~ r~ .- I: ~: CHAPTER P. SOMASUNOARAN K. P. ANANTHAPAOMANABHAN Henry Krumb School of Mines Columbia University New York, New York 16.1 INTRODUCTION Flotation processes are useful for die separation of a variety of species ranging from molecularand ionic 10 microorganisms and mineral fi~ from one aIIO(bct" for !be pll1KJ5e of extractionof valuable products aswell as cleaningof WaSfewalelS. They ~ particularly attlaclive for sepal2tion problems involving very dilute solutions where most oIfICrprocesses usually fail. The success of ft«ation processes is dependent ... primarilyon die 1e1KIerw:;y of surface-active species to conce.-nae81 dte water-fluid interfaceand 00 dleir capability to make selected noo-surface-active materialshydrophobic by means of adsorption on them or association with them. Under practical conditions, the amoumof imcrfacial areaavailable for such con- centration is incrQsed by &eftCraling air bubbles or oil ~ in dte ~ solution. A classification of fttXation processes based 00 die ~hanism of separation and die sizeof die materiaIthat is being separated is given in Table 16.1-1.,.2Thus. separatioo of surface-active species such as detergents from 8IpIeOU5 solution is koown as foam fractionation while that of noo-surface-active speciessuch as ffiCn:ury and IJIIOSpIIaIcs that can be compIexcdwith various surfactants is called molecular flotation or ion notation. Theseparations of surface-active and noo-surface-active subsieve sizecoUoids ~ known as foam flotation and micronotation.respectively. F~ ft<Mation is usedcu~y for !he separation of subsieve size panic- uIatcs preaggregatcd by various means to die sieve-siu range(ClevelandCliff Co.). Thesecan be called aggregate notation. Separation of subsieve-size paniculates has been attemptedby a number of od1er Icchniqucs using fine bubbles generated by a variety of means or by using oil as die hydrophobicmedium. A brief descriptiooof various Rotationprocesses is given below. It is to be noted that, althoughf~ ftOfation of ores is dte only process that hasbeenusedinckIstrially ~ a lafIe scale, other notation aechniques have cons:IdcnbIe ~ential for treating dilute solutions and ~ustrial wastes.Examples of potential areas for large-scale application include treatment of primary and secondary sewage efftuents. acid mine drainage,laundry waste, and wastes of textile, paper,leather,dying, printing, and meat ~ing indUstries. 16.2 FLOTATION TECHNIQUES 16.2-1 Froth Flotation In froth Rotation.fi~t a p'lp of crushed and ground particlesin water is conditionedwith desiredflotation ~agents including pH modifien and surfactants. Then it is agitatedin a cell, 1$ Jhown schematically in
CHAPTER
P. SOMASUNOARAN K. P. ANANTHAPAOMANABHAN Henry Krumb School of
Mines Columbia University New York, New York
16.1 INTRODUCTION
Flotation processes are useful for die separation of a variety of
species ranging from molecular and ionic 10 microorganisms and
mineral fi~ from one aIIO(bct" for !be pll1KJ5e of extraction of
valuable products as well as cleaning of WaSfewalelS. They ~
particularly attlaclive for sepal2tion problems involving very
dilute solutions where most oIfICr processes usually fail. The
success of ft«ation processes is dependent
... primarily on die 1e1KIerw:;y of surface-active species to
conce.-nae 81 dte water-fluid interface and 00 dleir capability to
make selected noo-surface-active materials hydrophobic by means of
adsorption on them or association with them. Under practical
conditions, the amoum of imcrfacial area available for such con-
centration is incrQsed by &eftCraling air bubbles or oil ~ in
dte ~ solution. A classification of fttXation processes based 00
die ~hanism of separation and die size of die materiaIthat is being
separated is given in Table 16.1-1.,.2 Thus. separatioo of
surface-active species such as detergents from 8IpIeOU5 solution is
koown as foam fractionation while that of noo-surface-active
species such as ffiCn:ury and IJIIOSpIIaIcs that can be compIexcd
with various surfactants is called molecular flotation or ion
notation. The separations of surface-active and noo-surface-active
subsieve size coUoids ~ known as foam flotation and micronotation.
respectively. F~ ft<Mation is used cu~y for !he separation of
subsieve size panic- uIatcs preaggregatcd by various means to die
sieve-siu range (Cleveland Cliff Co.). These can be called
aggregate notation. Separation of subsieve-size paniculates has
been attempted by a number of od1er Icchniqucs using fine bubbles
generated by a variety of means or by using oil as die hydrophobic
medium. A brief descriptioo of various Rotation processes is given
below.
It is to be noted that, although f~ ftOfation of ores is dte only
process that has been used inckIstrially ~ a lafIe scale, other
notation aechniques have cons:IdcnbIe ~ential for treating dilute
solutions and ~ustrial wastes. Examples of potential areas for
large-scale application include treatment of primary and secondary
sewage efftuents. acid mine drainage, laundry waste, and wastes of
textile, paper, leather, dying, printing, and meat ~ing
indUstries.
16.2 FLOTATION TECHNIQUES
16.2-1 Froth Flotation
In froth Rotation. fi~t a p'lp of crushed and ground particles in
water is conditioned with desired flotation
~
776 P. Somasundaran and K. P. Ananthapadmanabhan BI
TABLE 16.1-1 Flotation Techniques Classified on the Basis of
Mechanism of Separation and Size of Material Separated
Nalurdl surface
Ion flotation, molecular flOfation, adsorbing colloid flotation:
for example, Sr2+, Pb2+, Hg2+, cyanides
Foam flotation: for example. microorganisms, proteins
In association with sulface- active agents
Microftotation, colloid flotation, ultraftotation: for example,
particulates in wastewater, clay, microorganisms
Source: Reprinted from SeparatiQlt and PurijicaliQII Methods,
Courtesy of Man:d Dekker, Inc.
Fig. 16.2-1. in the presence of air that is sucked or fed into the
impeller zone where the air is well dispersed owing to the intense
agitation in that zone. The air bubbles collide with particles and
are attached to those that are hydrophobic or have acquired
hydrophobicity. The bubble-particle aggregates rise to the top of
the cell and are removed by skimming. Various types of machine that
are used by the industry have been described in detail by Hams in a
recent publication on flotation. I
Two cells used in ~ laboratory for studying the physical chemistry
of flotation process are the Hal- limond cell and Fuerstenau
cell!') Tests can be conducted in these cells under controlled
chemical con- ditions. Tests in a Hallimond tube cell, shown
schematically in Fig. 16.2-2. require only about I g of the mineral
and do not require the use of a frother. Rigorous control of
flotation time, gas flow. and agitation that have been made
possible by recent modifications enable one to conduct tests with a
reproducibility of :t 1%. Also. application of the results obtained
using the HaUimond tube cell has been demonstrated recently by
correlating such results with those obtained using conventional
laboratory large-scale cells.'
