state of the art electroflocculation - j koren

7/23/2019 State of the Art Electroflocculation - J Koren

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T R O F L O C C U L T I O N

S t a t e o f t h e A r t E l e c t r o f l o c c u l a t i o n

J . P .F . K o r e n a n d U . S y v e r s e n

Ost fo ld Rese arch Foundat ion PO Box 276 N-1601 Fredr ikstad

orway

T h e e l e c t r o f l o c c u l a t i o n p r i n c i p l e h a s b e e n k n o w n s i n c e t h e b e g i n n i n g o f t h e c e n t u r y , b u t u n t i l

r e c e n t ly i t h a s n o t b e e n u s e d i n i n d u s t ri a l a p p l ic a t i o n s . T h e ' P u r i f i e r ' d e s c r i b e d i n th e p a p e r i s a n

e l e c l r o fl o c c u l a t io n u n i t w h i c h c a n s e p a r a t e o i l, o r g a n i c s u b s t a n c e s a n d h e a v y m e t a l s f r o m w a t e r . I t

i s m o s t c o m p e t i t i v e w i t h c o n c e n t r a t i o n s o f l e s s t h a n 5 0 0 0 p a r t s p e r m i l l i o n o i l o r o r g a n i c

s u b s t a n c e s i n w a t e r . T h e p a p e r d e s c r i b e s t h e m a j o r w o r k i n g p r i n c i p le s o f t h e ' P u r i f ie r ' .

O iLpolluted water and water polluted with other organic

substan ces i s a problem in many di f ferent indust r ies .

Demands from the authorities and general public for a cleaner

environment will increase, and the a uthorities might reduce the

legal effluent concentrations to 20 mg of organic substances per

litre of effluent. When the effluent is characteri sed as ha zard ous

waste, it is illegal to drain it into the sewer. It might only consist of

0.5 oil, while the rest is pure water. These huge volumes of low-

conce ntrat ion oily waste are ex pensiv e to treat. If the oil could be

separated from the water i t would be much less costly to treat the

oily waste, beca use of the lower volume. The oily sludge can

probably be incinerated, and the wate r reused in the industrial

process with a reduction in the cost of new process water.

The electroflocculation unit is capable of separating man y kinds

of organic sub stan ces and heavy metals in addition to oil. The

degree of separ ation is in most cases above 99 , and the powe r

consump tion is abou t 1 kWh/m 3 of wastewater. Current units can

treat about 1 m:3/h of wastewater in a continu ous process. The best

results are when the wastewater contains 5000 ppm organic

substances or less.

H i s t o r y

Electrolytic pr ocesses to separate oil in wastewater were described

in the patent literature as early as 1903. The process was used to

txeat condensed water from steam engines, before it entered the

steam boiler as feedwater. The unit used iron sheets as the anode

material; the iron was oxidised during the process, and had to be

replaced after a while. The electrolysis cell o~erated with a

potential of 150 V and with a fairly high c urrent. [ ]

