Increasing Agitation Speed Research Articles

Leaching of tin from waste Pb-free solder in hydrochloric acid solution with stannic chloride

A hydrochloric acid (HCl) leaching process with stannic chloride (SnCl4) was proposed to leach Sn from waste Pb-free solder containing Sn, Ag, and Cu, where the oxidant stannic ion (Sn4+) oxidizes Sn metal into stannous ion (Sn2+). When Sn reagent-grade powder was leached in HCl solution with SnCl4, the leaching efficiency of Sn increased rapidly and the oxidation-reduction potential decreased with leaching time. In the leaching tests of Pb-free solder, the effect of factors such as the agitation speed, HCl concentration, pulp density, and temperature on the leaching behaviors of metals was investigated. The leaching efficiencies of Sn increased rapidly in the beginning of leaching with increasing agitation speed, HCl concentration, and temperature. The difference in the leaching efficiencies was negligible after 90min under the following conditions: HCl concentration of 1–3kmolm−3, agitation speed of 300–600rpm, and temperature of 50°C or 70°C. Although the pulp density was increased from 1% to 2%, the Sn concentration dissolved did not exceed 10,500gm−3 because of the lack of oxidant, and the increase in the initial concentration of Sn4+ as the oxidant could accelerate the leaching of Sn. A Sn leaching efficiency of greater than 99% was achieved in 1kmolm−3 HCl with 10,000gm−3 Sn4+ at 400rpm and 50°C with 1% pulp density within 90min. Ag was not detected in any of the leaching tests. Although the leaching solution contained 24.5gm−3 of Cu, the addition of Sn powder was successful in removing Cu from the solution via a cementation reaction. Thus, a Sn leaching solution was successfully obtained from Pb-free solder via HCl leaching with SnCl4.

Scale-up of high-solid enzymatic hydrolysis of steam-pretreated softwood: the effects of reactor flow conditions

The importance of flow conditions during scale-up of high-solid enzymatic hydrolysis of steam-pretreated spruce was demonstrated by comparing hydrolysis rates between laboratory (2 L) and demonstration (4 m3) scale. A positive effect of increased agitation speed on the rate of enzymatic hydrolysis was found regardless of scale. Importantly, the hydrolysis rate was higher at the larger scale when compared at similar specific power inputs. Changes in the rheological properties of the pretreated material during the hydrolysis were followed by off-line measurements of apparent viscosity. This information was used to estimate the flow conditions in the reactors, i.e., average Reynolds numbers, which together with measured mixing power consumptions enabled a more detailed comparison between the scales. The hydrolysis yields correlated better with average Reynolds numbers than specific power input over the different scales. This indicates that mass transport limitations, caused by insufficient bulk flow, likely play a decisive role in determining the rate of enzymatic hydrolysis.

The effects of temperature and agitation speed on the leaching behaviors of tin and bismuth from spent lead free solder in nitric acid leach solution

Nitric acid leaching was performed to separate tin and bismuth in spent Pb-free solder. The effects of agitation speed and leaching temperatures on the leaching behaviors of tin and bismuth were investigated to recover tin and bismuth from the spent solder, respectively. The leaching efficiency of bismuth increased rapidly with increasing agitation speeds and temperatures, and the efficiency is found to be 97.8% under the following leaching conditions: nitric acid concentration of 1 k mol m− 3, agitation speed of 400 rpm, 1% pulp density, leaching temperature of 90°C, leaching time of 1 hour. In the case of tin, the leaching efficiency increased and then decreased during leaching tests, and a white precipitate was observed in the reactor. XRD results indicate that tin precipitated as stannic acid (SnO2 H2O). Consequently, bismuth and tin could be separated successfully by nitric acid leaching process.

