Siltation of Ore Particles in Leaching Tanks: Causative Factors and Mitigation Measures

Siltation involves the accumulation of sediment over a considerable period of time and this may occur in closed systems like leaching tanks. Most mining companies in Ghana experience siltation problems during leaching of gold ore. This paper examines the potential causes and possible mitigation measures of siltation. Particle size analysis, slurry settling rate tests and agitation efficiency analysis were used in identifying causative factors of siltation whiles deflocculation test and grind analysis were conducted to ascertain mitigation measures.  Results from the study indicated that, high settling velocity of particles, inefficient milling and classification, poor slurry agitation and particle flocculation were the major causative factors leading to siltation. Size analysis results revealed P67 of 106 µm instead of P80 of 106 µm, a situation which affects particle suspension by agitators leading to siltation. This study therefore suggests that increase in milling residence time and particle deflocculation are potential remediation measures for curbing siltation. Extended grinding of ball mill feed resulted in 94% passing 106 µm while settling velocity was reduced by 71% after deflocculant addition at 1000 ppm. Keywords: Siltation, Deflloculation, Settling Velocity, Grindin

Prevalence of Overweight and Obesity among Students in the Kumasi Metropolis

The aim was to determine the prevalence of obesity and overweight among students in the Kumasi metropolis. In a descriptive cross-sectional study, 500 students aged 10 to 20 years were examined from two junior high schools selected by multistage sampling technique and three randomly selected senior high schools. Height and weight were measured in all participants and the body mass index (BMI) of each individual was calculated. Body mass index classes were calculated according to the International Obesity Task Force standards. Out of the 500 students, 290 (58.00%) were males and 210 (42.00%) were females. The prevalence of underweight, normal weight, overweight, and obesity was 7.40%, 79.60%, 12.20%, and 0.80%, respectively. Overweight was more prevalent among students than obesity. There is therefore the need to establish effective public health promotion campaigns among students in order to curtail future implications on health

A study of the feasibility of upgrading rare earth elements minerals from iron-oxide-silicate rich tailings using Knelson concentrator and Wilfley shaking table

A number of gravity separation techniques for rare earth elements (REE) minerals have been investigated and reported in the literature. These include the use of dense/heavy media, Falcon concentrators, Knelson concentrators, spiral concentrators, laboratory scale jigs, and shaking tables. Most of these methods have provided considerable REE minerals recovery and upgrade; but remain at the laboratory testing stage. There are vast quantities of iron-oxide-silicate rich tailings (IST) containing low grade REE in Australia. This work is part of research and development studies currently underway at the University of South Australia to develop economically viable methods to exploit selected IST for their REE contents. In this investigation, the feasibility of exploiting the differences in specific gravity to concentrate REE minerals from a typical IST sample was studied using two gravity separation units, a Knelson concentrator (KC) and Wilfley shaking table. The feed sample and gravity separation products were characterised using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Quantitative Evaluation of Minerals by Scanning Electron Microscopy (QEMSCAN) to study and compare the performance of the KC and shaking table as gravity preconcentration methods. The results indicated that the performance of both the KC and shaking table are significantly dependent on the mineralogical and particle size characteristics of the feed, however, the tabling was found to be the preferred choice over the KC, due to its greater selectivity. Tabling of >38 μm feed samples produced the desired split between the iron oxides and silicate minerals. The results suggest that desliming of the feed to remove fine/ultrafine particles (<38 μm) prior to tabling is key to attaining the desired results with the shaking table. Overall, tabling produced appreciable REE minerals upgrade, with iron oxides occupying the bulk of the concentrates. The test results confirm the complex mineralogy of the IST, which compromised REE minerals upgrade. A modified concentration criterion expression which considers the liberation characteristics of minerals is proposed, which provides a better idea on the feasibility of gravity separation.George Blankson Abaka-Wood, Keith Quast, Massimiliano Zanin, Jonas Addai-Mensah, WilliamSkinne

Assessment of estimated low-density lipoprotein-cholesterol (LDL-c) equations: a systematic review and meta-analysis

Abstract Background Low-density lipoprotein cholesterol (LDL-c) is the major determinant of cardiovascular disease burden. This study critically reviewed the published literature and performed a meta-analysis to compare and to determine which other equations provide the best means of estimating LDL-c in clinical settings. Method English articles indexed in PubMed, Science Open, Biomed central and SpringerLink databases were searched with searches being conducted in or after 2001 up to date. According to the predefined inclusion and exclusion criteria, 22 articles out of the 17,970 retrieved were eligible for quantitative analysis. Data were pooled and meta-analysis performed using a random-effects model, and the results are described as event rates (pooled correlation coefficient). Main body of the abstract All the twelve equations showed positive correlation with the respective direct low-density lipoprotein-cholesterol measurements. The pooled estimates showed a stronger positive correlation between Martin’s low-density lipoprotein-cholesterol equation and the direct low-density lipoprotein-cholesterol measurement [0.96 (95% CI 0.94–0.98)] as compared to Friedewald’s equation and the direct method [0.94 (95% CI 0.92–0.96)]. At triglycerides levels > 400 mg/dl, Martin’s low-density lipoprotein-cholesterol equation established better performance (77.78%) than the Friedewald’s equation. In studies where triglycerides levels > 400 mg/dl were excluded Martin’s low-density lipoprotein-cholesterol equation still established better performance (83.33%) than the Friedewald’s equation. Short conclusion Our data suggest that Martin’s equation showed a better performance than Friedewald equation. Martin’s equation can serve as a more accurate method to estimate low-density lipoprotein cholesterol as compared to Friedewald’s equation especially in situations of the same racial background

Monitoring power transformers oils deterioration using structured laser illumination planar imaging

Reliable quality assessments of oils in power transformers are important as they provide valuable information regarding the proper functioning of transformers. Thus, an early and accurate diagnostic of power transformers oils can prevent potential failures of transformers. In this paper, an imaging technique known as Structured Laser Illumination Planar Imaging (SLIPI) was used to monitor the extinction coefficient in various oil samples. The proposed technique offers the advantage of extracting the light intensity contribution from singly scattered photons and rejecting most of the light intensity from photons that have been scattered many times. This leads to more accurate and reliable measurement of the extinction coefficient , in optically dense oil samples. The variation of the extinction coefficient was therefore determined as a function of oil aging. The results demonstrate that SLIPI is reliable as a practical measurement method for the diagnosis of power transformer oils and present an attractive solution, alternative to the conventional methods such as Dissolved Decay Products, Interfacial Tension and Turbidity

Monitoring power transformers oils deterioration using structured laser illumination planar imaging

Reliable quality assessments of oils in power transformers are important as they provide valuable information regarding the proper functioning of transformers. Thus, an early and accurate diagnostic of power transformers oils can prevent potential failures of transformers. In this paper, an imaging technique known as Structured Laser Illumination Planar Imaging (SLIPI) was used to monitor the extinction coefficient in various oil samples. The proposed technique offers the advantage of extracting the light intensity contribution from singly scattered photons and rejecting most of the light intensity from photons that have been scattered many times. This leads to more accurate and reliable measurement of the extinction coefficient , in optically dense oil samples. The variation of the extinction coefficient was therefore determined as a function of oil aging. The results demonstrate that SLIPI is reliable as a practical measurement method for the diagnosis of power transformer oils and present an attractive solution, alternative to the conventional methods such as Dissolved Decay Products, Interfacial Tension and Turbidity