International Journal of Mineral Proc~..in,..
6 (1980) 303-320
e ElJevier Scientific Publiahin, Company. Amsterdam Printed in The Netheriands
-
303
SELEcrIVE FLOCCULATION OF SYNTHETIC MINERAL MIXTURES
USING MODIFIED POLYMERS
G.C. SRESTY. and P. SOMASUNDARAN
Henry Krumb School of Mine.. ColumbiG Uniuersity, New Yor~. N.Y. 10021 (U.S.A.
(ReceiTed February 6, 1979; revised yersion accepted September 11, 1979)
ABSTRACT
Sreaty, G.C. and Somuundaran, P., 1980. Selective nocculation or synthetic mineral
mixtures using modified polymeR. Int. J. Miner. Procea., 6: 303-320.
The role or the presence or active groups in polymers and operating variables 8uch as
conditioning time in producing nocculation in 8ingle and mixed mineraillimes
made
or hematite, quartz and chalcopyrite is examined at diUerent conditions or pH. Selective nocculation was achieved on the basis or results obtained ror single mineral systems
as, for example, in the case of hematit.--quartz
mixtures using 8ulfonated polymer.
Flocculation was found to go through a maximum as the mineral was conditioned with
the polymer solution. lnterestin(ly,
the times of maximum nocculation for various
mineraJa were sufficiently diUerent rrom each other 10 that it could be considered as
a potential factor for achieviR( selectivity. Also, cleanin( of the selectively nocculated
product by simple redispersion in water improved the separation. Electrokinetic
studies
conducted to study the mechanisms involved provided indication ror the shift of shear
plane.
INTRODUCTION
In the caseof number of currently available ores, mineral valuesare more
finely dispersedthan in the past. Conventional beneficiation techniques are
in generalrather inefficient in the sub-sievesize rangeand hence, it has become necessaryto develop new or modified processes.Among the techniques
that are being consideredat present for ("meparticle beneficiation, selective
fiocculation appearsto be one of most promising. Ideally this should involve
aggregationof either the desired mineral speciesor the gangueparticles into
flocs leaving the others in suspension.Separation of the unflocculated material by processessuch as notation or elutriation results in the desired bene..
ficiation.
Flocculation induced by dissolvedpolymer moleculescan be attributed
to chargeneutralization and/or interparticle bridging. Selectivity in noccu.
lation requires selectiveadsorption of the polymer molecules on the desired
.Present addre8: Iff Research Institute, 10 West 35th Street, Chicago, 01. 60616 (U.S.A
304
mineral particles. A majority of the commercially availablepolymers are,
however, bulk flocculants with insufficient selectivity. In such cases,selectivity can be achievedeither by altering the interfacial potential of the
mineral to create the desired electrical interactions between the polymer
moleculesand the mineral surface or by incorporating suitable functional
groupsinto the polymer which, by formation of complexes,can make
flocculation selective.li1corporation of xanthate groups into cellulose has,
for example,enabled Attia and Kitchener (1975) to obtain selectiveflocculation of copper minerals from a copper ore. Similarly modification of
starchesfor selectiveflocculation of hematite from low-gl'adeiron ore and
useof commercial polymers containing various ionic groups for selective
flocculation of mineral mixtures have been successfullyattempted in the
past (Frommer, 1968; Usoni et aI., 1968; Read, 1972).
This paper will deal with selective flocculation of two systems:hematitequartz and chalcopyrite-1}uartz. Effects of time of conditioning with
polymer solution of flocculation behavior of minerals, and the role of cleaning the selectively flocculated product are described. Mechanismsinvolved
are discussedwith the help of the abovedata and the results obtained for
electrokinetic properties of a selectedmineral/polymer system.
EXPERIMENTAL
Natural minerals used in this study (quartz, hematite and chalcopyrite)
were obtained from WardsNatural SciencesEstablishment. Synthetic silica
(Biosil-A) used was of reagentgradepowder. Quartz and chalcopyrite were
wet ground at 50% solids in a porcelain ball mill and the hematite was
ground in steel ball mill. The minus 20 micron fractions were then separated
by wet screeningand stored in distilled water.
