Focused Beam Reflectance Measurement Research Articles

The impacts of high salinity and polymer properties on dewatering and structural characteristics of flocculated high-solids tailings

In seeking to better understand the inline flocculation technique for enhanced water recovery from concentrated fine-particle suspensions, polymers of different molecular weight (MW) and chemistry were used to treat a synthetic tailings slurry in a low-shear mixer for continuous flocculation under controlled conditions. The effects of dissolved salts in the slurry and polymer solution make-up water on dewatering performance were evaluated for conventional acrylamide/acrylate copolymers (BASF Magnafloc® products) and an alternative functional chemistry polymer (BASF Rheomax® DR 1050). The properties of the separated liquid and solid phases were examined to understand the impacts of salinity and polymer type on the formation of rapidly dewatering flocculated material. Higher concentrations of NaCl (0.006–0.6 M) and CaCl2 (0.006–0.06 M) salts in the unflocculated slurries formed larger coagulated structures, with focussed beam reflectance measurement (FBRM) showing greater pre-aggregation for the divalent salt. NaCl slurries show edge-to-edge (EE) and edge-to-face (EF) inter-particle associations that are open and easily disrupted while more compact face-to-face (FF) contacts are observed in CaCl2 slurries. For concentrated NaCl slurries, the dosing of medium-to-high MW polymers is generally preferred to maximise net water recovery, with the implication being that bridging mechanisms are still at play in high solids applications. In calcium-enriched slurries, the lower MW conventional copolymer gave comparatively better water returns than the other polymers when applied under low shear conditions, highlighting quite distinct aggregation processes compared to low solids flocculation. These results provide insight on the fundamental complexity of the ionic strength dependence of high solids-high dosage tailings flocculation, towards informing reagent polymer dosing and offering greater flexibility for end-of-pipe dewatering schemes.

Mode and dosage time in polyethylene glycol precipitation process influences protein precipitate size and filterability

Precipitation has gained interest as alternative to the costly protein A chromatography for monoclonal antibody purification. Traditional precipitation processes are based on direct addition of precipitant in a single dose, with limited control on co-precipitation of impurities and not considering batch-to-batch variations. We propose a gradual dosage of polyethylene glycol to prevent co-precipitation and control resulting floc size. We used focused beam reflectance measurement to demonstrate that the PEG6000 dosage time and the final concentration significantly changes the particle size distribution (PSD). We demonstrated that gradual and stepwise precipitant addition was superior to conventional batch PEG precipitation, improving product yield and purity by a factor of 4 for HCP removal, for samples pre-treated with CaCl2 and caprylic acid. We studied the 3D structure of the precipitates by fractal dimension and showed that precipitates exhibited different compactness and density depending on the dosage time, resulting in different filterability in tangential flow filtration and depth filtration. To switch from batch to continuous PEG addition, the 3D structure of precipitates needs to be considered due to its high impact on the resulting process performance. Focused beam reflectance measurement (FBRM) and fractal dimension can be used to adjust the precipitation methodology to improve the product quality attributes and inform about the design of further purification steps.

Reducing Magnesium within Seawater Used in Mineral Processing to Improve Water Recovery and Rheological Properties When Dewatering Clay-Based Tailings.

In areas where access to water for mineral processing is limited, the direct use of seawater in processing has been considered as an alternative to the expense of its desalination. However, efficient flotation of copper sulfides from non-valuable phases is best achieved at a pH > 10.5, and raising the pH of seawater leads to magnesium precipitates that adversely affect subsequent tailings dewatering. Seawater pre-treatment with lime can precipitate the majority of magnesium present, with these solids then being removed by filtration. To understand how such treatment may aid tailings dewatering, treated seawater (TSw) was mixed with raw seawater (Rsw) at different ratios, analyzing the impact on the flocculated settling rate, aggregate size as measured by focused beam reflectance measurement (FBRM), and vane yield stress for two synthetic clay-based tailings. A higher proportion of Tsw (10 mg/L Mg2+) led to larger aggregates and higher settling rates at a fixed dosage, with FBRM suggesting that higher calcium concentrations in Tsw may also favor fines coagulation. The yield stress of concentrated suspensions formed after flocculation decreased with higher proportions of Tsw, a consequence of lower flocculant demand and the reduced presence of precipitates; while the latter is a minor phase by mass, their high impact on rheology reflects a small particle size. Reducing magnesium concentrations in seawater in advance of use in processing offers advantages in the water return from thickening and subsequent underflow transport. However, this may not require complete removal, with blending Tsw and Rsw an option to obtain acceptable industrial performance.

