Increasing Stirring Speed Research Articles

Removal of ammonium from municipal landfill leachate using natural zeolites

Ammonium ion-exchange performance of the natural zeolite was investigated in both batch and column studies. The effects of zeolite dosage, contact time, stirring speed and pH on ammonium removal were investigated in batch experiments. The result showed that ammonium removal efficiency increased with an increase in zeolite dosage from 25 to 150 g/L, and an increase in stirring speed from 200 to 250 r/min. But further increase in zeolite dosage and stirring speed would result in an unpronounced increase of ammonium removal. The optimal pH for the removal of ammonium was found as 7.1. In the column studies, the effect of flow rate was investigated, and the total ammonium removal percentage during 180 min operation time decreased with the flow rate though the ion-exchange capacity varied to a very small extent with the flow rate ranging from 4 to 9 mL/min. The spent zeolite was regenerated by sodium chloride solution and the ammonia removal capacity of zeolite changed little or even increased after three regeneration cycles.

Adsorption of Methyl Violet Dye, A Textile Industry Effluent onto Montmorillonite—Batch Study

In this study, methyl violet (MV) dye adsorption from synthetically prepared solutions onto montmorillonite was investigated. Experimental parameters were selected as stirring speed, adsorbent dosage, initial dyestuff concentration, initial solution pH, ionic strength, and temperature. It was determined that adsorption rate increased with increasing stirring speed, initial dye concentration, solution pH, ionic strength, and temperature, but decreased with increased adsorbent dosage. The experimental data were analyzed by Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherms, and it was found that the isotherm data were reasonably correlated by Langmuir isotherm. Maximum adsorption capacity of montmorillonite for MV dye was calculated as 230.04 mg g−1. Pseudo-first-order, pseudo-second-order, Elovich, and intraparticle particle diffusion models were used to fit the experimental data. Pseudo-second-order rate equation provided realistic description of adsorption kinetics. Thermodynamic parameters were calculated as 62.14 kJ mol−1, 59.55 kJ mol−1, 51.98 kJ mol−1, and 0.0242 kJ mol−1 K−1 for Ea, ΔH*, ΔG*, and ΔS* at 293 K, respectively. The value of the calculated parameters indicated that the physical adsorption of MV on the clay was dominant and the adsorption process was also endothermic. The positive values of ΔS° suggest the increased randomness. The positive ΔG° value indicated the un-spontaneous nature of the adsorption model.

EFFECT OF POURING TEMPERATURE AND STIRRING SPEED ON MECHANICAL, MICROSTRUCTURE AND MACHINING PROPERTIES OF AL6061-CU REINFORCED SICP METAL MATRIX COMPOSITES

The major challenges in the fabrication of MMC are the difficulties of achieving uniform distribution of reinforcing material and possible chemical reactions between reinforcement material and matrix. Therefore, the present research was conducted to investigate the effect of stirring speed and pouring temperature on mechanical, microstructure and machining properties of Al6061-Cu reinforced SiC MMC by stir casting technique. The dependent variables are hardness, impact strength and metal removal rate of MMC by electro-discharge machining while the independent parameters are five levels of stirring speed and five levels of pouring temperature. It is observed from experimentation that with the increase in stirring speed increases the impact strength and hardness of MMC up to a certain limit after that these properties decrease drastically. The optimal value of hardness and impact strength for MMC is obtained at pouring temperature of 725˚C and 400 rpm and impact strength of MMC are least at 800 rpm and 775˚C and followed by 50 rpm and 675˚C. It is observed from an SEM study that at stirring speed 400 rpm better homogeneity can be obtained compared to 200 and 600 rpm.

Phosphate removal from aqueous solution by Donnan dialysis with anion-exchange membrane

The removal of phosphate from aqueous solution by Donnan dialysis with anion-exchange membrane was investigated. The results show that phosphate could be removed from aqueous solution without supplying external high pressure or electrical potential. Under the conditions of influent phosphate of 2.0 mg/L, counterion(Cl−) concentration of 0.1 mol/L, stirring speed of 500 r/min and phase temperature of 298 K, the removal of phosphate achieves 70.0%. Decreasing counterion concentration has little influence on the removal of phosphate, but phosphate amount in anion-exchange membrane increases significantly. With the increase of stirring speed and phase temperature, the removal efficiency of phosphate greatly is improved. Existing forms of phosphate in aqueous solution affected transport of phosphate and only strong acidic pH of feed solution (pH=3.0) decreases the removal of phosphate. Transport of phosphate is also accompanied by change of pH value of feed solution. In consequence, it might be a promise potential process for phosphate advanced wastewater treatment, especially in the area where high salted nature water can be utilized.

