•The effects of curvature radius on the hydrocyclone are numerically studied.•The applicability of the mathematical model is verified.•Decreasing the curvature radius improves the stability of the inner flow field.•A smaller curvature radius reduces the amount of particle misplacement.An appropriate design of the inlet type has been proved to be an effective approach to improve the performance of a hydrocyclone. Until now, there is still no detail analysis on the mechanism underlying the flow control by the inlet type. In this paper, numerical simulation was conducted to investigate effects of curvature radius on the separation performance of the hydrocyclone with a tangent-circle inlet. The validity of the approach was verified by the reasonably good agreement between the predicted and measured results in terms of water velocities and particle partition curves. The simulating results were further analyzed in aspects of the flow field, pressure drop and separation performance. Results showed that a smaller curvature radius could increase the tangential velocity and the pressure gradient. Besides, the turbulence kinetic energy in the inlet section and the annular section are reduced by decreasing the curvature radius. Meanwhile, the symmetry of the inner flow field was improved by reducing the curvature radius. All these factors enhanced the radial regular distribution of particles in the inlet section and reduced influences of the short circuit flow on relatively coarse particles. Therefore, the classification precision was improved when using a tangent-circle inlet with a smaller curvature radius compared with base hydrocyclone.The effects of curvature radius on the flow field, the pressure drop and the separation performance are numerically studied. Decreasing the curvature radius is beneficial for enhancing the stability of the inner flow field and improving the separation precision.

•A new method (FP-EM) for hydrocyclone designs has been proposed and verified.•The feed flow rate is used as a parameter to estimate the method.•The optimum range of feed flow rate is deduced by the flow pattern.•The fitting equations are in good agreement with existing models.•The FP-EM method can be applied in hydrocyclone designs successfully.Existing design equations can hardly provide reliable guidance in hydrocyclone designs and give explanations for the selected optimum range. Therefore, a new method combined flow patterns and equation models (FP-EM) for hydrocyclone designs is proposed in this paper. The feed flow rate is used as a parameter to evaluate the FP-EM method. Results show that under a lower feed flow rate, the inner flow field is extremely unsteady, which is characterized by higher turbulence intensity and an unsteady air core. When the flowrate becomes extremely large, the value of the exponent n for the tangential velocity inside the free vortex region decreases. Furthermore, before flow field achieving stability, the separation accuracy is extremely low. In the optimum range, the separation efficiency and the accuracy increases with the increase of the feed flow rate, while the cut size decreases. Thus, for the φ50 mm hydrocyclone used in this study, the lower limit (15 L/min) can be determined by the flow field stability and the upper limit (55 L/min) is largely ascertained by energy consumption. Three power-type fitting equations are deduced in the optimum range to quantify the relationships between separation indexes (split ratio, pressure drop and cut size) and the flowrate. Correlation coefficients (R2 > 0.97) of three equations verify that equation models can predict the separation performance successfully. Therefore, all above results confirm that the FP-EM method is capable of providing an optimum range, quantifying the relationships between separation indexes and the feed parameter, and predicting separation performances.Download high-res image (261KB)Download full-size image

•The obtained TeO2 nanowires show a large surface-to-volume ratio.•Growth process of TeO2 nanowires is dominated by vapour-solid growth mechanism.•Sensitive and selective room temperature alcohol TeO2 nanowires gas sensor is demonstrated.TeO2 nanowires were synthesized by thermal evaporation of Te powders in air at ambient pressure. The crystal structure, morphology, and alcohol sensing properties of TeO2 nanowires were investigated. Structural characterizations showed that TeO2 nanowires with a tetragonal structure were approximately 70–200 nm in diameter and several hundreds of micrometers to 2 mm in length. No Au nanoparticles were observed at any ends of TeO2 nanowires, revealing that the growth process was dominated by the vapour-solid growth mechanism. Gas sensing measurements indicated that TeO2 nanowires with an n-type conduction showed a quick and reversible response to ethanol gas at room temperature. The response increased in the order of methanol > ethanol > propanol under the same conditions as well as with increasing alcohol gas concentration. The results demonstrate the feasibility of using TeO2 nanowires for sensing alcohol gases.

•Sulfur oxidation activity of A. ferrooxidans was promoted by PEG addition.•The passivation of chalcopyrite surface was caused by S0 and jarosite.•S0 deposited on the mineral surface was eliminated by the addition of PEG.•Cu extraction yield from chalcopyrite was increased by 1.19 times by PEG addition.Polyethylene glycol (PEG) was used as a catalyst to enhance chalcopyrite bioleaching with Acidithiobacillus ferrooxidans in shake flasks. The effects of PEG on the sulfur oxidation of A. ferrooxidans and on the process of chalcopyrite bioleaching were investigated. The morphology, main components and sulfur speciation of bioleached chalcopyrite surfaces were evaluated combining with XRD, SEM and XPS. It was demonstrated that addition of PEG could significantly improve the bioleaching of chalcopyrite. Furthermore, the results indicated that elemental sulfur and jarosite were the main components of the passivation layer during the bioleaching of chalcopyrite. PEG could promote the sulfur oxidation by A. ferrooxidans due to an increase in bacterial attachment, and therefore accelerate the biooxidation of elemental sulfur generated in leaching process. It was found that PEG eliminated inhibitory elemental sulfur from the chalcopyrite surface which could be the main reason for enhanced the leaching efficiency.

•Chitosan was used as a selective depressant in copper–molybdenum sulfides flotation​.•The results showed the selective adsorption of chitosan on chalcopyrite.•The depression mechanism of chitosan was studied by adsorption, FTIR spectra and ToF-SIMS.Chitosan, a natural biodegradable polymer, was studied as a selective depressant in copper–molybdenum sulfide separation by flotation. Although chitosan depressed both molybdenite and chalcopyrite in single mineral flotation, selective flotation was achieved during the flotation of molybdenum-bearing copper sulfide concentrate at pH 6; the recovery of molybdenum in the froth product was over 70% while the recovery of copper was less than 24%. Adsorption measurements showed that chitosan had a higher adsorption density on chalcopyrite than on molybdenite. FTIR and ToF-SIMS measurements were carried out to confirm the different degrees of interaction of chitosan with molybdenite and chalcopyrite and the results showed that chitosan mostly adsorbed on chalcopyrite via amide groups when both molybdenite and chalcopyrite were present in the suspension.