CS240900B1 - Regeneration method of ionex filters - Google Patents

Abstract

A strongly basic anionic ion exchange filter for denitrification and optionally softening of water is regenerated by contact successively in a first stage with a solution containing chloride ions and in a second stage with a solution containing sulphate or sulphate and hydrogen carbonate ions. If a cationic ion exchange filter for simultaneous softening of water is present, it may be regenerated by solutions from the anionic filter regeneration. The invention is applicable in water treatment for drinking purposes and in the production of beverages. Preferred sources of the chloride, sulphate, and hydrogen carbonate ions are NaCl, KCl, Na2SO4, K2SO4, NaHCO3, and KHCO3.

Description

This invention relates to a method of regenerating ion exchange filters odstoanování nitrates, ^{beta at} pH farm is considerably tordosto components from water.

The ever-increasing nitrate content of natural waters is becoming a major problem in the past. Nitrates of not ^l 'of the water · ODS ANOVA ^{t tr} conventional vortórenskými. ix-ups, are not ot ^b for natural, ie 'ultimate aerobic .podnínek and therefore a stable product of the conversion of nitrogen compounds in soil and. water. A number of sources of nitrogen compounds is most wholesale change ^pl UN ^Star oxalate ^{or I} and ^P ^ lika ^Affairs dus atých RUM ^{P y L} HNO ovýc ^h ^ vv agriculture.

Nitrates cause health disorders and even fatal diseases in humans and warm-blooded animals. The best known is the effect of nitrates on the formation of so-called nitrate alimentary methomoglobinaemia, which may occur in infants under three months of age when prepared with an artificial diet of water containing more than 15 ^m g ^{.l NO} . It · ^No s.norm ^{and BC} ipou ^STi 'to 50 mg.! · ^N0. Similar foreign standards also permit higher concentrations than the stated limit for infants. In adults, higher nitrate concentrations in drinking water cause cancer of the esophagus, stomach and bladder. They could be . the cause of abortion of cows and fatal poisonings of artificially nourished calves. Nitrates in water also have an adverse effect on the food industry (eg in germination of malt), in the preservation of foodstuffs and the production of beverages.

In addition to nitrates, the hardness components are defective if their content in the treated water exceeds the values given by the standard for drinking water. • In addition, they are a defect in some food processing plants, where higher hardness causes eg.

- 2 turbidity of drinks. 240 900

One way to remove nitrates from water is to use ion exchangers. Their common advantage is the independence of water temperature, satisfactory reaction rate, high efficiency and the course of denitrification without the addition of foreign substances and without the need for anaerobic environment. In most cases, however, the content of other anionic components of water is adversely affected. The most common is the use of a strongly basic anion exchanger in chloride form itself. However, its disadvantage is the high chloride content of the filtrate, especially at the beginning of the working cycle

The anion exchanger of this type exchanges all the anions present with the chloride anion.

The content of these chlorides in the treated water then exceeds the values set by the drinking water standard. The filtrate is essentially a chloride denaturate that can cause physiological problems. Conversely, sulphates are removed from the treated water together with nitrates. Hydrogen carbonates are also partially removed, so the water quality is substantially changed. However, the advantage of using this chloride form of the anion exchanger is its easy regenerability. During bed regeneration, nitrates are already washed out with eight volumes of 10% sodium chloride solution.

The use of the strongly basic anion exchanger itself in the hydrogen carbonate form is also disadvantageous _(due to the high content of hydrogen carbonates in the filtrate. chlorides well above the input concentration due to their gradual desorption from the ion exchange bed.

However, this entails exceeding the standard values of chloride in the filtrate for inlet waters with higher chloride concentrations. Sulphates are removed completely and their concentration increases with increasing nitrate concentrations. Another disadvantage of the strongly basic anion exchange resin in the hydrogen carbonate form is its poor regenerability. In the regeneration phase, the nitrates of 3 240 900 are washed out after the application of 23 volumes of 10% NaHCO 3 measured by the volume of anion exchange resin.

The use of regenerated mixed chloride-hydrogen carbonate beds of a strongly basic anion exchange resin is also known. Their advantage is that both the chlorides and hydrogen carbonates, ie two anionic components, are already present in the filtrate already in the desire of the working (sorption) phase. However, sulphates are again removed together with nitrates. The filtrate is therefore a chloride-hydrogen carbonate denaturate. As a result of chloride desorption in the second half of the working phase, the standard chloride concentration in the filtrate is again exceeded if there is a higher chloride concentration in the inlet water (albeit in the drinking water standard).

