Removal of mercury from waste streams
AssigneeEltech Systems Corporation
InventorOscar A. Pitton
Life of this patent
Estimating the term…
Abstract
A waste stream contaminated with mercury is purified by flowing the stream cyclically and/or sequentially through at least one electrolytic cell provided with an anode (11) and a cathode (10) made of tin, copper, silver or alloys thereof and optionally comprising other alloying element(s). The cathode (10) is a microporous, high surface area body through which the electrolyte can pass, with the solution sweeping the microporous surfaces. After cycling through one cell or cell module (1) with cathodes of given microporosity, the solution is passed to the next cell or cell module with cathodes of finer miocroporosity. The microporous surfaces are periodically cleaned by counter-current flushing, preferably followed by a rest period. The waste stream may be an acidic waste stream containing organic mercury compounds.
Claims33
A method of purifying a waste stream solution contaminated with mercury by flowing the stream through at least one electrolytic cell provided with an anode and a cathode having a surface made of tin, copper, silver or alloys thereof including alloys with gold, zinc, iron, gallium, aluminum and sodium as alloying element(s), which method comprises:
- (a) introducing the solution into at least one cell having a cylindrical microporous, high surface area cathode body of sintered metal or foam metal through which a solution can pass;
- (b) passing the solution through the body of the cylindrical microporous cathode of said cell;
- (c) sweeping the cathode body microporous surfaces with solution to reduce or prevent unwanted deposits;
- (d) passing solution through unseparated anolyte and catholyte compartments of said cell so that the anolyte from one cell passes into the catholyte compartment of the same cell or of another cell;
- and
- (e) removing deposits from the microporous surfaces of the cathode body by flowing a cleaning fluid through the microporous body counter-current to the flow of said solution.
A method of purifying a waste solution contaminated with a heavy metal such as mercury which amalgamates with tin, copper or silver by cathodic filtration, said method comprising:
- (a) passing the waste solution through the body of at least one cathodically polarised, cylindrical and microporous, high surface area cathode of sintered metal or foam metal through which the solution can pass, including sweeping solution on the microporous surfaces of said cathode body;
- (b) polarising the cathode body at a voltage sufficient to cathodically protect the body from any substantial dissolution in the waste solution and to deposit the heavy metal on the microporous surface as an amalgam with the metal(s) of the cathode body alone or with the heavy metal adsorbed on the cathode surface;
- (c) removing unwanted deposits from the microporous surfaces of the cathode body by flowing a cleaning fluid through the microporous body counter-current to the flow of said solution;
- and
- (d) allowing the cathode body to remain for a rest period without polarisation, in or out of contact with the cleaning fluid, before passing the waste solution again according to steps (a) and (b) with the body polarised.
An installation for purifying a waste stream solution contaminated with mercury, said installation comprising:
- at least one electrolytic cell provided with an anode and a cathode in an unseparated cell, said cathode having a surface made of tin, copper, silver or alloys thereof, including alloys with gold, zinc, iron, gallium, aluminum and sodium;
- at least one cathode in said cell having a hollow, cylindrical microporous, high surface area cathode body of sintered metal or foam metal, through which microporous cylindrical body the solution as electrolyte can pass,
- means for passing the solution through at least one cell with the solution passing through said cell;
- means for supplying an electrolysis current to polarize said cathode body at a voltage sufficient to cathodically protect the cathode body from any substantial dissolution in the waste stream solution and to deposit mercury on the cathode body as an amalgam with the metal(s) of the cathode body alone or with metallic mercury adsorbed on the cathode surface;
- and
- means for removing unwanted deposits from the microporous surfaces of the cathode body by flowing a cleaning fluid through the microporous body countercurrent to flow of the solution during normal operation, the cathode body being removable and replaceable.
Dependencies are inferred from the claim text.