FR2491670A1 - PURIFYING DEVICE FOR DECONTAMINATING AQUEOUS EFFLUENTS OF HEAVY METALS - Google Patents

Abstract

THE INVENTION CONCERNS A DEPURATION DEVICE FOR THE DECONTAMINATION OF AQUEOUS EFFLUENTS IN HEAVY METALS. THE DEVICE INCLUDES A CROSS-LINKED HYDROPHILIC COPOLYMER SUPPORT IN WHICH IS INCORPORATED AN AGENT CAPABLE OF COMPLEXING THE SAID HEAVY METALS, SUCH CROSS-LINKED COPOLYMER BEING CAPABLE OF ABSORBING THE SAID EFFLUENTS. THE COMPLEXING AGENT IS ADVANTAGEOUSLY THIO-2-BENZIMIDAZOLE OR THIO-2-VINYL-3-BENZIMIDAZOLE.

Description

The subject of the present invention is a device

  purification system for the decontamination of effluents

aqueous heavy metal.

  More specifically, it concerns the

  purification devices comprising an inert support in which an agent capable of

  to complex the heavy metals present in the ef-

aqueous fluents.

  The most widely used methods

  to remove heavy metals present in ef-

  aqueous fluents consist of absorbing or capturing heavy metal ions, for example mercury, lead, cadmium, copper, silver or chromium, by means of agents capable of forming with these ions

  sufficiently stable complexes.

  Among the chemical agents capable of

  This role, as we know from the article published in BIST 230-231, July / October 1978, pages 203-204, shows that sulfur derivatives are of great interest because they have a high affinity for heavy metals, in particular sulfur-containing derivatives such as thio-2-benzimidazole and its derivatives, for example its

  chlorinated, nitrated and dimethylated derivatives, thio-2-vinyl-2-

  benzimidazole, and thio-ureidobenzimidazole. We

  can also be used as a complexing agent

  no-2-benzimidazole and guanidines.

  However, to facilitate the decontamination operations, it is preferable to incorporate these complexing agents in an inert support to retain on this support the heavy metal ions captured by the complexing agent. Furthermore, it is desirable to be able to then remove the heavy metal ions thus fixed in order to regenerate the purification device.

  The present invention has precisely to ob-

  jet a purification device for decontamination

  heavy metals of aqueous effluents which makes it possible to

  satisfactory decontamination of heavy metals, with the further advantage of being able to

be regenerated easily.

  The device according to the invention is characterized

  in that it comprises a hydrophilic cross-linked copolymer support in which an agent is incorporated

  capable of complexing said heavy metals, said

  crosslinked copolymer port being capable of being

by said effluents.

  Advantageously, the copolymer is a copolymer

  at least one monounsaturated hydrophilic monomer and at least one

minus a polyunsaturated monomer.

  As examples of monounsaturated monomer that may be used, mention may be made of acid

  acrylic acid, methacrylic acid, vinylpyrrolidone

  ne, ethylene glycol acrylate, ethylene glycol methacrylate, diethylene glycol acrylate,

  diethylene glycol methacrylate, the acrylate of

  traethylene glycol, tetraethylene methacrylate

  glycol, polyethylene glycol acrylate and metha-

polyethylene glycol crylate.

  As examples of polyunsaturated monomer

  likely to be used, mention may be made of triacry-

  trimethylol propane, trimethacrylate

  trimethylol propane and pentaeryl tetraacrylate

  thritol. Preferably, the monounsaturated monomer and the polyunsaturated monomer are acrylic monomers

and / or methacrylic.

  According to the invention, the agent capable of

  plexing the heavy metals may be constituted by the sulfur derivatives mentioned above, in particular by the

  thio-2-benzimidazole and its derivatives.

