Pulp Phase Research Articles

Controlling a Flotation Cell at the Peak Air Recovery Point

Air recovery is the fraction of air that leaves the pulp phase of a flotation cell and reports to the concentrate. There is a peak in this quantity as cell parameters change, and experimental and test work suggests that this peak is associated with maximum recovery of valuable material. If this is the case, then a control system that can operate the cell at the peak air recovery (PAR) point will be of great value. Previous attempts at achieving this objective have used extremum-seeking control methods. In this paper, a simpler and faster method based on a model of the rate of change of the air recovery is proposed. It is shown that the method maintains the cell at PAR when disturbances to the systems are imposed.

Maximizing the recovery and throughput of a rougher flotation bank by improving the recovery of composite particles

With decreasing ore grades, the cost of mineral processing has been escalating due to the high costs associated with grinding larger volumes of ores for liberation. To minimize the embodied cost, mined ores are usually coarse ground for rougher flotation, in which much of the waste (or ‘dead’) rocks are removed before regrinding the rougher concentrate to obtain the final product. Thus, the feed to a rougher flotation bank frequently consists of coarse particles that are poorly liberated and, hence, are not hydrophobic enough to be collected by air bubbles in the pulp phase and survive the froth phase without being detached.In the present work, we explored the possibility of improving the flotation of composite particles using Super Collectors that can increase the water contact angles (θ) of the copper-bearing mineral grains well above 90°. The efficacy of this approach has been tested in laboratory flotation tests, followed by a series of simulations using a flotation model. The model has been derived from first principles using the surface forces in wetting films as kinetic parameters. The major input to the simulator was the liberation matrix (mij) of a flotation feed and the various operating parameters. The simulations were carried out to obtain the grade vs. recovery curves for a low-grade (0.24 %Cu) porphyry copper ore feed with d80 = 288 µm. The simulations were carried out using a Super Collector that can increase θ of the chalcopyrite grains to 150°. The grade vs. recovery curves obtained from the simulation showed that the Super Collector can substantially increase the recovery of composite particles over the case of using potassium amyl xanthate (PAX) as a collector at approximately 40 % shorter retention times. The simulation results also showed that Super Collectors help minimize bubble coarsening and hence contribute to improving the coarse particle recovery.

Double‐sensor conductivity probe applied in a flotation system

AbstractThis study proposed a new approach for measuring bubble size distribution, bubble mean diameter, Sauter mean bubble diameter, and gas holdup using a double‐sensor conductivity probe in an air/water two‐phase system bubble column. The results for the two‐phase system were compared and calibrated using analyses from bubble images taken by a digital camera from the side of the column wall. Good agreement was observed between the two techniques. The same double‐sensor conductivity was used in an air/water/solids three‐phase system. The conductivity probe captured the change in bubble dynamic behaviour inside the pulp phase; however, the presence of the solids made it more challenging to measure. As a result, the VisioFroth commercial package, using images taken from the top of the froth layer, could be used in conjunction with the double‐sensor conductivity probe to show the dynamic evolution of mineralized bubbles from the pulp zone to the froth zone in a flotation process.

Molecular interactions between thiolate collectors and non-ionic frothers in mixed monolayers at the air–water interface using a regular solution theory approach

Dithiophosphate (DTP) is classically used as a co-collector in sulfide mineral flotation to promote hydrophobicity on target particles. Notwithstanding the improved recoveries observed, DTP does not appear to behave as a conventional collector, since it has been shown that it does not adsorb onto certain sulfide mineral surfaces. Recent investigations have nevertheless indicated that when DTP does not adsorb onto the sulfide mineral surface, the presence of a non-ionic frother, such as an alcohol or polyglycol ether, activates a synergistic increase in pulp phase mineral recovery and bubble-particle attachment probability. In this paper, a regular solution approach is used to quantify the interactions between thiolate collectors and non-ionic frothers at the air–water interface, where no other methodology could demonstrate such interactions. Attractive interactions were observed between DTP and frothers, whereas no such interaction was observed between xanthate, a standard base metal sulfide collector. It is suggested that this is the first time that such interactions have been shown for the DTP-frother system and this may represent an important contribution to our understanding of the role of DTP reagents in the flotation process.

