Rapid Stirring Research Articles

Pengaruh pH dan Dosis Koagulan Ekstrak Biji Kelor dalam Koagulasi terhadap Pengurangan Kekeruhan Limbah Cair

The presence of suspended and colloidal particles in water can cause turbidity. To reduce the turbidity, coagulation–flocculation process is commonly used. In this process, the colloidal particle is converted into flocs which easily separated from water with the aid of coagulant. One of the natural coagulants that have been studied as water purifier is Moringa oleifera seeds. This research aims to reduce turbidity of kaolin synthetic wastewater through coagulation–flocculation process using Moringa oleifera seeds that have been extracted with NaCl 1 M. The variables used in this study were wastewater pH (3, 6, 10, and 12) and coagulant dosage (0, 1, 2, 3, 4, and 5 mL/L). Coagulation-flocculation was taken place in Jar Test with rapid stirring 150 rpm in 2 minutes, followed by slow stirring 30 rpm in 30 minutes, and sedimentation for 30 minutes. Then, the water was analyzed using Turbidimeter. The results showed that coagulant dosage and pH affected the effectiveness of coagulation in decreasing turbidity. The optimum dosage of extracted Moringa oleifera seeds coagulant in coagulation of kaolin synthetic wastewater at pH 3, 6, 10, and 12 were 2 ml/L, 3ml/L, 2 ml/L, and 4 ml/L, respectively .

Dual Liquid Junction Photoelectrochemistry: Part I. Dual-Cuvette and Dual-Thin-Film Cells for Screening and Quantification of Back-Contact Properties

We explore methods for utilizing electrochemical redox contacts both at the front and back of illuminated semiconductors. A dual cuvette cell utilizes a cuvette/gasket/semiconductor/gasket/cuvette sandwich with rapid stirring and the capability for four-electrode measurements. Results from the dual-cuvette cell include current density–potential (J–E) scans with a cobaltocene+/0 back contact to n–Si(111) and a ferrocene+/0 front contact facing the illumination source, and a logarithmic plot of short-circuit current density vs open-circuit photovoltage for several illumination intensities to quantify the diode ideality factor for this cell. An ITO/liquid/semiconductor/liquid/ITO sandwich in a two-electrode configuration comprises a thin-layer cell. Thin-layer cell results include J–E scans as well as electrochemical impedance/Mott-Schottky analysis of flatband potentials. Results on n–Si(111) electrodes with two liquid junction contacts resemble results from traditional photoelectrochemical cells with a rectifying liquid-junction front contact and a rear metal contact.

无机高分子混凝剂聚合硫酸铝铁的制备及其应用研究

本实验采用FeSO4∙7H2O、Al2(SO4)3∙12H2O为原料，以浓硝酸为强氧化剂，Na2HPO4为稳定剂，制备出了一种高聚态铁基混凝剂聚合硫酸铝铁(PAFS)。为验证其混凝性能的优劣，将制备出的高分子复合混凝机以有机腐殖酸为对象进行去除实验。考察了反应温度、Al/Fe摩尔比、P/Fe摩尔比和OH/(Fe + Al)摩尔比4个因素对PAFS混凝效果的影响，通过红外光谱对其形态结构进行表征。研究结果表明：当微波引发时间为5 min，反应温度为60˚C，合成时间为2 h，Al/Fe摩尔比0.4，P/Fe摩尔比为0.2，OH/(Fe + Al)摩尔比为0.4时，混凝剂的混凝性能最优。红外光谱分析表明，PAFS中含有以羟基桥联的铁和铝的聚合物，使得混凝剂具有较好的絮凝效果。且将PAFS用于处理腐殖酸溶液时，当快搅速度为350 rpm，快搅时间为3 min，慢搅速度为40 rpm，慢搅时间12 min，混凝剂投加量12.8 mg/L，pH为8时，腐殖酸去除率达到81%，且存在一定浓度的Mn2+可以提高PAFS对腐殖酸的去除效果。 In this paper, FeSO4∙7H2O and Al2(SO4)3∙12H2O were taken as the raw material, concentrated nitric acid as a strong oxidant and Na2HPO4 as stabilizer to produce poly aluminum ferric sulfate (PAFS) flocculants. In order to test the coagulation effect, the flocculants was applied to the removal of organic humic acid. The coagulation effect was examined with an emphasis on reaction temperature, Al/Fe molar ratio, P/Fe molar ratio and OH/(Fe + Al) mole ratio. The structure and morphology of PAFS were characterized by means of Fourier transform infrared spectrophotometer (FTIR). The results show that the product have the best coagulation effect when the microwave initiation time, reaction temperature, reaction time, Al/Fe molar ratio, P/Fe molar ratio and OH/(Fe + Al) molar ratio are 5 min, 60˚C, 2 h, 0.4, 0.2 and 0.4, respectively. Infrared spectrum analysis shows that PAFS containing hydroxyl polymer bridging of iron and aluminum, makes a better coagulation performance. The removal rate of humic acid reachs 81% when the dosage of PAFS is 12.8 mg/L, pH value is 8, rapid stirring speed is 210 rpm, fast mixing time is 3.0 min, the slow stirring speed is 50 rpm and slow stirring time is 12 min. With the concentration of Mn2+, the removal efficiency of humic acid and fulvic acid increased.