This process was fur ther developed by Weintraub, Gealer

Golovoy and Dzieciuch into a c onti nuou s proces s to clean oily

wastewater from metal-cutting, forming, rolling and finishing

~,perations. An electrolytic cell which can treat 3.8 1/min of

wastewater was designed and patented in 1980. The wastewater

which was fed into the unit contained from 300 to 7000 mg oil/litre

of water. The processed water c ontained less than 50 mg/l for 90

,)f the time, and less than 25 mg/l for 83 of the time. The unit can

be improved to reach an effluent oil concentration of 10 mg/l. The

power co nsum ptio n was calculated to be 1.6 kWh/m3. I11

One of the first expe rime nts with electroflotatio n was in 1911,

1 eating domestic sewage in the United States. This method has not

become generally used because the electrodes tended to scum after

a while and, beca use o f this, t he efficien cy decreas ed with ti me. [21

Flotation processes are used extensively in the mining industry,

In 1904, it was propo sed for the first time to use electrolysis to

make gas bubble s to ' f loat ' minerals. The process was used in some

mines in Broken Hill, Australia. However, the operation was not

successful, because the power consumption was too high and

becaus e the technology was n ot well enou gh developed. [al

In 1946, Rivkin e t a l [31 obtained a patent for a method for

(,lectroflotation of ore. They designed several laboratory-scale

~,lectroflotation cells, which gave an improved flotation rate

(ompared to other flotation techniques. This method is not

repor ted to have been taken into commercia l use by the

industry. [a] Other ex per imen ts with electrolytic cells have been

reported, but i t appe ars th at electroflotation of minerals is sti l l at

the laboratory/experimental stage. This is because only a l imited

amou nt of research has been done on the mechanism s and the

design of the cell. lal

Kaliniichuk e t a l have described an electroflocculation unit

which ca n be use d to sepa rate an o il-in-water emulsio n. 14] They

achieved a degree of separatio n of more than 99 with a power

Filtration Separation

con sump tio n of 0.48 kWh /m 3 of water, bu t thc y used a residenc(.

time of 10- -20 rain. [41

E l e c t r o f l o t a t i o n

In flotation processes, air or gas is bubbled through a liquid

containing particles which float or are emulsified in the water, The

process consists of four basic steps: (1) gas bubble generation, (2)

contact between gas bubble and oil drop, (3) gas bubble

adsorptio n on the surface of the particle and (4) the gas bubbles

and oil drop s ris ing to the surface. ['~] At the surface a layer of foam

will be created. This foam consists of gas bubbles and the flotated

particles, an d can be removed by skimming. The rate of flotation

depends on several parameters, such as the surface tension

between the water, particles and gas bubbles; the gas bubble

diameter; the size of the particles; the wat er's residence t ime in the

electrolytic cell and the flotation tank; the particle and gas bubble

zeta potentials; and the temperature,*-pH and particle size

distribution.

There are many different flotation methods. The conventional

process is to use a comp resso r to btow air through nozzles in the

bottom of the flotation tank. The proble m is the distribution of the

air bubbles, and to make small enough bubbles. Small gas bubbles

are more efficient than larger gas bubbles, since they have a larger

surface area per unit volume of gas. Smaller gas bubbles also have

the advantage that they have lower buoyancy, and so will have a

longer residence time in the electrolyte. This increases the

possibility for collisions between bubbles and oil particles.

Another method is dissolved-air flotation, which gives a better

bubble distribution in the water. The disadvantages is that i t is not

a continuous process, and it is difficult to control the bubble flux.

During the process air is injected into the water under pressure;

when the p ressur e is released, the water is supersa turat ed with air,

which is released as air bubbles. I6] This is the same proc ess th at

happ ens when a bottle of carbonated water or beer is opened.

A method which follows the same principle, but which uses a

very low pressure, is vacuum flotation. The water is saturat ed with

air at atmospheric pressure, and when a vacuum is applied, air

bubb les will be released. 16] This proc ess h as the same adva ntag es

and disadvantag es as dissolved-air flotation.

Electroflotation is a continuous method. The bubbles are

generated by electrolysis of water; the water flows between two

electrodes, and is reduced to hydrogen at the cathode and oxidised

to oxygen at the anode. One advantage is that the gas bubbles

generated are essentially at the same, very small size. However, the

power cons umptio n can be high if the process is not well designed

and optimised. Another advantage is that i t is easy to adjust the

gas bubble flux, by varying the current across the electrodes. The

distribution of the gas bubbles is also good, because the bubbles

are produce d over the whole area of the electrode.

E l e c t r o p r e o i p i t a t i o n

Electroprecipitation is a flocculation process where the flocculat-

ing agent is ions of metal which are precipitated from the anode.

The metal ions will settle in the electrolyte, but on the way down

they collide with particles in the electrolyte, and adsorb onto the

surface of these particles. The best anode material is iron or

aluminium, because they give trivalent ions; most oth er cheap and

easy accessible metals give bivalent ions. Trivalent ions have a

higher abili ty to adsorb onto particles in the water than bivalent

ions, because they have a higher charge density.