Role of hydrophobic fine particles in coarse particle flotation: An analysis of bubble-particle attachment and detachment

It is widely accepted that hydrophobic fine particles improve froth stability and thus increase the recovery of coarse particles in the froth phase. In fact, the presence of fine particles also enhances coarse particle recovery in the collection zone. It is not yet known what causes this, nor is it known how fine particles affect interactions between bubbles and coarse particles (collision, attachment, and detachment). In the present study, the role of hydrophobic fine particles in improving the recovery of coarse particles in the pulp phase was discussed from the perspective of bubble-particle interaction. Flotation tests of coarse particles with different fine particle contents were first carried out. The bubble collision-attachment test, bubble-particle aggregate stability test, and interaction force test were used to further explain the effects of fine particle coverage on bubble-particle interactions. The results show that the recovery of coarse particles increases as the fine particle content in the flotation feed increases. Although the presence of hydrophobic fine particles prevents the rupture of the liquid film and the formation of the contact line between bubble and coarse particle, it can also greatly increase contact angle hysteresis, increasing the maximum force required to pull coarse particle from the gas-liquid interface into the aqueous phase. Furthermore, the coverage of fine particles helps to improve the energy dissipation during the bubble collision and reduce the oscillation of the bubble-particle aggregates. As a result, the increase in coarse particle recovery in the presence of fine particles is due to the decrease in the detachment of the bubble-particle aggregate. The important findings of this study are expected to provide a basis for understanding the interaction between multiple particles and bubbles in actual flotation.

Multi-objective optimization of stirring tank based on multiphase flow simulation

Stirring tanks are regarded as pivotal equipment for solid-liquid suspension operations in industrial processes such as adsorption and crystallisation, and its performance is complex in relation to the pulp phase, structure and process conditions. However, the traditional design method for stirring tank structure is sophisticated and time-consuming, which greatly limits the design efficiency. To address the high cost and inefficiency of traditional design methods, this paper performed a multi-objective optimal design of stirring tank based on numerical simulation, surrogate model, NSGA-II, Entropy Weighting Method and Analytic Hierarchical Process. Firstly, the flow field state of stirring tanks with different structural dimensions and operating parameters was simulated with computational fluid dynamics (CFD), which was subsequently validated by Particle Image Velocimetry. Then, for the key parameters including stirring speed, stirrer diameter, stirrer height from the bottom and paddle pitch, experiments were designed using the Latin Hypercube method to establish a Kriging model based on the gained simulation data. Afterwards, the Pareto front was obtained from the optimization using NSGA-II with two objectives of stirring power and suspension uniformity. The result of Analytic Hierarchy Process and Entropy Weighting Method showed that the selected optimal solution can improve the suspension uniformity by 0.7 % while reducing power consumption by 48.3 % compared to the initial design.

The Electrochemical Response of Chalcopyrite and Galena to Degrading Water Quality

Water is used as a liquid medium as well as a means of transportation during mining operations. Flotation, in particular, is a water intensive process where water makes up about 80–85% of the pulp phase. Process water contains organic and inorganic species which accumulate as they are recycled. To avoid the treatment costs of removing these contaminants, many mining operations allow the quality of their water to degrade over time. When this water is introduced into flotation circuits, the pulp chemistry is altered. Ionic species that accumulate in recycled process water have been shown by previous studies to be especially deleterious to flotation performance. Such ions include Ca2+, Cu2+, Mg2+, Pb2+, SO42− and S2O32−, amongst others. The flotation sub-process of collector adsorption which is responsible for inducing hydrophobicity on valuable mineral surfaces may be influenced by water chemistry. Accumulating ionic species have been shown to hinder collector adsorption which may reduce recovery of valuable minerals to the concentrate. Consequently, degrading water quality may threaten the economic viability of mining operations that make use of closed water circuits. Electrochemical techniques such as mineral rest potentials can be used to monitor the impact of changing water quality on collector–mineral interactions. Microflotation was used to determine whether mineral floatability was affected by changing water quality. This study therefore aimed to investigate whether electrochemical techniques such as rest potential measurements can be used to predict flotation performance under changing water quality. No definable relationship was found between the rest potential differences and the microflotation initial recoveries, however, rest potential measurements did identify the negative impact that thiosulphate ions may have on flotation processes.