Impact of hydrodynamic conditions on the structure of clay-based tailings aggregates flocculated in freshwater and seawater

• Flocculation of clay-based tailing in industrial water and seawater was compared. • A number of the particles does not flocculate unless the shear rate increases. • The use of seawater led to a reduction in the size of aggregates. • The fractal dimension of aggregates decreases with increasing mixing intensity. The impact of shear rate on the structural properties of aggregates obtained during the flocculation of clay-based tailings with an anionic polyacrylamide was analyzed. The effects generated in industrial water (IW) and seawater (SW) were compared. Flocculation-sedimentation batch tests were performed to know aggregate size distribution, hindered settling rate, and internal structure of flocs expressed through their fractal dimension. The aggregate properties were characterized by the Focused Beam Reflectance Measurement (FBRM) and Particle Vision Microscope (PVM) techniques. The aggregate size distribution showed a bimodal behavior, where a portion of the particles does not flocculate properly unless the shear rate increases during flocculation. On the other hand, the size and quantity of coarse aggregates strongly depend on the mixing intensity. The use of seawater led to a reduction in the size of aggregates. It is suggested that this is a result of polymer coiling, which leads to a decreased ability to form polymeric bridges and thus less particle capture. The fractal dimension of aggregates shows that while the shear rate increases, the aggregates are less compact, with structures possibly more open and further away from a solid spherical body. The greatest reduction occurred in industrial water, related to the larger size of the structures in a low salinity environment.

Influence of the flocculation effect on the rheological properties of cement slurry

The rheological properties have an important impact on the migration and diffusion of cement slurry in grouting reinforcement applications. The microscopic interaction between particles affects the macroscopic rheological behaviors of cement slurry. However, the detailed influence mechanisms still remain unclear. In this work, five different fineness cements were selected to investigate the rheological properties. The focused beam reflectance measurement (FBRM) system was used to detect the in-situ flocculation characteristics under different water-to-cement ratios, cement fineness, and shear rates. In addition, the initial and time-dependent rheological properties under various conditions were measured by a rotary viscometer. The results reveal that these three factors influence the number and particle size distribution of flocculent particles, and the degree of flocculation increases linearly with time. Cement slurry with a water-to-cement ratio ranging from 0.6:1 to 1.6:1 follows the Bingham model. The yield strength and plastic viscosity decrease with increasing water-to-cement ratio, and increase with increasing cement fineness. The apparent viscosity is reversible with the change of shear rate. The influence of water-to-cement ratio, cement fineness, and shear rate on the flocculation effect is consistent with the influence on rheological parameters. Three factors and time affect the rheological properties by influencing the formation and destruction of the flocculation structure, and then changing the content of free water and intergranular force in cement slurry. Our study has revealed the evolution of rheological properties from a microscopic point of view, which can provide theoretical guidance for the design and application of cement slurry.

Thermodynamic Study on the Amorphous Form and Crystalline Hydrates Using in Situ Raman and FBRM

AbstractThe solubilities and maximum supersaturation concentrations of an amorphous and the crystalline tetrahydrate and heptahydrate solids of disodium guanosine 5'‐monophosphate (GMP) in water‐methanol mixtures were measured in situ by Raman spectroscopy and focused beam reflectance measurement. The distinct Raman peaks of the amorphous form, crystalline hydrates, solution, and solvent were used for measurements of solubility and maximum supersaturation. Above 45 °C and at methanol fractions of 0.15–0.90, the tetrahydrate was the stable form, while below 40 °C and at methanol fractions of 0.15–0.60, the heptahydrate was the stable form. Especially, the tetrahydrate was stable in the methanol fraction > 0.7 at the temperature investigated. The solubility and supersaturated concentration values can be used to selectively produce amorphous, tetrahydrate, and heptahydrate solids of GMP by anti‐solvent crystallization.

