PROCESS FOR THE CONCENTRATION OF SULFIDIC NICKEL ORES

PROCEDE DE CONCENTRATION DE MINERAIS SULFURES DE NICKEL

English Abstract

ABSTRACT
A process for the concentration of sulfidic nickel
ores from basic rocks by means of froth flotation is described.
The flotation reagent used is dithiophosphate with a pH of
3.5-6Ø

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for the concentration of sulfidic
nickel ore from basic rocks by means of flotation, whereby the
pulp obtained is treated with a strong acid so that the pH during
the flotation is 3.5-6.0, characterized in that dithiophosphate
with the following formula
<IMG>
where RI and RII, independently of each other, represent hydro-
carbon groups having 2-22 carbon atoms, or a salt of the same,
is added as a collector agent at the latest immediately after the
acid addition, and the sulfidic nickel mineral is flotated in a
manner known per se.
2. A process according to claim 1, wherein said hydro-
carbon groups have 2 to 12 carbon atoms.
3. A process according to claim 1, characterized in
that, after the addition of the sulfuric acid and the dithiophosphate,
the pulp is conditioned for a minimum of 15 minutes.
4. A process according to claim 3 wherein said pulp
is conditioned for 20 to 60 minutes.
5. A process according to claim 1, characterized in
that, independently of each other, RI and RII are alkyl groups,
phenyl-bearing groups, or cycloaliphatic groups.
6. A process according to claim 1, characterized in
that dithiophosphate is added in an amount which is 25-750 grams
per ton of ore.
7. A process according to claim 3, characterized in
that, independently of each other, RI and RII are alkyl groups,
phenyl-bearing groups, or cycloaliphatic groups.
8. A process according to claim 5, characterized in

that, independently of each other, RI and RII are alkyl groups,
phenyl-bearing groups, or cycloaliphatic groups.
9. A process according to claim 1, 3 or 5, wherein the
dithiophosphate is added in an amount of 50 to 400 grams per ton of
ore.
10. A process for the concentration of sulfidic nickel
ore from basic rocks by means of flotation, thereby the pulp obtained
is treated with a strong acid so that the pH during the flotation is
3.5 to 6.0, characterized in that dithiophosphate of the formula
<IMG>
or a salt thereof, wherein RI and RII are alkyl groups, phenyl-
bearing groups or cycloaliphatic groups having from 2 to 12 carbon
atoms, is added as a collector agent at the latest immediately after
the acid addition in an amount of 50 to 400 grams per ton of ore,
and the sulfidic nickel mineral is flotated in a manner known per
se, said pulp being conditioned for 20 to 60 minutes after the
addition of acid and the dithiophosphate.