Commercial polymers used are listed in Table I. The hydroxypropylcellulose xanthate sample was made in the laboratory by reacting one mole of
Klucel HF with three moles of potassium hydroxide and three moles of
carbondisulfide. All the flocculants, except for starch, had an approximate
averagemolecular weight of one million.
Flocculation experiments were done in 2 cm diameter and 15 cm long
test tubes at a solid content of approximately 5%. The pH of the suspensions
was adjusted when required by addition of standard solutions of HNOJ or
KOH, and ionic stre~
by addition of KNO] solution. The flocculation responseof the minerals is expressedas the percentageof suspendedmaterials
settling into the bottom one-third volume fraction in the test tube during a
settling time of 45 sec.One-third of the mineral that will be naturally distributed in the bottom layer is excluded so that what is measuredwill correspond to that settling into the layer. The flocculation of mineral/polymer
sYstemswas studied as a function of flocculant concentration and time of
conditioning of the mineral with flocculant.
Selectiveflocculation experiments were conducted using synthetic mixtures of hematite-quartz and chalcopyrite-quartz prepared by addition
305
TABLE I
APPN)XIMATE .->rzCUtAA
~
~P'rt~
WEIGIrr
CA"I~IC
10.
~LYTB-610
..lco
~ca1
SEP~-AP
taz-r--:-t
~.
10'
30
Dow Ot881cal
POLYST'f-
Mlo.JC
Salt)
PolY8cl_~..
P«.YAca11.Ala~
f g,.2~..,+EaZ1:;:3:t
~
SOI.r<*Aft
(Sod1-
P«.Y~~
10'
M1~IC
lac.
-far zCS-C,'rO 3--]~~C
KLUaL
hrcul...
IF
Inc.
10'
COM STA-=a
Kat.ional
Starct1 and
O\~cal
~.
5000
_I~IC
e~~=~~
. .J
of equal amounts of single minerals and equilibrating the mixed fmes for
one hour. Thesetests were conducted in 4 cm diameter and 15 cm long
test tubes at 5% solids. The pulp was fIrSt conditioned with the floccculant
for 30 secand then, after allowing it to settle for 45 sec, the supernatant
(top 67% of the total volume) was siphoned out using vacuum. For the purpose of cleaning, the floc portion was rediluted to the original volume with
distilled water, conditioned for 30 sec(without further addition of flocculant) and then after 45 sec, the supernatant was again siphoned off. The
supernatant product (wash), the material initially siphoned (tailing) and
the final floc product (concentrate) were all analyzed for the iridividual
minerals.
Electrokinetic measurementswere made using a Zetameter. Towards
this purpose, a fraction of the flocculated slurry was brought to a 0.1%
solids concentration by the addition of electrolyte that resulted from centrifugation of the slurry from the ~e
test.
306
RESULTS AND DISCUSSIONS
Flocculation of single mineral suspensions
Flocculation refers to the processof aggregationinvolving interparticle
bridging (La Mer, 1964; Kane and La Mer, 1964). Ability of polymers to
brdige particles together arisespartly from the conformational properties
of the adsorbedpolymer species.Polymer moleculesare considered to ad.
sorb on mineral particles by attachment at a few sites with tangling loops
and loose segmentsprojected into the suspendingmedium (Silberberg,
1972; Eirich, 1977). Interparticle bridging follows such adsorption of
polymers either due to adsorption of theseprojected polymer segments
on uncoveredsurfacesof other particles or due to intertwining of the
projected polymer segmentsfrom different particles. As a result, individual
particles grow into three-dimensionalnetworks called flocs. Such flocculation can be expected to depend on both the structure of adsorbedpolymer
speciesand the availability of uncovered particle surface for bridging.