Mechanical and physicochemical contribution in removal of different soil types on cotton fabric

The research was conducted to identify the optimal washing methods for three types of soils, in terms of washing efficiency and eco-efficiency. To this end, the mechanical action by the washer’s agitation and the physicochemical action by detergents were investigated for their respective contribution to the detergency of three kinds of artificial soils: oil, protein, and their mixture. In general, washing efficiency increased with the increased agitation speed and the amount of detergent use. Most of the washing conditions presented a positive synergistic effect when both the mechanical and physicochemical actions were applied simultaneously. The contributing ratio of the physicochemical action was greater for oily soil than for other soil types, due to the effective rolling-up by the detergent for the oily soil. The contributing ratio attributable to the mechanical action was higher when the protein was present in the soil composition, and the mechanical contribution was compromised as detergent usage was increased. The washing condition with the largest synergy did not always correspond with the condition of the highest washing efficiency. Energy Efficiency for Detergency was increased in all soil types as the agitation speed increased. It is suggested that the washing method be determined considering (1) the level of soiling and the acceptable washing performance, (2) the synergistic effect of mechanical and physicochemical actions, and (3) the eco-efficiency of washing methods.

Effect of agitation speed on the morphology of Aspergillus niger HFD5A-1 hyphae and its pectinase production in submerged fermentation.

To investigate the impact of agitation speed on pectinase production and morphological changing of Aspergillus niger (A. niger) HFD5A-1 in submerged fermentation. A. niger HFM5A-1 was isolated from a rotted pomelo. The inoculum preparation was performed by adding 5.0 mL of sterile distilled water containing 0.1% Tween 80 to a sporulated culture. Cultivation was carried out with inoculated 1 × 10(7) spores/mL suspension and incubated at 30 °C with different agitation speed for 6 d. The samples were withdrawn after 6 d cultivation time and were assayed for pectinase activity and fungal growth determination. The culture broth was filtered through filter paper (Whatman No. 1, London) to separate the fungal mycelium. The cell-free culture filtrate containing the crude enzyme was then assayed for pectinase activity. The biomass was dried at 80 °C until constant weight. The fungal cell dry weight was then expressed as g/L. The 6 d old fungal mycelia were harvested from various agitation speed, 0, 50, 100, 150, 200 and 250 rpm. The morphological changing of samples was then viewed under the light microscope and scanning electron microscope. In the present study, agitation speed was found to influence pectinase production in a batch cultivation system. However, higher agitation speeds than the optimal speed (150 rpm) reduced pectinase production which due to shear forces and also collision among the suspended fungal cells in the cultivation medium. Enzyme activity increased with the increasing of agitation speed up to 150 rpm, where it achieved its maximal pectinase activity of 1.559 U/mL. There were significant different (Duncan, P < 0.05) of the pectinase production with the agitation speed at static, 50, 100, 200 and 250 rpm. At the static condition, a well growth mycelial mat was observed on the surface of the cultivation medium and sporulation occurred all over the fungal mycelial mat. However with the increased in agitation speed, the mycelial mat turned slowly to become a single circular pellet. Thus, it was found that agitation speed affected the morphological characteristics of the fungal hyphae/mycelia of A. niger HFD5A-1 by altering their external as well as internal cell structures. Exposure to higher shear stress with an increasing agitation speed could result in lower biomass yields as well as pectinase production by A. niger HFD5A-1.

Selective and Effective Reduction of Gold Ions from Acidic HCl–NaClO3 Leachate with Oxalic Acid

The reduction of gold ions from HCl–NaClO3 leaching solution with oxalic acid was performed. It was found that, for 50 mL of gold-containing leaching filtrate, 20 mL of 6% (w/v) oxalic acid was required to achieve a selective and effective reduction of gold ions. The reaction temperature and time were found to have significant effects on gold reduction, and the optimal values were determined to be 85 °C and 2 h, respectively. The reduction of gold increased with increasing agitation speed and speed of addition of oxalic acid, and the optimal values were 180 rpm and 1.740 mL/min or more, respectively. Under the optimal conditions, the reductions of Au3+, Cu2+, Fe3+, Pb2+, Ag+, and Si4+ were 95.56%, 0.66%, 2.33%, 1.40%, 0.70%, and 0.50%, respectively. The appropriate solution acidity and solution potential, which are two important conditions for achieving the selective reduction of gold ions, were about 623 mV and 2.3–3.3 M, respectively.