16.2-2 Fine Bubbles Flotation
~
~.
~ ~~: ~ ~ ~'t; ~,
8IXi in die enriching nkJde part of die foamale is ~cled to die lop
of die ftor.rion column for ~ftuxing 8I:tM3n .
16.2-] Foam Fractionation
Foam fmctionation involves the removal of nanually surface-active
species by aegtjon at low ftow rates in the absence of any
agitation. This Ied8Ii'PIe is ~larty useful for die _aI of highly
surface- 8;tive contaminants from surfactants used for basic
surfaces and colloid dtemistry reseaICh walt.
16.2-4 Foam Flot~tion
,
The a)x)ve ftoWioo when conducted r« microscopic size species dlat
are naturally wtface active is called roam ftotation. It has been
used under laboratory conditions ror the ~moval or miclOOlJanisms.
dyes, alx!
10 00.
~
16.2-5 Ion Flotation
Ion flotation involves separation of ions capable of association
with a surfactant from other ions, molecular matter, or waste
material from aqueous solutions. In this case, equimolar amounts of
surface-active agents often are needed, making it less attractive
as a process for recovering valuable products.
16.2-6 Precipitate Flotation (
I
F
c
51
Ions also can be removed fim by precipitating them by changing the
pH or by bubbling. for example. hydrogen sulfide in the case of
copper. andlhen by providing appropriate surface-active agents that
can adsorb selectively on the surface of the precipitate to make it
hydrophobic. This process, known as pre- cipitate flotation. has to
be conducted under nonturbulent conditions. because the
precipitates usually are colloidal and bulky in nature. An
interesting variation of the technique, called precipitate
flotation of the second kind.6 involves precipitation of the
species with an organic reagent so that the resulting precipitate
is naturally hydrophobic and can be floated without the help of any
additional reagents. Examples of this include flotation of nickel
with dirnethylglyoxime!.1
16.2-7 Microflotation
tt ir
Rotation of colloidal-size colligends with the aid of surfactants
under mild agitation and aeration conditions is called
microflOCation. This technique has been used recently under labo~
conditions for removal of clays and other colloidal mailer from
wastewater effluents. It is to be ~ed that the term microflotation
also is used by those working on mineral flotation chemistry to
froth flotatioo conducted in the laboratory with 1-10 g of mineral
feed.
16.2-8 Pressure Release and Vacuum Flotation
1Conventional froth flotation using cells such as that shown in
Fig. 16.2-1 usually fail in processing micron- size particles. A
basic handicap of the conventional operation is its inability to
control the size of bubbles Examples of techniques in which fine
bubbles are generated include pressure release flotation and vacuum
flotation. Pressure release flotation consists of release of gas
predissolved in the pulp under pressure, whereas vacuum flotation
involves release of gas nonnally present in the pulp by application
of vacuum. In either case, numerous microbubbles are generated on
tbe hydrophobic particles causing tfleir levitation. Generation of
bubbles preferentially on hydrophobic sites can produce enhanced
selectivity. The air pockets in crevices and pores also can act as
nucleation sites for the bubbles; this of course can be
detrimental.
16.2-9 Electroflotation
1 0 d . b t l f
Bubbles that a~ extremely fine and homogeneous in size can be
produced by electrolysis of water using electrodes of a given
design. Rotation using such bubbles has been used ~jIoI1edly in
Russia in variou~ industries. An attractive featu~ of this
technique is that the bubbles resist Coalescence, possibly because
of similar charges on the bubble. It has potential for operation
ill combination with the conventional flotation (where extemal air
is used) for treating ores containing panicles in all size
ranges.
Vacuum, pressure release, and electroftotation can be used to
remove a variety of materials such as oils, fats, heavy metals, and
other suspended solids from municipal or industrial waste.9
16.2-10 Oil Flotation
Thc flotation processes using oil-water interface for collection of
panicles are emulsion Rotation al. t liquid- liquid flotation. In
the former the reagentized panicles are collected by oil-water
emulsion droplets and by aeration of the system. whereas in the
latter removal of the panicles collected at the interface is
achieved mostly by phase separation. The only cornmen:ial use of
emulsion flotation, to our knowledge, is that of the separation of
apatite from iron ore at LKAB, Malmberget, Sweden.
16.2-11 Aggregate Flotation
Conventional flotation processes can be made applicable to the
treatment of fines simply by preaggregating tbem among themselves
or with another carrier material. Techniques in this category
include floccflotatlon, carrier flotation (ultraflotation), and
spherical agglomeration.
FlOCCFlOTATION A technology with enormous potential in the mineral
processing area is selective flocculation accompanied by flotation.
Such a process already has become commen;ial for the separation of
iron minerals from lo.w- gl'ade iron ore.10 In this case stan:h is
used as flocculanl for iron oxide and quanz is floated using
amine
..:..l:
Bubble and foam Separations-Ore fkJtation 779
as the collector. Flocculation also can be achieved by the
adsorption of polyelectrolytes or ionic species. Past IatKJnIory
wort on selective lIocculation deab mostly with binary minetal
systems in which the valuable mi~raI was a metal sulfide (galena.
pyrite, or sphalerite)'I-ls or a metal or its oxide (hematite.
chromite. inMI. and titanium),s-il and the odIer ~ was a g~
mineral. RePOfts of sepaI31ion by selective IIocculation on
multicompo~nt natural ~ itself are scant. One noteworthy attempt in
this regard is that by Carta et aI.'9 for the be~ficia,ion of
uhrafi~ lluorite from latium.
CARRIER FlOTATK>N (UlTRAflOTATK>N) In this technique. known
also as piggyback ftotation. a carrier material is used for
ftoafing the fine particles. For example. anacase is leDM)Ved on a
comrnen:iaI scale from clay for use in the paper iIMiuSUy by using
calcile as dae carrier. While anatase does not ftoat by itself. it
is coftoated with a coarse auxiliary mineral such as cakite.
An analogous process is one called adsorbing colloid ftotation in
which the colligend is adsorbed on a colloid thai can be ftoated
using various microftotation lccbnicpJes.zo
SPHERICAL AGGLOMERATION FiDeS ~ tumbled in this case in an IqIJeOUS
solution COIIIaiaing an invniscible Iiquic! whidl fOrD1S capillary
bridges betwcea ~ ~1es and causes dleir~. Si~ Si(x:k's original
observation of this phenomenon in 19.52 with barium sulfate ~CaIes
in benzene. containing a small amount of water. it has been
examined maialy by Puddington and ~ for ~Iometation of graphite.
chalk, zinc sulfide. coal, iron ore, and tin ore suspensions in
aqueous solutions. I Also, Farnard ct aI.!! have claimed
good scparation of eacla COII1p)IICnt from a rnixture or li8C
sulfide, calcium carlJonate. and graphite in water with
nitrobenzene as binding liquid by stepwise agglomeration.