Similarly, in the removal of nitrates via an anion exchange resin in the sulfate cycle, all anions are exchanged for sulfate ion at the beginning of the working period.

Furthermore, a weakly basic anion exchanger in hydrogen carbonate form is used for denitrification of drinking water. However, this process has other disadvantages besides excess hydrogen carbonate ion in the filtrate and chloride ion desorption in the second half of the process cycle and sulphate suppression. On comparable waters, the denitrification capacity of a weakly basic anion exchange resin is about a quarter of that of a strongly basic anion exchange resin. If the treated water flows through an anion exchanger of this type, but which has already exhausted its denitrification capacity, the captured nitrates from the ion exchanger spontaneously wash out and the outgoing water is thus enriched with nitrates.

From the known ion exchange nitrate removal methods from water, an optimum method appears to be the most effective method, such as No. 200 907, which allows only nitrates to be removed selectively by means of the ion exchange resin while retaining the other anionic components of the water.

This method uses three forms of a strongly basic anion exchange resin _; namely chloride, sulfate and hydrogen carbonate, which are mixed to a certain extent. A significant disadvantage of this

However, the 4 240 900 process is that the bed obtained cannot be regenerated and all three ion exchange forms must be separately prepared once exhausted. Therefore, this method can only be used for small, single-purpose devices, for example for the denitrification of drinking water in the home, usually for the preparation of artificial food for infants. After exhaustion, this bed is discarded.

This implies that economical processes with easy anion exchange regeneration remove nitrates at the expense of deteriorating the physiological properties of water and, conversely, a method that removes nitrates selectively cannot be applied on a larger scale.

These drawbacks are solved by the proposed method of regeneration, which allows repeated use of an ion-exchange bed, which selectively removes nitrates and possibly also removes hardness components. The principle of the regeneration process consists in that the denitrification filter based on a strongly basic anion exchange resin or a denitrification and softening filter whose denitrification part is based on a strongly basic anion exchanger and the softening part is based on a strongly acidic cation exchanger ^ is brought into contact in the first stage of regeneration; a regenerating solution containing chloride ions, preferably a sodium or potassium chloride solution and, in a second phase, a solution containing sulfate ions, preferably a sodium or potassium sulfate solution, or successively or simultaneously with a solution containing sulfate ions, preferably sodium sulfate or potassium and hydrogen carbonate ions, preferably hydrogen carbonate, such as those used in the regeneration process, in that they allow, under economically advantageous conditions, the use of strongly basic anion exchangers to selectively remove nitrates from the water while maintaining other anionic components and hence physiological values. y water. Due to the relatively simple regeneration process, this method can be reused and on a larger scale. In the case of simultaneous denitrification and reduction of water hardness (eg for industrial preparation of beverages), this method is also economically advantageous in that the anion exchange regeneration solution is also used for the cation exchange regeneration. ’

In the first phase of the regeneration cycle, the effective desorption of the nitrates retained in the previous working cycle is carried out with only a relatively small amount of the solution containing chloride ions. The anion exchange resin is converted into the chloride form predominantly at this stage. In the case of regeneration of the denitrification and softening filter, the anion exchanger regeneration agent is used simultaneously to regenerate the cation exchanger, or vice versa. In the next stage of regeneration, the strongly basic anion exchanger is converted from the chloride form to a mixture of various forms of anion exchanger and the last nitrate residues from the working cycle are desorbed. At the same time, the cationic component of this second solution may optionally regenerate the cation exchanger.

•

Tables 1 and 2 serve to prove the effect of the bed regenerated according to the invention. Table 1 shows the composition of the filtrate after the bed of strongly basic anion exchange, regenerated only into the chloride cycle. The amount of filtrate in the first column is expressed in multiples of the volume of anion exchange resin used in the filter bed. Table 1:

Amount of filtrate Filtrate composition mmol.l

v.vý 1 1 1 m i | Й | 1 and 1 1/2 SO ^ HCO 01 20 May 0 0 0.2 5.8 40 0 0 0.3 5.7 60 0 0 0.3 5.6 80 0 0, 0.4 • 5.6 100 ALIGN! 0 0 0.6 5.4 120 0 0 1.1 4.9 140 0.01 0 1,8 4.2 160 0.03 0 2.2 3.8 180 0.07 0 2.4 3.6 200 0.20 0.1 2.3 3.4 220 0.36 0.3 2,0 3.3 240 0.55 0.55 1,8 3.1 inlet water 1.53 0.94 Ι, θ 0.8

- 6 continued Table 1

240 900

Filter bed: strongly basic anion exchanger of the second type, column height 0,6 m, s = 20 VV “\ Co-regenerated with 8 V _Q solution of 100 g NaCl in 1 liter of distilled water at s = 3 VV” lh ”l. Wash out 8 V _{Q of} distilled water. V = filtrate volume V_ = anion exchange volume s = specific load ⁰

Table 2 shows the composition of the filtrate after the anion exchange bed regenerated according to the invention. The amount of filtrate in the first column is expressed in multiples of the volume of anion exchange resin used in the filter bed.

