Remoção óleo com argila 0956-053x28962900023-2

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Pergamon 
PII: S09564)53X(96)00023-2 
Waste Management, Vol. 15, No. 8, pp. 623-628, 1995 
Copyright © 1996 Elsevier Science Ltd 
Printed in the USA. All rights reserved 
0956-053X/95 $9.50 + 0.00 
ORIGINAL CONTRIBUTION 
ORGANICALLY MODIFIED CLAY REMOVES OIL 
FROM WATER 
George R. Alther 
Biomin, Inc., PO Box 20028, Ferndale, M148220, U.S.A. 
ABSTRACT. When bentonite or other clays and zeolites are modified with quaternary amines, they become organophilic. 
Such modified bentonites are used to remove mechanically emulsified oil and grease, and other sparingly soluble organics. 
If the organoclay is granulated, it is placed into a liquid phase carbon filter vessel to remove FOGs (Free Oil and Grease) 
and chlorinated hydrocarbons. In this application the clay is mixed with anthrazite to prevent early plugging of the filter 
by oil or grease droplets. In batch systems a powdered organoclay is employed. Organoclay removes mechanically emulsi- 
fied oil and grease at 5-7 times the rate of activated carbon, or 50% of its dry weight. Oil and grease and other large spar- 
ingly soluble chlorinated hydrocarbons and NOMs (Natural Organic Matter) blind the pores of activated carbon (and 
ion-exchange resins), reducing its effectiveness significantly. It is therefore economically advantageous for the end user to 
prepolish the water before it enters carbon vessels. Operating costs can often be reduced by 50% or more. Copyright 
© 1996 Elsevier Science Ltd 
INTRODUCTION 
Oil and grease are commonly found in many process 
waters and groundwater. Oil that is found in con- 
taminated water can be classified into five areas: 
• Free oil and grease (FOG), which is oil that rises 
rapidly to the surface under calm conditions. 
• Mechanically emulsified oil. These are fine 
droplets ranging in size from micrometers to a 
few millimeters. These droplets are electrostati- 
cally stabilized without influence by surfactants. 
• Chemically stabilized emulsions: surface-active 
agents provide enhanced stability due to inter- 
action at the oil/water interface. 
• Chemically emulsified or dissolved oil: this 
includes finely divided oil droplets (5 p~m diam- 
eter), benzene and phenols. 
• Oil-wet solids. The oil adheres to sediments or 
other particulate matter in the waste water.1 
Types of oil found in water can include fats, lubri- 
cants, cutting fluids, heavy hydrocarbons such as 
tars, grease, crude oil, diesel oils; and light hydrocar- 
bons such as kerosene, jet fuel, and gasoline. 1 
As environmental regulations become more and 
more restrictive towards release of oil into waters, 
methods of removal need to be employed that 
RECEIVED 2 NOVEMBER 1995; ACCEPTED 3 APRIL 1996. 
remove low levels of oil at high efficiency and attrac- 
tive economics. 
Organoclays are employed to remove mechani- 
cally emulsified oil from water at concentrations of 
60 ppm or less. Applications for organoclays are 
cleanup of stormwater, boiler steam condensates, 
landfill leachates, ground water, boiler feed water, 
produced water from oil production wells, bilge water, 
wood-treating water, API oily water separators, 
degreasing operations, truck and heavy equipment 
wash, refinery and rendering operations wastewater, 
and other manufacturing process water. The two 
most common applications are: 
1. Pretreatment for activated carbon, ion-exchange 
resins, membranes, RO units and UF units, 
where the purpose of the organoclay is to 
increase the life and use of those media by pre- 
venting blinding and fouling. 
2. As a postpolisher for oil/water separators and 
DAF units. With the ever-tightening specifica- 
tions for release of oil and grease into waters, 
this use is becoming more prevalent. 
There are further advantages achieved by placing an 
organoclay media filter in front of air strippers and 
sand filters, K D F media and the like. Oils coat the 
plastic media in the air stripper, sand and so on, 
preventing proper functioning, a problem that is 
eliminated by the use of organoclay as a prepolisher. 
