Flocculation and rheology of kaolinite/quartz suspensions

Rheological properties of suspensions of Na-kaolinite and colloidal quartz (Min-U-Sil) at constant overall volume concentration of 2% are determined with a Weissenberg Rheogoniometer using a combined Couette and cone-and-plate geometry. The results are interpreted in terms of the flocculation behaviour of the constituent particles in the presence of high salt concentrations (0.1–0.75m NaCl) at pH 6, 7 and 8. In these chemical environments these suspensions are pseudoplastic for much of the range of mixture compositions becoming Newtonian for suspensions containing only quartz. These properties reflect the dominant influence of interactions between kaolinite particles on the flocculation behaviour of the mixture.Nomenclature a ₁, a₂ radii of spheres - A Hamaker constant - b radius of cylinder - C volumetric solids concentration - e ₀ electronic charge - H ₀ shortest distance between surfaces - I ionic strength - J collision frequency per unit volume - k Boltzmann constant - l length of cylinder - m number in eq. (2) - N particle number concentration - S (H ₀ + b)/b in eq. (4) - T absolute temperature - U electrophoretic mobility - V _A van der Waals attractive energy - V _R coulombic energy - V _T total energy of interaction - X H ₀/2a₁ in eq. (5) - Y a ₂/a₁ in eq. (5) - thickness of plate - shear rate - permittivity - zeta potential - k Debye-Hückel parameter - µ dynamic viscosity - µ _pl plastic viscosity - v valency of counter ion - shear stress - _B Bingham stress - ₁, ₂ dimensionless potentials - ₁, ₂ surface potentials     

Synthesis of nanocomposites from cationic polyacrylamide and modified carbon black: Application as flocculants for oily sludge suspension

Carbon black was modified using various liquid‐phase oxidation methods (modified carbon black = m‐CB, m = (1, 2, 3): 1, sulfuric acid/potassium permanganate method; 2, nitric acid method; 3, hydrogen peroxide method). With acetone–ethylene glycol as initiator, dimethyldiallylammonium chloride (DMDAAC) and acrylamide (AM) as monomer, cationic polyacrylamide (CPAM) was prepared by UV excitation of the monomer. The m‐CB/CPAM nanocomposites were synthesized using a hydrothermal method. The factors that affected the molecular weight of CPAM were investigated, including the total monomer concentration, the dosage of the complex initiator, the mass ratio of m_AM:m_DMDAAC and the UV irradiation time. The chemical structures and morphologies of the samples were characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, elemental composition, X‐ray diffraction and scanning electron microscopy. 1‐CB/CPAM was utilized to flocculate oil sludge suspension, and the effects of 1‐CB quality, 1‐CB/CPAM dosage, temperature and pH value on the flocculation performance of 1‐CB/CPAM were investigated. The flocculation mechanism of 1‐CB/CPAM was also analyzed. The results show that 1‐CB/CPAM has an outstanding flocculation effect, and it flocculates oil sludge particles by adsorption bridging and charge neutralization in acidic and alkaline conditions.     

Demulsification of Gas Oil/Water Emulsion via High-Intensity Ultrasonic Standing Wave

High-intensity ultrasonic standing wave field was established in a horizontal direction and its effect on “gas oil” in “water” emulsion separation rate was studied. Also, effects of four parameters on emulsion instability behavior were investigated: ultrasound irradiation time (5–30 min), emulsion position in ultrasound field (17–37 cm), ultrasound input intensity (20, 45, and 75%) and dispersed phase concentration (0.5, 2, and 10%). Emulsion light absorbance, droplet diameter and distribution were measured to analyze separation efficiency. The optimum states were 10% oil in water emulsion treated at 17 cm distance from ultrasound source under 30 minutes irradiation time and 20% sound intensity.     

BEHAVIOR OF ANIONIC SURFACTANT MICELLES IN THE PRESENCE OF Al3+ AND Ca2+

The estimation of the C-potential of ionic surfactant micelles may be useful for the study of adsorption of solutes onto the micellar surface, which causes a reduction of the net electrostatic charge. This work presents results on the variation of ζ-potential of alkylsulfate and fatty carboxylate micelles with the bulk concentrations of Al³⁺ and Ca²⁺ cations. Combined with results from the literature about the effect of micellar surfactant concentration on reducing surfactant precipitation in the presence of polyvalent cations, these allow to conclude that micelles of anionic surfactants will have a higher chance of electroneutralization of their surface charge by adsorbing cations if the end functional group of the surfactant is smaller.     