Time of reagentization of the mineral with polymer solution can affect
botJi of the above mentioned parametersgoverning flocculation (Botham
and Thies, 1969). Increasedreagentization can result in an increasein the
adsorption density and therefore in an increasein the fraction of surface
covered by polymer molecules.Also, a redistribution of the adsorbed
polymer segmentsamong the"suspendingmedium and particle surface can
occur at the sametime and this may lead to further increasein surface
coverageeven at constant adsorption density.
At a certain initial polymer concentration, surfacecoverageof particles
at any given time is determined by the kinetics of adsorption of the polymer
(Lipatov and Sergeeva,1972). Role of thesefactors in governing flocculation was examined for the present system 1rith the help of results obtained
for flocculation of hematite as a function of conditioning time with polymer solution. Such data for hematite/SeparanAP-30 (hydrolyzed polyacrylamide) system is given in Fig. 1 where the percentagesolids settled in 45 sec
is plotted as a function of conditioning time. Results given in this figure indicate that maximum flocculation is reachedwithin short periods of conditioning and prolonged conditioning causessome redispersionof the flocculated material. Conditioning times correspondingto maximum flocculation for the system in Fig. 1 are about 60 secat pH 7.8 and 120 sec at pH 4.
Theseresults suggestslower kinetics of adsorption of polymer and floccula.
tion at pH 4 than at pH 7.8. The active group of the polymer used in this
study wascarboxylate with a pH value of 4.7 (Aplan and Fuerstenau,1962).
Thesegroups will be in fully associatedform at pH 4 whereas,at pH 7.8,
they will be fully dissociated.Absenceof sufficient number of anionic
groups on the polymer at pH 4 can indeed causeretardation of its adsorption on the hematite particles that are positively charged.
Flocculation responseof quartz as a function of conditioning time with
SeparanAP-30 is shown in Fig. 2. Good flocculation of quartz was observed
using the anionic polymer at pH 7 where quartz is negatively changed.
307
a
w
-'
..
..
w
'"
'"
a
-'
0
'"
#
0
600
1200
1800
2400
CONOITIONINGTIME. SECONOS
Fig- 1. Percentageor hematite fines settled as a runction or time or reagentizing with
Separan AP-30; settling time, 45 sec.
0
~
..
..
w
'"
'"
0
:;
0
'"
"
0
400
800
1200
COt«>ITIONING TIME, SECONDS
Fig. 2. Percentageor quartz fines settled as a runction or time or reagentizing with
Separan AP.30; settling time, 45 sec.
308
Flocculation of negatively chargedquartz by this anionic polymer is probably due to hydrogen bonding or contamination of quartz during its grinding in poreelain mill. However, maximum in flocculation was not as sharp
in thjs cue as in the caseof hematite and conditioning time corresponding
to the maximum is at about 600 sec.The relatively slow flocculation is
probably due to the weak forees of adsorption between the anionic polymer
and similarly chargedquartz particles. The luge difference observedhere
between the optimum reagentization times for hematite and quartz suggests
the possibility of using times of conditioning of mineral with polymer solution for achievinga limited selectivity in flocculation.
Adsorption of polymer moleculeson mineral particles is governedmainly by three types of bonding, namely, electrostatic, hydrogen and covalent
bonding. The predominanceof any of the above three bonding mechanisms
over other dependson the particular mineral/polymer system and proper.
ties of the suspendingmedium. A combination of the above mechanisms
can also be operative under favourable conditions. The role of electrostatic
forees in controlling adsorption of polymers and flocculation is further
discussedin this section.
Electrostatic bonding is the predominant mechanismby which ionic
polymers can adsorb on mineral particles that are usually chargedin solutions. Polymer molecules,by adsorption on oppositely chargedparticles,
can neutralize the chargeon particle surface and decre~ the interparticle
repulsive forees that prevent aggregationof particles (Ries and Meyers,
1968). Adsorption of ionic polymers on similarly chargedparticles is not
100
.. NAl-CO\. YTE - 610
a
w
-'
..