Telenursing in e-health - determinants for future forward

Telenursing is a subgroup of telehealth. The nursing profession while working closely with rural/remote families promotes social aspects of family health meeting the social and psychological needs; ensures that the policies and practices be culturally sensitive and effective in local setting towards making more informed healthcare decisions. Though groundwork in e-health, it can support the delivery of healthcare in the country, thereby supporting individuals and community development, it is also expected at the same time that rapport with and attitude towards the consumers greatly influences the acceptability of services provided by the healthcare provider. Various studies support the hypothesis that attitude of the staff in government agencies is not consumer friendly (Sharma and Singh, 2012). To respond to rapid stirring opportunities with an understanding of transformative technologies and reducing the complexity of adoption would sustain its lasting benefits to the rural and remote location networking for effective, quality, specialised healthcare services/facilities etc.

Controlled synthesis of monodispersed mesoporous silica nanoparticles: Particle size tuning and formation mechanism investigation

In this work, systematic studies were performed to investigate the effects of experimental parameters (e.g. reaction temperature, stirring rate and concentration of triethanolamine (TEA)) on the particle sizes of mesoporous silica nanoparticles (MSNs). Results revealed that the stirring rate played a key role in the size-controlling of MSNs. Additionally, both the reaction temperature and the concentration of TEA showed relatively obvious influence on the sizes of MSNs. We supposed that the MSNs particles were formed by the aggregation and condensing of silica-surfactant micelles and the diameters of MSNs were dependent on the concentration of silica-surfactant micelles. In order to obtain MSNs with small sizes, low reaction temperature and rapid stirring rate were adopted to reduce the concentration of silica-surfactant micelles and suppress the growth of MSNs. As a surface capping ligand, TEA could suppress the particle growth and prevent the particle aggregation of MSNs. By simply controlling the synthetic parameters, MSNs with adjustable size from 20 to 110 nm were obtained. Moreover, the obtained MSNs displayed narrow size distribution and well dispersity in water, which made them highly promising in biomedical applications.

Microwave-Assisted Superheating and/or Microwave-Specific Superboiling (Nucleation-Limited Boiling) of Liquids Occurs under Certain Conditions but is Mitigated by Stirring.

Temporary superheating and sustained nucleation-limited “superboiling” of unstirred liquids above the normal atmospheric boiling point have been documented during microwave heating. These phenomena are reliably observed under prescribed conditions, although the duration (of superheating) and magnitude (of superheating and superboiling) vary according to system parameters such as volume of the liquid and the size and shape of the vessel. Both phenomena are mitigated by rapid stirring with an appropriate stir bar and/or with the addition of boiling chips, which provide nucleation sites to support the phase-change from liquid to gas. With proper experimental design and especially proper stirring, the measured temperature of typical organic reaction mixtures heated at reflux will be close to the normal boiling point temperature of the solvent, whether heated using microwave radiation or conventional convective heat transfer. These observations are important to take into consideration when comparing reaction rates under conventional and microwave heating.