Isolation and Characterization of Cellulosic Pulp Fines and Their Interactions with Cationic Polyacrylamides

Four different types of cellulosic fines were isolated from refiner mechanical and kraft pulp samples to characterize their chemical and physical properties. The pulp fines were flocculated using four different types of cationically modified polyacrylamides. The extent of flocculation was observed with multiple light scattering apparatus. The maximum adsorption of the polyelectrolytes on the pulp fines was determined by polyelectrolyte titration. It was concluded that it is the combination of the molar mass and the charge density of a polyelectrolyte, as well as the origins and characteristics of the fines which define the adsorption and flocculation behavior. None of these properties alone could fully describe these phenomena, but the molar mass of the polyelectrolyte was the predominant factor. The most important fines characteristics were the charge properties and the microstructure.     

Chitosan‐Based Glucose Oxidase Electrodes Enhanced by Silver Nanoparticles

Silver nanoparticles enhanced glucose oxidase electrodes were prepared on the basis of chitosan matrix. The enzyme electrodes exhibited high sensitivity and excellent response performance to glucose with a linear range from 1×10^?6 to 8×10^?3 mol · L^?1. And the time reaching the steady‐state amperometric response was less than 5 seconds. The inhibition percentage of this enzyme electrode against copper ions concentration was linear ranging from 1.2×10^?6 to 5×10^?5 mol · L^?1. These properties of enzyme electrodes are probably due to the excellent electron transfer of silver nanoparticles and the orientation of glucose oxidase molecule.     

河口混合与泥沙输运

根据振荡边界层理论和波流分解方法,导出了河口往复水流的流速垂向分布廓线,据此建立了河口垂向准二维水流、盐度、泥沙运动模型。对泥沙输运,完整地考虑了其对流、扩散、起动和沉降的动力学过程。模拟结果与实测资料进行了对比。应用该模型研究河口泥沙输运,分析了河口混合对泥沙输运的影响及最大浑浊带的时空变化规律。     

Adsorption Properties of Metal Ions Using Alumina Nano-Particles in Aqueous and Alcoholic Solutions

Different metal ions in aqueous and alcoholic solutions were adsorbed on alumina nano-particles prepared by the sol-gel method. The flocculation of the alumina sol was induced by the addition of different metal ions in solution. The flocculation kinetics was obtained by monitoring the particle growth with time using dynamic light scattering. These experiments were carried out following two different methods: a) the multiple injection method which consist in adding small amounts of metal ions until the critical flocculation concentration was reached and b) single injection method where an amount of metal ions equal to the critical flocculation concentration is added all in one shot. The efficiency of metal adsorption was determined by Atomic Absorption Spectroscopy.     

The effect of the exchangeable metallic cation on the colloid properties of laponite treated with acridine orangea spectrophotometric study

The adsorption of the cationic dye acridine orange (AO) by different monoionic laponites leads to changes in the colloid properties of this synthetic mineral in aqueous solutions. The organic cation is adsorbed by the mechanism of cation exchange. Small amounts of adsorbed dye keep the clay in a peptized state with all metallic cations. Greater amounts of AO result in the neutralization of the electric charge of the clay, and its flocculation. In excess AO the charge of the clay platelets becomes positive and the clay is peptized. The colloid properties are studied by absorbance curves in which the absorbance is described as a function of the degree of saturation with constant clay concentrations or with constant dye concentrations. In the absorbance curves three regions can be identified. The transition between the first and second or the second and third regions depend on the exchangeable metallic cation initially present in the clay. The spectrophotometric method is useful in identifying the presence of tactoids and flocculation mechanism, whether it results in card-house or in book-house flocs.     

An optical surface plasmon resonance biosensor for determination of tetanus toxin

Surface plasmon resonance (SPR) has been successfully applied for the simple, rapid, and label-free assay of various biomolecules. This assay evaluates a novel wavelength modulation SPR biosensor for the detection of tetanus toxin. The wavelength modulation SPR biosensor is designed based on fixing the incident angle of light and measuring the reflected intensities in the resonance wavelength range spanning 400-800 nm simultaneously. Tetanus toxin (TeNT), one of the most potent toxins known, is synthesized as a 150 kDa single polypeptide chain. The SPR biosensor has been shown to be capable of directly detecting concentration of tetanus toxin as low as 0.028 Lf ml⁻¹. Under selected experimental conditions, the SPR biosensor has a good reproducibility, sensitivity and reversibility. The results illustrate how wavelength modulation SPR biosensor can be used to detect biomolecular interactions.