Stabilization of Aqueous Dispersions of Inorganic Microparticles Under Mechanical Activation

The stability of aqueous dispersed systems of TiO2 and Fe2O3 microparticles in the presence of a water-soluble polymer - ethylhydroxyethylcellulose (EHEC) - has been studied under the condition of using two methods of mechanoactivation of the pigment surface - processing them in a disintegrator and in an ultrasonic field. It is shown that in the absence of a polymer stabilizer, an intense effect on aqueous dispersed systems of pigments leads to rapid coagulation of particles. In the presence of EHEC, a small stabilizing effect is observed, which is significantly enhanced when processing dispersed systems in a disintegrator and in an ultrasonic field. In this case, the stability of dispersed systems depends little on the method of mechanoactivation of their surface, but significantly depends on the duration of the intense exposure.

The Limits of Fine Particle Ultrasonic Coagulation

This paper describes the studies conducted in order to identify the limits of ultrasonic exposure’s effect on the fine particle coagulation process. It has been established as a result of the studies that ultrasonic exposure with a sound pressure level of 160 dB is capable of ensuring coagulation of particles sized 2.5 µm with efficiency δ = 83%. An increase of the coagulation up to 13% is induced with generation of swirling flows. The suggested approach to increasing the coagulation efficiency owing to vortex-type flows between the radiating and reflecting surfaces ensures efficiency of coagulation δ = 96 %. The implementation of this approach has shown that with generation of vortex-type acoustic flows, it makes the most sense for a concentration of particles of 18×10−3 g/m3. Incremental efficiency at such concentrations amounts to 50%.

Влияние осаждения и коагуляции частиц на параметры текущих в трубе наноаэрозолей

The influence of the processes of deposition and coagulation of particles, caused by Brownian diffusion, on the parameters of aerosols flowing in the tube is studied. The problem is considered in a two-dimensional formulation taking into account the inhomogeneous velocity profile of the medium across the tube. At different Knudsen numbers, the distributions of the concentration and radius of clusters (formed due to particle coagulation) along the longitudinal and transverse directions were obtained by the numerical finite difference method. It was found that moving along the channel, the clusters reach the final (limiting) size. The influence of the governing parameters on the distribution of dispersed characteristics of the mixture inside the tube and on the limiting size of clusters is discussed.

EXPERIMENTAL STUDY OF COAGULATION OF PARTICLES IN A MAGNETIC SEDIMENTATION

In agriculture, a large number of different lubricating and cooling liquids are used in the operation, maintenance and repair of agricultural machinery. In the process of use, technical fluids become contaminated with foreign impurities and require periodic cleaning. Magnetic sedimentation tanks are well suited for this. The studies were carried out in order to determine the parameters (the magnitude and gradient of the magnetic field strength, the height of the apparatus, the concentration of particles), at which coagulation of particles is observed in a non-uniform magnetic settler. The experiments were carried out on a laboratory setup for studying coagulation in the working area of a magnetic sump. For a given magnetic system, the geometric dimensions of the apparatus were determined in such a way that the magnetic field acts in the entire working volume of the sump and effectively traps foreign metal impurities. The value of the magnetic induction of the field B is proportional to the square of the distance from the investigated point to the pole of the electromagnet Н0. At a distance of 300 mm and further, the magnetic force has almost no effect on the particle, so the height of the sump should be less. The lowest magnetic induction is observed in the middle of the coil. A decrease in the current in the winding entails a reduction in the length of the floccule; magnetic coagulation takes place when the concentration of particles in the coolant is more than 0.3 g/l, with a lower content, it is not observed due to significant distances between the particles; the effect of coagulation is noted in the entire area of action of the magnetic field, while the length of the floccules decreases with a decrease in concentration. The distance at which the effect of coagulation between particles is observed is determined by a complex function that depends on the current in the winding, the field strength, their distance from the pole of the electromagnet, and also on the size of the particles.

MODERNIZATION OF DEVICES FOR PURIFICATION OF AIR FROM SOLID HIGH-DISPERSED AEROSOLS

A device for cleaning solid particles with a dispersion of 0.1 μm is proposed. The principle of the apparatus is based on coagulation of particles on slots perforated in the form of slots, using irrigation of contaminated air with water through nozzles with a dispersed composition from 2.0 microns to 10 microns. When a threephase fl ow passes through the slots of the fi rst separator plate, turbulent coagulation occurs due to turbulence of the fl ow in streams with a small turbulence scale, which leads to particle coarsening. When the jet runs onto the second plate, a boundary layer is formed that has an increased viscosity to the components of the jet. Viscosity is formed due to the sedimentation and mixing of water particles and dust (including coarsened) on the surface of the second plate, where particles are mainly deposited. The dependences of the apparatus effi ciency on the width of the slots and their mutual arrangement on the fi rst and second plates, the combination of which provides a mode of increased coagulation and high effi - ciency of particle capture by the apparatus, are revealed.

ON THE ROLE OF SURFACE INTERACTIONS OF PARTICLES OF FIBER STRUCTURE DURING AGGLOMERATION IN THE AIR FLOW

The mechanism of surface interactions of polydisperse particles during agglomeration is considered. The characteristic of fibrous materials is given on the example of shredded waste paper and cardboard. An equation is obtained for calculating the soaring speed of the particles of the fibrous structure depending on their relative sizes and density. The mechanisms of coagulation of particles in moving air streams are considered. The prevailing role of coagulation due to the acceleration mechanism for fibrous materials is shown. The results of the calculation of the dynamics of particle enlargement of technogenic fibrous materials depending on their initial size are presented. The expediency of organizing the process of agglomeration of particles in the toroidal chambers of a pneumomechanical apparatus under the action of centrifugal forces is shown.

Observation of rapid aerosol deposition according to AERONET data

Measurements at the AERONET station in Dushanbe showed that the diurnal variations of the aerosol optical thickness (AOT), humidity, Ångström parameter depend on the stratification of the atmosphere. It is established that the dynamics of the aerosol in the ground inversion temperature layer is determined by the effect of double diffusion, which is manifested as a result of the difference in the diffusion coefficients of the components. As the temperature and aerosol concentration increase from the bottom to the top, vertical convection cells of the "salt finger" type are formed, which cause a rapid settling of dust by means of condensation of water vapor and coagulation of particles and water droplets.

Robust open cellular porous polymer monoliths made from cured colloidal gels of latex particles

Preparation of polymer monoliths from the coagulation of particles, synthesized by soap-free emulsion polymerisation, using water as the only solvent.