FIELD OF THE INVENTION
This invention relates to a method -for the preparation of pure
metal powder from metal salts.
BACKGOUND OF THE INVENTION
Recovery of pure metals from salts or- minerals is valued for
their commercial applications, A common method of production of a
refined metal powder involves a co-reduction reaction of an elec
trolysis from metal cations. The former method is carried in
solid or in s solution form of cations with a reducing agent
while the electrolysis is carried out with an electrolytic
solution of rations. Separation of the pure metal poudf-: from
byproducts after the reaction is a big challenge in solid state
co-reduction reaction. The metal particles, are very intimately
adhering to byproducts making it difficult tc separate using an
adequate proper solvent. A disadvantage with the other process is
that it involves mixing of a large volume in two solutions and
1 h u s it occurs at a v e ry s 1 o w rate as per e >; p e r i m e n t a 1
conditions. Meanwhile, the metal particles get surface oxidized
by reaction with solution.
Also co-reduction reactions with inverse micelles CUS ratent
No.5147841 (1992)3 are developed to carry out the reaction in an
oxidation protective atmosphere in encapsulated micelles. It is a
very violent reaction which occurs at adjunction of two compo-
nents on adding the reducing agent (solution) to the metal
cations (solution) dropwise by stirring the solution vigorously.
Overall, it also takes a period of time to accomplish the
reaction, by the time the sample does have s significant reaction
with sc -..tion.
OBJECTS OF THE INVENTION
f'V-. object of this invention is to propose a method 1c; the p'"fpa-
:'dtion of pure metal powder from metal salt;;.
>¦"•- further object of this invention is to propose a method 'l^ the
preparation of pure metal powder from metal salts wn :'c;_- : =
simple, unique, efficient and cost-effective.
Further objects arid advantages of this indention wil] be more
apparent: from the ensuing description.
At the outset of the description which follows, it is to be
understood that the ensuing description only ll lust-rate'. a
particular form of this invention. However, such a particular
form is only an exemplary embodiment, and without intending to
imply any limitation on the scope- of this invention. Accordingly,
the description is to be understood as an exemplary embodiment
and reading of the invention and not intended to be taken
t estrictively.
BRIEF DESCRIPTION OF THE INVENTION
According to this invention is provided a process for the preps-
ration of pure metal from metal salts.
In this invention, a reducing agent of a solid of Al metal with
nascent surface is efficiently employed to co-reduce an M metal
salt into a refined M metal powder as soon as it is immersed in
ar. aqueous solution of salt. The reaction occurs throughout the
solution so that it accomplishes very quickly within 5 to 10
mins. in a 200g of reaction catch. The obtained metal powder- is
self separated from the solution and settles down in the
conainer. It is recovered by decanting and then wished with
distilled water to ensure it to be free from byproduct irnputries.
powder i *~ dried in vacuum at roor,i temperature.
q +
A nascent Al—surface efficient to induce M - M reaction is
refined from a refreshed surface (obtained by depressing and
washing .in distilled water and then treating with a mineral acid
:.,uch as H'Cl followed by washing in water again) by reacting with
2 +
Hg -cations. In this process, the specimen is dipped ir; an
2+
aqueous Hg solution and then rinsed properly with distiiled
2 + ' 2 +
mater to remove the excess Hg -cations. The Hg cations reset
with Al atoms at the surface by getting reduced into Hg metal as
2+ 3+
per the reaction of Hg ¦+¦ 2 Al - 3 Hg + 2 Al . It forms in a
thin amalgam film with nascent Al surface and that very
intimately adheres to the nascent Al surface. The amalgam induces
any inherent surface oxide at mother Al surftice to pile off from
the surface and to segregate over the amalgam alongwith other
byproduct impurities. This is removed easily alongwith excess
amalgam, if any, by washing in distilled water. The obtained
-pecimen has reactive nascent surfaces. They conduct the desired
ro-reduction reaction of dispersed M cations in an aqueous
solution. Otherwise, Al-metal surface is available ~ith a thin
indistinct inseparably oxide film of its own. That protects it
c-t-
f:ori i t'~ oxidation reaction with M cations.
A riesi -ably controlled N ¦- - co-reduction rpschoi f mm
dispET=.?'! ir.etsl cations r' in «: aqueous solution oc;:^:"'; fit
cone, ent - z \ * on of 1 N. For example, in case with an aqueous
solution of CoCl , it can be written as
3 C'.oC'J. + ? Al .....-........ 3 Co + ',' A] CI
7 h i ¦:-, i :.. a se 1 f — i ncuc ed Epo'it..:neou= exothermic ;?tt lio;: -uj.;: !¦
occurs by generating a lot of heat of reaction. The heat r ¦¦'. 1 e - ;¦¦;¦. e d
during the reaction unwanted!y ra::i;.es average t empe ra + ut e of
total solution with metal powder, if not controlled by an
external cooling. It causes, unwanted surface oxidation of metal
particles in the solution. Therefore, in order to minimize the
surface oxidation, the whole reaction is carried in a closed
reactor 'having the facility for releasing excess pressure if
develops during it) at controlled temperature with a predeter-
mined quantity of !MaCl . AiCl byproduct in this reaction is
highly soluble in water and ultimately gets filtered out along
ui i th the f i n a 1 so 1 u 11 on .
The CD-reduction process explored here seems to be rather
general. It is successfully tested for recovering a series of
metals of iron, cobalt, nickel, copper, tin and silver in form oi
refined powders directly from their salts. Particle i-i:e and
niorpholog> can be varied over a wide range from a feu: micrometers
to a ndriGineter scale according to initial concent ^at i.on of solu-
tion E.'-;d other exp e r-i men t a 1 cr-noi tion'j. S^all particles in '5 tc>
r.'0 riiji d i a(Tif? t e ?"¦ have a rspher icsl bhape, i.sT'qer particle:; appear in
el 1 ipse ids j (^ thin plsi;?^- -¦i-i;.f:r5.
Catc-d th--:: ?th day ot ..: ¦ if.'ijr,!;V, ;M(-M.

This invention relates to a process for the preparation of pure metal from metal
salts comprising
immersing an aluminium metal plate with nascent surface into an aqueous
solution of a salt of a transition metal,
filtering the transition metal powder obtained, washing and drying to obtain the
pure metal.