JPS59213445A - Regeneration of ion exchange filter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Prior Art The ever-increasing content of nitric acid in natural waters has become a serious problem. Nitrate cannot be removed from water by conventional water treatment methods because it is the final or stable end product of the transformation of nitrogen compounds in soil and water under natural or aerobic conditions. Among the many sources of nitrogen compounds, the large-scale pollution caused by the application of nitrogen fertilizers in agriculture is the most important.

Nitric acid causes health problems and fatal diseases in humans and warm-blooded animals. The most well-known effect of nitric acid is 15η/l.
The so-called nitrate-feeding methomoglobinaemia is said to occur in infants up to 3 months of age when food is prepared with water containing a large amount of nitrogen.
This is the appearance of Naemie. However, Czechoslovakia's IJI-J allows up to 50 ■/l of NO3-. Similar standards in other countries also allow concentrations higher than the limits given for infants. In adults, high nitrate concentrations in drinking water can cause cancer of the throat, stomach, and bladder. It also causes abortions in cattle and fatal poisoning of captive-reared calves. Nitric acid in water also has a strongly negative effect on food production (eg malt germination), food preservation and beverage production.

In addition to nitric acid, hardness components are also harmful if their concentration in the treated water exceeds the values specified in the standards for drinking water. Also, they have high hardness, e.g.
It is undesirable for certain food productions where it may result in bitterness in the drink.

One method for removing nitric acid from water is the use of ion exchange resins. Their common advantages are their independence from water temperature, reasonable reaction rates, high efficiency, and the fact that the denitrification bed occurs without the addition of other substances, and they are suitable for use in anaerobic environments. This means that it is not necessary. However, in many cases this process results in undesirable changes in the content of other anionic components in the water. Strongly basic anion exchange resins, mostly in the chloride form, are most frequently used. However, especially early in the cycle, this type of annex
has the disadvantage of high chlorine concentration in the offshore water since it exchanges all the anions present for the chlorine ions.

At this time, the chlorine level in the treated water exceeds the value prescribed by regulations for drinking water. This filtered water is essentially chlorinated water that can cause physiological disorders. On the other hand, sulfuric acid is removed together with nitric acid from the treated water. 'Also some of the hydrogen carbonate is removed and the quality of the water is therefore substantially changed. The advantage of using this chloride form of anion exchange resin is that it is easily regenerated. When the bed is regenerated, the nitric acid is flushed out with only 8 volumes of 10% sodium chloride solution.

The application of strongly basic anion exchange resins in the bicarbonate form also
This is unsuitable because the level of bicarbonate in the filtered water will be high. Bicarbonate replaces all anions present in the first half of the sorbed phase.

Only in the second phase of the sorption phase is a stepwise increase in chlorine level, and in the last phase, as a result of gradual desorption from the ion exchange medium, the chlorine concentration increases to a similar level to the initial concentration. It gets expensive.

However, this means that the standard value of chlorine in offshore water exceeds the limit if the incoming water has a higher chlorine concentration. Sulfuric acid is completely removed, their concentration increases only with increasing nitric acid concentration. Another drawback of strongly basic anion exchange resins in the bicarbonate form is that they are difficult to regenerate. In the regeneration phase, nitric acid is washed out only after application of 23 volumes of 10% Na HCo 3 as measured by the anion exchange resin volume.

The use of regenerated mixed chloride-bicarbonate media of strongly basic anion exchange resins is known.

Their advantage is that chloride and bicarbonate, the two anion exchange resin components, are both present in the offshore peroxide early in the sorption cycle. However, in this case too, sulfuric acid is removed together with nitric acid. Therefore, the filtered water is chloride-bicarbonate modified water. Because desorption of chlorine occurs in the second half of the sorption cycle,
The standard chlorine concentration in the filtered water is, again, when the chlorine concentration in the influent water is much higher (even if it is within drinking water standards).
, the limit is exceeded.

Similarly, in the case of removal of nitric acid on an anion exchange resin in a sulfuric acid cycle, all anions are replaced by sulfate ions early in the treatment cycle.

