Method for metal concentration, method for metal recovery, device for metal concentration, and device for metal recovery

Abstract

An objective of invention is conveniently concentrating a metal in a metal ion-containing solution with high efficiency and to recover the metal from the metal ion-containing solution with high recovery efficiency. A method for concentrating or recovering a metal in a metal ion-containing solution in the present invention is the method comprising the following steps, a reduction and accumulation step to reduce the metal ion into a metal fine particle and also to accumulate the metal fine particle in the microorganism by allowing the microorganism and an electron donor B to act on a metal ion-containing solution W 0 and thus to obtain a solution W 1 that contains a microorganism having a metal fine particle accumulated therein; a concentration step to concentrate the solution W 1 that contains the microorganism having a metal fine particle accumulated therein by a filtration membrane and thus to obtain a concentrated solution W 2 ; and a return step to return the concentrated solution W 2 to first step above and thus to circulate. Further, A device for metal concentration or recovering in the present invention comprises the following: a storage unit 2 to store the solution W 1 , a concentration unit 3 to concentrate the solution W 1 that is transferred from the storage unit 2 by a filtration membrane, and a return unit 4 to return a concentrated solution W 2 that is concentrated in the concentration unit 3 to the storage unit 2.

1 . A method for concentrating a metal in a metal ion-containing solution, the method comprising the following (1) to (3):
 (1) reducing a metal ion into a metal fine particle and accumulating the metal fine particle in a microorganism by allowing the microorganism and an electron donor to act on a metal ion-containing solution and thus obtaining a solution that comprises the microorganism having the metal fine particle accumulated therein;   (2) concentrating the solution that comprises the microorganism having the metal fine particle accumulated therein by a filtration membrane and thus obtaining a concentrated solution; and   (3) returning the concentrated solution to (1) above.   
     
     
         2 . The method for metal concentration according to  claim 1 , wherein the metal ion is an ion of one or more elements selected from the group consisting of Au, Ag, Pt, Pd, Rh, Ir, Ru and Os. 
     
     
         3 . The method for metal concentration according to  claim 1 , wherein a metal that is produced by reducing the metal ion coexists when the microorganism and the electron donor act on a metal ion-containing solution in (1) above. 
     
     
         4 . The method for metal concentration according to  claim 1 , wherein the electron donor is an organic substance having from 1 to 7 carbon atoms. 
     
     
         5 . The method for metal concentration according to  claim 1 , wherein the electron donor is at least one or both of an aliphatic carboxylic acid having from 1 to 3 carbon atoms and a salt thereof. 
     
     
         6 . The method for metal concentration according to  claim 1 , wherein the electron donor is at least one or both of formic acid and a salt thereof. 
     
     
         7 . The method for metal concentration according to  claim 1 , wherein the microorganism is iron-reducing bacteria. 
     
     
         8 . The method for metal concentration according to  claim 7 , wherein the iron-reducing bacteria are bacteria belonging to the genus  Shewanella.    
     
     
         9 . The method for metal concentration according to  claim 8 , wherein the bacteria belonging to the genus  Shewanella  are  Shewanella algae  or  Shewanella oneidensis.    
     
     
         10 . The method for metal concentration according to  claim 1 , wherein an average pore size of the filtration membrane is from 0.01 to 1.0 μm. 
     
     
         11 . A method for recovering the microorganism from the solution formed as a result of (1) in  claim 1 , the method comprising the following (4):
 (4) recovering the solution so as to have a cell concentration of 1.0×10 17  cells/m 3  or less.   
     
     
         12 . A method for metal recovery from a metal ion-containing solution, the method comprising the following (1′) to (4′):
 (1′) accumulating a metal ion in a microorganism by allowing the microorganism to act on a metal ion-containing solution and thus to obtain a solution that contains a microorganism having the metal ion accumulated therein; 
 (2′) concentrating the solution that comprising the microorganism having the metal ion accumulated therein by a filtration membrane and thus to obtain a concentrated solution; 
 (3′) returning the concentrated solution to (1′) above; and 
 (4′) recovering the solution that contains the microorganism having a metal fine particle accumulated therein so as to have a cell concentration of 1.0×10 17  cells/m 3  or less. 
 
     
     
         13 . The method for metal recovery according to  claim 12 , wherein the metal ion is an ion of one or more elements selected from the group consisting of Ga, In, Zn, Sn and a lanthanoid. 
     
     
         14 . The method for metal recovery according to  claim 12 , wherein the microorganism is iron-reducing bacteria. 
     
     
         15 . The method for metal recovery according to  claim 14 , wherein the iron-reducing bacteria are bacteria belonging to the genus  Shewanella.    
     
     
         16 . The method for metal recovery according to  claim 15 , wherein the bacteria belonging to the genus  Shewanella  are  Shewanella algae  or  Shewanella oneidensis.    
     
     
         17 . The method for metal recovery according to  claim 12 , wherein an average pore size of the filtration membrane is from 0.01 to 1.0 μm. 
     
     
         18 . A device for metal concentration, comprising the following (a) to (c):
 (a) a storage unit to store a solution that is obtained by allowing a microorganism and an electron donor to act on a metal ion-containing solution so as to reduce a metal ion into a metal fine particle and also to accumulate the metal fine particle in the microorganism or by allowing the microorganism to act on a metal ion-containing solution so as to accumulate a metal ion in the microorganism and contains a microorganism having a metal fine particle or a metal ion accumulated therein;   (b) a concentration unit to concentrate the solution that is transferred from the storage unit and contains the microorganism having a metal fine particle or a metal ion accumulated therein by a filtration membrane; and   (c) a return unit to return a concentrated solution that is concentrated in the concentration unit to the storage unit.   
     
     
         19 . The device for metal concentration according to  claim 18 , the device further comprising the following (e):
 (e) a measurement unit to measure a cell concentration of the solution that is supplied to the concentration unit and contains the microorganism having a metal fine particle or a metal ion accumulated therein.   
     
     
         20 . A device for metal recovery, comprising the following (a) to (d):
 (a) a storage unit to store a solution that is obtained by allowing a microorganism and an electron donor to act on a metal ion-containing solution so as to reduce a metal ion into a metal fine particle and also to accumulate the metal fine particle in the microorganism or by allowing the microorganism to act on a metal ion-containing solution so as to accumulate the metal ion in the microorganism and contains a microorganism having a metal fine particle or the metal ion accumulated therein;   (b) a concentration unit to concentrate the solution that is transferred from the storage unit and contains the microorganism having a metal fine particle or a metal ion accumulated therein by a filtration membrane;   (c) a return unit to return a concentrated solution that is concentrated in the concentration unit to the storage unit; and   (d) a recovery unit to recover the solution that contains the microorganism having a metal fine particle or a metal ion accumulated therein from at least one or both of the storage unit and the concentration unit.   
     
     
         21 . The device for metal recovery according to  claim 20 , the device further comprising the following (e):
 (e) a measurement unit to measure a cell concentration of the solution that is supplied to the concentration unit and contains a microorganism having a metal fine particle or a metal ion accumulated therein.