Stirred Bead Mill Research Articles

Integrating wet stirred-bead milling for Tetraselmis suecica biorefinery: Operating parameters influence and specific energy efficiency

Stirred bead milling proved to be an efficient cell destruction technique in a biorefinery unit for the extraction of over 95 % of proteins and 60 % of carbohydrates from the green marine microalga Tetraselmis suecica. Optimum conditions, expressed in terms of metabolite yield and energy consumption, were found for average values of bead size and agitator rotation speed. The higher the microalgae concentration, up to 100 g.L−1, which is adequate for biofilm algae growth in an industrial unit, the more efficient the cell destruction process. Cell destruction rates and metabolite extraction yields are similar in pendular and recycling modes, but the pendular configuration reduces the residence time of the suspension in the grinding chamber, which is less costly. With regard to the cell destruction mechanism, it was concluded that bead shocks first damage cells by permeabilizing them, and that after a longer period, all cells are shredded and destroyed, forming elongated debris.

Tailoring hydroxyapatite suspensions by stirred bead milling

The present work deals with the use of stirred bead milling process to tune the hydroxyapatite particles size adjusting the process conditions. Our goal is to find the optimal parameters to obtain particulate suspensions within a 0.2–1.5 μm particle size range. This size range is preferable to produce spherical feedstock for powder bed fusion technologies through the atomization process. A Darvan C dispersant agent dosage of 2.1 mg m−2 (active component) to the specific surface of the ceramic was found, through stability and rheological analyses, to be the most outstanding dosage for stabilizing the dispersion. Milling chamber, bead wear, and energy consumption were evaluated and minimized, finding the most efficient operating parameter setting for the process. For the studied material, the use of a fast stirrer speed, smaller grinding media size, and higher solids concentration increased the energy efficiency. This work confirmed the presented laboratory-scale milling process as a promising method to study the processing of hydroxyapatite-filled slurries, as a first-step product, on the manufacture of hydroxyapatite microspheres for the powder bed fusion industry.

Observation of the depassivation effect of attrition on magnesium silicates' direct aqueous carbonation products

The main obstacle to the aqueous carbonation of non-serpentinised magnesium silicates is the formation of surface passivation layers, which severely limits the reaction rate and thus the overall efficiency of the process. A technological solution to overcome this problem is to perform the carbonation process inside a stirred bead mill, which aims to continuously remove the surface by-product layers by attrition. In this work, the aqueous carbonation of ferronickel slag, a mineralogically complex mining waste composed of a Mg/Si rich amorphous phase and a crystalline ferrous forsterite, was studied at 150°C and under 10 bar of CO2 with different operating configurations: carbonation alone (C mode), attrition followed by carbonation (A-C mode) and concomitant attrition and carbonation (AC mode). By careful observation of the mineralogy and the surface of the secondary phases formed using complementary analytical techniques, the article allows a better understanding of the passivation phenomenon inherent to the carbonation of magnesium silicates, and confirms the effectiveness of continuous surface mechanical depassivation for reaching high carbonation rates with this type of material. Comparative analysis of the products obtained with the three operating modes shows that a true synergy takes place between attrition and carbonation due to the combined effect of continuous exfoliation and mechanical activation of particle surface, which goes far beyond the simple increase in surface area due to particle size reduction. While mechanical depassivation is here substantiated by several evidence, the additional mechanochemical activation effect cannot be delineated from experiment; however its beneficial contribution to carbonation is inferred from its observation in A-C mode. The work finds that the synergy between attrition and carbonation also yields very characteristic products. They consist in micrometric agglomerates formed by bound spherical particles a few tens of nanometers in size. These particles themselves contain an entanglement of nanometric grains of carbonates and amorphous silica dispersed inside a magnesium-depleted alumino-siliceous matrix. These results confirm that concomitant attrition and carbonation offers one of the most promising pathways for developing direct aqueous carbonation processes with non-thermally activatable magnesium silicates.