Table 2:

Amount of filtrate vv; ¹ N0 ₃ filtrate composition 1/2 SO ^ mmol.l ^ hco ₃ Cl 20 May 0 1.3 3.5 1,2 4q 0 1.4 3.2 1.4 60 0 2.3 2.3 1.4 80 0 2.8 1.9 1.3 100 ALIGN! 0 3.1 1,8 1.1 120 0.01 3.4 1,8 0.8 140 0.05 3.3 1,8 0.8 160 0.12 3.2 1,8 0.8 180 0.24 3.3 1,8 0.8 200 0.40 3.0 1,8 0.8 220 0.52 2.9 1,8 0.8 240 0.66 2.7 Ι, θ 0.8 inlet water 1.53 0.94 1,8 0.8

Filter bed: strongly basic anion exchanger of the second type 0,6 m high. Co-regenerated with 5 V _Q solution containing 100 g NaCl in 1 liter of distilled water and then with 5 V _Q mixed solution containing 85,9 g Na ₂ SO ₄ + 14,1 g NaHCO ₃ in 1 liter of distilled water at s = 3 VV · lh \ Eluted with 8 V _{Q of} distilled water. V = VZ filtrate volume - ion exchange volume s = specific load ⁰

- 7 From the values in Tables 1 and 2 results: For a 240 900 ^b EMA filters doctózí ^significant removal usičnanů ^{d. Z} and second ^FIL three ^(Table 2) is' however: zloven contained ^{OTHERS h} c ^h anions represented fairly evenly and in any proportion does not exceed drinking water standards. For the first filter along with ^'d US ^IR nan ^{t y} ODS sulfates ^and Ny is ^a n ^d r ^y and in the RDP ^{e p} s ^{i l} a n ^{e p} ROVISIONAL ^¹H on.

cycle * and the vast majority of hydrogen carbonates. The filtrate is chloride denaturate; Contains 4 - 7 times more chloride than inlet water and does not fully comply with the drinking water standard (2.82 mmol.l)

The following Tables 3 to -6 show examples of how to perform regeneration together with the results of the bed.

obtained on. regenero-abulka 4

Amount of filtrate ^L marries ^{d filt} r ^at u mmo ^l "^ Cl ' VV ' ¹ 0 NO ^ 1/2 SO “ HCO 2 20 May 0 0.1 1.05 0.50 40 0 0.1 1.0 0.50 60 0 0.15 0.85 0.65 80 0 0.20 0.70 0.80 100 ALIGN! 0 C, 25 0.55 0.85 120 0.01 0.25 0.5C 0.90 140 0.01 0.30 0.45 0.87 160 0.06 0.50 0.40 0.60 180 0.10 0.80 0.40 0.30 200 0.25 0.85 0.40 0.10 220 0.90 0.30 0.25 0.05 260 1.40 0.10 0.10 0 280 1.60 0 0 0 300 1.60 0 0 0 inlet water - / 1.60 0 0 0

V = volume of filtrate V- = volume of ion exchange resin with specific = ⁰ en LOAD ^{Iz s}

Table No.3 are 'describes the results of a strongly basic anion exchange resin of the second type, the filling height of 0.6 m, with VV = 45 ^ - .h This ^stork n l ^{n would} re la aouproudně ^g enerována 5 extended _Q · ^t ^ okx ^containing 100 g sodium chloride liter of distilled water and further five Vq mixed solution containing 85.9 g sulfate sod- 8,240,900 Joint а 14.1 g sodium hydrogen carbonate liter of distilled water. Wash out 8 V _{Q of} distilled water.

Furthermore, an artificial feed water solution was prepared which contained sodium nitrate at a concentration of 100 mg.NO2 in distilled water, i.e. without further anionic components. Although only nitrate salt is present in the inlet water, the water after passing through the bed regenerated according to the invention contains chlorides, sulphates and hydrogen carbonates in an amount corresponding to the drinking water standard, which proves that even in this extreme case, If such a filter is regenerated, it is proven to replace nitrates with the main anionic components of the eye.

