Biotransformation of lanthanum by Aspergillus niger

Lanthanum is an important rare earth element and has many applications in modern electronics and catalyst manufacturing. However, there exist several obstacles in the recovery and cycling of this element due to a low average grade in exploitable deposits and low recovery rates by energy-intensive extraction procedures. In this work, a novel method to transform and recover La has been proposed using the geoactive properties of Aspergillus niger. La-containing crystals were formed and collected after A. niger was grown on Czapek-Dox agar medium amended with LaCl 3. Energy-dispersive X-ray analysis (EDXA) showed the crystals contained C, O, and La; scanning electron microscopy revealed that the crystals were of a tabular structure with terraced surfaces. X-ray diffraction identified the mineral phase of the sample as La 2(C 2O 4) 3·10H 2O. Thermogravimetric analysis transformed the oxalate crystals into La 2O 3 with the kinetics of thermal decomposition corresponding well with theoretical calculations. Geochemical modelling further confirmed that the crystals were lanthanum decahydrate and identified optimal conditions for their precipitation. To quantify crystal production, biomass-free fungal culture supernatants were used to precipitate La. The results showed that the precipitated lanthanum decahydrate achieved optimal yields when the concentration of La was above 15 mM and that 100% La was removed from the system at 5 mM La. Our findings provide a new aspect in the biotransformation and biorecovery of rare earth elements from solution using biomass-free fungal culture systems. </p

Borate retardation of cement set and phase relations in the system Na₂O-CaO-B₂O₃-H₂O

The CaO-rich portions of this system have been determined at 25° and 55°C. Twenty-one closely spaced compositions were prepared from analytical reagent-grade materials and reacted in sealed containers for up to 6 months. Solid phases were characterized mainly by X-ray diffraction and the aqueous phase was analysed chemically for Ca, Na and B. Solubility data were also obtained from singlephase preparations of selected hydrates; in conjunction with data in the literature, extensive thermodynamic modelling of solubility relations was undertaken. The combination of calculation and experimental determinations enabled the equilibrium features to be determined rapidly; cross-checks between calculated and experimental data are presented. </jats:p

Investigating Techniques for Evaluating Fly Ash Behaviour in Air-entrained Concrete

Abstract The paper describes research from a study carried out to investigate techniques for evaluating fly ash influences on air-entrainment in concrete and covers the potential of dye adsorption tests, i.e. using methylene blue (MB) and acid blue 80 (AB80), in this role. The MB test is essentially that given in BS EN 933-9 (normally used for the assessment of fines in sand) and involves visual determination of an endpoint, while the AB80 test (similar to those used for examining activated carbon) is spectroscopic and, therefore, instrument-based. Following the determination of suitable procedures for the tests, their evaluation with fly ashes covering a range of properties is described through comparisons against parameters including, loss-on-ignition and specific surface area (measured by N 2 adsorption). Relationships are presented that examine the dye adsorption of fly ash with respect to the air-entraining admixture demand to achieve a target air content range (5.0 ± 1.0%) in corresponding concretes. These indicate strong correlations for the materials used. Consideration is given to how the dye adsorption tests could be applied in air-entrained fly ash concrete production

Feasibility of utilising quarry fines and waste silts to manufacture synthetic lightweight sand

Silt materials arising from the crushing of primary aggregates, wash plants, demolition and excavation materials and industrial wastes such as glass cullet are often landfilled, as they are generally not suitable for fill purposes and find limited opportunities for recycling within construction products. With over 20 Mt of silt produced from quarrying alone, and given its detrimental performance when added to mortar or concrete due to increasing water demand and higher shrinkage strains, there is a responsibility to find productive uses for such materials, as long-term landfilling is both environmentally unsound and uneconomic. As a response, this paper reports initial work into the technical feasibility of a novel technology to convert a range of silts into manufactured sand by up-sizing the material by initially incorporating and then crushing foamed concrete into sand-sized particles. The resulting ‘silt sand' was then exposed to carbon dioxide to enhance its strength. The resulting material was sieved and recombined into a specific particle size distribution and assessed for performance. The silt sand had a low density, and is characterised as a lightweight material. Data are presented for the use of the sand at 20% and 50% direct volume replacement for dense sand using standard mortar strength tests, and it is shown that the impact of this is less than might be expected for a lightweight aggregate. </jats:p