Stirring Speed Research Articles

Characterization of the Dynamic Behavior of a Stirred Liquid–Liquid System for Process Control

AbstractThe dynamic behavior of a toluene/NaOH solution system was studied in a batch stirred tank. Characterization by step response experiments showed that the drop size response to stirrer speed steps behaves as a first‐order system, whereas the stirrer speed responds as a second‐order system. The respective time constants differed by at least one order of magnitude, suggesting effective control of the drop size is feasible by adjusting the stirrer speed. Based on experimental data, simple, linear system models were derived for the mean drop diameter and the interfacial area using the stirrer speed as input variable. Validation experiments showed good model qualities of about 70 % and the design of test trajectories proved the model's usability in an open‐loop control.

Loading of Ce and n co-doped TiO2 composites onto modified shell powder synergism of adsorption and photocatalysis phytic acid removal: performance and mechanism

Phytic acid was investigated as an organophosphorus pollutant. Titanium dioxide (TiO2) doped with Ce and N was prepared using the sol-gel method and loaded onto a modified shell power to produce modified shell powder/Ce-N-TiO2 (Msp/CeNT). The combined effects of adsorption and photocatalysis on phytic acid were explored. The actual phytic acid degradation rate with the composite photocatalyst was higher than the sum of the adsorption removal rate of phytic acid using the modified shell powder and the photocatalytic degradation removal rate of phytic acid using the Ce-N-TiO2 photocatalyst. Msp/CeNT synergistically affected adsorption and photocatalytic degradation. The effects of different factors, such as reaction temperature, catalyst dosage, initial pH, stirring speed, and light intensity, on the combined effect were investigated. The results showed that the synergistic effect increases with the increase of light intensity. Increasing the reaction temperature, catalyst dosage, initial pH, and stirring speed first increased and then decreased the synergistic effect of the composite photocatalysts. Phytic acid (69.54%) was degraded within 4 h when the temperature, pH, catalyst dosage, stirring speed, and light intensity were 25 °C, 5, 1 g/L, 300 rpm, and 500 W, respectively. We investigated and prepared a composite photocatalytic material, developing a new theoretical method for degrading organophosphorus dissolved in water and providing a basis for treating lake eutrophication as a practical application.

Catalytic epoxidation of waste palm kernel oil using in situ performic acid formation

AbstractThe use of renewable resources in the epoxidation process can reduce the dependence on non‐renewable petroleum resources and contribute to a more environmentally friendly chemical industry. This study aims to investigate the epoxidation of waste palm kernel oil as a renewable feedstock. The synthesis of epoxidized waste palm kernel oil was conducted by reacting waste palm kernel oil, formic acid, and hydrogen peroxide in a one‐pot system. Currently, there is no reported literature on the simultaneous application of a catalyst for the epoxidation of waste palm kernel oil derived from industrial waste. The optimum process parameters were determined, including hydrogen peroxide to waste palm kernel oil molar ratio (1.5:1), formic acid to waste palm kernel oil molar ratio (0.5:1), and stirring speed (300 rpm). The optimum relative conversion to oxirane of epoxidized waste palm kernel oil was 88%. A mathematical model was developed using numerical integration based on the fourth‐order Runge–Kutta method as follows: = 0.894 mol·L−1·min−1, = 7.420 mol·L−1·min−1, and = 0.086 mol·L−1·min−1. Based on the findings of the kinetic study, the kinetic model was validated due to its minimal simulation error.

RSM modelling and yield prediction of base-catalyzed transesterification of pumpkin-seed oil to biodiesel: artificial neural network, kinetics, and thermodynamics

The study examined the extraction of bio-oil from pumpkin seed and compared the optimization of the production of Fatty acid ethyl ester (FAEE) via the transesterification process using Response Surface Methodology (RSM), and Artificial Neural Network (ANN). This research uniquely highlights the utilization of pumpkin seed oil, a non-edible and sustainable feedstock, and combines RSM and ANN methodologies to enhance the precision of biodiesel optimization. The transesterification experiment was conducted at 60 min reaction time under varying temperature ranges, catalyst weight, stirrer speed, and ethanol-oil molar ratio. The RSM optimized conditions for maximum production were determined to be a 1.3% catalyst concentration, 6:1 ethanol-to-oil molar ratio, 50 °C temperature, and 550 rpm stirrer speed, resulting in a 90% biodiesel yield. The statistical evaluation metrics confirmed the neural network predictions were compromised to 80% yield due to limitations such as insufficient data size and the inherent complexity of the ANN model. The biofuel produced satisfied ASTM specifications peculiar to sustainable environmental applications. The mechanistic parameters revealed variations in thermodynamic stability and feasibility across reaction orders (zero, pseudo-first, and pseudo-second), emphasizing the temperature-dependent effects of the transesterification kinetic pathway on yield, design, and efficiency.

