Water
`Soluble
`Polymers
`
`GAL
`. 50ad
`
`si
`
`2
`
`C
`
`.
`
`900
`
`700
`
`500
`
`500
`
`400
`
`300
`
`'
`
`1IN
`
`20°C
`1000
`
`706
`
`600
`
`500
`
`400
`
`300
`
`200
`
`100
`
`FLOERGER®j
`
`EXHIBIT
`
`SNF Holding Company et al v BASF Corporation,
`
`Page 1 of 57
`IPR2015-00600
`
`

`
`Introduction
`
`Water soluble polymers
`
`cover a wide
`
`range of
`
`highly varied families of products of natural or
`
`synthetic origin, and have numerous uses.
`
`Among these families, synthetic polymers,
`
`and
`
`more particularly coagulants and ßocculants, are
`
`used mainly
`
`for facilitating the separation
`
`of
`
`materials in suspension
`
`in aqueous media. They
`
`also help to dewater sludge fmm various separa-
`
`tion processes.
`
`The separation of solids in a liquid medium takes
`
`þlace mpidly when the density of the particles
`
`is
`
`markedly different
`
`from that of the liquid
`
`medium. Either the particles
`
`settle out or
`
`they
`
`float on top of the liquid.
`
`Difpeulties occur when the particle size allows it
`
`to remain in suspension in the liquid medium.
`
`In this case, the use of coagulants and ßocculants
`
`allows separation to be carried out.
`
`SNF HIWSNWM
`
`Page 2 of 57
`
`

`
`2 Table of contents
`
`if
`
`il
`
`Ill
`III-I
`
`INTRODUCTION
`
`TABLE OF CONTENTS
`
`BASIC PRINCIPLES OF COLLOfD SCIENCE
`
`Colloidal suspensions
`Ilf-I-I
`HI-I-2
`
`_ Hydrophobic colloids
`Hydophilic colloids
`
`III-2
`
`Measurement
`
`of
`
`the concentration of colloids
`
`IV
`
`IV-I
`
`IV-2
`
`IV-3
`
`IV-4
`
`COAGULATION AND FLOCCULATION
`Charge neutmlization _
`Adsorption
`
`Suspension destabilization by coagulation
`
`Suspension destabilization by flocculation
`
`IV-4- I
`
`N-4-2
`
`IV-4-3
`
`Initiation of
`
`Kinetics of
`
`f locs
`floc development
`
`_
`
`Consistency o¶ ff ocs
`
`_ _
`
`IV-5
`
`Other sus ension destabilization systems
`
`IV-5- I
`
`IV-5-2
`
`N-5-3
`
`W-6
`
`Efficiency
`
`"Encapsulation"
`
`syst_ems
`
`Two-polymer-component
`
`coagulation systems
`
`_ Microgarticulate
`o¶flocculation and coagulation
`
`systems
`
`i
`
`2
`
`6
`
`6
`
`6
`
`7
`
`7
`
`8
`
`8
`
`9
`
`I0
`
`I O
`
`I O
`
`I2
`
`I2
`
`I 3
`
`I 3
`
`I 3
`
`I 3
`
`I4
`
`Page 3 of 57
`
`

`
`IV-7
`
`Parameters having an influence on the eficiency of flocculation and coagulation
`
`IV-7- I
`
`IV-7-2
`
`IV-7-3
`
`IV-7-4
`
`IV-7-5
`
`Inpuence of
`
`the particles
`
`_
`
`Inpuence of
`the polymers
`Influence of the polymer mixing in the solution
`
`influence o¶the pH and the temperature of
`
`the solution
`
`Influence o¶the organic nature o¶the suspension
`
`IV-8
`
`Advantages o¶ synthetic
`
`coagulants
`
`Y
`
`V-I
`
`WATER SOLUBLE POLYMERS
`
`Coagulants
`V I-I
`
`V-t-2
`
`V-I-3
`
`Quaternary polyamines
`
`PolyDADMAC
`
`Dicyandiamide resins
`
`V-2
`
`Flocculants
`
`Y 2-I
`
`V-2-2
`
`V-2-3
`
`Nonionic flocculants
`
`Anionic flocculants
`
`Cationic flocculants
`
`V-3
`
`V-4
`
`V-5
`
`V-6
`
`V-7
`
`Amphoteric copolymers
`
`Other polymers
`
`Pmducts in solution
`
`ßranched
`
`ers
`
`Thickening agents
`
`I4
`
`I 4
`
`15
`
`I 6
`
`I 7
`
`I 7
`
`I 7
`
`la
`
`8
`
`18
`
`19
`
`20
`
`20
`
`20
`2I
`
`2 I
`
`22
`
`22
`
`23
`
`23
`
`23
`
`Page 4 of 57
`
`

