Development and evaluation of an early removal process for the beneficiation of arsenic-bearing copper ores.

In conventional flotation flowsheets for treating copper sulphide ores containing small but significant amounts of arsenic, the arsenic is generally concentrated with the copper in final concentrate. Often, a penalty can be imposed by the smelter processing the concentrate, based on the arsenic content. In some cases the arsenic level is such that the smelter will not treat or accept the concentrate. A new approach to address this issue is reported in this paper, which is becoming more significant as the quality of the copper ore bodies currently being mined diminishes. A new flowsheet, based on the early removal of arsenic at the concentrator, has been developed and tested at bench-scale. The proposed flowsheet comprises three key steps: firstly, separation of arsenic and copper minerals using controlled-potential flotation to produce a low-arsenic high-copper concentrate and a high-arsenic low-copper concentrate. The low-arsenic concentrate can be sold without incurring any penalty for arsenic content. In the second stage, the high-arsenic concentrate is subjected to a low temperature roasting, where the arsenic is selectively fumed off into a low-volume stream product. The calcine from the roaster is high in copper and sulphur and can still be smelted directly. In the final stage of the flowsheet, the arsenic in the fume product is immobilised in a low temperature ceramic such that safe disposal back into the ground is possible. The new early removal flowsheet has been sequentially tested in the laboratory at small scale. The technical and economic merits of the flowsheet compared with that of the conventional copper flotation flowsheet show that there is a net benefit. © 2010, Elsevier Ltd

Water transport through cement-based barriers - a preliminary study using neutron radiography and tomography.

In this preliminary study we use neutron radiography and tomography to examine differences in water transport through cement pastes and mortars. Bulk residual water contents and sorptivity curves determined using neutron radiography are compared with data obtained gravimetrically. In addition, macro-pore volume distributions of each sample were measured. Furthermore, it was possible to use neutron radiography to monitor the change in the mass of water when samples were dried or when water moved into the samples. The trends and absolute values of weight loss and gain obtained using both approaches are very consistent for mortars, especially when a neutron-scattering correction is applied. © 2009, Elsevier Ltd

Appraisal of a cementitious material for waste disposal: neutron imaging studies of pore structure and sorptivity.

Cementitious materials are conventionally used in conditioning intermediate and low level radioactive waste. In this study a candidate cement-based wasteform has been investigated using neutron imaging to characterise the wasteform for disposal in a repository for radioactive materials. Imaging showed both the pore size distribution and the extent of the cracking that had occurred in the samples. The rate of the water penetration measured both by conventional sorptivity measurements and neutron imaging was greater than in pastes made from Ordinary Portland Cement. The ability of the cracks to distribute the water through the sample in a very short time was also evident. The study highlights the significant potential of neutron imaging in the investigation of cementitious materials. The technique has the advantage of visualising and measuring, non-destructively, material distribution within macroscopic samples and is particularly useful in defining movement of water through the cementitious materials. © 2010, Elsevier Ltd

Durability of a cementitious materials in waste disposal studies: integration of neutron tomography studies with other physical and chemical techniques.

To characterise and to evaluate the durability, structural properties and sorptivity of a candidate wasteform for ILW and gain an understanding of the factors that control water movement through the matrix and the matrix and the resultant degradation process.http://cement08.in2p3.fr/Presentation%20Workshop%20pour%20site%20web/Tuesday%2014/AM/Mc%20GLINN.pdfIN2P3; Laboratoire SUBATECH; ONDRAF/NIRAS; ANDRA; ATILH; U|B; ICB; Universite De Nantes; CNRS; Eccle Des Mines De Nante

Quantitative study of the reactivity of fly ash in geopolymerization by FTIR

Fourier transform infrared (FTIR) spectroscopy has been applied to analyse the environments of Al–O and Si–O bonds in fly ash, which are used as raw materials of geopolymer synthesis. It is noted that the relative intensities of the bands at around 1000, 910 and 700 cm-1 are much higher in fly ash with higher reactivity, as reflected by the compressive strength of geopolymer. Deconvolution analysis of the band from 400 to 1400 cm-1 shows that the cumulative area of these three resolved bands, together with the band at 1090 cm-1, which is assigned to the asymmetric stretching of Si(Al)–O–Si, is proportional to the reactivity of fly ash. If it is assumed that the area of the resolved bands is proportional to the concentration of the corresponding bonds, a general indication is therefore that fly ash containing more reactive bonds will exhibit higher reactivity in geopolymerisation. FTIR spectroscopy in combination with particle size analysis provides a fast approach to predict the reactivity of fly ash,from the perspective of aluminosilicate glass chemistry

Magnesium analogues of aluminosilicate inorganic polymers (geopolymers) from magnesium minerals

Attempts to synthesise magnesium-containing analogues of aluminosilicate geopolymers from the 1:1 and 2:1 layer magnesiosilicate minerals chrysotile and talc, as well as the magnesium mineral sepiolite are reported. The effect of pre-treating these starting minerals by grinding and/or dehydroxylation was also investigated by XRD, 29Si and natural-abundance 25Mg solid-state magic angle spinning (MAS) NMR spectroscopy. The products from sepiolite most closely resembled an aluminosilicate geopolymer, setting at 40 °C to an X-ray amorphous product containing a broad characteristic 29Si MAS NMR resonance at −90 ppm. The 25Mg MAS NMR spectrum of this product also showed evidence that some of the Mg was located in tetrahedral sites, as expected for a conventional geopolymer. A similar 25Mg MAS NMR result was obtained for chrysotile, but talc proved to be extremely resistant to geopolymer synthesis, requiring treatment at 120 °C for 3 days to set to a friable material retaining the XRD and NMR characteristics of the original talc or its crystalline dehydroxylation products. This lack of reactivity may be related to the 2:1 layer-lattice talc structure, or to the fact that a suitably reactive amorphous product is not formed upon dehydroxylation