, $ 1
,141
%
1L i i3
7TT'. CL=ING
OF
PITTR
LEA4"TT
SOLUTIONS
BY
CAMONATE.
OP
T717AIV-7
lightsthesis Is submitted to te vacuity of the
Iftssaalmsetts Institute of ",'Technology
in partial
1alfillment of the reqairements for the
Degree of Bachelor of Science
In the Departmentof Metallurgy
by
In the Departmentof
ectrochemistry
by
11Z1-
71--
I"
Cambridge,
Maso.
June, 1926.
.
I
19ff
Agipowledir,wnt
'".
We wish '.,o thanIt Pofassor
Carlo R. 7ayward
for his helpful recommendations
ad suzgestions for
methods of attack
olt
We wioh to
help in olving
the subject.
46
B. B. Trsmare for his
of anal7zing solations.
We wi5h to thank i"r. Laist,
Mr. William With,
Sr., for tir
11r. L"Lton, -nd
recomnendation o.
this subject 10brthesis .,fork.
.
-
.4
.
i.
INI
Z)
Za_js of vlontoLt s,
Page
Purpoise.
1
Introdue-tiou
to C*ar Wozic.
3
Uethads of Analysis.
5
Precipitation.
a
Elsetrol,7sis.
9
Procedure.
Discussion
10
and Data.
I
-1I
0cne I Uzct
I on s .
17
ROCOMMOU&1t
ions.
is
3 I b 1 o grap 1,,7.
20
I
1'4 arpose of tlAs thesic I, t etract t
ipurities
(iron. arsenic, ant1mowj,,phosphorus, aluzin=) that are contained
in the solution resultin
from te leaehitg of a copper ore with
a sulphuric acid olution to such an extent that they do not
effoct the onrrent
fficiency and character of deposit in the
subsequentdepositiot of te copper by lectrolysis.
This state-
ment a be modified b7 confining the elimination of Impurities
to Iron. Iron is the most troublesome im
L
puritybecause f its
corrosive action on cathode op per.
(Arzenic and antimony would
also have a orrosive atctl= on the cathode copper; but since it
Is carried downas explained later,
t
an nowbe disregarded.)
This limination is effected by the precipitation of the iron by
means of
alcium carbonate.
The one uessful
method in practice of reducing the
corrosive action of Iron Is the use of "2 as a depolarizer.
This
method is nowued 'by the largest loaching plants in th wrld,
(DowOornelia, Chile 03opper) The solution Is ran into
towers
where tba S2 is absorbed. Lhe ferric iron s red-aced to farrous
iron-, and S2 is Osorbed by the solution, and acts as a
depolarizer In the aell hse.*
of Imparitles by this
ethod.
There is-no actual precipitation
It is -necessaz7to constantly
4iseard solution to k"r the i=uritiez
*Iawrenae, -'*rans. -m. Electrochemical
Ricketts,
Trans.
A. 1. 11,%
Vol. LII.
below a point role
Soeietg.
1.
r
tbiey
2
will
nterf"Ore with electrolysis.
h
Is done by aattjmj out
a Contain =ount of Solution -after it hAs passed tmugb
t1'9
cell house, and ten pr6alpitating, the copper on serap iron.
Oho rasultinf;
copper
evolution is thrown away
has to be malted.
T
remating
In brief, it meanstt
constant oss of solution tat
cement
there is a
is hgh in aold ad an added
pense of handling and smeltW5 Oement opper.
11!
1_nt;:o4uqt12n
to
I
r ,;or_.
1.0
The solution used I r this workwas made p synthetically to correspond to the solutions that are obtained in
leaching copper ores at the Andes Copperlompany, M19, 5outh
America.
Anal7siz of solution resultingo
ore
rom leaching
t the Andes (copper onparq:
OU
R,2SO&
Totai Fe
-Al
As
Sb
40 gra= per liter
10 omms per liter
6-8 grams per liter
5-6 rams per liter
gggr=sper liter
.08 ram per liter
P,20,5
1.3 -==a per liter
Sio
.59 gram per liter
_Amlysisof sthetia
GU
'H,2SO4
Fe
FerrOUL Fe
Al
P,?05
As
"'S
13.9
6.2
0.4
olutiont
grwas per
Sr.ams per
zc,,rawper
-,= s per
liter
liter
liter
liter
3.0 E-,
rams per liter
1.2, r,,rms Tor liter
1.1 grams per liter
These substances were put Into solution in te
following mmmer:
Gapper
Iran
Al=inuM
Ar"nia,
Pbosphorus
Ca S704 W_20
PWS04M,20
A12(SW-9H20
A8203
P;205
opper
A
It
Tvss imzossible to Lot antimony nto a d1lutq HZS04
solution wlthout bmavii..',it In the formsof a complex i.rcn mith
tartaric acid.