The mechanism which breaks down emulsions in the water

phase is not fully understood. Weintraub e t a l suggested that the

Febr uary 1995 0015-1882/95/US 7,00 ~ 1995 Elsevier Science Ltc~ 153


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breakd o~ of emuls ions i s b rought about wi th the ass i s tance o f

hydroxyl radicals which are generated during ferrous-ion oxida-

tion. The reaction sequence is:

Fe 2+ +0 2 + H + = Fe a+ + HO2 (a)

Fe 2+ +H O' 2+ H ~ = Fe ~+ + H202 (b)

Fe 2+ + HzOz --~ Fe n+ + HO + OH - (c)

Fe e~ + HO --~ Fe 3~ + OH ~ (d)

The fe r rous ion /hydrogen perox ide so lu t ion tak ing par t in

reactions (c) and (d) is recognised as Fenton's reagent , and is a

powerful oxidising system. The emulsion is destabil ise d by both

oxidative destruction of the chemical emulsif ier and by neutral isa-

t ion of t he emul sion/ dropl et charge. TM

No mechan ism has been suggested with alumin ium as the

anode. Aluminium ions are very unstable, and i t is suggested that

aluminium ions react with hydroxyl ions and make a network as

soon as they are released from the anode. The network of

alumini um hydroxi de wil l adsorb onto colloidal part icles. Collob

dal part icles are defined as part icles which in the dispers ed state

have an extension in at least one dimension of between 1 nm and 1

Hm. The upp er l i mit is not dist inct , s ince part icles which are larger

than 1 Hm are also treated as colloidal part icles if they have

prop erti es like co lloidal particles . 17]

The network of aluminium ions is buil t up from a chain with

three hydroxyl ions per aluminium ion. The chains can be several

hundred ~ngstroms long, but only a few part icle diameters thick.

The chains are created by a condensat ion polymer reaction

mechanism. The process depends on pH and temperature to create

the correct crystals. At 25C the pH in the wa ter mu st be between 4

and 10, and at 100('C between 3 and 7, in order to create large

cKystals. Outside these pH ranges the afuminium ions will react to

make less comp lex c ompo unds with h ydrogen a nd oxygen. [s]

l e c t r o f l o c c u l a t i o n

Eleetroflocculat ion is a combin ation of the processes of electro-

f lotat ion and e lectroprecipitat ion. Our eleetrofloeculat ion unit

consists of an electrolytic cel l with an alumi nium an ode and a

stainless-steel cathode. The anode mus t be more easi ly oxidisable

than the c atho de to give the correct effect. Balmer and Foulds [1

tried many different electrode materials, such ms iron, steel, copper,

brass, zinc, alloys of aluminium, bronze and phosphor bronze. All of

~hese mate rial s produced enough flocs, and gave a high degree of

separat ion. They concluded that the cheapest and most easi ly

accessible electrode materi als should be used.

An electrolytic cell can be des igned in ma ny di fferent ways. [m}

Here we wil l discuss a specif ic unit , which ha s been designed and

pate nted by Jan Sundell; this uni t is called the 'Purifier' . The

distance between the electrodes is 3 ram; this distance is an

impor tan t des ign var iab le when i t comes to op t imis ing the

~Jperat ing costs of the unit . The oper at ing costs are depen dent on

l he power consumptio n, which can be expressed as

P = U x I (1)

where P is the power consum pti on (W), U is the voltage IV) and I

is the cur rent (A). Using Ohm's Law (U =/ ~ I, where /~ is the

resistance in ohms), i t is also possible to rewrite Eqn. 1 as

P = R [2 (2)

U ~

P = ~ (3)

The relat ionship between current and power consum ption is shown

in Eqn. 2, and a cha nge in curre nt will chan ge the powe r

consumptio n in the second power. The amount of gas which

evolves at the electrodes is dependent on the c urrent f lowing across

he electrodes.

To reduce the power consumption without changing the current

and the degree of separat ion, one can reduce the resista nce in the

electrolyte. Reducing the distance between the electrodes or

increasing the conductivi ty of the electrolyte wil l reduce the power

,.onsumption without changing the degree of separat ion, because

he current is not changed. Ohm's Law states that the power

consumpt ion wil l decrease ms the d istance between the electrodes

is reduced and as the conductivi ty of the electrolyte increases.

