A process mineralogy approach to optimize molybdenite flotation in copper � molybdenum processing plants

The Sungun copper-molybdenum operation in Iran uses a typical copper-molybdenum flowsheet to produce separate copper and molybdenum concentrates through flotation and regrinding of the rougher concentrates arising from the primary circuit. This site was used as a case study limited to the feed and products of the copper-molybdenum separation circuit, in which process mineralogy might improve the quality of the molybdenum concentrate thorough diagnostic analysis of key flowsheet streams. The undesirable presence of copper in the molybdenum concentrate was identified as a key focus for the investigation by process mineralogy, which has a history of successful process diagnosis. This is because it develops information on minerals, which is far more informative than chemical assays alone. Together with the assays, the mineralogical data inform the investigator of the type and quantity of minerals present, their state of liberation and textural associations, and metal recovery. A key finding was that the appearance of chalcopyrite in the molybdenum concentrate was due to the presence of a chalcopyrite-pyrite texture that avoided the chalcopyrite depression in the molybdenum circuit because of suitable pyrite flotation conditions. Recovery of liberated pyrite to this concentrate also diluted the molybdenum concentrate. The open-circuit format of the regrind circuit also contributed to the unnecessary production of ultrafine particles. This flaw expressed itself as ultrafine losses of molybdenite to the flotation tailings. © 202

Titanium mesh-reinforced calcium sulfate for structural bone grafts

Calcium sulfate (CS) possesses many of the requirements for an ideal bone graft material: it is biodegradable, biocompatible, and osteoconductive. However, its relatively low strength and brittleness are major obstacles to its use as a structural bone implant. Although the strength of CS can be improved by reducing porosity, its brittleness remains a major obstacle towards its use as bone graft. Here we combine two powerful toughening strategies which are found in advanced ceramics and in natural bone: Multi-layered architectures and ductile reinforcements. We first used stress analysis and micromechanics to generate design guidelines that ensure the proper failure sequence and maximize properties. We then fabricated and tested fully dense CS by hydrostatic compression layered with layers of titanium woven mesh. Flexural experiments in hydrated conditions confirmed that the ductility and strength of titanium and the adhesion at the titanium-CS interfaces (controlled by the size of the Ti mesh) are critical factors in the mechanical performance of the composite. Our best design exhibited a toughness 180 times larger than that of plain CS, together with a 46% increase in strength.</p

Configuration of flowsheet and reagent dosage for gilsonite flotation towards the ultra-low-ash concentrate

Gilsonite has a wide variety of applications in the industry, including the manufacture of electrodes, paints and resins, as well as the production of asphalt and roof-waterproofing material. Gilsonite ash is a determining parameter for its application in some industries (e.g., gilsonite with ash content < 5 used as an additive in drilling fluids, resins). Due to the shortage of high grade (low ash) gilsonite reserves, the aim of this study is to develop a processing flowsheet for the production of ultra-low-ash gilsonite (< 5), based on process mineralogy studies and processing tests. For this purpose, mineralogical studies and flotation tests have been performed on a sample of gilsonite with an average ash content of 15. According to mineralogical studies, carbonates and clay minerals are the main associated impurities (more than 90 vol.). Furthermore, sulfur was observed in two forms of mineral (pyrite and marcasite) and organic in the structure of gilsonite. Most of these impurities are interlocked with gilsonite in size fractions smaller than 105 µm. The size fraction of + 105 � 420 µm has a higher pure gilsonite (approximately 90) than other size fractions. By specifying the gangue minerals with gilsonite and the manner and extent of their interlocking with gilsonite, + 75 � 420 µm size fraction selected to perform flotation tests. Flotation tests were performed using different reagents including collector (Gas oil, Kerosene and Pine oil), frother (MIBC) and depressant (sodium silicate, tannic acid, sulfuric acid and sodium cyanide) in different dosages. Based on the results, the use of kerosene collector, MIBC frother and a mixture of sodium silicate, tannic acid, sulfuric acid and sodium cyanide depressant had the most favorable results in gilsonite flotation in the rougher stage. Cleaner and recleaner flotation stages for the rougher flotation concentrate resulted in a product with an ash content of 4.89. Due to the interlocking of gilsonite with impurities in size fractions � 105 µm, it is better to re-grinding the concentrate of the rougher stage beforehand flotation in the cleaner and recleaner stages. Finally, based on the results of mineralogical studies and processing tests, a processing flowsheet including crushing and initial granulation of gilsonite, flotation in rougher, cleaner and recleaner stages has been proposed to produce gilsonite concentrate with < 5 ash content. © 2021, The Author(s)

Feasibility of cone-beam computed tomography in detecting lateral canals before and after root canal treatment: An ex vivo study

Introduction: The study objective was to evaluate the effectiveness of cone-beam computed tomographic (CBCT) imaging for the detection of lateral canals (LCs) in endodontically treated premolars. Methods: Two evaluators classified 80 extracted premolars into 2 groups based on the absence (n = 40) or presence (n = 40) of LCs according to micro-computed tomographic analysis. The extracted teeth were fixated in a human mandible and scanned with CBCT imaging. Subsequently, each tooth was endodontically treated, and CBCT scans were repeated. Three experienced examiners evaluated all images randomly. Receiver operating characteristic curves were compared using the McNemar test, and sensitivity, specificity, positive predictive value, and negative predictive value (NPV) were obtained. Results: The area under the receiver operating characteristic curve values were 0.58 and 0.49 before and after root canal treatment, respectively. These values were statistically significantly different (P < .001). Before root canal treatment sensitivity, specificity, positive predictive value, and negative predictive value were 55%, 52%, 55%, and 56%, whereas after root canal treatment the values were 33%, 61%, 46%, and 48%, respectively. Conclusions: LC detection in nontreated teeth presented low accuracy, whereas among treated teeth CBCT imaging showed no efficacy. The results suggest that CBCT imaging is not an effective diagnostic tool for LC detection