Physicochemical principles governing the varOis tIocMjon processes
~ essentially Mientical. even dKlUgh there can be significant
dilferences in the actual mechanics used in their application.
Basic principles involved in Rotation ~ discussed below with
appropn.te examples.
16.3 PHYSICOCHEMICAL PRINCIPLES
!i The success of selective Rotation depends primarily 00 the
diffele1K:CS in the hydrophobicity of the species or particles that
ale co be ftO8Icd. Excepc for a smaU flacliOll, colligends a~
generally hydropitilic and the~fo~, to impart hydrophobicitY,
surfactants thac seleclively will associate with or adsorb on them
ale 8IkIed to the syllem. Thcsc aarfxunts, gencta1ly called
coUectors, have at least ~ polar head and ~ hydropitobic tail in
their RM)1ccular sllUCtu~. CollectOf$ adsolb on minerals with their
hydrophobic tail tIImcd toward the bulk~. rhcreby making rhc
minerals hydrophobtc- Typica1 examples of colieclors ~ in praccice
include Iong-<:hain amines for quartz, potash, and anionic
complc~cs such as fem>cyanide alKl sbort<hain xandIatcs for
base mcta1 sulfides.
In the recent past, a number of e~cellent ~vicws and boob have
appca~ on the physicochemical aspects of Rotation. 1-6 Only a brief
ovcrvicw of the n-=dIaIIistjc 8SpccU ~ included he~ arK! for
~
details ~rs should coosuh the above ~fele1K:CS. The association or
adsoqltioo of surfactants with the colli&end ~ occurs due to
vari<XIs interactive
fortes, opefaIing iOOivilklally or in COIOOinalion with"each dher.
Major forces rhat can contribule to the adsorption arise from
elcctroSlatic attraction, covalent bonding, hydrogen bolKling, van
dcr Waals cohesive interaction among the adIOIbatc species, arK!
solvalion or desoJvation of adsoIbate or adsorbent species in the
interfacial region. The concentration c" in kmoI/m}, of coonterions
in the interfacial ~gion can be given on the basis of the BoltzmaM
distribution function as
( -4G;-S )c. - C. exp -.r--
~;
(16.J.I)
when c. is the concentration in bulk and 40.-s is die f~-eae1JY
change involved in the transfer of surfactants from the bulk to the
surface of the colligend. Equation (16.3-1) can be rewritten in
tenns of adsorption density r, by multiplying the right-hand side
by the thickness T of the adsorbed layer:
P. Somasundaran and K. P. Ananthapadmanabhan780
AG~ = AG + AG:.,. + AG..-c + AG:. + AGH + 4G:"v (16.3-3)
AG is the tenD that arises from the electrostatic interaction
between ionic species and the charged colligend; similarly, AG:.,.
is due to any covalent bonding that leads to chemisorption; 4G..-c
is due to the cohesive chain-chain interaction between sunactant
species upon adsorption; 4G..., is the nonpolar inter- action
between the chain and the solid substrate; 4GH is the term due to
hydrogen bonding; and AG:,.v is the result of solvation or
desolvation of any species owing to the adsorption process. For
each system. one or more of the above terms ~an be contributing,
depending on the type of the colligend, sunactant. and other
chemical species in the system, concentration of the sunactant, pH,
temperatUre, ionic strength, and so on. Thus, for adsorption of
alkyl sulfates on nonmetallic minerals such as qualtz,
electrostatic and lateral chain-chain interaction forces are
considered to playa governing role, whereas for adsorption of
xanthates on sulfides, the covalent forces are considered to be
predominant.
16.3-1 Electrostatic Forces
Electrostatic properties of the solid surfaces generally result
eithec from the preferential dissolution of the lattice ions. as in
the case of silver iodide, or from the hydrolysis of the surfaces
followed by the pH- dependent dissociation of the surface hydroxyls
as in the case of silica: 7
Of(-
-M(HzO)~ ~ -MOH- ~ -MQ-- + HzO
The sign and magnitude of the electrical field is detennined
primarily by the concentration of positive and negative (surface)
potential-detennining ions. Lattice ions ~ coo~ to be
potential.{jetennining ions for Agl-type solids and H" and OH- are
the conesponding ions for o~ide minerals. For salt-type minerals
such as calcite and apatite. both of the above mechanisms can be
operative since their lattice ions can undergo preferential
dissolution as well as hydrolysis reactions with H" and OR-. In
such cases. H+. OR-. and all charged comple~es that are the result
of the hydrolysis reactions can playa major role in detennining the
surface potential. Even for the o~ide minerals such as silica. it
will be more accurate to consider dissolved hydrolyzed species as
potential detennining. since these minerals do have finite solu-
bilities that can amount to significant levels. Silicate minerals.
with layeJect structures. possess a net negative charge under most
natural conditions due to substitutions, for e~. AI)" for Si'" and
Mg2+ for AP"
in the structu~. The surface potential +0 for the above minerals is
given by
RT (Q+ ) RT (Q- )'to - z:Fla ~ -uta F (16.3-4)
where F is the FaJaday constant and a+ and a- are activiti~ of the
positive and negative potential- determining ions with valencies Z.
and Z- (inclusive of sign); a~ and aJ'!'C are activities under
conditions of zero diarge of the particle surface. Such i condition
of zero charge is called the point of zero charge (PZC). Particles
will carry a positive charge below the PZC. represented in lenDS of
the negative of the logarithm of the positive porentiaI-determining
ions. and negatively charged above it. Since the system as a whole
must be electrically neutral. there should be an equivalent amount
of ions in the interfacial region. called counterions, with charge
opposite to that of the particle surface. A schematic diagram of
the resultant diffuse soluble layer is given in Fig. 16.3-1.
For oxides and salt-type materials. adsorption of both organic and
illO~anic flotation reagents are often the result of electrostatic
attraction between the solid and the reagent. The PZC of the solid
is an important characteristic property in such cases and can be
determined easily by experiment. Typical PZC values of some common
minerals are given in Table 16.3-1. It is to be noted that the PZC
of the minerals has been shown. using zeta potential. (potential of
the shear region) measurements. to be affected significantly by
various factors such as pretreatment of the solid. extent of aging.
storing. as well as the pH and even the
ionic strength of the solution in which it is stored.4S.6I-1O It
has been shown recently that the commonly used cleaning procedures
such as leaching in acidic and
hot solutions can affect drastically both the sign and magnitude of
the experimentally measured paramet~rs such as the zeta potential.