The eleetrolyte 's conductivi ty wil l affect the power co nsumpt ion

in the same way as the distance between the electrodes. According

to Ohm's Law, a high conduc tivit y in the electrolyte and a smal l

5 4

distance between t he electrodes gives a low power consump tion. I'1

In some types ofwa stew ater the conductivi ty is too low, and i t is

necessary to add some sal ts to increase the numbe r of dissolved

ions in the electrolyte. The simplest met hod is to add table sal t

(NaGl), but it has also been reported that 0.01N CaC12 has been

used to i ncrea se the conduc tivi ty of the electrolyt e. U]

There is an opti mum ar rang ement with a certain power

consumption and a certain degree of separat ion. When the current

in the electrolytic cel l is increased, the gas bubble f lux increases;

this increas es the s eparat io n effect . However, when the concentra-

t ion of gas bubbles is increased, the possibi l i ty hat two gas bubbles

coll ide also increases. This reduces the separat ion effect s ince

larger gas bubbles are less effect ive than smaller gas bubble:r ,

because they have a smalle r surface area/v olume rat io. In addit ion,

gas bubbles have a lower conductivi ty than the electrolyte; this

increases the power consumption.

When the gas bubble concentrat ion increases, the result is thal

the degree of separat ion increases as the curr ent increa ses up to ~

certain level . The concentr at ion of the gas b ubbles gives a large

contributi on to the electrolyte resistance, and eventually too many

of the gas bubbles wil l coalesce. The degree of separa t ion wil l then

slowly decre ase as the c urre nt across t he el ectro des increases. U~I

At a certain point , increasing the power consu mption wil l no longer

affect the degree of separat ion.

T h e e l e c t r o d e r e a c t io n s

The anode and cathode reactions are as fol lows:

2H20 + 2e -= H2(g) + 2OH (cat hode ) E = -0 .8 3V

2H~O = Oz(g) + 4H + + 4e - (an ode ) E = +0 .4 0V

Alia) = Al 3+ + 3e (an ode ) E = -- 1.66

2Alia) +6 H2 0 = 3H2(g) +6 OH +2 AI :~+ (Tot al) E = +0 .8 3 \

Hydrogen gas will evolve on the cathode, and oxygen gas will evolve

on the anode; oxygen gas wil l only evolve at high current densi t ies

It is an adv antage th at hydroxyl ions are developed at the cathode.

because they maint ain the pH in the electrolyte. To create the

correct alumin ium complexes, the pH mus t be close to 7.

There a re many mecha nisms which a re a t work in the

electrolytic cell . These include an electrophore sis mechanism,

which makes the negatively charged oil part icles at tracted to the

anode. This results in a faster f locculat ion than would be the case

with c onven tiona l flocculation or flota tion meth ods. I 'll

G a s b u b b l e f o r m a t i o n

The gas bubbles which are created by electrolysis have an

impor tant function in the sep arat io n process. Reay and Ratcl iff

found th at the rate of f lotat ion of polystsTene ~art i cles is

depen dent on the gas bubble- and part icle diameter . [~2] The rate

of flotat ion at a con sta nt gas rate var ies as d 2 rt~ and d.-i~- This

~ cte O~oole

means th at the rate of f lotat ion is at i ts highest when the part icles

are as large as possible and when the gas bubbles are as small as

possible. Coll ins and Jame son found that the rate of f lotat ion of

polystyrene latex part icl es with a di amete r of 4 - 20 /zm varied as

l ~ 5 t i t e . [ 1 2 1 They also found that the ex pone nt showed l i t t le

pe'r~dence on the charge on the particle, but that the actual

rate of f lotat ion was strongly influenced by the part icle charge,

which was varied in the 30--60 mV range.

There is a specif ic rat io between the sizes of the pa rt icles and

the bubbles where there is a higher probabil i t y ( if direct coll is ions

between gas bubbles and part icles. I lzl A direct coll is ion makes the

gas bubble adsorb onto the part icle , and many direct coll is ions

duri ng a shor t tim e give a high rat e of flotation.

If a collision between a parti cle and a gas bubble is to be

successful , the energy barrier represented by the water f i lm

between the actual part icle and the actual gas bubble must be

overcome. The coll is ion velocity and the par t icle mass determi ne

the energy which is available during the coll is ion; larger part icles

hit the gas bubbles with a great er force than smaller gas bubbles.

