Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
735
The invention relates to a process for the production of an
anion exchanger which is particularly suitable for the treatment of
waste water.
The treatment of municipal and industrial waste water is be-
5 coming an increasing problem, especially in industrialized countries.It is therefore technologically important to develop processes which
give a high efficiency at relative low cost for the treatment of waste
water which besides protein and heavy metals contains refractory
components. Proteins can be treated on biological units, but often the
10 materials are so valuable that it would be natural to consider a reco-
very process.
Proteins, polypeptides and amino acids can be removed by
chemical precipitation. As precipitants are used lignin sulphuric acid
and dodecylbenzene sulphonic acid, and others.
However, only very high molecular weight proteins are pre-
cipitated and compounds such as proteins with medium and lower
molecular weight, polypeptides and amino acids are not removed by
this process.
It would therefore be desirable to have an ion exchanger
20 available which can remove such compounds and can therefore be used
for the treatment of waste water, which has been subjected to the
precipitation treatment. Examples of waste water for which such a
combined treatment may be advantageous is such from fish filletting
factories, dairies, slaughterhouses and other food processing plants.
25 This removal is furthermore of interest for the recirculation of water
in fish farms.
A number of cellulose ion exchangers are already on the
market. Examples are cellulose sulphate esters produced by reacting
cellulose with SO3, and also cellulose phosphate esters. These are
30 capable of solving the above mentioned problem, but all these ion
exchangers are prohibitively expensive.
It is the object of the invention to provide a process for
the production of ion exchangers which have high efficiency in -the
treatment of waste water and can be produced at the lowest possible
35 cost. Particularly, these ion exchangers should be capable of removing
anionic organic compounds as well as pro-teins and other nitrogen
compounds from the waste water. Moreover, the ion exchanger should
be capable of regeneration in order to reduce the problem of
disposing of consumed ion exchanger material to a minimum.
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With ~his object in view, the invention relates -to a process
for the production of an anion exchanger, particularly -for the treat-
ment oF waste wa-ter, which is characterized in that cellulose or a cel-
lulose derivative is treated with polyethylene imine in an aqueous re-
action medium at a pH-value of 2-6, and the ion exchanger is recover-
ed from the reaction mixture.
The recovery of the ion exchan0er from the reaction mix-
ture can take place by decanting, filtering and other separating me-
thods, and after having been separated from the reaction medium the
ion exchanger can be washed and/or dried. It is, however, preferable
to bring ~he ion exchanger on the market without first washing and
drying it and to perform the washing with water only immediately be-
fore it is taken into use.
The reaction of the cellulose or the cellulose derivative with
the polyethylene imine can take place at ambient temperature, however,
it is preferable, in order to reduce the reaction time and to increase
the degree of reaction, to work at higher temperatures, e.g. in the
range 40-90 C, preferably in the range 60-70 C.
The pH-value of the reaction mixture can advantageously be
adjusted in the range from 4 to 5, which can be effected by means of
an acid, preferably hydrochloric acid. The reaction time depends on
the other reaction conditions, particularly whether stirring takes
place or not. The reaction time is relatively long, usually in the
range from two hours to four days.
The speed of reaction also depends on the concentration of
the polyethylene imine solution. This concentration should therefore
be at least 1% by weight, and preferably at least 2% by weight.
Solutions of 5-40% by weight are very suitable.
The polyethylene imine solution can be used successively
` 30 for several charges, seeing that upon removal from the first and also
subsequent charges it still contains a sufficient amoun-t o-f polyethyle-
ne imine for effecting additional reac-tions. Usually about 5-10% o-f the
polyethylene imine is consumed in the production of the ion exchanger.
The reaction time is pre-ferably in the range from 1-4 days in order
to obtain a very good activation of the material and to bind enough
polyethylene to the cellulose or the cellulose derivatives.
As starting material it is preferred not to use pure cellulose,
but a cellulose derivative. Some particular cellulose derivatives give
an increased activity. One of the cellulose derivatives that may be
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used with advantage is sulphonated lignocellulose, which is e.g. known as an
intermediary product in the manufacturing of cellulose. Another preferred start-
ing material is a mixture of cellu]ose derivatives, which is obtained from bark
when this is treated in separate steps with alkali hydroxide solution and with
sulphuric acid.
The compounds contained in this starting material are not de~ined.
However, it is evident that they contain sulphurous strongly acid groups, such
as acidic sulphate ester groups or sulphonic acid groups as well as carboxyl
groups and hydroxyl groups.
This starting material can advantageously be produced by first treat-
ing comminuted bark preferably having an average particle size from .5-5 mm, pre-
ferably from 1 to 3 mm, with an alkali hydroxide solution of at least 5% by
weight, preferably 20-40% by weight, preferably sodium hydroxide solution, then
washing with water, preferably to a pH-value of 9 or below, thereafter treating
the bark with sulphuric acid of 30-75% by weight, preferably 40-70 and more pre-
ferably 50-65%, and finally washing with water preferably up to a pH-value above
4. The time of treatment with the alkali hydroxide solution is .5-20, prefer-
ably 3-10 hours, and the time of treatment with sulphuric acid is .5-8, prefer-
ably 1-6 hours.
Especially for the use in the treatment of waste water, it is advant-
ageous to mix the anion exchanger obtained by the reaction of polyethylene imine
with activated clay, preferably A1203, in the ratio from 2:1 to 1:4~ preferably
1:2. The last mentioned value particularly applies to the use of the mixture
for the purification of municipal waste water. The clay can advantageously be
activated by treatment with nitric acid, but also clays otherwise activated can
be used.