`
`4 Table ofcontents
`
`VI
`
`VI-I
`
`VI-2
`
`VI-3
`
`VI-4
`
`PHYSICAL FORMS OF POLYMERS
`
`Powders
`
`Emulsions
`
`Polyacrylamides in bead form
`
`Products in solution
`
`VII CHEMICAL CHARACTERISTICS OF POLYMERS
`
`VII-I
`
`VII-2
`
`Viscosity
`
`Measurements
`
`o¶_the molecular mass
`
`_ _ _
`
`VII-2-I
`
`Vit-2-2
`
`VII-3
`
`Stability__
`
`VII-3-I
`
`VII-3-2
`
`lonicity
`
`VII-4
`
`VII-5
`
`VII-6
`
`Light scattering method
`
`Intrinsic viscosity method
`_ _ _ _ _ _
`gynical ami biochemical stability
`Mechanical
`
`stability
`
`__
`
`_
`
`_ __
`
`_ _
`
`Residual polymer content
`
`foyicity
`
`_
`
`_
`
`_
`
`Ylli LABORATORYTESTS AND INDUSTRIALTRJALS
`VIII-I Principles
`
`Vill-2 Main laboratory process-water and municipal-water
`
`VIII-3
`
`Use o¶the polymers
`
`_
`_
`treatment applications
`
`VIII-3-I
`
`VIII-3-2
`
`VIII-3-3
`
`Polymers
`
`in powder¶orm and in bead form
`
`Polymer emulsions
`
`Pol
`
`Ym
`
`er solutions
`
`24
`
`24
`
`25
`
`27
`
`27
`
`28
`
`29
`
`30
`3I
`
`3 i
`
`32
`
`32
`
`32
`
`33
`
`33
`
`33
`
`34
`
`34
`
`36
`
`37
`
`37
`
`37
`
`37
`
`Page 5 of 57
`
`

`
`IX GENERALAPPLICATIONS
`IX-I
`Separation processes
`using flocculation
`IX-I-I
`IX-I-2
`IX-t-3
`
`Settling
`
`Centrifuging
`
`Belt
`
`filters
`
`IX-2
`
`IX-3
`
`IX-4
`
`IX-5
`
`IX-6
`
`X
`X-I
`
`X-2
`
`X-3
`
`X-4
`
`Potable water
`
`Process water
`
`Industrial egiuent
`
`Municipal sewage
`
`Thickening and dewatering of studge
`
`SPECIALAPPLICATIONS
`Mining industry
`
`The paper industry
`
`The þetroleum industry
`
`The cosmetic
`
`industry
`
`X-4-I
`
`X-4-2
`
`Conditioners and ßlm-forming agents
`
`for hair and skin products
`
`Thickening agents
`
`and emulsion stabilizers
`
`X-5
`
`The textile industry
`
`X-5-I
`
`X-5-2
`
`X-5-3
`
`Synthetic
`
`thickeners
`
`sizing agents
`
`Fixing agents
`
`X-6
`
`Agriculture-Soil conditioners
`
`38
`
`39
`
`39
`
`40
`4I
`
`42
`
`43
`
`44
`
`45
`
`46
`
`48
`
`48
`
`49
`
`50
`
`51
`
`SI
`
`5 I
`
`52
`
`52
`
`52
`
`52
`
`53
`
`Page 6 of 57
`
`

`
`Basicprinczples
`6 of colloid science
`
`In liquid media and more particularly aqueous
`media, organic or inorganic materials are present
`in dissolved or solid form.
`
`These two forms are distinguished by the size of
`the particles,
`
`-
`
`Dissolved compounds are:
`ions ondlor organic com-
`Inorganic compounds,
`of low molecular weight with a particle
`pounds
`size of at most 10 3 µm;
`- Soluble organic compounds of high molecular
`as proteins or polymers, with a
`weight,
`such
`slightly larger particle size of between 10" and
`10 3 µm.
`
`Solid compounds are:
`- Colloids with a particle size of between about
`IO" and I µm;
`- Materials in suspension with a particle size of
`more than I µm.
`
`111-1 Colloidal suspensions
`Colloidal particles,
`the naked eye, undergo
`invisible
`to
`high-speed Brownian motion -
`speed is between
`the
`largest
`particles
`0.004 m/s
`and
`the
`case
`o¶ the
`in
`the smallest.These particles also
`I 00 m/s
`in the case of
`propor-
`surface
`area
`(inverseÏy
`very high specific
`have a
`to the partide diameter).They
`are therefore more
`tional
`phenomena
`than to gravitational
`sensitive
`to surface
`the largest colloid particles wi/I have a natu-
`¶orces.Thus,
`a depth of
`I m of water of about
`rol settiing time
`over
`two years.
`
`Colloidal particles con there¶ore form suspensions which
`over
`time.
`are very stable
`
`a colloid suspension depends on the equi-
`The stability of
`librium between two
`o¶ opposing ¶orces
`types
`involved.
`the universal attrac-
`These are Van derWaals'-type
`force -
`dve force between atoms
`and molecuÏes,- and an electro-
`interaction force.
`static
`
`depending on the intrinsic
`These two forces act dif¶erently
`nature of
`colloids, which are either hydroþhilic,
`the
`water molecules
`are adsorbed
`onto their surface,
`conversely,hydrophobic.
`
`i.e.
`
`or,
`
`Colloids
`
`Ill-I-I Hydrophobic colloids
`a hydrophobic nature (for e×ample, clays) ¶orm
`of
`susþensions because their
`charge is
`sur¶ace
`the
`stable
`same and they reþeÏ each other.These charges may come
`adsorption of an ion onto
`the sur¶ace
`from selective
`lattice defects).
`¶rom the surface
`itself
`(crystal
`
`or
`
`the electrically charged particle is at
`a dif-
`The sur¶ace of
`solvent medium. Electrostatic
`¶erent potential
`from the
`equilibrium between the sur¶ace
`the particle and the
`of
`solvent medium is achieved by means of
`two transitional
`layers.
`
`Page 7 of 57
`
`