623 
624 G.R. ALTHER 
A coarser grained organoclay/anthrazite medium 
can be employed to remove occasional spikes of oil 
and other hydrocarbons. 
ORGANOCLAYS: WHAT ARE THEY? 
Bentonite consists primarily of the clay mineral mont- 
morillonite. The montmorillonite has ion-exchange 
capacity of 70-90 meq/g. By exchanging the nitrogen 
end of a quaternary amine onto the surface of the clay 
for sodium and calcium, the clay becomes organo- 
philic, i.e. its swelling in water is minimized. By choosing 
a long-chain quaternary amine, such as di-menthyl 
(di-hydrogenated) tallow ammonium chloride (12-18 
carbons) the clay will swell in organic fluids, such as 
diesel and jet fuel, gasoline, kerosene and others. 2 
This ability has resulted in their use in paints, 
adhesives, drilling fluids (oil-based drilling muds), 
oil-based foundry sands, printing inks, etc., where 
they act as thickeners and binders due to their rheo- 
logical properties. It has also been found that when 
organoclays are placed into water containing mechan- 
ically emulsified oil, greases, dioxenes, PCB, PCP, 
and other large chlorinated hydrocarbons (also small 
ones like vinyl and methyl chloride) the organophilic 
clay will remove these compounds by a partitioning 
process) The carbon chains from the quaternary 
amine, in the presence of water, will stand up per- 
pendicularly to the clay platelet (Fig. 1). 4 Smith 
e t al. 5 showed that linear absorption isotherms are 
similar to heptane-water partition coefficients in 
their experiments. Clays substituted with smaller 
cations such as tetramethyl ammonium chloride (TMA) 
showed non-linear uptake of benzene and other small 
aromatics from water, indicative of absorption onto 
the TMA-treated surface. Since we found that 
organoclays also remove chromate anions, a third 
process, anion-exchange with the chlorine end of the 
amine, seems to take place: Symons et al. 6 found 
that anion-exchange resins are well suited for the 
removal of TOC from water, and that they can be 
regenerated with sodium hydroxide/sodium chloride 
brine, further supporting this hypothesis. 
We found some chromate removal ability with the 
long-chain quaternary amines (C-18), but not to the 
same extent as with shorter chains (C-12) reported in 
the literature. Since commercial quats are a mixture 
of C-12 - C-22 amines, we propose that this anion 
exchange is due to the short-chain impurities. 
The long amine chains will dissolve into the oil or 
other hydrocarbon droplets, holding or fixing it due 
to Coulombic (electrostatic, van der Waal) forces. 
This activity takes place on the surface of the clay 
platelet (Fig. 1). Activated carbon, on the other 
hand, is a porous material where the organics are 
adsorbed into the pores. Thus, if an oil droplet is 
larger than the diameter of the pores, it will simply 
sit on top of that pore, preventing any further 
adsorption. Therefore, the capacity of the carbon is 
used up much more quickly, resulting in frequent 
changeout of the carbon at greatly increased cost to 
the end user. This problem is greatly reduced by 
placing the organoclay/anthrazite mix in front of the 
activated carbon vessel, resulting in cost savings to 
the end user of up to 55% (Fig. 2). 
In batch systems, powdered organoclays are 
employed. In filtration vessels, a granular organo- 
clay mixed with anthrazite is used. The purpose 
of the anthrazite is to help keep the pore spaces 
between the granules open. The unblended organo- 
clay would plug up as fast as carbon, negating its 
advantage. The organoclay/anthrazite mix is gener- 
ally applied when the concentration of emulsified oil 
is less than 60 ppm. It can remove as much as 50% 
of its weight in oil. Organoclay powder can remove 
up to 70% of its weight in oil. 