Synthesis of Silica Particles Using Ultrasonic Spray Pyrolysis Method

Silica has sparked strong interest in hydrometallurgy, catalysis, the cement industry, and paper coating. The synthesis of silica particles was performed at 900 °C using the ultrasonic spray pyrolysis (USP) method. Ideally, spherical particles are obtained in one horizontal reactor from an aerosol. The controlled synthesis of submicron particles of silica was reached by changing the concentration of precursor solution. The experimentally obtained particles were compared with theoretically calculated values of silica particles. The characterization was performed using a scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS). X-ray diffraction, frequently abbreviated as XRD, was used to analyze the structure of obtained materials. The obtained silica by ultrasonic spray pyrolysis had an amorphous structure. In comparison to other methods such as sol–gel, acidic treatment, thermal decomposition, stirred bead milling, and high-pressure carbonation, the advantage of the ultrasonic spray method for preparation of nanosized silica controlled morphology is the simplicity of setting up individual process segments and changing their configuration, one-step continuous synthesis, and the possibility of synthesizing nanoparticles from various precursors.

Insights Into Nickel Slag Carbonation in a Stirred Bead Mill

This work is part of the ongoing development of the attrition-leaching carbonation process, a single-step aqueous carbonation technology that integrates a stirred bead mill. The principle of the attrition-leaching carbonation process is to continuously refresh the surfaces of reactive particles so that leaching can proceed unimpeded, yielding enhanced carbonation kinetics and yield. Invariably, attrition-leaching carbonation experiments carried out under controlled temperature and CO2 partial pressure conditions with different silicate-rich carbonation feedstocks - natural ores and nickel slags - show a carbonation yield that tends towards a plateau 20 to 50% below the stoichiometric yield. This repeatable behaviour raises the question as to whether the carbonation limitation is due to specific equilibrium side reactions of the carbonation feedstock or to a kinetic limitation of the attrition-leaching carbonation process. To try to provide some answers to this puzzling question, this reflexive paper implements a “thermo-kinetic” modelling methodology based upon geochemical equilibrium simulations and particle reaction models. The results obtained indicate that the observed slowing down of the carbonation process can be explained either by the formation of Mg- and/or Fe-rich silicates that precipitate at the expense of carbonates, or by a decrease in the efficiency of the attrition process over time. Indeed, either one of these mechanisms could explain the observed behaviour of the attrition-leaching carbonation process. However, the cross comparison of different data sources pleads in favour of the attrition-leaching carbonation performance being limited by the attrition process. Pending further confirmation, this tentative conclusion suggests that further development of the attrition-leaching carbonation process requires new knowledge about its inner workings, and that there may be ways to optimize the performance of this process beyond that based on standard stirred bead mill operating rules.

Mechanochemical preparation of ternary polyethyleneimine modified magnetic illite/smectite nanocomposite for removal of Cr(VI) in aqueous solution

A ternary nanocomposite integrating polyethyleneimine (PEI), magnetite (Fe3O4) nanoparticles, and illite/smectite clay nanoflakes (denoted as PEI-MI/S) was prepared via a mechanochemical route in a high-energy density stirred bead mill. The ternary PEI-MI/S nanocomposite was determined by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetry, scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry and X-ray photoelectron spectroscopy, respectively. The results show that ternary PEI-MI/S nanocomposite can be prepared in the presence of intense grinding, which can graft a more amount of PEI rather than that prepared in the absence of grinding. The compressive and shear stresses in intense grinding can disperse Fe3O4 nanoparticles and exfoliate/destruct I/S clay nanoflakes. Also, the mechanochemical effect facilitates the hydrogen bond and electrostatic interaction between PEI and magnetic I/S, and the crosslink reaction between PEI and glutaraldehyde in grinding, resulting in a more grafting amount of PEI. Ternary PEI-MI/S nanocomposite was applied for the removal of hexavalent chromium (Cr(VI)) anions in aqueous solution. The effect of parameters (i.e., pH value, adsorption time, temperature, and initial concentration of Cr(VI) anions) on the adsorption performance was investigated. It is indicated that the adsorption of Cr(VI) anions onto PEI-MI/S nanocomposite be related to the adsorption/reduction process. Ternary magnetic PEI-MI/S nanocomposite with a saturated magnetization (Ms) of 14.7 emu/g facilitates the magnetic separation and reusability. The regenerated ternary PEI-MI/S nanocomposite can maintain 71.43% of initial activity for adsorption of Cr(VI) anions after 6 cycles.

