The relation between local structural distortion and the low-temperature magnetic anomaly in Fe7S8.

Structural defects on an atomic level can crucially impact the magnetic properties of a material. We study this phenomenon by means of magnetometry and powder neutron diffraction on a stoichiometric, monoclinic pyrrhotite (Fe7S8), which is a classic omission structure with a magnetic anomaly at about 30 K. The initial structural distortion of the pyrrhotite at 300 K caused by the vacancy arrangement decreases upon cooling, and simultaneous to the magnetic anomaly the anisotropic contraction of the unit cell homogenizes the covalency of the Fe-Fe bonds with lengths less than 3.0 Å and the Fe-S-Fe bond angles. These changes on the atomic level affect the spin-orbit coupling and the super-exchange interactions in Fe7S8, and trigger the low-temperature magnetic anomaly within a crystallographically stable system.

Characterization of indoor dust from Brazil and evaluation of the cytotoxicity in A549 lung cells.

Over the past decade, ambient air particulate matter (PM) has been clearly associated with adverse health effects. In Brazil, small and poor communities are exposed to indoor dust derived from both natural sources, identified as blowing soil dust, and anthropogenic particles from mining activities. This study investigates the physicochemical and mineralogical composition of indoor PM10 dust samples collected in Minas Gerais, Brazil, and evaluates its cytotoxicity and inflammatory potential. The mean PM10 mass concentration was 206 µg/m(3). The high dust concentration in the interior of the residences is strongly related to blowing soil dust. The chemical and mineralogical compositions were determined by ICP-OES and XRD, and the most prominent minerals were clays, Fe-oxide, quartz, feldspars, Al(hydr)oxides, zeolites, and anatase, containing the transition metals Fe, Cr, V, Ni, Cu, Zn, Ti, and Mn as well as the metalloid As. The indoor dust samples presented a low water solubility of about 6 %. In vitro experiments were carried out with human lung alveolar carcinoma cells (A549) to study the toxicological effects. The influence of the PM10 dust samples on cell viability, intracellular formation of reactive oxygen species (ROS), and release of the pro-inflammatory cytokine IL-8 was analysed. The indoor dust showed little effects on alamarBlue reduction indicating unaltered mitochondrial activity. However, significant cell membrane damage, ROS production, and IL-8 release were detected in dependence of dose and time. This study will support the implementation of mitigation actions in the investigated area in Brazil.

Is phosphorus recovery from waste water feasible?

Phosphorus (P) recovery from waste water must become a predominant goal of all countries to face the limited resources of this essential nutrient. The induced crystallisation of calcium phosphates straight from the waste water phase applying tobermorite-rich calcium silicate hydrate compounds (CSH) from the construction industry as the trigger material has proved to be a suitable method. Laboratory and semi-technical scale experiments were carried out in fixed bed, stirred reactor and expanded bed mode. P-loads of the crystallisation substrates of up to 13 wt-% total P (P-tot) (30 wt-% P2O5) were achieved. Recycling options of the generated products, both as substitute for phosphate rock in the phosphate industry and as a new fertiliser in agriculture, were demonstrated. Indicative operating and investment costs were estimated for conversion of conventional waste water treatment plants (WWTP) designed for nutrient removal and P-precipitation with iron and aluminium reagents to the proposed new crystallisation technology for simultaneous P-removal and P-recovery.

Phosphorus removal and recovery from wastewater by tobermorite-seeded crystallisation of calcium phosphate.

Investigations were focused on the development of a technology for phosphorus (P) recovery straight from wastewater. Facing the finiteness of the natural resources of this essential nutrient, the declared goal must be the sustainable use of available phosphorus sinks such as wastewater treatment plants (WWTP) for the generation of P rock substitutes. A feasible method for simultaneous elimination and recovery of phosphorus from wastewater proved to be the P-RoC process - the phosphorus recovery from wastewater by induced crystallisation of calcium phosphate, applying tobermorite-rich waste compounds of the construction industry. The experiments were performed in fixed bed-, stirred- and expanded bed reactors in laboratory--as well as in pilot-scale experiments. The efficiency and longevity of the P-RoC process was determined by the supply of Ca ions and the initial P concentration. Total P (P-tot) contents in the generated crystallisation products of up to 13% P-tot (30% P2O5) were achieved. Mineralogical investigations proved the formation of a hydroxy-apatite-(HAP)-like coating onto the seed material's surface. Reuse options for the generated crystallisation products, such as substitute for phosphate rock or as new fertiliser, were assessed.

Phosphate elimination and recovery from wastewater by active filtration using crushed gas concrete.

Laboratory long-term upstream fixed-bed experiments were carried out to investigate the efficiency of phosphorus elimination with the effluent of a biological sewage treatment plant using crushed gas concrete. The development of the pH-value in the column outflow as well as the reaction kinetics was investigated. Furthermore, the phosphorus yield was balanced for phosphorus recovery and the calcium phosphate compounds generated were specified by mineralogical analysis methods. These activities were followed by a study with respect to the suitability of the material as raw material for the phosphate industry.