CASE HISTORIES 
1. The largest application has been at Hill Air 
Force Base in Utah (Fig. 3) where three organo- 
clay/anthrazite mix tanks protect fourgranular 
activated carbon columns. The water that is pro- 
cessed is wash water from jet plane cleaning 
OIL 
OIL OIL 
/oh /e\ 
r / / 
Pores~ 
Activated carbon Granule - 
Porespaces of activated carbon, 
blinded by emulsified oil. 
Clay Platelets, modified with 
quaternary amine, remove emulsi- 
fied oil on the clay surface. 
Activated Carbon downstream of 
Organoclay, ready to remove the 
more soluble compounds. 
FIGURE 1. Mechanism of oil droplet removal from water, and related problems, by activated carbon and organoclay. 
ORGANICALLY MODIFIED CLAY REMOVES OIL FROM WATER 625 
Millions Bed Cost/ 
Gallons Life 1000 Gallon 
Treated Days Treated 
I I I 
15. 
10- 
5- 
1 
FIGURE 2. Waste stream contains 25 ppm oil, flows at 5 gpm, 10 
hours/day. Removal efficiency for GAC is 10%, for organoclay/ 
anthrazite it is 50% of its dry weight. Cost reduction/gallon by 
using clay/anthrazite is 55%. 
. 
. 
operations and storm water runoff. Paint strip- 
ping, degreasing and electroplating operations 
generate hydrocarbons such as oil, grease, tetra- 
chloroethane, 1,1,2-trichloroethene, chloroform, 
methylene chloride, and heavy metals which are 
also removed by use of organoclay and acti- 
vated carbon. This system tends to last two 
years until changeout. 
Lead-containing rinse water: Trials showed that 
neither organoclay, activated carbon, or an ion- 
exchange resin were able to remove the lead 
individually; a combination of the three was 
successful and brought the waste water within 
compliance. The lead was organically bound. 
A foundry in Illinois had set up a water treat- 
ment system consisting of various settling and 
coagulation tanks, an oil/water separator, a 
sand filter, and a granular activated carbon 
filter. The purpose of the system is to remove 
oil, grease, phenolics and some heavy metals 
from the waste water. If the foundry used more 
than 1500 glad water, they would be out of com- 
pliance, resulting in fines, an occurrence that 
happened frequently. The sand in the sand filter 
was replaced with the organoclay/anthrazite mix; 
for several months now there have been no vio- 
lations of standards in spite of varying flow rates. 
4. A large laboratory conducted a test using air 
compressor condensate that contained auto- 
matic transmission fluid (ATF) oil which 
resisted all emulsion-breaking techniques, 
including acidification, heat, dilution or poly- 
mers. The material had a milky white appear- 
ance and on settling for 72 h had a very faint 
ring of free oil floating on top of the water and 
a milky appearance. The inflow concentration 
was 30,000 mg/l. After passing through an oil/ 
water separator, the sample contained 3300 mg/l; 
after the first organoclay/anthrazite vessel it 
retained 240 mg/l; after passing through the sec- 
ond vessel, 1 mg/1 remained. 
5. In another case in Alaska, ground water was 
contaminated with diesel fuel. Three tanks of 
activated carbon were set up in series. The car- 
bon lasted for 2 days when breakthrough 
occurred. After the carbon was replaced, three 
tanks of organoclay/anthrazite were placed in 
front of the carbon. This system lasted for 3 
months, or until the cleanup was finished. (it 
was not saturated at this point). The clay/ 
anthrazite removes the heavier chlorinated 
hydrocarbons, the carbon removes the volatiles. 
6. A laboratory trial showed powdered organoclay 
to be very effective in the removal of pesticides 
such as alachlor, diazinon, metolachlor, 2,4-D, 
trifuralin, 2,4,5-T, and others. Scientific litera- 
ture further supports these results, i.e. organo- 
clays remove acidic herbicides and pesticides. 7 
Influent 
1 
Air Flotation 
Unit 
Primary Collection 
Sump 
_ 
O:rgan~la~ 
Absorption /l ~ l .tt. Carbon CoLumns 
Columns ~ 1 
Discharge . ._l I I I 
'°s~w°r -1 chch I 
Back Wash Pump 
FIGURE 3. Design at Hill Air Force Base, Utah. Operation: electroplating, degreasing and paint stripping. Contaminants: grease, chlorinated 
hydrocarbons, oil: total: 10-50 ppm. Flow-through rate: 350 gpm. Cost reduction by using organoclay/anthrazite as prepolisher: 50%. 
