DE2301486A1 - METHODS FOR PURIFYING WASTE WATER, IN PARTICULAR RADIOACTIVELY CONTAMINATED WATER - Google Patents

Description

Patent attorneys
Dlpf.-Ing. R. Ώ Π ETZ «βΓ * ί
Dlpl-Inn. K. LA? -1P ^ REAL

Dr.-In3. R. D Ii 2 1 "Z Jr,
t Manchen 22, Stekudorhtr.1

233-20.O35P January 12, 1973

Ceskoslovenska komise pro atomovou energii, P ra ha (CSSR)

Process for the purification of waste water, in particular radioactively contaminated water

Processes currently known and used for cleaning radioactive waste water or for cleaning water in general are usually based on the use of sorption, possibly also precipitation and coagulation processes. In the first case, it is an application of sorbents of various types, for example according to the principle of ion exchange work (synthetic ionxes, natural Ionexes of inorganic or organic origin), adsorption, deposition of ionic precipitate and like that. In the second case it is a chemical precipitation of macroscopic impurities or at Removal of radioactive trace substances - in order to

233- (S 7759) -Hd-r (8)

309833/0781

precipitation, co-crystallization, formation of isomorphic crystals, and the like. An advantage of sorption methods is mainly based on the possibility of regeneration of most sorbents with relatively simple technological Processes and equipment with generally favorable economic viability of the measures. The coprecipitation procedure are more effective compared to sorption processes, mainly because of the decontamination of water from trace impurities regards; the need to replenish components of carrier precipitation (up to exceeding of the respective solubility product) and the separation of the solid phases formed from the decontaminated Water makes the precipitation and coprecipitation processes technical and economical in a number of cases less beneficial.

The process according to the invention, which is used as a sorption-precipitation process is called, combines the advantages of both cleaning principles, i. H. the benefits of sorption (Regeneration capacity, simplicity of the technical process and the equipment, favorable economy) with ^ the advantages of coprecipitation (high decontamination effectiveness). It was found that by an appropriately chosen Regeneration process, through a suitable composition of the regeneration reagent and the type of sorbent, a high one Decontamination or cleaning efficiency can be achieved while maintaining the principle of the work process, which is characteristic of granular, solid sorbents. There is a demonstrable ongoing Formation of a microcrystalline deposit within the pores and on the surface of the sorbent during the actual decontamination phase of the process, d. H.

309833/0 7 81

ζ. B. when the decontaminated water flows through a column with a fixed bed of the regenerated sorbent. The chemical composition of the precipitate is given by the regeneration process and the composition of the purified water; the regeneration process is then chosen with regard to the composition of the purified water in such a way that a precipitate arises with a maximum entrainment efficiency for the contaminants in question (mechanism of co-precipitation, adsorption and the like) _{or the like}

In particular, the inventive method can the decontamination of wastewater in the extraction of radioactive raw materials are presented; the greatest pollution the usual Ra 226 "

Its reliable removal can, for. B. can be achieved by co-precipitation with BaSOr, PbCO “and the like. Sorption, such as ₀ on strongly acidic Katexen, takes place even, but with lower efficiency or lower selectivity that do not always meet the hygiene safety. It must be noted that the form of the existence of Ra and of radium as a chemical substance in natural water is not clearly given, and that the radium is contained in them partly in a cationic, partly in a colloidal form. This is how natural water differs from synthetically prepared water. The circumstances mentioned are at the same time one of the causes of the lower efficiency of the cleaning by means of ion exchange systems when this water or liquid is deactivated.