Spherical and Porous Particles of Calcium Carbonate Synthesized with Food Friendly Polymer Additives

Porous calcium carbonate particles were synthesized by adding solutions of Ca2+ to solutions of CO32– containing polymeric additives. Under optimized conditions well-defined aggregates of the anhydrous polymorph vaterite formed. A typical sample of these micrometer-sized aggregates had a pore volume of 0.1 cm3/g, a pore width of ∼10 nm, and a specific surface area of ∼25–30 m2/ g. Only one mixing order (calcium to carbonate) allowed the formation of vaterite, which was ascribed to the buffering capacity and relatively high pH of the CO32– solution. Rapid addition of the calcium chloride solution and rapid stirring promoted the formation of vaterite, due to the high supersaturation levels achieved. With xanthan gum, porous and micrometer-sized vaterite aggregates could be synthesized over a wide range of synthetic conditions. For the other food grade polymers, hydroxypropyl methylcellulose (HPMC), methylcellulose (MC), and sodium carboxyl methylcellulose, several intensive and extensive synthetic parameter...

Reaction enhancement of initially distant scalars by Lagrangian coherent structures

Turbulent fluid flows have long been recognized as a superior means of diluting initial concentrations of scalars due to rapid stirring. Conversely, experiments have shown that the structures responsible for this rapid dilution can also aggregate initially distant reactive scalars and thereby greatly enhance reaction rates. Indeed, chaotic flows not only enhance dilution by shearing and stretching but also organize initially distant scalars along transiently attracting regions in the flow. To show the robustness of this phenomenon, a hierarchical set of three numerical flows is used: the periodic wake downstream of a stationary cylinder, a chaotic double gyre flow, and a chaotic, aperiodic flow consisting of interacting Taylor vortices. We demonstrate that Lagrangian coherent structures (LCS), as identified by ridges in finite time Lyapunov exponents, are directly responsible for this coalescence of reactive scalar filaments. When highly concentrated filaments coalesce, reaction rates can be orders of magnitude greater than would be predicted in a well-mixed system. This is further supported by an idealized, analytical model that was developed to quantify the competing effects of scalar dilution and coalescence. Chaotic flows, known for their ability to efficiently dilute scalars, therefore have the competing effect of organizing initially distant scalars along the LCS at timescales shorter than that required for dilution, resulting in reaction enhancement.

The Utilization of Soybean Straw. II. Dissolution & Regeneration of Soybean Straw in LiCl/DMSO

Various soybean straw (stem and pod) samples were dissolved in 8% lithium chloride/dimethyl sulfoxide (LiCl/DMSO) following 4 h of planetary ball-milling. The solubility, extractable lignin yield, and crystal structure of the ball-milled soybean straw were greatly affected by the ball-milling pretreatment. The dissolved soybean straw could be regenerated by being poured into excess distilled water under rapid stirring. The total regenerated fraction yield decreased with the increase in the duration of ball-milling. Approximately 10% to 25% of the straw mass was lost in the dissolution-regeneration procedure. For comparison, ethylenediamine (EDA)-pretreated soybean straw was also completely dissolved in 8% LiCl/DMSO to form a homogeneous solution containing 1% straw after 24 h of continuous stirring. The dissolution-regeneration performance of soybean straw submitted to the EDA pretreatment was quite different due to the lack of vigorous ball-milling.

Performance and Characterization for Blend Membrane of PES with Manganese(III) Acetylacetonate as Metalorganic Nanoparticles

This study describes the preparation, characterization, and evaluation of performance of blend Polyethersulfone (PES) with manganese(III) acetylacetonate Mn(acac)3to produce reverse osmosis blend membrane. The manganese(III) acetylacetonate nanoparticles were prepared by a simple and environmentally benign route based on hydrolysis of KMnO4followed by reaction with acetylacetone in rapid stirring rate. The prepared nanoparticle powder was dissolved in polymer solution mixture to produce RO PES/Mn(acac)3blend membrane, without any treatment of Polyethersulfone membrane surface. The membrane morphology, mechanical properties, and performance were presented. The scanning electron microscopy (SEM) images have displayed a typical asymmetric membrane structure with a dense top layer due to the migration of Mn(acac)3nanoparticles to membrane surface during the phase inversion process. Contact angle measurements have indicated that the hydrophilicity of the membrane was improved by adding Mn(acac)3. AFM images have proved excellent pores size distribution of blend membrane and lower surface roughness compared with bare PES. The desalination test was applied to blend membrane, where the blend membrane provided good performance; particularly, permeate flux was 24.2 Kg/m2·h and salt rejection was 99.5%.