71.72 In addition to the above mentioned variables. surface
chemical heterogeneIty of the.rrticles also can contribute
significantly to the range of PZC values that can be obtained for a
given
solid.7 An interesting study. in this regard. by Kulkarni and
Somasundaran73 involved the analysis of vario.us
spots on a typical hematite particle using scanning electron
microscopy. energy dispersive X-ray anal~sls- and Auger
spectroscopic techniques. Figure 16.3-2 shows the electron
micrograph of a hematite partIcle. Spots E. G. and H shown in the
figure were analyzed and the results showed a very high percentage
of sifica at spots F and G whereas spot H showed almost JXlre
hematile. For this particular sample, whereas the bulk: analysis
indicated a silica content of 4 %, surface analysis using the Auger
technique gave a value
as high as 50% for the silica content. The presence of such large
amounts of silica on the surface will dec~ the PZC of the hematite
to lower pH values. It is to be noted that, because of the presence
of positive hematite regions on the mineral, the adsorption of
anionic surfactants still can take place above the net PZC of the
sample. In fact, results from the litemture (see Fig. 16.3-3)
indicate the adsorption of anionic surfactants above the net PZC of
hematite!4.1s In such cases, the observed adsorption could be due
to the surface chemical heterogeneities mther than any
chemisorption of the collector as speculated in the past!4.1S In
addition, chemical heterogeneity of the particles can contribute
significantly k> the range
of PZC values that can be otxained for a given solid. In the case
of sulfide minerals, oxidation of the surface also can affect the
PZC considerably. As the
pH increases. the surface may get oxidized and the potential
obtained at any particular pH may be the net value of the oxide and
the sulfide. In fact. it may be possible to obtain two PZC values
for such minerals, one corresponding to that of the sulfide at
lower pH and the other corresponding to that of the oxide at hi~r
pH values. Some of the wide range of values shown in Table 16.3-1.
for example, chalcocite. cha1copyrite, pentlandite. and spbaierite,
could have resulted partly from such surface oxidation. The role of
the electrical nature of the interface in determining ad.sorption
can be seen for the case of adsorption of dodecylsulfonate on
alumina76 (see Fig. 16.3-4). It can be seen that only below the
point of zero charge of alumina, when the solid is positively
charged. is there measurable adsorption of the anionic sulfonate.
This effect is shown more clearly for the case of calcite. for
which adsorption and resultant flotation with cationic amine is
significant only above the point of zero charge (see Fig. 16.3-5).
Indeed. change in electrical characteristics due to adsorption of
inorganic species can affect significantly the ftotation response
of the particulates. as will be seen later. Thus, ftotation can be
depressed by adding electrolytes that will compete with the
ftotation reagents for adsorption in the interfacial region or
enhanced by adding those electrolytes that can adsotb specifically
and change the charge in the desired di~tion. Depression of alni~
flotation of quartz using monovalent and divalent inorganic cations
has been analyzed recently on the basis of the double-layer model
and its compression." Toward this purpose we rewrite Eq. (16.3-1)
with the .1G~ consisting of the electrical term and a term to
account for the specific adsorptjon of the bivalent ion
(16.3-5)
where cp is the specific adsorption energy. Assuming that ",6 is
equal to the zeta po~ential, that the adsorption density of the
collector ions at the solid-liquid interface is constant for a
given amount of flotation and that the addition of electrolytes has
00 effect on the specific adsorption potential of the collector
ions, one can
write the following equation for the ratio cNolca. for equivalent
flotation:
r~ rHa c~ (cPa. + 2F~ - ~\ ---exp- rBl c:a (16.H)
f&, RT
~
8 9
;<
5.0 3.4
3.8-4.9 6-6.5
3.4
23 24 25, 23 27 28 29. 31 32 27 24 28 28 33 34 28
ABgonite Barite, pBa 3.7-7.0 Calcite, pCa 3.5, ~ 3.0 Celestite
Dolomite Eggonite FluoBpatite FluoBpatite (synthetic), pCA 4.4, pF
4.6 Francolite, pHPO. Magnesite Monazite Scheeiite, pCA 4.8 Silver,
pAg 4.1-4.6 Silver iodide, pAl 5.6 Silver sulfide, pAg 10.2
Strengite 2.8
Andalusite Augite Bentonite Beryl Biotite Chrysocolla Garnet
Kaolinite Kyanite Muscovite Quartz Rhodonite Spodurnene Talc
Tounnaline Zireon
782
26
.10
Molybdenite Nickel sulfate Pentlandite Pyrite PylTtlotite
SpIIalerite
3.0 2.5-3.0
11.5 6.2-6.9
3.0 2-7.5
Short conditioning time Conditioning time not specified
Conditioning time not specified
. Any condition co=sponding to zero eIectrok.inetic potential is
~fe~ to as IEP. In the absence of SlJe'"ific IdsorpcioII PZC = I
EP
AI Si Fe FIGURE 16.3-2 (a) Scanning electron micrograph of a
hematite sample on which spot analysis was conducted. (b) EDAX
analysis of spot G shown in pan (a). Analysis of spot E was similar
to that obtained for spot G. (c) EDAX analysis of spot H as shown
in pan (a). (After Kulkarni and Somasundaran; 7)
counesy of Elsevier Seuqoia S.A., Lausanne. Switzerland.)
783 ~
61
2 3 4 5 6 7 8 9 10 pH
FIGURE 16.3-3 Zeta potential of natural hematite in sodium
dodecylsulfate solution. (Data from Shergold and Mellgren. 74.
7S)
784
785BtiJble and Foam Separations-Ore Flotation
pH FIGURE 16.3-4 Adsor.-ion of dociecylsulronate on alumina as a
function of pH. (After Somasundaran and Fuerstenau; 76 courtesy or
die American Chemical Society.)
of equivalent flotation and thelefole, by assumption, under
constant concentration of the coUector. c:," and c:O ale the
conespondin~ ~Ik cooceotmj(X1s of sodium aIMI barium ions and l"-
and ~ ale the CO(Je-
sponding zeta potentials. rHo aIMI r" are COI\Side~ in this case to
be the ~ii of the hydrated sodium and unhydmed barium ions,
JespectiveJy, and ." is the specific adSCJI1Mion ~rgy of I moi of
barium ioas. The adsorption of hydrated sodium ion on oxide
minerals is nonspecific, since its plesellce is ROC known to
ctIange the point of zero c~ of these minerals. Using a val8e of 2
for r""tr" and 3RT for .", we obtain values on the basis of Eq.
(16.3-6) for the ratio of c:," c:O for constant Rotation. These
dIeOfaical values are seen inTahie 16.3-2 to be in fair agree~t
with experimental values. Considering the complex
100. .,'~: .. - .-".
80
.~ ./'
0
pH FIGURE 16.3-S Flotation of calcite with do<iecylammonium
acetate (DDAA) and ~ium dodccyl sulfate (DDSO.) solutions. (After
Somasundaran aOO Agar;2-' coonesy of Ac8demic Prcss.)
20
I"'. :;;':
-50
~ 70 ~ JO
natu~ of d1e ftWtion process, tI1is ag~~t must be conside~ to
provide .. e~1eIIt support for the role of the electrostatic
interactions in detennining the flotation of such materials.