According to the invention, a sorbent is used which

309833/0781

230U86

a suitable porosity and shape and chelating and replaceable. Functional groups owns. For example, sorbents based on the mycelium of the sponges of the Penicillium chrysogenum strain, which are solidified by a resorcinol, formaldehyde, urea-formaldehyde, possibly by another resin, which have sorption properties for cations, have proven successful , e.g. B. from heavy metals and from alkaline earth metals and others, distinguish (probably through a replacement mechanism), as well as for electrolytes (probably through a membrane mechanism) ο through their regeneration, z. B * with 0.1-1.0 M solutions Pb (NO „) ₂ , Fe (NO ₃ ) -, FeCl ₃ , BaCl ₃ and the like, sorption of the cationic component occurs, which remains in the biosorbent even after washing with water (The anionic components are removed in this process), in a concentration of about 0.5 to 1 mol / kg or 0.2 to 0.6 mol / l of the biosorbent. If the regenerated (and washed out) biosorbent is contaminated with waste water which is contaminated with Ra, in a dynamic, ie columnar manner, the anionic and cationic components also diffuse against the surface and into the phase of the biosorbent. Thanks to the relatively high concentration of cations (Pb, Fe, Ra and the like) in the phase of the biosorbent and the aforementioned sorption capacity for electrolytes, the result of the contact is a continuous formation of a microcrystalline precipitate, e.g. B. Fe (OH) », PbSOr, Pb (CO_) ₂ , BaSO ^ and the like, inside and on the surface of the biosorbent, accompanied by an explicit reduction in the concentration of Ra 226 in the decontaminated water. As a rule, it is not necessary to add anionic precipitate-forming components to the decontaminated

309833/0781

To top up with water, for example

2 - —2 -

ion SOr, HCO ", CO, HO after reaching the respective solubility products (s. the relatively high concentration of the precipitate forming Kationes in biosorbent), of which sufficient present in their own decontaminated water is _e This has also an economic significance, because the costs of the consumption of Mitfällungsreagentien are by no means negligible Another undoubtedly significant fact is the emergence and simultaneous fixing of precipitation on the surface and within the biosorbent what the problems in separating the "coprecipitates ¹ · triggers of decontaminated water in a technically relatively easily accessible manner _O

After "saturating" the layer of biosorbent follows an elution, combined with a dissolving of the precipitate. The choice of the elution reagent is mainly due to the chemical Given the composition of the precipitate, e.g. B. in the case of iron hydroxide and lead carbonate one can Use diluted mineral acid, for lead sulfate a solution of sodium lye or sodium thiosulfite, or ammonium acetate , for barium sulfate a solution of III-complexone and the same.

In the course of one's own decontamination operation, only part of the precipitating cation becomes one Precipitate is converted, and the rest is bound by functional groups of the sorbent (the lower conversion or degree of conversion is evident from the accessibility of the "inner" functional groups of the sorbent determined, which on the one hand is a consequence of the resulting low

309633 / μ 7 η!

230T486

derschlag, on the other hand by the degree of denaturation im The case of using the above-mentioned biological sorbents is the result of the formation of an "outer" barrier from the precipitate that forms is - however, this efficiency is also sufficient for this - on the order of magnitude

3
10 volumes of water to decontaminate to 1 volume of sorbent.

It has been found, however, that in forming the working cycle of the decontamination process as a whole (the cycle consists essentially of the operations of sorption or retention, elution, regeneration), and that by choosing the elution reagent of an appropriate concentration and composition, e.g. B ₀ for iron hydroxide O, 1N HCl, practically only dissolution of the precipitate and accessibility of the non-regenerated functional groups can be achieved. The regeneration can then be carried out less often, e.g. B. for every third to fifth cycle.

The application of the water purification process according to the invention is, as follows from what has been said, with the Application of a sorbent with the necessary properties, which are given by its structure and character of the functional groups. Specifically, it is above all the following properties: Dependency of the selective sorption coefficient on precipitation-forming cations the pH value, sorption of the electrolytes, sufficient porosity, necessary mechanical resistance and the like. From this point of view, suitable sorbents of organic origin are proteins, polysaccharides, hexosamines and other organic polymers, optionally also synthetically prepared, such as. B. so-called chelating resins.

309833 / 078Ί

230H86

Embodiment 1

The work process is based on the use of the dynamic cleaning process, i.e. the formation of contact between the liquid phase and the biosorbent in a column (with fixed biosorbent bed) with flow from top to bottom. Radioactive natural wastewater became the liquid phase used with approximately the following composition:

266 approx

Ra 2+

2+

Fe ³⁺

Total hardness

temporary degree of hardness permanent degree of hardness Na ⁺

Mn ⁺⁺

U ^nat

200 to 800 pCi / 1000 ml 10 to 50 mg / 1000 ml 2 to 10 mg / 1000 ml 0.2 to 1 mg / 1000 ml

6.8 acidity meq / l 0.8

° German 7.6 alkalinity on

MO mval / l 2.3

grade ° German 6.4 Cl " mg / l 5.5 ° German 1,2 ■ soy " mg / l 15.0 mg / 1 10.0 HCO " mg / l 14O, O mg / 1 5.0 NO; mg / l traces mg / l 0.05 ^N0 2 mg / l traces mg / l 0.02 SiO ₂ mg / l traces ^P ° 4 mg / l traces H ₂ S mg / l traces Ra ²²⁶ pCi / 1 45O-600

10 ml of a type M biosorbent are placed in a column with a diameter of 10 mm and a height of 140 mm.

