An innovative self-designed medium was packed in a bench-scale flotation column to study its influence on the flotation recovery of bauxite. Computational fluid dynamics (CFD) simulation was ...conducted to reveal the impact of the packing medium on the turbulent characteristics of collection zone in the column. Simulation results show that multilayer packing of the medium divides the collection zone into small units having different turbulent intensities, which is more suitable for flotation separation. The packing medium decreases the turbulence kinetic energy (from 1.08 × 10−2 m2/s2 to 2.1 × 10−3 m2/s2), turbulence eddy dissipation (from 3.71 × 10−2 m2/s3 to 9.8 × 10−3 m2/s3) and axial fluid velocity of fluid in the column. With three layers of packing, the recovery of Al2O3 increased by 2.11% and the aluminum to silicon content ratio of the concentrate improved from 5.16 to 9.72.
•REE extraction from GL was affected by acid type and concentration during MHTC.•H2SO4 performed better than HNO3 and HCl at the same concentration.•Nearly 100 % of REEs were extracted into biocrudes ...using 0.2 mol/L H2SO4.•The quality of hydrochar was improved with the increase in H2SO4 concentration.
Phytomining is a promising approach that uses hyperaccumulators to extract rare earth elements (REEs) from various substrates. Nonetheless, the processing and reutilization of REE hyperaccumulators after hyperaccumulation remains a challenge. In this study, the effects of acid type (HCl, H2SO4, and HNO3) and acid concentration (0.01 mol/L-0.2 mol/L) on REE extraction from grass leaves (GL) during microwave-assisted hydrothermal carbonization (MHTC) were investigated. The structural properties and thermal decomposition behavior of both the GL and the hydrochar produced from the MHTC process were characterized. It was found that at the same concentration, H2SO4 yielded the highest REE extraction efficiency due to the greater availability of hydrogen ions. Notably, the utilization of 0.2 mol/L H2SO4 led to the extraction of nearly 100 % of REEs from the GL into the resulting biocrudes. Concurrently, this also caused the degradation of amorphous hemicellulose and crystalline cellulose present in the GL, thereby enhancing the thermal stability of the resulting hydrochar. The physiochemical properties of the hydrochar were also influenced by acid type and acid concentration. The increase in acid concentration significantly contributed to the reduction in the volatile matter and ash content of the hydrochar. Using 0.2 mol/L H2SO4 as the reaction medium, MHTC resulted in a hydrochar with enhanced high heating value and energy densification. These results suggest that MHTC in the presence of an appropriate concentration of H2SO4 is an effective way to extract REEs and produce hydrochar from the GL.
In this investigation, the fine-grained bauxite ore flotation was conducted in a plate-packed flotation column. This paper evaluated the effects of packing-plates on recovering fine bauxite particles ...and revealed the fundamental mechanisms. Bubble coalescence and break-up behaviors in the packed and unpacked flotation columns were characterized by combining Computational Fluid Dynamics (CFD) and Population Balance Model (PBM) techniques. Flotation experiments showed that packing-plates in the collection zone of a column can improve bauxite flotation performance and increase the smaller bauxite particles recovery. Using packing-plates, the recovery of Al2O3 increased by 2.11%, and the grade of Al2O3 increased by 1.85%. The fraction of −20 μm mineral particles in concentrate increased from 47.31% to 54.79%. CFD simulation results indicated that the packing-plates optimized the bubble distribution characteristics and increased the proportion of microbubbles in the flotation column, which contributed to improving the capture probability of fine bauxite particles.
Saxifraga species are widely distributed in alpine and arctic regions in the Northern hemisphere. Highly morphological diversity within this genus brings great difficulties for species ...identification, and their typical highland living properties make it interesting how they adapt to the extreme environment. Here, we newly generated the chloroplast (cp) genomes of two Saxifraga species and compared them with another five Saxifraga cp genomes to understand the characteristics of cp genomes and their potential roles in highland adaptation. The genome size, structure, gene content, GC content, and codon usage pattern were found to be highly similar. Cp genomes ranged from 146,549 bp to 151,066 bp in length, most of which comprised 130 predicted genes. Yet, due to the expansion of IR regions, the second copy of rps19 in Saxifraga stolonifera was uniquely kept. Through sequence divergence analysis, we identified seven hypervariable regions and detected some signatures of regularity associated with genetic distance. We also identified 52 to 89 SSRs and some long repeats among seven Saxifraga species. Both ML and BI phylogenetic analyses confirmed that seven Saxifraga species formed a monophyletic clade in the Saxifragaceae family, and their intragenus relationship was also well supported. Additionally, the ndhI and ycf1 genes were considered under positive selection in species inhabiting relatively high altitudes. Given the conditions of intense light and low CO2 concentration in the highland, the products of these two genes might participate in the adaptation to the extreme environment.