For drinking water denitrification beds, weakly basic anion exchange resins in the bicarbonate form are sometimes also used. However, this technique has other drawbacks besides excess of bicarbonate ions in the filtered water and desorption of chloride ions and reduction of sulfuric acid in the second half of the treatment cycle. In equivalent water, the denitrification bed area of a weakly basic anion exchange resin is about V4 of that of a strongly basic anion exchange resin. When the treated water is passed through this type of anion exchange resin whose denitrification bed has already been consumed, the residual nitric acid is automatically washed out of the ion exchange resin.
The effluent water is therefore effectively enriched in nitric acid.

Among the currently known methods for the removal of nitric acid from water by means of ion exchange resins, from the point of view of efficiency the method as protected by Czechoslovak Inventor's Certificate No. 200907 is the most suitable method. It seems to be.

By using an ion exchange resin, this method can selectively remove only nitric acid while preserving other anionic components of water.

This method uses three strongly basic anion exchange resins, namely chloride, sulfuric acid and bicarbonate forms, mixed in predetermined proportions. However, the essential drawback of this method is that the resulting medium cannot be regenerated and all three forms of ion exchange resin have to be prepared fresh separately after consumption. For this reason, this method should only be used in small, single-purpose devices designed, for example, for the denitrification of drinking water in homes, as a rule for the preparation of artificial food for infants. I can do it. After consumption the floor will be discarded.

Therefore, although economical and easily regenerated processes for anion exchange resins remove nitric acid, they degrade the physiological properties of the water and, on the other hand, methods for selectively removing nitric acid cannot be used on a large scale. .

SUMMARY OF THE INVENTION The object of the invention is to provide a method for the regeneration of ion exchange filters based on strongly basic anion exchange resins used for the removal of nitric acid from water, which is economical to operate and which reduces the physiological The object of the present invention is to provide a method for removing nitric acid without deteriorating properties.

Another object of the invention is to enable the regeneration of additional filter beds based on strongly acidic cation exchange resins used to soften water. Other objects and advantages of the invention will become apparent from the following description and from the tables showing the results of the application of the regeneration method according to the invention.

The method proposed by the present invention, which allows repeated use of the ion exchange medium and which selectively removes nitric acid and at the same time removes hardness components, is based on a denitrification bed based on strongly basic anion exchange resins. A denitrifying bed and softening filter, wherein the filter or denitrifying bed portion is based on a strongly basic anion exchange resin and the softening portion is based on a strongly acidic cation exchange resin,
In the first stage of regeneration, a regeneration solution containing chloride ions and possibly a Na CL or KCt solution is contacted;
step with a solution containing sulfate ions, possibly thorium or potassium sulfate, and bicarbonate ions, preferably sulfur or potassium bicarbonate. The advantage of this regeneration process is that, under economically suitable conditions, it can be used to selectively remove nitric acid from water while preserving other anion exchange resin components and thus preserving the physiological value of the water. This can be seen in the fact that strongly basic anion exchange resins can be used. In terms of a relatively simple regeneration process,
This method can be applied iteratively and with a wider scale of operation. In cases where denitrification beds and water hardness reduction are carried out simultaneously (e.g. in industrial production of beverages), this method is useful since the solution from the anion exchange regeneration is also used for the regeneration of the cation exchange resin. , which is economically acceptable.

In the first stage of the regeneration cycle, effective desorption of nitric acid, which was inhibited in the previous treatment cycle, is achieved by using a relatively small amount of solution containing chloride ions. Anion exchange is mainly converted to the chloride form in this phase. For regeneration of denitrification beds and softening filters, regenerants from anion exchange resins are also used for regeneration of cation exchange resins and vice versa. In the next stage of regeneration, the strongly basic anion exchange resin is converted from the chloride form to a mixture of various anion exchange resin forms, while the final residues of nitric acid from the processing cycle are desorbed. The cation exchange component of this second solution can also regenerate the cation exchange resin.

EXAMPLE In the following, the operation of the method according to the invention will be explained in more detail with the aid of a table showing the results of the regeneration process for different conditions.