",Inca the antimony acts 44
did ,,lot deem
advisable to attamrt I,,- Castit Into solution
tl,.e asa of tartaric
ame as arsarJc -me
acid bcause of the chance of the
tartaric acid holdine, p the Iron in precipitation.
not added because it does not effect the
Considerable difficulty
!ray.
roblem in any --
xas encountered in getting al=imum Into
solution because of Its golng In suspension.
days, the aluminum settlqd
off and stared for ue.
71.1icawas
()n standing Several
out and thq clear solution was siph=e1,,.
5
1
M'011104g
S
C2MPx.
Procipitation by alumin=.
DDissolving with
NOZand taking
it down
th Y.Cl and
R2SO4-
St=dard iodide method.
Reduce ,with al=inum.
Titrate
1vith MftO4.
Farm'sI=.
Me
analvis
suggested to s 7 the Inspiration Copper
CorVany was as follawss
1110cc. solution
,water,
in 250 cc. beWkor.
cc. oone. 142SOA. Titrate
Add 5 co. distilled
with
Wefo=d that his method as Impossible because of
the interference of te oopper. The rult
,,wre ferrous Iron than the total iron.
for ferrous iron gave
then tried the bichromate
method, 'out here again the copper interfered with tl,.e ona point.
After sveral
days of exparimentation, and as a last resort, we
preelpitated the Copperas cuprous xanthate and titrated with
biahromate solution.
ing o-ar matrix, It
fince there as nothing In literature
as necessary to ran blank tests.
oncern-
A olution
ruide up of
,Franc Ou n.--,r1.00 cc.
10 CC. of --standard 1errous
sul-bbate solution ras added. rhe solution .wasa-aldifted
5 cc. of cone. F-01.
be clopperr. wasprxipitatodwith potasslum
xanthate, and 41.-he
filtrate
-s
t1trated with bichromte.
mothodohealked,so, t.
thyl
This
plied It to our
,,withrenz=ble security.
Aluminum.
Iron oxidized with a few drops
o1O
7-ITOZ.
Iron and alumlr= hydroxide precipitated
7 e=esz
W40H
Filter,
Imite, and weigh, as Fe2O3+ A20-3.
Percentage of al=l=m dtermined by deducting
known amoumt of
e2O3:.
AxsMI&,.
Precipitate fromhot solutionrith hdrogen mphide.
Dissolve in sodium polysul-phide.
RepreC4
pitata arsenic as silver ron.
Ignite and iseigh.
" Shama.
"law filtrate
from above HpSprecipitate
and precipitate
with- ammoniummolybdate.
Reassolve in aecida=nla
Rsduce in -Tonas rducer
e13te
and titrate
*fty, Azantitative Analysis, We 75.
slution.
with Mta04.
0=sidarnble dilt'riculty,
eiicountered in maalyzin,
due to tha amphoteric character of aluminum.
Precipitate
Filtar
Cu by K
d
S203.
,Lmdreduce llodiie b7 Na2S20.3.
Filter aain.
Tilrata wth WI=
Indicator.
carbonate -7l-'.'-hethyl orange as
6
The apparatnas sed for the .,:recipitation
described as follows-. The aitating
,,rill be
chamber as a ton liter,
,narrowm=thed bottle with the bottom out off.
This was
Inverted, and -air as led Into It by means of glazz tubing
through a rber
for tho ir:
topper.
There were two serarate
one terminating In a anvaz bag flanged around a
woman's ommon mbroidery hp;
bottom of te
distribute
entrance
coutalner.
and the other at the very
The canvas bag served as a means of
te air througlicmt
t solution in flne bbbles,
and te other Fred
the neck of t1habottle.
the settlineof te precipitant at
The Inely dirided air n-- only
served as a me=s of agitation,
'but
so as -an oxidizing agent
Itor the iron.
T'he calcium carbomate used for praclpitating
the form of marble crashed to 70 mash. The
content was 4
r cent.