..
w
.
SEPARAN- AP30
pH' 35 TO36
- 7.
0
::i
0
..
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H"
0
.
eo
~"CONC.,
.
120
~
~M lORY SQ..IOSIASIS)
Fi,. 3. Percentageof synthetic silica settled as a function of concentration of Nalcolyte610 and Separan AP-30; reagentizing time, 30 sec; settling time, 45 sec.
309
pOIIible if the interfacial potential is sufficiently high to introduce electrostatic repulsion. For example, results shown in Fig. 3 indicate that synthetic
silica (BiosU-A) can be flocculated with the cationic polyacrylamide,
Nalcolyte-610, but not with the anionic polyacrylamide, SeparanAP-30.
Addition of SeparanAP-30 did not result in any increasein the fraction of
silica seWedin 45 sec.Since the silica particles are highly negatively charged
in the pH rangetested, electrostatic forces can evidently be considered as
responsiblefor controlling their flocculation. It is to be noted, however,
from Fig. 4, that good flocculation of ilematite was obtained with both of
thesepolymers eventhoughanionic Separanwas slightly more effective than
cationic Nalcolyte. Figure 5 shows the flocculation responseof hematite at
various concentrations of sodium polystyrenesulfonate as a function of pH.
Anionic polystyrenesulfonate flocculates hematite better at lower pH values
where the mineral is positively chargedthan at higher pH valueswhere it is
negatively charged.
Theseresults indicate the complex nature of mechanismsinvolved in
flocculation of mineral suspensions.Though electrostatic forces are observed
to govern flocculation of some of the above systems,observednocculation
cannot be explained on the basisof electrostatic bonding alone for all cases.
For the present systems,it is suggestedthat flocculation is dependent on a
number of mechanisms,the predominance of anyone mechanismbeing
dependent on the particular mineral/polymer combination and physicochemical properties of the suspendingmedium.
0
w
...
00W
.
.
0
~
I'
0
'0
POLYMER CONC.
100
150
ao
P9M lORY S<X.IOS &ASIS'
F"". 4. Percentaceor hematite fines settled as a runction or concentration or Nalcolyte610 and Separan AP.30; reagentizing time, 30 sec; settling time, 45 sec.
310
,.
100
'.
.
,
,
15
'SQ..IOS
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.
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7
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.
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11
pM
Fig. 5. Percencace of hematite fines settled u a runction of pH and concentration
sodium polYltyrenesulronatej
reagentizing time, 30 &eCjsettling time, 45 sec.
or
Selective flocculation of aynthetic mineral mix tures
Preferential flocculation of a single or a group of mineral particulates
from a suspensioncontaining more than one mineral is referred to asselective flocculation. Successof the selectiveflocculation technique in beneficiating heterogeneousnatural ores will depend on a number of factors, some
of which include: (a) good dispersion of the fine particles in suspension;
(b) preferential adsorption of the dissolved polymer moleculeson particles
and subsequentfiocculation; and (c) effective separationof the fiocs from
the suspension.Resultsof the tests on selective flocculation of hematite
and chalcopyrite from their mixtures with quartz; and effect of the above
mentioned parameterson the separation are discussedin this section.
Hematite-quartz mixture using sodium polystyrenesulfonate
Preferential adsorption of long-chain alkyl sulfonates on iron oxide minerals is well known in flotation. Chemical aspectsof notation collectors and
polymeric flocculants are similar in severalways. Experiments were conducted to determine whether such selectivity can be obtained with sulfonate
811
a
w
..J
0-
S
..
a
~
a
#
FiC. 6. Percentageof hematite fines and quartz fines settled u a function of concentration of sodium poIysty~nesulfonate; reacentizinc time, 30 see; settling time, 45 see.
polymers in the flocculation of hematite. The flocculation responsesfor
single mineral suspensionsof hematite and quartz are shown in Fig. 6 as a
function of concentration of sodium polystyTenesulfonate.The percentage
of hematite settling in 45 sec is higher than.that for quartz and the results
suggestthat separationof hematite from quartz by $electiveflocculation
should be possibleunlessthere are strong interactions between these two
minerals.