16.3-2 ~in-chain Interactions FIGURE at low CI
The zeta poteIMiaI pkJt for alumina given in Fig. 16.3-4 as a
fulx:tiOll of pH of ck)(jccylsulfonate soIutioos shows a revenal of
slope below about pH 7, suggesting increased adsorption below this
pH involving forces in addition 10 ~cal attrxtioo. The adsorption
isodIenn oMained for ck)(jccylsulfonate on alumina in fact shows a
awted change in slope at a particular sulfact8llt adSOfJJtDI ~ sudI
an intcfPretMioD. Based on the experimental observations d1at a
INmber of other inletf8cial1WOlJClties such as ~. contact angle,
and suspension settling ~te undergo a marlced change in a given
surfactant concentmioa raDle, it was proposed that at low
concentrations of the surfactant, the surfactant KlnS are adsotbed
on the minetal due to electrostatic forces. while at high
concentrations adsorption is assisted further by forces arising
from latenl associative intelXtKlns of the 8fsorbed surfacwM
species (see FilS. 16.3-3-16.3-7). The concentntioo at which such
two-dimensional lateral interactions begin has been shown to depend
on pH, tempe~ture, and the chemical state and the structure of the
surfactant.
16.3-3
dodec) ..1M
compI Al
plSiti
16.:
Surf:
Bubble and Foam SeparationS-Ore Flotation 787
e
SPECIFICALLY 0 COUNTER IONS ~ ADSORBING ,~ COLLECTOR
DEHYDRATED \.~ CATIONS COUNTER IONS
..'0E~ CIII m ~ c fII C C
W I- C W -' 0
L-
0
0
EQUIU8R-* CONCENTRATION OF OLEATE, k..oI/.3
FIGURE 16.M AdS«p.bI iIOttIemI of pocassNm oleate 011 akire at .
natural pH of 9.6. (After So- masuada~ 81 CCXIdeSy of A&:ademic
PIas.)
pH
FIGURE 16.3-' 0Ian&e in zeta jX)Ientiai of calcite particles as
a function of pH at Q)8IsfaIII ionic st~gth 10-3 krnol/m3 KNO1).
(After Somasuitdal2n;87 courtesy of Academic Press.)
788
10.0
16.3-5 Structural Compatibility
For the case of anionic flotation of simple salts such IS fluorite,
it has been suggested by ~n that hydrogen bonding between the
oxygen of the collector and the fluoride species is active and that
it is assisted by the electron resonance of the polar groops, the
stnlcture of which must be compahDIc with the geometry of the
mineral crystal. The role of structural ~~ity also has been
examined for the case of soluble 5alts. For example, Fucmenau and
Fuerstcnau proposed that the surfactant adsoq)tion OIl soluble
5alts is governed by a matdting of size of the functional groop of
the surf8Ctant with that of simtlariy charged lattice ions of the
solid. Thus, aminium ions adsorb on sylvite (KCI) IxIt JQ 011
halite (NaCI), owing to the comparable size of the aminium ion and
the potassium ion. It is to be noted, however, that this theoty
fails to explain why a 1000g-diain aniOllic sulfate will adsorb
OIIly OIl KCI - 00 OIl HaCl.
An alternate mechanism in tenus of hydration properties of the
solid has been pit forward by Rogers and SdIIIlman91 for the
adso~iOll of surfactants 011 soluble 5alts.
16,3-6 Hydration Factors
According to Rogers aIMS Schulman," .tsorpioo 011 soluble salts is
govemed by their solvation properties. the ones with the largest
~gative heat of solution being a beUer adSOItJCIIt than the odIers.
~r, this theory provides no adequate expianatiOll for seveml
adsoqltiOll systems involving soluble 5alts.
16.3-7 Precipitation
An interesting cons~ration by du Riett involves a condition of
p~pilalion of !he surfaclant-laaice ion ~x for
iocipienlll<Mation.92 This ~sm has been examineod subsequently
in detail by a number of investigators.
16.3--8 Adsorption at Liquid-Air Interface
Even though the ftofation process involves three phases and three
interfaces, most re~h work has been solely on the behavior of the
solid-liquid interface. This is in spite of the fact that
8dSOfption at the solid- liquid interface. as shown in Fig 16.3-10.
is of a considerably smaller magnitude thaa dial at the solid- PI
or liquid-gas interface. 9J It is to be DOted that e~cellent
co~IatiOt1 has been obtained ~ndy between surfactant 8dSOIptjon at
the I~id-gas interface 8I.t ftowion for the hematite-oleate system
(see Fig. 16.3- II). It is also important to DOte that the migmMlft
of the surfXIant at the liquid-gas interface is ~ dIan its di«usioo
from bulk to the interface, as least for this system." Such a
migl2tion at the interface CaD help towaRI fastef attainment of ~i~
surfactant ~n density at the solid-gas interface upon the con(act
of the Mibble with the particle.
-9 .
DOAA
~
.. eu"-. -10- 10 0e >- t- (j) ~ 10-" 0 z Q t- A. ~ 10-12., 0 « -
SOLID-GAS
-_.:.. LIQUID-GAS - SOLID-LIQUID
CONCENTRATI<*. kmol/",3
FIGURE 16.3-10 Comparison of Idso~ or dociecylammonium acetate at
dilfe~1 interfaces. (After Somasundaran;93 courtesy or American
Instilute of Metallurgical Engineen.)
-15 10 -
1 !., J oj I *
100
4080
0 IIM)86 pH
fiGURE 16.3-11 Comparison of 8oIation properties of 3 x IO-s
kmol/m) potassium oleate solutions with final surface pressu~ at
2SoC. (After Kulkarni and Somasundaran;90 courtesy of American
Institute
of Chemical Engineers.)
16.3-9 Role of lonomolecular Complexes
Studies of die liquid-gas interfacial properties have 'provided a
new insight into the flotation mechanisms by revealing the
prominent role of the complexes fonned between different surfactant
species in flotation. Surfactants such as fatty acids and amines
will undergo hydrolysis in water and produce various complexes
depending on the pH of the solution. Thus, oleate will exist in the
ionic form in the alkaline pH range, in the molecular form in the
acidic range, and in the ionomolecular complex in the intermediate
pH range.
RH = R- + H+ ole;' aoid RH = RRH-
ole;. Kid '-n."-- '-"-' R- +-
The role of such ionomolecular complexes has been shown to be a
potentially impol1ant factor in flotation. In fact, the pH of
maximum flotation recovery for the hernatite-oleate system is found
to correspond with the pH where maximum complex fonnation is
expected.94 Evidence for the formation of the highly surface-
active complex was obtained using surface-tension measurements
shown in Fig. 16.3-11. Similarly, the pH of maximum flotation of
quartz using amine has been shown to coincide with the pH at which
maximum lowering of the adhesive tension of the system and of the
surface tension of amine solutions occurs (see Figs.