626 G . R . A L T H E R 
7. A large national remediation contractor was 
contracted to remove hydrocarbons and poly- 
chlorinated biphenyls (PCBs) from the sediment 
of a creek bed in western New York State as 
part of a NYSDEC consent order. The contractor 
proposed and designed a system that resembled 
an environmental dewatering project with adsorp- 
tion treatment of the effluent process stream. 
The contractor designed a small wastewater 
treatment system that included two 7000 gallon 
• m u l t i - l a y e r media sand filters and two 7000 gal- 
lon activated carbon bed adsorbers. The creek 
bed sediment was contaminated with PCBs and 
hydrocarbons. The sediment dredged from the 
creek was lime stabilized and then passed 
through an 80 cubic foot (~ 2.2 m 3) plate frame 
filter press. The effluent from the filter press 
was then processed through the multi-stage 
adsorber system. 
The first multi-layer adsorber vessel had three 
layers. The layers were composed as follows: 1 
foot (30 cm) of a pea gravel over a retaining 
screen, then 4 feet (1.2 m) of grade 68 sand and 
on top of that 1 foot (30 cm) of organo-modi- 
fled clay. The organo-modified clay was used 
primarily for removal of the hydrocarbons, and 
secondarily to protect the activated carbon bed 
by extending its bed-life, allowing the carbon 
preferentially to adsorb the PCBs into its pore 
structure. Periodically, the clay/anthrazite medium 
is replaced as it becomes saturated with the 
hydrocarbons. Because the organoclay is the 
uppermost layer for the adsorber vessel, it was 
easy to remove the flanges to gain access to the 
system and remove the spent clay/anthrazite 
from the adsorber vessel. 
. 
. 
This procedure for using organoclay/anthra- 
zite in connection with activated carbon is part 
of the contractor's standard design manual for 
use when hydrocarbons are present as part of 
the constituent contaminants in the process 
stream. Further, the use of organoclay/anthra- 
zite in connection with activated carbon allows 
the contractor to comply with NPDES per- 
mit discharge limits and only change out the 
clay/anthrazite media instead of all the carbon 
beds. 
A plating shop was out of regulatory compli- 
ance with zinc by about 1 ppm. The tumble 
water containing the zinc also contained vari- 
ous oils. A drum of organoclay removes the 
oil, a drum of natural clinoptilolite removes 
the zinc, the customer has been in compli- 
ance over 6 months with no changeout of the 
media. 
A refinery in Canada has a flow rate of 270 
gpm and a temperature of 187°F for its boiler 
feed water. Organoclay is removing 2 ppm of 
oil in spite of fouling by iron. 
COMMON DESIGNS 
The organoclay filter media are designed to use in 
downflow filter contactor vessels, very much the 
same as other filter media. Therefore quite often 
existing filter vessels may be used or changed out. 
Flow rates and differential pressures are similar; i.e. 
3~1 gpm per square foot (~ 0.1 m 2) of filter bed sur- 
face area to establish the design flow and 3-6 feet 
(1-2 m) of bed depth to design detention time (7-10 
min). While no two water treatment systems are 
identical, many similarities exist. 
I I 
u 
® 
EC-100 GAC 
t...J 
FIGURE 4. Typical downflow filter system (upflow is also possible). 
ORGANICALLY MODIFIED CLAY REMOVES OIL FROM WATER 627 
Influent 
Steel Product 
Recovery Tank 
[ 0 ] Feed Reserve 
Float Control 
I © 
Duplex Pump 
Stand. Panel 
n n 
I 
Bag 
Filter Absorption 
( ~ O r ~ n T i t e Duplex 
EFF GAC 8x30 Du flex 
/ 
oc 0 
i 
Absorption 
FIGURE 5. Oil/water separator, followed by organoclay/anthrazite and GAC for water heavily contaminated with free oil and grease, 
plus volatile organics. A bottle with a dripping device, filled with sulfuric acid, can be installed at the oil/water separator if the pH needs 
to be reduced to breakthe emulsion. 