The results obtained for selectiveflocculation tests are shown in Fig. 7.
The recovery and grade in terms of % Fel0) in the settled portion are
shown in this figure as a function of flocculant concentration. Grade of the
settled portion is observedto increasemarginally with flocculant concentration, attain a maximum and then decreasein the higher concentration
range.However, the recovery of iron oxide is found to increasesharply
with increasein flocculant concentration and reach a constant value of
about 75%. The decreasein the gradeof the settled.portion at higher flocculant conce.ltration indicates commencementof flocculation on entrapment of quartz particles in this concentration range.The settled portion
wascleanedby redispersingin water to remove the weakly flocculated
and mechanically entrained quartz particles. The gradeand recovery obtained
after one cleaning operation are also given in Fig. 7. Cleaning of the settled
portion has improved the grade with a simultaneousdecreasein reco~ery of
iron oxide.
312
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~:::~~--'1'""
:
~
~
0
;r /.f-.,?,
104
~
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,
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0
-& FeZ 0, RECOVERYIN FIRST FLOC
.0. Fez 0, RECOVERYAFTER ONE CLEANING
- ASSAY. AFTER <»IE CLEANING
.. ASSAY. FIRST FLOC
pH' 17 TO 78
I
60
I
120
1_'25
180
POLYMERCOfC.. PfIM IORYsa..m
2»-
BASIS!
Fig. 7. Recovery and grade of' the concentrate f'rom selective Oocculation of' hematitequartz mixture as a f'unction or concentration of'sodium polystyrenesulronate; reagentizing time, 30 sec; settling time, 45 sec.
In order to evaluatethe perfonnance of flocculation, and in particular,
cleaning,both gradeand recovery will have to be considered.Separation index incorporates both of thesevariablesand is defmed as "(percentage of
value mineral recoveredin the concentrate + percentageof ganguerejected
in the tailing - 100)/100". A value of either plus or minus unity for separation index refers to complete separationof the minerals and a value close
to zero refers to failure of the process.Calculatedvalues of separation index
for the results shown in Fig. 7 are given in Fig. 8. Theseresults indicate that
cleaningof the flocculated product hasimproved the separation significantly.
The importance of cleaning the flocculated slurry has beendiscussedearlier
by Friend et al. (1973) and Clausset al. (1976).
In order to elucidate the mechanismsby which such polymers act, zetapotential measurementsof hematite particles were made as a function of concentration of the flocculant. Measurementswere done under variable and
cons'c:ant
ionic strength conditions at two pH values,i.e., 7.8 where the hematite particles are negatively chargedand 4 where the hematite particles are
positively charged*. The results obtained are given in Fig. 9a, b. At pH 4, adsorption of the anionic polymer on the positively chargedhematite particles
is found to produce a decreasein the zeta potential and even make the surface negativelycharged.Tests could not be continued at pH 4 and ionic
.Point
or zero ch&fJe
pH 5 (Sresty, 1977)
ror the massive
red hematite
(95%
pure)
used in this study
is at
313
strength of 10-1 M above a polymer concentration of 100 ppm as there was
excessiveflocculation making the measurementsdifficult. Excellent flocculation was observedeven after the chargereversalof hematite particles.
Similar results were earlier obtained by Somasundaranet al. (1966) for
aggregationof alumina using sodium dodecylsulfonate.
Such chargereversalnormally suggestsspecific adsorption of the polymer
moleculesdue to forces that are non-electrical in nature. In this case,however, it is most interesting to note that polymer adsorption has also caused
a decreasein zeta potential of similarly chargedparticles at pH 7.8. Under
constant ionic strength conditions, adsorption of negatively charged molecules cannot normally be expected to make the mineral particles less
negative.The observedresults clearly suggesta significant shift in the shear
plane due to adsorption of the massivepolymer molecules. In fact, under
theseconditions, the zeta potential obtained can be considered to be a good
measureof the adsorbedpolymer layer rather than that of the original
mineral particles themselves.