Predicting the recovery and grade of a rougher flotation circuit from liberation data

A flotation model has been validated against the survey data obtained from a copper rougher flotation circuit with a circulating load. The model was developed using the hydrophobic force as a kinetic parameter, which made it possible to use the contact angles of the free and composite particles as input parameters so that the model can predict both recoveries and grades. The model also recognizes the role of bubble coarsening in determining the froth phase recoveries and grades. The model predictions are in good agreement with the survey data. The size-by-size recovery curve as predicted from the model shows an optimum particle size range that is consistent with most of the operating data reported in the literature. The model suggests that the upper particle size limit may be determined by the instability of the froth phase rather than the turbulence in the pulp phase of a flotation cell.

Development of a flotation simulator that can predict grade vs. Recovery curves from mineral liberation data

Flotation is a kinetic process designed to separate mineral fines by control of hydrophobicity . In general, both the recovery and selectivity of a flotation process increase with contact angle. It is difficult, however, to model flotation kinetics using the thermodynamic parameter. In the present work, we consider flotation as heterocoagulation so that the bubble-particle interactions occurring in the pulp phase of a flotation cell can be modeled using the hydrophobic force as a kinetic parameter that can represent the role of contact angles in flotation. The pulp-phase model developed in this manner has been combined with a froth-phase model developed earlier by considering the effect of particles in film thinning kinetics and bubble coarsening (Park et al, 2018). The combined model has been used to develop a flotation simulator that can be used to construct grade vs . recovery curves from feed characteristics ( e.g ., mineral liberation and particle size) and various operating parameters. The simulator has been tested successfully against a set of bench-scale continuous flotation test results reported in the literature (dos Santos and Galery, 2018).

The new identity of cellulose pulp: A green silver nanoparticles support for highly efficient catalytic hydrogenation of 4-nitrophenol

The uniquely interconvertible transformation of cellulose pulp and paper shows great potential as smart materials for environment remediation. However, performing liquid-phase catalytic reactions involving hydrogenation steps under mild conditions and ambient temperature remains challenging. Herein, we report a facile and eco-friendly strategy to fabricate low-cost, highly effective, and stable pulp-supported silver nanoparticles (AgNPs/pulp). The pulp phase is used to maintain the high catalytic efficiency of the AgNPs/pulp catalyst, while the paper phase remains high stability as the filling material in the reaction column. The as-prepared AgNPs/pulp catalyst exhibits excellent catalytic activity toward NaBH4-mediated reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) with a turnover frequency of 605.1 h−1 and a k value of 24.9 × 10−3 s−1 at room temperature, which outperforms most of reported cellulose-supported catalysts. Impressively, the AgNPs/pulp catalyst shows outstanding durability during a continuous operation for 72 h. Such excellent performance can be attributed to the uniform dispersion of the AgNPs/pulp in solution and uniform distribution of Ag NPs on the fiber surface of cotton pulp, which greatly improve the accessibility of reactants and active sites as well as metal-support interactions. This work provides new insights into the understanding of catalytic hydrogenation of 4-NP, which could pave the way for rational design of novel cellulose-based catalysts for organic wastewater treatment.