Synthesis of sodium polyacrylate copolymers as water-based dispersants for wet ultrafine grinding of cobalt aluminate particles

Sodium polyacrylate copolymers, i.e., polymethyl methacrylate-methacrylic acid-2-acrylamido-2-methylpropane sulfonic acid-hydroxyethyl methacrylate (PMASHS) were synthesized with polymethacrylic acid-2-acrylamido-2-methyl propane sulfonic acid-hydroxyethyl methacrylate (PASH) as water-based dispersants for ultrafine grinding of cobalt aluminate (CoAl2O4) particles in a stirred bead mill. The product size/size distribution, suspension rheological properties, electrokinetic potential and adsorption behavior were analyzed by laser particle size analysis, rheometry, thermogravimetry and electrokinetic potential measurement, respectively. Dispersant PMASH1 used for grinding the pigment particles for 120 min gives an increased product fineness with a narrower particle size distribution. This is possibly due to the presence of solvated chains of dispersant PMASH1 on the particle surface generating a proper steric hindrance energy between the particles. Besides, the breakage behavior of CoAl2O4 particles in ultrafine grinding was also discussed by selection and breakage functions from population balance modeling, indicating that the addition of dispersant PMASH1 in ultrafine grinding has a greater grinding efficiency. The breakage mechanism of the pigment particles in the bead mill is mainly abrasion, accompanied by compression.

Preparation of submicron-sized quasi-spherical silica particles via ultrafine grinding with chemical dissolution assistance

Submicron-sized silica particles with the quasi-sphericity were prepared via wet ultrafine grinding in a high energy-density stirred bead mill in the absence and presence of different salt solutions (i.e., water, potassium chloride (KCl), sodium chloride (NaCl), magnesium chloride (MgCl2), calcium chloride (CaCl2), barium chloride (BaCl2) and ammonia chloride (NH4Cl)). Effects of parameters (i.e., salt solution type, salt concentration, solid content of silica particles and grinding time) on the size/size distribution and sphericity of silica particles ground in the mill were investigated. The results show that submicron-sized quasi-spherical silica particles can be obtained under the selected condition (i.e., solution of BaCl2, BaCl2 concentration of 0.01 mol/L, solid content of 20 wt.% and grinding time of 30 min). Besides the size reduction and size distribution improvement, the sphericity can enhance from 0.71 for the original particles to 0.76 for the ground particles in the absence of any salt solution. Also, the proper addition of BaCl2 during ultrafine grinding can give a finer product with a steeper size distribution, and the particle quasi-sphericity increases from 0.76 to 0.89. It is revealed that ultrafine grinding can affect the spheroidization with and without chemical dissolution. In addition, the mechanism for ultrafine grinding of silica particles without and with chemical dissolution assistance was also discussed via the selection and breakage functions from population balance modeling.

Is it time for routinely tracking of early immunosuppression in tracking and prognosing patients with acute pancreatitis?

(Ni, Sb)-co-doped rutile yellow ceramic pigments were synthesized via a mechanical activation-assisted solid-state reaction in a stirred bead mill. The effects of mechanical grinding of the raw materials on the synthesis of (Ni, Sb)-co-doped rutile pigment were investigated. The results show that mechanical activation effectively decreased the crystallinity of the mixed precursors, thus enhancing their reactivity and the migration rate of ions. These effects lowered the temperature required for formation of the rutile phase. Compared with results from a mixture of separately ground precursors, the mixture of raw materials ground together was more effective for accelerating nickel/antimony ions doping into the TiO2 structure and improved the color performance of the pigment. The pigment from the mixed raw materials ground for 2.0 h and heat-treated at 1100 °C could be used as an environmentally-friendly ceramic yellow pigment owing to its low-toxicity, bright yellow hue, good chemical/thermal durability, and high cost-effectiveness.