Theoretical and Experimental Research of CO<sub>2</sub> Absorption Enhancement by Carbon Nano-Tube

The enhancement characteristics of carbon nanotubes (CNTs) on CO2 absorption were investigated experimentally a stirred thermostatic reactor. A comparison of CNTs with micro active carbon was made. From the experimental results, significant enhancement of CO2 absorption was obtained by both CNTs and micro active carbon, however, different change trends with stirring speed for the two solid particles was observed. With increasing stirring speed, the enhancement factor was decreased in AcC suspensions, whereas in CNT slurries it is increased. The experimental phenomena demonstrated a difference in enhancement mechanism for different size particles. For nanoparticles, besides the grazing effect, the micro-convection caused by Brownian motion should be also taken into account. The micro-convection strengthens the interaction of the concentration field around the particles and thus increases the diffusion rate of the solute. In addition, the agglomeration of the nanoparticle was also an important influencing factor. Due to the agglomeration of the particle, the enhancement factor for CNTs increases initially with increasing stirring speed. A three-dimensional microcosmic mass transfer model was developed to explain the experimental phenomena. Based on the model, the interaction of the flow field around the particles was analyzed.

Design of phosphated cross-linked microspheres of bael fruit gum as a biodegradable carrier

Present work was aimed at designing of phosphated cross-linked microspheres of bael fruit gum (BFG) by emulsification method using sodium-tri-meta phosphate as a cross-linking agent for treatment of colon cancer using 5-fluorouracil as model drug. Stirring speed was found to be 1,000rpm for about 5h to be optimal to obtain reproducible microspheres. It was found that there is an increase in particle size as polymer concentration is increased whereas a reduction in particle size was observed as there is increase in stirring speed. Cross-linked BFG microspheres were successfully prepared by emulsification method. Optimum surfactant concentration was found to be 2% w/w. Scanning electron microscopy studies showed that the drug-loaded microspheres were non-aggregated and in spherical shape. Differential scanning calorimetry and Fourier transform infrared-spectroscopy studies showed that drug and excipients are compatible. Release studies showed that drug release was more profound in cecal medium induced with enzymes causing degradation of the cross linked BFG than that of the release showed in simulated intestinal fluid. Stability studies showed that there were no significant changes in the drug content and physical appearance of microspheres.

PREPARATION OF FOLATE-CONJUGATED BOVINE SERUM ALBUMIN NANOPARTICLES ADSORBING EPIRUBICIN HYDROCHLORIDE

This work investigated the preparation process of folate-conjugated bovine serum albumin nanoparticles (FA–BSANPs) adsorbing epirubicin hydrochloride (EPI) nanoparticles (FA–EPI–BSANPs), a specific-targeting drug delivery system in cancer chemotherapy. The BSANPs were prepared by desolvation as a drug carrier system and conjugated with folate to produce FA–EPI–BSANPs that specifically target tumors by cross-linking. EPI, an anticancer drug, was adsorbed by this drug carrier system. The influences of six experimental parameters, namely, the adsorption time, FA–BSANPs solution-adsorbed EPI concentration, stirring speed, FA–BSANPs solution pH, the ratio of glutaraldehyde and BSA, and mass ratio of FA–BSANPs to EPI, on the drug loading efficiency (DLR) and drug entrapment efficiency (DER) of FA–EPI–BSANPs were investigated via the single factor method. The results indicated that the optimum operation conditions were obtained with 145.4 nm±0.5 nm MPS, 23.41% DLR and 98.93% DER. The N -hydroxysuccinimide-folate content associated with BSANPs was up to 0.9757% (wt). The DLR and DER of EPI increased with increasing adsorption time, FA–BSANPs solution concentration, and pH value, peaking at 1750 rpm with increasing stirring speed, but decreasing thereafter. The FA–EPI–BSANPs obtained were characterized by laser light scattering, scanning electron microscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, X-ray diffraction and thermogravimetric analysis. Drug release in vitro was investigated, as well. The characterization results showed that EPI in FA–EPI–BSANPs existed in an amorphous, instead of crystalline state. Most of the EPI was enclosed by FA–BSANPs, and a small amount was adsorbed onto the surface of the FA–BSANPs. The FA–EPI–BSANPs particles are nearly ellipsoidal and significantly affect sustained release. The inhibitory rate of FA–EPI–BSANP was mensurated by MTT method. The inhibitory rate of FA–EPI–BSANPs for SMMC 7721 cell developed with raise of concentration and was higher than other samples. The IC50 values of FA–EPI–BSANPs and EPI were 11.5 μg/mL and 18.8 μg/mL, respectively. The target ability of FA–EPI–BSANP for SMMC 7721 cell was mensurated by fluorescence (FITC) modified albumin techniques. The uptake rate of FA–EPI–BSANPs was higher than samples without folate conjugated, and increased with increased concentration.