Table 4

Amount of filtrate Filtrate composition mmol.l

VV ' ¹ 0 1 m i O i Й 1 1 1 1 1/2 SO = HCO " Cl 20 May 0 5.8 7.2 1,2 40 0 6,2 / 6.6 1.5 60 0 6.2 6.3 1.7 80 0 5.9 6.1 2.3 1C0 0 5.7 6.1 2.4 120 0.01 5.6 6.1 2.5 140 0.01 5.4 6.1 2.6 160 0.02 5.3 6.1 2.8 180 0.05 5.3 6.1 2.8 200 0.10 5.3 6.1 2.7 22C 0.15 5.2 6.1 2.7 240 0.20 5.2 6.1 2.7 260 0.24 5.1 6.1 2.7 280 0.38 5.1 6.1 2.7 300 0.49 5.0 6.1 2.65 320 0.61 5.0 6.0 2.60 340 0.61 5.0 6.0 2.60 360 0.61 5.0 6.0 2.60 inlet water 0.61 5.0 6.0 2.6

V = filtrate volume V _rt = ion exchange volume s = specific load ⁰

Table 4 shows the results with strongly basic results

- 9 240 900 anion exchanger of the second type, filling height 0,6 m, s = 40 VV ^ .h ¹ . Co-regenerated 5 V _Q solution containing 1C0 g NaCl vil distilled water and sweat 5 V _Q mixed solution containing 85.9 g sodium sulphate and 14.1 g sodium bicarbonate v.1 l distilled water at s = 3 VV ”\ h” \ Wash out 8 V _{Q of} distilled water.

The strongly basic anion exchange regenerated by the process of the invention (Table 4) has a balanced anionic composition, without the extreme values of the individual anions, including sulphates, which are maintained throughout the working phase at concentrations appropriate to the input values. Table 4 further shows that upon exhaustion of the denitrification capacity of the strongly basic anion exchanger regenerated according to the invention, there is no increase in nitrate concentration in the filtrate by their spontaneous desorption from the filter bed. This is very important for the safety of denitrification equipment operation.

Table 5

Amount of filtrate vv; ¹ slo N0 ^ filtration 1/2 S0 = mmol.1 1 HCO3 Cl AND 20 May 0.006 2.9 7.5 2.7 40 0.006 3.5 6.8 2.8 60 0,010 ⁴ 4.2 6.45 2.6 .80 0.010 4,5 6.20 2.6 100 ALIGN! 0.016 4.8 6.20 2.5 120 0.018 4.8 6.20 2.3 140 0,025 4.7 6.15 2.3 160 0.050 4.65 6.15 2.3 180 0,096 4.65 6.10 2.2 200 0.150 4.6 6.10 2.2 220 0.180 4.6 6.10 2.2 240 0,2.50 4.6 6.10 2.2 260 0.320 4.55 6.10 2.2 280 ₍ 0.43 4.50 6.10 2.2 inlet water 0, 61 4.40 6.00 2.1

V = filtrate volume V _n = ion exchange volume s = specific load ⁰

- 10 240 900

Table 5 shows the results with a strongly basic anion exchanger of the second type, a fill height of 0.6 m, s = 40 VV / h concurrently regenerated with only 4 V _Q solution, 100 g NaCl vial of input water and then only 4 V _Q mixed solution 85> 9 sodium sulphate and 14.1 g sodium bicarbonate in 1 mL of input water at s = 3VV / h. Eluted with 8 V _Q inlet water. This regeneration is an economically advantageous variant.

Even with economical regeneration, the filtrate composition in all proportions complies with the drinking water standard. A somewhat shorter cdenitrification cycle is achieved against regeneration with five volumes of 10% reagents. However, the specific costs of the nitrate unit removed are also lower.

Similarly, it is possible to economically regenerate the denitrification bed with concentration solutions - for example: 5 V _Q 8% NaGl + 5 V ₍ 8% mixed regenerant, 5 V _Q 8% NaCl + 4.3 V _Q 8% Na ₂ SO 4 + + 0, 7 V _by 8% NaHCO 3 or 4 V _Q 10% NaCl + 4 V _Q 10% Na ₂ SO ₄ and the like.

Table 6

The amount of filtrate reduced the filtrate mmol.l.