Wet Milling, Seeding, and Ultrasound in the Optimization of the Oiling-Out Crystallization Process

Complicated solution environments in oiling-out crystallization can lead to particle agglomeration with wide size distribution and low purity of the products, due to complex interactions among two liquid phases and one solid phase during the oiling-out crystallization. This research mainly focuses on the optimization of size distribution by controlling particle agglomeration during the oiling-out crystallization process in a model system of propyl paraben–ethanol–water. Nucleation control technologies, wet milling, seeding, and ultrasound were used to limit the agglomeration. Further investigations of wet milling were performed before the nucleation or in the crystal growth stages with different geometries, such as coarse, medium, and fine rotor–stator tooth pairs. An integrated process analytical technology tools (PAT) array, including focused beam reflectance measurement (FBRM), particle visual monitoring (PVM), and attenuated total reflectance ultraviolet/visible (ATR-UV/vis), was used to observe the droplet formation of the dispersed phase, size distributions, and particle shapes during the nucleation and crystal growth. The results demonstrate that wet milling, seeding, and ultrasound technologies can help to optimize the particle size distribution in complex solution environments with different levels of efficiencies.

Selective aggregation of fine quartz by polyaluminum chloride to mitigate its entrainment during fine and ultrafine mineral flotation

• Polyaluminum chloride (PAC) could lower quartz entrainment in galena flotation. • Adding xanthate before PAC suppressed the depressive effect of PAC on galena. • PAC selectively aggregated fine quartz particles in the galena-quartz mixture. • The rate of PAC adsorption onto quartz surfaces was higher than on galena. • PAC adsorbed on quartz through both charge neutralization and Al bridging. Fine and ultrafine hydrophilic particles are typically left in a dispersed state in a flotation pulp when novel fine mineral flotation technologies are developed. These dispersed fine and ultrafine gangue particles can enter flotation concentrate by mechanical entrainment, lowering concentrate grade. The problem is becoming increasingly more pervasive as the required liberation size of value minerals in ores decreases. In this work, polyaluminum chloride (PAC) was investigated to study its effect on the reduction of quartz entrainment in the batch flotation of synthetic mixtures of quartz and galena. Apart from the evaluation of quartz entrainment, micro-flotation of galena, batch flotation of artificial mixtures of galena and quartz, the aggregation/dispersion behaviors of quartz and galena and their mixtures in the presence of PAC were studied by sedimentation, turbidity, focused beam reflectance measurement (FRBM) coupled with optical microscope observations and scanning electron microscope (SEM), and zeta potential measurements. The results indicated that the addition of PAC reduced quartz entrainment without adversely affecting galena flotation, so that the flotation separation efficiency was increased from 74% (without PAC) to 77% (when PAC was added prior to xanthate) and 80% (when xanthate was added prior to PAC) at PAC concentrations below 150 mg/L. PAC was found to aggregate the fine quartz but not galena. It was observed that PAC preferentially adsorbed on quartz in the quartz-galena mixtures, so that it lowered the entrainment of quartz and improved separation efficiency.

High molecular weight guar gum assisted settling of fine solids in diluted bitumen: Effect of solvents

