方孔多孔板水力空化杀灭大肠杆菌的实验研究

旋转型水力空化反应器因其空化强度大,空化率高,已被广泛应用于杀菌消毒,污水处理等工业领域。文章提出一种弧形转子,通过数值计算分析弧形转子与原转子在不同转速下反应器内部空化性能,分析定子与转子之间的相互作用,研究改变弧形转子叶片入口安装角对反应器内部空化性能的影响。结果表明,在不同转速下,弧形转子均极大提高反应器内部空化强度,提高空化率。转子区域,空化发生于转子叶片吸力面,与低压区相对应;定子区域,转子叶片转过定子盲孔时,对流体进行强剪切,盲孔内部与进出口分离区压力降低涡量增大,发生剪切空化以及涡空化。增大叶片入口安装角度可以极大增加空化强度,提高反应器性能。

     

单频超声和双频复合超声的空化效应实验研究

从超声电功率、超声作用时间和溶液温度来研究超声的空化效应,采用碘化钾溶液中碘的释放量来测定超声的空化产额,研究结果表明：在相同的电功率输入情况下,双频复合超声（25kHz/40kHz）释放碘的量远大于单频25kHz超声和单频40kHz超声释放的碘的量,双频复合超声的空化产额高于单频超声。     

Degradation of alachlor in aqueous solution by using hydrodynamic cavitation

Samples of zirconium(IV)iodotungstate have been synthesized under varying mixing order and ratios of aqueous solution of potassium iodate, sodium tungstate and zirconium oxychloride at pH 1. A tentative formula was proposed on the basis of chemical composition, FTIR and thermogravimetric studies. The material shows a capacity of 0.68 meq g⁻¹ (for K⁺) which can be retained up to 200 °C. pH titration data reveal its monofunctional behavior. The distribution coefficient values of metal ions have been determined in various solvent systems. A number of important and analytically difficult quantitative separations of metal ions have been achieved using columns packed with this exchanger. In order to demonstrate practical utility of this material, Hg²⁺ and Pb²⁺ have been selectively separated and determined in the synthetic mixtures. Assay of Al³⁺ and Mg²⁺ in commercial tablets and analysis of lead in the standard reference material have also been attempted.     

Degradation of alachlor in aqueous solution by using hydrodynamic cavitation

The degradation of alachlor aqueous solution by using hydrodynamic cavitation was systematically investigated. It was found that alachlor in aqueous solution can be deomposed with swirling jet-induced cavitation. The degradation can be described by a pseudo-first-order kinetics and the degradation rate was found to be 4.90 × 10⁻² min⁻¹. The effects of operating parameters such as fluid pressure, solution temperature, initial concentration of alachlor and medium pH on the degradation rates of alachlor were also discussed. The results showed that the degradation rates of alachlor increased with increasing pressure and decreased with increasing initial concentration. An optimum temperature of 40 °C existed for the degradation rate of alachlor and the degradation rate was also found to be slightly depend on medium pH. Many degradation products formed during the process, and some of them were qualitatively identified by GC–MS.     

Investigation of the possibility of copper recovery from the flotation tailings by acid leaching

The flotation tailings pond of the Bor Copper Mine poses a great ecological problem not only for the town of Bor but also for the surrounding soils and watercourses. Since the old flotation tailings contain about 0.2% of copper on the average, we investigated their leaching with sulphuric acid in the absence and presence of an oxidant. The aim was to determine the leaching kinetics of copper and iron as affected by various factors such as: the pH value of the leach solution, stirring speed, pulp density, particle size, concentration of ferric ions, temperature and time for leaching. The average copper and iron recovery obtained was from 60% to 70% and from 2% to 3%, respectively. These results indicate that the old flotation tailings pond represents an important source of secondary raw material for the extraction of copper and that it should be valorized rather than land reclamation. At the end of the paper, a mechanism of dissolution of copper and iron minerals from the tailings was described.     

Formation of hydrogen peroxide by galena and its influence on flotation

The formation of hydrogen peroxide (H₂O₂), an oxidising agent stronger than oxygen, during the grinding of galena (PbS) was examined. It was observed that galena generated H₂O₂ in the pulp liquid during wet grinding and also when the freshly ground solids were placed in water immediately after dry grinding. The generation of H₂O₂ during either wet or dry grinding was thought to be due to a reaction between galena and water, when the mineral surface is catalytically active, to produce OH free radicals by breaking down the water molecule. It was also shown that galena could generate H₂O₂ in the presence or absence of dissolved oxygen in water.The concentration of H₂O₂ formed increased with decreasing pH. The effects of using mixtures of pyrite or chalcopyrite with galena were also investigated. In pyrite–galena mixture, the formation of H₂O₂ increased with an increase in the proportion of pyrite. This was also the case with an increase in the fraction of chalcopyrite in chalcopyrite–galena mixtures. The oxidation or dissolution of one specific mineral rather than the other in a mixture can be explained better by considering the extent of H₂O₂ formation rather than galvanic interactions. It appears that H₂O₂ plays a greater role in the oxidation of sulphides or in aiding the extensively reported galvanic interactions. This study highlights the necessity of further study of electrochemical and/or galvanic interaction mechanisms between pyrite and galena or chalcopyrite and galena in terms of their flotation behaviour.     

