Composition of a filter cake for precious metals recovery

Abstract

A process is provided for preparing a spent noble metal fixed-bed catalyst for precious metals recovery, comprising: a) adding the catalyst to a caustic solution to wash the spent catalyst and to make a wash slurry having an alkaline pH, wherein the spent catalyst has been in contact with chloroaluminate ionic liquid catalyst, and wherein the spent catalyst comprises from 5 to 35 wt % chloride; and b) filtering the wash slurry and collecting: i) a filter cake having from at least 70 wt % of the chloride in the spent catalyst removed and having the noble metals retained, and ii) a wash filtrate. Also provided is a filter cake comprising a washed consolidated cake having 40 to 75 wt % solids, a cake moisture content from 25 to less than 60 wt %, 0.1 to 1.5 wt % total noble metals, and a residual chloride content of from zero to less than 4 wt %.

It is claimed: 
     
         1 . A filter cake suitable for precious metals recovery, comprising: a washed consolidated cake having a % solids from 40 to 75 wt %, a cake moisture content from 25 to less than 60 wt %, 0.1 to 1.5 wt % total noble metals, and a residual chloride content of from zero to less than 4 wt % that is at least 80 wt % lower than an initial chloride content of a spent noble metal fixed-bed catalyst that had been in contact with a chloroaluminate ionic liquid catalyst and the chloroaluminate ionic liquid catalyst was trapped inside the spent noble metal fixed-bed catalyst. 
     
     
         2 . The filter cake of  claim 1 , wherein the washed consolidated cake is not water reactive. 
     
     
         3 . The filter cake of  claim 1 , wherein the washed consolidated cake comprises a filter aid. 
     
     
         4 . The filter cake of  claim 3 , wherein the filter aid comprises from 50 to 98 wt % silica. 
     
     
         5 . The filter cake of  claim 3 , wherein the filter aid is selected from the group consisting of diatomaceous earth, fly ash, perlite, cellulose, calcined rice hull ash, and fibers from used paper products. 
     
     
         6 . The filter cake of  claim 5 , wherein the filter aid is calcined rice hull ash. 
     
     
         7 . The filter cake of  claim 1 , wherein the washed consolidated cake comprises no aluminum hydroxide colloidal gels. 
     
     
         8 . The filter cake of  claim 1 , wherein the cake moisture content is from 30 to less than 50 wt %. 
     
     
         9 . The filter cake of  claim 1 , wherein the noble metals comprise platinum group metals. 
     
     
         10 . The filter cake of  claim 9 , wherein the platinum group metals comprise platinum, palladium, or a mixture thereof.