% . , $ 1 ,141
1- I 19ff L i i3
7TT'. CL=ING OF PITTR LEA4"TT SOLUTIONS BY
T717AIV-7 OP CAMONATE.
lights thesis 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 Department of Metallurgy
by
In the Department of ectrochemistry
by
11Z1-
71--I"
We wish '.,o thanIt Pofassor Carlo R. 7ayward
for his helpful recommendations ad suzgestions for
methods of attack olt the subject.
We wioh to 46 B. B. Trsmare for his
help in olving of anal7zing solations.
We wi5h to thank i"r. Laist, 11r. L"Lton, -nd
Mr. William With, Sr., for tir recomnendation o. this subject 10br thesis .,fork.
-.4 INI . . i. Z)
Za_js of vlontoLt s,
Page Purpoise.
Introdue-tiou to C*ar Wozic.
Uethads of Analysis.
Precipitation.
Elsetrol,7sis.
Procedure.
Discussion and Data.
0 c ne I Uzct I o n s . ROCOMMOU&1t ions. 1 3 5 a 9 10 -1 II 17
is
3 I b 1 o grap 1,,7. 201'4 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
subsequent depositiot 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 down as explained later, t an now be 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 now ued 'by the largest loaching plants in th wrld,
(Dow Oornelia, 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.* There is-no actual precipitation of Imparitles by this ethod. It is -necessaz7 to constantly 4iseard solution to k"r the i=uritiez below a point role tbiey
*Iawrenae, -'*rans. -m. Electrochemical Soeietg. 1. r
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; evolution is thrown away T remating cement
copper has to be malted. In brief, it means tt there is a
constant oss of solution tat is hgh in aold ad an added
1_nt;:o4uqt12n to r ,;or_.
I 1.0
The solution used I r this workwas made p syntheti-cally to correspond to the solutions that are obtained in
leaching copper ores at the Andes Copper lompany, M19, 5outh
America.
Anal7siz of solution resultingo rom leaching opper ore t the Andes (copper onparq:
OU R,2SO& Totai Fe -Al As Sb P,20,5 Sio
40 gra= per liter
10 omms per liter 6-8 grams per liter
5-6 rams per liter
gggr=s per liter
.08 ram per liter
1.3 -==a per liter
.59 gram per liter
_Amlysis of sthetia olutiont
GU 'H,2SO4 Fe FerrOUL Fe Al P,?05 As
"'S grwas per liter 13.9 S r. ams per liter
6.2 zc,,raw per liter 0.4 -, = s per liter
3.0 E-, rams per liter 1.2, r,,rm s 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_- 2 0 PWS04M,20 A12(SW-9H20 A8203 P;205
A
It Tvss imz ossible to Lot antimony nto a d1lutq HZS04 solution wlthout bmavii..', it In the forms of a complex i.rcn mith
tartaric acid. ",Inca the antimony acts 44 ame as arsarJc -me did ,,lot deem advisable to attamrt I,,- Cast it Into solution
tl,.e asa of tartaric acid bcause of the chance of the
tartaric acid holdine, p the Iron in precipitation. 71.1ica was
not added because it does not effect the roblem in any --!ray. Considerable difficulty xas encountered in getting al=imum Into solution because of Its golng In suspension. ()n standing Several days, the aluminum settlqd out and thq clear solution was siph=e1,,. off and stared for ue.
1 S M'011104g
C2MPx.
Procipitation by alumin=.
DDissolving with NOZ and taking it down th Y.Cl and
R2SO4-St=dard iodide method.
Reduce ,with al=inum. Titrate 1vith MftO4.
Farm's
I=.
Me analvis suggested to s 7 the Inspiration Copper
CorVany was as follawss
1110 cc. solution in 250 cc. beWkor. Add 5 co. distilled ,water, cc. oone. 142SOA. Titrate with
We fo=d that his method as Impossible because of the interference of te oopper. The rult for ferrous iron gave ,,wre ferrous Iron than the total iron. 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 Copper as cuprous xanthate and titrated with
biahromate solution. fince there as nothing In literature oncern-ing o-ar matrix, It as necessary to ran blank tests. A olution
ruide up of ,Franc Ou n.--,r 1.00 cc. 10 CC. of --standard 1errous
sul-bbate solution ras added. rhe solution .was a-aldifted
5 cc. of cone. F-01. be clopperr. wasprxipitatodwith potasslum thyl
xanthate, and 41.-he filtrate -s t1trated with bichromte. This mothod ohealked, so, t. plied It to our
,,with renz=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 from hot solutionrith hdrogen mphide. Dissolve in sodium polysul-phide.
RepreC4 pitata arsenic as silver ron.
Ignite and iseigh.
" Shama.