The relat ive velocit ies of a part icle and a gas bubble increase with

the difference in their dimensions. If the gas bubble hi ts a relat ively

small part icle , the force from the coll is ion wil l make the part icle

rebound from the gas bubble. The highest prob abil i ty for a

successful coll is ion is when t he gas bubble coll ides perpendic ular

to the part icle surface. There are distr ib ution curves available Ibr

air bubbles and mineral part icle diam eter to f ind the optim um

flotability. This is co mmon in th e mini ng industry . U:8

Collins and . lameson H 2] repor ted that the gas bub ble (:ollection

Eebruary 1995 F ~ l l r a t i o n S e p a r a t i o n


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efficiency for bubbles less than 100 ]~m in diameter can be

described

b y

(dP~ ~i~z~N (4)

E c = \ d b u b b b /

wher e N - 1.90 whe n Pparticl~./pfluid = 1.0, and N- 2.05 when

P~,a,-ti,:t,~/Pfl~i,t

= 2.5. This assu mes that the strea m around the

sphe re follows Stokes' Law for a flow arou nd a rigid sphere; t hat

electrical interactions between bubbles and particles do not have

any effect on the particle trajectory or on E(., and that bubble

motio ns are no t affected by the pre sence of the particles, p2]

T h e s i z e o f t h e g a s b u b b l e s

The fol lowing condi t ions af fect the gas bubble d epar ture

di am et er :[~4]

[] Gas bubble contact angle.

[: J Catho de surface morphology .

~:] Current density.

{~ Polarisation potent ial.

E] Gas bubble charge.

Parameters which are fixed or which are impractical to adjust in

order to obtain fine-sized gas bubbles are pH, temperature, reagent

(:,mcentration and the electrode material.

Khosla e t a l . Ua] and Glembotskiy e t al. H51 have rep ort ed th at

The gas bubble size decreases with increasing current density.

Glembotskiy

e t a / .

H5] have also found that the hydrogen gas bubble

size increases with increasing temperature, and that the smallest

gas bubbles were formed at pH 7. Khosla e t a / . U4I have also

successfully used pu lsed electrolysis to genera te very small gas

bubbles; with a pulse cycle time varied in the range of 30 ms and

the c urre nt de nsity varied fr om 2 to 0.5 A/m 2, they obser ved an

m creas in num ber o f sm a l l gas bubb le s (< 10- -1 5 m ) .

()thers(~,,~Zl have reporte d gas bubble diamet ers of 20 m durin g

,qectroflotation with a constant current density.

G a s b u b b l e f o r m a t i o n o n t h e c a t h o d e

] ' Irate are three basic steps in tbe development of gas bubbles:

mlcleation, growth and detachment. Nucleation occur in energy-

fiwourable places like pits and scratches. These places have a

higher voltage than the rest of the cathode surface (see Reference

t 6, p. 305). Khos la e t a l . [14J reported that with pulsed electrolysis

I he energy-favourable places are less importa nt as nucleation sites,

and that nucleation is more uniform over the cathode surface.

Growth is driven by expansion caused by a high internal

pressure and tra nspor t of dissolved gas through the ga s/liquid

interface beca use of super sat m~t ion of gas in the electrolyte. Hal

Another mechan ism which make gas bubbles grow is coalescence.

Fhis occurs when two gas bubbles touch, and coalesce into a single

Ras bubble. Sides (Reference 16, p. 309) described a mechanism

called radial specific coalescence, and obsel~ced that smaller gas

bubbles moved radially towards a larger gas bubble and coalesced.

Another mechanism which make two gas bubbles coalesce is

when one gas bubb le rolls across the.cathode surface, and coalesces

with every gas bubble which comes into its path. This gas bubble

will often grow larger than necess ary before it detaches. Sides (Ref.

16, p. 312) repor ted t hat wh en the electrod e was tilted a few

degrees from the horizontal, the bubbles coalesced and made a

large front of gas bubbles, which 'scavenged' other bubbles in its

path. This is unfavourable for the rate of flotation, because gas

bubbles with smaller diameters are more effective than gas bu bbles

with larger diameters.