Synthesis and characterization of (Ni, Sb)-co-doped rutile ceramic pigment via mechanical activation-assisted solid-state reaction

(Ni, Sb)-co-doped rutile yellow ceramic pigments were synthesized via a mechanical activation-assisted solid-state reaction in a stirred bead mill. The effects of mechanical grinding of the raw materials on the synthesis of (Ni, Sb)-co-doped rutile pigment were investigated. The results show that mechanical activation effectively decreased the crystallinity of the mixed precursors, thus enhancing their reactivity and the migration rate of ions. These effects lowered the temperature required for formation of the rutile phase. Compared with results from a mixture of separately ground precursors, the mixture of raw materials ground together was more effective for accelerating nickel/antimony ions doping into the TiO2 structure and improved the color performance of the pigment. The pigment from the mixed raw materials ground for 2.0h and heat-treated at 1100°C could be used as an environmentally-friendly ceramic yellow pigment owing to its low-toxicity, bright yellow hue, good chemical/thermal durability, and high cost-effectiveness.

Comparison of high pressure homogenization and stirred bead milling for the production of nano-crystalline suspensions

Currently, the two technologies primarily used for the manufacturing of nano-crystalline suspensions using top down process (i.e. wet milling) are high pressure homogenization (HPH) and stirred bead milling (SBM). These two technologies are based upon different mechanisms, i.e., cavitation forces for HPH and shear forces for stirred bead milling. In this article, the HPH and SBM technologies are compared in terms of the impact of the suspension composition the process parameters and the technological configuration on milling performances and physical quality of the suspensions produced. The data suggested that both HPH and SBM are suitable for producing nano-crystalline suspensions, although SBM appeared more efficient than HPH, since the limit of milling (d50) for SBM was found to be lower than that obtained with HPH (100 nm vs 200 nm). For both these technologies, regardless of the process parameters used for milling and the scale of manufacturing, the relationship of d90 versus d50 could be described by a unique master curve (technology signature of milling pathway) outlining that the HPH leads to more uniform particle size distribution as compared to SBM.

Simulation of solid-liquid flows in a stirred bead mill based on computational fluid dynamics (CFD)

The selection of simulation model is an important step in computational fluid dynamics (CFD) to obtain an agreement with experimental work. In addition, computational time and processor speed also influence the performance of the simulation results. Here, we report the simulation of solid-liquid flow in a bead mill using Eulerian model. Multiple Reference Frame (MRF) was also used to model the interaction between moving (shaft and disk) and stationary (chamber exclude shaft and disk) zones. Bead mill dimension was based on the experimental work of Yamada and Sakai (2013). The effect of shaft rotation speed of 1200 and 1800 rpm on the particle distribution and the flow field was discussed. For rotation speed of 1200 rpm, the particles spread evenly throughout the bead mill chamber. On the other hand, for the rotation speed of 1800 rpm, the particles tend to be thrown to the near wall region resulting in the dead zone and found no particle in the center region. The selected model agreed well to the experimental data with average discrepancies less than 10%. Furthermore, the simulation was run without excessive computational cost.

Disintegration of Nannochloropsis sp. cells in an improved turbine bead mill

The Nannochloropsis sp. cells in aqueous solution were disintegrated in an improved bead mill with turbine agitator. The disintegration rates of cell samples disrupted under various operating parameters (i.e., circumferential speed, bead size, disintegration time, and cell concentration) were analyzed. An experimental strategy to optimize the parameters affecting the cell disintegration process was proposed. The results show that Nannochloropsis sp. cells can be effectively disintegrated in the turbine stirred bead mill under the optimum condition (i.e., circumferential speed of 2.3m/s, concentration of 15vol.%, disintegration time of 40min and bead size of 0.3–0.4mm). The disintegration mechanism was discussed via the selection and breakage functions from population balance modelling. It is revealed that the impact and compression effects of stirring beads are more effective for the disruption of coarser fraction of cells, and the shear effect dominates the production of finer fractions of disintegrated cells.