Pineapple leaf (Ananas comosus) powder as a biosorbent for the removal of crystal violet from aqueous solution

Dyes are present in the industrial effluents which need to be treated before discharging to the environment as they pose severe environmental and health impacts. For this, biosorption has been considered as an economic and efficient technology as compared to the other treatment processes. Thus, biosorption characteristics of Ananas comosus (pineapple) leaf powder (PLP) was investigated for decolorization of crystal violet (CV), a cationic dye from its aqueous solutions employing a batch experimental setup. The parameter studied included contact time, initial dye concentration, adsorbent dose, pH, agitation speed, particle size of adsorbent, and temperature. Different isotherm models, Langmuir, Freundlich, Dubinin–Radushkevich, and Temkin were found. Maximum adsorption was found with <150 μ particle sized 50 mg of PLP at 30°C with 200 rpm at pH 8. The maximum adsorption capacity (qm) was found to be 158.73 mg/g. Lagergen pseudo-second-order model best fits the kinetics of adsorption. Intra particle diffusion plot showed boundary layer effect and larger intercepts indicates greater contribution of surface sorption in rate-determining step. Adsorption of CV on adsorbents was found to increase on decreasing initial concentration, increasing pH up to 8, decreasing temperature, increasing agitation speed, and decreasing particle size. Overall, the present findings suggest that PLP is environmentally friendly, efficient, and low-cost biosorbent which is useful for the removal of CV from aqueous media.

Effects of fabricated technology on particle size distribution and thermal properties of stearic–eicosanoic acid/polymethylmethacrylate nanocapsules

Polymethyl methacrylate (PMMA) encapsulated eicosanoic–stearic acid (EA–SA) eutectic nanocapsules were prepared by ultraviolet photoinitiated emulsion polymerization and various characterization techniques were employed to investigate the influence of preparation methods on thermal properties and particle size distribution (PSD). The results show that the particle size decreased and PSD narrowed with the increase of agitation speed, reduction of initiator and monomer concentration, existence of cross-linking agent and stabilized at agitated speed higher than 5000rpm and monomer concentration lower than 0.15mol/L. However, latent heats of the capsules decreased with the increase of monomer and initiator concentration. Type of emulsifier in emulsion has significant effects on PSD and phase change properties of EA–SA/PMMA and nonionic emulsifier is suitable for reducing particle size and enhancing heat storage ability. Morphology and chemical characteristic analysis indicate that spherical nanocapsules with average diameter of 46nm were successfully fabricated and its maximum encapsulation ratio is 68.8wt% without leakage of core material. The melting and crystallizing temperatures and latent heats of capsules were determined as 56.9°C and 54.5°C, 126.4J/g and 128.3J/g, respectively. Accelerated thermal cycling test shows that the nanocapsules have good thermal and chemical reliability after repeated thermal cycling. Besides, the super-cooling problem of PCMs reduced dramatically by forming nanocapsules.

Enhanced riboflavin production by recombinant Bacillus subtilis RF1 through the optimization of agitation speed

Dissolved oxygen is one of the most important bioprocess parameters that could affect cell growth and product formation, and it is easy to control by changing agitation speed. In this work, the effects of agitation speed on the performance of riboflavin production by recombinant Bacillus subtilis RF1 was investigated in fed-batch fermentation. The lower agitation speed (600 rpm) was beneficial for cell growth and riboflavin biosynthesis in the initial phase of fermentation process. While, during the later phase, higher agitation speed (900 rpm) was favor for cell growth and riboflavin biosynthesis. Thus, a two-stage agitation speed control strategy was proposed based on kinetic analysis, in which the agitation speed was controlled at 600 rpm in the first 26 h and then switched to 900 rpm to maintain high μ for cell growth and high q(p) for riboflavin production during the entire fermentation process. However, it was observed that a sharp increase of agitation speed resulted in an adverse effect on cell growth and riboflavin synthesis within a short time. To avoid this phenomenon, a multi-stage agitation speed control strategy was set up based on the two-stage control strategy, the maximum concentration of riboflavin reached 9.4 g l(-1) in 48 h with the yield of 0.051 g g(-1) by applying this strategy, which were 20.5 and 21.4% over the best results controlled by constant agitation speeds.

