Kinetic and Microhydrodynamic Modeling of Fenofibrate Nanosuspension Production in a Wet Stirred Media Mill

This study examined the impact of stirrer speed and bead material loading on fenofibrate particle breakage during wet stirred media milling (WSMM) via three kinetic models and a microhydrodynamic model. Evolution of median particle size was tracked via laser diffraction during WSMM operating at 3000–4000 rpm with 35–50% (v/v) concentration of polystyrene or zirconia beads. Additional experiments were performed at the center points of the above conditions, as well as outside the range of these conditions, in order to test the predictive capability of the models. First-order, nth-order, and warped-time kinetic models were fitted to the data. Main effects plots helped to visualize the influence of the milling variables on the breakage kinetics and microhydrodynamic parameters. A subset selection algorithm was used along with a multiple linear regression model (MLRM) to delineate how the breakage rate constant k was affected by the microhydrodynamic parameters. As a comparison, a purely empirical correlation for k was also developed in terms of the process/bead parameters. The nth-order model was found to be the best model to describe the temporal evolution; nearly second-order kinetics (n ≅ 2) was observed. When the process was operated at a higher stirrer speed and/or higher loading with zirconia beads as opposed to polystyrene beads, the breakage occurred faster. A statistically significant (p-value ≤ 0.01) MLRM of three microhydrodynamic parameters explained the variation in the breakage rate constant best (R2 ≥ 0.99). Not only do the models and the nth-order kinetic–microhydrodynamic correlation enable deeper process understanding toward developing a WSMM process with reduced cycle time, but they also provide good predictive capability, while outperforming the purely empirical correlation.

Response Surface Methodology to Optimize the Isolation of Dominant Volatile Compounds from Monofloral Greek Thyme Honey Using SPME-GC-MS

This study aimed at an experimental design of response surface methodology (RSM) in the optimization of the dominant volatile fraction of Greek thyme honey using solid-phase microextraction (SPME) and analyzed by gas chromatography-mass spectrometry (GC-MS). For this purpose, a multiple response optimization was employed using desirability functions, which demand a search for optimal conditions for a set of responses simultaneously. A test set of eighty thyme honey samples were analyzed under the optimum conditions for validation of the proposed model. The optimized combination of isolation conditions was the temperature (60 °C), equilibration time (15 min), extraction time (30 min), magnetic stirrer speed (700 rpm), sample volume (6 mL), water: honey ratio (1:3 v/w) with total desirability over 0.50. It was found that the magnetic stirrer speed, which has not been evaluated before, had a positive effect, especially in combination with other factors. The above-developed methodology proved to be effective in the optimization of isolation of specific volatile compounds from a difficult matrix, like honey. This study could be a good basis for the development of novel RSM for other monofloral honey samples.

One-step method for obtaining potassium sulfate and processing of lye

Method of obtaining potassium sulfate with basic substance content higher 92 % shown. Process conditions: 110 % KCl (10 % excess substance from stoichiometry), mixing at temperature higher 95 °C during 30 min, mixing at temperature 0 °C for 1 hour, stirrer speed 500 rpm, sludge washing 15 % water from wet sludge weight, drying the washed sludge at 70–80 °C during 1 hour. The degree of evaporation of the solution at which the double salt of potassium and ammonium sulfate precipitated was determined. The degree is 30 % at the evaporated suspension cooled, and is 45 % at hot filtration.

Recovery of Manganese from Ferromanganese Slag by Leaching with Sulphuric Acid

Investigations on extraction of manganese from ferromanganese slag, a waste product from a local ferroalloy industry, were carried out using sawdust as a reducing agent. Leaching of manganese was done with sulphuric acid. The effects of particle size, stirring speed, contact time, acid concentration, temperature and dosage of reductant were studied. Based on the experimental results, the recovery of manganese increased with decreasing particle size. Optimum values of acid concentration, stirrer speed and contact time were obtained for realizing maximum recovery of manganese. With the addition of reductant, there is a significant increase in the yield of manganese.

Mechanochemical Treatment of Historical Tungsten Tailings: Leaching While Grinding for Tungsten Extraction Using NaOH

Innovative tungsten (W) extraction techniques are continually being sought because of challenges of low leaching efficiencies, despite using advanced processing units such as autoclaves operating high temperatures and pressures. Compared to conventional leaching, mechanochemical treatment improves the efficiency of leaching. Therefore, in this study, an innovative mechanochemical treatment method, referred to as leaching while grinding (LWG), was employed as a reprocessing option to optimize W recovery from historical tungsten tailings. Experiments were run using the regular two-level factorial design to screen through the four factors of stirrer speed, liquid/solid ratio, temperature, and digestion time to assess their criticality and effects in the LWG process. The stirrer speed and the liquid/solid ratio were the most critical factors in the optimization of W recovery. The maximum W recovery (91.2%) was attained at the highest stirrer speed (410 rpm), low liquid/solid ratio (0.8), long digestion time (6 h), and low leaching temperature (60 °C). The attained low leaching temperature (60 °C) was due to the mechanical activation of scheelite resulting from the simultaneous grinding and leaching. For such low- grade W material, liquid/solid ratio optimizing is critical for maintaining the digestion mixture fluidity, and for environmental and economic sustainability regarding the sodium hydroxide (NaOH) consumption, which was low.

