System and method for recovering metal from metal-containing waste liquid

Abstract

Disclosed is a system for recovering metal from metal-containing waste liquid. The system includes a waste liquid storage unit, an extraction unit, and an electrolysis unit. The waste liquid storage unit is configured to store a metal-containing waste liquid. The extraction unit is in fluid connection with the waste liquid storage unit and includes an extraction device and a back-extraction device. The extraction device is configured to collect a target metal ion present in the metal-containing waste liquid, and the back-extraction device is configured to back-extract the target metal ion into a back-extracting liquid to form a metal compound. The electrolysis unit is in fluid connection with the waste liquid storage unit and the extraction unit, configured to reduce the target metal ion to a solid metal, or to dissociate the metal compound and deposit a solid metal.

What is claimed is: 
     
         1 . A system for recovering metal from metal-containing waste liquid, comprising:
 a waste liquid storage unit configured to store a metal-containing waste liquid;   an extraction unit in fluid connection with the waste liquid storage unit, including an extraction device and a back-extraction device, wherein the extraction device is configured to collect a target metal ion present in the metal-containing waste liquid, and the back-extraction device is configured to back-extract the target metal ion into a back-extracting liquid to form a metal compound; and   an electrolysis unit in fluid connection with the waste liquid storage unit and the extraction unit, configured to reduce the target metal ion to a solid metal, or to dissociate the metal compound and deposit a solid metal.   
     
     
         2 . The system according to  claim 1 , wherein the extraction device is in fluid connection with the back-extraction device through a circulation pipeline, and the electrolysis unit is in fluid connection with the waste liquid storage unit and the circulation pipeline through an inlet pipeline thereof. 
     
     
         3 . The system according to  claim 2 , wherein a top discharge end of the waste liquid storage unit is in fluid connection with an top inlet end of the extraction device, the circulation pipeline includes a first liquid delivery pipe and a second liquid delivery pipe, a top discharge end of the extraction device is in fluid connection with an top inlet end of the back-extraction device through the first liquid delivery pipe, and a bottom inlet end of the extraction device is in fluid connection with a bottom discharge end of the back-extraction device through the second liquid delivery pipe. 
     
     
         4 . The system according to  claim 3 , wherein the inlet pipeline of the electrolysis unit includes a waste liquid delivery pipe, a back-extracting liquid discharge pipe, and an inlet pipe, a bottom discharge end of the waste liquid storage unit is in fluid connection with one end of the inlet pipe through the waste liquid delivery pipe, the other end of the inlet pipe is connected to a top inlet end of the electrolysis unit, and the back-extracting liquid discharge pipe is connected between a branch point of the second liquid delivery pipe and the inlet pipe. 
     
     
         5 . The system according to  claim 1 , wherein the waste liquid storage unit, the extraction unit, and the electrolysis unit are in fluid connection with a treatment facility through a waste liquid treating pipeline. 
     
     
         6 . The system according to  claim 5 , wherein the waste liquid treating pipeline includes a first waste liquid discharge pipe, a second waste liquid discharge pipe, a third waste liquid discharge pipe, and at least one fourth waste liquid discharge pipe, another bottom discharge end of the waste liquid storage unit is in fluid connection with the facility management through the first waste liquid discharge pipe, the second waste liquid discharge pipe is connected between a branch point of the waste liquid delivery pipe and the first waste liquid discharge pipe, another bottom discharge end of the back-extraction device is in fluid connection with the first and second waste liquid discharge pipes through the third waste liquid discharge pipe, and at least one discharge end of the electrolysis unit is in fluid connection with the first waste liquid discharge pipe through the at least one fourth waste liquid discharge pipe. 
     
     
         7 . The system according to  claim 1 , further comprising a conditioning unit in fluid connection with the back-extraction device and the electrolysis unit, configured to recover the electrolyzed back-extracting liquid discharged from the electrolytic unit and supply the conditioned back-extracting liquid to the back-extraction device. 
     
     
         8 . The system according to  claim 7 , wherein the conditioning unit includes a chemical feeding tank and a conditioning tank, a bottom discharge end of the chemical feeding tank is in fluid connection with a first top inlet end of the conditioning tank through a chemical delivery pipe, and a bottom discharge end of the conditioning tank is in fluid connection with another top inlet end of the back-extraction device through a chemical supply pipe. 
     
     
         9 . The system according to  claim 8 , wherein the waste liquid treating pipeline further includes a waste liquid recycling pipe, a bottom discharge end of the electrolysis unit is in fluid connection with a second top inlet end of the conditioning tank. 
     
     
         10 . The system according to  claim 9 , further comprising a water source and an air source, the water source is in fluid connection with a third top inlet end of the conditioning tank through a water supply pipeline, and the air source is in fluid connection with air intakes of the electrolysis unit and the conditioning tank through an air supply pipeline respectively. 
     
     
         11 . The system according to  claim 1 , wherein the waste liquid storage unit includes a concentration detector for detecting metal concentration present in the metal-containing waste liquid. 
     
     
         12 . A method for recovering metal from metal-containing waste liquid, comprising the following steps:
 extracting a target metal ion from a metal-containing waste liquid;   back-extracting the target metal ion into a back-extracting liquid to form a metal compound; and   electrolyzing the back-extracting liquid to dissociate the metal compound and deposit a solid metal.   
     
     
         13 . The method according to  claim 12 , before the step of extracting a target metal ion from a metal-containing waste liquid, further comprising: directing the metal-containing waste liquid to a waste liquid storage unit for temporary storage. 
     
     
         14 . The method according to  claim 13 , wherein the step of directing the metal-containing waste liquid to a waste liquid storage unit for temporary storage further comprises: monitoring concentrations of metal ions in the metal-containing waste liquid. 
     
     
         15 . The method according to  claim 14 , between the step of extracting a target metal ion from a metal-containing waste liquid and the step of extracting a target metal ion from a metal-containing waste liquid, further comprising:
 electrolyzing the metal-containing waste liquid to reduce a target metal ion at relatively high concentration into a solid metal according the monitoring result; and   directing the electrolyzed metal-containing waste liquid back to the waste liquid storage unit.   
     
     
         16 . The method according to  claim 12 , wherein the back-extracting liquid includes hydrochloric acid. 
     
     
         17 . A method for recovering metal from metal-containing waste liquid, comprising the following steps:
 providing a metal-containing waste liquid containing first and second metal ions, wherein the concentration of the first metal ion is greater than that of the concentration of the second metal ion;   extracting the second metal ion from the metal-containing waste liquid;   electrolyzing the extracted metal-containing waste liquid to reduce the first metal ion into a first solid metal and back-extracting the second metal ion into a back-extracting liquid to form a metal-containing back-extracting liquid; and   electrolyzing the metal-containing back-extracting liquid to reduce the second metal ion into a second solid metal.   
     
     
         18 . The method according to  claim 17 , wherein the step of providing a metal-containing waste liquid containing first and second metal ions further comprises: directing the metal-containing waste liquid containing first and second metal ions to a waste liquid storage unit for temporary storage. 
     
     
         19 . The method according to  claim 18 , wherein the first metal ions at a relatively high concentration are copper ions and the second metal ions at a relatively low concentration are gold or silver ions. 
     
     
         20 . The method according to  claim 17 , wherein the back-extracting liquid includes hydrochloric acid.