scholarly journals A Hybrid Device for Enhancing Flotation of Fine Particles by Combining Micro-Bubbles with Conventional Bubbles

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 561
Author(s):  
Polyxeni K. Tsave ◽  
Margaritis Kostoglou ◽  
Thodoris D. Karapantsios ◽  
Nikolaos K. Lazaridis
Keyword(s):  
Ultrafine Particles ◽  
Fine Particles ◽  
Mining Industry ◽  
Water Electrolysis ◽  
Collision Efficiency ◽  
Hybrid Device ◽  
Flotation Cell ◽  
Wide Range ◽  
Micro Bubble ◽  
Ultra Fine Particles

Flotation in the mining industry is a very significant separation technique. It is known that fine and ultra-fine particles are difficult to float, leading to losses of valuable minerals, mainly due to their low collision efficiency with bubbles. Flotation of fine particles can be enhanced either by increasing the apparent particle size or by decreasing the bubble size. Literature review reveals that electroflotation resulted in higher recoveries of ultrafine particles as compared with dispersed-air flotation, because electrolytic bubbles are smaller in size. To this end, the best practical approach is to combine conventional air bubbles and micro-bubbles from water electrolysis. Therefore, the design, fabrication, and operation of a bench-scale micro-bubble generator through water electrolysis is proposed. Moreover, this electrolysis unit is adapted in a mechanical Denver-type flotation cell. The resulting hybrid flotation device is capable of producing bubbles within a wide range of diameters. The significance of this process is that micro-bubbles, attached tothe surface of fine particles, facilitate the attachment of conventional-sized bubbles and subsequently increase the flotation recovery of particles. Experimental flotation results so far on the hybrid device indicate the enhancement of fine particle recovery by approximately 10% with the addition of micro-bubbles.

Studies of copper selenide ultrafine particles by newly developed gas evaporation method

1990 ◽  
Vol 48 (4) ◽  
pp. 306-307
Author(s):  
Chihiro Kaito ◽  
Yoshio Saito
Keyword(s):  
Crystal Structure ◽  
Ultrafine Particles ◽  
Fine Particles ◽  
Production Method ◽  
Atmospheric Temperature ◽  
Copper Selenide ◽  
Quartz Boat ◽  
Selenium Vapor ◽  
Ar Gas ◽  
Ultra Fine Particles

The direct evaporation of metallic oxides or sulfides does not always given the same compounds with starting material, i.e. decomposition took place. Since the controll of the sulfur or selenium vapors was difficult, a similar production method for oxide particles could not be used for preparation of such compounds in spite of increasing interest in the fields of material science, astrophysics and mineralogy. In the present paper, copper metal was evaporated from a molybdenum silicide heater which was proposed by us to produce the ultra-fine particles in reactive gas as shown schematically in Figure 1. Typical smoke by this method in Ar gas at a pressure of 13 kPa is shown in Figure 2. Since the temperature at a location of a few mm below the heater, maintained at 1400° C , were a few hundred degrees centigrade, the selenium powder in a quartz boat was evaporated at atmospheric temperature just below the heater. The copper vapor that evaporated from the heater was mixed with the stream of selenium vapor,and selenide was formed near the boat. If then condensed by rapid cooling due to the collision with inert gas, thus forming smoke similar to that from the metallic sulfide formation. Particles were collected and studied by a Hitachi H-800 electron microscope.Figure 3 shows typical EM images of the produced copper selenide particles. The morphology was different by the crystal structure, i.e. round shaped plate (CuSe;hexagona1 a=0.39,C=l.723 nm) ,definite shaped p1 ate(Cu5Se4;Orthorhombic;a=0.8227 , b=1.1982 , c=0.641 nm) and a tetrahedron(Cu1.8Se; cubic a=0.5739 nm). In the case of compound ultrafine particles there have been no observation for the particles of the tetrahedron shape. Since the crystal structure of Cu1.8Se is the anti-f1uorite structure, there has no polarity.

scholarly journals Landfill air pollution by ultrafine and microparticles in case of dry and windless weather conditions

