Re: What chemical reactions are involved in the production of nickel?

Nickel was named after Satan because of the difficulty of separating it 
from copper.  Nickel is usually found as a sulfide, although it can also be 
found as an oxide or a silicide.  It is almost always found in combination 
with copper and other metals such as iron and cobalt.

A lot of the history of extracting nickel can be found on INCO's web site:
http:\\www.inco.com .  INCO, which used to be named International Nickel, 
is the largest producer of nickel.  Another useful website is the Nickel 
Page: http:\\www.nipera.org .

In the process for extracting nickel, nickel ore is first crushed and then 
concentrated by flotation.  The nickel concentrate is then sent to the 
smelter, where it is heated to high temperature.  During this reaction, the 
sulfur is oxidized to form SO2 and SO3.  This reaction is called roasting. 
 So the first major reaction is likely nickel sulfide reacting with oxygen 
to form nickel oxide and sulfer dioxide.  If you controlled the amount of 
oxygen being added to this reaction, it may be possible to only oxidize the 
sulfer, resulting in metallic nickel along with other metals.  However, it 
is probably easier to perform a two step process in which the sulfer is 
removed in the first step, and reducing agents such as methane or carbon to 
be used to reduce nickel oxide to metallic nickel in the second step.

After reduction, the metallic nickel is pretty impure.  There are two 
methods used to separate the nickel from other metals.  The first is called 
electrowinning, in which an impure cast bar is electroplated.  By 
controlling the chemistry of the plating bath along with the voltage, 
fairly high purity nickel can be produced.  Up to this point, the methods 
for producing copper and nickel are almost the same.

The other process for producing high purity nickel is the most unique.  
Nickel will react with carbon monoxide to form a gaseous nickel compound 
called nickel carbonyl.  The nickel is removed in the vapor phase, leaving 
behind all of the copper, cobalt, and other metals.  The nickel carbonyl is 
 heated to a higher temperature, where it becomes unstable and decomposes 
into metallic nickel and carbon monoxide.  The metallic nickel forms round 
pellets, and the carbon monoxide is recycled to refine more nickel.  Pretty 
slick, don't you think.  The nickel carbonyl can also be used to coat 
things with nickel, such as graphite fibers.  The only problem is that 
nickel carbonyl is very poisonous, so your process controls and containment 
have to be very, very good.