Drainage aid for metal heap leaching

#The present application relates to an improved process for leaching of metal from ore heaps in which a lixiviant solution is brought into contact with the ore to form a “pregnant” solution, from which the metal is ultimately separated. The improvement lies in contacting the metal ore with an ethoxylated aliphatic alcohol to improve percolation of the lixiviant through the heap.

#In recent years, heap leaching has become a cost effective method for recovering precious metals such as gold or silver from low grade ores. In the process, a lixiviant system, comprising a ligant and an oxidant is used to dissolve out the desired precious metal from the ore. As used herein, the phrases “lixiviant system” and “lixiviant solution” will be used interchangeably and do not imply a true chemical solution—only a chemical combination adapted to extract the mineral value in the ore.

#In heap leaching, the metal bearing ore may be obtained from an open pit mine or the like and is crushed to produce an aggregate that is coarse enough to expose the desired mineral values but fine enough to allow intimate contact of the lixiviant system or solution therewith. The lixiviant solution may be distributed over the top of the metal ore heap via sprinklers, wobblers, or other similar equipment. The barren lixiviant “percolates” through the heap to perform its desired function with the metal and the resulting pregnant solution is then collected by an impervious leach pad or the like located at the bottom of the heap. The pregnant solution is then subjected to conventional mineral recovery techniques to obtain the desired precious metal.

#FIG. 1 is a graph showing the results of activated carbon gold uptake tests reported in Example 4; and

#FIG. 2 is a bar graph illustrating the tests reported in Example 5 showing the uptake of the drainage aids by gold ore.

#The drainage aids in accordance with the invention are ethoxylated aliphatic alcohols having the formula

#HO[Brketopenst]CH2CH2—O[Brketclosest]nR

#wherein R is C4-C20 alkyl or C4-C20 alkenyl with n being about 2 to 20. More preferably, R is C4-C14 alkyl or C4-C14 alkenyl and n is about 3 to 8.