`
`is ßxed and remains attached to the surfa-
`layer
`The first
`ce o¶the particle.The
`layer, seþarated ¶rom the
`second
`ßrst by a shear plane,is more diffuse.
`
`Figure 1 - Equilibrium layers of
`
`a colloidal particle
`
`PotZe
`
`al
`
`+
`
`+
`
`N
`se\
`Di
`Layer
`
`1
`
`+
`
`+ |
`
`4
`
`+
`
`*
`
`Solution
`
`+
`
`+
`
`+
`
`Shear
`Plane
`
`The potential dij¶erence between the shear plane and the
`solution is called the zeta þotential.This
`potential
`dij¶e-
`rence is about
`I 0 to 200 mV When it
`reduced to zero
`is
`or close to zero (the isoelectric þoint},the particles tend to
`agglomerate under
`influence of
`the Van der Waals'
`the
`forces and the colloidal suspension becomes destabilized,
`
`III -l-
`Colloids
`
`2 Hydophilic coHolds
`a hydrophilic nature (generally organic sub-
`o(
`owe their stability to the layers
`of water mole-
`stances)
`cules bonded to the surface o¶the particle.The bonds are
`of a chemical nature and the electostatic
`charges play
`only a secondary role.The layers
`of water molecules pre-
`any aggiomeration between particles.
`vent
`this
`case,
`In
`there is no real
`interface between the particle and the sol-
`vent medium.
`
`hüYe GD Ín(IUenCO 00 th€ SDIubility of hydro-
`The charges
`philic colloids.The importance of
`the role o¶the charges
`depends on the degree o¶ionization ofthe particle's func-
`tional groups.The degree of
`ionization itsel¶ depends on
`the pH of
`the medium.
`In general, the solubility is
`a mini-
`mum amund the isoelectric þoint, which corresþonds to a
`pH of between 4.0 and 6.5.
`
`Hydrophilic colloidal suspensions there¶ore are akin to an
`actual solution of very large molecules or of aggregates of
`small molecules, with a very high affinity
`for
`the solvent.
`
`can be adsorbed onto
`In some cases, hydroþhilic colloids
`of hydrophobic
`colloids, such
`the
`clays
`for
`sur¶ace
`as
`impart
`and thus
`a hydroþhilic nature to the
`examþIe,
`hydroþhobic þarticle. Such colÏoidal suspensions are then
`to destabilize.
`very difficult
`
`111-2 Measurementof the colloid
`concentration
`There are no direct measurements of
`tration.
`
`the colloid concen-
`
`be directly observed with a
`The colloidal particles
`can
`microscope.They are visible indirectly by light reflection or
`the Tyndall effect, which is why colloidal solutions are tur-
`bid.
`
`The turbidity may be quantified by nephetometry,a
`relati-
`ve measurement expressed
`in NTU (Nephelometric
`Turbidity Unit) with
`resþect
`a calibration solution of
`to
`zero turbidity (French
`¶ormazine in water which has
`Standard NFT 90.053).
`
`Page 8 of 57
`
`

`
`8 Coagulationandflocculation
`
`The conventional methods of solid-liquid separa-
`
`tion, such as filtration, sedimentation,
`
`centrifuga-
`
`tion and flotation, cannot
`
`be used directly on
`
`stabilized suspensions.The particles
`
`are too fine
`
`and
`
`remain separated from each other.
`
`Coagulation
`
`and flocculation destabilize
`
`these
`
`suspensions and allow solid-liquid separation.
`
`Two mechanisms
`
`are mainly
`
`involved, namely
`
`charge neutralization and adsorption.
`
`IV-1 Charge neutralization
`In aqueous media, hydrophobic
`colloidal particles
`generally negatively
`charged. The increase in
`the
`cation
`content of
`the solution reduces the zeta potential and
`therefore the
`thickness of
`double
`layer which
`the
`surrounds the colloidal particle.
`
`are
`
`When the electrical protection of
`the particles has been
`removed or sufficiently
`reduced, the moving particles can
`collide with each other due to
`the momentum of
`Brownian motion,
`the movement of
`the fluid in which they
`are contained and the relative movement of
`the particles
`by sedimentation.
`
`The Van der Waals' ¶orces and the
`adsorption
`surface
`then become dominant again. Since
`phenomena
`the
`particle can bond together, the suspension is destabilized.
`
`a
`
`is
`
`This charge neutralization mechanism is
`reversible.There
`limiting cation
`concentration which allows destabiliza-
`if cations
`this critical concentration,
`to occur. Above
`tion
`continue to be added,
`o new ionic imbalance between the
`particle and the solution may be created,
`leading to the
`formation of
`a new double layer and to the restabilization
`the suspension.
`of
`
`The charge neutralization efficiency
`of an electroÏyte
`(the Schulze and Hardy rule).
`increases
`with
`valency
`its
`This explains the predominant
`trivalent
`use of bivalent or
`for destabilizing colloidal suspensions.
`electrolytes
`
`Page 9 of 57
`
`