Experimental Study on Softening High-Calcium Sulfate Reverse Osmosis Concentrate Using Induced Crystallization Method

Reverse osmosis (RO) concentrate often contains high levels of sulfate and calcium ions due to the use of antiscalants, leading to significant calcium sulfate supersaturation and creating favorable conditions for induced crystallization. This study utilized a combination of static and dynamic experiments to investigate the key factors influencing the removal of calcium sulfate from RO concentrate via induced crystallization. The static experiments examined the effects of seed crystal concentration, stirring speed, reaction temperature, and the molar ratio of SO42− to Ca2+ on removal efficiency, with response surface methodology (RSM) employed to analyze the interactions among these factors. In the dynamic experiments, gypsum particles were used as seed crystals in a fluidized bed reactor to study the impact of initial seed crystal dosage and influent flow rate on the removal performance. Optimization strategies for stable operation were also explored. The static experiments revealed that seed crystal concentration was the most critical factor affecting removal efficiency. Under optimal conditions, the calcium ion concentration in the treated water could be reduced to 453 mg/L, achieving a removal rate of 63.8%. In the dynamic experiments, the effluent calcium ion concentration was reduced to 724 mg/L, with a removal rate of 52.5%. However, prolonged continuous operation led to a gradual increase in effluent calcium ion levels, which could be mitigated by recycling seed crystals from the settling zone back to the reaction zone. Characterization of the induced seed crystals and simulation calculations demonstrated that Ca2+ and SO42− reacted to form calcium sulfate crystals, primarily as CaSO4·2H2O, which adhered to the seed crystal surfaces. The growth of the seed crystals, indicated by an increase in particle size, correlated with the volume of water treated. This study provides valuable insights and data for the application of calcium sulfate-induced crystallization as a method to reduce sulfate and calcium ion concentrations in RO concentrate, offering a viable approach to water softening and resource recovery.

Effects of a 3D-Printed Turbulence Promoter on Membrane Fouling During the Ultrafiltration of Dairy Wastewater

In this study, the integration of a 3D printed turbulence promoter into a stirred membrane separation cell during dairy wastewater ultrafiltration was investigated. Its effects, along with the effects of stirring, on the permeate flux and membrane fouling were examined. The experiments were carried out at different transmembrane pressures (0.1, 0.2, and 0.3 MPa) and stirring speeds (RPM: 100–400 min−1), both with and without the application of the turbulence promoter. Various parameters were employed to characterize the membrane performance, such as the permeate flux, the flux decline ratio, and the fouling coefficient. To further investigate the membrane fouling mechanisms, mathematical models were used: the resistance-in-series model, the Makardij model, and the Hermia model. With the resistance-in-series model, we examined whether the membrane fouling was reversible (the deposit could be easily removed by washing operations) or irreversible (irreversible fouling) for each measurement, and with the Makardij model, we investigated whether the rate constant of the fouling or the rate constant of the deposit removal was the most important. In the case of the Hermia model, changes in the cake filtration rate constant were monitored. The results indicate that the combination of the 3D printed turbulence promoter and the stirring speed could effectively reduce membrane fouling during dairy wastewater ultrafiltration.

Analysis and optimization of the adsorption of lead ions on a new material based on silica synthesized from blast furnace slag.

