Metallurgical apparatus – Having means for leaching and subsequently precipitating a...
Reexamination Certificate
1999-09-28
2001-03-13
Kastler, Scott (Department: 1742)
Metallurgical apparatus
Having means for leaching and subsequently precipitating a...
C266S170000
Reexamination Certificate
active
06200521
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to apparatus for silver waste recovery, and more specifically, to a gravity-flow apparatus for use in the recovery of silver from photo processor waste streams.
A number of devices employing containers for recovering silver from photo processor waste streams such as spent fixing solutions from photographic paper and film processes are known in the industry. These devices generally pass the solution containing silver salts through a metal filter. The metal utilized in the metal filter is selected due to its electromotive force series characteristic being higher than that of silver. As the silver salts pass through the metal filter, a chemical replacement action causes the silver to be deposited on the metal filter. When the supply of metal on the metal filter for exchange is exhausted, the contents of the container, especially the used metal filter, are processed at a refinery to recover the silver left therefrom.
In order to safeguard the environment, it is important to be able to control the release of silver-containing solutions into the environment. Known sources of silver containing solutions have traditionally been treated to remove the silver salts from these solutions prior to disposing of the remaining solution into the environment. Attempts have been made, in the prior art, to fashion silver recovery systems that remove a large quantity of silver from the solution prior to the disposal of the solution. Some of these prior art methods unfortunately leave a relatively large silver component in the solution after the solution passes through the silver recovery systems. Currently the EPA has a requirement that waste water have no greater than five parts per million silver content. Additionally, it is also possible that city and state clean water requirements may be more strict. Accordingly, many users of silver containing solutions are in need of an effective silver recovery system.
U.S. Pat. No. 5,837,188 issued to Peterson on Nov. 17, 1998, discloses a metal filter utilized in conjunction with a non-metallic mesh material positioned about and to closely adjacent to an exterior surface of the filler filter material. This patent discusses at least some of the known prior art silver recovery systems. Some of these prior art silver recovery systems utilize steel wool as a metal filter. Others utilize large openings in screen wire permitting solution to bypass the filter material and exit the vessel with silver remaining in the solution. Others utilize solution flow from the bottom of a tube upward through metal shavings and a bed of neutralizing material. While still others utilize a mesh bag to contain the silver material when the core is moved from the interior bag. Finally, others utilize fluid deflectors and baffles to increase the length of fluid flow through the filter.
These prior art silver recovery systems suffer from a number of perceived problems. First, the affluent of the silver recovery systems exits the units after passing last through the metal filter. Accordingly, if any silver particulate breaks off on the metal filter, the silver will likely end up passing out of the unit as effluent. Secondly, if the capacity of the metal filter or filler material is close to the end of its useful life, the user may have trouble visually inspecting to see the amount of useful life left by the unit.
Although some prior art systems have employed a mesh bag around a silver recovery filter, a need exists to provide a more suitable catch for particulate matter in the solution. In the prior art, external portions of the mesh bag may become fouled with particulate and perhaps pass to the outlet and into the environment.
If the filter material of these prior art systems is depleted, then the silver-containing effluent will pass directly to the outlet. As such, the silver-containing effluent may flow outwardly of the system without reacting with the filter material.
SUMMARY OF THE INVENTION
Consequently, it is an object of the present invention to provide a silver recovery system which provides a plating surface for the silver.
It is another object of the present invention to provide a silver recovery system which allows silver to plate on filter material so that the actual silver may serve as a filtering element and a silver recovery component of the system.
It is a further object of the present invention to provide a silver recovery system so as to provide a system which allows for the use of two separate types of filter mechanisms.
It is yet a further object of the present invention to provide a silver recovery system that enhances the purity of the silver which is recovered from the system.
It is still a further object of the present invention to efficiently filter organic chemicals and heavy metals from the effluent of the unit system.
It is still yet a further object of the present invention is to utilize a non-reactive filter closest to the outlet to significantly reduce the opportunity for particulate to exit with the effluent.
It is yet still another object of the present invention to provide a silver recovery system which is relatively inexpensive, easy to use, and easy to manufacture. These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.
Accordingly the present invention provides a silver recovery system comprising a container having an inlet and an outlet, a filter having filler material, preferably in the form of silver cell, within the container communicates with the inlet, the silver cell being a metal above silver in the electromotive force series. Enfluent solution passes through the filler material in the silver cell, and thereafter through a second filter, and then to the outlet. Thus, any solution passing through the inlet of the unit must first pass through the silver cell prior to passing through to the outlet as effluent. The second filter is preferably a fabric filter or other non-silver exchanging filter such as a fabric filter. Although the preferred flow path is from the inlet through the silver cell through the fabric filter to the outlet, an overflow spout may be located in the unit to allow for bypassing the second filter to allow overflow to exit the unit.
REFERENCES:
patent: 6042775 (2000-03-01), Steiner et al.
Kastler Scott
Miller & Martin
Ruderman Alan
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