Acid mist formation in the electrowinning of copper

The formation of acid mist in the electrowinning of copper can result in a health hazard if the concentrations of the acid mist is too high. A study was carried out in a model electrowinning bath where the gas generation in an electrowinning bath was simulated by controlled gas injection. The breakup of the bubbles at the free surface controlled the mechanism for acid mist formation. The results showed that the bubble size and concentration played an important part in determining the droplet size and density that formed the acid mist. The amount of acid mist formed for different bubble concentration showed that the acid mist concentration above a model of the electrowinning bath decreases exponentially with distance from the bath surface. However, fine bubbles resulted in fine acid mist gives rise to droplets that can be carried away by the gas generated. The study identified means of reducing the acid mist concentration without the need to install complex gas cleaning and isolation equipment

Circular economy: A sustainable management strategy for rare earth elements consumption in Australia

Rare earth elements (REEs) are a major constituent of many advanced materials in the information and telecommunication industries, as well as the renewable and energy efficiency sectors. REEs are enablers of speed, performance, durability, and low carbon emissions in these industries. They are required in everyday applications because of their unique chemical and physical properties. Given the rise in environmental concerns and consequent demand for REEs and the limited locations where REEs can be sourced, there is a very high risk of supply disruption. Despite the threat of REE supply risk and its environmental and economic significance, an in-depth examination of the environmental impact and benefits of sustainable consumption of these metals in Australia, as in many other parts of the world, holistically and systematically is lacking, particularly regarding improvement in resource efficiency strategies. Most previous work on REEs has focused either on the politico-economic conflicts over supply and distribution, or the environmental and social impacts of its production and has not holistically examined this problem, as a system. This paper provides a review of REEs' sustainable consumption in Australia. The study highlights Circular Economy (CE) as a scientifically plausible picture of sustainable management strategy to help address the adverse impacts of resource (REEs) shortages while achieving maximum environmental benefits. It provides answers to how sustainable are the current strategies of REEs consumption and how this can be enhanced from a CE perspective. A comprehensive CE framework was developed, followed by an illustrative example of CE as a tool for sustainability management and a practical implementation strategy to close the material loop and improve resource efficiency

Improving gold recovery from a refractory ore via Na₂SO₄ assisted roasting and alkaline Na₂S leaching

Gold recovery from refractory gold ores with controlled roasting remained well below 80%. Na2SO4 was added in an O-2-enriched single stage roasting of a refractory gold ore to improve its gold recovery. Changes in physicochemical properties of the calcines suggested that this reduced the sintering as well as facilitated the formation of pores and a water soluble phase within the calcine. Thermodynamic analysis and leaching results demonstrated that Na2S solutions could effectively remove Sb species from the calcine. An extraction process that includes Na2SO4 assisted roasting and alkaline Na2S leaching is shown to be able to achieve a gold recovery of over 95% from the refractory ore

Green Synthesis of Carbon Nanospheres for Enhanced Electrochemical Sensing of Dopamine

The detection of dopamine (DA) has received enormous attention since it is widely recognized as an important neurotransmitter associated with nerve signaling and some diseases. In this work, glucose-derived carbon nanospheres (CNs) are synthesized by the green hydrothermal approach and are served to modify electrodes for the detection of DA. The CNs were successfully synthesized and were investigated in detail by various characterization technologies. The CNs modified glassy carbon electrode (CNs/GCE) exhibits better electrochemical sensing performance with a wide linear range of 0.05–1600 μM and a low limit of 8.3 nM for determination of DA, as compared with the modified electrodes reported previously. The CNs/GCE was successfully applied to detect DA in human serum samples, which makes it promising for a variety of biomedical applications. More importantly, this work shows a novel green and simple strategy for the development of cost-effective and high-performance sensing materials, which provides more opportunities for design of electrochemical sensors with future capabilities of mass production in practical applications

「医療的ケア」基本研修修了者の就職後の動向に関する調査 : アンケートから見えてくるもの

Two lab-scale wetland systems were studied for the removal of dissolved Cu, Mn, Fe, Pb and Zn. Vegetated with Typha domingensis, each system consisted of two units, a vertical and a horizontal flow wetland column, which were filled with either crushed sea shell grits or composted green waste as main media. A synthetic acidic wastewater was prepared by dissolving H2SO4, Pb(CH3COO)2, MnCl2, FeSO4, CuSO4 and ZnSO4 in a distilled water. As it passed through each column, metal concentrations, pH and conductivity were monitored. The pH value of the wastewater increased in the shell grit columns, where dissolved metals were almost completely (>99%) removed. In the wetland columns filled with the green waste, the average percentage removals were 90, 77, 27, 98 and 75% for Cu, Mn, Fe, Pb and Zn, respectively. Scanning electron microscopy and energy-dispersive spectroscopy (SEM-EDS) analysis showed that the surface characteristics of the shell grits remained largely unchanged before and after being used in the columns; but the mass compositions of carbon increased, whereas calcium and oxygen decreased. Infrared spectroscopy (IR) and X-ray diffraction (XRD) were used to further analyse the chemical compositions and functional groups of the surfaces of the shell grits