A novel silica-based material (SBM), synthesized from chemically-, thermally-, and mechanically-treated blast furnace slag (TBFS), was examined for its batch-mode lead adsorption capacity based on various parameters. Physicochemical examinations revealed that the formulation of the new SBM consisted mainly of silica, which represented 81.79% of its total composition. After modification, the measured specific surface area changed significantly, from 275.8 to 480.13 m2/g, with a point of zero charge (PZC) of approximately 3.4 on the pH scale. The experiment revealed that the driving factors (contact time, stirring speed, solution pH, temperature, and initial concentration) greatly influenced improvement of the lead adsorption capacity, which reached 164.84 mg/g after 40 min of interaction. The adsorption isotherms demonstrated that the lead adsorption took place on a homogeneous surface and in a single layer, which was confirmed by the correlation coefficient and the ability of the Langmuir model to adsorb. The separation factor (RL) and heterogeneity factor (1/n) demonstrated that adsorption was favorable, while the Temkin parameter (bt) revealed that removal occurred through physical adsorption. According to the kinetic analysis, this process followed a pseudo-second-order kinetic model and was regulated by both external diffusion and intraparticle diffusion. Thermodynamic parameters demonstrated that lead adsorption was a spontaneous, exothermic, less entropic, and physical process, driven by electrostatic interaction. Activation energy revealed that the lead removal process occurred through physical adsorption. Desorption analysis demonstrated that SBM can be reused up to four consecutive times.

Characterization and Optimization of Vesicle Properties in bioPISA: from Size Distribution to Post-Assembly Loading.

This study investigates the formation and properties of vesicles produced via biocatalytic Polymerization-Induced Self-Assembly (bioPISA) as artificial cells. Methods for achieving size uniformity, including gentle centrifugation and sucrose gradient centrifugation, are explored, and the effects of stirring speed on vesicle morphology is investigated. The internal structure of the vesicles, characterized by a polymer-rich matrix, is analyzed using fluorescence correlation spectroscopy (FCS). Additionally, the feasibility of loading macromolecules into pre-formed vesicles is demonstrated using electroporation, and a fluorescent protein as well as enzymes for a cascade reaction were sucesfully incorporated into the fully assembled polymersomes. These findings provide a foundation for developing enzyme-synthesized polymeric vesicles with controlled morphologies for various applications, e.g., in synthetic biology.

Optimization of Aluminium Casting with Alumina Reinforcement via Stir Casting: Impact on Physical and Mechanical Properties

Aluminum casting using the stir casting method is a common practice in the industrial sector. This study aims to optimize the effect of stirring speed on the physical and mechanical properties of aluminum casting reinforced with alumina powder (Al2O3). The material used in this study is derived from discarded vehicle rim waste. The stir casting method was performed at varying speeds of 500, 600, and 700 rpm, with a mold temperature of 250°C and a pouring temperature of 700°C. Physical testing to examine the microstructure was conducted using optical metallography, hardness testing was performed using the Rockwell hardness scale B, and tensile strength was measured using a Universal Testing Machine. The microstructure observations showed that a stirring speed of 500 rpm yielded the best results, with minimal porosity. The highest hardness value recorded was 65 HRB at 500 rpm, consistent with the microstructure observations. The highest tensile strength was also recorded at 500 rpm, reaching 262 MPa.

Study on the Chlorination Leaching of Gold and Copper from High Gold-Containing Material Based on Variable Stirring Speed

Study on the Chlorination Leaching of Gold and Copper from High Gold-Containing Material Based on Variable Stirring Speed

Efficiency of Two Laterites in Cyanide Removal from Aqueous Solutions: Equilibrium and Kinetic Studies

In the dynamic of drinking water supply in rural populations, water pollution by cyanide is one of challenges that impacts the process in the mining areas of Burkina Faso. The objective of this work was to assess the efficiency of laterite soils to remove cyanide from water. To do this, two laterites were prepared and characterized by spectroscopic and analytical techniques to serve as adsorbent. The cyanide removal was carried out using batch experiments with cyanide aqueous solutions. The characterization of laterites using analytical techniques showed a specific surface area of 42.39 and 24.55 m<sup>2</sup>.g<sup>-1</sup>. The crystalline phases were mainly kaolinite, goethite, hematite, quartz, and alumina. The optimization of the operating parameters indicated a strong influence of operating conditions on the adsorption process. Indeed, the optimum stirring speed was 150 rpm corresponding to an adsorption capacity of 0.14 and 0.34 mg/g using raw (LB) and treated (LT) laterites, respectively. By assessing the influence of the contact time, the adsorption capacities were 0.35 and 0.19 mg.g<sup>-1</sup> at 40 and 75 min respectively using LT and LB corresponding to a treatment rate of 53% and 28%. The optimal doses were 28 and 45 g.L<sup>-1</sup> at the optimal temperature of 30°C using LB and LT. Results concluded the efficiency of treated laterite comparatively to the raw laterite. The isotherm modelling concluded on Freundlich isotherm indicating a multilayer adsorption following a pseudo-second order kinetic. Therefore, these laterites would be good filters for the treatment of cyanide enriched waters and other heavy metals in dynamic experiments.