As water-based extraction technologies for producing bitumen from oil sands have received increasing environmental concerns, developing non-aqueous extraction (NAE) technique is of both fundamental and practical importance. However, the relatively high concentration of fine solids trapped in the extracted bitumen presents an obstacle for pipeline transport as well as upgrading and refining downstream. This research attempts to provide a solution to fine solids removal without using synthetic additives or affecting bitumen recovery from NAE process. Herein, naturally hydrophilic additives (i.e., water and high molecular weight guar gum (HGG) produced from Cyamopsiste tragonolobuosr L. Taup.) were introduced to promote the settling of fine solids suspended in bitumen-solvent solution, and the effects of solvents (i.e., toluene, cyclohexane and their mixtures) were systematically investigated. Aggregate size distribution analyzed by the focused beam reflectance measurements confirmed that the addition of water and HGG could promote the agglomeration and settling of fine solids in all solvents studied. However, the size range and quantity of the agglomerates vary significantly with the solvent's aromatic character. Solvent mixtures demonstrate a superior performance on removing fine solids from bitumen over single solvent. Specifically, in a 3:2 toluene/cyclohexane mixture, the solid content was lowered from 0.66 wt% to 0.09 wt%.

Lime/Sodium Carbonate Treated Seawater to Improve Flocculation and Sedimentation of Clay-Based Tailings.

Seawater treated with lime and sodium carbonate in different proportions to reduce magnesium and calcium contents is used in flocculation and sedimentation tests of artificial quartz and kaolin tailings. Solid complexes were separated from water by vacuum filtration, and factors such as lime/sodium carbonate ratio, kaolin content, flocculation time, and flocculant dose are evaluated. The growth of the aggregates was captured in situ by a focused beam reflectance measurement (FBRM) probe. Solid magnesium and calcium complexes are formed in raw seawater at pH 11, impairing the performance of flocculant polymers based on polyacrylamides. The results show that the settling rate improved when the treatment’s lime/sodium carbonate ratio increased. That is, when a greater removal of magnesium is prioritized over calcium. The amount of magnesium required to be removed depends on the mineralogy of the system: more clay will require more significant removal of magnesium. These results respond to the structural changes of the flocs, achieving that the more magnesium is removed, the greater the size and density of the aggregates. In contrast, calcium removal does not significantly influence flocculant performance. The study suggests the necessary conditions for each type of tailing to maximize water recovery, contributing to the effective closure of the water cycle in processes that use seawater with magnesium control.

Cationic Lignin Polymers as Flocculant for Municipal Wastewater.

The radical polymerization of acid-washed and unwashed softwood kraft lignin with [2-(methacryloyloxy) ethyl] trimethylammonium chloride (METAC) was attempted to investigate the production of lignin-based flocculants for simulated wastewater. The incorporation of METAC onto lignin resulted in a cationic charge density (2.3–3.3 meq/g), increased water solubility (89–96% in neutral pH), and increased molecular weight (70,000–210,000 g/mol) of lignin. The lignin–METAC polymers generated from acid-washed lignin had higher molecular weights than those generated from unwashed lignin. The lignin–METAC polymers showed lower resistance to thermal decomposition than unmodified lignin due to the inclusion of PolyMETAC. The unmodified acid-washed lignin samples did not significantly affect the COD of the wastewater, while the unmodified unwashed lignin samples contributed to the COD, implying that unmodified lignin was not suitable for wastewater treatment. The flocculation of wastewater with lignin–METAC led to the chemical oxygen demand (COD) reduction of 17–23% and total organic carbon (TOC) drop of 51–60%. The lignin–METAC polymer with the highest molecular weight (produced from acid-washed lignin) reached the highest COD removal, while lignin–METAC polymer with the highest charge density (produced from unwashed lignin) reached the highest TOC removal. Focused beam reflectance measurement (FBRM) studies revealed that the lignin–METAC polymer produced from acid-washed lignin with a high molecular weight generated larger and more flocs in wastewater than the lignin–METAC polymer produced from unwashed lignin. The comparison of theoretical and experimental dosages required for neutralizing the charges of wastewater demonstrated that charge neutralization was the main flocculation mechanism, although a bridging mechanism was also involved for component removals from wastewater. The use of 1 mg/L of alum along with 65 mg/L lignin–METAC in a dual coagulation–flocculation system led to higher average phosphorous (42%) and COD (44%) removals than the singular flocculation system only using 65 mg/L of lignin–METAC (with phosphorous removals of 3.4% and COD removals of 18.7%). However, lignin–METAC flocculant slightly increased the ammonia–nitrogen content in both singular flocculation and dual coagulation–flocculation systems due to the residual ammonia content of lignin–METAC. The coagulation–flocculation system determined that the use of lignin–METAC (65 mg/L) could reduce the alum dosage significantly while maintaining a similar organic content reduction of 44% for wastewater.