"law filtrate from above HpS precipitate and precipitate with- ammonium molybdate.
Reassolve in aecid a=nla e13te slution.
Rsduce in -Tonas rducer and titrate with Mta04.
due to tha amphoteric character of aluminum.
Precipitate Cu by K d S203.
Filtar ,Lmd reduce llodiie b7 Na2S20.3.
Filter aain.
Tilrata wth WI= carbonate -7l-'.'-h ethyl orange as
The apparatnas sed for the .,:recipitation ,,rill be described as follows-. The aitating chamber as a ton liter,
,narrow m=thed bottle with the bottom out off. This was
Inverted, and -air as led Into It by means of glazz tubing
through a rber topper. There were two serarate entrance
for tho ir: one terminating In a anvaz bag flanged around a
woman's ommon mbroidery hp; and the other at the very bottom of te coutalner. The canvas bag served as a means of
distribute te air througlicmt
t
solution in flne bbbles,
and te other Fred
the settlineof te precipitant at
the neck of t1ha bottle. 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 was In the form of marble crashed to 70 mash. The lei= aar6onate
content was 4 r cent. a.
The filtering of the solution was done n a large Bueabner fillar through filter paper.
-A
1.1110 eloctrolysis was done in small suare eass
jam, seven Ignores dp and three and one-balf nches de Te
solutionma-s alr=lated b means of a Poble air lift. Vie anode wre lead -and the cathodes thin strips of copper. The
size of the alectrodes ms fur t3nd one-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 5ph-ate =7stals, 50 grams of cone. HZS04 ad
10 :PXqcsdur,i.
Six liters ol the s7nthetia solution wer tken -.VOr each ran. Te amant of 1mroex used was 171Cared, first, to
neutralize the id, and second, to procipitate the iron -as a
carbon-ate. The vol-ation mz aigitated fr two ours, te
11marock blief added during the first hr at Intervals of
fifteen inutes. Aftor rigitation he ,Evolution was -1L. altered.
Two lters o 'kphe I'lltrate -,7are taken for -electrolysis. The
aurm-nt afficiancias and deposits of a pure opper sulphate Solution, an maleaned solution, and a cleans. solution, were
taken ,md ooMareed. The lectrolysis as run for period of
two hours. Vae athodes -sere t1hen tmken out, mashed with
alachol, dried, and treigbed.
Discassio - nd Ata.
Ther m=nt- of CaC% used in each ran was frst e1gured as fllows:
Basing It apon the original analysis - al'O3fj
15.9 gmms per liter.
T42-504 CaCN - CaSO& + H,20 + 002
U-2 x 00 = 14.2 rams OaC-0, rer liter.
or acid.
I
98
We added 25 gran f C0 I
17hie solation Davis agitated for to hours. Upon trying
to -1.11tor It, we ound hat It would not flter cold. Upon
ax-parimenting we found tt by heating Cha solution to 55-60' C.,
the precipitate coagnlatad o that V wld flttr radily. In
All of the follo,,,winj runs -his procedure waz followed.
This 5olution was ther- aal7zed fr oopper and iron.
Copper 34.1 Sr:wm pr liter.
Iron 3.8 grams per liter.
From theve results we aw that more OaG03 was
necessary to eliminate all of the iron. T'he copper was hgher
than the ori-ginal solution. 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.
,We then figared fr= theoretical amounts, and iclude the *eraentar prity of marble 54 pr ent. aO) the exa-at
12
This jeaves 10.1.3 gmngs par liter to precipitate 4L-Ihe iron. From
the Pollowinf,-. ealaulation.-, i-t Is evider41; Chat Iron to-es down
as -farric aarbonate.
+-;-- N . Fe2 (003 3 Ca4-+ 2 Fe + CaC
ffIere was 62 gram of iron in tho original olution,
and .8 In the final solution. This lavened .4 glim tat we"
pre-a iDi tated.
From the raction o Ir= and GaMo tbe, following
=1 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 to agitation, time,
and filtration, we =d a ran with 35 grams per liter of
Analy.Is ol' filtrate:
Co-o- 4
,.-er 35.4 rrams per
'-Iron Total 0.91 z;ram per liter Ferrous iron .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 + Hso + z o2
(Antimony wuld likewise blieve this way.)
14
The elumimm will likewise be precipitated i t same
ma=ar as the Iron.
Tbase equatiams may or my not be rieit, 'but voo aoubt if anyone can disruto tunNbecauz o a lack of knowledge on the Subject.
In aalyzing the results obtained In this
,
1t mmdafinlte17 be concluded tat thic method of purification -will
lower the mpurities to such a point that they aan be onsidered
negligible.