Optimization of preparation parameters of palm oil-based nanofuel with multi wall carbon nanotube (MWCNT) for stability using Taguchi-grey relation analysis (GRA) combination

This research optimizes the preparation parameters of palm oil-based nanofuel and Multi Wall Carbon Nanotube (MWCNT) to produce stable nanofuel. The parameters optimized include stirrer speed, sonication time, sonication power, and surfactant ratio, with stability measured through absorbance and sedimentation ratio (SR). The Taguchi method, using an L9 orthogonal array designed with minitab 19.0 software, was employed for single-objective optimization, while Grey Relation Analysis (GRA) is applied for multi-objective optimization. Experimental results show that the optimal conditions for absorbance are stirrer speed of 1000 rpm, sonication time of 30 minutes, sonication power of 200 watts, and surfactant ratio of 1, whereas for sedimentation ratio the optimal conditions are stirrer speed of 1000 rpm, sonication time of 30 minutes, sonication power of 150 watts, and surfactant ratio of 1. ANOVA analysis reveals that surfactant concentration contributes the most to nanofuel stability, with contributions of 79.63% for absorbance and 82.60% for sedimentation ratio. Multi-objective GRA optimization results also show that surfactant concentration is the most dominant factor, contributing 71.5% to the Grey Relational Grade (GRG). The consistency of optimal parameters yielded by both Taguchi and GRA methods reinforces the validity and consistency of this study's results. This research provides a strong foundation for the development of more stable nanofuels, potentially enhancing energy efficiency and sustainability. These findings offer practical guidelines for real-world applications and make significant contributions to nanofuel technology

Impact of rotational speed and pH on tribocatalytic dye degradation activity of 0.5Ba(Zr0.2Ti0.8)O3‒0.5(Ba0.7Sr0.3)TiO3

AbstractThe degradation of methylene blue dye via tribocatalysis using 0.5Ba(Zr0.2Ti0.8)O3‒0.5(Ba0.7Sr0.3)TiO3 (BST‒BZT) ceramic powders was investigated under various conditions. The tribocatalytic process was initiated using magnetic stirring with a polytetrafluoroethylene‐coated magnetic bar in a glass beaker setup. The degradation efficiency was evaluated at different stirring speeds of 300, 500, and 700 rpm. The results showed significant variation in degradation rates, with the highest degradation efficiency of ∼73% achieved within 12 h at a rotational speed of 700 rpm. Additionally, the impact of pH on the degradation process was examined by adjusting the dye solution to pH levels of 3, 6, and 9. The degradation efficiency increased with higher pH levels, with the maximum degradation occurring in the basic medium (pH 9). Kinetic analysis revealed that the degradation process adhered to pseudo‐first‐order kinetics, with rate constants of 0.023, 0.035, and 0.104 min⁻1 at different stirring speeds of 300, 500, and 700 rpm, respectively. This study showcases the potential of BST‒BZT ceramics as efficient tribocatalysts for degrading organic pollutants in wastewater, emphasizing the impact of stirring speed and pH on degradation efficiency.

Polysilsesquioxane Open Hollow Spheres for Heavy Metal Ions Adsorption.

Hollow microspheres with open windows on the shells have shown significant potential in adsorption, catalysis, and drug delivery fields, owing to their low density, large interior volume, high specific surface area, and abundant availability of adsorption sites. However, creating open hollow spheres with structurally stable and entirely organic-functionalized surfaces remains a challenge. Herein, we fabricated polysilsesquioxane open hollow spheres using trialkoxysilane containing mercaptopropyl groups under vigorous stirring, employing polystyrene microspheres as a template. Various reaction parameters were explored, revealing stirring speed as the key factor influencing the morphology and openness of the microspheres. By examining the morphology of intermediate products at different reaction times, we proposed a step-growth mechanism for microsphere formation. The resulting materials exhibited high adsorption capacity and selectivity towards Hg2+ and Pb2+, attributed to the presence of thiol groups and the open-hollow structure. Our approach provides a robust method for producing open hollow materials with functionalized surfaces, offering potential applications in the adsorption field.