用碘释放法研究双束脉冲超声辐照的空化产率增强效应

本文首次采用碘释放法发现双束脉冲超声辐照的空化产率增强效应。这一发现无疑对声空化效应的基础研究和声化学技术发展具有重要的意义。     

Influence of impeller speed and cell volume on coal flotation performance in a self-aerating flotation machine

The effect of impeller speed and cell volume on batch coal flotation performance in a self-aerating flotation machine is studied in the present investigation. Factorial designed experiments are carried out to establish the relationships between the manipulated variables (impeller speed, and cell volume, and their interactions) with the separation indicators (yield, ash, combustible recovery and entrained water recovery). Correlation coefficient values are used to select the best fit model, and an analysis of variance to identify the statistically significant components of the model. The results indicated that both the impeller speed and cell volume significantly influence the performance of coal flotation. Further, the influence of these variables and their significance is discussed by flotation rate constant.     

旁通装置控制离心泵空化特性的数值模拟与试验

为了研究旁通水路对离心泵空化性能的影响规律,以一台比转速为32的低比转速离心泵为研究对象,在蜗壳第八断面靠进口侧位置处至吸入段搭建一旁通管路.采用修正的SST k-ω湍流模型和Kubota空化模型,在不同空化数下,对原型泵和带有旁通水路的离心泵进行三维非定常数值模拟,并同试验结果进行对比.结果表明:低比转速离心泵在搭建...     

Novel application of depressant sodium mercaptoacetate in flotation separation of chalcopyrite and pyrite

The development of flotation reagents with high selectivity and strong depression ability is of great significance in the efficient enrichment of copper sulfide ores. In this work, a new depressant, sodium mercaptoacetate (SMA) has been explored for the flotation separation of chalcopyrite and pyrite, and the depression mechanism of SMA was studied by Fourier Transform Infrared spectrometer (FTIR), adsorption tests, local electrochemical impedance spectroscopy test (LEIS), Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS). Micro-flotation tests showed that SMA strongly depresses pyrite in the pH range of 6–10. When the dosage of SMA is 2.5 × 10⁻⁵ mol/L, the dosage of SBX is 1 × 10⁻⁵ mol/L, and pH = 6.5, the concentrate with a Cu grade of 31.93% and chalcopyrite recovery of 85.97% can be obtained, in which the pyrite recovery was only 4.18%, respectively. The strong chemical adsorption between SMA and Fe atomic sites exposed on the surface of pyrite reduces the hydrophobicity of pyrite and hinders the adsorption of SBX. In comparison, SMA has less adsorption on the surface of chalcopyrite and hardly affects the further adsorption of SBX. It was shown that SMA could be used as an effective depressant for pyrite in the flotation separation of chalcopyrite and pyrite.     

Activation mechanisms of apatite by purifying reagent polyacrylamide for backwater from mineral processing in flotation of rare earths

This study revealed activation mechanisms of apatite by polyacrylamide (PAM) during flotation of rare earth minerals in Bayan Obo Ore. This activation leads to high phosphorus content in rare earth concentrate. Ultraviolet (UV) absorption measurements show that adsorption of PAM on the surfaces of apatite and rare earths follows a pseudo-second-order reaction kinetic model. The isothermal adsorption process follows the Freundlich adsorption model, indicating that the adsorption of PAM on apatite is a multi-layer, non-uniform process, that is, physical and chemical adsorption occurs simultaneously. The measured zeta potential shows that under weakly alkaline conditions, amide groups with a negative charge are adsorbed on the surface of apatite, increasing the electronegativity, so that the potential is shifted negatively; however, the negative shift of the potential on the surface of rare earths is insignificant. Fourier transform infrared (FT-IR) test and X-ray photoelectron spectroscopy (XPS) results imply that PAM is chemically adsorbed on the surface of apatite, while 506E undergoes stronger chemical adsorption than PAM on the surface of rare earth minerals. It is found that multi-layer, non-uniform adsorption of PAM combining physical and chemical adsorption occurs on the surface of apatite and the process is dominated by physical adsorption: the adsorption of PAM on surfaces of apatite is stronger than that on the surface of rare earth minerals. Such adsorption activates the apatite, causing it to float during the flotation of rare earths, which is the reason for the high phosphorus content in the rare earth concentrate.     