Mechanical Flotation of Mineral Particles with an Underwater Speaker

ABSTRACT This paper aims to demonstrate a safe, non-chemical approach for improving the efficiency of froth flotation. Laboratory scale flotation tests for quartz particles of different sizes (< 20 µm, 20–38 µm, 38–75 µm, 75–106 µm, 106–150 µm, 150–212 µm) with an ether amine collector at different dosages were conducted in batch mode by using a bottom-driven mechanical flotation cell. An underwater loudspeaker was placed in the flotation pulp phase. The solids concentrations tested were 5% and 20% by weight. The results showed that acoustic sound (at 375 Hz and 77 decibels) increased the flotation recovery by at least 6% over a broad particle size range (i.e. 20–212 micron). The results also suggested applying acoustic sound in a flotation system can improve flotation recovery to a larger extent at a lower reagent dosage. An advantage of having the loudspeaker immersed in the pulp phase rather than in air above the flotation cell was the substantially reduced noise level. The present study provides a potential approach for improving flotation performance and reducing the chemical reagent consumption in flotation cells.

Characterisation of solid hydrodynamics in a three-phase stirred tank reactor with positron emission particle tracking (PEPT)

It is challenging to measure the hydrodynamics of stirred tank reactors when they contain multiphase flows comprising liquid, gas bubbles and particles. Radioactive particle tracking techniques such as positron emission particle tracking (PEPT) are the only established techniques to determine internal flow behaviour due to the inherent opacity and density of fluid and the vessel walls. The profiles of solids flow are an important tool for robust reactor design and optimisation and offer insight into underlying transport processes and particle–fluid–bubble interactions for applications such as froth flotation. In this work, measurements with PEPT were performed with two tracer particles differing in surface hydrophobicity to characterise the solids hydrodynamics in a baffled vessel agitated with a Rushton turbine. The location data from PEPT were averaged with time to estimate the probability density function (PDF) of particle velocity in individual voxels. The peaks of these voxel distributions were used to produce profiles of solids flow in different azimuthal and horizontal slices. Bimodal vertical velocity distributions were observed in the impeller radial jet which suggest the particles experienced trajectory crossing effects due to inertia. Statistical tests were performed to compare the velocity distributions of the hydrophilic and hydrophobic tracer particles, which indicated similar average flow behaviour in the liquid or pulp phase of the vessel and differences near the air inlet, in the impeller discharge stream and pulp–froth interface. With tracers designed to represent gangue and valuable mineral species, the differences in velocity reveal interactions such as bubble–particle attachment and entrainment. • Positron emission particle tracking (PEPT) measurements of multiphase flow. • Solid hydrodynamics in a three-phase stirred tank reactor of gas, liquid and solids. • Comparison of hydrophilic and hydrophobic particle flow behaviour. • Observations of particle interaction with the gas bubble flow field.

Evaluation of Erythrina fuscaLour. as a pulping raw material

ABSTRACT This paper characterizes Erythrina fusca Lour. in terms of anatomical, morphological and chemical properties to evaluate its efficacy as a pulping raw material. It is characterized with 47.0% α-cellulose and 28.8% lignin content with a fibre length of 1.11 mm. The vessels (pores) are distinct and form porous semi-rings, with a row of larger pores at the beginning of the growth layer, which facilitate penetration of chemicals during the cooking phase of pulping. Kraft pulping of E. fusca was carried out by varying cooking temperature, time and alkali charge. At optimum condition of 14% active alkali for 2 h of cooking at 170°C, pulp yield was 40% with kappa number of 26.6. The papermaking properties were also evaluated and showed tensile index of 52.4 N m g−1 with tear index of6.8 mN m2 g−1 at oSR of 57. This species can be used as a raw material for writing and printing grade pulp.