Removal of crystal violet dye from aqueous solutions using Robinia pseudoacacia L. (Fabaceae) Fruits biosorbent

Synthetic dyes are a major source of environmental pollution. In this regard, biosorption is an important treatment method for the removal and detoxification of synthetic dyes from aqueous solutions. Accordingly, the present study was conducted to investigate the potential of Robinia pseudoacacia L. biosorbent (RPF) in the removal of crystal violet (CV) dye from aqueous solutions. To this end, biosorption parameters, including zero charge point, pH, initial dye concentration, biosorbent dose, stirring speed, and temperature, were investigated. Variations in the treated and untreated biosorbent surfaces were characterized using FTIR spectroscopy. The results showed that the RPF biosorbent removed 77% of CV under optimal conditions: pH of 6, initial dye concentration of 10 mg/L, biosorbent dose of 1 g, contact time of 30 min, stirring speed of 150 rpm, and temperature of 298 K. The Dubinin-Radushkevich isotherm (R2= 0.976) and pseudo-second-order kinetic (R2 = 0.995) models were well fitted according to isotherm and kinetic studies. Thermodynamic studies revealed that the process was endothermic according to the ΔG values. Moreover, the phytotoxicity of treated CV solutions was significantly reduced. Thus, the RPF biosorbent was determined to be a low-cost, sustainable, and ecofriendly material for the removal and detoxification of synthetic dyes from aqueous solutions.

CELLULOSE NANOCRYSTALS BASED ON PINEAPPLE LEAF FIBERS IN HEMOPERFUSION APPLICATIONS FOR CREATININE REMOVAL: BATCH METHOD ADSORPTION STUDY

Kidney failure is a major global cause of mortality, often resulting from the buildup of uremic toxins like creatinine. Creatinine serves as an indicator for assessing treatment needs in kidney failure patients. Hemoperfusion, a treatment based on the adsorption of toxins, has shown promise when using cellulose nanocrystals (CNCs) as adsorbents. CNCs derived from pineapple leaf fibers offer unique advantages due to their abundance of active sites, high adsorption capacity, and strong binding affinity. This study investigates the efficiency of CNCs in reducing creatinine levels, with the reduction attributed to the binding of creatinine to CNC hydroxyl groups. Characterization of CNCs was performed using PSA, XRD, FTIR, and SEM-EDX techniques, while the residual creatinine was quantified via UV-Vis spectrophotometry, utilizing a picric acid complex under alkaline conditions and measured at 485 nm. Optimal conditions were found with a stirring speed of 210 rpm, 120-minute contact time, and 10 mg/L creatinine concentration, resulting in an adsorption capacity (Qads) of 2.572 mg/g. The CNC adsorbent demonstrated hemocompatibility, with an APTT blood coagulation time of 31.3 seconds. These findings suggest that CNCs could be highly effective in developing safer, efficient hemoperfusion systems for managing kidney failure.

Reactive extraction of methanesulfonic acid from wastewater using trioctylamine

Wastewater containing methanesulfonic acid (MSA) mainly originates from the production process of metal detergent, which also contributes significantly to environmental pollution. This study investigates the extraction of MSA from wastewater using trioctylamine (TOA). A thorough investigation was carried out into the factors that affect extraction efficiency, such as the type of extractant, phase ratio (O/A), temperature, stirring speed, and extraction time. An extraction efficiency of 96.1% was achieved using TOA at 25 °C, 1400 r·min− 1, and an extraction time of 30 min. Various techniques including FT-IR, XPS, and high-resolution ESI-MS were employed to investigate the extraction mechanism. The results of different techniques revealed that the complexation between TOA and MSA occurred through ionic and hydrogen bonding interactions. Moreover, TOA was successfully regenerated through back-extraction with sodium hydroxide. The proposed extraction system is advantageous for eco-friendly engineering applications.

