Liquid purification or separation – Processes – Making an insoluble substance or accreting suspended...
Patent
1993-08-25
1996-07-30
Hruskoci, Peter A.
Liquid purification or separation
Processes
Making an insoluble substance or accreting suspended...
210746, 210 961, 210101, 324 711, 324453, C02F 156
Patent
active
055408451
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention is concerned with a method of measuring the anionic charge content of an aqueous stream of an anionic dispersion, including identifying the incursion of an anionic dispersion into a less anionic aqueous stream.
1Field of the Invention
Anionic dispersions are commonplace: most natural dispersions--raw water sewage, sludges and effluents--and some man-made dispersions are anionic. Some are required whilst others are a nuisance or dangerous and need to be avoided or treated to remove the danger.
Many industries produce an aqueous stream which is ideally devoid of, or has at most a limited tolerance for, colloidally dispersed anionic solids or liquids. For example the product stream from a water treatment works, the effluent from an industrial or communal waste water works or the outfalls from farms, admitted to watercourses such as public waterways. Such a stream may be adventitiously polluted with colloidal suspended matter to the detriment of the quality of the stream.
Incidents have occurred where sludge has escaped from a sewage farm, or silage liquor or animal slurry from a farm, killing fish and leading people to doubt the quality of the water they use for recreation.
There is, therefore, a need for an instrument giving timely warning of such an incursion of a disperse phase of negatively charged particles into an aqueous stream.
2. Background of the Invention
The analysis of dispersions has hitherto been the province of electrokinetics which requires that the particles move relatively to the continuous phase. Either that movement is brought about by imposing an electric gradient on the dispersion via electrodes having an impressed potential difference, causing the dispersed particles to migrate towards the electrode of opposite potential (electrophoresis): or the particles are slowed relative to the fast flowing dispersion and the current generated by The mobile counter-ions swept from the surfaces of the dispersed phase, is collected on two electrodes as a potential difference or current (streaming potential or streaming current).
Electrophoresis is not applicable to opaque dispersions and Is probably only applied to stationary or slowly moving streams. Streaming potential or streaming current is not applicable to any stream with a substantial disperse phase-capillaries are essential elements of the apparatus and the dispersion must be able to pass through them. Hence electrokinetics is not suitable to analyse most everyday dispersions.
In the specification of WO91/04486 a device is described for sensing the course of the aggregation of an aqueous dispersion of charged particles in an aggregation control loop process. The device has a galvanic cell having a metallic indicator electrode without any particular ion-specificity and a second electrode, the electrolyte of the cell being a mixed stream of the dispersion and an aggregant for the charged particles and being in contact with the indicator electrode, and a means for sensing the potential difference appearing between the electrodes. This is an effective feed-back control device which can be used in an aggregation control loop, for example, to control the addition of aggregant.
We have now discovered feed-forward (or feed-downstream) applications in which aggregant addition is not necessary upstream of the sensing-point so that it is not a mixed stream of aggregant and aqueous dispersion which is being charge-sensed. This invention allows the potential difference created in a galvanic cell where an aqueous stream of negatively charged particles is the electrolyte, to be used for pollution control.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, a method of indicating changes in the anionic charge per unit time borne by the dispersed phase of a stream of an aqueous dispersion of negatively charged particles, comprises flowing the dispersion in contact with a first metallic indicator electrode, allowing the first indicator electrode to develop an electrical potential determined by the anio
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patent: 5202016 (1993-04-01), Church et al.
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Blanchard Michael J.
Collins Brian
Basil William Brook
Hruskoci Peter A.
Striker Michael J.
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