Low-temperature synthesis of zircon by soft mechano–chemical activation-assisted sol–gel method

Zircon (i.e., ZrSiO4) was synthesized by a sol–gel route at a low temperature with assistance of soft mechano–chemical activation of derived precursors in a high-energy density stirred bead mill. The reaction of precursors pretreated by soft mechano–chemical at different time in sol–gel process was analyzed. The samples were characterized by X-ray diffraction, Fourier transfer infrared spectroscopy, nitrogen gas adsorption method (BET), thermogravimetry, scanning electron microscopy and high-resolution 29Si nuclear magnetic resonance spectroscopy. The results show that zircon powder with a high crystallinity and a small grain size can be formed via soft mechano–chemical pre-activation and sol–gel route at a lower temperature. The specific surface area of calcined powder increases and the average crystalline size and mean surface particle size decreases with increasing the soft mechano–chemical treatment time. It is indicated that the soft mechano–chemical activation can accelerate the dehydration/dehydroxylation reactions, reduce the bonding degree of Si–O bonds, and break a certain extent of [SiO4]4− tetrahedral three-dimensional network, which is formed in the sol–gel reaction, thus enhancing the reactivity of precursors and facilitating the formation of ZrSiO4 from Zr4+ ions with [SiO4]4− tetrahedra during the subsequent thermal treatment at a lower temperature (i.e., 700 °C). XRD patterns of all the ground precursors fired at 700 °C. Soft mechano–chemical activation of precursor prepared in sol–gel route could decrease the subsequent sintering temperature of ZrSiO4. Compared to the precursor unactivated, ZrSiO4 powder with a high crystallinity was formed at a lower sintering temperature (i.e., 700 °C) for the precursor activated for 6 h.

Effect of mechanical activation on solid-state synthesis process of neodymium disilicate ceramic pigment

The effect of mechanical activation of precursors ground in a high-energy density stirred bead mill on the synthesis of Nd2Si2O7 powders was investigated. The reaction of precursors after the mechanical treatment at different milling time was analyzed by laser particles size analysis, thermogravimetry and differential thermal analysis (TG-DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results reveal that the precursors without grinding and fired at 1200 °C cannot form the Nd2Si2O7 phase. Nd2Si2O7 can be formed at 986.9 °C when the precursors are ground for 3.0 h. To further clarify the effect of mechanical activation, two raw materials (i.e., SiO2 and Nd2O3) were pre-treated by different methods. The raw materials mixed and subsequently ground is conducive to decreasing the temperature of forming pure Nd2Si2O7 phase. The results indicate that the mechanical activation favors the promotion of the crystal growth of Nd2Si2O7. In addition, the color properties of the synthesized Nd2Si2O7 powders were also evaluated by reflection differential colorimetry. It is indicated that Nd2Si2O7 powders that possess a high-temperature stability can be used as a ceramic pigment.

The study of electrical conductivity and diffusion behavior of water-based and ferro/ferricyanide-electrolyte-based alumina nanofluids

Nanofluids are liquids containing suspensions of solid nanoparticles and have attracted considerable attention because they undergo substantial mass transfer and have many potential applications in energy technologies. Most studies on nanofluids have used low-ionic-strength solutions, such as water and ethanol. However, very few studies have used high-ionic-strength solutions because the aggregation and sedimentation of nanoparticles cause a stability problem. In this study, a stable water-based alumina nanofluid was prepared using stirred bead milling and exhibits a high electrical conductivity of 2420μS/cm at 23°C and excellent stability after five severe freezing–melting cycles. We then developed a process for mixing the water-based nanofluid with a high-ionic-strength potassium ferro/ferricyanide electrolyte and sodium dodecyl sulfate by using stirred bead milling and ultrasonication, thus forming a stable electrolyte-based nanofluid. According to the rotating disk electrode study, the electrolyte-based alumina nanofluid exhibits an unusual increase in the limiting current at high angular velocities, resulting from a combination of local percolation behavior and shear-induced diffusion. The electrolyte-based alumina nanofluid was demonstrated in a possible thermogalvanic application, since it is considered to be an alternative electrolyte for thermal energy harvesters because of the increased electrical conductivity and confined value of thermal conductivity.

