step in the electronic roadmap, with many devices currently in production already containing components smaller than 100 nm. Molecules and conducting polymers are at the forefront of this research with the goal of reducing component size through the use of cheap and environmentally friendly production methods. This, and the coming steps that will eventually bring the individual circuit element close to the ultimate limit of the atomic level, are expected to deliver better devices with reduced power consumption.

Role of solids in heavy metals build-up on urban road surfaces

Solids are widely identified as a carrier of harmful pollutants in stormwater runoff exerting a significant risk to receiving waters. This paper outlines the findings of an in-depth investigation on heavy metal adsorption to solids surfaces. Pollutant build-up samples collected from sixteen road sites in residential, industrial and commercial land uses were separated into four particle size ranges and analysed for a range of physico-chemical parameters and nine heavy metals including Iron (Fe), Aluminum (Al), Lead (Pb), Zinc (Zn), Cadmium (Cd), Chromium (Cr), Manganese (Mn), Nickel (Ni) and Copper (Cu). High specific surface area (SSA) and total organic carbon (TOC) content in finer particle size ranges was noted, thus confirming strong correlations with heavy metals. Based on their physico-chemical characteristics, two different types of solids originating from traffic and soil sources were identified. Solids generated by traffic were associated with high loads of heavy metals such as Cd and Cr with strong correlation with SSA. This suggested the existence of surface dependent bonds such as cation exchange between heavy metals and solids. In contrast, Fe, Al and Mn which can be attributed to soil inputs showed strong correlation with TOC suggesting strong bonds such as chemsorption. Zn was found to be primarily attached to solids by bonding with the oxides of Fe, Al and Mn. The data analysis also confirmed the predominance of the finer fraction, with 70% of the solids being finer than 150 µm and containing 60% of the heavy metal pollutant load.

Functionalised zinc oxide nanowire gas sensors : enhanced NO2 gas sensor response by chemical modification of nanowire surfaces

Surface coating with an organic self-assembled monolayer (SAM) can enhance surface reactions or the absorption of specific gases and hence improve the response of a metal oxide (MOx) sensor toward particular target gases in the environment. In this study the effect of an adsorbed organic layer on the dynamic response of zinc oxide nanowire gas sensors was investigated. The effect of ZnO surface functionalisation by two different organic molecules, tris(hydroxymethyl)aminomethane (THMA) and dodecanethiol (DT), was studied. The response towards ammonia, nitrous oxide and nitrogen dioxide was investigated for three sensor configurations, namely pure ZnO nanowires, organic-coated ZnO nanowires and ZnO nanowires covered with a sparse layer of organic-coated ZnO nanoparticles. Exposure of the nanowire sensors to the oxidising gas NO2 produced a significant and reproducible response. ZnO and THMA-coated ZnO nanowire sensors both readily detected NO2 down to a concentration in the very low ppm range. Notably, the THMA-coated nanowires consistently displayed a small, enhanced response to NO2 compared to uncoated ZnO nanowire sensors. At the lower concentration levels tested, ZnO nanowire sensors that were coated with THMA-capped ZnO nanoparticles were found to exhibit the greatest enhanced response. ΔR/R was two times greater than that for the as-prepared ZnO nanowire sensors. It is proposed that the ΔR/R enhancement in this case originates from the changes induced in the depletion-layer width of the ZnO nanoparticles that bridge ZnO nanowires resulting from THMA ligand binding to the surface of the particle coating. The heightened response and selectivity to the NO2 target are positive results arising from the coating of these ZnO nanowire sensors with organic-SAM-functionalised ZnO nanoparticles.

Hydrothermal technologies for the production of fuels and chemicals from biomass

Biomass and non-food crop residues are seen as relatively low cost and abundant renewable sources capable of making a large contribution to the world’s future energy and chemicals supply. Signifi cant quantities of ethanol are currently produced from biomass via biochemical processes, but thermochemical conversion processes offer greater potential to utilize the entire biomass source to produce a range of products. This chapter will review thermochemical gasifi cation and pyrolysis methods with a focus on hydrothermal liquefaction processes. Hydrothermal liquefaction is the most energetically advantageous thermochemical biomass conversion process. If the target is to produce sustainable liquid fuels and chemicals and reduce the impact of global warming as a result of carbon dioxide, nitrous oxide, and methane emissions (i.e., protect the natural environment), the use of “green” solvents, biocatalysts and heterogeneous catalysts must be the main R&D initiatives. As the biocrude produced from hydrothermal liquefaction is a complex mixture which is relatively viscous, corrosive, and unstable to oxidation (due to the presence of water and oxygenated compounds), additional upgrading processes are required to produce suitable biofuels and chemicals.