Comparison of attachment process of particles to air and oily bubbles in flotation

The attachment between particles and bubbles is a very important basic unit for mineral flotation. In the present study, methylation processing for glass spheres with trimethylchlorosilane was used to prepare particles with different surface hydrophobicity, and a visualization setup was assembled based on high-speed camera technology to investigate the dynamic attachment process of particles onto air/oily bubbles. More importantly, the difference in the attachment process between particles and air/oily bubbles was successfully quantified with the software Image Pro Plus 6.0. It was found that the wetting film ruptured at about 36 ms during the attachment between the hydrophobic glass sphere M2 and air bubbles, while it occurred at about 28 ms during the attachment between M2 and oily bubbles. Moreover, the formed three-phase contact line between hydrophobic particles and oily bubbles was larger than that between hydrophobic particles and air bubbles, suggesting a more stable attachment of the former. In contrast, no successful attachment of the hydrophilic glass sphere M0 onto air or oily bubbles was observed. These findings strongly demonstrated that oily bubbles had both strong collecting power and excellent selectivity for hydrophobic particles in flotation. This study improved the understanding of the difference between oily-bubble and conventional flotations.     

Understanding of attachment efficiency and induction time between bubbles and pyrite particles in flotation

The fundamental flotation models are useful for understanding flotation mechanisms. However, these models cannot be used for design and optimization of flotation circuits because it is very difficult to determine induction times experimentally during flotation despite using advanced high-speed cameras. Thus, there is a need to develop the model that can be used for practical applications, which is the main objective in this work. The developed models were successful in predicted P_a (attachment efficiency) and t_i (induction time) at various chemical conditions. The values of P_a (attachment efficiency) were strongly affected by particle size, collector concentration and pulp pH while the values of t_i (induction time) were affected by particle size and collector concentration and the values of k (flotation rate constant) were affected by collector concentration only. It means that P_a is much more sensitive than t_i and k to detect the changes in the flotation experimental conditions. The slopes of t_i vs P_a functions were larger at different particle sizes than those at different collector concentrations, demonstrating that the effect of particle size was more dominant than the effect of collector concentration on P_a. This paper demonstrated that understanding of P_a is essential for better analysing flotation mechanisms.     

Estimating the electrochemical reactivity of pyrite ores-their impact on pulp chemistry and chalcopyrite flotation behaviour

Prudent control of ore pulp chemistry via parameters such as redox potential (Eh), dissolved oxygen (DO) and pH, can markedly improve the flotation recovery, grade and selectivity of sulphide minerals. In this paper, the electrochemical reactivities of two pyrite minerals and their impact on chalcopyrite flotation are investigated using oxygen demand test and froth flotation. Changes in the surface chemistry/speciation are also investigated using X-ray photoelectron spectroscopy (XPS) and EDTA extraction technique. The oxygen demand test shows that the different pyrite ores display significantly different electrochemical reactivity. Furthermore, continuous aeration of the pulp reduces the reactivity of the pyrite ores. Solution and surface analysis results suggest the formation of hydroxide surface coatings on the pyrite surface as aeration progresses, preventing or minimising further oxidative reactions from taking place in the pulp. Flotation results showed that the flotation response of chalcopyrite is influenced by the pulp DO/Eh, and therefore the type and reactivity of the pyrite associated with it.     

Root cause analysis of the fracture of a sonar window caused by hydrostatic,hydrodynamic, and transient forces around a ship

Sonar systems are installed in naval vessels to inspect objects in the sea. When the system is installed at the bulbous bow of the ship, it can be vulnerable to fractures in rough seas due to hydrostatic and hydrodynamic forces, such as fluid-induced forces, and transient forces, such as slamming and collision with submerged foreign objects. In this paper, root causes analysis (RCA) of the fracture of a sonar window of a typical naval vessel was performed. To identify the root causes of the fracture, a numerical analysis was performed of the stress distribution on a sonar window under various extreme conditions. The results of the analysis, together with hypotheses of the causes of the fracture, are presented. The results of the analysis were verified by measuring the stress on the sonar window under typical sailing conditions of ships. The RCA demonstrated that buckling in response to the hydrostatic forces applied under the typical operating conditions of a water management system (WMS), in addition to excessive slamming, can cause a sonar window to fracture. Based on this RCA, corrective actions to prevent sonar window fractures include changing the material of the window and the operating conditions of the WMS.     