`
`Adsorption is
`a complex mechanism involving a
`large number of pommeters miating to:
`
`The coagulant:
`structure of
`the molecular chain
`ionic charge density
`molecular weight
`
`The colloids:
`number o¶available sites
`charges
`surface
`surface area
`specißc
`particle concentration
`
`The aqueous medium:
`pH
`conductivity
`presence of other substances
`turbulence
`shear rate temperature
`mixing of
`the products
`
`The complexity of this system exþIains the dißiculties sti/I
`time in understanding
`encountemd at
`the present
`and
`modelling this þhenomenon. The experimental
`approach
`remains indispensable.
`
`IV-2 Adsorption
`Adsorþtion
`a sur¶ace mechanism which allows two
`is
`contacting particles to be bonded to each other by Van
`derWaals'¶orces
`or hydrogen bonds.
`
`Measuring the amount of polymer adsorbed by a colloidal
`o¶ time allows a characteristic
`susþension as
`a ¶unction
`curve, called a Langmuir
`isotherm,
`to be plotted:
`
`Figure 2-Adsorption
`
`isotherm
`
`Degree of
`adsorpten
`mg/g or%
`
`Equßbrium
`
`Time
`
`The characteristic
`is called an isotherm since the
`curve
`adsorþtion is stmngly
`dependent on the temperature and
`any measurement must be carried
`out al constant
`temperatum.
`
`Adsorption is an irreversible mechanism which takes place
`in two steps. Firsdy, after
`a ¶ew seconds, most o¶the reac-
`tion has taken place.After
`a relatÍYOÎy ÏOng 50CQnd Sleþ, G
`limited by the number of
`balance is
`achieYed, which is
`the particle.When all
`sites available on the surface
`of
`the
`available sites are occupied, no further molecule can be
`attached to the surface o¶rhe particle.
`
`SNF fiWi:TWim
`
`Page 10 of 57
`
`

`
`10 Coagulation and flocculation
`
`IV-3 Suspension destabilization
`by coagulation
`Coagulation is
`the destabilization o¶o colloidal suspension
`using products with a high ionic charge density.Two types
`of mechanisms may occur.
`
`IV-4 Suspension destabilization
`by flocculation
`Flaccutation is
`the destabilization of a hydrophobic colloi-
`dal suspension by bonding between colloidal particles
`using long polymer chains.
`
`are added to the colloidal sus-
`the cations
`type,
`first
`In a
`pension in an amount
`just equal
`to neutralize the nego
`tive charges.Coogulation
`occurs directly by charge neutm-
`lization.This type of coagulation is extensively
`used in the
`treatment
`of potable water with iron or aluminium
`cations.
`
`type of coagulation is achieved using polymers
`A second
`(LMW = 20,000 to I million)
`of Low Molecular Weight
`with a high cationic charge.When
`this type of polymer
`is
`in contact with anionic particles,
`its chains may be entire-
`ty adsorbed onto part of
`the colloidat par-
`the surface
`of
`ticles thus ¶orming regions of
`a cationic nature.
`
`Figure 3- Coagulation using a LMW polymer
`
`+ ++
`
`This requires the use of polymers with a high molecular
`than I million) and takes
`weight
`(greater
`þIace
`two
`floc initiation and floc growth.
`main steps:
`
`in
`
`To
`
`IY-4-I Initiation of
`flocs
`initiate flocs,
`the polymers essentially act via a mecha-
`irreversible adsorption of
`the colloids along their
`nism of
`molecular chain.The effect
`this mechanism depends on
`of
`the concentration
`the concentration
`of par-
`o¶ polymer,
`ticles and the particle size.
`
`If an excess of þolymer covers
`the particle,
`the sugace of
`the particle wi/I once again be isolated and the suspension
`will restabilize.
`
`Figure 4
`
`- Isolation of
`
`a particle by a polymer
`
`+
`
`reduces the
`This adsorption o¶ oppositely charged ions
`potential
`and the protection
`the particles.
`surface
`of
`Having become true dipoles, these particles are attracted
`to each other and collide with each
`other. The Van der
`Waals'
`into play, binding the two par-
`forces
`then
`come
`ticles and destabilizing the suspension.
`Coagulation by this
`o¶ mechanism generally has
`type
`higher degrees of aggregation than those
`of
`the simþIe
`electrical neutralization mechanism.
`
`+
`
`+
`
`‡
`
`Page 11 of 57
`
`