Bengal gram seed husk as an adsorbent for the removal of dyes from aqueous solutions – Equilibrium studies

Seed husk of Bengal gram (SHBG) (Scientific Name: Cicer arietinum) was used as an adsorbent for the removal of a direct dye namely Congo red (CR), two basic dyes namely methylene blue (MB) & rhodamine-B (RB) and an acidic dye namely acid blue 25 (AB) from aqueous solutions with equilibrium isotherms. The effect of particle size, of mass of adsorbent, of agitation speed of shaker and of temperature of dye solutions was studied for understanding the interaction of dyes with adsorbent. The uptake of dyes by the adsorbent was increasing with increasing mass of the adsorbent, decreasing with increasing size of the adsorbent, and increasing with increasing agitation speed and temperature. The adsorption capacity for each dye-adsorbent system was determined by using the Langmuir isotherm. The adsorption capacity of adsorbent for MB, RB, CR and AB was 333.33, 133.34, 78.12 and 5.56mgg−1, respectively. The experimental data fit well with the Langmuir and Freundlich models. The standard enthalpy change of adsorption for MB, RB, CR and AB was 13.5, 10.97, 4.01 and 6.72kJmol−1, respectively. The average standard entropy change of adsorption for MB, RB, CR and AB is 58.2957, 36.869, 13.2138 and −3.4179kJmol−1, respectively. The adsorption of two basic dyes is much higher than that of the direct and acid dyes.

Study on Size and Density Distribution in Fine Coal Flotation

Mineral composition, size fraction, and density distributions of a fine coal sample were used to determine its floatability and quality characteristics. Flotation rate tests were conducted using different agitation speeds of flotation machines. The results showed that the ash of clean coal product increased gradually with increasing agitation speed and the floatability of coal became poor. The higher the agitation speed, the faster the flotation rate was. For coarse size coal with higher density, the recovery was low. For the same size particle and density, the higher the agitation speed, the higher the recovery. The relationship between energy (E) and recovery (ϵ) were estimated through the cubic expression. The model parameters were calculated using software MATLAB7.0. The experimental data of various size fractions showed that the fitting of the model was very good.

Fluidization Characteristics of Nano Particles with the Assist of Stirrer

Fluidizationof ultrafine solidparticles iswidelyusedin a varietyofindustrial applicationsbecauseofitsunusualcapabilityofcontinuouspowderhandling, good mixing,large gas- solidcontactarea,andveryhigh ratesofheatandmass transfer.As theparticlesizedecreases thecohesive forces betweenparticlesincreases.Therefore,fluidization of ultrafineparticles becomes much moredifficultas compared to thelargersizeparticlesanditneeds efficient method. In thepresentwork, the fluidizationexperimentswereconducted usingairas fluidizingmediaand SiO2, ZnO and Al2O3 nano particles, with a size ranging from 15 to 30 nmin2-dimensional fluidizedbedwiththe assist of stirrer. The fluidization behavior of the nanoparticle, including the fluidization regime, the minimum fluidization velocity, and the bed expansion are also investigated. .The results showed that smoother fluidization was observed with increasing agitation speed, because the agglomeration and channeling were reduced by the mechanical agitation. Itwas found that with the assist of stirrer ,by increasing in the speed of stirrer initial bed voidage increased and terminal velocity and agglomerate

OPTIMIZATION OF AGITATION AND INCUBATION PERIOD ON PRODUCTION OF MANNANASE BY BACILLUS VELEZENSIS NRC-1 USING BENCH-SCALE BIOREACTOR