ANALYSIS OF PHOSPHATE IN LIQUID WASTE HOSPITAL

Liquid waste generated by various activities in the hospital environment has the potential to pollute the environment if the parameters contained in it exceeds the specified quality standards. Parameters that most often exceeded the quality standard is phosphate (PO43-). Phosphate which exceeds the limit of 2 mg/L may affect the balance of aquatic ecosystems. One way to lower phosphate levels is using the coagulation flocculation process. This study aims to uncover the root cause of high levels of phosphate and recommendations for decline it and propose to install coagulation flocculation units.Research methodology starts from search and identification of phosphate levels of various source of phosphate in the hospital environment, from sump pit Dapur (Kitchen), sump pit Poli (Polyclinic), sump pit Lucas, sump pit Biara (Monastery), sump pit Genset and sump pit Carolus. Then doing the jar test in coagulation flocculation process using coagulant that is alum and lime with rapid stirring for 60 seconds and slow stirring for 15 minutes. Jar test was used to determine the optimal dose of coagulant for alum dose range between 50-150 (mg/L) and lime between 75-125 (mg/L). Coagulation flocculation units will be built on the largest phosphate producer with sampling as much as 6 times to determine the fluctuations of phosphate. Lab test of phosphate levels were performed using the spectrophotometric of SnCl2 method.The study data include phosphate levels from source of phosphate and phosphate fluctuations in the greatest source. Based on the results the largest source from pond Elisabeth. Jar test process is done by sampling as much as a liter of waste water taken from pond Elisabeth with total discharge of 26,640 L/day. Showed that the initial Phosphate of maximum from 7,1 mg/L decreased to 1,73 mg/L (75,63%) if given the alum dose of 50 mg/L and lime 125 mg/L which generates as much as 7,049 kg of sludge per day. Phosphate of average from 4,58 mg/L decreased to 0,73 mg/L (84,06%) with alum as much as 50 mg/L and lime as much as 75 mg/L which produces sludge as much as 5,378 kg/day. Phosphate of minimum from 2,23 mg/L decreased to 0,14 mg/L (93,72%) if given the alum dose of 50 mg/L and lime 75 mg/L with sludge as much as 4,931 kg/day.

Fluorescence correlation spectroscopy and nonlinear stochastic reaction-diffusion.

The currently existing theory of fluorescence correlation spectroscopy (FCS) is based on the linear fluctuation theory originally developed by Einstein, Onsager, Lax, and others as a phenomenological approach to equilibrium fluctuations in bulk solutions. For mesoscopic reaction-diffusion systems with nonlinear chemical reactions among a small number of molecules, a situation often encountered in single-cell biochemistry, it is expected that FCS time correlation functions of a reaction-diffusion system can deviate from the classic results of Elson and Magde [ Biopolymers 1974, 13, 1 - 27]. We first discuss this nonlinear effect for reaction systems without diffusion. For nonlinear stochastic reaction-diffusion systems, there are no closed solutions; therefore, stochastic Monte Carlo simulations are carried out. We show that the deviation is small for a simple bimolecular reaction; the most significant deviations occur when the number of molecules is small and of the same order. Our results show that current linear FCS theory could be adequate for measurements on biological systems that contain many other sources of uncertainties. At the same time, it provides a framework for future measurements of nonlinear, fluctuating chemical reactions with high-precision FCS. Extending Delbrück-Gillespie's theory for stochastic nonlinear reactions with rapid stirring to reaction-diffusion systems provides a mesoscopic model for chemical and biochemical reactions at nanometric and mesoscopic levels, such as a single biological cell.

Role of mixing conditions on coagulation performance and flocs breakage formed by magnesium hydroxide

The breakage and re-growth of flocs formed by magnesium hydroxide were evaluated for coagulation of kaolin suspension under high pH. A series of jar experiments were conducted to investigate the impacts of mixing conditions on coagulation performance and magnesium hydroxide-kaolin floc properties. Flocculation index (FI) value was then discussed with controlled experiments using on-line intelligent particle dispersion analyzer (iPDA) and optimum coagulant dose of 14.4mg/L (magnesium ion) was obtained. The results showed that one time addition feeding mode lead to relatively large floc size at first stage compared with dropwise addition mode. Ultrasonic disruption led to small flocs and prolonged ultrasonic time gave poorer coagulation performance. Increasing rapid mixing speed led to a decrease in the final floc size. Breakage and recovery factors decreased with the increase of rapid stirring speed. The experiments also showed that magnesium hydroxide coagulation process including fast floc formation and growth of flocs and then larger flocs break into relative small particles. All of the flocs under investigation showed a limited capacity to re-growth when they had been previously broken.

