Complex Investigations of Double Layer of Colloid Particles. Electric Conductivity of Suspensions and Anisotropy of Electrophoresis

Conditions for obtaining quantitative .ililformation on the double layer of colloid particles on the basis of electrosurface measurements have been analyzed. A rigorous theory of electric conductivdty of diluted suspensions on the basis of induced dilpole moments of particles has been presented. The .isoconductance point of a suspension has been shown to codncide wd.th the isopolarisation state of a particle. A theory of anisotropy of the electrophoresis of long rod-like particles has been put forward. The identity of the formules of electrophoresis of a sphere and of cylindrical particles oriented pevpendicular towards the field at a small thickness of the double layer has been shown. A good agreement has been found between the values of induced dipole moments and, specific surface conductivity in a wide electrolite concentration range measured by the methods of electric conductivity of suspensions and anisotropy of electrophoresis. The theories of induced dipole moment, electric conductivity of suspension and anisotropy of electrophoresis have been experimentally examined

Complex Investigations of Double Layer of Colloid Particles. Electric Conductivity of Suspensions and Anisotropy of Electrophoresis

Conditions for obtaining quantitative .ililformation on the double layer of colloid particles on the basis of electrosurface measurements have been analyzed. A rigorous theory of electric conductivdty of diluted suspensions on the basis of induced dilpole moments of particles has been presented. The .isoconductance point of a suspension has been shown to codncide wd.th the isopolarisation state of a particle. A theory of anisotropy of the electrophoresis of long rod-like particles has been put forward. The identity of the formules of electrophoresis of a sphere and of cylindrical particles oriented pevpendicular towards the field at a small thickness of the double layer has been shown. A good agreement has been found between the values of induced dipole moments and, specific surface conductivity in a wide electrolite concentration range measured by the methods of electric conductivity of suspensions and anisotropy of electrophoresis. The theories of induced dipole moment, electric conductivity of suspension and anisotropy of electrophoresis have been experimentally examined

Non-Equilibrium Surface Forces

A theory of the non-equilibrium double layer and of non- equilibrium surface forces is presented. Departures from the equilibrium state in the double layer are observed whenever there . is flow in this structure. In the theory only external field influences are treated. Dipolophoresis and diffusiophoresis are defined, and conditions for a steady-state are described. Application of the theory in interpreting phenomena of electrocoagulation, electrofiltration, bubble flotation, and electrodeposition of polymers is briefly discussed

Non-equilibrium Surface Forces and Hydrodynamics of Thin Films

The notion of »non-equilibrium surface forces« is advanced for the application in a number of cases of colloid stability and transport phenomena. The idealized concept of full equilibrium in the double layer, as used in the DLVO theory is shown to be too simple to describe the stability of a colloid particle not in equilibrium with the surrounding medium. Cases are described where surface forces are stipulated by adsorption layer effects, controlled by diffusion, such as flotation, crystal growth, hydrodynamic transport, and in describing the stability of living cells in suspension

Ion size effects on the electrokinetics of salt-free concentrated suspensions in ac fields

We analyze the influence of finite ion size effects in the response of a salt-free concentrated suspension of spherical particles to an oscillating electric field. Salt-free suspensions are just composed of charged colloidal particles and the added counterions released by the particles to the solution, that counterbalance their surface charge. In the frequency domain, we study the dynamic electrophoretic mobility of the particles and the dielectric response of the suspension. We find that the Maxwell-Wagner-O'Konski process associated with the counterions condensation layer, is enhanced for moderate to high particle charges, yielding an increment of the mobility for such frequencies. We also find that the increment of the mobility grows with ion size and particle charge. All these facts show the importance of including ion size effects in any extension attempting to improve standard electrokinetic models.Comment: J. Colloid Interface Sci., in press, 13 pages, 9 figure

A Classical Density-Functional Theory for Describing Water Interfaces

We develop a classical density functional for water which combines the White Bear fundamental-measure theory (FMT) functional for the hard sphere fluid with attractive interactions based on the Statistical Associating Fluid Theory (SAFT-VR). This functional reproduces the properties of water at both long and short length scales over a wide range of temperatures, and is computationally efficient, comparable to the cost of FMT itself. We demonstrate our functional by applying it to systems composed of two hard rods, four hard rods arranged in a square and hard spheres in water

KIMERA: A Kinetic Montecarlo Code for Mineral Dissolution

KIMERA is a scientific tool for the study of mineral dissolution. It implements a reversible Kinetic Monte Carlo (KMC) method to study the time evolution of a dissolving system, obtaining the dissolution rate and information about the atomic scale dissolution mechanisms. KIMERA allows to define the dissolution process in multiple ways, using a wide diversity of event types to mimic the dissolution reactions, and define the mineral structure in great detail, including topographic defects, dislocations, and point defects. Therefore, KIMERA ensures to perform numerous studies with great versatility. In addition, it offers a good performance thanks to its parallelization and efficient algorithms within the KMC method. In this manuscript, we present the code features and show some examples of its capabilities. KIMERA is controllable via user commands, it is written in object-oriented C++, and it is distributed as open-source software.Spanish Ministry of Economy, Industry and Competitiveness (project Ref-201860I057) and the Spanish Ministry of Science, Innovation and Universities (project Ref RTI2018-098554-B-I00). P. Martin acknowledges support from the PhD scholarship Tecnalia Research & Innovation’s grant