`
`In
`
`the
`
`a suspension containing particles which
`case of
`a wide particle-size distribution
`or several particle
`have
`size distributions,
`the susþension may be restabilized ¶or
`different polymer concentrations corresponding to the dif-
`(erent particle-size distributions.Thus, good results may be
`achieved using a given polymer
`for one particle size, but
`for another.As a general
`rule, when this phenomenon
`not
`good flocculation
`is observed but
`occurs,
`relatively
`the
`solution remains very cloudy.
`If the polymer concentration is such that adsorption sites
`remain fiee on the particles,
`the same þolymer chain may
`be able to be adsorbed onto two different particles:
`
`The length o¶ the completely uncolled polymer chains
`as a few tens o¶µm in the
`about
`I µm, possibly
`as much
`chains.These lengths should be com-
`case of
`the longest
`pared with the dimensions of
`the particles, which are
`about
`I µm.
`
`is
`
`Inter-particle bridging can occur with nonionic, cationic or
`anionic polymers.
`In these mechanisms,
`the charge neu-
`tralization phenomena have
`a secondary influence.This
`explains why flocculation reactions can occur with poly-
`carrying charges
`the colloidal
`mers
`of
`the same
`suspension.
`
`sign
`
`as
`
`an influence which pomotes
`The charges may
`have
`better uncoiling ofthe polymer chains due to the ef¶ect o¶
`electrostatic
`repulsion. The shape of
`the polymer chain
`may also be a key factor
`in this process.
`
`o¶the solution may also influence chain un-
`The ionicity
`coiling by limiting or eliminating the repulsion ef¶ect.This
`phenomenon is known as
`the counterion ef¶ect
`or salt
`etreet.
`
`bridging mainly depends on
`polymer,
`a given
`For
`two
`the number of sites available for adsorption
`parameters:
`the particle and the rate o¶collision o¶
`on the sur¶ace of
`the particles.
`.
`
`Figure 5- Bridging between two particles
`
`+
`
`+
`
`mm
`
`the polymer allows part of
`In this mechanism,
`its molecu-
`for chain to uncoil
`the solution beyond the particle's
`in
`double layer.The free end of
`the molecular chain is
`in turn
`adsorbed onto
`o¶ a second þarticle, which
`the surface
`thus creates bridging between the two particles.
`
`the optimum þolymer concen-
`In general, it
`that
`found
`is
`be such that more than half
`tration must
`the adsorption
`sites remain available on the particles.
`
`SNF ENWER
`
`Page 12 of 57
`
`

`
`12 Coagulation andflocculation
`
`IY-4-2 Kinetics of †Ioc development
`Depending on the mechanisms described above, develop-
`ment of
`the j?ocs takes place in several sequential steþs:
`
`IV-4 -3 Consistency of flocs
`namely "so¶t",
`Flors
`can be of
`two
`types
`consistencies,
`which are reversible, and "hard", which are irreversible.
`
`- Dispersion of
`
`the polymer
`
`in the medium
`
`- Dif¶usion
`
`of
`
`the polymer
`
`towards the solid-liquid inter
`
`face
`
`- Adsorption o¶the polymer onto the surface
`a particÏe
`of
`of particles carrying an adsorbed flocculant with
`Collision
`another þarticle
`
`a second particle in
`the flocculant
`- Adsorption of
`onto
`order to ¶orm a bridge and a microfloc
`
`- Growth of
`adsorptions
`
`the microflocs
`
`by successive
`
`collisions
`
`and
`
`- Breaking of
`
`the flocs formed, by shear.
`
`Each step takes place according to its own kinetics and
`result,in terms of
`the floc, depends on the relati-
`the final
`if the
`¶or example,
`o¶ the
`various
`steþs. Thus,
`rates
`ve
`adsorption phase
`is much more rapid than
`the growth
`if
`phase,
`there will
`be many small
`flocs whereas,
`the
`growth rate is higher,
`the flocs will be larger and fewer
`number.
`
`in
`
`In general, adsorption reactions are extremely rapid.The
`due,10
`limiting step in the development
`of
`flocs is mainly
`the frequency of collision between particles and collusions
`with flocs already formed.
`
`floc provides good retention o¶jine particles ¶or
`When a
`low shear
`a quiescent zone, as
`the shear
`rate
`rates
`in
`the retention o¶the fine particles decreases.On
`increases
`returning to the initial shear conditions,
`if the floc resumes
`initial structure,
`is ca]Ied
`soft
`floc. Soft
`(locs are
`its
`it
`generalÏy obtained with polymers of
`low molecu Jar weight.
`
`a
`
`is
`
`stronger, maintains good retention of
`A hard floc,
`fine
`particles
`over wider
`turbulence
`and increased
`shear.
`However, when it
`is subjected to high turbulence for an
`length o¶ time,
`fine particles
`retention of
`excessive
`the
`decreases.The floc then becomes sofi.
`
`The assumed reasons
`this phenomenon stem¶rom the
`for
`configuration of
`the polymer chains
`o¶the
`on the surface
`particle.A hard floc is composed of particles connected by
`bridging via molecular
`chains which uncoil
`the space
`in
`around the particle:
`
`Figure 6
`
`- Hard floc by double flacculation
`
`.y
`
`..
`
`*
`
`*
`
`-
`
`*
`
`+
`
`+
`
`+
`
`-
`
`+
`
`+
`
`-
`
`¯
`
`Initial adsorption
`
`1.
`
`Initial
`
`flocculation
`
`2
`
`3. Change of conformation
`4 Reflocculation
`the molecular chains, due to the influence of
`After
`shear,
`the ionic forces, have a tendency to cover more o¶the sur-
`the particle, giving, by bridging.a floc of so¶t consis-
`face of
`
`tency.
`
`Page 13 of 57
`
`

