Note: Descriptions are shown in the official language in which they were submitted.
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INORGANIC ION EXCHANGER
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FIELD OF THE INVENTION
The invention relates to an inorganic ion exchanger
excellent in strength in water and suitable for use in the
chemical separation at a high temperature o~ either injurious
or beneficial materials contained in water~
BACKGROUND OF THE INVENTION
Techniques have recently been developed for e~fi
ciently carrying out the removal of injurious materials
such as arsenic, chromium and the like from water containing
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such materials or the concentration and recovery of bene-
ficial materials such as uranium and the like from water
containing such materials. from the view-point of environ-
mental purification or of effective exploitation of re-
sources. Such injurious and beneficial materials exist in
water generally as ions and, therefore, it is advantageous
that they are separated from water by treatment with an
ion exchanger~ Particularly, inorganic ion exchangers are,
as compared with organic ion exchangers, excellent in
stability at a high temperature and under a strong radiation,
and have, in most cases, selective ion exchange property
for specific ionsO Thus, inorganic ion are suitable for
the treatment at a high temperature or the treatment of
radioactive substances~
In general, it is necessary to form inorganic ion
exchangers into a specifically shaped product of a proper
size, particularly in the case where the inorganic ion
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exchangers are used by being packed into a colu~n, in
order to lower the resistance to the passage of li~uids.
In addition, such a shaped product is required to have
strength in water, acid resistanc~ and alkali resistance
sufficient to withstand an operation such as a back wash,
regeneration or the like. In order to form inorganic ion
exchangers into a shaped product, known inorganic binders, -
~such as silica sol, water-glass and the like, may be used.
However, the shaped products obtained by the use of such
inorganic binders are inferior in alkali resistance and
have lower ion exchange capacity than that of the ion
exchangers prior to being formed into shaped products.
On the othex hand, for the forming of inorganic ion
exchangers into a shaped product, organic binders such as
natural and synthetic polymers may be used. However, the
use of an organic binder produces shaped products inferior
in heat resistance, acid resistance and alkali resistance.
Thus, such shaped products have drawbacks in that they
weld together or disintegrate during the treatment at a
high temperature or during the regeneration treatment with
a strong acid or a strong alkali.
It is the primary object of the present invention
to provide an inorganic ion exchanger which has a high ion
exchange capacityl is excellent in heat resistance, strength
in water, acid resistance and alkali resistance and is
useful for the treatment of water containing, as ions,
injurious materials or beneficial materials.
DESCRIPTION OF THE INVENTION
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The present invention provides an inorganic ion
exchanger prepared by the process comprising mixing and
kneading at least one titanic acid, selected ~rom anatase
type titanic acid, and amorphous titanic acid with water
5 and at least one inorganic acid, selected from sulfuric
acid, hydrochloric acid and phosphoric acid, and then
extrusion molding the blend, and thereafter, heat treating
the extruded product at a temperature of 50 to 500C.
The titanic acids employed in the present invention
are represented by the formula TiO2 nH2O, in which n is
0.5 to 2.0, and include anatase type titanic acid and
amorphous titanic acid. ~-~
Titanic acids include, in general, those of rutile
type, anatase type and amorphous crystal structures.
However, the use of rutile type titanic acid produces a
disadvantageous inorganic ion exchanger having low strength
in water and poor ion exchange property. On the other
hand, it has been found that the use of anatase type or
amorphous titanic acid produces an inorganic ion exchanger
having high strength in water and good ion exchange property.
Particularly, where anatase type titanic acid is employed,
there can be obtained an inorganic ion exchanger extremely
excellent in acid resistance.
The titanic acids usable for the present invention
may be obtained by heating an aqueous solution of titanium
sulfate or of titanium tetrachloride and then hydrolyzing
said solution, or by adding a base to the aqueous solution
to neutralize it, and then, washing it with wate~, filtering
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and drying the resultant solidO Alterna ively, the titanic
acids may be obtained by hydrolyzing an alkoxide, such as
tetrabutoxide, tetra-isopropoxide or the like, of titanium
in water, and then, washing with water, filtering and
drying the resultant solid.