A dynamic flotation model for predictive control incorporating froth physics. Part I: Model development

It is widely accepted that the implementation of model-based predictive controllers (MPC) ensures optimal operation if an accurate model of the process is available. In the case of froth flotation, modelling for control purposes is a challenging task due to inherent process instabilities. Most models for control have only focused on the pulp phase rather than the froth phase, which is usually oversimplified or even neglected. Despite the fact that froth stability can significantly affect the overall performance of flotation cells, there is still a gap in literature regarding flotation models for control purposes that properly include froth physics.In this paper we describe the development of a dynamic flotation model suitable for model predictive control, incorporating equations that describe the physics of flotation froths. Unlike other flotation models for control in the literature, the model proposed here includes important variables related to froth stability, such as bursting rate and air recovery, as well as simplified equations to calculate froth recovery and entrainment. These model equations allow estimating the amount of valuable material reporting to the concentrate, which can be used as a proxy to estimate grade and recovery. Additionally, pulp-froth interface physics was also included in our model, which enables a more accurate prediction of relevant flotation variables.A sensitivity analysis of the parameters showed that two out of seven parameters were highly sensitive. The highly sensitive parameters are the exponential factor n of the equation for the overflowing bubble size, and the constant value a of the equation for the bursting rate. Although the other parameters showed a reasonably lower sensitivity than n and a, the results also revealed that there is a significant difference in the prediction accuracy if the parameters are poorly estimated. Further simulations of important variables for control exhibited a good adaptability to changes in typical variables, such as air and feed flowrates.An analysis of degrees of freedom of the model established that two variables need to be fixed to have a completely determined system. This means that two variables are available for control purposes, which can be air and tailings flowrates (through the manipulation of the respective control valves). This study therefore paves the way for the implementation of a robust dynamic model for flotation predictive control, incorporating important froth phenomena.

The Behavior of Gangue During the Flotation of a Sulfidic PGM-Bearing Ore in Response to Various Monovalent and Divalent Ions in Process Water.

Mineral concentrators are becoming increasingly aware of the importance of the quality of the water that they feed into their milling and flotation circuits. It is speculated that different inorganic constituents of process water may yield different flotation results owing to the electrolyte–reagent–mineral interactions occurring in the pulp phase. These interactions are said to be specific to ion type, reagent type, and mineral or ore type. It therefore stands to reason that there is a need to develop an understanding of the specific ion effects on both the pulp phase and the froth phase phenomena, such that the chemistry and the quality of process water can be monitored and controlled in a manner that does not negatively affect the flotation performance. Previous research has shown that inorganic electrolytes may impact the hydrophobicity and the floatability of mineral particles and could in turn affect froth stability, entrainment, and thus mineral grades and recoveries. In this study, the floatability of a Cu-Ni-PGM-bearing Merensky ore is tested on a bench-scale flotation system in various single salt solutions, viz., CaCl2, CaSO4, Ca(NO3)2, MgCl2, Mg(NO3)2, MgSO4, NaCl, NaNO3, and Na2SO4, in order to examine specific ion effects on gangue recovery. Coagulation and zeta potential tests are conducted in order to establish the nature of the impact that specific ions have on the behavior of gangue in flotation. The findings of this work have shown that single salt solutions containing ions resulted in a strong depression of gangue compared to those solutions containing Cl− and SO42− ions. It was also shown that the divalent Ca2+ and Mg2+ showed a stronger depression of gangue compared to the monovalent Na+. Ca2+, in comparison to Na+, resulted in an increase in the coagulation of the ore as well as an increase in the zeta potential of talc. Overall, the findings of this paper suggest that the presence of Ca2+ and Mg2+ in process water would most likely create conditions that promote gangue depression.

The Behaviour of Mixtures of Sodium Iso-Butyl Xanthate and Sodium Di-Ethyl Dithiophosphate during the Flotation of a Cu-Ni-Pt Ore in Degrading Water Quality