`
`IV-5 Other suspension
`destabilization systems
`Thme other systems
`are also encountered - still
`employing the two basic mechanisms,
`namely
`charge neutralization and adsorption.
`
`IY -5-I
`"Encapsulation"systems
`The bridging system described above is based on the pri-
`mary interaction between a polymer chain and the par-
`ticle in order
`initiate
`flocculation.
`regards
`to
`As
`encaþsulation mechanisms,
`occur when two
`these
`or
`mom polymer chains react ßrst of all with each other due
`to the influence o¶electrostatic interactions or of hydogen
`reaction produces a network
`of crosslinked
`bonds. This
`polymer
`chains which mechan¡cally traþ the particle.
`this mechanism, which is not
`very well understood,
`the
`electmstatic
`interactions between the particles
`and the
`polymer do not play an imþortant role.
`
`In
`
`IY-5-2 Two-polymer-component
`coagulation systems
`The sequential addition of two polymers of opposite char-
`very good coagulation to be achieved.
`In þrac
`ge allows
`a cationic þolymer
`low or moderate molecular
`of
`tice,
`weight is ßrstly intmduced into the solution.followed by on
`anionic polymer of high molecular weight.
`
`cationic polymer
`low-molecular-weight
`is adsorbed
`The
`onto the þarticle to form cationic regions onto which the
`high-molecular-weight
`anionic polymer may be ßxed.The
`anionic molecular chain tends to uncoil
`in the solution due
`to the ef¶ect of charges of
`type carried by the
`the same
`particle. Eventually the chain
`is adsorbed onto other par-
`via bridging.
`ticles
`
`Figure 7
`
`- Two-component coagulation
`
`+
`
`+ M
`
`+
`
`-
`
`+
`
`+
`
`+
`
`+
`
`is
`
`imþortant for
`a slight excess o¶ cationic polymer
`to
`it
`is added.I¶it
`remain in solution when the anionic polymer
`the polymers can react with
`each other
`does not,
`in the
`liquid phase
`and (orm a gel.
`
`lY-5-3 Microporticulate systems
`Microþarticulate
`systems generally involve a cationic poly-
`mer and ßne inorganic anionic particles (bentonite, silica,
`etc.).
`
`They allow small,
`very strong.
`retain water.
`do not
`
`flocs to be obtained which
`
`SNF IKeBNK
`
`Page 14 of 57
`
`

`
`14 Coagulation andflocculation
`
`IV-6 Efficiency of flocculation
`and coagulation
`and flocculation is essential-
`o¶coagulation
`The eff¡ciency
`ty measured by the size of
`the flocs and their characteris-
`flocculated or coagulated matter in
`the amount
`tics,
`of
`suspension and the turbidity of
`the supernatont
`liquid.
`
`charac-
`These various parameters depend on the specific
`teristics o¶the flocs, and also on the seþaration þrocesses
`In order to measure the efficiency
`flocculation,
`used.
`of
`it
`therefore necessary
`tests according to the
`out
`to carry
`is
`seþaration þrocess employed.
`
`I gives the main characteristics of
`Table
`separation processes:
`
`flocs for various
`
`Table I
`
`Separation
`
`Characteristics of
`
`the flocs
`
`Filtration
`
`Sedimentation
`
`Centrifuging
`
`Flotorion
`
`Porous, strong, permeable
`Dense, strong,
`large, uniform shape,
`minimal þorosity
`Strong, dense,
`Low density, strong uni¶orm size,
`
`large
`
`large
`
`.
`
`..
`
`.
`
`.
`
`..¾uq.Jahdde /¾Lvurm £leccid<uinnfoodadan
`
`.
`
`IV-7 Parameters having an
`influence on the efficiency of
`flocculation and coagulation
`o¶coaguÏation and floccuÏation depends on
`The efficiency
`many parameters
`relating to
`the particles,
`the polymers
`used and the solution to be treated,
`
`have appeared on the subject, par-
`studies
`To date, many
`ticularly aiming to provide simplified models which allow
`extrapolation.
`
`Without attemþting to give
`the þarameters
`aÏI
`of coagulation and flocculation,
`influence the efficiency
`following are the main
`ones.
`
`that
`the
`
`the particles
`Influence of
`IV-7 I
`flocculation occurs
`individual þarticles smaller
`Usually,
`¶or
`I 00 µm) gene-
`than 50 µm. Large particles (greater
`than
`flocculate since the collision rates are too low.
`rally do not
`the polymers to become fixed to their sur-
`for
`is difficult
`it
`faces during collision and the rate o¶breakage of
`the flocs
`formed is very high.
`
`large particles
`flocculation
`place
`take
`can
`of
`However,
`using suitable polymers with a very high molecular weight.
`
`Depending on their nature and their concentration,
`floculation o¶susþended matter is:
`
`the
`
`the flocs are separated and o¶
`- Either dif¶use,in which all
`different size.The large flocs settle rapidly, leaving
`the finer
`flocs and microflocs in suspension,
`these being unable to
`leave a settiing tank via its overflow.The
`settle
`and often
`flocculation
`times
`about
`long-between
`I and 15
`are
`minutes;
`
`in which the flocs are o¶ similar size
`- Or homogeneous,
`leaving a clear
`interstitial
`and settle
`at
`the same
`rate,
`water.
`
`Page 15 of 57
`
`