The third step is detachment. Its occurence is dependent on the

bubble contact angle and the size of the gas bubble. Pulsating

electrolysis gives the gas bubbles a shock, which makes the gas

bubbles detach earlier than they would without the pulses. A

surface-active substance in the electrolyte will reduce the surface

tension between the electrolyte, the surface of the cathode and the

gas bubbles, and make the gas bubbles detach sooner. Venczel (Ref.

16, p. 316) added gelatine, glycerine and beta-naphthochinolin to

the electrolyte; in most cases the bubble diameter decreased. The

reason suggested is that the surface-active substance results in

increased wettability of the electrode.

The 'Purifier ' reported here has been tested with soap in the

electrolyte. This test gave a higher degree of separation with oil-in-

water emulsions. The disadvantage is that a surf 'ace-active

substance works as an emulsifier and stabilises the oil emulsion,

but i t is probably possible to find surface-active substa nces which

increase the wettabili ty of the cath ode wit hout working as an

emulsifier for pollutants in the water.

T h e ' P u r i fi e r ', a n e l e c t r o f l o c c u l a U o n u n i t d e s i g n e d b y

J a n S u n d e l l

Before the wastewater enters the electrolytic cell, it is coarsely

filtered in a hydrocyclone. This removes the larger particles, and

improves the total degree of separation. It was mentioned earlier

that ther e is a p robl em with the anode, which will tend to scum. [2}

This problem is solved in the Purifier. Jan Sundell has designed and

patente d a system which keeps the anode clean all of the time, and

makes the anode wear evenly.

In the electrolytic cell aluminium ions precipitate from the

anode a nd flocculate the unwa nted particles l ike oil, most kinds of

organic compounds and heavy metals. At the same time the

hydrogen gas bubbles which form at the cathode cause the

flocculated parti cles to float. The residence time of the wastewa ter

in the electrolytic cell is less than 1 s, but this depends on the flow

velocity of the water. The water flows into a se dimen tatio n tank,

where the residence time is short, but depends on the temper ature,

the concentration of impurities etc.

This process forms both a sediment and a layer floating on the

surface, which are removed at regular intervals. The sediment is

drained regularly, and the surface layer is skimmed off. The sludge

is dewatered in a filter, and the removed water is recycled into the

electrolytic cell. The sedimentation tank is tapped for clean water

at regular intervals.

If the w aste wate r conductivity is too low, it is necessary to add

W a s t e W a t e r

P u r e w a t e r

S l u d g e ~

W a t e r a n d

S a l t

. . . . . . ~ Reverse

O s m o s i s

' T

E l e c t r o l y t i c

Ce l l 1

_ I _ _ _

: ~ecyc led

Water

H y d r o C y c l o n e

7

i ly S l u d g e

Figure 1. Flowsheet for

the Purifier.

Fi l tration Separation F e b r u a r y 1 9 9 5 155


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Figure 2 . The Pur i f ie r un i t , Inc lud ing e lec tro ly t ic ce l l ,

s e d i m e n ta t i o n ta n k a n d p r o c e s s c o n t r o l s y s te m .

s od ium ch lor ide to increas e the conduct iv i ty . I f t he r ec ip ien t

cannot accep t s a l t water , i t wi ll be neces s ary to r emove the s a lt .

This is done w ith the use of a revers e osmos is uni t . The uni t

p roduces two s t r eams , one wi th pure water and the o ther wi th a

mix ture o f s a l t and water . The l a t t e r s t r eam i s r ecyc led back to the

electrolyt ic cel l for reuse of the sal t .

The Puri f i e r has ach ieved promin en t r es u l t s wi th the separa t ioH

of d i f f e r en t k inds o f po l lu t ion f rom water . Es pec ia l ly good r es u l t s

have been achi eved in the sep arat ion of oi ly emuls io ns , and i t ha.~

a l s o ach ieved a h igh degre e o f s epara t i on wi th s evera l k inds n i

o rgan ic s ub s tances and heavy meta l s . Tab le 1 g ives va lues whic lp

were ach i eved dur ing t es t ing o f the Pur i f ie r ( the ana lys i s wa:~

per formed by the KM Labora to ry in Kar l s t ad) .

The US company Envi ronomics has a l s o deve loped a p roces :~

which us es the e l ec t ro f loccu la t ion p r inc ip le , which has ach ieved

good r es u l t s fo r s epara t i on o f po lyaroma t i c hydroc arbons (PAHs )

o il , o rgan ic compounds and he avy meta l s f rom was tewater .

