The behaviour of free gold particles in a simulated flash flotation environment

A reliable laboratory method to characterize the response of free gold particles to flash flotation conditions has been developed. The test has been performed on free milling gold ores as well as synthetic ores, using either a gravity concentrate or gold powder as the gold source, to assess the floatability of gold particles. Trends in free gold flotation kinetics, as well as size and milling effects, were identified for gold recovery based on the different feed types, reagent dosages, and residence times. It was shown that the ultimate recoveries and kinetic trends of gold particles from the gravity concentrate could be enhanced with increased dosage of collector, potassium amyl xanthate. Interestingly, in comparison to gravity-recoverable gold, recovery from pure Au powders was better in collectorless flotation, and cumulative recovery decreased with higher levels of collector addition. Improved coarse particle recovery appeared linked to increased collector additions for both the gravity concentrate and the pure gold powders. In general, coarse gold particles demonstrated slower kinetic rates than the fine or intermediate components incomparable tests

A conceptual flowsheet for heap leaching of platinum group metals (PGMs) from a low-grade ore concentrate

peer reviewedThis research proposes a new conceptual process to economically extract platinum group metals (PGMs), and as a secondary aim, base metals (BMs) from a low-grade concentrate originating from typical PGM concentrator plants. Slurry made from the concentrate was coated onto granite pebbles and packed into a column, in which it was bioleached with a mixed culture of thermophiles and mesophiles at 65 °C. After 30 days the extractions achieved were 52% copper, 95% nickel and 85% cobalt. The residual concentrate material was subsequently subjected to a cyanide leach also in a packed column operating at a room temperature of 23 °C. After 21 days 20.3% Pt, 87% Pd and 46% Rh were extracted. Using these results and projected extractions over longer operating times, a conceptual flowsheet was proposed for a possible process route to recover PGM values circumventing the problematic smelter route for this material

Promoting deeper learning in pharmacy education using team-based learning

Background. The benefit of deep learning compared with surface learning is the ability to retrieve, apply and integrate previously learnt knowledge rather than simply memorising course content most likely to be evaluated during assessments. Team-based learning (TBL) is an educational strategy that echoes the purpose of deeper learning. Objectives. To identify whether TBL as a teaching strategy increases pharmacy students’ understanding of theoretical work. Method. Fourth-year pharmacy students completed a questionnaire consisting of biographical data (gender, age and ethnicity) and 16 questions on their understanding of course content. A total of 183 students (91.5%) participated after giving informed consent that their data may be included in the study. Results. The results indicated that, due to the implementation of TBL in the course, students perceived that they learnt more and made more effort, experienced increased understanding of content, perceived higher knowledge retention, performed better during assessments in the module where TBL was implemented and felt that course outcomes were achieved more easily. Conclusion. TBL as a teaching strategy could potentially promote deeper learning of course content

Operation of a concentrated mode dual-alkali scrubber plant at the Lonmin smelter

Lonmin Platinum installed a concentrated mode dual-alkali scrubber at the smelter in Marikana in 2002. The dual-alkali scrubber was the technology of choice at that time as a sulphur fixation plant, due to the perceived benefits of handling both the high SO2 concentrations of converter off-gas and the swings in SO2 concentration that are linked to Peirce-Smith operation. Owing to current and impending legislative requirements for air quality and waste, Lonmin is currently considering additions to the dual-alkali plant, but is also evaluating alternative technologies for sulphur fixation. This paper reviews the decision of Lonmin to install a concentrated mode dual-alkali scrubber and presents plant performance achieved. It also describes the important control variables and sensitivities of the plant, and the final product that is produced by the operation of the plant. The legislative requirement that drives the Lonmin technology evaluation is also discussed

Assessing a Two-Stage Heap Leaching Process for Platreef Flotation Concentrate

The Platreef is a relatively rich ore body in terms of the presence of platinum group metals (PGMs) and base metals (BMs). It differs from the Merensky and UG2 ore bodies in that a significant portion of the PGMs are associated with the silicates or on base metal sulphide-silicate grain boundaries, it has an unfavourable Pt to Pd ratio and although there is significant Au, there is much less Rh and Ru than in the Merensky or UG2 ores. Additionally, a large portion of PGMs occur as bismuth-tellurides and arsenides, which have been observed to be slow floating, requiring high mass pulls to obtain high concentrator recoveries. The high mass pulls invariably leads to grade dilution. Due to this unique mineralogy the conventional process of milling, flotation, smelting and matte pressure leaching leads to marginal process economics, with high energy and water costs, high skilled labour requirements and large capital and operating costs. Moreover, the Platreef resource lies in an arid area of South Africa, with a low skilled labour pool and poor electrical infrastructure. Additionally, a considerable amount of the PGMs will report to the tailings and will not be recoverable by flotation. A novel flowsheet to process this ore is proposed here, which represents a parallel low-cost route, along the standard method.This revolves around a two-stage heap leaching process consisting of a high temperature bioleach to extract base metals followed by a precious metals heap leach. This is currently being evaluated through preliminary bench scale test work. The results so far, which will be presented, have been promising

Sonic injection into a PGM Peirce-Smith converter: CFD modelling and industrial trials

Peirce-Smith converters (PSCs) are extensively used in the copper, nickel, and platinum group metals industries. The typical converting operation involves lateral purging of air into molten matte through a bank of tuyeres. This blowing operation occurs at low pressure from the blowers, resulting in a bubbling regime that is considered inefficient from both a process and an energy utilization perspective. Inherent drawbacks also include recurrent tuyere blockage, tuyere punching, and low oxygen efficiency. Western Platinum embarked on a full-scale industrial evaluation of generating a jetting regime by using sonic injection. Prior to industrial- scale tests, a numerical assessment to ascertain the feasibility of implementing sonic injection into a PSC was conducted. The work included flow characterization at high-pressure injection achieving sonic velocity at the tuyere exit. The 2D and 3D simulations of the three-phase system were carried out using the volume of fluid method together with the RKE turbulence model to account for the multiphase and turbulent nature of the flow. This paper discusses the key findings in understanding plume extension, velocity distribution, shear wall stress analysis, and phase distribution characteristics in the system. Plant trials are also discussed with reference to the commercial aspects of a full-scale implementation of sonic injection in the smelter