The MALATANG Survey : Dense Gas and Star Formation from High Transition HCN and HCO+ maps of NGC253

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. © 2020 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.To study the high-transition dense-gas tracers and their relationships to the star formation of the inner $\sim$ 2 kpc circumnuclear region of NGC253, we present HCN $J=4-3$ and HCO$^+ J=4-3$ maps obtained with the James Clerk Maxwell Telescope (JCMT). With the spatially resolved data, we compute the concentration indices $r_{90}/r_{50}$ for the different tracers. HCN and HCO$^+$ 4-3 emission features tend to be centrally concentrated, which is in contrast to the shallower distribution of CO 1-0 and the stellar component. The dense-gas fraction ($f_\text{dense}$, traced by the velocity-integrated-intensity ratios of HCN/CO and HCO$^+$/CO) and the ratio $R_\text{31}$ (CO 3-2/1-0) decline towards larger galactocentric distances, but increase with higher SFR surface density. The radial variation and the large scatter of $f_\text{dense}$ and $R_\text{31}$ imply distinct physical conditions in different regions of the galactic disc. The relationships of $f_\text{dense}$ versus $\Sigma_\text{stellar}$, and SFE$_\text{dense}$ versus $\Sigma_\text{stellar}$ are explored. SFE$_\text{dense}$ increases with higher $\Sigma_\text{stellar}$ in this galaxy, which is inconsistent with previous work that used HCN 1-0 data. This implies that existing stellar components might have different effects on the high-$J$ HCN and HCO$^+$ than their low-$J$ emission. We also find that SFE$_\text{dense}$ seems to be decreasing with higher $f_\text{dense}$, which is consistent with previous works, and it suggests that the ability of the dense gas to form stars diminishes when the average density of the gas increases. This is expected in a scenario where only the regions with high-density contrast collapse and form stars.Peer reviewe

Breakup of a flow-focused emulsion jet for the production of matrix-structured microcapsules

To achieve a better control of particle performances, significant research efforts have been directed toward the production of structured particles with a very narrow size distribution, or monodisperse “designer” particles. This paper presents a method for the production of monodisperse microspheres with a matrix structure. The technique is based on the application of flow focusing to the breakup of an emulsion jet in a liquid environment using an in-house designed and fabricated macroscopic device. Through the variation of flow conditions, the device is capable of producing matrix-structured monodisperse microcapsules in a size range of 20–200 µm

Application of flow-focusing to the break-up of an emulsion jet for the production of matrix-structured microparticles

Powder behaviour and performances are intimately related to particle attributes defined by the size, shape and structure of the individual particles making up the powder. The heterogeneous nature of the vast majority of powders reflected in the broad distribution of these particle attributes gives rise to the well-known difficulties in the prediction of powder behaviours. To achieve a better predictability and ultimate control of the performances, significant research efforts have recently been made towards the production of particles with controlled attributes, i.e. structured particles with a very narrow size distribution. This paper presents a new method for the production of monodisperse matrix-structured microcapsules using a simple in-house designed and fabricated macroscopic flow cell. The method combines flow-focusing with laminar jet break-up of a water-in-oil emulsion jet in a bulk water phase that produces monodisperse water-in-oil-in-water dispersion templates. The templates are then converted into solid microcapsules with a matrix structure by solvent evaporation. Results presented in the paper confirm a transition of flow regime from jetting to dripping when the outer to inner flow rate ratio reaches a critical value, accompanied by an increase in the size of the resultant droplets from the break-up. Importantly, the transition imposes a limit to the smallest size of monodisperse droplets each flow cell can produce through flow-focusing. The smallest monodisperse microcapsules produced from the flow cell used in this study through flow-focusing are 20μm in diameter

Uniformity of particles from laminar jet break-up

Many applications such as particulate drug delivery for targeting or controlled release require particles to be uniform in size. Much of the recent attention has been attracted to the production of particle with a narrow particle distribution. Laminar jet break-up represents one of the easiest methods for production of uniformly-sized particles from liquid feeds. However, while it is generally acknowledged that particles produced by laminar jet break-up do have a relatively narrow particle size distribution, no quantitative results seem to appear in the open literature on the size distribution in relation to the operating conditions. This paper attempts to quantify the influences of material properties and process variables on the particle size distribution from a laminar jet break-up process