A c k n o w l e d g m e n t

This work has been f inance d by the Le t t en F. Saugs tads Fund .

R e f e r e n c e s

1 Weint raub , M.H., Gealer, R.L., Golovoy, ~ and Dziecioch, M.A.: Devel opment ol

electrolytic treatment of oily waste water', En~ironme~r.tal Progress, Februar~

1983, 2(1), p. 32.

2 Fukui, Y. and Yuu, S.: 'Colle('tion o f submi eron partic les in electro-flota tion'

Chem. Eng. ~'ci., 1980, 35, pp. 10 97 - 1105.

3 Mallikarjuan, R. and Venkat achal am, S.: 'Elektrof lotation A review'

[nternatmn al Symposium nn Electrochemistry in Mineral Metal Processing

(165th meet ing of the Electro chemic al Society), Cincinnati, Ohio, USA, May 1984:

pp. 233 -- 256.

4 Kaliniichuk, E.M., Vasilenko, l.]., Shchepanyuk , V.Yu., Sukhovcr khova, N.A. and

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T a b l e 1 . R e s u l t s f r o m t e s t r u n e w i t h t h e P u r i f i e r .

B e f o r e t h e A f t e r t h e D e g r e e o f E x a m p l e

P u r i f i e r , m g / I P u r i f i e r, m g / I s e p a r a t i o n

1 . O i l i n w a te r 3 5 0 0 . 3 9 9 . 9 C a r w a s h u n i t

2 . A t i p h a ts i n c o o l i n g w a te r 2 6 0 2 . 4 9 9 . 1 S h i p

A r o m a ts i n c o o l i n g w a te r 6 2 0 . 6 9 9 . 0

3 . L e a d , P b2 + 5 . 3 < 0 . 0 5 > 9 9 P r i n t i n g o f fi c e

C o p p e r , C u 2 + 1 1 0 1 . 2 9 8 . 9

Z i n c , Z n 2 + 1 6 0 0 . 2 2 9 9 . 9

T a b l e 2 . R e s u l t s f r o m E n v i r o n o m i c s I n c 1 9 9 3 ) .

Wastewater f rom Before Af ter sep arat ion , Degree of Type of

l au n dr y s e pa r at io n , m g / I m g / I s e p a r a t i o n c o m p o u n d s

3 . 4 0 . 0 7 9 9 7 . 7 P o l y a r o m a t i c

N a p h t a l e n e 5 . 7 0 . 2 40 9 5 . 8 h y d r o c a r b o n s

2 -b is

e t h y l h e x y l p h t a t a t e

3 , 4 < 0 . 3 3 > 9 1 (P A H s )

P y r e n e 3 . 4 < 0 , 3 3 > 9 1

F l u o r a n th e n e 3 . 4 < 0 . 3 3 > 9 1

C h r y s e n e

T o ta l o i l a n d g r e a s e 5 5 0 0 4 0 9 9 , 3 O i l f r a c t io n s

O i l a n d g r e a s e 4 0 0 0 1 0 9 8 . 8

P h e n o l 3 , 4 0 0 5 2 9 8 . 5 O r g a n i c

T S S 3 5 0 0

2 2

9 9 . 4 c o m p o u n d s

E th y l b e n z e n e 2 1 < 0 . 0 0 7 > 9 9 , 9 7

T o l u e n e 2 3 0 . 0 1 4 9 9 ;9 4

X y l e n e 1 6 8 0 . 05 1 9 9 , 9 7

C d2 + 2 5 . 6 < 0 . 0 0 1 > 9 9 . 9 9 6 H e a v y m e t a l s

P b2 + 4 0 0 0 . 0 3 9 9 . 9 9 3

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10 ]logan , P. and Kuhn, A.T.: 'Die

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12 Collins, G. L. and James on, GJ.:

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14 Khosla, N.K., Venkat achala m, S.

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15 Glembotskiy, V.A~, Mamakov, A..~

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156 F eD rua ry 19 95 F i l t r a t ion S e p a r a t i o n

state of the art electroflocculation - j koren

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