Table 1 shows the composition of the filtrate from a strongly basic anion exchange bed regenerated only for the chloride cycle, Table 2 shows the composition when regenerated according to the invention, and Tables 3-6
Table 7 shows the results when regeneration solutions of different compositions are applied, and Table 7 shows the results when a strongly basic anion exchange resin bed and a strongly acidic cation exchange resin bed were regenerated together. The effects of media reproduced according to the present invention can be seen. Table 1 shows the composition of the filtrate from a strongly basic anion exchange resin bed that was regenerated only for the chloride cycle.

In the first column, the amount of filtered water is shown as the volume of anion exchange resin used in the filter bed.

Table 1 Apparent amount of filtrate water Composition of filtrate nmo4/l
V/VoNO3-1/2804”HCO,-C1-2
0000・25.8 40 0 0 0.3 5.760
0 0 0.3 5.680
0 0 0.4 5.6100
0 0 0.6 5.4120 0
0 1.1 4.9140 0.
01 0 1.8 4.2160 0.
03 0 2.2 3.8180 0.
07 0 2.4 3.6200 0.
20 0.1 2.3 3.4220 0
．． 36 0.3 2.0 3.3240
0.55 0.55 1.8 3.1 Inflow water 1
．． 53 0.94 1.8 0.8 filter bed 2@2
Strongly basic anion exchange resin of the type, column depth 0.
6 m s S = 20V/Vo 0S = 3V/vo-
Distilled water 1 with 1 h of water was regenerated in parallel flow with 8 Vo of a solution with a concentration of 100 NaCt. Washed with 8Vo distilled water.

v Volume of filtrated water vo: Volume of anion exchange resin S:
Specific Load Table 2 shows the composition of the filtrate for an anion exchange resin bed regenerated according to the present invention. The amount of filtrate in the first column is given as a multiple of the volume of anion exchange resin used in the filter bed.

Margin table below 2 Apparent amount of filtrate Composition of filtrate nma17'
l.

20 0 1.3 3.5 1.2
40 0 1.4 3.2 1.4
60 0 2, B 2.3 1.4
80 0 2.8 1.9 1.31
00 0 3.1 1.8 1.11
20 0.01 3.4 1.8 0.8
140 0.05 B, 3 1.8
0.8160 0.12 3.2 1.8
0.8180 0.24 3.3 1.
8 0.8200 0.40 3.0 1
．． 8 0.8220 0.52 2.9
1.8 0.8240 0.66 2.7
1.8 0.8 Inflow water 1.53 0.94 1
．． 8 0.8 filter bed: a second type of strongly basic anion exchange resin, washed with a solution 5Vo containing 1009 NaCt in distilled water at a depth of 0.6 m N I L, then 85.8 m in lt distilled water. 9 I Na2SO4,14,
A mixed solution containing 19ONaHCO5 at 5V was regenerated in parallel flow. S wo 3 v/v, -ho 8 V
Washed with distilled water.

v: Volume of filtrate water vo: Volume of anion exchange resin S
From the values in specific load tables 1 and 2, the following can be seen. That is, significant nitric acid removal is achieved for the two types of filters.

However, for the second filter (Table 2), at the same time,
The content of other anions is relatively uniform and does not exceed drinking water standards. For the first filter, sulfuric acid is removed along with nitric acid, and in the fourth half of the treatment cycle most of the bicarbonate is removed. The filtered water is chlorinated water and has 4 to 7 times more chlorine than the inflow water, and as a whole meets the drinking water standard (2.82nmot/
l) does not match.

In Tables 3-6 below, examples of recovery processes are shown with results obtained in regenerated beds.