Chaotic advection in a steady, three-dimensional, Ekman-driven eddy

AbstractWe investigate and quantify stirring due to chaotic advection within a steady, three-dimensional, Ekman-driven, rotating cylinder flow. The flow field has vertical overturning and horizontal swirling motion, and is an idealization of motion observed in some ocean eddies. The flow is characterized by strong background rotation, and we explore variations in Ekman and Rossby numbers, $E$ and ${R}_{o} $, over ranges appropriate for the ocean mesoscale and submesoscale. A high-resolution spectral element model is used in conjunction with linear analytical theory, weakly nonlinear resonance analysis and a kinematic model in order to map out the barriers, manifolds, resonance layers and other objects that provide a template for chaotic stirring. As expected, chaos arises when a radially symmetric background state is perturbed by a symmetry-breaking disturbance. In the background state, each trajectory lives on a torus and some of the latter survive the perturbation and act as barriers to chaotic transport, a result consistent with an extension of the KAM theorem for three-dimensional, volume-preserving flow. For shallow eddies, where $E$ is $O(1)$, the flow is dominated by thin resonant layers sandwiched between KAM-type barriers, and the stirring rate is weak. On the other hand, eddies with moderately small $E$ experience thicker resonant layers, wider-spread chaos and much more rapid stirring. This trend reverses for sufficiently small $E$, corresponding to deep eddies, where the vertical rigidity imposed by strong rotation limits the stirring. The bulk stirring rate, estimated from a passive tracer release, confirms the non-monotonic variation in stirring rate with $E$. This result is shown to be consistent with linear Ekman layer theory in conjunction with a resonant width calculation and the Taylor–Proudman theorem. The theory is able to roughly predict the value of $E$ at which stirring is maximum. For large disturbances, the stirring rate becomes monotonic over the range of Ekman numbers explored. We also explore variation in the eddy aspect ratio.

Preparation of manganese (III) acetylacetonate nanoparticles via an environmentally benign route

With the hope of overcoming the generation of hazardous materials to human health and environment, serious and great endeavor have been made in catalyst fabrication using green chemistry technology. In this paper, the manganese (III) acetylacetonate nanoparticles with diameters of about 146 nm were prepared by a simple and environmentally benign route based on hydrolysis of KMnO4 followed by reaction with acetylacetone in rapid stirring rate or ultrasonication. The as-prepared samples were characterized by X-ray diffraction, energy dispersive X-ray fluorescence (EDIX), Fourier transfer infrared spectroscopy and scanning electron microscope. Various parameters were investigated, and the pure and stable crystals of manganese (III) acetylacetonate could be obtained in 98% conversion at a molar ratio 7:1 of acetylacetone to KMnO4 and 75°C after 60 min. We further proposed a mathematical model, and the predicted results from model were in good agreement with experimental results.

One‐Pot Synthesis of Phenylmethanethiolate‐Protected Au20(SR)16 and Au24(SR)20 Nanoclusters and Insight into the Kinetic Control

We report two synthetic routes for concurrent formation of phenylmethanethiolate (-SCH2Ph)-protected Au20(SR)16 and Au24(SR)24 nanoclusters in one-pot by kinetic control. Unlike the previously reported methods for thiolate-protected gold nanoclusters, which typically involve rapid reduction of the gold precursor by excess NaBH4 and subsequent size focusing into atomically monodisperse clusters of a specific size, the present work reveals some insight into the kinetic control in gold-thiolate cluster synthesis. We demonstrate that the synthesis of -SCH2Ph-protected Au20 and Au24 nanoclusters can be obtained through two different, kinetically controlled methods. Specifically, route 1 employs slow addition of a relatively large amount of NaBH4 under slow stirring of the reaction mixture, while route 2 employs rapid addition of a small amount of NaBH4 under rapid stirring of the reaction mixture. At first glance, these two methods apparently possess quite different reaction kinetics, but interestingly they give rise to exactly the same product (i.e., the coproduction of Au20(SCH2Ph)16 and Au24(SCH2Ph)20 clusters). Our results explicitly demonstrate the complex interplay between the kinetic factors that include the addition speed and amount of NaBH4 solution as well as the stirring speed of the reaction mixture. Such insight is important for devising synthetic routes for different sized nanoclusters. We also compared the photoluminescence and electrochemical properties of PhCH2S-protected Au20 and Au24 nanoclusters with the PhC2H4S-protected counterparts. A surprising 2.5 times photoluminescence enhancement was observed for the PhCH2S-capped nanoclusters when compared to the PhC2H4S-capped analogues, thereby indicating a drastic effect of the ligand that is merely one carbon shorter.