1 1 1 1 1 1 1 1 1 1 «4 1 1 o 1 and > 1 1 1 1 N0 " 1/2 SO4 HCO 2 Cl 20 May 0,048 1.00 3.6 2,0 40 0,048 0.90 3.45 2.25 60 0.052 0.90 3.30 2.42 80 0,055 0.90 3.25 2.55 100 ALIGN! 0,059 0.95 3.25 2.55 120 0,063 1.05 3.1 2.45 140 0,070 1,25 3.0 2.20 160 0,085 1.60 2.9 2.00 180 0,085 1.80 2.7 1.90 200 0,090 2.00 2.4 1.90 220 0.11 2.25 2.1 1.85 240 0.13 2.35 2.1 1.80 260 0.18 2.40 2.1 1.80 inlet water 0.516 2.08 2.05 1.77 V = filtrate volume V = volume ionex s = specific 0 load

- 11 240 900

Table 6 shows the results with a strongly basic anion exchanger of the second type, a filling height of 1.05 n, s ^with 20 V ~ h H.. Regenerated countercurrently 5 In a solution of 100 g sodium chloride villas incoming water and then 5 V _Q of the mixed solution of 85.9 g of sodium sulfate and 14.1 g of sodium hydrogen carbonate water at the inlet of villas and VV = 3 "^. H" * · ·. Wash 10 V _{Q of} inlet water.

As can be seen from this example, the method according to the invention can also be regenerated countercurrently, but the denitrification efficiency of the bed thus regenerated is generally lower and the variation in the concentration of other anions in the filtrate may be greater.

When preparing a bed from a new, unused anion exchanger, the fact that it is supplied predominantly already in chloride form is utilized. Therefore, in the first treatment, before use, the chloride anion solution is omitted and the anion exchanger is only contacted with a solution containing sulfate, or sulfate and hydrogen carbonate ions. In this way, the ion exchanger is prepared for the first application and for further regeneration according to the invention.

Table 7

The amount of filtrate V.V ^'1 0 1 1 1 i m 1 o 1 1 1 The composition of the filtrate was mmol 1/2 S0 = HCO 2 Cl 1/2 T _o 20 May 0 1.3 3.5 1,2 0 ^ 02 40 0 1.4 3.2 1.4 0.02 60 0 2.3 2.3 1.4 0.02 80 0 2.8 1.9 1.3 0.15 100 ALIGN! 0 3.1 1,8 1.1 0.24 120 0.01 3.4 1,8 0.8 0.34 140 0.05 3.3 1,8 0.8 0, 40 160 0.12 3.2 1,8 0.8 0.70 180 0.24 3.3 1,8 0.8 0.90 200 0.40 3.0 1,8 0.8 1.20 220 0.66 2.7 1,8 0.8 2.40 240 0.66 2.7 1,8 0.8 2.40 inlet water 1.53 0.94 1,8 0.8 5.20

V ^s filtrate volume VI = ion exchange volume s = specific load ⁰

- 12 240 900

Table 7 shows the results with a strongly basic anion exchanger of a second grade, 0.6 m high, followed by a strongly acidic cation exchanger, a filling height of 0.15 m, s = 20 VV * \ hT \ calculated on the anion exchanger. Co-regenerated with 5 V _{of a} solution containing 100 g of sodium chloride in distilled water and then with 5 V _{of a} mixed solution containing 85.9 g of sodium sulphate and 14.1 g of sodium bicarbonate in one liter of rain, water at s = 3 VV ^ .h “ ¹ . Eluted with 8 V _Q distilled water. Due to the cation exchange component, a decrease in hardness is also observed. The heavier cation exchanger forms the bottom layer of the filter. The ratio of anion exchanger to cation exchanger is 4 J 1 to 12: 1. Unlike cation exchanger in the energy sector, reducing the hardness of drinking water is not a complete removal of calcium and magnesium. The anion exchange - cation exchange ratio is determined by the desired degree of water softening, ion exchange capacity and overall composition.

Claims (1)

SUBJECT OF THE INVENTION 240 900 A method of regenerating ion exchange filters for denitrification of water based on a strongly basic anion exchange resin, or an ion exchange filter for denitrification and water softening, the denitrification portion of which is based on a strongly basic anion exchange resin and the softening portion is based on a strongly acidic cation exchange resin. a strong basic anion exchanger, or a strong basic anion exchanger and a strongly acidic cation exchanger, in a first phase of regeneration, contacting a regeneration solution containing chloride ions, preferably a sodium or potassium chloride solution, and in a second phase, contacting a solution containing sulfate ions , preferably with a sodium or potassium sulfate solution, or simultaneously or sequentially with a solution containing, on the one hand, sulfate ions, preferably sodium or potassium sulfate, and, on the other hand, hydrogen carbonate ions, preferably sodium or potassium hydrogen carbonate.