Table 3 Apparent amount of convulsive water Composition of filtrate nmal/1
20 0 0.1 1.05 0.5
040 0 0.1 1.0 0.
5060 0 0.15 0.85 0
．． 6580 0 0.20 0.70
0.80100 0 0.25 0.5
5 0.85120 0.01 0.25
0.50 0.90140 0.01 0.3
0 0.45 0.87160 0.06
0.50 0.40 0.60180 0.1
0 0.80 0.40 0.30200
0.25 0.85 0.40 0.10220
0.90 0.30 0.25 0.052
60 1.40 0.10 0.10 02
80 1.600 00300 1
．． 60 0 0 0 Inflow water 1.60 0
0 0 v: Volume of filtered water vo: Volume of anion exchange resin S:
Specific load table 3 shows the second type, depth 0.6 m, S = 45
Results obtained with a strongly basic anion exchange resin of V/Vo-h are shown. This bed is made of 1 ton of distilled water.
5V of a solution containing sodium chloride of 01 and further 85.9 g of sodium sulfate in 1 t of distilled water and 14.1. F
was regenerated in cocurrent with a mixed solution 5Ve containing sodium hydrogen carbonate. It was then washed with 8Vo distilled water.

An influent water was also prepared containing sodium nitrate at a concentration of 100 g/l NO3- in distilled water, ie containing no other anionic moieties. Despite the fact that only nitrates are present in the influent water, the water regenerated according to the invention contains chlorine, sulfuric acid and carbonic acid in such amounts as to meet drinking water standards after passing through the filter bed. It can be seen that this regeneration filter has the ability to displace nitric acid by the main anions present in the water, even in this extreme case, which contains hydrogen and therefore does not normally occur.

Margin table below 4 Apparent amount of filtrate water Composition of filtrate nmroL/
lV/V, NO3-1/2804” HCO3
-C1-2005,87,21,2 4006,26,61,5 6006,26,31,7 8005,96,12,3 10005,76,12,4 1200,015,66,12,5 1400,015 ,46,12,6 1600,025,36,12,8 1800,055,36,12,8 2000,105,36,12,7 2200,155,26,12,7 2400,205,26,12, 7 2600,245,16,12,7 2800,38B, 1 6.1 2.7300
0.49 5.0 6.1 2.6532
0 0.61 5.0 6.0 2.60
340 0.61 5.0 6.0 2.
60360 0.61 5.0 6.0
2.60 Inflow water 0.61 5.0 6.0 2.6v
: Volume of filtrate vO: Volume of anion exchange resin S: Specific load Table 4 shows the results for the second type of strongly basic anion exchange resin. The depth of the filter bed is 0.6
mz &-40v,,' vO-ho A solution of 1001 NaCl in 1 t of distilled water 5V, and then 85.9 g of sodium sulfate and 1 in 1 t of distilled water.
4. Co-current regeneration of mixed solution 5Vo containing +7 um of hydrogen carbonate (4.1.9'). S=3V/Vo
-Wash with h08Vo distilled water.

The strongly basic anion exchange resin regenerated by the method of the present invention (Table 4) appears to be maintained during the entire treatment cycle at a concentration appropriate to the values in the influent without extreme values of different anions, including sulfuric acid. It has a stable anion composition.

It can be seen from Table 4 that even after the denitrification capacity of the strongly basic anion exchange resin regenerated according to the invention is consumed, no increase in the nitric acid concentration in the filtrate water occurs due to desorption from the filter bed. This is extremely important for the safety of operation of the denitrification equipment.

Table 5 below shows the results obtained with the second type of strongly basic anion exchange resin, with a filter bed depth of 0.6 m.
s S ” 40 v, 'v, + h.1t
A solution containing 100# NaCA in the influent water of 4V.

Co-current regeneration with 4V of a mixed solution containing 85.9.9% sodium sulfate and 14.1.9% sodium bicarbonate in 1 t of influent water. 5=3V/vo-h
, Wash with 8vo inflow water. This regeneration is an economically viable modification.

Even with economical regeneration, the filtrate composition in all parts meets drinking water standards.

A somewhat shorter denitrification cycle is achieved compared to regeneration with 5 volumes of 10% reagent. The cost for removing one nitric acid unit is also low.

Similarly, it is also possible to economically regenerate denitrification filter beds using solutions with the concentrations listed below.

For example, 5 Vo 8 '16 NaCt+ Vo 8%
Mixed regeneration liquid, 5 Vo 8 'Ir NaCt+ 4.
3 Vo 8% Nazso4+ 0.7V.