The filtering
Bueabner fillar
lei=
was In
aar6onate
a.
of the solution was done n a large
through filter
paper.
9
-A
1.1110
eloctrolysis
jam,
seven Ignores dp
solutionma-s alr=lated
was done in small suare
and three and one-balf
eass
nches
b means of a Poble air lift.
de
Te
Vie
anode wre lead -andthe cathodes thin strips of copper. The
size of the alectrodes ms fur t3ndone-half inabse by t=- and
one-half Inches mabnerpd.
A copper caulomtqr
az connected in
series, with a solation --onalst1w of 1000 gram of water, 150
grams of coppe
50 gmms of
5ph-ate
lcohol.
=7stals,
50 grams of cone. HZS04 ad
10
:PXqcsdur,i.
Six liters
each ran.
ol the s7nthetia solution wer tken -.
VOr
Te amant of 1mroex
neutralize the
used was 171Cared, first,
and second, to procipitate
id,
carbon-ate. The vol-ation mz aigitated fr
11marockblief addedduring the first hr
fifteen
Two lters
inutes.
o
'kphe
Aftor rigitation
the iron -as a
two ours, te
at Intervals of
he ,Evolutionwas altered.
-1L.
I'lltrate -,7aretaken for -electrolysis.
aurm-nt afficiancias
to
The
and deposits of a pure opper sulphate
Solution, an maleaned solution, and a cleans. solution, were
taken ,md ooMareed. The lectrolysis
two hours.
alachol,
as run for period
Vae athodes -sere t1hen tmken out, mashed with
dried, and treigbed.
The res-ulting ftltratas
were analyzed.
of
11
Discassio - nd Ata.
Therm=nt- of CaC% used in each ran was frst
e1gured as fllows:
Basing It apon the original analysis - al'O3fjor acid.
15.9 gmms per liter.
T42-504 CaCN
-
CaSO&+ H,20+ 002
U-2 x 00
=
14.2
rams OaC-0, rer
I
98
We added 25 gran
f
liter.
C0 I
17hiesolation Davis
agitated for to hours. Upontrying
to -1.11torIt, we ound hat It would not flter
ax-parimenting we found tt
by heating
cold. Upon
Cha solution
the precipitate coagnlatad o that V wld
flttr
to 55-60' C.,
radily.
In
All of the follo,,,winj runs -his procedure waz followed.
This 5olution was ther-aal7zed fr oopper and iron.
Copper
Iron
34.1 Sr:wm pr
liter.
3.8 grams per liter.
From theve results
we aw that more OaG03was
necessary to eliminate all of the iron.
than the ori-ginal solution.
T'hecopper was hgher
This Is undoubtedly due to
evaporation during agitation =1 water chemically combined.
Thiswas found to b the case in all of te following r=s.
,Wethen figared fr= theoretical amounts, and iclude
the *eraentar prity
of marble 54 pr
ent.
aO) the exa-at
az=nt neceszar- for the acid, 14.5 ,ramper liter.
12
This jeaves 10.1.3gmngspar liter
to precipitate 4L-Ihe
iron.
the Pollowinf,-.ealaulation.-, i-t Is
evider41;
From
Iron to-es down
Chat
as -farric aarbonate.
+-;--
2 Fe
+
CaC
N
.
Fe2 (003 3
Ca4-+
ffIere was 62 gram of iron in tho original
and .8 In the final solution.
This lavened .4 glim
olution,
tat
we"
pre-a iDi tated.
Fromthe raction
=1
o Ir= and GaMo tbe, following
4oulations are 'baead.
4.4 - x 300 = 67 grams per liter pure Ca(z.
x 55.8
which corresponds to 68 grams of marble. h, plus the 14.5
grams for the acid, givess 21.3 S=s per liter.
The difference
of .7 rams an Justify be credited to losses or praci-pitation
of alumin=.
Basing our *nl=lations
on the above discovered facts,
we added, in the following runs, On U*oretiml amount of
marble eds.
In al. probability te ferric arbonate is immediately
h7drolized to ferric Hydroxide.
Obser7ing the same conditions a
and filtration,
marbl e.
we =d
to agitation,
a ran with 35 gramsper liter
time,
of
13
Analy.Is ol' filtrate:
Co-o-
4
,.-er
35.4 rrams per
'-
Iron Total
Ferrous iron
0.91 z;ramper liter
.63 ram per liter
.Alwairmm
2 1 fgrams per "Iter
Arsenic
:05 gram per 11iter
P20.5
.20 sram per liter
A Discussion as to how tiie impurities
ome down at
tlh.is point -ight be dasirnble.