16.3-12-16.3-14). This is also the pH region in which stable
amine-aminium ion complexes can be expected. The thermogravimetric
analysis results of Kung and Goddard96 have provided some evidence
for the existence of such ionornolecular complexes in the bulk
phase also. From these results, the formation of complexes between
neutral molecules and ions appears to play an imponant part in
their enhanced adsorption and resultant flotation using them. It
must be pointed out that such correlation has not been
obtained during studies using tertiary amines.
~. f~1:han
pH FIGURE 16.3-12 AotaIion ~very of qualU as a function of solutjon
pH using dodecylammonium acetate as collector for ftowion dumion
of.5 aIKIlO s. (After SomasUJ.tafan;" ~nesy of Elsevier S.A..
Lausanne. Switzerland.)
E u
\AI U :: «
pH FIGURE 16.3-13 Adhesion tension of dodecylamlOOOium chloride
solution of VaMIs CO(M:efttrations as a function of solution pH.
(After Somasundaran;9S courtesy of Elsevier S.A.. Lausanne.
SwitzerlaOO.)
791
.701
'0
~
.. 4-10-5 kmol/m' OOAA
10 ... 13
pH fiGURE 16.3-14 Surface tension of 4 X 10-. kmoUm) dodecylamine
hydrochloride solution as a function of pH detennined by pendant
drop methOO, measu~ 15 s after fonning drop." (After R. W. Smith,
personal communication, 1967.)
The mechanism of adsotption of complexes on minerals has not been
investigated. It can be noted, however, that the electrostatic
factor can be impof1ant in this case also, since the complexes like
the monomer ions are charged. In addition, increase in the
effective size of the species dIIC to complex fonnation can be
expected to make the surfactant less soluble in water and bcncc
more active.
16.4 FLOTAIDS
In addition to collectors. a number of othcr cbemical additives are
used in flotatton to aid 5epantion by this process. They include
Crothers, activalors. IiePfCssants. deactivators,! ftocculants, and
dispersants.
16.4-1 Frothers
To produce die desiJed froth stability, nonionic surfactants. such
as die sparingly soluble monohydroxylated clesols. usually ale
added. panicularly when the collector used is of die shon-chain
type. The opcimum concentration of die frother in die system is
approximately that at which dlele is a significant change in
surface tension with surfactant addition (Fig. 16.4-1). It is
possible, even though not proved. that the restoring force that
becomes available upon any distention of die bubble to plevent its
ruptule might contribute toward die requi!ed froth stability in the
flotation cell. Indeed. this is applicable only if the diffusion of
the surfactant to the locally extended surface legion is not fast
enoogh to !educe die surface PIeSSUIe difference between this
legion and the sunounding surface, before the distention is
lepai!ed by such pressule diffelence.
In addition to inducing froth stability. frother species can take
pan in the overall process of adsorption on the mineral surface.
Like die collector species, the frother species also can be
expected to migrate to the panicle-gas interface during the time of
contact and assist in establishing the attachment of die bubble to
the panicle. Coadsorption of frother along with the collector
species2~ can be favorable for flotation, possibly because the
neutral molecules adsorbed between charged collector ions can
reduce the repulsion between the latter species and theleby enhance
the overall surfactant adsorption.
16.4-2 Activators
Activators are used for enhancing flotation of the minerals that
may not possess any ftotability in their absence. Flotation of quam
using calcium salts and of sphalerite using copper sulfate (see
Fig. 16.4-2) are typical examples of activation. In the case of
oleate flotation of quam in the presence of calcium, activation can
be attriooted to electrostatic adsorption of the calcium ions on
the negatively charged quartz
50
I
30
z 0 Ui z
, ---,
FIGURE 16.4-1 Di8gI2m iUustl8tiog the conelatioa belween froth
stability and swf~ lellsion lowering due to die addition of a
surfactant. (After Cooke;' coortcsy of John Wiley &
Sons.)
aIMS ~ providing sites for adSOI1Mion of the oIeaIr. colIcdOl'
species. Bivaleat ions, IIIMJI\ ~, can revene die sign of the stem
potential and thQ cause adIOrp(Joa aIMS ftowionwith collectors that
have a clwge of the - sip as that of the miaeraJ (~FiC.
16.4-3).
However, sphalerite activarm by copper sulfate is the result of
adIOlption of copper ions on the surface of this mineral, due ID
~-eXchanle processes. The eft"ect of adivMon also can be due to
their reactions with the collectors to foml ~nds of low-solubility
product. 7
Another typical e~ of activation is that of die o~ or cartMJn8Ie
minetals by sodiwn sulfide. For example, in the case of cenusite,'
the following reactjons can produce a surface layer of
sulfide:
Na~ + HzO ;:!; NaSH + NaOH
NaSH + NaHi'bOz ;:!; 2NaOH + ~
NazS + PbCO) ;:!; ~ + ~
The cenusile surface, which is allefed in the above manner. can be
ftoa~ with unthale col~. In certain cases. on die IXher haJJd, it
is necessary to .emove allefed su~ using acMIs 10 obtaia ftotation
(see Fig. 16.4-4). Acids can also enhance notation fk)SSibly by
senerating microbubbles on the minem surface as has been suggested
in die case of calcile.9 .
# 100
~ CuSO4'5H20,lbm/tonore
FIGURE 16.4-2 Flotation of pu~ sphalerite. "rile g~1ar minenl.
1000ISO mesh was lloated with xan thate 0.10 lb/tOll. terpineol.
0.20 Ib/ton. sodium ~te. 2.00 Ib/ton. and copper sulfate. as shown
(From Ref. 5; courtesy of McGraw-Hili. New York.)
-,\(794 P. Somasundaran and K. P. Ananthapadmanabhan
~ ~
Ca CCM1Centration (mmol/ L)
FIGURE 16.4-3 Effect of amount of Ca2+ in die ftotation of quartz
by different surfactanls (From Ref. 6.
16.4-3 Depressants
~nts are organic or inorganic reagents that prevent the collector
adsofption on the mineml by intef2C1jng with the mineRl or the
collector. Silicates, phosphates, aluminium salts, chromates, and
di- chromates are typical inorganic salts used as depressants. The
action of sodium silicate in flotation is considered to be due
usually to its depressing effect on quartz present in the pulp and
to its ability to control the dispersion of the slimes that are
present in ~ pulp. The effectiveness of silicates has been related
to the degree of polymerization that it can undergo under the given
conditions.IO The effect of polyvalent cations in the case
offtotation of phosphate or calcite. on the other hand, is
attributed primarily to collector precipitation in the presence of
these ions.I'.'2 Polyvalent ions also can prevent collector
adsorption by causing charge reversal of mineRls. For example,
addition of soluble phospIIate can depress flotation of apatite
using oleate (see Fig. 16.4-5).