The influence of conditioning on the flotation of pyrrhotite in the presence of chlorite was investigated through flotation tests, sedimentation tests, and X-ray photoelectron spectroscopy (XPS) ...analysis. The flotation results show that chlorite slimes dramatically impair the flotation of pyrrhotite. Sedimentation and flotation tests reveal that conditioning can effectively remove chlorite slimes from pyrrhotite surfaces, resulting in an enhanced flotation recovery of pyrrhotite. When mixed minerals were conditioned under the natural atmosphere, a faster conditioning speed and longer conditioning time decreased the flotation recovery of pyrrhotite. However, when mixed minerals were conditioned under a nitrogen atmosphere, a more intensive conditioning process provided better flotation results. XPS analyses illustrate that a faster conditioning speed and longer conditioning time under the natural atmosphere accelerates the oxidation of pyrrhotite, leading to a decrease in the flotation recovery of pyrrhotite.
The separation of carbon from fly ash significantly improves the potential end-us of combustion byproducts. Froth flotation is the most effective separation technique for ultrafine material. Diesel ...dosages, conditioning time, and impeller rotating speeds' influences on carbon flotation performance were studied. From flotation products, +25 and −25μm fractions were screened out to study their different flotation behaviors. At a given impeller speed, carbon recovery of +25μm fraction increased significantly from 38.46% to 74.22% over a range of diesel dosage from 0.5 to 4.5kg/t, while that of -25μm fraction was relatively constant at 85% over the same diesel dosage range. Morphologies and microstructures of coarse and fine carbon were studied by using scanning electron microscope. Porous structures of coarse carbon were observed. It's difficult for diesel droplets of several microns to penetrate the pores of coarse carbon particles, which increases diesel consumption. Increasing impeller speeds from 1200 to 1600rpm during conditioning improved the carbon recovery and separation efficiency of +25μm fraction by 79% and 110%, respectively, which significantly reduced diesel consumption. Flotation kinetic studies indicate that increasing impeller speeds during conditioning stage can improve the flotation rate constant and maximum carbon recovery for both +25 and −25μm fractions.
•Complicated porous structures were observed on coarse carbon via SEM.•Coarse carbon (>25μm) was difficult to be floated even with 4.5kg/t diesel.•Increase in CIS improves carbon recovery and separation efficiency of coarse carbon by 79% and 110%, respectively.•Increase in CIS reduces the collector consumption by nearly 80%.
The rapid development of advanced technologies has increased the demand for critical elements, such as Mn, Co, and Ni. For this work, a systematic study was conducted to develop a process for ...producing high-purity Mn, Co, and Ni products from an acid mine drainage (AMD). As major contaminants, Fe and Al in the solution were sequentially precipitated and eliminated by elevating the pH to around 4.00 and 6.50, respectively. After that, a pre-concentrated slurry containing 3,794 mg/L Mn, 59 mg/L Co, 127 mg/L Ni, and 300 mg/L Zn was obtained by collecting the precipitates formed in the pH range of 6.50 to 10.00. The pH of the pre-concentrated slurry was decreased to around 5.00 by adding HCl to re-dissolve Co, Ni, and Zn for further purification. At this pH, greater than 50% of Mn remained undissolved, and filtration of the undissolved material resulted in a product with around 30 wt.% Mn. Sodium sulfide was added into the re-dissolved solution to selectively precipitate Co, Ni, and Zn while remaining Mn in the solution. Almost 100% of Co, Ni, and Zn but only around 15% of Mn were precipitated using a sulfur to metal molar ratio of 1 at pH 4.00. The sulfide precipitate was calcined at 200 °C for 2 h and then completely dissolved in 1.2 M HCl. The critical elements existing in the dissolved solution were efficiently separated using a two-stage solvent extraction process. Ultimately, Co and Ni products with almost 94% and 100% purity were obtained by sulfide and alkaline precipitation, respectively.
Although the regulatory role of cognitive reappraisal in negative emotional responses is widely recognized, this reappraisal's effect on acute saliva secretory immunoglobulin A (SIgA), as well as the ...relationships among affective, immunological, and event-related potential (ERP) changes, remains unclear. In this study, we selected only people with low positive coping scores (PCSs) as measured by the Trait Coping Style Questionnaire to avoid confounding by intrinsic coping styles. First, we found that the acute stress of viewing unpleasant pictures consistently decreased SIgA concentration and secretion rate, increased perceptions of unpleasantness and amplitude of late positive potentials (LPPs) between 200-300 ms and 400-1000 ms. After participants used cognitive reappraisal, their SIgA concentration and secretion rate significantly increased and their unpleasantness and LPP amplitudes significantly decreased compared with a control condition. Second, we found a significantly positive correlation between the increases in SIgA and the decreases in unpleasantness and a significantly negative correlation between the increases in SIgA and the increases in LPP across the two groups. This study is the first to demonstrate that cognitive reappraisal reverses the decrease of SIgA. In addition, it revealed strong correlations among affective, SIgA and electrophysiological changes with convergent multilevel evidence.
PDF