PARTICULATE POLYCYCLIC AROMATIC HYDROCARBONS IN URBAN AIR OF TEHRAN

Polycyclic Aromatic Hydrocarbons are ubiquitous in the urban atmosphere and one of the most atmospheric pollutants to be identified as suspected carcinogens .The objective of this study was to compare particulate PAH profiles from several sites across Tehran. Atmospheric concentrations of Polycyclic Aromatic Hydrocarbons in Tehran were evaluated to study particulate PAH profiles in different sites. The particles size distributions were unimodal with a fine mode diameter (PM<0.49 μm). Five sites were selected in residential areas and one site in rural area for representing various situations and role of motor vehicles in producing Polycyclic Aromatic Hydrocarbons. Organics on the filter were extracted with acetonitrile and a group of 16 Polycyclic Aromatic Hydrocarbons was selected for evaluation. PAH identification was done by High Performance Liquid Chromatography. Total PAH concentration associated with particles collected on the six-stage cascade impactor stages and after-filter in different sites ranged between 0.132 to 234.3 ng/m3. The mean concentrations of Polycyclic Aromatic Hydrocarbons, collected on each stage were: 4.17 ng/m3 for PM10-7.2 μm, 5.69 ng/m3 for PM7.2 - 3 μm, 11.95 ng/m3 for PM3 - 1.5 μm, 9.18 ng/m3 for PM1.5-0.95 μm, 2.82 ng/m3 for PM0.95-0.49 μm and 47.91 ng/m3 for PM < 0.49 μm respectively

Process mineralogy as a key factor affecting the flotation kinetics of copper sulfide minerals

The aim of this study is to apply process mineralogy as a practical tool for further understanding and predicting the flotation kinetics of the copper sulfide minerals. The minerals’ composition and association, grain distribution, and liberation within the ore samples were analyzed in the feed, concentrate, and the tailings of the flotation processes with two pulp densities of 25wt% and 30wt%. The major copper-bearing minerals identified by microscopic analysis of the concentrate samples included chalcopyrite (56.2wt%), chalcocite (29.1wt%), covellite (6.4wt%), and bornite (4.7wt%). Pyrite was the main sulfide gangue mineral (3.6wt%) in the concentrates. A 95% degree of liberation with d80 > 80 µm was obtained for chalcopyrite as the main copper mineral in the ore sample. The recovery rate and the grade in the concentrates were enhanced with increasing chalcopyrite particle size. Chalcopyrite particles with a d80 of approximately 100 µm were recovered at the early stages of the flotation process. The kinetic studies showed that the kinetic second-order rectangular distribution model perfectly fit the flotation test data. Characterization of the kinetic parameters indicated that the optimum granulation distribution range for achieving a maximum flotation rate for chalcopyrite particles was between the sizes 50 and 55 µm

The effect of noise and dust exposure on oxidative stress among livestock and poultry feed industry workers

Introduction: Simultaneous exposure to noise and dust may have detrimental health effects. This study was conducted to determine the effect of exposure to noise and dust on oxidative stress. Methods: In this cross-sectional study, 82 employees of two livestock and poultry feed factories in Golestan Province, Iran, were selected as the exposed group and 82 office workers were selected as the control group. Occupational noise and dust exposure were measured using a dosimeter, sampling pump, and vinyl chloride filter. Oxidative stress was determined by measuring the levels of malondialdehyde (MDA) and superoxide dismutase (SOD) in blood samples. T-tests, one-way analysis of variance, and multivariate linear regression were used to analyze the data. Results: The levels of MDA and SOD in the exposed group were significantly higher and lower than the control group (p < 0.001), respectively. The results showed the subgroup with both over the threshold dust and noise exposure had the highest MDA levels. The SOD level among those exposed to noise more than the recommended level, in the subgroup with more dust exposure, was significantly less than the subgroup with low noise exposure (p = 0.017). Conclusion: Noise and dust exposure probably increase the level of oxidative stress by increasing the level of lipid peroxidation (MDA) and reducing the level of antioxidant enzymes (SOD). © The Author(s) 2020

Projected future risk of leukemia and brain tumors from unnecessary brain CT scans: a multi-center study in Iran

Introduction: Computer Tomography (CT) scans can deliver a relatively high radiation dose to the patient, therefore radiation protection for this modality is paramount. The present study determined the frequency of no abnormality detected (NAD) brain CT scans and probability of cancer induction in different age groups and genders. Methods: In this study, brain CT reports were used to identify any findings as abnormality detected (AD) and others as NAD. Then probability of future leukemia and brain cancer was estimated for different age and gender groups. Results: On average, in 65% of the cases the results were NAD (56% and 76% among males and females, respectively). Among children, 79% of the reports were NAD. The total number of projected brain cancers was 1.8 and 1.3 for males and females, respectively. The number of projected leukemia cases was 0.75 and 0.7 for males and females, respectively. For pediatric patients, brain CT scans can lead to leukemia cases about 4.5 times more often than adults. Conclusion: Brain CT scans can lead to additional cases of brain cancer and leukemia. A significant fraction of brain CTs were NAD (non-pathologic) and could practically be replaced by other radiation-free imaging modalities, especially in pediatric and young patients