Detritus ◽  
2020 ◽  
pp. 139-146
Author(s):  
Emília Hroncová ◽  
Juraj Ladomerský ◽  
Denisa Ladomerská
Keyword(s):  
Ultrafine Particles ◽  
Large Scale ◽  
Particle Number ◽  
Fine Particles ◽  
Weather Conditions ◽  
Municipal Waste ◽  
Dust Particles ◽  
Particle Sizer ◽  
Ultra Fine Particles ◽  
Surprising Finding

In the present article we give the results for ultra-fine particles and microparticles at a landfill of municipal waste, taking into consideration various factors. The landfill is a large-scale source of dust. There is little knowledge in terms of fractional composition of dust particles. We have performed concentration measurements of the number of ultrafine (10 to 100 nm) and microparticles (0.1 to 10 μm) in the field conditions of the municipal waste landfill using the TSI Technique (Optical particle sizer 3330 and Nanoscan SMPS nanoparticle sizer 3919). The particle number concentration in the atmosphere in case of dry and windless weather conditions at the landfill was in the range of about 2,500 to 5,500 of ultrafine particles per cm3. The mass concentrations of the microparticles was in the range of 29 to 163 μg.m-3 (assuming ρ=1 g.cm-3). There was an evident trend of increase of concentration of the ultrafine particles and microparticles in the lower location of the landfill occuring in the case of dry and windless weather conditions. The surprising finding was that passing haulage vehicles and in particular the operation of the compactor increase the mass concentration of microparticles, but they do not increase the concentration of the number of microparticles or even of ultrafine particles.

Revisiting pulmonary acinar particle transport: convection, sedimentation, diffusion, and their interplay

2015 ◽  
Vol 118 (11) ◽  
pp. 1375-1385 ◽  
Author(s):  
Philipp Hofemeier ◽  
Josué Sznitman
Keyword(s):  
Ultrafine Particles ◽  
Fine Particles ◽  
Particle Sizes ◽  
Transport Dynamics ◽  
Inhaled Particles ◽  
Numerical Studies ◽  
Precise Understanding ◽  
Acinar Structure ◽  
Ultra Fine Particles ◽  
Local Deposition

It is largely acknowledged that inhaled particles ranging from 0.001 to 10 μm are able to reach and deposit in the alveolated regions of the lungs. To date, however, the bulk of numerical studies have focused mainly on micrometer-sized particles whose transport kinematics are governed by convection and sedimentation, thereby capturing only a small fraction of the wider range of aerosols leading to acinar deposition. Too little is still known about the local acinar transport dynamics of inhaled (ultra)fine particles affected by diffusion and convection. Our study aims to fill this gap by numerically simulating the transport characteristics of particle sizes spanning three orders of magnitude (0.01-5 μm) covering diffusive, convective, and gravitational aerosol motion across a multigenerational acinar network. By characterizing the deposition patterns as a function of particle size, we find that submicrometer particles [[Formula: see text] (0.1 μm)] reach deep into the acinar structure and are prone to deposit near alveolar openings; meanwhile, other particle sizes are restricted to accessing alveolar cavities in proximal generations. Our findings underline that a precise understanding of acinar aerosol transport, and ultrafine particles in particular, is contingent upon resolving the complex convective-diffusive interplay in determining their irreversible kinematics and local deposition sites.

scholarly journals Monitoring of Indoor Ultrafine Particulate Matter at the Sites of the Czech Armed Forces

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Eva KELLNEROVÁ ◽  
Zbyněk VEČEŘA ◽  
Josef KELLNER ◽  
Tomáš ZEMAN
Keyword(s):  
Ultrafine Particles ◽  
Fine Particles ◽  
Working Hours ◽  
Armed Forces ◽  
Ambient Air ◽  
World Health Organisation ◽  
World Health ◽  
Scanning Mobility Particle Sizer ◽  
Adverse Health Effects ◽  
Ultra Fine Particles