314
>
2
...
~
IZ
III
l-
f
~
III
N
0
.
50
100
150
~
POLYSTYREN( SA.FONATE CONC.. PPM (MY SOLIOSBASISI
Fig. 9a. Zeta potential or hematite fines as a function or concentration of sodium polystynnesulronate, natural ionic strenlth. b. Zeta potential or hematite fines as a function
or concentration or sodium polystyrenesulfonate; ionic strenlth 10-1 M KNO3.
Hematite-quartz mixture using causticizedcorn starch
Selectivity of com starch in depressingiron oxide during anionic flotation
of silica and in selectively flocculating iron oxides are well known (Cooke
et aI., 1952; Iwasaki et aI., 1969). The selectivity of starch in depressingiron
oxides during flotation of silica from iron ores dependsto a large extent on
the functional groups present in the starch molecule (Iwasaki et al., 1969).
Chang(1952) has reported oxidized starch to produce most preferential
adsorption on hematite particles than other types.
315
Flocculation responsesof hematite and quartz fines in the presenceof
causticizedcom starch are shown in Fig. 10. Increasein settling of hematite due to flocculation is larger than that of quartz. Also. the difference
between the flocculation responseof these two minerals in the presence
of causticized com starch is greater than that in the presence of sodium
polYltyrenesulfonate suggesting better selectivity with starch than with
the latter. Results of the selectiveflocculation experiments using hematitequartz mixtures are given in Fig. 11. In this case.a satisfactory separation
index of 0.7 was in fact obtained after a one-stagecleaning of the flocculated
product.
A single stagecleaning of the flocculated product hasproduced significant
improvement in the separation index for both of tJie above mentioned systems. The effect of multiple-stagecleaning of the flocculated product on
both gradeand recovery was determined at two concentrations of starch.
Multiple-stagecleaning of the flocculated slurry produced significant im.
provement in tJie grade owing to further removal of entrained quartz. As
expected. recovery. however. decreasedduring eachstageof cleaning. The
effect of multiple-stagecleaning on the separation index obtained for selective flocculations are shown in Figs. 12 and 13. Due to tJie existence of an
apparent upper limit of grade that can be obtained in this case.improvement in separation index occurred only during the f"llStfew stagesof the
cleaning. Under theseconditions. scavergingof the tailings might be necessary to obtain economically acceptableseparationlevels.Theseresults also
100'
~
Q
w
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=:
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-
.
Q
QUARTZ
i
~ 40
pH-l.O
.. HEHATITE
pH-78
to
~
00
I
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~
STAACHC~C.
I
100
I~
PPM(MY Scx..IDSBASIS)
I
210
FiC. 10. P~tace or hematite rUlesand quartz finesMttled - . runction or concentratioa or stareh;reagentizingtime, 30 sec;settling time, 45 sec.
~
316
x
~
z
..
z
2:
..
c
c
:
..,
\II
100
200
PPM (DAY SOUOS BASIS!
STARCH
C~.
300
Fig. 11.
Separation index achieved from selective flocculation of hematite-quartz
mixture as a function of concentration of starch; reagentizing time, 30 sec; settling time, 45 sec.
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NUM8ER OF Q.EANINGS
Fig. 12. Recovery and grade or the concentrate, and separation index achieved rrom
selective flocculation or hematite-Quartz mixtures using starch as a runction or number
or cleaning stages;reagentizing time, 30 sec: settling time, 45 sec.
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Fit- 13. Reco..ry and ITade of the concentrate, and aeparation index achieved from
aelective nocculation of hematite-quutz mixture u8inc starch as a function of number
of cle.niDI stages;reacentizinc time, 30 see;settling time, 45 sec.
show that optimum amount of cleaningdependson the concentration of
polymer added. In the presentcase,use of higher ~olymer concentrations
are found to require a larger number of cleaning stages.