(As rgards the fom of arsenic In sol-ation
r.
Laist, in parronal commanication,said that arsenic Is in the
farm of rsenic sulrhate.)
Ths reactions as far as Iron is concerned:
(1)
702(SO4)3
3
aGO
3
+
G0(C03)3
With excess acid this beocoes:
(2)
?02(('03)3 +
4
$-
*504)Z
+
H,20+
COP.
That is until the excess acid is used up. flhau, ith
oxcoss li-ne,
ou get reaction No. (1).
The ferric
arbonate, vould then hdrolize.
Angnio.
AzZ(SO4)3 +
92(CO3)3 +
HZ-0
2
ot +
(Antimonywuld likewise blieve this way.)
CaCO3 + 02SO4
=
SQ4
HP-0 + COZ
Hso
+ z
o2
14
The elumimmwill likewise be precipitated i
t
same
ma=ar as the Iron.
Tbase equatiams may or my not be rieit,
if anyone can disruto tunNbecauz
'but vooaoubt
o a lack of knowledge on the
Subject.
In aalyzing the results obtainedIn this
,
1t mm
dafinlte17 be concludedtat thic methodof purification -will
lower the mpurities to such a point that they aan be onsidered
negligible.
By t,
request of Professor ft-vard we madeup a
solution f=1 in Iron 30 grams per lter)
mad madea rum 9=atly
as before volth the exception o-t lacreasinS the agitating time to
three hrs.
In this solutio
fOrmW. More ifflmlty
60 degrees C.
obtained.
a heavy, dense brownpecipitate
was eemmtered
ter filtering
In filtering
twice a clear filtrate
even at
was
The amo=t of marble used was figared Zr= the theoretical
value eqaired.
This amount as 100 g=s
per liter.
The solut1cm,was analyzed for Iron, =d: for cower.
010ppe'r
Iron
The rults
33. 8 gra=
2-.0 ram-
of this ran how tat
takan out of solution by the Mcipitatiou,
the copper as not
and that the Iron
-wasreduced '., a point thAt would not interfere with the
electrolysis.
I El
in obtaining the current eff icieney and ttl'ze
abaractar of te dposits,
runs were madeas stated previously.
A curran't density of six aVere
a
pr square foot was ased !:-tt
twmperature of 50 dgrees.
Th-,,fi-st solution -jas a pure copper sulphate
sol-ration
32 STams of Cu per liter,
anodes were used and
e athode
and cathodQ was two inahez.
electrolyte
as
h
R2504).
runs were 91.0 per cent. -and 89
Two lead
intance betweez anode
The -rate of circulation
7 cc. per mute.
bright, amooth, rystalline,
10 -mv
The affialleneies
per eent.
of
on two
The do-posit mas a
anti solid de-noelt.
The origizial impure solutian gave an afficlem
of
87 per cant.
ne deposit was In every rerpect similar to tho
above deposit.
rivers heck-- up airly well with What Vr. .
gives as his fndings.*
Mr. Eagle so," ttat iron below 65
grams per liter does not efect rmterlmlly te
the deposit.
nis
fficiency or
mi,&htbe explained 'ay the aluminum In the
solution atting as a diaphragm, or, n other ords, it h
regard
effect on the
crroziva tandeney of Iron,.**
The electrolysis of te fil-trate of ran Ro.
results as good as the pure ooper --alphate.
of this Is unecessary.
*Ifrana.
*1'11
Trans.
AM. MIOM. Soc.
Am. Chem. I',00.,
a
Vol.
Vol.
XLV, page 372.
MITI.-1 iddicks.
gave
Parther discussion
16
Mbeeeetrol
per
is of te solution containing
40
am$
ter of Iron gave an offlaimay of 40 pr eont. and
the dposit
was peroeptMy earroded as evidenced 17 ftrrms
*-r ;Streaks..
adw
17
Ts liesitate to give any definita Oanclusions about the
practicability of this mthod of al"aing
opper leach solutions
because of the Limited scale upon which the work was conducted
and the manypases of the subject tat
ave not been Investigated.