`
`+
`
`+
`
`+
`
`+
`
`+
`
`..
`
`in the case of clays for example,
`the flocculation is dif¶use
`¶or a concentration o¶ less than about 2 g/I and homoge-
`type (or a concentmtion of about 2 to 5 gli.
`neous
`
`Figure 8
`
`- Filter effect
`
`Above a certain
`concentration,
`flocculant-susþension
`mixing no longer occurs and no floc appears.
`
`4
`
`The þarticle concentration in the suspension has an ef¶ect
`on the nature o¶the phenomeno involved.
`In general
`it
`is
`low particle concentrations
`that at
`the dominant
`¶ound
`charge neutmlization, whereas,
`phenomena
`involve
`¶or
`the þhenomena o¶adsoption and
`higher concentrations,
`bridging are dominant.Moreover,
`the flocs formed with a
`high þarticle concentration
`are stronger and contain a
`higher concentration of suspended matter.
`
`2 influence of the polymers
`IY-7-
`The nature of
`the polymer
`the main element
`in floccu-
`is
`three main chamcteristics are involved
`lation.
`In this case,
`the molecular weight,
`concentration
`and the
`ionic
`the
`charge.
`
`is greater
`ofthe þolymer
`the eißciency
`In genemí,
`the lon-
`its molecular chain,
`the chain length deþending on the
`ger
`molecular weight and on
`the spatial conßgumtion of
`the
`molecule.The longer the chain,
`the greater
`the possibiti-
`is
`ty o¶ creating bridging and the smatier
`the amount o¶
`þolymer used for
`In addition, high-mole-
`the same
`result.
`cular-weight polymers can have a secondary ef¶ect*the
`ßl-
`in which an unflocculated
`particle
`becomes
`ter
`ef¶ect,
`trapped
`floc mesh. The structure
`the
`o¶ the
`chain
`in
`an important
`(linear, branched or crosslinked) also plays
`role.
`
`Untfoccurated partide
`
`SNF ÏÑWW:WlR
`
`Page 16 of 57
`
`

`
`16 c ...
`
`.....
`
`is
`
`the molecular chains must
`not be too long as
`However,
`limited by problems o¶dif¶usion in
`their efficiency
`the
`solution and o¶ steric hindrance. Furthermore,
`increasing
`length has the ef¶ect of
`increasing the viscosity
`the chain
`o¶the solution and the time required to dissolve the poly-
`mer.
`
`and dissolution problems
`These polymer
`also
`dif¶usion
`to be used (the amount
`depend on the necessary
`dosage
`of polymer per
`tonne of dry matter).The
`appearance o¶
`floc allows the
`right dosage
`to be determined.
`the
`For
`a matt apþearance indicates good
`example, on a
`filter,
`flocculation, whereas a
`shiny appearance indicates that
`too much polymer has been added.
`
`in practice,
`a high or moderate dosage (polymer quan-
`for
`tities o¶between I kg and 10 kg per tonne of dry matter
`for municipal sludge),
`floc porticles
`the
`size
`o¶ the
`related to the molecular weight o¶ the polymer.
`directly
`The higher
`the molecular weight,
`the larger
`the floc. On
`the other hand,
`low dosages, polymers of moderate
`for
`molecular weight give better
`results because of
`the poor
`mixing of high-molecular-weight
`polymers and their
`ten-
`to retain unflocculated particles.
`dency
`
`is
`
`is
`
`the þolymer
`influence
`charge on the
`The
`flocs
`of
`the medium.
`expressed in relation to the ionic demand of
`Weaker charges give
`flexible flocs,
`good shear
`having
`their filtration properties are not exceþtional.
`strength,
`but
`On the other hand,
`a moderate or stronger charge gives
`better
`filtration
`properties,
`obtained are
`but
`the
`flocs
`more sheor-sensitive.
`
`case consists
`
`a high-pres-
`flocculation in
`One particular
`of
`be present
`the polymer must
`sure centrifuge.
`In this case,
`the entire amount of studge to allow
`the ¶ree form over
`in
`the initial
`both initial
`flocculation and re-flocculation after
`flocs have been sheared. In this case, any excess polymer
`must not produce a sludge
`redispersion ef¶ect.
`
`IY-7-3 Influence of polymer mixing
`in the solution
`is mixed in
`The conditions under which the polymer
`the
`solution are fundamental
`to achieving good coagulation
`and flocculation.
`
`Since the adsorption reactions are irreversible and
`very
`the quality of mi×ing must
`be high enough to allow
`rapid,
`of the polymer
`rapid diffusion
`the susþension.
`in
`Moreover,
`since the
`polymers
`are generolly
`used in
`concentrated form and in small quantities,
`they must
`be
`the medium.
`distributed uniformly throughout
`
`compromise there¶ore has to be found
`An experimental
`so that, depending on
`the points at which the polymer
`is
`injected, the quality of mixing is satis¶actory without shea-
`ring the flocs which are forming. Because, above a certain
`the flocs become very shear-sensitive.
`size,
`
`intrinsic shear strength and the shear
`their
`of
`Because
`rate in the medium, the flocs can break up and become
`smaller
`flocs or even individual particles. Over
`time,
`an
`equilibrium is established
`between the ¶ormation and
`disappearance of
`the flocs.
`
`is also important
`The hydrodynamic state
`the soÏution
`of
`for mi×ing. Flocculation gives good results
`faminar or
`in
`turbulent-flow.
`smaller
`the
`flocs
`result
`due
`latter,
`In
`to
`the interim state,
`sheoring. In
`the performance
`is unpre-
`dictable.
`
`Page 17 of 57
`
`