Ultrafine particles and nanoparticles in the air are evaluated as a risk factor for the development of respiratory and other healthsymptoms due to their inhalation from the ambient air. The Czech Army professionals are expected to have frequent presence in apolluted environment and regular exposure to air with increased concentration of airborne pollutants. The report evaluates the presenceof ultra-fine particles (in the range of about 7.6–299.6 nm) in rooms often used by soldiers during their working hours whenthey are not deployed. The purpose is to assess whether the presence of troops in these workplaces is safe and does not pose a riskof adverse health effects in itself. Testing took place in three military rooms (classroom 1, classroom 2 and exercise flight simulatorroom). Seven samples of air were analysed in time by the scanning mobility particle sizer in succession. Mean particle concentrationswere found at 1.79×104, 7.53×103 and 8.39×103 N·cm-3 for the classroom 1, classroom 2 and exercise flight simulator room.Conclusions of the research have shown that particle concentrations in the places of the Czech Army can reach values that borderthe immission limits stated by the World Health Organisation.

scholarly journals Large hemispheric difference in ultrafine aerosol concentrations in the lowermost stratosphere at mid and high latitudes

2021 ◽  
Author(s):  
Christina J. Williamson ◽  
Agnieszka Kupc ◽  
Andrew Rollins ◽  
Jan Kazil ◽  
Karl D. Froyd ◽  
...  
Keyword(s):  
Size Distribution ◽  
Ultrafine Particles ◽  
Fine Particles ◽  
Global Scale ◽  
Stratospheric Aerosol ◽  
Heterogeneous Chemistry ◽  
High Latitudes ◽  
Aircraft Emissions ◽  
Ultra Fine Particles ◽  
Ultrafine Aerosol

Abstract. The details of aerosol processes and size distributions in the stratosphere are important for both heterogeneous chemistry and aerosol-radiation interactions. Using in-situ, global-scale measurements of the size distribution of particles with diameters > 3 nm from the NASA Atmospheric Tomography Mission (ATom), we identify a mode of ultrafine aerosol in the lowermost stratosphere (LMS) at mid and high latitudes. This mode is substantial only in the northern hemisphere (NH), and was observed in all four seasons. We also observe elevated SO2, an important precursor for new particle formation (NPF) and growth, in the NH LMS. We use box modelling and thermodynamic calculations to show that NPF can occur in the LMS conditions observed on ATom. Aircraft emissions are shown as likely sources of this SO2, as well as a potential source of ultrafine particles directly emitted by, or formed in the plume of the engines. These ultra-fine particles have the potential to grow to larger sizes, and to coagulate with larger aerosol, affecting heterogeneous chemistry and aerosol-radiation interactions. Understanding all sources and characteristics of stratospheric aerosol is important in the context of anthropogenic climate change as well as proposals for climate intervention via stratospheric sulphur injection. This analysis not only adds to the, currently sparse, observations of the global impact of aviation, but also introduces another aspect of climate influence, namely a size distribution shift of the background aerosol distribution in the LMS.

Effect of Surfactant on Bubble Size and Air Holdup on Column Flotation

2017 ◽  
Vol 899 ◽  
pp. 71-76
Author(s):  
Angelica Silva Reis ◽  
A.M.R. Filho ◽  
G.R.L. Carvalho ◽  
Marcos Antonio de Souza Barrozo
Keyword(s):  
Bubble Size ◽  
Ultrafine Particles ◽  
Fine Particles ◽  
Bubble Column ◽  
Mining Industry ◽  
Good Alternative ◽  
Particle Collisions ◽  
Complex Process ◽  
Intermediate Size ◽  
Superficial Gas Velocity

Flotation is a complex process in which is present physicochemical and hydrodynamic phenomena. The flotation performance is related to the probability of bubble-particle collisions and stability of aggregate formed. The collision efficiency is a function of particle and bubble diameters. Currently one of the biggest challenges of the mining industry is the flotation of fine and ultrafine particles and a possible solution to increase the recovery of these fine particles is the use of bubbles with intermediate size (100-1000μm). Therefore, determining and controlling the bubble size is very important for further recoveries in the flotation of fine particles. It is known that the bubble size and air holdup are influenced by variations on the superficial gas velocity and by addition of surfactants. Thus this work aimed to study the effect of adding surfactants on bubbles formation. The results showed that the addition of surfactant was a good alternative to decrease bubble size and increase the air holdup in a bubble column. Three different surfactants had similar behavior on bubble size and holdup. It was possible to define the range of concentration values which are sufficient for forming bubbles with intermediate size and holdup within the range recommended for mineral flotation.

