Abstract:
A silver waste recovery system including a container having an inlet and an outlet at a lower elevation than the inlet, filler material in a silver cell is in communication with the inlet and a separate non-silver reactive filter is in communication with the outlet. A catch basin is positioned about the silver cell and the non-silver reactive filter contains particulates in the area of the filter and the filler material. Fluid entering the inlet passes through the silver cell and exits into the catch basin. It thereafter enters the non-silver reactive filter and exits from it through the outlet.

Description:
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. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The particular features and advantages of the invention as well as other objects will become apparent from the following description taken in connection with the accompanying drawings in which: 
     FIG. 1 is a vertical diagrammatic cross-sectional view of apparatus of a silver recovery system constructed in accordance with the present invention; 
     FIG. 2 is a top view of the apparatus of FIG. 1 shown with the lid removed; 
     FIG. 3 is a side elevational view of the lid of an alternative embodiment; and 
     FIG. 4 is a top elevational view of the lid illustrated in FIG.  3 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, FIGS. 1 and 2 illustrate apparatus forming a silver recovery system  10  according to the present invention, the silver recovery system comprising a container  12 , preferably equipped with a lid  14 , a filter having filler material shown as silver cell  16 , a fabric filter  18  and a catch basin  20 . 
     The container  12  has an inlet  22  and an outlet  24 . In the preferred embodiment, the container  12  is a bucket with a base  26  and has the inlet  22  extending through a portion of the lid  14 . The outlet  24  extends through a wall  28  of the container  12 , the outlet  24  being connected by a connector  30  in the form of a conduit into the filter  18 . Where the outlet  24  joins the connector  30  at the wall  28 , a seal  32  may be desirable. 
     As can be seen in FIG. 1, the inlet  22  is located at a higher level than the outlet  24  so that the apparatus may operate as a gravity flow apparatus. The container  12  may be of any standard design, preferably cylindrical, and should be made of a non-reactive, non-corrosive material. The outlet  24  may be equipped with a metallic coupling capable of indicating when silver collection is complete for a particular silver cell  16 . 
     Within the container  12  is housed a catch basin  20 . The catch basin  20  is illustrating having sides  34 ,  36  and bottom  38 , but preferably is also cylindrical. In the preferred embodiment, the catch basin  20  has a bottom portion  38  which rests atop the base  26  of the container  20 . It is preferred that sufficient room exists between the external periphery of the catch basin  20  and the interior periphery of the walls of the container  12  such that the catch basin  20  may be removed in order to recover silver from the silver cell  16  and/or the catch basin  20  and/or the filter  18 . 
     The operation of the silver recovery system  10  is straightforward. Enfluent such as the produce of spent photographic fixer solutions or other silver salt containing solutions enters through the inlet  22 . The enfluent thereafter enters the silver cell  16  and then passes from the interior of the silver cell  16  outwardly and into an internal portion of the container  12 . The silver cell  16  is preferably a metallic replacement silver cell as is known in the art containing a filter material including a metal above silver in the electromotive force series. 
     In the preferred embodiment, the silver cell  16  surrounds a core  40  which has one or more openings so as to allow enfluent to pass from the inlet  22  to the interior portion of the container  12  through the silver cell  16 . The core  40  may, if desired, be disconnectibly connected to a tubular conduit  42  by a coupler  44 . The conduit  42  is illustrated passing through the lid  14  to connect and communicate with the inlet  22 . A second seal  56  may be utilized where the passage  42  extends through lid  14 . 
     By having the effluent pass from the internal portion of the silver cell  16  to the external portion, silver should preferentially plate from the internal portion of the silver cell  16  outward. This process will result in more silver being contained within the silver cell  16 . This, it is believed, assists in reducing the amount of silver debris which may collect in the bottom of the catch basin  20 . As fluid passes from the interior to the exterior of the silver cell  16  and then to the catch basin  20 , the fluid may enter filter  18 . Filter  18  is preferably a fabric filter and preferably comprises a  40  micron fabric filter. Within the filter  18  may be located a charcoal core  66 . The charcoal core may take the form of activated charcoal granules or an activated charcoal core portion which may further treat solution prior to the solution exit being as effluent. 
     The non-silver exchanging filter type has been found effective at filtering organic chemicals and assisting in filtering silver and other heavy metals and debris which have been filtered from the enfluent solution. Other non-silver exchanging filters may be used in lieu of the filter  18  or in addition to the filter  18  without departing from the invention. 
     The fluid exiting the filter  18  passes into connector  30  preferably at first leg  46 . From the first leg  46  fluid may enter pipe joint  50  and proceed into second leg  48  through the wall  28  of the container  12  and through the outlet  24  of the silver recovery system. An overflow spout  52  connected to the joint  50  has been found effective in preventing spills from apparatus. The overflow spout  52  is an added safety feature of this silver recovery system  10  if used. The connector  30  is preferably made of a non-corrosive, non-reactive material such as PVC piping. Additionally, the core  40 , coupler  44  and passageway  42  are preferably made of a non-corrosive, non-reactive material such as PVC piping. Other material may be substituted and/or utilized. 
     The filter  18  is illustrated resting atop the catch basin  20  on a foot  54  which has been found effective in providing support for the filter  18 . Other and/or additional supports may also be utilized to assist in supporting the filter  18 . Additionally, the connector  30  may assist in supporting the filter  18 . Although the silver cell  16  is illustrated slightly suspended above the catch basin  20 , it is also possible for the silver cell  16  to rest atop a support within the catch basin  20 . 
     FIG. 3 illustrates a side elevational view of the lid  114  of an alternative embodiment of the silver recovery system  10 . The lid  114  preferably has ledge  58  which, when installed, is where the lid  114  rests atop a top portion of the wall  28  of the container  12 . Threads  60  may be utilized to connect the lid  114  to the container  12 . Other connection mechanisms may also be utilized to connect the lid  114  to the container  12 . 
     FIG. 4 is a top view of the lid  114  and illustrates raised portions  62  and recessed portions  64  which may assist a user in connecting the lid  14  to a container  12 . 
     The preferred embodiment may utilize a standard metallic replacement silver recovery cartridge for silver cell  16 . Utilizing available equipment, such as a five-gallon bucket for the container  12 , the cost of producing the system  10  may be minimized. As aforesaid, PVC piping may be utilized for the connector  30 , the coupler  44 , the passage  42 , the core  40  and the overflow spout  52 . Additionally, the inlet  22  and the outlet  24  may be constructed of PVC material. It will be apparent to one skilled in the art that other materials may also be utilized for these as well as other components described herein. 
     Numerous alternations of the structure herein disclosed will suggest themselves to those skilled in the art. However, it is to be understood that the present disclosure relates to the preferred embodiment of the invention which is for purposes of illustration only and not to be construed as a limitation of the invention. All such modifications which do not depart from the spirit of the invention are intended to be included within the scope of the appended claims.