Study of the efficiency of sweet potato growing in the Forest-Steppe of Ukraine by different methods of soil mulching

Sweet potato (Ipomoea batatas L.) is a new crop for soil and climatic conditions of Ukraine, the active implementation of which is hindered by the lack of recommendations on technological aspects of cultivation. One of the important technological measures for growing sweet potatoes is the use of soil mulching, which improves the water regime and regulates the thermal regime of the soil; prevention of weed growth and growth of sweet potato shoots to the soil. Thus, the aim of the research is to determine the efficiency of growing sweet potatoes in the Forest-Steppe of Ukraine by different methods of soil mulching. Field research was carried out on typical low-humus light loamy chernozem on loess loam. It was noted, that when growing sweet potatoes on ridges, the introduction of mulching the soil with black polyethylene film provides more active growth of the vegetative mass throughout the growing season (5.33 shoots/plant with a total length of 252.1 cm), while growing without ridges has a positive effect on plants growth due to the general absence of mulch (2.53 shoots/plant with a total length of 107.8 cm). The use of ridges and mulching the soil with black polyethylene film causes the yield of sweet potato tubers at 34.8 t/ha, while the mulching of the soil with straw, the yield was 18.3–21.9 t/ha, without mulching – 13.0–17, 1 t/ha. Mulching with black polyethylene film ensures the accumulation of vitamin C and starch in sweet potato tubers. When growing the culture on ridges by this method of mulching, the maximum level of vitamin C according to the experiment (4.78 mg/100 g) and starch (11.73 %) was noted. The introduction of mulching and ridge formation involves additional material and labor costs, but helps to reduce weed control and tuber digging costs. When growing sweet potatoes on ridges with mulching with black polyethylene film, the minimum additional labor costs for the formation of a unit of yield (1.95 man-minutes/kg of tubers) were noted, while without mulching and without ridges this figure was 6.76 man-minute/kgSweet potato (Ipomoea batatas L.) is a new crop for soil and climatic conditions of Ukraine, the active implementation of which is hindered by the lack of recommendations on technological aspects of cultivation. One of the important technological measures for growing sweet potatoes is the use of soil mulching, which improves the water regime and regulates the thermal regime of the soil; prevention of weed growth and growth of sweet potato shoots to the soil. Thus, the aim of the research is to determine the efficiency of growing sweet potatoes in the Forest-Steppe of Ukraine by different methods of soil mulching. Field research was carried out on typical low-humus light loamy chernozem on loess loam. It was noted, that when growing sweet potatoes on ridges, the introduction of mulching the soil with black polyethylene film provides more active growth of the vegetative mass throughout the growing season (5.33 shoots/plant with a total length of 252.1 cm), while growing without ridges has a positive effect on plants growth due to the general absence of mulch (2.53 shoots/plant with a total length of 107.8 cm). The use of ridges and mulching the soil with black polyethylene film causes the yield of sweet potato tubers at 34.8 t/ha, while the mulching of the soil with straw, the yield was 18.3–21.9 t/ha, without mulching – 13.0–17, 1 t/ha. Mulching with black polyethylene film ensures the accumulation of vitamin C and starch in sweet potato tubers. When growing the culture on ridges by this method of mulching, the maximum level of vitamin C according to the experiment (4.78 mg/100 g) and starch (11.73 %) was noted. The introduction of mulching and ridge formation involves additional material and labor costs, but helps to reduce weed control and tuber digging costs. When growing sweet potatoes on ridges with mulching with black polyethylene film, the minimum additional labor costs for the formation of a unit of yield (1.95 man-minutes/kg of tubers) were noted, while without mulching and without ridges this figure was 6.76 man-minute/k

Electrophoretic mobility of a charged colloidal particle: A computer simulation study

We study the mobility of a charged colloidal particle in a constant homogeneous electric field by means of computer simulations. The simulation method combines a lattice Boltzmann scheme for the fluid with standard Langevin dynamics for the colloidal particle, which is built up from a net of bonded particles forming the surface of the colloid. The coupling between the two subsystems is introduced via friction forces. In addition explicit counterions, also coupled to the fluid, are present. We observe a non-monotonous dependence of the electrophoretic mobility on the bare colloidal charge. At low surface charge density we observe a linear increase of the mobility with bare charge, whereas at higher charges, where more than half of the ions are co-moving with the colloid, the mobility decreases with increasing bare charge.Comment: 15 pages, 8 figure