Rlowever',
'weare -certain, from our results,
principles of tbe subject, precipitation
tat
the two f=damontal
and 17ilterine, may be
effectively a*ao:V1ir1,-ed. To are further convinced of this by
tire fact that In the zinc leachin-g at Great Falls, Montana, at one
time, the pecipitation
of all of the iron in the zinc solution tms
accomplished by means of lime.
It is foolish for 'as to make an
attempt to arrive at the ultimate cost of the process because of"
the small knowledgeof the ultimate factors entering into the cost-,
but due to the cheapness of limerock
and its wide distribution
4q..2 a ton trough
65 mesh)
throughout te world, we are convinced
thatthe process is worthy of Investigation on a large scale.
we had started on our thesis we larned
After
that patents had been taken
out on te use of 1mernak for cleaning copper leach solutions by
Mr.'Lalst of the AnacondaCopper Oompavy. Since the ubject of
research was recommended
t us by officials
of te AnacondaCopper
Company,1mare aiting with Interest to Core
obtained.
the ramlts
18
.got knowing the details
of the-rrork Carried on t
Anaoomla, we reoomend the followine invos,-Lgations, providing
they have not baem already carried out at Anaconda.
Alkinly, e=erimentation
and practicability
n a large scale with the cost
of the apparaturs in view.
This Includes the
following$
onsiderine the amount of lim rack and the time of
(1)
agitation, we reco=end tat
a thorough investigation be arried
out to obtain '-,hebest economi*al balance bet-wean te
two.
(2
A ractical
means of agitation.
(3)
A study of the rost economical temperature to heat the
solution to in order to filter.
Bore w -mightstate tiat the
cost of this factor Is not ofgreat
Importancebecause the
solution ,vnz to be heated to 40 - 0 degroos . for lectrolysis.
(4)
An adequate and suitable means of -A"11tration. -its realize
that the precipitate Is large and bulky and tat the tne of filter
should be one having a lar,,,-e fltrating
readily washed. We recommendtt
area
nd one tat
ocrald be
the iloors type of filter,
h
as is used in the oyaniding processes for gold be investigated.
This filter
bas a large area, and it can be readily
washed. In usin,-:; our canvas bag for agitation
became stiff
and hard.
If canvas flters
a study of re-conditioning these filters.
andled and
we noticed that it
are used, we roe-ommend
19
(5) A study o-f tho Wash1ng of the nreeinitats
included copper olution,
to recover
We racorrmendhere an ivestigation
the use of limOrock to precipitate
of
the copper from the wash
,,voters as a arbonate.
(6)
'the working out of a onti=ous
process without tho
lose of any solution-or the us-9 of an additional
,W of t
rocess for
products such as the 1kindling,of' cement comer i
$02 process.
te
Webelieve that the precipitated eopper arbonate
from the wash solutions oonld be ten
with the excess limarock
and placed in the solution before it has been leaned.
Therg the
copper would be takez Into solution and the excess 11marock would
be 'used In the precipitation
of Impurities..
In no way can we
son where there would be a loss of solution in this process
We
reallse that the acidwould be neutralized In the precipitation
process, but sines te acid content at tie
point is so small,
this lose would not be of reat importance., and in comparison to
the SOZprocess, the loss perh4ps would not be greater tan tat
lost in their discard anlution.
Water ,wouldbe lost from the solution b7.evaporation,
chemically tucluded in the precipitate,
precipitate,
mhanically
included in this
loss due to Includedwater in the tailings of the leach,
and atural mchanical losses darimg the process.
Mis loss could
be made up from the wash water, so only the excess immsb ater
hare to be stripped of copper.
ould
20
Hofmanand Haymrd,
"Ketallursy of 11cpper"
Trans.
A. 1. K. E.
1914,
XLIX, 610,
7rans.
A. 1. M. E.,
1915,
LII.
Rickatts
7257,
Iforse and obleman .
Tmns. A. I. M. B., 1916, -,
Toblew==d Potter
Trans.
A. I. M. B.,
1919, LX,
Trant. Am. Bleotroahem. W.,
80,
2
191s,
mX711I, 73,
Addl oks
Trans. Am.3100troebem. Sac.,
Zern
1918,ImIll, 11,
11"Mans.
1924, -ZVO 65,
Am.
Meatrecham
O$
Eagle
mns.
Am. Electrochem. Soe.l.
19,24,
XLV,
53,
Skowronski
Private 00mmmicationwith different officials
-4=aconda Copper Company.
of the