The ion exchanger according to the invention has a surprisingly high
63~735
efficiency in the treatment of waste water, and in particular it has a high
selectivity towards proteins, polypeptides, amino acids, dyestuffs, humic acid,
inorganic anions such as chromate ions or phosphate ions, and other impurities
occurring in household or industrial waste water. E.g. this ion exchange can be
used for the purification of municipal waste water and waste water from textile
dyeing plants, galvanizing plants, slaughterhouses and fish filletting factories
and also from the canning industry and soy bean factories.
The anion exchanger according to the invention can also be used for
the recirculation of fish farm water when it is mixed with a
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~6~735
cellulose cation exchanger and activated clay, such as clinoptilolite in
the ratio 2:2:1 to 1:1:4. Since clinoptilolite is capable of removing
ammonium a complete removal of nitrogen compounds in fish farm
waters is obtained by using this mixture.
The anion exchanger according to the invention can in case
of need easily be regenera-ted, e.g. by elution wi-th sodium hydroxide
or an aqueous solution containing a mixture o-f sodium hydroxide and
sodium chloride preferabiy a solution oF .1-1.5 M NaOH and 0.5-2 M
NaCI is used for the regeneration. After the regenera-tion a reac-
tivation can, if necessary, be effected by treatment with polyethylene
imine .
EXAMPLE .
As a starting material was used a cellulose derivative mix-
ture produced in the following manner.
Pine bark was comminuted by means of a cutting machine to
a particle size of .5-3 mm. The comminuted bark was placed in a ves-
sel and covered with a 15% sodium hydroxide solution for seven hours.
After removal of the sodium hydroxide the bark was washed with wa-
ter until the pH-value was 9 or below. Thereafter the bark was co-
vered in the same vessel or another with 65% sulphuric acid for four
hours. The bark was then washed until the pH-value was 4 or above.
An aqueous polyethylene imine solution of approximately 7%
was adjusted to pH 4.5 with hydrochloric acid. The starting material
produced as described above was covered with this solution, the re-
action mixture was heated for four hours to 70 C and was then left
to stand for three days at ambient temperature. Thereafter the pro-
duct of the process was separated by filtration, and the filtrate could
be used for a further charge after making up for the consumed poly-
ethylene imine solution and readjustment of the pH-value.
Immediately before use the moist ion exchanger produced as
above described was washed several times with water. For determining
the coefficient of selectivity solutions of azodyestuffs, dodecylbenzene
sulphonic acid (DBS), humic acid, and potasium chromate were pro-
duced and passed through a column of the anion exchanger. A glass
column filled wi-th the anion exchanger having a diameter of 2.5 cm
was used, the thickness of the bed was about 30 cm and the flow rate
was 15 m per hour. The outflow frorn the ion exchanger column was
analyzed for every 500 ml. The coefficient of selectivity determined
by this analysis means the quantity of a substance which is taken up
'73~
in preference to sodium chloride when the ionexchanger is treated
with a solution, the dissolved matter of which comprises 50% of the
substance in question and 5~6 sodium chloride. The coefficient of
selectivity determined for the various subs-tances are shown in Table
1.
TAeLE 1.
25 mgll of solution pH of -the solution Selectivity coeFficien-t
Red Azodyestuf-f 6.8-7.2 67
Yellow Azodyestuff 6.8-7.2 35
DBS 6.8-7.2 50
Humic acid 6.0-6.5 100
CrO4 6.5-6.8 19
In another test the anion exchanger produced as described
15 above was mixed with activated clay in a proportion such that the
mixture consisted of 2/3 activated Al2O3 and 1/3 ionexchanger. This
mixture was used for testing the removal of phosphorous from an
aqueous solution. The mixture was -filled in-to a pilo-t plant having a
diameter of 15 cm and a height of 2 m, a 1 m layer of the mixed
20 ionexchanger material being used. The activated Al2O3 is capable of
removing orthophosphate, while the anion exchanger is capable of
removing polyphosphate and organic phosphates. A flow rate of 10
bed volumes per hour was used corresponding to 175 I waste water
per hour. The flow o-f waste water was directed upwards through the
25 column. After the column was saturated, it was regenerated by wash-
ing with 35 I water, elution with 25 1 .5 M NaOH, and washing with
70 I water.
The following types of waste material were treated in the pi
lot plant:
30 I. Waste water effluent from a biological filter, total phos-
phorous content 9.6 mg/l.
I l . Waste water effluent from chemical precipi-tation, total
phosphorous conten-t 0.61 mg/l.
I l l . Overflow from a rain water bassin, total phosphorous
content 1.08 mg/l.
The column and the elution liquid were used four times be-
fore the test here considered was carried out. Samples of the output
were analyzed every second hour. The results are shown in the fol-
Iowing Tables 2 and 3.
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TABLE 2.
Capacity Sludge
InflowBed volurnes m3 * I l/m3 was-te wa-ter.
I ......... 320 5, 5 5 0 . g0
Il......... 2200 38,4 5 0.13
Ill........ 1811 31,6 5 0.16
* 0.1 m3 is deducted corresponding 0.1 m3 washing water.
TABLE 3.
Soluble
Sample soluble poly-
(average) P total P soluble Ortho-P org. P phosphates
Inflow I 9.6 7.3 6.1 0.7 0-5
Outflow 1 0. 95 0. 950. 57 0 . 2 0 . 2
Inflow l l 0.610.37 0.25 0.05 0.05
Outflow ll 0.060.06 0.01 0.03 0.02
Inflow lll 1.080.51 0.38 0.'11 0.04
Outflow lll 0.100.10 0.03 0.03 0.04
Tables 2 and 3 show that the capacity corresponds to about 90%
removal of phosphorus.
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