Ultra fine grinding of silver plant tailings of refractory ore using vertical stirred media mill

Ultra fine grinding of the plant tailings of a refractory silver ore was studied using a laboratory type vertical stirred media mill. Preliminary tests confirmed that ultra fine grinding substantially improves the extraction of silver from the tailings in cyanide leaching (i.e. 36% Ag extraction rate from the as-received tailings with d80 of 100 μm, c.f. 84% extraction rate after ultra fine grinding of the tailings with d80 of 1.2 μm). In the ultra fine grinding tests, the effects of ball diameter (2–4.5 mm), stirring speed (200–800 r/min) and ball charge ratio (50%–80%) on the fineness of grind (d80, μm) were investigated through a Box–Behnken design. Increasing stirrer speed and ball charge ratio decreased fineness of grind while larger balls resulted in the coarser products. The tests demonstrated that a fineness of grind less than 5 μm can be achieved under suitable conditions. Analysis of stress intensity indicated an optimum range of stress intensity of (0.8–2)×10−3 N·m for all power inputs.

Migration distance-based platelet function analysis in a microfluidic system

Aggregation and adhesion of platelets to the vascular wall are shear-dependent processes that play critical roles in hemostasis and thrombosis at vascular injury sites. In this study, we designed a simple and rapid assay of platelet aggregation and adhesion in a microfluidic system. A shearing mechanism using a rotating stirrer provided adjustable shear rate and shearing time and induced platelet activation. When sheared blood was driven through the microchannel under vacuum pressure, shear-activated platelets adhered to a collagen-coated surface, causing blood flow to significantly slow and eventually stop. To measure platelet adhesion and aggregation, the migration distance (MD) of blood through the microchannel was monitored. As the microstirrer speed increased, MD initially decreased exponentially but then increased beyond a critical rpm. For platelet-excluded blood samples, there were no changes in MD with increasing stirrer speed. These findings imply that the stirrer provided sufficiently high shear to activate platelets and that blood MD is a potentially valuable index for measuring the shear-dependence of platelet activation. Our microfluidic system is quick and simple, while providing a precise assay to measure the effects of shear on platelet aggregation and adhesion.

Mechanical Stress on Lysozyme Crystals during Dynamic Cross‐Flow Filtration

AbstractThe influence of mechanical stress on the crystal size distribution of lysozyme crystal slurries in a dynamic cross‐flow device is discussed. The reduction of crystal size may have an influence on mass and resistance of the fouling layer. A filter test device with a filter area of 130 cm2 is used for thickening. After thickening, a model impurity, namely bovine serum albumin, is washed out of the suspension. A reduction of crystal size due to stirring and a reduced fouling layer with increasing stirrer speed is observed. Furthermore, a higher stirring speed increases the specific filtrate flux. In the presence of the impurity, more crystal aggregates than single isometric crystals are formed and, hence, the decrease of crystal size due to shear forces is more pronounced than without impurity.

Experimental and Theoretical Studies of CO2 Absorption Enhancement by Nano-Al2O3 and Carbon Nanotube Particles

The influence of nano-particles on CO2 absorption was studied experimentally in a stirred thermostatic reactor. Nano-Al2O3 and carbon nanotube (CNT) particles which showed different hydrophobic properties were chosen for the investigation. The experimental results were compared with that of micron-size activated carbon (AC) and Al2O3 particles. From the results, no enhancement by micron-size Al2O3 was found, and with the increase of Al2O3 concentration, the enhancement factor decreased. However, nano-Al2O3 showed a weak enhancement for the CO2 absorption. AC and CNT particles all intensified the gas-liquid mass transfer effectively, yet the trend of the enhancement factor with stirring speed for the two particles was different. With increasing stirring speed, the enhancement factor of AC particles was decreased, whereas in CNT suspensions it was increased. The experimental phenomena demonstrated a difference in enhancement mechanism for different size particles. For nano-particles, besides the influence of adsorbability and hydrophobicity, the micro-convection caused by Brownian motion should be also taken into account. Considering the micro-convection effect, a theoretical model was developed to shed light on the absorption enhancement by nano-particles.