The effect of agitation speed and incubation period on the production of mannanase enzyme by Bacillus velezensis NRC-1 using bench-scale bioreactor at 45oC was investigated. Results revealed that the increase in agitation speed from 200 to 800 rpm resulted in a significant increase in mannanase production to 21.04 U/mL. The increase in agitation speed affected dissolved oxygen (DO) concentration which in turn affected cell growth and mannanase production. The maximum mannanase production in the bioreactor was attained after 72 h of incubation at 45 oC. Mannanase activity in the bioreactor (21.04 U/mL) while much higher than that obtained from the shake flask fermentation (15.6 U/mL) also the incubation period decreased from 7 days in shake flask fermentation to 3 days in bioreactor.

Preparation of porous, nano-sized urea–formaldehyde polymer powder

Nano-sized, porous urea–formaldehyde polymer powder was created by variations of an existing reaction. Formaldehyde was reacted with urea at or below the equimolar stoichiometric ratio. The resulting amorphous white powder did not generate formaldehyde. Increased agitation speed during the generation of polymethylene urea restricted the polymer particles’ growth and introduced porosity. Adding sodium dodecyl benzene sulfonate surfactant at agitation speeds over 1500rpm resulted in 1–5μm spherical, porous particles. Adding water glass during the synthesis of polymethylene urea (PMU) limited particles’ growth and facilitated uniform porosity. The polymer powder showed wide potential applicability, e.g. polymer fillers and pigments.

A Novel Agricultural Waste Adsorbent, Watermelon Shell for the Removal of Copper from Aqueous Solutions

The present study deals with the application of Watermelon Shell, an agricultural waste, for the adsorptive removal of Cu(II) from its aqueous solutions. This paper incorporates the effects of time, dose, temperature, concentration, particle size, agitation speed and pH. Analytical techniques have been employed to find pore properties and characteristics of adsorbent materials. Batch kinetic and isotherm studies have also been performed to understand the ability of the adsorbents. The adsorption behavior of the Cu(II) has been studied using Freundlich, Langmuir and Tempkin adsorption isotherm models. The monolayer adsorption capacity determined from the Langmuir adsorption equation has been found as 111.1 mg/g. Kinetic measurements suggest the involvement of pseudo-second-order kinetics in adsorptions and is controlled by a particle diffusion process. Adsorption of Cu(II) on adsorbents was found to increase on decreasing initial concentration, increasing pH up to 8, increasing temperature, increasing agitation speed and decreasing particle size. Overall, the present findings suggest that watermelon outer shell is environmentally friendly, efficient and low-cost biosorbent which is useful for the removal of Cu(II) from aqueous media.

Influence of Agitation Speed on Tannase Production and Morphology of Aspergillus niger FETL FT3 in Submerged Fermentation

Agitation speed was found to influence the tannase production and fungal growth of Aspergillus niger FETL FT3. The optimal agitation speed was at 200 rpm which produced 1.41 U/ml tannase and 3.75 g/l of fungal growth. Lower or higher agitation speeds than 200 rpm produced lower enzyme production and fungal growth. Based on the SEM and TEM micrograph observation, there was a significant correlation between agitation speed and the morphology of the fungal mycelia. The results revealed an increase of the enzyme production with the change of the fungal growth morphology from filamentous to pelleted growth forms. However, the exposure to higher shear stress with an increasing agitation speed of the shaker also resulted in lower biomass yields as well as enzyme production.

Impact of agitated drying on the powder properties of an active pharmaceutical ingredient

In this study, the impact of agitated drying on the physical and bulk powder properties of an active pharmaceutical ingredient (API) is presented. The effects of different agitated drying conditions such as agitation rate, drying temperature, drying time pre-agitation, drying time during agitation and number of solvent wash cycles on the bulk density, millability, flow and specific surface area is reported. The crystal morphology is altered from fibrous needles to agglomerates when switching from tray to agitated drying. An increase in bulk density and specific surface area was evident when using agitated drying compared to tray drying as hard coarse granules were produced with an increase in the number of fine particles < 10 μm. The bulk density was found to increase with an increase in agitation speed, drying time and number of solvent wash cycles used during filtration. Controlling both fine and coarse particle size of the granules for this API during agitated drying was difficult to achieve due to the fibrous crystal habit. However, the increase in the bulk density observed has the potential to facilitate improvements in the ease of drug product development. In the case of this system further particle size control was required through the use of dry milling.

