Effect of saline groundwater on the aggregation and settling of suspended particles in a turbid Australian river

Laboratory studies have modelled the interaction of Darling River water and a saline groundwater intrusion. Kinetic measurements have shown that the rate determining step in water column clarification is the aggregation of small colloidal particles which then settle rapidly after reaching a critical diameter. Divalent cations (Ca²⁺ and Mg²⁺) are extremely effective in enhancing the rate of clarification by increasing the colloid stability factor. Three different phases have been observed in the cation-mediated removal of iron from solution: (i) rapid coagulation induced by the initial velocity shear resulting from solution mixing; (ii) a slower second-order iron removal, consistent with conventional aggregation kinetics; and (iii) a decrease in rate after 90% iron removal which is attributed to a lower iron content in the ultrafine colloid fraction. Specific interactions between the divalent cations and the organic coatings on the particles are proposed in order to explain the much higher rate of coagulation than expected on electrostatic grounds when compared with the monovalent Na⁺ and K⁺.

Water column clarification occurred more rapidly in these model laboratory studies than was observed in the Darling River weir pool. Iron removal rates in the river tend to be inhibited by hydrological effects. Turbulence inducing processes are required to mix the dense saline groundwater with the overlying water column and thus may ultimately limit the rate of turbidity reduction.     

Simulation of suspension gravity currents with different initial aspect ratio and layout of turbidity fence

A three-dimensional (3D) numerical model, using large eddy simulation (LES), is developed for simulating the motion of suspension gravity currents. The suitable values of model parameters are determined using the existing experimental data of a two-dimensional (2D) suspension (a mixture composed of water and glass bead particles) cloud. The simulated gravity current with different initial aspect ratio (length/breadth) of the suspension is compared with the reported data of 3D laboratory experiments to investigate the effect of initial aspect ratio on the flow characteristics and the diffusion of turbidity under the presence of a turbidity fence. The comparison of simulated results of such main flow characteristics as front height, front propagation velocity and particle deposition with the experimental data reveals that the model is capable of simulating the complex behavior of the 3D suspension gravity currents to a reasonably good accuracy under complex conditions.     

硫酸钡分光光度比浊法间接测定有机催化剂2－乙基蒽醌中的硫

本文研究了用浓硝酸将２－乙基蒽醌中的硫定量转化成硫酸根，然后用硫酸钡分光光度比浊法间接测定其硫含量的方法。建立的方法简单、快速、实用。试样分析结果表明准确度及精密度均符合要求。     

Impact of various stresses on the streaming electrification of transformer oil

In this contribution the influence of various stresses and their combined impact on the electrostatic charging tendency of oil is studied. Various physicochemical properties were measured according to ASTM Standards to detect changes in oil quality. A free radical reagent, 2.2 diphenyl-1-picrylhydrazyl (DPPH), was added to oil before and after the application of stresses to determine free radical concentration. The results obtained show that the application of stresses contributes to an increase in the electrification current. These results also demonstrate that electrification current is affected by the quantity of the free radicals.     

Spectroscopic Evaluation of Effects of Heat Treatments on the Structures and Emulsifying Properties of Caseins

The effects of heat treatment (heating temperature and pH) on the structures and emulsifying properties of caseins were systematically studied by spectroscopy. Heat treatment from 60 to 100 ℃ resulted in an increase in their fluorescence intensity, hydrodynamic diameter, turbidity and emulsifying activity index, but decreased the size polydispersity of caseins. In the pH range of 5.5 to 7.0, the fluorescence intensity, hydrodynamic diameter, turbidity and emulsifying properties decreased with increased heating pH, but the size polydispersity of caseins increased with increased pH. The relationship between the surface fluorescence intensity and emulsifying activity was also investigated, revealing a correlation coefficient of 0.90. These results suggested that heat treatment could be used to modify the structures and emulsifying properties of caseins by appropriately selecting heating conditions.     

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Rheo-optical characterization of dilute polymer mixtures under shear flow

Optical properties can estimate morphological changes of polymer chains under flow. This work proposes a rheo-optical procedure to determine turbidity and both flow and form birefringence of diluted polymer mixtures of polystyrene (PS) and polypropylene (PP) during a controlled shear flow, by measuring the transmitted light intensity with and without crossed polarizers via an own built optical sensor. The turbidity in these dilute mixtures decreased with the increase of the shear rate due to deformation of the dispersed phase droplets, which reduces their cross-sections. The presence of PP as the dispersed phase in the PS matrix caused a decrease in the total birefringence measured, whereas PS as the dispersed phase in the PP matrix caused an increase in it. Both effects are associated to the positive contribution of the form birefringence, produced by the shear-induced elongated morphology of the dispersed phase.     

Port wine spectronephelometry

The main purpose of this research was to create a portable equipment capable of measuring colour and turbidity during production of port wine. Actually, human, chemical and colour analysis are performed in key production stages for quality control. Several wine transformation processes are done without any kind of control. By using a fibre optic illuminator with a tungsten/halogen light source and a small spectrometer with fibre optic input, it was possible to perform angular measurements in wine samples. We have adapted these optical devices with a specially designed mechanical equipment which allows the passage of the wine during production. The spectral measurements were acquired in four different angular positions in a bypass of the mechanical support. This way we could determine colour coordinates and spectral transmittance and turbidity for three stages of a Ruby production. The entire equipment assembly had been previously calibrated in terms of colour and turbidity determination. The obtained results are in agreement with wine transformations between measurements, showing a small variation in colour and a high diminishing in spectral turbidity when filtration was performed. Transmittance has also increased after filtration turning the wine more limpid as it should be for human appreciation.     

A Turbidity Study of the Rate of Dissolution of Zinc-Monoglycerolate in Aqueous Solution

Abstract

The turbidity of suspensions of polymeric zinc monoglycerolate (ZMG) has been used to determine dissolution rates in aqueous solution. The rate was found to be first order with respect to the concentration of undissolved ZMG and of order 1/2 with respect to the hydrogen ion concentration in the pH range 4.1–5.8 and a temperature range of 20°C - 45°C. The temperature dependence at constant pH obeys the Arrhenius equation and the activation energy of the dissolution process was found to be near 35 k J mol^?1.