Production of Submicron Particles by Mechanical Treatment: Width of Particle Size Distribution and Fineness of Product

Calcium carbonate (CaCO3) powders commonly used as a functional filler in paints, inks, papers, plastics, cosmetics, and so on, are generally produced by mechanical treatment (milling). This research was aimed to produce calcium carbonate submicron particles by stirred milling in wet conditions. The experiments were carried out by a batch operation, and determined the change in particle size distribution (PSD) of calcium carbonate. The product size (fineness) and PSD were used in the evaluation of the test results. The results showed that wet grinding in a stirred bead mill using the smaller grinding media (500 µm) is an effective method for reduction of product size (∼500 nm) of the CaCO3 powder.

Preparation and Thermo-Physical Properties of Fe2O3-Propylene Glycol Nanofluids.

Iron oxide (Fe2O3) nanoparticles were prepared from ferric chloride and ferrous sulphate by precipitation reaction. Fe2O3-propylene glycol nanofluid was prepared by dispersing Fe2O3 nanoparticles in propylene glycol through stirred bead milling, shear homogenization and probe ultrasonication. The nanofluid was characterized through measurement of viscosity, particle size distribution and thermal conductivity. The interactions between Fe2O3 nanoparticles and propylene glycol on the nanoparticle surfaces lead to reduction in viscosity, the magnitude of which increases with nanoparticle concentration (0-2 vol%) at room temperature. The thermal conductivity enhancement for 2 vol% nanofluid was about 21% at room temperature, with liquid layering being the major contributor for thermal conductivity enhancement.

Wet grinding of CaCO3 with a stirred media mill: Influence of obtained particle size distributions on pressure filtration properties

Chemical and process industries utilize stirred media mills for efficient fine grinding of solids. Stirred media mills, also referred to as stirred ball or stirred bead mills, generally have a good ability to produce fine particles with a relatively narrow particle size distribution. Wet grinding with vertical stirred ball mills is typically carried out for slurries containing particles smaller than 200μm, such as industrial minerals and pigments. Filtration is an important unit operation, which is performed in order to reduce the water content of the slurry after grinding and concentration, and prior to drying and transportation. Pressure filters are used to obtain the maximum dryness of the product. A number of properties of solids affect the filtration performance. The particle size and shape, the width of particle size distribution, and the net surface charge of the particles are among the factors having a significant influence on the filtration characteristics.In this study, the dependency of the pressure filtration properties of wet ground calcium carbonate (GCC) slurries on the grinding result obtained by a stirred media mill is investigated. After grinding, subsequent filtration experiments were carried out with a laboratory-scale pressure filter. Average specific cake resistances, porosities of the filter cakes, and cake compressibility parameters were determined from the filtration data. The results showed clear correlations between the particle size data and the related filtration properties. Interesting observations were also made regarding the average porosity of the filter cakes and the uncertainty of the experiments.

Development of an attrition-leaching hybrid process for direct aqueous mineral carbonation

Mineral carbonation is the single most eligible companion solution to geosequestration for mitigation of anthropic CO2 emissions on a large scale. Amongst its possible pathways, direct aqueous mineral carbonation stands out as one of the most promising ones. The originality of the present work lies in the transposition of the concomitant exfoliation/mineralisation concept, which was first proposed by the mineral carbonation research group from the Arizona State University in early 2000s, inside a dedicated attrition environment, more specifically inside a stirred bead mill. Experimental results and analyses bring definite proofs about the possibility and synergy of concomitant exfoliation and mineralisation. Given high carbonation yield for olivine and serpentinised ores (up to 35% in 5h and 80% in 24h in water, and 70% in 5h with inorganic additives) and the capacity of stirred mills to process mining size throughputs, this work leads to real perspectives for developing large scale robust solutions for direct aqueous mineral carbonation.