The inorganic acids usable for the present invention
include sulfuric acid, hydrochloric acid and phosphoric - ~
acid. ~he use of these inorganic acids produces an inorganic
ion exchanger which is excellent in acid resistance and
alkali resistance, but which does not degrade the ion
exchange capacity when it is extruded. The effects of the
addition of the inorganic acid are remarkable where sulfuric
acid, hydrochloric acid or phosphoric acid is employed;
whereby when another inorganic acid, for example, silicic
acid, is employed, the alkali resistance and the ion
exchange capacity of the resultant inorganic ion exchanger
becomes very low. The inorganic acids may preferably be
added in an amount ranging from 0.1 to 7.2 moles per 8
moles of titanic acid. More preferably, 0.3 to 3.0 moles
of sulfuric acid (as H2SO4), 1.2 to 2.4 moles of hydrochloric
acid (as HC ) or 1.2 to 3.6 moles of phosphoric acid (as
H3PO4) may be added per 8 moles of titanic acid. If the
inorganic acid is added in an amount of less than 0.1 mole
per 8 moles of titanic acid, the resultant inorganic ion
exchanger has disadvantageously low strength in water.
; While if the inorganic acid is added in an amount
of more than 7.2 moles per 8 moles of titanic acid, it
becomes difficult to carry out the extrusion molding due
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to the remarkable increase of the viscosity and the sepa-
ration of the solid and the liquid in the blend during the
kneading and; in addition, there is inconvenience in that
excessive inorganic acid ble~ds out onto the surface of
the inorganic ion exchanger, thus causing the sur~ace to
become tacky due to the absorption of moisture, which
occurs even after the heat treatment at a high temperature,
and particularly in the case where sulfuric acid or phos-
phoric acid is employed.
The amount of water to be added may preferably be 1
to 50 moles per 8 moles of titanlc acid. More preferably,
the amount may be varied more or less depending upon the
type of the extrude used, the aperture of the die or
screen used, the extrusion speed, the amount of the added
inorganic acid or the like. For example, where the inorganic
acid is added in an amount of not more than 2 moles per 8
moles o~ tltanic acid, it is pre~erred to add water in an
amount of 20 to 50 moles per 8 moles of titanic acid.
The kneading o~ the blend of the titanic acid, the
inorganic acid and the water may be carried out in a batch
type or continuous type kneader. The blend may preferably
be molded by a pelleti~er of a type such that the blend is
molded under pressure, such as a screw type extxusion
pelletizer, roll type extrusion pelletizer or blade type
extrusion pelletizer. By such extrusion molding, an
lnoxganic ion exchanger, having a strength much higher
than that of an inorganic ion exchanger obtained by merely
drying the blend or by dryLng and heat treating the blend,
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can be obtained. The particle diameters of the pellets
obtained by the extrusion molding may be in a range of
from 0.1 to S.0 mm by appropriately selecting the diameter
of the bores of the die or screen of the pelletizer.
Then, the molded pellets are heat trea~ed to obtain
the inorganic ion exchanger of the invention. It is
suitable to carry out the heat treatment at a temperature
of from 50 to 500C. Where the heat treatment temperature
is higher than 500C, the resultant inorganic ion exchanger
may be very low in ion exchange capacity. Where the
temperature is lower than 50C, the resultant inorganic
ion exchanger may have a low strength. In order to obtain
an inorganic ion exchanger excellent in both the strength
in water and the ion exchange capacity, lt is particularly
preferable to carry out the heat treatment at a temperature
of from 100 to 400C.
In the case where the inorganic ion exchanger of
the present invention is to be used by being packed into a
column through which polluted water to be treated is
passed, the inorganic ion exchanger of the pelletized form
may be used as such, or after grinding and dressing it or
forming it into a globu}ar form.
The inorganic ion exchanger of the present invention
is excellent ln heat resistance, acid resistance, alkali
resistance, has high strength in water, good ion exchange
property, and, in addition, has very high ion exchange
- speed. Further, in the presenk invention, it is possible
! ~ to greatly change the ion exchange capacity of the resultant
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inorganic ion exchanger by selecting the inorganic acid to
be used. Thus, the inorganic ion exchanger obtained by
the use of sul~uric acid or hydrochloric acid is particularly
excellent in selective ion exchange proper~y for alkaline
earth metal cations and polyvalent anions. Examples of
the alkaline earth metal cations include radium, barium,
strontium and calcium ions and examples of the polyvalent -
anions include arsenate, arsenite, chromate, phosphate,
uranyl, molybdate, tungstate and vanadate ions. The
inorganic ion exchanger is particularly useful for the
removal or the concentration and recovery of these polyvalent
anions in an aqueous system containing a large amount of
chloride ion, bromide ion or the like. On the other hand,
the inorganic ion exchanger obtained by the use of phosphoric
lS acid is excellent in selective ion exchange property for
metal cations, such as cesium, rubidium, silver, potassium
and barium ions. Thus, the inorganic ion exchanger is
useful for the removal or the concentration and recovery
of these cations and can be utilized for the separation of
alkali metal cations or of alkaline earth metal cations.