~
~Ie .nd ~m ~r"i--Ore Aot.tion 795
pH fiGURE 16.4-5 Eft"ect of ~e SfJeCies on die ftocatioo of
8I8itell'. K~ 2 x 10-6 knd/m}
-COH. These 1Q&ent5 can act by ~ adsorption on die minerals as
wdl as by causing IIoccu..- of . 51- dI8t is ~"bIe for excessive
coUector coasunllMioa. Even IhcMIgh such IQgeIMs have been used
extensively as modifien, . actual ~hanisms by which .y act ~ oot
ulMieBtood totally. SclMIIIz and Cooke" and Balajee and Iwasaki"
have shown that the adsorption of stareh on iron oxide ~rials
depends 00 the type of staIdI, its ~ntion, the extent of brudling.
and so 00. Experime.-s ~ ~Iy 00 die adsorpjon of staldliiId okaIe
in die p~ of each other have provided so~ insight into the
mechanisms involved here (Ref. 16.3-8). It was found dI8t. in
dlis~. the ltart:h does not reduce lIocation by inhibilingdle
adsorption of surfactant on calcite particles. In fact. ~
adsorption of oleate on calcite was found to be higher in die ~ of
starch than odIefWise: (~Figs. 16.4-6-16.4-8). Similarly. die
adsorption of SWt:h also was enhanced by oleate. Deprasion of
mineral fIocation obtained under dIr;se conditions suggested that
even though die mineral has adsorbed ~ oleate, it has ~mained
hydrophilic. This unusual pheno~non was ascribed to the fonnation
of the helical-type structure that stareh assumes in the ~ of
hydrophobic materials or in alkaline solutions aIM1 to the fact
that the interior of dIis helix is hydrophobic aIKI . exterior is
hydrophilic. It was sugesled that . adsoftJed oleate is wl3AJcd
inside the starch helices. InterKtions between die nonpolar
surfactant cI1ajn and the hydrophobic staldl interior can be
expected to pr{Kfuce mutual enhancement of adsorptioIi. The
hyd~philic nature of calcite in . presence of starch and oleate
results from die fact that die adsoI,bed oleate is obscured from
die txllk.
.. , . ~ ,~~',~ ,"'" IC~ *
~ "
~/
loci' ~'*'~'~'~l~5 CONCENTRATION OF STARCH, ppm
FIGURE 16.4-6 Adsorption density or oleate on calcite at natural pH
9.6-9.8 IS a runction or stan:h added prior to the oleate additKln.
(After Somasundaran. Rer. 16.3-87; counesv or Academic
Pre.u.\
~ t796 P. Somasundaran and K. P. Ananthapadmanabhan
solution by Slan:h helices with a hydrophilic exterior and from
possible masking of the collector adsorbed on die mineral in the
normal manner by massive stan:h species.
Simple organic compounds such as citric acid, tartaric acid, oxalic
acid. and EDT A often are used as modiliers.'6 Some of these
reagents react by complexing varioos interfering ions such as
calcium that are usually present in the solution.
16.44 Deactivat()rS
Deactivators interact with activators to form an inert species and
thus prevent activation. An example is the deactivation of copper
in the xanthate flotation of sulfides by cyanides.
16.5 VARIABLES IN FLOTATION
A number of variables are encountered in flotatioll due to the
variations in the raw materials. methods of their preparation,
reagentizing, and the actual flotation p!occss itself. An
understanding of the effect of the
kmol/m3 o'eate 0 10- 4
610-5 ~ 0 \&J t- ~ 0 ..J I&.
0 4.5 9 13.5 18 CONCENTRATION OF STARCH, ppm
.
~ 797Bubble ~nd Foam Separ~tions-ore Flotation
variables can help towani proper control of the flotation for
optimum perfonnance. The effects of major physical BOO chemical
variables have been ~viewed e1sewhe~.1.1
The chemical variables that can play a major role iJK:lude chemical
state and SUuclu~ of !he surfxtant. including its d\ain length.
concentrations of surfactant. complexing ions. flocculants. and
dispersants. pH, ionic st~ngth. BOO !he temperatu~ of !he solution.
As mentioned earlier, flotation can be expected to be maximum if
the collector is ~nt as iono~1ar complexes. Substitution of
hydrogen in !he -CH1- groops of die long chain with fluorine has
been fouoo to produce a significant inclease in ftOtalion! Of
course. flotation is strongly dependent on collector concentration.
Rubin et al.4.' among others have stUdied !he dependence of
~ipilale flotations and ion flOlalions on die ~tration of die
collector. While a collector to coIligelMi ratio of 0.2: I normally
is rIeceSSaIY for achieving good flotation of precipitates. die ioo
flotation was fouoo to need much larger quantitiC$. For foam
separation techniques, die most suitable surfac1aDI COIK:entration
is die lowest one that provides !he desi~ foaming prqIerties.H
Transiency of die fOIm was found desirable for eXUactj()l\ in
solUtions of low collector ~rations. In fmh ftotatjoo also, an
excess of collector has sometimes been fouoo to produce ~
extraction.'
Flocculants and polymers can cause an inclease or a declease in
ftocatjoo depending 00 the properties of !he coIIi&enS. 1005.
while flOCation of B ~ and illite with miam lauryl sulfate can be
eahanced by Piing alum,lO. II that of calcite and apatite using
sodium oIcate can be depressed tot,aJly usinl starch.
The pH of die solution is an important variable controlling
flotation since die pH can affect die electrical .-.nies of die
particle surfaces BOO its solubility as well as !he clIemicaI state
of !he surfactant. The effect of pH due to its role in determining
die surface charge of die paIlicles is illustrated in Fil. 16.3-5
whe~ ooly die collector that is charged oppositely to die mineral
surface is capable of producing significant ftOIatjoe. The role of
pH in determining !he chemical state of oleate and amine and !heRby
flOCatioa usins them a- been discussed earlier. Maximum ~ was
otMained in ~ cases under pH ~itions that generate ionoroolecular
complexes of the collector.
Ionic StJm&dl has a silnificant role to play ia determining die
~ of collector on die mineral as wdl as 00 die tMlbble due to both
the incteascd electrical double-layer con..,rcssion and die
inclased salting out of die collector from the aqueous solution
with increase in ionic strength. Wbile the effect on die double
layer will cause a decrease in flotation for sySfems whe~
electrostatic autactioo is a major factor. the salting unit effect
will produce an increase in ~. When the iJK:1ease ~ ionic stRagth
is the ~It of a salt containing a bivalent counterion. the ~sion of
flotation is even larger. This IaIBef effect results from the
tendency of the bivalent ions to adsorb strongly and compete with
the collector more than the monovalent ions. This effect also can
be used 10 activate the 8OIalion of a particle that has a charge
similar to dIat of a collector (see Fig. 16.4-3). Enough bivalent
ions a~ introduced in this ~ to cause a particle charge ~versal.
the~by making the collector adSOl]llion possible.