Chalcopyrite-quartz mixture using xanthate
Selectiveadsorption of xanthates on heavy minerals such as chalcopyrite,
galenaand sphalerite in preferenceto quartz and calcite has resulted in its
extensive use as collecton in the flotation of sulfide minerals. An ideally
selective flocculant can be made for separatingthese minerals from gangue
by incorporating the sulfi1Ydryl group into long chain polymen. Hydroxypropylcellulose supplied by Hercules,Inc., under the name "Klucel HF"
is a high-molecular weight surface-activepolymer with foaming tendency.
This polymer also possesses
a long flexible chain which can be helpful for
flocculation. Hydroxypropylcellulose xanthate was prepared by reacting
this polymer with three moles of potassium hydroxide and three moles
of carbondisulfide.
Flocculation responsesof both chalcopyrite and quartz fines as a function
of concentration of hydroxypropylcellulose xanthate at the corresponding
natural pH valuesfor thesesystemsis illustrated in Fig. 14. It is seenthat
this polymer can be effective in flocculating chalcopyrite with practically
no effect on quartz. The results obtained for the selectiveflocculation of
chalcopyrite from chalcopyri~uartz
mixture are given in Fig. 15. An
excellent separation index of 0.75 wasobtained after a one-stagecleanin~
operation.
318
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CONCLUSIONS
Flocculation of mineral suspensionsis sensitiveto many operating variablesand the effect of some of thesevariablessuch as the type of active
group present in the polymer molecules is very significant. Results obtained
in this study have indicated the existence of an optimum reagentizing time
of the mineral with the polymer solution, which was dependent on the
particular mineral/polymer system and the electrolytic properties of the suspending medium. ConPitions that permit favourable electrostatic forces
between mineral particles and polymer moleculesdo induce flocculation,
but all of the results obtained could not be explained on the basisof an
electrostatic mechanismalone.
Selectiveflocculation experiments conducted with mixed mineral systems
under conditions selectedon the basisof the results obtained for single
mineral suspensionsfurther confirms selectiveflocculation to be a feasible
process.Selectivity of the polymers towards flocculation can be improved
significantly by the incorporation of suitable functional groups into the
polymeric chains. Cleaningof the nocculated product is observedto be
essentialfor obtaining satisfactory separation.
Electrokinetic tests conducted for hematite/polystyrenesulfonate system at different pH valuesgaveindications for a shift of the shear plane.
In the caseof a polymer-coated particle, the results suggestthat the value
of the zeta potential obtained to be characteristic of the adsorbedpolymer
layer itself rather than that of the original particle.
ACKNOWLEDGEMENT
The support of the Particulate and Multiphase ProcessesProgram of the
National ScienceFoundation and the International Nickel Company is
gratefully acknowledged.
REFERENCES
Aplan, F.F. and Fuerstenau, D.W., 1962. Principles oCnon-metallic mineral flotation.
In: D.W. Fuerstenau (Editor), Froth Flotation. 50th Anniversary yolume, AIME,
p.170.
Atti.. Y.A.L and Kitchener, J.A., 1975. Dev.lopm~nt oCcompJe~ing polymers Corthe
selective flocculation oCcopper mineral.. In: M. Carta (Editor), Proc. XIth Int.
Concr. Miner. Procesa.UniYersata di Caciiari. p. 1233.
Botbam. R. and Thies. C., 1969. The efCectoCstereorecularity upon the adsorption
behavior of hiCh molecular weicht poly (iaopropylacrylate). J. Colloid Interface Sci.,
31: 1.
Chant. C.C.. 1952. Subatituted starches in amine flotation of iron ores. Trans. AlME.
199: 922.
Clau-. C.R.A, Appleton, E.A. and Vink, J.J., 1976. Flocculation or caaiterite in mi~.
tuns with quartz using a modified polyacrylamide nocculant. Int. J. Miner. Process.
3: 27.
320
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