Sustainable Manufacturing and Optimization of Squeeze Stir Cast Rods Using Recycled Aluminum and Alumina Reinforcements

This work focusses on the production of sustainable metal metrics composites MMCs. The scrap aluminum alloy wheel (SAAW) was used as a metrics and alumina is used as a reinforcement. The process parameters (namely squeeze pressure and time, die preheating temperature and stirrer speed) were optimized using Taguchi method to produce the alumina reinforced-aluminum matrix composites (AMCs). These stir-casted composites were characterized based on their hardness, tensile and compression strengths and wear/tribological properties. The results showed that addition of alumina to aluminum matrix has improved the mechanical and tribological performance. From, Taguchi analysis the optimized 9 approaches (L1 to L9) were obtained and, L5 and L6 methods showed optimum mechanical properties with 100 MPa squeeze pressure, 30 to 40 sec squeeze time, 250 to 350°C die preheating temperature and 450 to 525 rpm stirrer speed process parameters. It was found that properties are process parameters dependent. The produced AMCs have many potential industrial applications including applications in piping industry.

Solketal Production by Glycerol Acetalization Using Amberlyst-15 Catalyst

Glycerol, as a by-product of biodiesel production, has recently increased due to the rapid growth of the biodiesel industry. Glycerol utilization is needed to increase the added value of glycerol. Glycerol can be converted to solketal, which can be used as a green fuel additive to enhance an octane or cetane number. Conversion of glycerol to solketal was conducted via acetalization reaction with acetone using amberlyst-15 as the catalyst. The objective of present study was to investigate the effect of some operation conditions on glycerol conversion. Furthermore, it also aimed to develop a kinetic model of solketal synthesis with amberlyst-15 resins. The experiment was conducted in a batch reactor, equipped with cooling water, thermometer, stirrer, and a water bath. The variables that have been investigated in the present work were reaction temperature, reactants molar ratio, catalyst loading, and stirrer speed for 3 hours of reaction time. Temperatures, reactants molar ratio, and stirrer speed appeared to have a significant impact on glycerol conversion, where the higher values led to higher conversion. On the other hand, in the presence of catalyst, the increase of catalyst loading has a less significant impact on glycerol conversion. The results showed that the highest glycerol conversion was 68.75%, which was obtained at 333 K, the reactant’s molar ratio was 4, the amount of catalyst was 1 wt%, and stirrer speed of 500 rpm. Based on the pseudo-homogeneous kinetic model, the resulting kinetic model suitable for this glycerol capitalization. The value of parameters k and Ea were 1.6135 108 min-1 and 62.226 kJ mol-1,respectively. The simulation model generally fits the experimental data reasonably well in the temperature range of 313-333 K.

Secondary Nucleation Kinetics of AIBN Crystallisation in Methanol: Online Imaging-Based Measurement and Modelling

The secondary nucleation process of 2,2-azobisisobutyronitrile (AIBN) seeded crystallisation in methanol in a stirred tank reactor was studied at varying initial supersaturation levels, temperatures, crystal seed numbers, and stirrer speeds. The average secondary nucleation rate, induction time, and agglomeration ratio were measured using on-line microscopic imaging. The initial supersaturation level, temperature, and stirrer speed were found to be positively correlated with the secondary nucleation rate. A small change in the crystal seed number, i.e., 1-20, did not substantially affect the secondary nucleation rate throughout the secondary nucleation process. An increase in the initial supersaturation level and crystal seed number decreased the induction time, and an increase in the strength of agitation promoted the initiation of secondary nucleation at a stirring rate greater than 250 revolutions per minute (rpm). Temperature exerted a complex effect on the induction time. Regarding the agglomeration ratio, the initial supersaturation level positively correlated with the agglomeration ratio, while the stirrer speed negatively correlated with this parameter. Finally, based on the measured data, the average secondary nucleation rate, induction time, and final crystal suspension density were correlated. This study provides guidance for the control of supersaturation, induction time, stirring, and other factors in the crystal seed addition process in AIBN crystallisation.