Real-time particle size analysis using focused beam reflectance measurement as a process analytical technology tool for continuous microencapsulation process

The online real-time particle size analysis of the microencapsules manufacturing process using the continuous solvent evaporation method was performed using focused beam reflectance measurement (FBRM). In this paper, we use FBRM measurements to investigate the effects of polymer type and compare the size distributions to those obtained using other sizing methods such as optical microscope and laser diffraction. FBRM was also utilized to measure the length-weighted chord length distribution (CLD) and particle size distribution (PSD) online during particle solidification, which could not be done with laser diffraction or nested sieve analysis. The chord lengths and CLD data were taken at specific times using an online FBRM probe mounted below the microparticle. The timing of the FBRM determinations was coordinated with the selection of microparticle samples for particle size analysis by optical microscope and laser diffraction calculation as a reference. For all three produced batches tested, FBRM, laser diffraction, and sieve analysis yielded similar results. Hardening time for the transformation of emulsion droplets into solid microparticles occurred within the first 10.5, 19, 25, 30, and 55 min, according to FBRM results. The FBRM CLDs revealed that a larger particle size mean resulted in a longer CLD and a lower peak of particle number. The FBRM data revealed that the polymer type had a significant impact on microparticle CLD and the transformation process.

Rehydration characteristics of milk protein concentrate powders monitored by electrical resistance tomography

Electrical resistance tomography (ERT) is a robust and low-cost method offering real-time visualization of processes. In this work, we developed an ERT-based method to characterize the rehydration behavior of milk protein concentrate (MPC) powders. Circular-type and linear configurations were used to achieve high resolution in the radial and axial directions, respectively. To evaluate the rehydration profile, MPC powders were reconstituted to 2.5% (wt/wt) total solids at room temperature, and the rehydration behavior of the MPC powders [MPC with 85% protein (MPC85) and milk protein isolate with 90% protein (MPI90)] was monitored for a dissolution time of 30 min using the ERT system. The MPC powders were characterized in terms of overall mean conductivity, area under the mean conductivity curve, slope at a dissolution time of 3 min, and the relative dissolution index. Additionally, the focus beam reflectance measurement (FBRM) was used as a reference method to follow rehydration characteristics. Particle count changes from the FBRM measurements showed that MPI90 had higher larger particle counts and more resistance to dispersing in water. As the dissolution time proceeded, mineral ions and proteins were released and consequently increased the overall conductivity, confirming the transfer of water into MPC particles. At lower protein contents, the particle dispersion rate was higher and an increase in overall mean conductivity was observed, indicating better powder dissolution. Both configurations were able to effectively monitor differences in the dissolution behavior of MPC powders. In the ERT circular configuration, MPC85 and MPI90 showed maximum conductivity of 0.201 ± 0.006 and 0.162 ± 0.001 mS/cm, respectively. In the linear probe configuration, MPC85 and MPI90 showed maximum conductivity of 0.161 ± 0.001 and 0.136 ± 0.001 mS/cm, respectively, suggesting increasingly inhibited water transfer as the protein content of the powder increased. In this study, we demonstrated the capability of ERT using the circular and linear probe configurations to offer, in addition to qualitative tomographic images, reliable quantitative data by which to characterize the dissolution behavior of high-protein dairy powders.