The effect of variation in the temperatu~ of the pulp or solution
or 8IMaIioa has not been studied in detail. Elevation in tempera~
is expected to ~ adsolpCioo of collectors on minerals if die
IdSOIption is due to physical foR:eS. and to inc~ adsorption if it
is due to chemical foR:eS. An inte~ng observation in this qard has
been the ~Its obtained for the flotation of hematite using oleate
under various ionic
798
!u 'Su.a- ..
a .E .g £
.
~:ac.!!~"Q , ~cd
;I. .z~.. ... .. ,- ~
. ~ILo c'C0(U"0.cgSU
s
strength conditions. In this case an increase in temperature
enhanced flotation but only under low ionic strength conditions
(Fig. 16.5-1). Above an ionic strength of 2 x 10-3 kmol/m).
flotation was found to decrease with an increase in temperature.
These temperature-ionic strength interactions are attributed to be
the effect of adsorption of the oleate on the mineral and the
salting out of the oleate from the solution. It is to be noted that
the alterations in temperature also can affect the performance of a
foam separation technique due to its effects on foam drainage,
transiency, and adsorption on the bubble surface.
Physical hydrodynamic variables that can affect the flotation, even
though not to as great an extent as the clIemical variables listed
above, include gas flow rate, bubble size distribution, agitation,
feed rate. foam height, and reagent addition RxJdes.
A detailed list of foam separation studies is available in a number
of reviews Refs. 16.1-1. 16.1-2. 16.3-6, 16.5-13-16.5.15). A
compilation of major minerals and other particulate matter that
have been separated by froth flotation are given in Table
16.5.1.
REFERENCES
Section 16.1
P. Somasundaran, Foam Separation Melbods. in E. S. Perry aOO C. J.
Vann Oss (Eds.). Sepa- ration and Purification Methods. Vol. I, p.
117. Man:el Dekker. New York, 1972.
P. Somasundaran. Separation Using Foaming Techniques. Sep. Sci.,
10,93 (1975).
Section 16.2
16.2-1 C. C. Hams, Flotalioo Machines in M. C. Fuerstenau (Ed.),
Flotation, Vol. 1, p. 753, A. M. Gaudin Memorial International
Rotation Symposium. AIME, New York, 1976.
16.2-2 D. W. Fuerstenau, P. H. Metzger, and G. D. Seele, Eng. Min.
J., 158,93 (1957). 16.2-3 M. C. Fuerstenau, Eng. Min. J., 165, 108
(1964). 16.2-4 R. D. Kulkami, "Flotation Properties of
Hematite.oOleate System and Their Dependence 00 the
Interfacial Adsotption," D. Eng. Sci., Dissertation, Columbia
University, New York, 1976.
16.2-5 M. Goldberg and E. Rubin, Ind. Eng. Chem. Proc. Des. Dev.,
6, 195 (1967). 16.2-6 T. A. Pinfold, Adsorptive Bubble Separation
MetIKJds, &po Sri., S, 379 (1970). 16.2-7 E. J. Mahne and T. A.
Pinfold, Precipitate Flotation, J. AppL oIem., 18,52 (1968). 16.2-8
E. J. Mahne and T. A. Pinfold, Selective Precipitate Flotation,
Chem. Ind., 1299 (1966). 16.2-9 D. B. Chambers and W. R. T.
Cottrell, Rotatioo: Two Fresh Ways to Treat Elftuents, Chem.
Eng., 83(16), 95 (Aug. 2, 1976). 16.2-10 R. Sizzelman,
Cleveland-Cliffs Takes the Wraps Off Revolutionary New Tilden Ore
Process,
Eng. Min. J. 10, 79 (1975). 16.2-11 D. N. Collins and A. D. Read,
The Treatment of Slimes, Miner. Sri. Eng., 3, 19 (1971). 16.2-12 S.
K. Kuzkin and V. P. Nebera, "Syndletic Rocculants in Dewatering
Processes," Trans. J. E.
Baker, National Lending Library, Boston Spa 278, 1966. 16.2-13 O.
Griot and J. A. Kitchener, Role Surface Silanol Groups in the
Flocculation of Silica Suspen-
sions by Polyacrylamides, Trans. Faraday Soc., 61, 1026 (1965).
16.2-14 A. M. Gaudin and P. Malozemoff, Recovery by Flotation of
Mineral Particles or Colloidal Size,
J. Phys. Chem., 37, 597 (1932). 16.2-15 A. D. Read, "Selective
Flocculation or Fine Mineral Suspensions," Stevenage, Warren
Spring
Lab. Repon LR88 (MST), 1969. 16.2-16 A. D. Read, Selective
Flocculation Separation Involving Hematite, Trans. IMM (London),
SO,
C24 (1971). 16.2-17 I. Iwasaki, W. J. Carlson, Jr., andS. M.
Parmener, The Use of Stan;hes and Stan;h Derivatives
as Depressants, and Rocculants in Iron Ore Beneficiation, Trans.
AIME, 244, 88 (1969). 16.2-18 A. D. Read and A. Whitehead,
Treatrnenl of Mineral Combinations by Selective Flocculation.
Proc. X Int. Min. Proc. Conp;., IMM (London). 949 (1974). 16.2-19
M. Carta. G. B. Alsano, C. Deal Fa. M. Ghiani, P. Massacci, and F.
Satta, "Investigations on
Beneficiation or Ultrafine Fluorite from Latium." Proc. XI Int.
Min. Proc. Cong., Paper 41, 1975.
16.2-20 Y. S. Kim and H. Zeitlin, Anal. Chem. Acra, 46, 1 (1969).
16.2-21 H. M. Smith and I. E. Puddington. Spherical Agglomeration
of BaSO., Can. J. Chem., 38,
1911 (1960).
f?" 801 Bubble and Foam Separations-Ore Flotation
Section 16.3 16.3-1 M. C. Fuemenau. f1otation. A. M. Gaudin
Memorial Vols. I and 2. AIME. New York, 1976.
16.3-2 J. Leja. Surface Chemistry of Flotation, Plenum, New York,
1982. 16.3-3 R. P. King, Principles of Flotation, Sooth African
InstitUte of Mining and Metallurgy, Johan-
nesburg. 1982. D. W. Fuerstenau, Froth Flotation, 50th Ann. Vol.
AlME. New York. 1962. P. Somasundatan and R. B. Grieves.
Interfacial Phenomena of particulatelSollltionlGas Systems.
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16.3-91 J. Rogers and J. H. Schulman, Mechanism of the Selective
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Section 16.5
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New York. 1975.
805Bubble and Foam Separations-Ore Flotation
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16.54 A. J. Rubin, J. D. Johnson and C. Lamb, Comparison of
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FIO-B71.
16.5.0
'(\,\-1