Kinetic study on the removal of iron from gold mine tailings by citric acid

Abstract: The Gold mining generates large volumes of tailings, with consequent disposal and environmental problems. Iron tends to react with sulphur to form pyrite and pyrrhotite which then react with rain water forming acid rain. The study focuses on the removal of iron (Fe) from Gold Mine tailings; Fe was leached using citric acid as a leaching reagent. Three parameters which have an effect on the removal of Fe from the gold mine tailings, namely; temperature (25 ºC and 50 ºC), reagent concentration (0.25 M, 0.5 M, 0.75 M and 1 M) and solid loading ratio (20 %, 30 % and 40 %) were investigated. It was found that the recovery of Fe from gold mine tailings increased with increasing temperature and reagent concentration, but decreased with increasing solid loading ratio. The optimum conditions for the recovery of Fe from gold mine tailings was found to be at a temperature of 50 ºC, reagent concentration of 1 M and solid loading of 20 %. Three linear kinetic models were investigated and Prout- Tompkins kinetic model was the best fit yielding linear graphs with the highest R2 values

Immunosuppression in new-born lambs

A novel technique, based on cytotoxicity-neutralization, was developed for the in vitro titration of anti-sheep lymphocyte and anti-sheep macrophage sera. The titres obtained for a number of antisera were compared with those found in an agglutination assay. Anti-lymphocyte sera with a high cytotoxicity-neutralization titre very effectively suppressed the number of circulating lymphocytes the peripheral blood of treated new-born lambs, thus indicating in vivo immunosuppressive activity.The articles have been scanned in colour with a HP Scanjet 5590; 300dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

Hepatic Endothelial CCL25 Mediates the Recruitment of CCR9+ Gut-homing Lymphocytes to the Liver in Primary Sclerosing Cholangitis

Primary sclerosing cholangitis (PSC), a chronic inflammatory liver disease characterized by progressive bile duct destruction, develops as an extra-intestinal complication of inflammatory bowel disease (IBD) (Chapman, R.W. 1991. Gut. 32:1433–1435). However, the liver and bowel inflammation are rarely concomitant, and PSC can develop in patients whose colons have been removed previously. We hypothesized that PSC is mediated by long-lived memory T cells originally activated in the gut, but able to mediate extra-intestinal inflammation in the absence of active IBD (Grant, A.J., P.F. Lalor, M. Salmi, S. Jalkanen, and D.H. Adams. 2002. Lancet. 359:150–157). In support of this, we show that liver-infiltrating lymphocytes in PSC include mucosal T cells recruited to the liver by aberrant expression of the gut-specific chemokine CCL25 that activates α4β7 binding to mucosal addressin cell adhesion molecule 1 on the hepatic endothelium. This is the first demonstration in humans that T cells activated in the gut can be recruited to an extra-intestinal site of disease and provides a paradigm to explain the pathogenesis of extra-intestinal complications of IBD

A cross-sectional survey and cross-sectional clinical trial to determine the prevalence and management of eye movement disorders and vestibular dysfunction in post-stroke patients in the sub-acute phase : protocol

INTRODUCTION: Visual impairment, specifically eye movement disorders and vestibular dysfunction may have a negative influence on the functional recovery in post-stroke patients. This type of sensory dysfunction may further be associated with poor functional outcome in patients' post-stroke. METHODS: In phase 1, a cross-sectional survey (n = 100) will be conducted to determine the prevalence of eye movement disorders and vestibular dysfunction in patients who sustained a stroke. A cross-sectional clinical trial (n = 60) will be conducted during phase 2 of the study to determine the effect of the combination of vestibular rehabilitation therapy (VRT) and visual scanning exercises (VSE) (experimental group) integrated with task-specific activities compared with the effect of task-specific activities as an intervention (control group) on patients who present with eye movement impairment and central vestibular dysfunction post-stroke. An audiologist will assess (a) visual acuity (static and dynamic), (b) nystagmus, (c) saccadic eye movements, (d) smooth pursuit eye movements, (e) vestibulo-ocular reflex, and (f) saccular, utricular, and vestibular nerve function. An independent physiotherapist will assess (1) cognitive function, (2) residual oculomotor visual performance, (3) visual-perceptual system, (4) functional balance, (5) gait, (6) functional ability, (7) presence of anxiety and/or depression, and (8) level of participation in physical activity. ETHICS AND DISSEMINATION: Ethics approval has been obtained from the Ethics Committee of the Faculty of Health Sciences at the University of Pretoria (UP) (374/2015). The study will be submitted as fulfillment for the PhD degree at UP. Dissemination will include submission to peer-reviewed professional journals and presentation at congresses. Training of rehabilitation team members on the integration of VSE and VRT into task-specific activities in rehabilitation will be done if the outcome of the experimental group's functional performance is clinically and statistically significantly better than the control group on the Barthel Index. TRIAL REGISTRATION: Pan African Clinical Trials Registry (PACTR201509001223262).The principal researcher received a National Research Foundation Innovation Doctoral scholarship for 2016 and funding from the South African Society of Physiotherapy’s Research Foundation (VAN180).http://journal.frontiersin.org/journal/neurologyam2016PhysiotherapySpeech-Language Pathology and Audiolog