Improvements in Treating Cupric Sulphate Solutions.
Year: 1899

page_text: Date of Application, 27th June, 1899-Accepted, 16th Sept., 1899
COMPLETE SPECIFICATION.
Improvements in Treating Cupric Sulphate Solutions.
I, OTTOKAR HOFMANN, of Ash Street (top of hill), Argentine, in the County of
Wyandotte and State of Kansas, United States of America, Metallurgical
Engineer, do hereby declare the nature of my invention and in what manner
the same is to be performed, to be particularly described and ascertained in and
by the following statement:-
The object of the invention is to provide a new and improved method for
treating cupric sulphate solutions, to bring the same into a purified condition
for direct manufacture into blue vitriol or other substance, or for use in chemical
and metallurgical processes.
If copper matte, a product of smelting, and consisting principally of copper
and iron sulphide or a sulphuretted copper ore after being subjected to an
oxidizing roasting, is treated with hot diluted sulphuric acid, then a solution
of cupric sulphate is obtained which contains large quantities of iron besides
more or less arsenic, antimony, nickel, cobalt etc. Such an impure cupric sul-
phate solution is not suitable for the manufacture of blue vitriol because the
impurities, especially the ferrous sulphate, also crystallizes out of the concen-
trated solution and make the product of blue vitriol too impure for the market.
There is no practical and rational method known by which a cupric sulphate
solution can be freed from the above-named impurities, and the manufacturers
are obliged, in order to produce a pure solution, to eliminate the impurities
from the material before it is subjected to the action of the diluted sulphuric
acid, and this is a costly process. There are two methods in use for purifying
the copper material. One is a very slow method, and consists in converting the
copper sulphide of the matte into metallic copper by repeated roasting and
smelting operations, and then the metallic copper is granulated and dissolved
by the alternating action of air and hot diluted sulphuric acid. The other
method is to concentrate the copper in the matte by repeated roasting and smelt-
ing until the same contains about from 80 to 85 per cent. copper. By this
repeated roasting and smelting the largest portion of the iron and other impuri-
ties are oxidized and go in the slag. This highly concentrated matter is pul-
verized, roasted and treated with sulphuric acid. This method involves great
expense, and results in a considerable loss of copper.
By my new method, the crude cupric sulphate solution is refined, and refining
of the material is therefore not required. Any copper matte or sulphuretted
copper ore, rich or poor in copper, after roasting, furnishes a suitable material.
In order to carry the above mentioned method into effect, I proceed in detail
as follows:
Common copper matte or sulphuretted copper ore is pulverized and oxidized
by roasting, and treated with hot diluted sulphuric acid, either in an agitating
tank or in a leaching tank. The amount of sulphuric acid necessary for produc-
ing the neutralizing effect depends upon the nature of the ore or matte. Atten-
tion has to be paid that the resulting cupric sulphate solution is neutral or as

page_text: nearly neutral as possible. The neutral crude solution is charged into a suit-
able receptacle, most conveniently into a high tank or tower made of a cast
iron skeleton frame and lined with heavy sheet lead. The bottom of the tower'
is funnel-shaped. Through the lowest part of the latter enters a lead pipe, pro-
jecting 12 to 18 inches into the tower, and connected with an air compressor.
To prevent the solution from flowing into the compressor, the pipe must ascend
above the top of the tower and then descend to the compressor. Near the
inlet of the air pipe is the outlet or discharge pipe for the solution. By means
of a steam coil the solution in the tower can be heated.
When the tower is charged with solution, steam is turned into the coil and
the solution heated to about 75° to 80° C.; then air is forced through the solu-
tion, and pulverized cupric oxide added in required quantities, which depend on
the amount of impurities contained in the solution and the amount of free acid, if
any which is present. As the roasted matte contains a large amount of cupric oxide,
roasted matte can be used to great advantage in place of pure cupric oxide. The
ascending air keeps the particles of matte or cupric oxide suspended and in motion.
After from three to four hours of operation, the above-named impurities,
together with some basic sulphate of copper are precipitated. The end of the
operation is ascertained by test for iron. Then the liquor, together with the
precipitate is discharged into an agitating tank, and from there, by means of
a pressure tank, forced into a filter press. The solution leaving the press is
now free from iron, arsenic, antimony, nickel and cobalt, and can be directly
subjected to evaporation for the manufacture of blue vitriol, or used for any
other technical purpose. To free the precipitate from the basic sulphate of
copper, the same when removed from the press, is treated in an agitating tank
with a cold and weak acid (about 2 per cent.) Such weak acid will readily dis-
solve the basic copper, while it will only slightly attack the oxides of the pre-
cipitated impurities.
The chemical reaction in this process can be expressed by the following
equation.
2 Fe SO + 0 + 2 CuO
=
Fе0+2 CuSO
It will be seen that the cupric oxide which is used together with air to pre-
cipitate the iron, combines with the sulphuric acid of the ferrous sulphate and
goes in solution as cupric sulphate, which is an advantageous feature of the
process, because the precipitant is converted into the same chemical substance
from which it eliminated the impurities, making the solution stronger in copper.
The crystals of blue vitriol obtained by my method are much purer and more
permanent than those usually found in the market, because they crystallize out
of a very pure neutral solution and do not contain any free acid. They can be
exposed to light for years and do not contain any free acid. Direct sunlight,
however, has to be avoided. This method is much less expensive than others
in use, and does not require so costly and extensive a plant.
When air alone is forced through the solution without an addition of cupric
oxide a part of the iron precipitates as basic sulphate.
The above described apparatus does not form a part of my invention. To
successfully operate my new method, any apparatus which affords the require-
ment for the treatment, can be used.
Having now particularly described and ascertained the nature of the said in-
vention and in what manner the same is to be performed, I declare that what
I claim is:-
1. The herein described method for refining crude cupric sulphate solutions,
consisting in precipitating the impurities contained in the solution by the addi-
tion of cupric oxide and the injection of air into the solution, as set forth.

page_text: 2. In process herein described and claimed under Claim 1, heating the solu-
tion before adding cupric oxide thereto, substantially as described.
3. Neutralizing the solution before heating it as specified under Claim 2,
and further treating it as specified under Claim 1, substantially as described.
4. In the processes claimed under Claims 1 to 3, substituting for the cupric
oxide specified therein, pulverized material containing cupric ozide, such as for
instance, oxidized copper matte, substantially as described.
PRE
1000
A. M. & WM. CLARK,
Chartered Patent Agents, 53, Chancery Lane, London.