The use of mixtures of thiol collectors is reportedly beneficial in sulfide flotation. This is becoming standard practice for many concentrators, but process water recirculation and re-use in flotation circuits may compromise the behaviour of such mixtures owing to changes in physicochemical interactions occurring in the pulp phase as a result of water quality variations. It is expected that changes in the pulp chemistry would in turn affect both the pulp and froth phase phenomena, thereby affecting flotation performance. Thus, this study considers mixtures of thiol collectors, sodium iso-butyl xanthate (SIBX), and sodium di-ethyl dithiophosphate (SEDTP) in degrading water quality. Bench-scale flotation tests were conducted on various molar ratios of the selected thiol collectors under different ionic strengths (0.0242 mol·dm−3 and 0.1212 mol·dm−3) of synthetic plant water. Increasing the ionic strength of synthetic plant water and SEDTP molar ratio resulted in an increase in water, solids, Cu, and Ni recoveries. Cu-Ni grades decreased in increasing SEDTP molar ratios. The highest Cu-Ni grades were obtained in degrading water quality. The increase in water and solids recoveries in increasing SEDTP and ionic strength of plant water is attributed to an increase in froth stability. It can be concluded that the increase in the ionic strength of plant water increased water recoveries and therefore froth stability in parallel with SEDTP’s froth stabilizing effect, thus suggesting an additive interaction on the froth stabilisation effect seen.

A framework for polydisperse pulp phase modelling in flotation

Froth flotation is one of the most widely-used mineral processing operations. The pulp zone in flotation tanks is polydisperse in general and serves as a medium for the interaction between the solid particles and the gas bubbles in a liquid continuum, leading to particle–bubble attachment/detachment and bubble coalescence/breakage phenomena. To better predict the hydrodynamics and inform the design of efficient flotation equipment, it is therefore important to accurately model and simulate the evolution of the size distribution of the dispersed phases. This has created an urgent need for a framework that can model the pulp phase in an efficient manner, which is not currently available in the literature. The available software products are not efficient enough to allow for a tractable modelling of industrial-scale flotation cells and in some cases they cannot model the polydispersity of the dispersed phase at all. This work presents an efficient numerical framework for the macroscale simulation of the polydisperse pulp phase in froth flotation in an open-source finite element computational fluid dynamics (CFD) code that provides an efficient solution method using mesh adaptivity and code parallelisation. A (hybrid finite element–control volume) finite element framework for modelling the pulp phase has been presented for the first time in this work. An Eulerian–Eulerian turbulent flow model was implemented in this work including a transport equation for attached and free solid particles. Special care was taken to model the settling velocity of the free solids and the modification of the liquid viscosity due to the presence of these particles. Bubble polydispersity was modelled using the population balance equation (PBE), which was solved using the direct quadrature method of moments (DQMOM). Appropriate functions for bubble coalescence and breakage were chosen in the PBE. Mesh adaptivity was applied to the current problem to produce fully-unstructured anisotropic meshes, which improved the solution efficiency, while all simulations were executed on a multicore architecture. The model was validated for 2D simulations of a bubble column against experimental results available in the literature. After successful validation, the model was applied to the simulation of the pulp phase in a flotation column for monodisperse and polydisperse solids. Polydispersity of the solids was modelled for the first time in this work using three separate solid size classes. A clear dependence of the flotation rate on the particle size was noticed and the monodisperse solids simulations were shown to over-predict the flotation rate. Other than flotation, this open-source framework can be used for the simulation of a variety of polydisperse multiphase flow problems in the process industry.

Влияние технических лигносульфонатов на коррозию сварных швов в водоугольной суспензии

Hydrotransport of coal, iron ore, bauxite and other solid materials is known to be carried out through trunk pipelines. Hydrotransport of coal in the form of highly concentrated coal-water slurries (HCCWS) makes it possible to solve a whole range of problems from environmental ones to those when HCCWS are used as a fuel for energy boilers. The HCCWS combustion efficiency is determined by the concentration of the solid pulp phase and the particle size. The highest HCCWS combustion efficiency is observed when the mass concentration of the solid phase is 60--65 % and the particle size is up to 0.02 sm. In order to achieve stability of these slurries with the solid phase concentration, various additives are used to improve the rheological properties of coal-water slurries. In particular, such plasticizing agents as sodium tripolyphosphate, technical lignosulfonates, carbon-alkaline reagents and others are used. Plasticizing agents are known to change the rheological properties of coal-water slurries but the problems of corrosion activity of plasticizing agents are not well understood, especially with respect to welded joints of pipelines. Welded joints of slurry pipelines can be represented as macro-galvanic couples, in which the weld and base metal are electrodes of a galvanic element. The current magnitude of the macro-galvanic couple can be used to calculate the local corrosion value due to the work of the galvanic element of the base metal and the weld. The paper studies the effect of technical lignosulfonates (TLS) and TLS-based compositions in a coal-water slurry on the local currents of the base metal --- weld macro-galvanic couple made of 09G2S steel. Findings of research show that in the water-coal slurry the maximum inhibitory effect is observed when 0.75 % TLS + 0.25 % K2CrO4 (Na2CO3) is added to the slurry.

