Note: Descriptions are shown in the official language in which they were submitted.
1084181
!
BAC~GROUND OF Tl~ INV~TION
Fiel~ of the Invention
This invention relates to a unit for r~moval of impurities
from liquids and to a method for doing so.
Description of the Prior Art
~ moval of impurities from liquids such as aqueous solu-
tions, particularly, heavy metals present in small quantities in
waste water ~ffluent, is an acute probl~n due to the toxicity of
the heavy metals and the increasingly stringent water quality reg-
ulations regulating discharge of such materials into water bodies.
In many areas, water containing small quantities of heavy metals
~such as chromium, lead, mercury, cadmiuM, berylli~, etc. cannot De
discharged into municipal sewage syste~ls without rer.loval of the
heavy metals to an extremely low level.
For other purposes, filtering of aqueous solutions is not
adequate with conventional filteriny devices because of the nature
of the material to be filtered. For example, ferric hydroxide is a
gelatinous solid which is very difficult to filter. Fruit juic~s
containing impurities rendering the solution cloudy axe also difficult
to filter and clarify.
Liquids such as used motor oils, tallow, etc. are difficult~
to purify by conventional means.
The removal and recovery of hexavalent chromium from aqueous
metal treating baths by con~act of the hexavalent chromi~n with a
lead compound to form a water-insoluble lead chromate is disclosed
in,United States Patent ~o. 3,493,328. U. S. Patent ~lo. 3,791,520
also discloses a system for removing chromium anions present in
small quantities from waste waters by contacting the waste water ^~
stream with a particulate carrier having a water insoluble lead
compound adsorbed thereon, the lead compoun~ reacting with the chrom-
ium in the waste water stream to form a water-insoluble lead chromate.
The syst~m for chromi~,l removal disclosed in U. S. Patent ~o. 3,791~520
r ~B4~8~
pro~ ~les an effective r.lethod of chromium removal; however, the.flow
rate through the system must be closely controlled to prevent "chann~l-
ing" which results in inadequate removal of the chromium anions
from the incorning waste wat~r stream. In an effort to overcome the
problems encountered with the unit described in U. S. Patent No.
3,791,520, the unit disclosed and claimed herein was designed.
The use of chitin and chitosan to re~.love metal ions from
aqueous solutions is ~inown from U. S. ~'atent Nos. 3,533,940 and
3,635,81~.
SU~L~RY O~ '~HE I~VR~TIOM
It is a primary object of this invention to provide a
unit for removal of i~purities from liquids, the impuritites gen-
erally present in small quantities, by contactin~ the liquid con-
taining the impurities with a loose, particulate treating material
which acts to r~nove the impurity from the liquid stre~ by reaction,
by ion exchange or by adsorption, the treating material held in a
vessel haviny a wall with multiple small op~nings therein, each
filled with an inert, compact, finely-divided filter material re-
tained therein.
It is a further obj~ct of this invention to provide a
unit for removal of metal ions pres~nt in small quantities in waste
water streams by feeding the water containiny the metal ions into a
vessel have multiple small-sized openings in a wall thereof filled
with an inert, particulate, finely-divided filter material retained
in the openings of the vessel by a fine mesh material covering the
outer surface of the wall and the openings, the vessel filled with
a particulate treating material which rer.loves the m~tal ions con~
tained in the aqueous stream, the metal ions retained within the
vessél while the water with the ions removed passes throuyh the
particulate filter u~terial for discharge.
It is a primary object of tnis inv~ntion to provide a r
unit for removal of impurities from non-aqueous liquids such as
1084181
hydrocarbon oils, tallow, etc. ~y contacting the non-aqueous liquid
containing the impurities with a loose, particulate treating mater-
ial which acts to remove the iMpurity from the liquid, the treating
material held in a vessel having a wall with multiple small open- ~
ings therein, each filled with an inert, compact, finely-divided ~`
filter material retained therein. I;
It is a further object of this invention to provide a !
unit for removal of impurities ernploying means within the treating
vessel to progressively sweep the tnner surfac~ of the vessel over
the openings therein to prevent blinding of the filter material
retained in the op~nings by solids and to uniformly distribute the ¦~`
treating material within the vessel.