Iron removal from extremely fine quartz and its kinetics

The iron impurity removal from extremely fine quartz and its kinetics have been explored. The investigation reveals that the product layer diffusion in heterogeneous reaction system is the rate-control step and the activation energy was found to be 45.37kJ/mol. But the mechanism seems to have a trend towards homogeneous reaction system with the second order rate model from the heterogeneous system. Because the homogeneous reaction system’s average linear correlation coefficient is up to 0.978, which is very close to 0.995 of its counterpart in heterogeneous system. This result was confirmed through examination of the homogeneous system models with the first and the second order rates, as well as the heterogeneous system models with interface film, product layer diffusion and chemical reaction models. Additionally, other interesting results revealed that the leaching efficiency for such extremely fine silica sand decreased with increasing stirring speed – this observation was opposite to that for coarse particles. Usually, leaching efficiency of coarse particles increases with increasing stirring speed or higher ultrasonic power.

Dispersion of micro diamond particles in electroless nickel solution

The dispersion behavior of micro-diamond particles ranging from 0 to 0.5 micron was compared between in DI water and in electroless nickel solution. The effects of the concentration of electroless solution, temperature, ultrasonic treatment, stirring speed, and baffles on the size distribution of micro diamond particles in electroless nickel solution were studied. Results show that the dispersion of micro diamond particles in DI water is obviously superior to that in electroless nickel solution. Micro diamond particles agglomerate evidently when the concentration of electroless solution V elect:V DI in dispersion media exceeds 5‰. Diamond particles agglomerate more and more seriously with the increase of the ion concentration. Applying ultrasonic, increasing stirring speed and adding baffles are helpful to improving the dispersion of diamond particles in the electroless nickel solution and its uniform distribution in the Ni-P coating.

Fabrication and Properties of Gelatin/Chitosan Microspheres Loaded with 5-Fluorouracil

The use of microspheres as drug delivery vehicles for anticancer therapeutics has great potential to revolutionize the future of cancer therapy. The present paper describes the influence of process variables on the encapsulation and loading efficiency of 5-Fluorouracil (5-FU) in gelatin/chitosan (Gel/Cs) microspheres. The influences of preparation parameters, including the contents of the emulsifier Span-80, the cross-linking agent and 5-FU, and the stirring speed, on drug loading and encapsulation efficiency of the microspheres were investigated. The experimental results indicated that drug loading and encapsulation efficiency of microspheres increased with increasing concentration of the cross-linking agent; and then decreased when the concentration of the cross-linking agent was higher than 0.3 ml·g−1 of Gel/Cs. Drug loading and encapsulation efficiency increased with increasing concentration of Span-80; they reached the maximum value when the concentration of the emulsifier was 0.012 g·ml−1. The loading and encapsulation efficiency of the microspheres also increased with increasing stirring speed. In addition, drug loading and encapsulation efficiency increased with increasing concentration of 5-FU; however, the encapsulation efficiency decreased when the concentration of 5-FU was higher than 40 mg·ml−1.

Performance and kinetic study of photo microbial fuel cells (PMFCs) with different electrode distances

Focus of this study is to observe the stirring effect on electrode distances by using Chlamydomonas reinhardtii transformation F5 in photo microbial fuel cells (PMFCs). The electrode distances applied in this study were 10.3, 12.5 and 14.7cm, respectively. Higher power density and lower internal resistance were observed at electrode distance of 14.7 and 10.3cm compared to at electrode distance of 12.5cm. Despite of it, higher exchange current density (io) and over potential (η) but lower electron transfer coefficient (β) can be observed at electrode distance of 14.7 and 10.3cm compared to electrode distance of 12.5cm. Since the results observed in the present study are different from some reported studies, the explanations are discussed in this paper. In addition we also performed experiment with different stirring speed and found out that power density increased and internal resistance decreased with the increasing stirring speed.