8% Na HCOs, or 4 Vo 10% Na
C4+4 Vo 10% Na25o4 etc.

Table 6 shows the results obtained with the strongly basic anion exchange resin of the second tights. Filter bed depth 1.05 m
s S= 20 V/Vo・ho 1 t (solution 5 Vo containing 100 g of sodium chloride in D influent water,
Then countercurrent regeneration was carried out by adding 85.9 g of sulfuric acid (IJ) and 14.1 # of hydrogen carbonate (IJ) in 1 t of influent water. 5=3V/Vo-h, 10
Wash with VO inflow water.

As this example shows, it is also possible to regenerate countercurrently according to the invention. However, the denitrification effectiveness of filter beds regenerated in this way is usually lower and the fluctuations in the concentration of other anions in the nitrogen water may be higher.

When polishing a filter bed from fresh, unused anion exchange resin, it is possible to take advantage of the fact that it is in principle already in the chloride form.

For this reason, solutions containing chloride ions are excluded in a pretreatment before use, and the anion exchange resin is contacted with a solution containing sulfate ions or sulfuric acid and bicarbonate ions. The ion exchange resin is thus suitable for initial application and also suitable for regeneration according to the invention.

Table 7 below shows the results obtained with the second type of strongly basic anion exchange resin. The depth of the filter bed is 0.6 m, for which a strongly acidic cation exchange resin is introduced, the depth of the filter bed is 0.15 m and 8 = 20 V/V.
oh (calculated for anion exchange resin). 1
A solution containing 10 (l) of sodium chloride in t of distilled water
vo, then co-current regeneration to 5V of a mixed solution containing 85.911 parts of sodium sulfate and 14.11 parts of sodium bicarbonate in distilled water of IL. 8 = 3V/Vo
・H, Wash with 8 Vo distilled water. A decrease in hardness was also observed due to the cation exchange component. The heavy cation exchange resin forms the bottom layer of the filter. The anion/cation exchange resin ratio is from 4:1 to 12:1. Unlike the use of cation exchange resins, here the reduction in hardness does not provide an overall removal of calcium and magnesium. The anion/cation exchange resin ratio depends on the desired degree of water softening, the ion exchange resin capacity, and the overall composition of the water.

Margin below

Claims (1)

[Claims] 1. In regenerating an ion exchange filter for a water denitrification bed based on a strongly basic anion exchange resin, in the course of the first regeneration step, the strongly basic anion exchange resin is a regeneration solution containing chloride ions, and contacting said filter bed during a second regeneration stage with a regeneration solution containing sulfate ions. 2. The method of claim 1, wherein during the second regeneration step, the regeneration solution also contains bicarbonate ions in addition to sulfate ions. 3. The method of claim 1, wherein after both regeneration steps a third regeneration step is carried out using a regeneration solution containing bicarbonate ions. 4. The ion exchange filter acts as both a denitrification bed and a water softener, the filter bed contains a filter bed based on a strong acid cation exchange resin in addition to a strong basic anion exchange resin, and the first regeneration stage 2. The method of claim 1, wherein in the process both of said filter beds are contacted with a regeneration solution containing chloride ions. 5. The method of claim 4, wherein both of said filter beds are contacted in a second regeneration stage with a regeneration solution containing sulfate ions. 6. The method of claim 4, wherein both of said filter beds are contacted in a second regeneration stage with a regeneration solution containing sulfate and bicarbonate ions. 7. The method of claim 5, wherein within the third regeneration stage the filter bed is contacted with a regeneration solution containing bicarbonate ions. 8. A filter bed based on a strongly basic anion exchange resin and a filter bed based on a strongly acidic cationic resin are separated at intervals, and both are first contacted with a regeneration solution containing chloride ions. The method described in Section 4. 9. The ion exchange filter acts on both the denitrification bed and water softening, and the filter bed is composed of a strong acidic cation exchange resin in addition to a strong basic anion exchange resin, and the filter bed is composed of a strong acid cation exchange resin in addition to a strong basic anion exchange resin. 2. The method according to claim 1, wherein the regeneration solution used for is used as a regeneration solution for a strongly acidic cation exchange resin.