Description

109564(~
The present invention relates to a process for
the concentration of sulfidic nickel ores from basic rocks
by means of froth flotation. The flotation reagent used is
dithiophosphate with a pH of 3.5-6Ø
Sulfidic nickel ores in which valuable metals
are present in the form of various sulfides, e.g.
pentlandite (NiFeS2) and heazlewoodite (~i3S2) have long
been concentrated by froth flotation; primarily sulfur-
bearing collector agents such as alkyl xanthates and
dialkyl dithiophosphateshave been found to be suitable for
this purpose. The flotation process is usually carried
out within a pH range of 6-8.
Nevertheless, there are certain ultrabasic ore
types, peridotites, which contain nickel minerals. In
the case of these ores it has been observed that a better
nickel yield is obtained in froth flotation if a finely-
ground ore is first treated with a relatively large
quantity of sulfuric acid and thereafter the flotation is
carried out within a pH range of 3.5-6, using alkyl
xanthate as the collector agent. The
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~ improved yield is most probably explained by the fact that
! these ores are partly oxidized and that by means of the acid
; treatment nickel sulfide surfaces are freed with the result ~
I that the collector agent can reach them. In spite of this ~`
I improved technology, it has proven difficult to obtain on one
l hand the desired nickel content in the concentrate, i.e. over
¦ 6% nickel, and on the other hand a high total yield of nicke],
¦ i.e. a yield of over 70%.
i It has now been found possible to improve considerably both
¦ the purity and the total yield in the nickel ore flotation of
¦ the type described above, by selecting dithiophosphat as the
~ collector agent and by adding it to the pulp in question at
¦ the latest immediately after the addition of sulfuric acid.
¦ The duration of the conditioning of the pulp is usu211y 15
~ minutes, but pre~erably 20-60 minutes, whereafter the sulfidic
¦ nickel mineral is flotated at pH 3.5-6.0 in a manner known ~''3'
se. , I;
.
When using the process according to the invention it is crucial
I . , . ., ,.. ; ~ ,.. .. . ,.... , .. . ......... ., .. ., - ....... .. , ... - .. ~ ~
that dithiophosphate is not added substantially later than the
sulfuric acid. When sulfuric acid is added, the pH lowers
momentarily to approx. 1-2, whereafter it, after approx. 3-10
minutes, rises to approx. 3.5-6 under the effect of that basic
mineral at the pH of which the flotation is carried out.
"Substantial" here means that the time period must not sur:pass
~ minutes, suitably 2 minutes, preferably 1 minute. ~hen using
the process according to the invention the reagent is thus
present for the period during which the pH of the pulp surpasses
the pH prevailing during the actual froth flotation. According
to one advantageous embodiment, the collector agent and the
~ulfuric acid are added simultaneously. When so desired, the
dithiophosphate can also be added before the sulfuric acid.
The reason why the time of the dithiophosphate addition is 50 .
important has not yet been explained, ~ut according to one
theory certain nickel surfaces are momentarily fxeed at the low
p~ which prevails at the time of the sulfuric acid addition and
immediately thereafter. l
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The dithiophosphate compounds according to the inven~ion are
compounds Wit]l the general formuia
RIO ~ ,~ S o
R O SH
where RI and RII, ndependently of each other, represent a
hydrocarbon group having 2-22 carbon atoms, preferably 2-12
carbon atoms, or a salt of the same. Such hydrocarbon groups
can be aliphatic groups, phenyl-bearillg groups, or cycloaliphatic
groups. Some special examples of the suitable groups are alkyl
groups such as ethyl, propyl, isopropyl, butyl, isobutyl,
secondary butyl, hexyl, 2-ethyl-hexyl, octyl, nonyl, decyl,
and dodecyl; phenyl-bearing groups such as phenyl, metnyl-phenyl,
and dimethyl-phenyl; saturated cycloaliphatic groups such
as cyclohexyl and cyclohexyl-eth~l. The addition of dithio-
phosphate is 25-750 grams, preferably 50-400 grams, oer one ;'
tonne of the ore on which the froth flotation is performed. ~ !
When using the process according to the invention it is also
possible, if so desired, to add conventional additives during
the flotation, such as secondary collector agents. Some examples
of suitable secondary collector agents are water insoluble
hydrophobic substances which are emulsified in water by means