Photoclickable surfaces for profluorescent covalent polymer coatings

The nitrile imine-mediated tetrazole-ene cycloaddition reaction (NITEC) is introduced as a powerful and versatile conjugation tool to covalently ligate macromolecules onto variable (bio)surfaces. The NITEC approach is initiated by UV irradiation and proceeds rapidly at ambient temperature yielding a highly fluorescent linkage. Initially, the formation of block copolymers by the NITEC methodology is studied to evidence its efficacy as a macromolecular conjugation tool. The grafting of polymers onto inorganic (silicon) and bioorganic (cellulose) surfaces is subsequently carried out employing the optimized reaction conditions obtained from the macromolecular ligation experiments and evidenced by surface characterization techniques, including X-ray photoelectron spectroscopy and FT-IR microscopy. In addition, the patterned immobilization of variable polymer chains onto profluorescent cellulose is achieved through a simple masking process during the irradiation. Photoinduced nitrile imine-alkene 1,3-dipolar cycloaddition (NITEC) is employed to covalently bind well-defined polymers onto silicon oxide or cellulose. A diaryl tetrazole-functionalized molecule is grafted via silanization or amidification, respectively. Under UV light, a reactive nitrile imine rapidly forms and reacts with maleimide-functionalized polymers yielding a fluorescent linkage. Via a masking method, polymeric fluorescent patterns are achieved.

Vibrational spectroscopic study of the minerals cavansite and pentagonite Ca(V4+O)Si4O10.4H2O

The bright blue minerals cavansite and pentagonite, a calcium vanadium silicate Ca(V4+O)Si4O10.4H2O, have been studied by UV–Visible, Raman and infrared spectroscopy. Cavansite shows an open porous structure with very small micron sized holes. Strong UV–Visible absorption bands are observed at around 403, 614 and 789 nm for cavansite and pentagonite. The Raman spectrum of cavansite is dominated by an intense band at 981 cm -1 and pentagonite by a band at 971 cm-1 attributed to the stretching vibrations of (SiO3)n units. Cavansite is characterised by two intense bands at 574 and 672 cm-1 whereas pentagonite by a single band at 651 cm-1. The Raman spectrum of cavansite in the hydroxyl stretching region shows bands at 3504, 3546, 3577, 3604 and 3654 cm-1 whereas pentagonite is a single band at 3532 cm_1. These bands are attributed to water coordinated to calcium and vanadium. XPS studies show that bond energy of oxygen in oxides is 530 eV, and in hydroxides -531.5 eV and for water -533.5 eV. XPS studies show a strong peak at 531.5 eV for cavansite, indicating some OH units in the structure of cavansite.

The influence of vegetation and soil type on the speciation of iron in soil water

Soluble organic matter derived from exotic Pinus species has been shown to form stronger complexes with iron (Fe) than that derived from most native Australian species. It has also been proposed that the establishment of exotic Pinus plantations in coastal southeast Queensland may have enhanced the solubility of Fe in soils by increasing the amount of organically complexed Fe, but this remains inconclusive. In this study we test whether the concentration and speciation of Fe in soil water from Pinus plantations differs significantly from soil water from native vegetation areas. Both Fe redox speciation and the interaction between Fe and dissolved organic matter (DOM) were considered; Fe - DOM interaction was assessed using the Stockholm Humic Model. Iron concentrations (mainly Fe 2+) were greatest in the soil waters with the greatest DOM content collected from sandy podosols (Podzols), where they are largely controlled by redox potential. Iron concentrations were small in soil waters from clay and iron oxide-rich soils, in spite of similar redox potentials. This condition is related to stronger sorption on to the reactive clay and iron oxide mineral surfaces in these soils, which reduces the amount of DOM available for electron shuttling and microbial metabolism, restricting reductive dissolution of Fe. Vegetation type had no significant influence on the concentration and speciation of iron in soil waters, although DOM from Pinus sites had greater acidic functional group site densities than DOM from native vegetation sites. This is because Fe is mainly in the ferrous form, even in samples from the relatively well-drained podosols. However, modelling suggests that Pinus DOM can significantly increase the amount of truly dissolved ferric iron remaining in solution in oxic conditions. Therefore, the input of ferrous iron together with Pinus DOM to surface waters may reduce precipitation of hydrous ferric oxides (ferrihydrite) and increase the flux of dissolved Fe out of the catchment. Such inputs of iron are most probably derived from podosols planted with Pinus.