Particle aggregation characteristics of hematite-quartz mixture with addition of sodium oleate

In the flotation of finely disseminated iron ores, fine hematite and gangue minerals (mainly quartz) always co-exist in the pulp, their higher interface energies would cause complex interfacial interactions and aggregations. Thus, particle aggregation characteristics in hematite-quartz systems with sodium oleate (NaOL) were studied in this research. The focused beam reflectance measurement (FBRM) and Zeta potential distribution analyses revealed that quartz and hematite particles formed hetero-aggregates at pH 5.0–7.0, while NaOL would weaken the hetero-aggregation by inducing the aggregate formation of hematite particles. The adsorption and contact angle tests indicated that hetero-aggregation inhibition could be attributed to oleate ion (OL−) adsorption onto hematite surfaces, which changed the surface charge and hydrophobic characteristics. Theoretical calculations demonstrated that the hydrophobic interactions among hematite particles, rendered hydrophobic by NaOL, were the main cause of hematite particles forming large aggregates.

Process development in the QbD paradigm: Implementing design of experiments (DoE) in anti-solvent crystallization for production of pharmaceuticals

Developing an understanding of critical process parameters and their impact on product quality attributes is crucial for implementing quality-by-design (QbD) in a pharmaceutical crystallization process. Use of statistical design of experiments (DoE) is widely accepted to be a more efficient experimental strategy for gaining the required process understanding than the traditional one-variable-at-a-time approach. In recent years, crystallization of active pharmaceutical ingredients (APIs) has been explored to generate crystals with desirable physical characteristics. Many problems in downstream processes can be attributed to poor particle characteristics established during the crystallization step. This paper presents the implementation of a DoE driven QbD approach for the anti-solvent crystallization of Dexlansoprazole API. Focused beam reflectance measurements were used to obtain crystal morphology data. Minitab19 statistical software was utilized for experimentation design and analysis. The empirical model thus created was statistically relevant. The model has been further used to design a control strategy to enable in-process control of the crystal size distribution during crystallization, as expected in the QbD paradigm. We expect that the proposed approach may benefit those wishing to achieve consistency in product quality during API crystallization.

Effect of the ultrasonic standing wave frequency on the attractive mineralization for fine coal particle flotation

Froth flotation for mineral beneficiation is one of the most important separation techniques; however, it has several challenges for processing fine and ultrafine particles. Attractive mineralization between particles and bubbles by ultrasonic standing wave (USW) is a novel and high-efficiency method that could assist fine particle flotation. Frequency is an important ultrasound parameter, whose effectiveness mechanisms on the attractive mineralization did not compressively address. This study explored the effect of the USW field with various frequencies on the fine coal flotation for filling this gap. Herein, a high-speed camera and a focused beam reflectance measurement (FBRM) were used to analyze three sub-processes of the attractive mineralization, including the microbubbles’ formation, the conventional flotation bubbles (CFBs)’ dispersion, and the particles’ movement. It was found that the maximum flotation metallurgical responses were obtained under the highest examined USW frequency (600 kHz). However, the flotation outcomes by a low USW frequency (50 kHz) were even lower than the conventional flotation tests. Observation and theoretical calculation results revealed these results were originated from the influence of frequency on the carrier bubbles’ formation and the action of the secondary acoustic force during USW-assisted flotation. These outcomes demonstrated that frequency is a key factor determining the success of attractive mineralization for fine particles’ flotation.

Use of Multi-Anionic Sodium Tripolyphosphate to Enhance Dispersion of Concentrated Kaolin Slurries in Seawater

This research aims to analyze the impact of sodium tripolyphosphate (STPP) as a rheological modifier of concentrated kaolin slurries in seawater at pH 8, which is characteristic of copper sulfide processing operations. The dispersion phenomenon was analyzed through chord length measurements using the focused beam reflectance measurement (FBRM) technique, complementing size distributions in unweighted and square-weighted modes. The reduction of the rheological properties was significant, decreasing from 231 Pa in a reagent-free environment to 80 Pa after the application of STPP. A frequency sweep in a linear viscoelastic regime indicated that by applying a characteristic dosage of 0.53 kg/t of STPP, the pulp before yielding increases its phase angle, which increases its liquid-like character. Measurements of the chord length verified the dispersion of particles, which showed an apparent increase in the proportion of fine particles and a reduction of the coarser aggregates when STPP was applied. Measurements of the zeta potential suggested that the high anionic charge of the reagent (pentavalent) increases the electrostatic repulsions between particles, overcoming the effect of cations in seawater. The results are relevant for the mining industry, especially when the deposits have high contents of complex gangues, such as clays, that increase the rheological properties. This increases the energy costs and water consumption needed for pumping the tailings from thickeners to the tailing storages facilities. The strategies that allow for the improvement of the fluidity and deformation of the tailings generate slack in order to maximize water recovery in the thickening stages.