scholarly journals Use of Multi-Anionic Sodium Tripolyphosphate to Enhance Dispersion of Concentrated Kaolin Slurries in Seawater

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1085
Author(s):  
Williams Leiva ◽  
Norman Toro ◽  
Pedro Robles ◽  
Edelmira Gálvez ◽  
Ricardo Ivan Jeldres
Keyword(s):  
Rheological Properties ◽  
Fine Particles ◽  
Sodium Tripolyphosphate ◽  
Mining Industry ◽  
Chord Length ◽  
Water Recovery ◽  
Reflectance Measurement ◽  
Anionic Charge ◽  
Free Environment ◽  
The Impact

This research aims to analyze the impact of sodium tripolyphosphate (STPP) as a rheological modifier of concentrated kaolin slurries in seawater at pH 8, which is characteristic of copper sulfide processing operations. The dispersion phenomenon was analyzed through chord length measurements using the focused beam reflectance measurement (FBRM) technique, complementing size distributions in unweighted and square-weighted modes. The reduction of the rheological properties was significant, decreasing from 231 Pa in a reagent-free environment to 80 Pa after the application of STPP. A frequency sweep in a linear viscoelastic regime indicated that by applying a characteristic dosage of 0.53 kg/t of STPP, the pulp before yielding increases its phase angle, which increases its liquid-like character. Measurements of the chord length verified the dispersion of particles, which showed an apparent increase in the proportion of fine particles and a reduction of the coarser aggregates when STPP was applied. Measurements of the zeta potential suggested that the high anionic charge of the reagent (pentavalent) increases the electrostatic repulsions between particles, overcoming the effect of cations in seawater. The results are relevant for the mining industry, especially when the deposits have high contents of complex gangues, such as clays, that increase the rheological properties. This increases the energy costs and water consumption needed for pumping the tailings from thickeners to the tailing storages facilities. The strategies that allow for the improvement of the fluidity and deformation of the tailings generate slack in order to maximize water recovery in the thickening stages.

scholarly journals Design of 3D Additively Manufactured Hybrid Structures for Cranioplasty

Materials ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 181
Author(s):  
Roberto De Santis ◽  
Teresa Russo ◽  
Julietta V. Rau ◽  
Ida Papallo ◽  
Massimo Martorelli ◽  
...  
Keyword(s):  
Physical Models ◽  
Cranial Bone ◽  
Head Model ◽  
Rigid Sphere ◽  
Element Analysis ◽  
Aliphatic Polyesters ◽  
Hybrid Device ◽  
Wide Range ◽  
Hybrid Devices ◽  
Technical Solutions

A wide range of materials has been considered to repair cranial defects. In the field of cranioplasty, poly(methyl methacrylate) (PMMA)-based bone cements and modifications through the inclusion of copper doped tricalcium phosphate (Cu-TCP) particles have been already investigated. On the other hand, aliphatic polyesters such as poly(ε-caprolactone) (PCL) and polylactic acid (PLA) have been frequently investigated to make scaffolds for cranial bone regeneration. Accordingly, the aim of the current research was to design and fabricate customized hybrid devices for the repair of large cranial defects integrating the reverse engineering approach with additive manufacturing, The hybrid device consisted of a 3D additive manufactured polyester porous structures infiltrated with PMMA/Cu-TCP (97.5/2.5 w/w) bone cement. Temperature profiles were first evaluated for 3D hybrid devices (PCL/PMMA, PLA/PMMA, PCL/PMMA/Cu-TCP and PLA/PMMA/Cu-TCP). Peak temperatures recorded for hybrid PCL/PMMA and PCL/PMMA/Cu-TCP were significantly lower than those found for the PLA-based ones. Virtual and physical models of customized devices for large cranial defect were developed to assess the feasibility of the proposed technical solutions. A theoretical analysis was preliminarily performed on the entire head model trying to simulate severe impact conditions for people with the customized hybrid device (PCL/PMMA/Cu-TCP) (i.e., a rigid sphere impacting the implant region of the head). Results from finite element analysis (FEA) provided information on the different components of the model.

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