Study on Flocculation Process and Optimal Stirring Speed of Compound Traditional Chinese Medicine

In order to optimize the flocculation process of compound traditional Chinese medicine and improve the clarity and quality of solution, the natural macromolecule flocculant chitosan was used to flocculate the compound traditional Chinese medicine Shuangsang soup. In the analysis of different factors affecting the flocculation effect, grain size analysis method was used to focus on the influence of stirring speed on flocculation effect. Finally, the optimal flocculation conditions were obtained by orthogonal experiment as follows: the dosage of chitosan was 0.385g/L, the temperature was 40°C, the stirring speed was 30r/ min, at the same time, the stirring method, which is first rapid stirring with 60s, and then slow stirring with 240s was applicated during mixing the solution. The results showed that, with this process condition, not only the effective component loss rate of compound traditional Chinese medicine Shuangsang soup was reduced to a minimum; the flocculating rate was raised to the highest, but also the energy could be saved, the production cost could be reduced, in the end, the process optimization was truly achieved.

Carbon nanoparticles-induced formation of polyaniline nanofibers and their subsequent decoration with Ag nanoparticles for nonenzymatic H2O2 detection

The present communication reports on the preparation of polyaniline nanofibers (PANINFs) by chemical oxidative polymerization of aniline under rapid stirring using ammonium persulfate as the oxidant in acidic aqueous media in the presence of carbon nanoparticles. The subsequent treatment of such nanofiber with a AgNO3 aqueous solution leads to in situ chemical reduction of Ag+ on them to form Ag nanoparticle-decorated PANINFs. The resultant composites show good catalytic activity toward the reduction of H2O2. An effective enzymeless H2O2 sensor based on such composites is also constructed. It exhibits a fast amperometric response time 2 s, and it has a linear detection range from 0.1 to 60 mM and detection limit of 0.9 μM at a signal-to-noise ratio of 3, respectively.

Study on Energy Consumption Distribution of High Ferric-Based Silicon Coagulant Using Fractal Dimension

High ferric-based silicon coagulant is a kind of new self-made coagulant. The high ferric content was introduced in the preparation process of the coagulant, and the effect was good in dealing with simulated industrial wastewater with lead. The beaker test indicated that the lead removal rate reached the highest 96.48% when the rapid stirring speed was 300r/min and stirring time was 1min, low stirring speed was 80r/min and stirring time was 15min, the dosage of the coagulant was 3.5ml/L. And the fractal dimension of flocs was 1.67674 under that optimum conditions. The low stirring stage was divided into three different stages in the orthogonal experiment of energy consumption, and the result showed that the optimum combination of flocculation was: velocity gradient G1=67.7s-1, stirring time T1=4min; G2=57.8 s-1, T2=5min; G3=23.9s-1, T3=6min. The removal rate of lead ion improved and the energy consumption decreased when the flocculation was divided into different stages. The relations between fractal dimension and energy consumption distribution can be obtained by calculated the fractal dimension of different stages. The stirring speed can be controlled and the flocs can be prevented from being broken by observing the flocs.

Asymptotic Behaviour of the Critical Value for the Contact Process with Rapid Stirring

We study the behaviour of the contact process with rapid stirring on the lattice $$\mathbb Z ^d$$ in dimensions $$d\ge 3.$$ This process was studied earlier by Konno and Katori, who proved results for the speed of convergence of the critical value as the rate of stirring approaches infinity. In this article we improve the results of Konno and Katori and establish the sharp asymptotics of the critical value in dimensions $$d\ge 3.$$