CONCLUSIONS AND RECOMMENDATIONS 
Numerous case histories have shown that the use of 
organoclay/anthrazite media as a prepolisher of acti- 
vated carbon, ion-exchange resins, membranes and 
other media can significantly reduce the operating 
costs and inconvenience to the end user of water 
cleanup systems. Postpolishing of water behind 
DAF units and oil/water separators easily brings the 
waste water into compliance with the most restric- 
tive environmental standards for discharged water, 
be that boiler steam condensate, ground water or 
other process water. Disposal options of spent media 
are cement kilns (spent organoclay/anthrazite media 
has as much as 18,000 BTU), landfills, bioremedia- 
tion through land farming, cement encapsulation or 
incineration. Regeneration is possible if large vol- 
umes of media are in use. 
The experience over the past few years has shown 
that even in cases where water is contaminated with 
a large number of organic compounds, the life of 
activated carbon can be extended by placing a vessel 
of organoclay/anthrazite in front of it, regardless of 
whether or not oil is present. The reason is that 
organoclays exhibit selectivity for certain chlorinated 
hydrocarbons, such as PCP. This ability allows car- 
bon to remove VOCs at higher efficiency. The pres- 
ence of NOMs can also degrade the loading capacity 
of activated carbon. 8 They consist of polynuclear 
aromatic compounds, which are efficiently removed 
by organoclays, as recently shown in a soil stabiliza- 
tion project (Lawson, EarthTech, Inc., written com- 
munication). Organoclays also have some affinity for 
ethylene glycol. An effective method for cleanup of 
water would be a combination of organoclay, anion- 
exchange resins and granular activated carbon, 
where organoclay removes NOMs, FOGs, and other 
sparingly soluble organics, the anion-exchange resin 
removes lighter chlorinated hydrocarbons by anion 
exchange, and carbon removes the VOCs. A side 
benefit is that the organoclay will remove low 
amounts (less than 3 ppm) of heavy metals. 
REFERENCES 
1. Braden, M. L. Demulsification of oily waste waters. WPCF 
64th Annual Conf. & Exposition, Toronto. #AC91-061-005. 
WPCF, 601 Wythe St, Alexandria, VA 22314-1994 (1991). 
2. Alther, G. R., Evans, J. C. and Pancoski, S. E. Organically 
modified clays for stabilization of organic hazardous waste. 
HMCRI's 9th National Conference, Superfund 88, HMCRI, 
9300 Columbia Blvd., Silver Spring, MD 20910, pp. 44ff445 
(1988). 
3. Mortland, M. M., Shaobai, S. and Boyd, S. A. Clay-organic 
complexes as adsorbents for phenol and chlorophenols. Clay 
and Clay Min., 34:581-585 (1986). 
4. Lagaly, G. Clay-organic reactions, interaction. Phil Trans. R. 
Soc. London, A-311:315-332 (1984). 
5. Smith, J. A., Jaffe, P. R. and Chiou, C. T. Effect of yen qua- 
ternary ammonium cations on tetrachloromethane sorption 
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to clay from water. Environ. Sci. Technol., 24:1167-1172 
(1990). 
Symons. J. M., Fu, P. L. K. and Kim, P. H. S. The use of 
anion exchange resins for the removal of natural organic 
matter from municipal water. Int. Water Conf. Proc., 
Pittsburgh, PA, October, pp. 92-120 (1992). 
7. Hermosin, M. C. and Connejo, J. Binding mechanisms of 2, 
4-dichlorophenoxy acetic acid by organo-clays. J. Environ. 
Qual., 22:325-331 (1993). 
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O p e n for d i scuss ion un t i l 19 D e c e m b e r 1996