309833/0 7 8 1

This is initially eluted with 200 ml of 0.1N HCl, with 100 ml Washed out distilled water and then regenerated with 200 ml 0.1M FeCl- and again with 100 ml distilled water washed out. In all of these operations, a specific load 5 is used, i.e. 5 ml / ml Bisorbent ° h. Then follows the operation of actually purifying the above-mentioned waste water by this through the column at a specific load 10

226 flows through. The concentration of Ra in the liquid The phase behind the column increases progressively. After flow of 10 1 it is about 30 pCi / l, and after flow through of about 15 1, the exit concentration is approximately at the level of the entry concentration.

Embodiment 2

Under the conditions mentioned in Example 1, an aqueous solution of the order 10 ~ MPb / N0_ / „, BaCIp and the like can also be used A type M biosorbent can be replaced by a type R biosorbent with the same effect when cleaning.

Embodiment 3

Under the conditions mentioned in Examples 1 and 2, the cleaning process can be simplified in such a way that the regeneration solution is applied cyclically after three or more sorption-elution stages. The number of these between individual regeneration stages must be determined depending on the external conditions of the cleaning.

309833/0 7 81

230H86

Embodiment k

If the regeneration steps are completely omitted in the working method according to example 3, comes there is a decrease in the cycle of the Sorptiona elution stages the penetration capacity of the biosorbent. At the 10th cycle will z. B. achieved the penetration capacity at a flow rate of about 3 l. It follows from what has been said that it is permanent It is necessary to use the biosorbents periodically regenerate"

Embodiment 5

With the arrangement described in Example 1, the purification of waste water from natural uranium can be carried out analogously. The working process is as follows: a column having the biosorbent of the type R or M wl rd initially with 200 ml of alkaline brine eluted (for example, having a composition:. $ 10 NaCl, 0.5 i "Na-CON), after washing regenerated with water mains water with 200 ml 0.1M CaCl-. In all of these operations, a specific load of 3 to 5 is used. Then follows the operation of actually purifying the waste water, which is composed as follows:

U - of course, 1 to h mg / 1000 ml

permanent degree of hardness ° German 1.8

Temporary degree of hardness ° German 10

dissolved substances in the evaporation residue mg / l 329

"" in the ashes 192

Nitrates 24.0

Sulfates 127.5

Chlorides 19.5

309833/0781

" ¹⁰ " 230U86.

Total iron 0.2

Ca ²⁺ 34.1 Mg ²⁺ 0.48

Na ⁺ 33.0 K ⁺ 8.5

pH 7.62

It is advisable to adjust the pH of this natural waste water by adding it before it enters the column by HgSO. to bring the acid value to pH = 3.5. the Concentration of the natural U in the liquid phase behind the column decreases continuously, and with a flow of about 8 1 a value of 0.1 mg U / 1000 ml is reached. After the flow of about 14 l are the inlet and Exit concentrations roughly balanced.

Implementation example 6

The cleaning process can be carried out in a manner analogous to that given in Example 3 so simplify that the regeneration solution is applied cyclically after three or more sorption-elution stages.

309833/0781

Claims (2)

230U86 Claims mt process for purifying wastewater, in particular of radioactively contaminated water, characterized in that a sorbent containing the cations is regenerated by a solution, e.g. B. bischloride, lead nitrate, barium chloride and the like, their cationic Component with anions, optionally with anionic ones Impurities in the purified water, e.g. B. with sulfate, carbonate, bicarbonate, hydroxyl anions and the like, forms a precipitate capable of removing cationic impurities, e.g. B. Ra 226, to be carried away and at the same time to adhere to the surface and within the pores of the sorbent. 2. The method according to claim 1, characterized in that substances of organic origin are used as the sorbent, the proteins, polysaccharides, hexosamines and other organic biopolymers or prepared synthetically, e.g. so-called chelating resins. 309833/0781