The inorganic ion exchanger according to ~he present
invention has high strength in water and is stable at pH
values in a wide range. Thus, the inorganic ion exchanger
can be subjected to the back wash and the regeneration,
which is usual in conventional ion exchange resins; and as
a regenerant, there can be used hydrochloric acid, sulfuric
acid, sodiu~ hydroxide, potassium hydroxide, sodium car-
bonate, ammonium carbonate, aqueous ammonia and the like. ~
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Upon the use of the inorganic ion exchanger of the
present invention for the removal of injurious materials
or the concentration and recovery of beneficial materials,
a so-called slurry technique, in which the inorganic ion
exchanger is suspended in water containing the injurious
or beneficial materials and then filtered, can ~e utilized.
A packed column technique, in which water containing the
injurious or beneficial materials is passed through a
column packed with the inorganic ion exchanger, can also
be utilized.
INDUSTRIAL APPLICABILITY
The inorganic ion exchanger can be applied, by the
utilization of the above-mentioned features, to the removal
of arsenic contained in underground water, geothermal hot
water, waste water from ore treatment and the like, the
removal of phosphorus from plant waste water, the removal
or recovery of radium or uranium from waste water from
uranium smelting, and the recovery of chromium from plating
waste water.
The invention will further be illustrated by the
following non limitative examples.
Example 1
Anatase type titanic acid (Tio2 ~2)~ water and
sulfuric acid, hydrochloric acid or phosphoric acid were
~lended at the proportions shown in Tahle 1 below. The
blend was then well kneaded in a kneader and formed into
pellets, having a length of 3 to 7 mm and a diameter o
0.5 mm, on a screw type extrusion pelletizer pro~ided with
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a screen having bores of a diameter of 0.5 mm. The molded
pellets were heat treated in hot air at 110C for 16 hours
and then in an electric oven at 300C for 3 hours to
obtain a pelletized inorganic ion exchanger.
To evaluate the strength of the obtained inorganic
ion exchanger, 300 cc of hot water of 90C was charged
into a 300 cc beaker and 10 g of the inorganic ion changer
was immersed into the hot water and agitated for 5 hours
in a jar tester at a rotational speed of 150 r.p.m. Then,
the inorganic ion exchanger was filtered off, heat treated
in an electric oven at 300C for 3 hours and then sieved
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with a 48 mesh Tyler standard sieve. The percentage (by
weight) of the powder formed by the hot water treatment
and passed through the sieve was determined as a powdering
percentage. The determined powdering percentage is shown
in Table 1 as a measure of the strength.
Further, to evaluate the alkali resistance and the
acid resistance of the inorganic ion exchanger, 1 g of the
inorganic ion exchanger was immersed into 50 cc of a 25%
aqueous sodium hydroxide solution or concentrated sulfuric
acid and the liquid was left to stand for 24 hours while
periodically being shaked. Then, the change of the shape
of the pellets was observed. The results are also shown
in Table 1.
For comparison, anatase type titanic acid as mentioned
above was blended with silica sol (moisture content of
80%) or an aqueous sodium silicate solution (moisture
content of 68%) at the proportions as shown in Table 1 and
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the blend was treated in the manner as mentioned above to
obtain a comparative inorganic ion exchanger. The obtained
comparative inorganic ion exchanger was then subjected to
the above-mentioned evaluation tests. The results are
also shown in Table 1.
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Example 2
The procedure as in Example l was repeated using
amorphous titanic acid, sulfuric acid and water at the
proportions shown in Table 2 below to obtain a pelletized
inorganic ion exchanger. The strength of the obtained
inorganic ion exchanger was evaluated in the manner as in
Example l. The results are shown in Table 2.