It is a further object of this invention to provide a
unit for removal of heavy metals present in small quantities from
water streams by contact of the water stream containing the heavy
metal with particulate, naturally-occurring polysaccharide polymer
held w~thin a cylindrical vessel having multi~le small openings
therein filled with a compact, inert, inely divided filter mater-
ial.
These and other objects are accomplished by a system
which com~rises (1) a vessel holding a charye of a particulate treat-
ing material which acts to remove impurities from the liquid fed
the~ein, the vessel having multiple small openings in a wall there-
of filled with a compact, inert, finely-divided filter material
retained in the openings by suitable means, and (2) means for re-
peatedly and progressively sweeping the inner surface of the vessel
over the openings therein and just out of contact with the inn~r
vessel wall to prevent blinding of the particulate filter material
retained in the openings, the same means also mixing and distri-
buting the treating material within the vessel.
BRIEF DESCRIPTIO~ OF T~IE D~ GS
. .
Fiy. 1 is a cross-sectional view of a unit for carryiny
10841 81 t
out the invention disclosed;
Fig, 2 is a cross-sectional view along line 2-2 of Fig. A,
l; and
Fig. 3 is an enlarged cross-sectional view of a portion
of the cylindrical vessel wall of Fig. 1 illustrating the location ;
of the finely divided particulate material and the woven mesh mat-
erial which retains the particulate material in the snall openings
of the cylindrical vessel.
DETAILED DESCRIPTION OF THE INVENTION
~queous streams containing heavy rnetal ions such as
chromium, banium, lead, zinc found in waters in the plating in-
du~try can be treated with the unit disclosed to remove the metal
ions to such a low level that there is no problem in discharging
the resultant effluent into water bodies.
The unit may be also used to remove ferric hydroxide,
phosphates, and cyanide fror~l aqueous streams, remove impurities
frora water discharged from leather tanneries, filter fruit juices
or wines, filter waste petroleum oils, etc.
Fig. 1 illustrates one syst~ for reroving impurities
from liquids. An outer cylindrical housing 10 having end walls 16
and 18 is provided with a discharge port 12 for discharge of treated
liquid after it passes into and through the openings in the wall of
an inner cylindrical vessel 14. End walls 16 an~ 18 include shoul-
der portions 17 and 19 of substantiaLly the same diameter as the
inner diameter of shell 20 of the inner cylindrical v~ssel. The
end walls 16 and 18 cap the open ends of vessel 14. o-ring 21 pro-
vides an effective s~al between wall 20 and the shoulder portion 17
of end wall 16. End wall 18 includes a flan~e portion 11 which is
secured to an integral flange portion 13 of housing 10 by suitable
fastening means 15. O-ring 23 provides an effective seal between
portion 13 and housing 10. Cylindrical wall 20 is secured by suit-
able means over the flange portion 19 of end wall 18. End wall 19
-4-
1~84~81
.
has an inlet port 25 therein for introducin~ the liquid to ~e
treated into the interior of vessel 14. The inlet port may be
fitted with a pressure meter 27 and/or flow m~ter if desired. ;~
Cylindrical wall 20 has multiple small openings 22 therein (see
Fig. 3). The size of the op~nings may vary but preferably range
from 1/8 to 1/2 inch in diameter. The outer housing 10, cylindrical
vessel 20 and end walls 16 and 18 are preferably manufactured fror
a synthetic plastic material which can withstand highly acidic ma-
terials without damage thereto. The units ~nay also be manufactured
from stainless steel or other suitable metals if desired, depending
on the water to be treated.
j Imbedded in each of the op~nings 22 is a finely-divided,
¦ particulate, inert, filter material 24, such as diator;laceous earth.
