Liquid purification or separation – Processes – Treatment by living organism
Patent
1998-05-26
2000-06-06
Reifsnyder, David A.
Liquid purification or separation
Processes
Treatment by living organism
210626, 210695, 210739, 210765, 2101951, 2101953, 210197, 2101981, 210202, 210218, 210222, 210223, C02F 300, C02F 334, B03C 100
Patent
active
060714077
DESCRIPTION:
BRIEF SUMMARY
This invention relates to magnetic separation.
Magnetic separation is a technique used to remove contaminants such as heavy metal ions from solution in, for example, water.
One example of the use of magnetic separation is to remove radioactive heavy metal contaminants from waste water generated in a nuclear plant. The technique involves adding an adsorbent material to the contaminated solution which attaches to the contaminants, for example by chemical or electrostatic adsorption. The adsorbent material has magnetic properties so that, after the adsorbent material has removed heavy metals and/or organic materials from solution, the loaded adsorbent can be removed magnetically. (However, other separation techniques such as microfiltration, high speed centrifuge, hydroclone or flotation could be used).
A complementary process to the above technique is the so-called biomagnetic separation process. The basis of previously proposed biomagnetic separation techniques is that low-level micro-organisms are grown and then introduced into the contaminated solution. The micro-organisms have the two important properties mentioned above: they interact with the contaminants in the solution (generally by precipitation or adsorption on the organism surface) and they have magnetic properties so that they can subsequently be separated from the solution using a magnetic technique such as high gradient magnetic separation (HGMS). When the micro-organisms are separated from the solution in this way, they carry with them the precipitated contaminants, and so the contaminants are removed from the solution.
This process is described in various publications such as the article "Biomagnetic Separation And Extraction Process For Heavy Metals From Solution", Watson & Ellwood, Minerals Engineering, Vol. 7, No. 8, pp1017-1028 (1994), and "A Biomagnetic Separation Process For The Removal Of Heavy Ions From Solution", Watson & Ellwood, Proceedings of the International Conference on Control of Environmental Problems from Metal Mines, 1988.
FIG. 1 is a schematic diagram of such a previously proposed biomagnetic separation apparatus, comprising a chemostat 10 in which the micro-organisms (in this example, the so-called "Desulfovibrio" micro-organism) are grown.
The Desulfovibrio micro-organisms are then supplied to a reaction vessel 20 in which they are mixed (using a stirrer 30) with contaminated effluent and solutions of sulphates (SO.sub.4) and lactates. In the reaction vessel 20 the heavy metal contaminants in the effluent precipitate onto the surface of the Desulfovibrio micro-organisms.
The mixture is then passed to a high gradient magnetic separator 40 which (as described in the published references listed above) comprises a matrix of fine ferromagnetic wire which is magnetised by an externally-applied magnetic field (not shown). The paramagnetic Desulfovibrio bacteria (with precipitated contaminants) are attracted and held onto the wires by magnetic forces. The decontaminated effluent then emerges through an outlet 50.
From time to time, the material accumulated on the matrix can be removed by switching off the applied magnetic field and washing the particles from the matrix. Alternatively, the matrix can simply be withdrawn from the magnetic field for washing. Thus, HGMS is a cyclical process with a collection phase and a washing phase.
In the schematic diagram of FIG. 1, the Desulfovibrio bacteria with the heavy metal contaminants emerge through a separate washing outlet 60 during the washing of the matrix.
A problem with these previous magnetic separation processes is the difficulty in identifying suitable micro-organisms (from a large number of available micro-organisms) or other materials to interact with the contaminants in the particular effluent to be treated and produce a strongly magnetic precipitate.
This invention provides apparatus for generating an adsorbent product for use in magnetic separation of contaminants from an influent liquid, the apparatus comprising: micro-organisms with the contaminated influent liquid; sep
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patent: 5228995 (1993-07-01), Stover
patent: 5328594 (1994-07-01), Hettinger
Ellwood Derek Clifford
Watson James Henry Peter
Reifsnyder David A.
University of Southampton
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