Chemistry: electrical and wave energy – Processes and products – Electrostatic field or electrical discharge
Patent
1986-06-11
1988-03-01
Tufariello, T. M.
Chemistry: electrical and wave energy
Processes and products
Electrostatic field or electrical discharge
C02F 146
Patent
active
047284048
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for decomposing oil-in-water emulsions in an electrolysis cell powered by directed current and an apparatus for carrying out the method.
Due to the increased use of synthetic products based on mineral oils, which are biologically only poorly decomposable, ground and surface water is increasingly loaded with matter, such as, e.g. petroleum, diesel fuels, heating and lubricating and surface-active substances.
In consideration of the increasing environmental load, the authorities have made the discharge of these dangerous substances above certain concentrations into waters a punishable offence.
Macro-emulsions are polyphase systems with great contact surfaces and contact surface tension which does not disappear on which their instability is based. This means that these emulsions tend to reach the lowest possible energy stage, towards sedimentation or flotation and thereby finally to coalescence.
Micro-emulsions are, however, isotropic, thermodynamic stable systems, whose dispersed phase appears in the form of particles smaller than 2000 Angstrom units. They develop spontaneously by the interaction of the corresponding molar ratios of peptizing mediums, tenside, oil, and water.
The stability of emulsions is increased by the addition of emulsifying surface-active compounds. This involves bipolar substances that reduce the surface tension between the phases.
The overall stability of an emulsion is determined by the sum of the van der Waal attraction forces and the repulsion of the primarily negatively charged particles due to coulomb forces.
Coagulation and flocculation can result from the removal of the charge of the particles, i.e. the zeta potential of the emulsified particles. Should a particle move, for example as a result of an imposed electrical field, one part of the diffuse double layer is stripped off and if the energy barrier between the particles is small enough, a flocculation process can be caused only by the particles moving closer together.
To comply with the norms suggested by law, the breaking of oil/water emulsions, to avoid pollution of the environment is necessary in all circumstances. Some technical solutions are known to achieve this, namely mainly: ultrafiltration, the mixing in of de-emulsifiers, ultrasonic sound, chemical dosing, dialysis, electrocoagulation.
These processes are, however, partially associated with high investments and high operating costs and are particularly uneconomical for small quantities of highly polluted waste water. An important object of this invention was therefore to make a versatile, cost-favourable process available.
Other technical separation processes for the recovery of products concern the preparation, for example, of ores, coal, salts and dewatering, and here one of the best known processes is flotation based on the observations of W. Haynes (British Patent No. 488 of 1860). This flotation is applied in many branches of industry also in the form of electroflotation, for example in the separation of silver from used photobaths.
With this flotation gas bubbles are produced in watery solutions from the water by the aid of electrolysed hydrogen and oxygen, that is in the medium itself which is subject to the separation. In addition, the separation yield can be considerably increased by the simultaneous coagulation of the solids in the watery solution.
It is apparent that in the field of the decomposition of emulsions of the abovenamed kind, it would be a marked advance if one could apply electroflotation and electrocoagulation together with electrophoretic effects to these systems and decompose these emulsions in a progressive manner with justification of the energy involved. At the same time, it would also be possible to use this form of emulsion decomposition in the separation of organisms from nutrient solutions and to add by means of the simultaneous metal decomposition, the necessary cations to the solution to do away with present processes, namely centrifuging or flotation by the blowing in of air and the following
REFERENCES:
patent: 4121993 (1978-10-01), Krugmann
Schellin Eric P.
Tufariello T. M.
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