Effect of preparation conditions on the properties of microspheres prepared using an emulsion-solvent extraction process

Methylaluminoxane microspheres were prepared using a hydrocarbon-in-perfluorocarbon-emulsion solvent extraction process. The effect of the preparation conditions on the size of the microspheres was investigated. As expected, the size of the microspheres decreased with increasing stirring speed. At low surfactant concentrations the size of the microspheres was independent of the surfactant concentration. However, the size of the microspheres decreased as the surfactant concentration was further increased. The size of the microspheres was not only affected by the surfactant concentration but also by the volume ratio of the dispersed phase to the continuous phase. At a low volume ratio of the phases the effect of the surfactant on the size of the microspheres was larger than the effect of the increased volume ratio of the phases. At high volume ratios of the phases the effect of the volume ratio of phases on the size of the microspheres became more significant than the effect of the surfactant. A slow solidification increased the formation of non-spherical microspheres.

Extraction of phenol from aqueous effluent using triglycerides in supported liquid membrane

This research work focuses on the removal of phenol using a flat sheet supported liquid membrane impregnated with triglycerides (vegetable oils). The mass transfer of phenol was found to be dependent on various factors such as type of vegetable oil, support material, feed phase pH and concentration, stripping phase concentration and stirring speed. The phenol transport was found to be higher when PTFE membrane (pore size 0.45 μm) impregnated with coconut oil was used and mass transfer coefficient was found to be 3.50 × 10-6 m/s. The corresponding stirring speed, pH of feed solution, concentration of stripping (NaOH) solution were 350 rpm, 4.0 and 0.2 M, respectively. The 92.5% of phenol was extracted from feed phase to stripping phase in 20 h. The aqueous boundary layer thickness reduced with an increase in stirring speed up to a certain extent (350 rpm), beyond which, it resulted in turbulence leading to displacement of impregnated oil from membrane pores. Phenol can be transported through the membrane, ...

Fabrication and Characterization of Gelatin/Chitosan Microspheres for Drug Release

Gelatin/chitosan (Gel/Cs) microspheres were fabricated through an emulsification-solvent evaporation technique using saturated glutaraldehyde as a cross-linking reagent. The influences of the concentration of the emulsifier, stirring speed, and water/oil ratio on particle size and surface morphology were investigated. The experimental results indicated that the particle size of the microspheres decreased with increasing concentration of the emulsifier; however, the microsphere size did not change when the concentration of the emulsifier exceeded 0.016 g·mL−1. The particle diameter of the microspheres decreased with increasing stirring speed and increased with increasing water/oil ratio. The concentration of an acetone/water solution had an obvious effect on the morphologies of the Gel/Cs microspheres during the course of dehydration; the surface of the microspheres became smooth when dehydrated by an acetone solution with a volume ratio of 3:1.

Study of Strengthen Flotation Separation for Middle-Low Grade Bauxite

The ore properties and strengthen separation of bauxite were studied in this paper. The parameters in strengthen separation, such as dosage of collectors, flotation turbulence and inflation etc., were also discussed. With the increase of collector dosage, the recovery of Al2O3increased.,When the collector dosage was 900 g/t, A/S of foam was 7.06 and the recovery was 86.39%. The recovery also increased with the increase of stirring speed. When the speed of agitation mixing impeller reached 1700 r/min, the recovery was 84.56% and A/S of concentrate was 6.71. With the increase of inflation, the number of bubbles increased, the contact opportunities between bubbles and mineral particles increased, and the recovery increased. When the inflation was 0.35 m3/h, the recovery was 85.21% and A/S of foam was 6.71,. With the increase of inflation over 0.35 m3/h, the enhancement of recovery was not limited and the bubble inclusions led to the decrease of recovery of Al2O3.

Effect of stirring and temperature on synthesis yield and crystallization of hydrothermally synthesized K 2W 4O 13 nanorods

The K 2W 4O 13 was synthesized by hydrothermal treatment of crystalline WO 3·H 2O in the presence of K 2SO 4 in the stirred hydrothermal reactor operated at 120–180 °C for 1–6 h at the stirring speeds ranging from 0 rpm (static condition) to 700 rpm to investigate the significance of stirring on crystallization of the K 2W 4O 13 nanorods at different synthesis condition. The crystallization was enhanced by stirring as revealed by the increased synthesis yield with the increase of stirring speed. At 180 °C and 6 h of hydrothermal treatment, the stirring had no observable effect on phase and particle morphology. At shorter time or lower temperature, the stirring had significant effect on enhancing crystallization of the nanorods.