The particle size of the filter material is chosen depending on the
solid~ to be retained. The particle size of the filter material 24
should be sufficiently s~all to prevent passage therethrough of
particulate solids in the waste water. A pxeferred particle size
is on the order of 2 to 5 microns, on the average. Too small a
particle size of filter matexial results in too slow filter rate
while too large a particle size does not effectively remove the
impurities sought to be removed. To xetain the filter material
within the openings 22, a woven fabric 23 or ot~er suitable mater-
ial having a mesh size s~all enough to prevent passage of the par-
ticulate filter material therethrough is placed over the outer
surface of the cylindrical shell 20 and over the openings 22. For
example, a woven nylon or polyester knit cloth adhesively bonded to
the outer surface of the cylindrical shell has been found to work
adequately.
Mounted within the vessel are a series of blades 26 which
extend substantially the length of the vessel. ~ach blade is scured
by suitable struts 2~ to a rotatable shaft 30 axially mounted in
the vessel. The outer periphery of each of the blades is designed
. 1~8418L
to pass over the inner openings as close as possible to the inner
surface of the wall 20 without affecting the filter material 24
contain~d in the opaning 22. llhe clearance between the blades and
the inner suxface of wall 20 is preferably about 1/64-inch. Shaft
30 extends through an opening in wall 18 and is connected to suit-
able power means 32, such as a hydraulic motor by a connector 29
for rotation thereof. 7~ standard shaft packing gland 31 surrounds
shaft 30 to prevent leakage through end wall 18.
~ For removal of hexavalent chromium from wast~ water solu-
tions the interior of vessel 14 may be filled with a water-insoluble
lead compound which reacts with chromium anions in the water being
treated to form water-insoluble lead chromate. The lead compound
used may be lead oxide, lead carbonate, lead hydroxide, or other
water-insoluble lead compound. The particle size of the partic-
ulate filter material 24 retained in the openings of the cylindrical
shell 20 is chosen to prevent passage of the finely divided lead
chromate precipitate which forms as a result of the reaction of the
water-insoluble lead compound in the vessel with the chromium anions
contained in the waste water stream. The smaller the particle size
of filter material used, the lower the rate of filtration. A pres-
sure differential between the interior and exterior of vessel 14 of
3 to 6 psi is maintained for adéquate filtration. It has also been
found that a wall thickness of the cylindrical shell 20 should be
from 1/4" to 1/2" and preferably 3/~" for optimum results. The
depth of the diator.laceous earth 24 filling the openings 22 in the
cylindrical shell is equal to the wall thickness. The vessel is
~illed with the particulate lead compound in loose form or adsorbed
in t~e pores of a particulate carrier such as disclosed in U. S.
Patent No. 3,791,280. Waste water containing small quantities of
chromium anions is fed into the vessel through inlet port 25. On
contact with the lead compound in the cylindrical vessel, a finely-
divided water-insoluble lead chromate precipitate is formed. ~he
water passes through the diatomaceous earth filter mat~rial 24,
--6--
1~84181
(FW50 with a particle siæe of about 1/64-inch), the diatomaceous ;~
earth preventing passage of the lead chromate precipitate thGretllrouyh.
The blades 26 within the vessel are rotated at a speed sufficient
to prevent blinding of the diatomaceous earth filter material 24 by
the finely-divided lead chror3ate pr~cipitate. The blades also
continuously mix the lead compound within the vessel to prevent
channelincJ. The water with the chromiurn r~loved is discharged from
the housing 10 through port 12. If desired, monitoring means, such
as a conductivity meter, may be used to continuously sample the
discharge water to determine the level of chromium anions in the
water being discharged. ~len the bed of lead within the vessel is ~-
substantially spent water-soluble chromium will pass through the
filter material causing a change in the conductivity of the water
being discharged. The monitor, if desired, can be connected to
suitable control means to automatically discontinue feeding water
into the unit or to notify an operator to take appropriate action.
Two or more units can be run in tandem so that when one unit is
sp2nt the waste water to be treated can be fed into the adjacent
unit. The lead chromate precipitate contained within the vessel
can be recovered and sold as a pigment to the paint industry, or
otherwise used.