Mitigating the challenges of textile wastewater treatment in Saudi Arabia utilizing electrocoagulation process: Optimization of operating parameters

The increasing importance of treating industrial effluents for environmental and public health protection has necessitated reliable and economical treatment methods capable of meeting stringent effluent quality standards. This study aimed to evaluate the effectiveness of the electrocoagulation (EC) process using iron electrodes for treating real textile wastewater by removing total solids (TS), COD, colour, and turbidity. Various operating parameters, including treatment time, initial pH, current density, stirring speed, and inter-electrode spacing (IES), were investigated to optimize removal efficiency. The results demonstrated that the optimal conditions for maximum pollutant removal were achieved at a treatment time of 60 minutes, a current density of 6.2 mA/cm², a solution pH of 8-8.5, a stirring speed of 150 rpm, and an IES of 5 cm. Under these conditions, the removal efficiencies reached 79.2% for TS, 92.7% for COD, 88.9% for turbidity, and 98.7% for colour. The findings of this research indicate that the EC process is a simple, quick, and economically viable method for effectively removing pollutants from textile wastewater. Additionally, it is recommended that a coupled treatment unit, such as filtration or adsorption, be employed following the EC process to enhance pollutant removal. Saudi Arabia’s Vision 2030 aims to address environmental pollution from industrial wastewater, including textile wastewater, highlighting the importance of balancing industrial growth with environmental stewardship. Present study offers the first thorough analysis of textile wastewater treatment utilizing EC process in the region, enhancing understanding of effective strategies for sustainability and compliance with effluent quality standards.

Optimization of reinforcement ratio and stirring speed on mechanical properties of Al-TiB2-B4C hybrid composite using Taguchi – grey relational analysis

Abstract The aim of the research is to optimise percentage raio of hybrid reinfoecements and stirring speed to maximize the mechanical properties of the hybrid composite by and Taguchi analysis and grey relational analysis. The matrix material employed in this study is Al 7075, while boron carbide (B4C) and titanium diboride (TiB2) serve as the reinforcement materials.. The hybrid metal matrix composite is produced via the stir casting method. For experimental design Taguchi L9 orthogonal array was adopted, with the weight percentage of the reinforcement materials and stirring speed identified as experimental factors. the specified levels of weight percentage for the reinforcements B4C and TiB2 were established at 3%, 6%, and 9%. The mechanical properties analysed as response parameters consist of tensile strength, hardness, impact strength, and flexural strength. The Taguchi analysis, particularly the signal-to-noise (S/N) ratio evaluation, reveals that the percentage weight of TiB2 is the predominant factor affecting tensile strength. In contrast, the percentage weight of B4C significantly influences both hardness and flexural strength, while stirring speed is the most critical parameter for impact strength. The optimal parameters identified for maximizing tensile strength, hardness, and flexural strength are 9% B4C, 9% TiB2, and a stirring speed of 600 rpm. The highest grey relational grade was attained in experiment number 9, which utilized these optimal parametric values.

Investigating the Relationship Between the Emulsification Parameters and Physical-Chemical Properties of Poly(D,L-lactic acid) Particles for Dermal Fillers.

Poly(L-lactic acid) (PLLA) and poly(D,L-lactic acid) (PDLLA) particles have been applied as dermal fillers for soft-tissue augmentation because they can induce foreign-body reactions, resulting in fibroblast proliferation and collagen formation. Although PLLA and PDLLA fillers are safe and biocompatible, clinical complications such as nodules and granulomas have been reported, possibly due to incomplete reconstitution. PDLLA particles were prepared via emulsification in this study, and three stirring speeds were investigated when adding PDLLA into carboxymethyl cellulose solution. The particle size, molecular weight of PDLLA, optical rotation, pH value, osmotic pressure, and reconstitution time were analyzed. A rabbit dorsal ear model was established to evaluate the soft-tissue augmentation of a commercial PDLLA filler. The results demonstrated that the stirring speed affected the particle size, but not other physical-chemical properties of the PDLLA particles. All the PDLLA particles were reconstituted in less than 7 min, which is faster than the process for the other commercial PDLLA dermal filler products. In addition, the PDLLA particles could induce inflammation and fibroblast proliferation. Although the PDLLA particles generated in this study have not yet been investigated in vivo, the results demonstrated here suggest their potential for application as dermal fillers.