DEM simulation of single bubble flotation: Implications for the hydrophobic force in particle–bubble interactions

A 3D Discrete Element Method simulation model for a single bubble was developed in order to investigate the capture of hydrophobic particles. The bubble was considered stationary at the centre of the working space. Particle–particle and particle–bubble contacts were simulated using a linear spring-dashpot model. Gravitational, buoyancy, drag and hydrophobic forces were taken into account. The hydrophobic force was estimated through a single exponential decay law which depends on a pre-exponential parameter K and a decay length λ. It was observed that when λ was less than 10 nm, the number of the particles that were collected was independent of the strength of the hydrophobic force. In contrast, for values of λ within the range of 10–500 nm, the capture efficiency increased significantly with the strength of the hydrophobic force and λ. We have also demonstrated how these two parameters affect the particle trajectory around the bubble and thus produce a significant difference in particle collection when the strength and range of the hydrophobic force were varied.     

The utilization of tamarind seed gum as a novel dolomite depressant in the selective flotation of apatite from dolomite

In this study, the separation of apatite from dolomite was first investigated by using tamarind seed gum (TSG) to depress the flotation of dolomite in sodium oleate (NaOL) collector system. The effects of pH and flotation reagents concentration were studied, and the results indicated that TSG could strongly depress the dolomite floatability rather than apatite floatability. A satisfactory separation effect was realized when pH was 9.0, TSG dosage was 10 mg/L and NaOL dosage was 40 mg/L, at which the recovery of single apatite and dolomite was 80.28 % and 3.46 % respectively, and the grade of P₂O₅ and the recovery of P₂O₅ of the concentrate was 35.86 % and 76 % respectively in mixed ore flotation experiments. To reveal the adsorption mechanism, the flotation reagents adsorption morphology, adsorption type, and adsorption site were analyzed through AFM images, zeta potential measurements, FT-IR spectra, and XPS spectra, respectively. It was found that TSG was adsorbed on apatite by hydrogen bond while adsorbed on dolomite by chemical bond. Hydrogen bond was weaker than chemical bond, thus NaOL could still express the strong adsorption on apatite surface when TSG was used as depressant, while TSG could impede NaOL to be adsorbed on dolomite. Therefore, TSG selectively restrained the flotation of dolomite, achieving the separation. Furthermore, the XPS results uncovered that the Ca and Mg of dolomite were the main active sites that react with TSG.     

Adsorption mechanism of green efficient chelating poly-L-aspartic acid in flotation separation of brucite and dolomite

Green and efficient reagents have gained considerable attention in flotation research, where poly-L-aspartic acid (PASP) is an effective reagent to realize the flotation separation of brucite and dolomite. The effect of PASP on the flotation of brucite and dolomite and its mechanism were studied using flotation tests and modern detection methods. Microflotation tests show that PASP can considerably reduce the flotation recovery of dolomite in the Sodium dodecyl sulfonate (‘SDS) system, whereas it only slightly affects the flotation recovery of brucite. Under ‘SDS, PASP can selectively reduce the contact angle of dolomite but only slightly affect that of brucite. Furthermore, atomic force microscopy detection and zeta potential tests demonstrate that PASP can strongly adsorb on the dolomite surface, considerably changing its roughness and potential value but slightly affecting brucite. The infrared spectrum analysis shows that PASP is selectively strongly adsorbed on dolomite, causing strong and weak ‘SDS adsorption on the surfaces of brucite and dolomite, respectively. Moreover, X-ray photoelectron spectroscopy demonstrates that PASP strongly impacts the Ca site of dolomite, and selective chelation of Ca is a key factor in inhibiting dolomite flotation.     

Bezier函数型径向弯叶片对电站锅炉给水泵空化性能影响研究

为满足1000 MW超超临界电站锅炉给水泵大容量高参数的设计要求,通过CFD技术对锅炉给水泵叶轮的空化性能进行数值研究．提出一种基于Bezier 函数思想的径向弯叶片几何参数设计方法,并引入正弯叶片和反弯叶片两种叶片径向弯曲结构．结果表明：直叶片必需空化余量为22.8 m,与试验值的绝对误差仅为0.2 m,预测结果具有一定的精度;反弯叶片必需空化余量为22.3 m,空化性能最好;正弯叶片在叶片进口处压力面最先出现空泡,吸力面空化面积最大,而反弯叶片吸力面空化面积最小;3种径向弯叶片空化后在沿叶高中间流线相对位置0.2处叶片表面存在最大压差,可能导致叶片局部发生断裂．