Influence of organic matter in road deposited particulates in heavy metal accumulation and transport

The research study discussed in the paper investigated the influence of organic matter on heavy metal adsorption for different particle size ranges of build-up solids. Samples collected from road surfaces were assessed for organic matter content, mineral composition, particle size distribution and effective cation exchange capacity. It was found that the organic matter plays a key role in >75µm particles in the adsorption of Zinc, Lead, Nickel and Copper, which are generated by traffic activities. Clay forming minerals and metal oxides of Iron, Aluminium and Manganese was found to be important for heavy metal adsorption to <75µm particles. It was also found that heavy metals adsorbed to organic matter are strongly bound to particles and these metal ions will not be bio-available if the chemical quality of the media remains stable.

Poorly characterized phases in C2M carbonaceous chondrites : proposed structures and significance

Poorly characterized phases (PCP's) may constitute up to 30 volume percent of some C2M carbonaceous chondrite matrices [1] and are an important key to an understanding of matrix evolution. PCPs are usually fine-grained (

Proposed structures for poorly characterized phases in C2M carbonaceous chondrite meteorites

Structure and chemistry of poorly characterized phases (PCP). We suggest here that approximately 10 angstrom PCP, a dominant matrix variety, has a structure equivalent to iron-rich tochilinite [6Fe (sub 0.9) S 5(Fe, Mg) (OH) (sub 2) ] which consists of coherently interstratified mackinawite and brucite sheets. approximately 17 angstrom PCP, previously described as an SBB-type mixed-layer structure, is a commensurate intergrowth of serpentine and tochilinite layers. A wide range of cation substitutions is possible within both tochilinite and serpentine-tochilinite structural types. Various forms of PCP observed in carbonaceous chondrites are intergrowths of tochilinite, serpentine, serpentine-tochilinite and/or valleriite-type minerals.--Modified journal abstract.

Grain size distributions of Magneli phases and metallic titanium in chondritic porous interplanetary dust particles

A mineralogical survey of chondritic interplanetary dust particles (IDPs)showed that these micrometeorites differ significantly in form and texture from components of carbonaceous chondrites and contain some mineral assemblages which do not occur in any meteorite class1. Models of chondritic IDP mineral evolution generally ignore the typical (ultra-) fine grain size of consituent minerals which range between 0.002-0.1µm in size2. The chondritic porous (CP) subset of chondritic IDPs is probably debris from short period comets although evidence for a cometary origin is still circumstantial3. If CP IDPs represent dust from regions of the Solar System in which comet accretion occurred, it can be argued that pervasive mineralogical evolution of IDP dust has been arrested due to cryogenic storage in comet nuclei. Thus, preservation in CP IDPs of "unusual meteorite minerals", such as oxides of tin, bismuth and titanium4, should not be dismissed casually. These minerals may contain specific information about processes that occurred in regions of the solar nebula, and early Solar System, which spawned the IDP parent bodies such as comets and C, P and D asteroids6. It is not fully appreciated that the apparent disparity between the mineralogy of CP IDPs and carbonaceous chondrite matrix may also be caused by the choice of electron-beam techniques with different analytical resolution. For example, Mg-Si-Fe distributions of Cl matrix obtained by "defocussed beam" microprobe analyses are displaced towards lower Fe-values when using analytical electron microscope (AEM)data which resolve individual mineral grains of various layer silicates and magnetite in the same matrix6,7. In general, "unusual meteorite minerals" in chondritic IDPs, such as metallic titanium, Tin01-n(Magneli phases) and anatase8 add to the mineral data base of fine-grained Solar System materials and provide constraints on processes that occurred in the early Solar System.