To evaluate the ion exchange property of the inorganic
ion exchanger, lOO cc of an aqueous arsenic acid solution
containing lOO ppm of arsenic was charged into a sample
bottle and l.O g of the inorganic ion exchanger was added
to the solution and immersed into the solution at 40C for
3 hours while stirring. Then, the amount of the arsenic
retained in the solution was determined. The results are
also shown in Table 2.
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Comparative Example 1
Amorphous titanic acid powder of particle diameters
of 30 to 100 m, which was obtained from the same amorphous
titanic acid as used in Example 2, was sub~ected to the
test for the ion exchange property as mentioned in Example 2.
The determined amount of the retained arsenic w~s 40 ppm.
Thus, it was proved that the ion exchange property of the
amorphous titanic acid powder was fairly inferior to that
of the inorganic ion exchanger of the present invention as
in Example 2.
Amorphous titanic acid powder, the same as used in
the above, was charged into a mold and press molded under
a pressure of 1000 kg/cm2 into a disc. The disc was then
ground and sieved to produce a granular material of particle
sizes of 16 to 48 mesh. The granular material was then
subjected to the tests for strength in hot water as in
Example 1 and for the ion exchange property as in Example 2.
The powdering percentage was 74% and the amount of the
retained arsenic was 68 ppm~ Thus, it was proved that the
20 strength was fairly inferior to that of the inorganic ion
exchanger of the present invention and that the ion exchange
property was further inferior to that of the amorphous
titanic acid powder as mentioned above.
Example 3
A pelletized inorganic ion exchanger was prepared
in the manner as in Example 1, except that 800 g of anatase
type tltanic acid, 67 cc of concentrated sulfuric acid and
400 cc of water were used and the~heat treatment was
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carried out under the conditions shown in Table 3 below.
The powdering percentage was evaluated, as in E~ample 1,
and the amount of the retained arsenic was evaluated, as
in Example 2, and the results axe shown in Table 3.
Table 3
Powdering Amount of
Heat Treatment Percentage Retained
Condition (%) Arcenic(p~ R~rks
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110C, 16 hrs. 5.2 0.49
200C, 3 hrs 1.0 0.54
300C, 3 hrs. 0.5 0.70-
500C, 3 hrs. 5.6 2.53
Disintegrated
700C, 3 hrs. 7.1 89.0 uFon soaking
in water
Comparative Example 2
726 g (8 moles) of rutile type titanic acid (TiO2 -
0.6 H2O), 67 cc (1.26 moles) of concen-trated sulfuric acid
and 400 cc ~22.2 moles) of water were blended. The blend
was then well kneaded in a kneader and formed into pellets,
having a length of 3 to 5 mm and a diameter of O.S mm, on
a screw type extrusion pelletizer provided with a screen
having bores of a diameter of O.S mm. The molded pellets
25 were heat treated in hot air at 110C for 16 hours and
then in an electric oven at 300C for 3 hours.
The powdering perc ntage of the granular ma-terial
evaluated, as in Example 1, was 100~ and the amount of the
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retained arsenic evaluated, as in Example 2, was 98 ppm.
Thus, it was proved that the use of the rutile type titanic
acid could not produce an inorganic ion exchanger satis-
factory in strength in hot water and in the ion exchange
property.
- Example 4
7.83 kg (80 moles) of anatase type titanic acid
(TiO2 H2O), 340 cc (6.4 moles) of concentrated sulfuric
acid and 5.18 ~ (288 moles) of water were well kneaded in
a kneader and formed into pellets, having a length of 2 to
7 mm and a diameter of 1.0 mm, on a screw t~pe extrusion
pelletizer provided with a screen having bores of a diameter
of 1.0 mm. The molded pellets were heat treated at llO~C
for 16 hours and then at 300C for 3 hours to obtain a
pelletized inorganic ion exchanger.
The inorganic ion exchanger was packed into a
column of an inner diameter of 50 mm and a length of 1500 mm
to a height of 1000 mm. Then, an aqueous solution of
K~HPO4 containing 50 ppm of PO4 was passed through the
column at a S.V. (space velocity) of 10. The concentration
of PO4 in the effluent solution was maintained below
O . 3 ppm over the course of 50 hours.
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