of a suitable emulsifier. Other additives include compressing
and activating agents, frothers, etc.
e process according to the invention is also illustrated by
the following examples.
Example I
A peridotite ore containing 0.50% nickel in the form of a
nickel sulfide mineral and~ furthermore, copper in the form of
chalcopyrite, CuFeS2, magnesium sil~cates c~rresponding to
35% ~gO, and a totai sulfide amount correspond-ing to 2~ S, I
wa~ crushed into nuggets of 2-4 cm. Thereafter Lhese nuggets l
were ground in a grinder for 10 minutes in the presence of ¦
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~ 4 109S64~
¦ 0.8 1 water per one kg of ore. After grinding, 80% by weight
¦ passed a sieve with a mesh of 65 ~m. A mineral pulp -v7,~s :~
I prepared from the ore thus ground (1 ~ilogram of ore and 1 liter
¦ of water), and this pulp was transferred into a flotation cell.
f Sulfuric acid, a flotation reagent, and a frother were added
I according to the tables below. A~er the crude flotation the
operation was repeated 3 times.
~ Experiment 1 ,
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Time - min ,
1,
¦ 0 Sulfuric acid 20 kg/tonne
15 Potassium amyl xanthogenate 500 g/tonne pH 4.0
20 Start of crude flotation pH 4.5
37 Potassium amyl xanthogenate 250 g/tonne pH 4.4 j
41 " 250 g/tonne pH 4.5
46 ~ 250 g/tonne pH 4.6 1
~ 52 " 250 g/tonne pH 4.6 ~
1 59 ~ 250 g/tonne p~ 4.6
66 " 500 g/tonne p~ 4.6
73 Start of 1st repeat pH 4.7
; ~ 90 Start of 2nd repeat ~ . , pH 4.9~ ~105 Start of 3rd repeat pH 5.1 ~;
A frothing agent, dipropylene-glycol-monomethyl-ether, was
added at a total rate of 375 grams/tonne between 37 and 66
minutes.
Exper _ ent 2
~ :f~ Tim - min
0 Sulfuric acid 30 kg/tonne
~1 20 Di-isobutyl dithiophosphate 150 g/tonne pH 4.0
25 Start of crude flotation pH 4.2
62 Di -iso~butyl ~ithiophosphate 100 g/tonne pH 4.6 ~
65-80 1st repeat pH 5.1-4.7 ~¦
80-93 2nd repeat pH 4.9
93-104 3rd repeat pH 5.1
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Exper ment 3
_ _- . s
~ne - min ` "
_ ~.
0 Sulfuric acid 33 kg/tonne ,
Di-isobutyl dithiophosphate 150 g/tonne 2
l pH 1.7 ,~'
2 pH 2.1 j~,,
2 pH 3.6
30 Start of crude flotation pH 4.2 ~,
39-79 Dipropylene-glycol-monomethyl-ether
¦Frother 120 g/tonne. Continuous crude flotation '','
-79-96 1st repeat pH 4.8 ~,
96-103 ~nd repeat pH 5.0 ,,
103-lll 3rd repeat pH 5.1 ~`
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The settling products of the various flotation stages and the ~ '
froth of the last stage were dried, we,ighed and analysed for
nickel. T'he following results were thereby obtained. 2':
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, Crude flotation 1st repeat 2nd reFeat 3rd repeat
Concen- Yield Concen- Yield Concen- Yield Col~cen- Yield
,,,, ,,,,~,', ,,tration tration tration tration
Experiment l 1.5476.2 3.83 50.1 5.43 45.8 6.67 43.2 ..
. . j,~ ! .
,~ Experiment 2 0.87 73.2 1.90 36.9 4.1 32.9 7.1 30~0 ~,
EX~erim~nt 3 2.1 76.8 5.1 71.6 6.48 69.7 7.2 68.5
: ~: 22~ '
Experiment 1 represents the model of the current commercially
used froth flotation technology in the respect that the addition ,
-~ ~ o~ the collector agent is continuous and the conditioning
pe.riod after the first addition of the collector agent is only
l 5 minutes. Even though the total addition of potassium amyl ~-~
,; ~ xanthogenate is 2250 g/tonne, the nickel yield is poor, only
~ 43~ af ter the third repeat operation. ~r I
,, ~ Experiment 2 the collector agent was di-isobutyl dithio-'~ phosphate, which was added at two staqes, The first addition ~'
was 20 minutes after the sulfuric acid addition and the second ~
one 5 minutes later. The flotation result was good in terms of ~ '
r ickel concentration, but poor in ter!r.s of the yield.

~ 6
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In Experiment 3, which was performed according to the
invention, the collector agent and the sulfuric acid were added
simultaneously. The conditioning period was 30 minutes. The
values obtained for the nickel concentration and the yield,
7.2~ and 68.5%, respectively, are both highly satisfactory.
When these are compared with the values obtained in
Experiments 1 and 2, it must be taken into consideration that
the amount of reagent in Experiment 3 was less than 7~. Thus
it was 60~ of the amount used in the reference experiments.
~he process according to the invention thus represents a
considerably improved technique in this field.
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