`
`IV-7-4 influence of the pH and
`the temperature
`of the solution
`We have seen that
`the pH of
`the solution has a direct
`ef¶ect on the behaviour of
`the polymer chains.
`It can oIso
`have other effects:
`
`the solution allows metal hydroxides
`Adjusting the pH of
`to be precipitated,
`interfere with
`and these may directly
`flocculation,
`for example by capturing the colloids.
`
`and therefore the ionic charge of
`Hydmlysis,
`depends on the pH.
`
`the polymer,
`
`Strongly anionic polymers
`basic
`ef¶ective
`very
`are
`in
`as good in acid
`medium, but
`their per¶ormance is
`not
`medium because the
`carboxylate/carboxylic
`¶unctional
`in such a medium. Nonionic or
`groups
`do not dissociate
`moderately cationic polymers are the best per¶ormers in
`acid medium.
`
`the solution directly
`temperature
`of
`The
`o¶ the reactions involved
`kinetics
`and the activity
`colloids.Thus,
`towering the temþerature reduces
`tion.
`
`influences
`
`the
`
`the
`of
`floccula-
`
`IY-7-5 Influence of the organic nature of the sus-
`pension
`important
`regarding the suspension is
`factor
`A final
`its
`organic nature.
`In general, the more organic the nature of
`the suspension the greater
`the cationicity of
`the polymer.
`Conversely, anionic polymers are more ej¶ective
`inorga-
`nic solutions.
`
`in
`
`IV-8 Advantages of synthetic
`COBgulânÍS
`for their higher unit cost
`Well known
`than inorga-
`nic substances,
`organic polymers prove,
`in many
`cases, to be more economical
`to use than inorga-
`because of their
`following specific
`nic substances
`advantages:
`
`- The amounts needed are generally I 0 times
`inorganic substances;
`those of
`
`lower than
`
`increase the amounts of solid matter to be
`- They do not
`and there¶ore help to minimize the cost of
`trea-
`removed
`ting the residual sludge;
`
`-The flocs obtained using organic polymers have a higher
`shear strength than those
`formed using
`inorganic sub-
`inter-þarticle
`bridging
`resulting ¶rom stronger
`stances,
`elastic bonding;
`
`inorganic coagulants are not
`- The flocs obtained using
`very compressible.They there¶ore take up more space on
`a filter medium and raþidly increase the head loss;
`
`- Organic polymers are less sensitive
`to pH variations and
`can therefore be used for
`treating a greater
`variety
`of
`water types;
`
`- Organic þolymers help to reduce the amount of trivalent
`salts dissolved in the water (in particular,
`there is
`fear o¶
`aluminium because o¶Alzheimer's disease);
`
`a
`
`- Synthetic
`
`polymers can be used together with inorganic
`the organic polymers mechanically rein¶orcing
`substances,
`the structure ¶ormed by the inorganic substance.
`
`Page 18 of 57
`
`

`
`18 Water solublepolymers
`
`-
`
`V-1 Coagulants
`The two main characteristics of a coagulant are:
`a very high cationic
`charge,
`to neutralize
`the
`negative charges of the colloids
`- a relatively low molecular weight,to allow rapid
`diffusion in the medium and around the particles.
`
`Three large families of products are used, namely
`quaternary polyamines, polyDADMAC and
`dicyandiamide resins.
`
`V-l-I Quaternary polyamines
`The condensation reaction of epichlorhydrin with a pri-
`mary or secondary amine, usually dimethylamine,
`þro-
`a polymer of moderate molecular weight
`in which
`duces
`the nitrogen atoms are in quoternized form:
`
`all
`
`CH.,
`
`CHa
`
`CH,-CH-CH,C1 +
`
`HN
`
`-þ
`
`(CH,-CH-CH,-N*)
`
`Ci
`
`O
`
`CHa
`
`OH
`
`CH3
`
`Epiditorhydra
`
`Dimelhylamine
`
`Polyamine
`
`of monomer
`the addition
`Controlling
`the molecular weight
`to be varied
`allows
`
`into
`
`the
`
`reactor
`
`The addition o¶þolyamines allows the branching and total
`the chain to be controlled.
`Ïength
`of
`
`Polyamines
`nic charge is
`
`from other polymers because the catio-
`differ
`on the main chain.
`
`Such polymers have the following characteristics:
`- Molecular weight between /0,000 and /,000,000
`- Liquid form with 40 to 50% concentration
`- Cationic site on the main cha