The spatial-temporal working pattern of cold ultrasound treatment in improving the sensory, nutritional and safe quality of unpasteurized raw tomato juice

In considering the adverse nutritional and flavor consequences of thermal pasteurization on fruit juices, freshly squeezed and unpasteurized fruit juices, commonly called raw juices, are of increasing demand as they are served in bars, restaurants and at home. Apparently, due to lack of controlled processing regime as did in a juice factory, the raw juice often undergoes a rapid phase separation and is at the risk of microbial unsafety. To this end, an attempt of cold ultrasound treatment (CUT, 87.52 W/cm2, 10 °C) was implemented to a raw tomato juice up to 30 min. Appreciatively, the physical stability, nutritional value and microbial safety substantially improved. On a CUT time scale, cloud stability and total phenolic content continuously increased; the total plate count was adversely altered; the rheological parameters (viscosity, thixotropy and shear-thinning tendency) and total carotenoids obtained shared a parabolic changing pattern but peaked at 15 min and 10 min, respectively. Finally, the ascorbic acid sharply increased at an earlier stage (5 min), and then remained stable throughout the whole process. Notably, the occurrences of these improvements are of spatial-temporal nature and resulted from different cavitation induced stress fields. At the initial stage, CUT chiefly worked via the mechanical field with the particles in pulp phase, making them smaller and releasing the soluble materials into serum phase. When the particles larger than approximately of 160 μm were completely disintegrated, the CUT entered its second stage and mainly functioned in the serum phase via both mechanical and chemical fields. As a result, the serum pectin and carotenoids were depolymerized and degraded, respectively. The present results are valuable in uncovering the mechanism and kinetics underlying the ultrasound treatment of fruit juices and the present CUT is highly recommended due to its high maneuverability and excellent performance.

Water quality effects on bubble-particle attachment of pyrrhotite

In froth flotation, separation between the valuable and the gangue minerals comes as a result of the attachment of hydrophobic particles to air bubbles. Considering the importance of bubble formation and bubble-particle attachment, it is evident that the pulp phase facilitates the events for the most crucial requirements of successful flotation. Water forms the bulk of the pulp phase; and as a result of water scarcities in countries like South Africa, the need to recycle process water within mining operations is increasing. Hence it is of great importance to understand the effects of water quality on the vital sub-processes within the flotation process, particularly bubble-particle attachment. A novel attachment timer which allows for 396 opportunities for bubble-particle attachment was used for the bubble-particle attachments tests in this work. Three water qualities of increasing ionic strength were tested both in the presence and absence of a xanthate collector to see the effect of increasing ionic strength of synthetic plant water on the bubble-particle attachment probability. The attachment time measurements showed a general decrease in attachment probability as the ionic strength of the synthetic plant water increased both in the absence and presence of a collector. This result indicated that increasing the concentration of the ions present in synthetic plant water lowered the probability of pyrrhotite particles attaching to air bubbles. Further, adsorption studies showed that less xanthate adsorbs on the mineral surface at the highest ionic strength of synthetic plant water under study. This indicates that increases in the ionic strength of synthetic plant water hindered the xanthate adsorption on the pyrrhotite surface. Furthermore, an increase in the zeta potential of pyrrhotite with increasing ionic strength was reported, indicating cation adsorption on the mineral surface. The study presented shows a direct relationship between the zeta potential and attachment probability.