A Criterion for Estimating the Strength of Flocculated Aggregates in Salt Solutions

A simple criterion is proposed to quantitatively estimate the resistance of aggregates based on incremental mechanical shear disturbances. Aggregate strength can be affected by the hydrodynamic conditions under which flocculation occurs; therefore, an experimental method is standardized to determine the resistance of aggregate structures that are formed under defined conditions of salinity (NaCl 0–0.1 M), mixing time (3 min), and mean shear rate (G = 273 s−1). Kaolin particles were flocculated in saline solutions with an anionic flocculant of high molecular weight. The method involves increasing the mean shear rate (G = 0–1516 s−1). Each increment represents a new experiment that starts from the base of 273 s−1. Target aggregates are increasingly fragmented as mechanical disturbance increases. The monotonic relationship between the mean shear rate increments (ΔG) and the final size of the aggregates is used for a quantitative estimate of the resistance of the target aggregates since this resistance underlies this relationship. The evolution of aggregate size is analyzed by the Focused Beam Reflectance Measurement (FBRM) method, which may capture the chord length distribution on concentrated slurries. To estimate and compare the resistance of the target aggregates in solutions with different salinities, a pseudo-first-order model that describes the rupture degree as a function of shear rate increments obtains the characteristic shear rate. The rupture percentage is reached with considerably lower agitation increments at higher salinity than at low salinity. This criterion is expected to help improve the efficiency of solid–liquid separation processes, especially in plants operating with seawater, be it raw or partially desalinated.

Effect of the Ultrasonic Standing Wave Frequency on the Attractive Mineralization for Fine Particle Flotation

Froth flotation for mineral beneficiation is the most important separation technique; however, it has several challenges for processing fine and ultrafine particles. Attractive mineralization between particles and bubbles by ultrasonic standing wave (USW) is a novel and high-efficiency method that could assist fine particle flotation. Frequency is an important ultrasound parameter, which its effectiveness mechanisms on the attractive mineralization did not compressively address. This study explored the effect of the USW field with various frequencies on the fine coal flotation for filling this gap. Herein, a high-speed camera and a focused beam reflectance measurement (FBRM) were used to analyze three sub-processes of the attractive mineralization, including the microbubbles' formation, the conventional flotation bubbles (CFBs)' dispersion, and the particles' movement. It was found that the maximum flotation metallurgical responses were obtained under the highest examined USW frequency (600 kHz). However, the flotation outcomes by a low USW frequency (50 kHz) were even lower than the conventional flotation tests. Observation and theoretical calculation results revealed these results were originated from the influence of frequency on the carrier bubbles' formation and the action of the secondary acoustic force during USW-assisted flotation. These outcomes demonstrated that frequency is a key factor determining the success of attractive mineralization for fine particles' flotation.

Floc structure and dewatering performance of kaolin treated with cationic polyacrylamide degraded by hydrodynamic cavitation

At present, efficient dewatering of mineral-processing–plant tailings still presents a serious challenge, especially for tailings with a high proportion of clay minerals. In this study, cationic polyacrylamide (CPAM) was degraded using hydrodynamic cavitation and was used for the flocculation and dewatering of kaolin. The properties of CPAM after degradation were characterized using a rheometer. At the same time, focused beam reflectance measurement, particle video microscopy, and low-field nuclear magnetic resonance were used to study the flocculation and filtration characteristics of kaolin treated by degraded CPAM. The results showed that with an increase in the cavitation time, the viscosity of CPAM decreases gradually and a flocculant mixture system with multimolecular weight is formed. In the process of kaolin flocculation, the pretreated CPAM makes the flocs smaller and denser, resulting in the acceleration of kaolin filtration.