Papers by Keyword: Copper

Abstract: Most microorganisms grow on surfaces as biofilms rather than as individual planktonic cells, and cells within biofilms show high levels of resistance against antimicrobial drugs. Thereby biofilm formation complicates treatment and contributes to high morbidity and mortality rates associated with infections. This study explores the physical, optical, and nano-structural properties of silver and copper nanoparticles dispersed in aqueous suspensions (nanoparticulate colloidal water) and examines their in vitro activity against microbial biofilms. Silver and copper nanoparticulate colloidal water of various concentrations were prepared and studied. Their surface energies, surface charge and surface plasmonic resonance properties were determined using contact angle measurement, zeta potential measurement and optical spectrometry, respectively. A model of biofilm formation on the wells of microtiter plates was used to determine the activity of the nanoparticulate suspensions against fungal and bacterial biofilms. Scanning electron microscopy (SEM) was used to observe the nanoparticle interactions with microbial cells within the biofilms. Results show that silver nanoparticle-containing liquids have higher surface energy than their copper counterparts; and that the surface energy increases as the concentration of silver nanoparticles increases. Altogether, the effectiveness of silver nanoparticle colloidal suspensions in controlling biofilm formation is observed and reported. For a given size of silver nanoparticles studied, it is found that the effective concentrations against microbial biofilms are far lower than their cytotoxic concentrations, indicating an overall safety and a good therapeutic index thus substantial application potential.

Abstract: Cu-Ti alloy, pure copper, and stainless steel AISI 304 were tested in this study for their microstructure, effect of alloying element to hardness, and antibacterial activity. The antibacterial properties were tested against E. coli suspensions. The titanium in Cu-Ti alloy was varied 1-4 wt. %, and the microstructure was modified by homogenization treatment. The antibacterial susceptibility test was done by inhibition zone measurement and bacterial suspension inoculation methods. Result showed the addition of titanium increased hardness from pure copper (44.93 HV) to 79.68-207.6 HV. No inhibition zone was observed for the stainless steel samples, while the largest inhibition zone diameter was gained by pure copper (12.4 mm). The killing bacteria activity test concluded that the compositions of the alloys were not directly linked to the antibacterial activity.

Abstract: This European Union ERASysApp funded study will investigate one of the major drawbacks of bioleaching of the copper containing mineral chalcopyrite, namely the long lag phase between construction and inoculation of bioleaching heaps and the release of dissolved metals. In practice, this lag phase can be up to three years and the long time period adds to the operating expenses of bioheaps for chalcopyrite dissolution. One of the major time determining factors in bioleaching heaps is suggested to be the speed of mineral colonization by the acidophilic microorganisms present. By applying confocal microscopy, metatranscriptomics, metaproteomics, bioinformatics, and computer modeling the authors aim to investigate the processes leading up to, and influencing the attachment of three moderately thermophilic sulfur-and/or iron-oxidizing model species: Acidithiobacillus caldus, Leptospirillum ferriphilum, and Sulfobacillus thermosulfidooxidans. Stirred tank reactors containing chalcopyrite concentrate will be inoculated with these species in various orders and proportions and the effects on the lag phase and rates of metal release will be compared. Meanwhile, confocal microscopy studies of cell attachment to chalcopyrite mineral particles, as well as metatranscriptomics and metaproteomics of the formed biofilms will further increase understanding of the attachment process and help develop a model thereof. By fulfilling our goal to decrease the length of the lag phase of chalcopyrite bioleaching heaps we hope to increase their economic feasibility and therefore, industrial interest in bioleaching as a sustainable technology.

Abstract: In order to recovery base and precious metals from processing plants tailings of Southern Ural and the Murmansk region, test work on heap biooxidation using these products was carried out. These tests involved the chemical and mineralogical analyses of the samples, the bacteria adaptation for the products tested, heap biooxidation in percolation columns, base metals (copper, nickel, zinc) precipitation and gold cyanidation. The recoveries of base metals to the solution from the products of magnetic separation of the wastes were 75% Ni and 50% Cu. This work is aimed at studying sustainability of magnetic separation products and pyrite tailings biotechnological processing. Also, gold and base metals recovery to the solution and the options of base metals removal from the solutions were studied.

Abstract: Demand for copper is growing in the world,which makes it increasingly necessary to process low-grade ores and tailings that used to be considered as wastes. The development and application of bioleaching by acidophilic chemolithotrophic microorganisms, which obtain energy from the oxidation of sulfide minerals and use carbon dioxide for constructive metabolism, has been a major approach for processing the low-grade copper ores. In this study, mixed culture consisted of six iron and sulfur oxidizing microorganisms were used in leaching of flotation and acid-leaching tailings obtained from Zambia sulfide ores. The result showed that 62.7% and 61.7% copper were dissolved by bioleaching, while 53.8% and 57.4% by acid leaching in flotation and acid leaching tailings, respectively. In addition, mineralogical forms of copper were quite noteworthy since copper sulfide mineral extraction was significantly improved in bioleaching. XRD analysis showed wollastonite and diopside in acid tailing were undetectable after 23 days while others were difficult to be dissolved. No jarosite or sulphur was detected by XRD in residues.