Structural stability of white sauces prepared with different types of fats and thawed in a microwave oven

This paper describes the microstructure and dielectric properties of white sauces prepared with different fats (sunflower oil, olive oil, soy oil, and butter) and agitation speeds (350, 1100 and 3250 rpm). The structural stability of sauces during thawing using conventional oven (CO) and microwave oven (MO) are studied. The results showed that, for fresh samples (not subjected to the freeze–thaw cycle) an increase in agitation speed during elaboration from 350 to 1100 rpm caused a significant decrease ( p < 0.05) in the fat globules area – regardless of the type of fat used; in the samples with sunflower and olive oils, a significant increase ( p < 0.05) in the fat globules circularity and dielectric properties (dielectric constant and loss factor) was also produced. The thawing method used did not significantly ( p > 0.05) affect fat globule size and shape, regardless of the agitation speed and type of fat. Sauces that were stable during the freeze–thaw cycle were obtained using speeds of 1100 and 3250 rpm.

10.2478/s11814-009-0237-0

Optimization of the production of antifungal lipopeptide, iturin A, by B. subtilis was carried out in submerged cultural fermentation. In a shake-flask experiment, response surface methodology (RSM) was employed to optimize the cultivation conditions of Bacillus subtilis S3 for the enhancement of iturin A production. The optimal conditions for iturin A production obtained from RSM were pH 6.0, 0.93% maltodextrin, 1.11% glucose, 0.72% corn steep powder (C.S.P), 1.5 mM MgSO4, 0.75 mM KH2PO4, rotation speed 180 rpm and area of aeration 4.35 cm2. 57% increase of iturin A productivity (from 47.19 mg/L to 74.22 mg/L) was observed using the one-factor-at -a-time technique; however, 180% increase of iturin A productivity (from 47.19 mg/L to 132.23 mg/L) was observed with RSM. The iturin A production was further studied in a 5-L fermentor with a variation of agitation speed, aeration and baffles. In the 5-L fermentor, it was found that increased agitation speed improved the growth of B. subtilis and the production of iturin A. Aeration at 2 vvm gave excellent production of iturin A (175.52 mg/L) at 6 d of fermentation. The addition of baffles in the fermentor has significantly influenced the oxygen mass transfer coefficient (KLa) and iturin A production.

Production of antifungal lipopeptide from Bacillus subtilis in submerged fermentation using shake flask and fermentor

Optimization of the production of antifungal lipopeptide, iturin A, by B. subtilis was carried out in sub- merged cultural fermentation. In a shake-flask experiment, response surface methodology (RSM) was employed to optimize the cultivation conditions of Bacillus subtilis S3 for the enhancement of iturin A production. The optimal conditions for iturin A production obtained from RSM were pH 6.0, 0.93% maltodextrin, 1.11% glucose, 0.72% corn steep powder (C.S.P), 1.5 mM MgSO4, 0.75 mM KH2PO4, rotation speed 180 rpm and area of aeration 4.35 cm 2 . 57% increase of iturin A productivity (from 47.19 mg/L to 74.22 mg/L) was observed using the one-factor-at -a-time tech- nique; however, 180% increase of iturin A productivity (from 47.19 mg/L to 132.23 mg/L) was observed with RSM. The iturin A production was further studied in a 5-L fermentor with a variation of agitation speed, aeration and baffles. In the 5-L fermentor, it was found that increased agitation speed improved the growth of B. subtilis and the production of iturin A. Aeration at 2 vvm gave excellent production of iturin A (175.52 mg/L) at 6 d of fermentation. The addition of baffles in the fermentor has significantly influenced the oxygen mass transfer coefficient (KLa) and iturin A production.