,
The system disclosed is also useful for reMoval of other
heavy metals, such as nickel, cadmium, mercury and lead present in
small quantities in water streams, using a particulate treating
material containing a naturally-occurring polysaccharide polymer
such as chitin or chitosan as disclosed in U. S. Patent No. 3,533,940
and 3,635,818. Chitin is the main structural component of lobster,
shrimp and crab shells as well as the exterior skeletons of other
crustaceans, insects and spiders. Chitin is composed of chains of
glucose units in which one hydroxyl in every ylucose fragment is
replaced by acetamido group. "Chitosan", a deacylated form of chitin
produced by heating chitin in aqueous acid, has similar properties
` 1~84~81
to chitin. Both chitin and "Chitosan" act as ion exchange mater- ~
ials for the removal of heavy metals such as chromium, lead, mercury, ~`
zinc and cadmium contained in water soluble form in water streams.
The cylindrical vessel 14 is filled with particulate shrimp, lobster
or crab shells or other source of chitin, the chitin or chitosan
acting as an ion exchange material to remove the solubilized heavy
metals in the water stream fed into the vessel. The p~ of the enter-
ing strear~ to be treated is preferably adjusted to the pl~ of less
than about 7, such as pH 6.5. The cylindrical vessel 14 is filled
with the paxticulate chitin polymer. The particle size of the chitin
or chitosan should range between 6 and 60 mesh (U.S. Sieve Series).
As mentioned earlier the small openings in the vessel wall are filled
with a compact, finely-divided, particulate filter material such as
idatomaceous earth. Blades within the vessel are used to uniformly
mix the particulate treating material contained therein to prevent
channeling and to assure uniform action of the heavy metals contained
in the water stream with the treating material. As mentioned previously,
the ~ater discharged from the unit can be continuously monitored to
determine the effective removal of tne heavy metals contained there-
in. When the ion exchange properties of the chitin or chitosan
have been substantially spent, the incoming water to be treated can
be transferred to a second unit. The heavy metals sequestered by
the treating material in the cylindrical vessel can be recovered by
pyrolysis of the material. Pyrolysis is a known technique involving
the heating of the bed of treating material in a closed vessel in
the absence of oxygent sufficient to decompose the treating material -~
and recover the metal.
~ One of the problems associated with the use of shrimp or
crab shells is that they begin to smell very quickly after the m~at
is removed from the shells due to decay. This makes them almost
impossible to use because of the odor associated therewith. It has
been found tllat soaking the shells in a solution of 0.5 to ~ per
1~84181
.~` ` ' . '
cent by weight formaldehyde prevents their decay. After soaking in
formaldehyde the shells can be dried and used without any odor ;,'
associated therewith. '~
The addition of formaldehyde or other aldehyde to the ,~
treating material also has the advantage of destroying free and/or
chemically combined cyanide present in the aqueous solution to be ;' '
treated, as described in U. S. Patent No. 3,505,217.
If the aqueous stream to be treated contains gross amounts ,~
of heavy metals it is preferable to subject it to pretreatment to
reduce the level of the heavy m~tals. For example, acid solutions
such as pickle liquor solutions may be pretreated by adjusting the
pH of the solution with caustic or other suitable base and preferably
to around p~l 6.5, and then adding sodiurn sulfide to precipitate out
the heavy metal.
The unit may also be used in conjunction with chitin or ~,
chitosan to remove cyanide present in aqueous streams. For exar.lple, ,~
n a solution containing caustic and nic~el cyanide, an aldehyde
such as formaldehyde or acetaldehyde is added which reacts with and
, breaks down the cyanide. The p~ of the solution is then preferably
,adjusted to around pH 6.5 and sodium sulfide added to precipitate
out the heavy metal w~lich is retained within the filter unit by the
filter material 24.
The unit may also be used in conjunction with conventional
filter aids ~diatomaceous earth) as the treating material to filter
and clarify fruit juices such as apple juice and wines. A coarser
grade of diatornaceous earth is used for the treating material than
for the filter material 24. For cleaning cran~case oil the unit
may be filled with an acid clay as the treating material.
:. : . , . . , ~, ,