Abstract: Water is the source of life and an essential resource for our global economy. It empowers agricultural and industrial production and development, and fosters the nature and ecosystems. With increasing water scarcity, growing population, climate change and extreme weather conditions, together with stricter water regulations, decline in ore grade and increasing controversy on water use between mining operations and local communities, effective governance of shared water resources and protecting water quality is an economic imperative and social responsibility for mining companies. Water Footprint Assessment (WFA) is a holistic methodological framework that allows integrated assessment for operational and supply-chain water use and the associated water footprint sustainability in different sectors at various spatial and temporal scales. This paper presents a WFA for two copper products – copper cathode and copper concentrate produced by Zijin Mining (China) based on the data from 2012 and 2013. The aim of this study is to evaluate the water consumption within the operations and supply chains, to understand the product sustainability and identify water footprint reduction targets to minimize its associated social and environmental impact on natural resources in the catchment. The two copper products were produced from two different processes, hence their different associated water footprints. Evaporation due to the vast area of heap leach pad is the main contribution to the blue water footprint (WF) for copper cathode whereas supply chain WF is negligible. The grey WF is found to be due to total copper concentration in the effluent discharge. This assessment goes beyond water footprint accounting stage and includes the environmental sustainability of the direct water footprint. Opportunities for efficiency improvement across the two processing plants and prevention strategies to reduce impacts on the environment are also discussed. The comprehensive approach makes the WFA unique from other water use assessments and shows its value in water sustainability strategy making.

Abstract: A low pH sulfate-reducing bioreactor was used to selectively recover copper from synthetic pH 5 mine water draining a copper mine in Brazil, and also to remove other transition metals from solution. The design of the system used meant that a single bioreactor could be used for the process. Over 99% of the copper present was recovered as CuS in an off-line reactor vessel, while other metals (Ni, Co and Zn) were precipitated in the bioreactor vessel.

Abstract: The efficiency of chalcopyrite bioleaching in a high sulfate background was evaluated using acidophilic microorganisms adapted to sulfate. The concentration of magnesium sulfate added to mesophilic, moderately thermophilic and thermophilic bioleaching tests was equivalent to 100, 40 and 80 g L^-1 SO₄^2-, respectively. Biological copper extraction was highest at 45 °C (67 %), followed by 60 °C (54 %) and 30 °C (16 %). Quantitative x-ray diffraction (QXRD) analysis of the ROM ore and bioleached residues revealed the complete disappearance of pyrrhotite and a significant reduction of pyrite at all temperatures. Significant chalcopyrite was leached at 45 and 60 °C; however, no chalcopyrite was leached at 30 °C. As the bioleach did not plateau after 31 days, it is possible that higher copper yields may have been achieved with prolonged leaching.

Abstract: The need for super-plasticity and high strength leads to the development of Severe Plastic Deformation technique. The strength of the material is directly dependent upon the grain size of the material. So, there is a need for producing Ultra-Fine Grain microstructure (UFG). UFG material is the material with very small grain size in the range of sub-micrometre. Application of severe plastic deformation, imparts extremely high strain. Equal channel angular pressing (ECAP) is a severe plastic deformation process in which the metal specimen is pressed through an angular channel of equal cross section. The material is subjected to shear deformation and strain is imparted in the specimen. Geometric parameters such as channel angle and corner angle play a major role in grain refinement. Aluminium (Al) specimens are subjected to undergo severe plastic deformation. Since, the strength of Al is not high, other materials are added in order to enhance its mechanical properties by matrix work hardening. Copper (Cu) along with Al shows increase in its strength and also in hardness. An attempt is made with Aluminium and copper, blended in the ratio 95:5 by weight with the main objective to study the Tensile strength, Hardness and Percentage Elongation properties of the specimen.

Abstract: Powder Metallurgy (P/M) is a manufacturing process in which powders are compacted in a die to attain the final product. P/M has certain unique advantage like controlled porosity, High Strength to weight ratio. Aluminium (Al) is a light weight material, but pure Al does not possess a good strength. To achieve the strength, Copper (Cu) powders are blended at required proportions. Al along with Cu shows good mechanical properties. An attempt is made to optimize the process parameter of Al – 10% Cu powder to attain maximum process efficiency. Here optimization is done by Taghuchi’s method.