By t, request of Professor ft-vard we made up a
solution f=1 in Iron 30 grams per lter) mad made a rum 9=atly as before volth the exception o-t lacreasinS the agitating time to three hrs. In this solutio a heavy, dense brown pecipitate
fOrmW. More ifflmlty was eemmtered In filtering even at
60 degrees C. ter filtering twice a clear filtrate was
obtained. 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 33. 8 gra=
Iron 2-.0
ram-The rults of this ran how tat the copper as not takan out of solution by the Mcipitatiou, and that the Iron -was reduced '., a point thAt would not interfere with the
in obtaining the current eff icieney and ttl'ze
abaractar of te dposits, runs were made as stated previously. A curran't density of six aVere pr square foot was ased !:-tt a twmperature of 50 dgrees.
Th-,, fi-st solution -jas a pure copper sulphate
sol-ration 32 STams of Cu per liter, 10 -mv R2504). Two lead
anodes were used and e athode h intance betweez anode and cathodQ was two inahez. The -rate of circulation of
electrolyte as 7 cc. per mute. The affialleneies on two runs were 91.0 per cent. -and 89 per eent. The do-posit mas a bright, amooth, rystalline, 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 fficiency or
the deposit. nis mi,&ht be explained 'ay the aluminum In the
solution atting as a diaphragm, or, n other ords, it h a
regard effect on the crroziva tandeney of Iron,.**
The electrolysis of te fil-trate of ran Ro. gave
results as good as the pure ooper --alphate. Parther discussion
of this Is unecessary.
*Ifrana. AM. MIOM. Soc. Vol. XLV, page 372.
*1'11 -1 iddicks.
adw
16
Mbe eeetrol is of te solution containing 40 am$
per ter of Iron gave an offlaimay of 40 pr eont. and
the dposit was peroeptMy earroded as evidenced 17 ftrrms
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 many pases of the subject tat ave not been Investigated. Rlowever', 'we are -certain, from our results, tat the two f=damontal principles of tbe subject, precipitation 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 knowledge of the ultimate factors entering into the cost-,
but due to the cheapness of limerock 4q..2 a ton trough 65 mesh) and its wide distribution throughout te world, we are convinced
thatthe process is worthy of Investigation on a large scale. After
we had started on our thesis we larned that patents had been taken
out on te use of 1mernak for cleaning copper leach solutions by Mr.'Lalst of the Anaconda Copper Oompavy. Since the ubject of research was recommended t us by officials of te Anaconda Copper Company, 1m are aiting with Interest to Core the ramlts
.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 n a large scale with the cost
and practicability of the apparaturs in view. This Includes the
following$
(1) onsiderine the amount of lim rack and the time of
agitation, we reco=end tat a thorough investigation be arried
out to obtain '-,he best 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 -might state tiat the cost of this factor Is not ofgreat Importance because 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 area nd one tat ocrald be readily washed. We recommend tt 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 andled and washed. In usin,-:; our canvas bag for agitation we noticed that it became stiff and hard. If canvas flters are used, we roe-ommend
a study of re-conditioning these filters.
(5) A study o-f tho Wash1ng of the nreeinitats to recover included copper olution, We racorrmend here an ivestigation of the use of limOrock to precipitate 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 rocess for ,W of t products such as the 1kindling, of' cement comer i te
$02 process. We believe that the precipitated eopper arbonate from the wash solutions oonld be ten with the excess limarock and placed in the solution before it has been leaned. Therg the
copper would be takez Into solution and the excess 11marock would be 'used In the precipitation of Impurities.. In no way can we
son where there would be a loss of solution in this process We reallse that the acidwould be neutralized In the precipitation process, but sines te acid content at tie point is so small, this lose would not be of reat importance., and in comparison to
the SOZ process, the loss perh4ps would not be greater tan tat
lost in their discard anlution.
Water ,would be lost from the solution b7.evaporation,
chemically tucluded in the precipitate, mhanically included in this precipitate, loss due to Includedwater in the tailings of the leach, and atural mchanical losses darimg the process. Mis loss could
be made up from the wash water, so only the excess immsb ater ould
Hofman and Haymrd,
"Ketallursy of 11cpper"
Trans. A. 1. K. E. 1914, XLIX, 610,
Rickatts
7rans. A. 1. M. E., 1915, LII. 7257,
Iforse and obleman .
Tmns. A. I. M. B., 1916, -, 80,
Toblew=
=d Potter
Trans. A. I. M. B., 1919, LX, 2
20
Trant. Am. Bleotroahem. W.,
Addl oks
Trans. Am. 3100troebem. Sac., Zern
11"Mans. Am. Meatrecham O$
Eagle
mns. Am. Electrochem. Soe.l.
Skowronski
191s, mX711I, 73,
1918, ImIll, 11,
1924, -ZVO 65,
19,24, XLV, 53,
Private 00mmmication with different officials of the