  This complexing agent can be trapped in the crosslinked network of the polymer, for example when it is constituted by thio-2-benzimidazole, or else fixed on the copolymer chain by a covalent bond in the case of thio-2-vinyl- 3-benzimidazole. It is specified that thio-2-benzimidazole is a known product which can be prepared for example according to

  the method described in Organic Syntheses, vol. 4,

  569-570. Thio-2-vinyl-3-benzimidazole can

  be prepared from thio-2-benzimidazole by vi-

  according to a procedure similar to that

  described by H. HOPFF, U. WYSS, H. JUSSI, Helvetica Chi-

  mica Acta, vol. 13, Fasc. 1 (1960), p. 135, for the

  Nylation of nitrogenous heterocycles.

  According to the invention, the content of monomer po-

  lyunsaturated copolymer, which determines its

  cross-linking is important enough to obtain

  It should not be too high so that the aqueous effluents can reach the support and be in contact

  with the complexing agent included in this support.

  Advantageously, a copolymer comprising from 85 to 95% by weight of hydrophilic monomer is used.

  monounsaturated and from 5 to 15% by weight of

unsaturated.

  The complexing agent content of the support is advantageously from 2 to 20% by weight relative to the total weight of the support containing the complexing agent,

  and generally 5 to 15% in the case of thio-2-

benzimidazole and its derivatives.

  The present invention also relates to a method for preparing a purification device

  for the decontamination of aqueous effluents.

  This process consists in forming the crosslinked copolymer support in which the agent is incorporated.

  complexing by polymerization of a solution

  taking at least one monounsaturated hydrophilic monomer, at least one polyunsaturated monomer and an agent capable of

to complex heavy metals.

  Preferably, this polymerization is carried out

  by irradiation of the solution by means of

ionizing events.

  Advantageously, a solution is used

  cool, for example a solution of different mono-

  mothers and the complexing agent in ethanol, and

  the polymerization is carried out under vacuum or in atmospheric

re inert.

  Ionizing radiation likely

  to be used may be made up of

  ultraviolet radiation, radiation, radiation

  y, and electron beams.

  Advantageously, the radiation

cobalt 60.

  In the purification device of the invention

  tion, the inert carrier made of hydrophilic copolymer

  in which the complexing agent has been incorporated, may be in the form of powder, granules,

  film or fiber, obtained by conventional techniques

  c; in this case, the powders, granules, filis or

  are placed or kept in an enclosure

priate.

  According to a variant of the invention, the provision

  cleaning agent may include a fabric or a

  woven such as a felt made, for example, from poly-

  fluorinated mother, made of polyester or polyamide, this fabric or felt supporting the crosslinked hydrophilic copolymer

  in which the complexing agent is incorporated. To obtain

  to hold such devices, the tissue is coated or 1-

  felt of a solution comprising at least one monounsaturated monomer, at least one polyunsaturated monomer and agent capable of complexing heavy metals, then grafting and polymerizing this solution, preferably

  by irradiating it with radiation

  ionizing substances, leading to the formation of a crosslinked copolymer containing the complexing agent, which

  copolymer being grafted onto the fabric or felt.

  Other advantages and features of

  the invention will become more apparent on reading the

  following description, given, of course, as an example

illustrative and not limiting.

  According to the invention, a device is prepared

  purification from a monounsaturated monomer con-

  by acrylic acid and a polyunsaturated monomer

  formed by trimethylol triacrylate

breaded.

  For this purpose, a solution consisting of

  by weight 72% ethanol, 16.2% acrylic acid, 1.8% trimethylol propane triacrylate, and 10%

  a complexing agent consisting either of thio-2-

  benzimidazole, or by thio-2-vinyl-3-benzimidazole

  zole. Thio-2-vinyl-3-benzymidazole was obtained

as follows.

  A mixture containing 0.012 mole of thio-benzimidazole, 0.4 g of mercuric sulfate and 0.24 mole of vinyl acetate is maintained under a nitrogen atmosphere for 2 weeks at 60-70 ° C.

  reaction a first time to eliminate thio-2-

  benzimidazole remaining, and then evaporated under vacuum unreacted vinyl acetate. The residue is taken up in ethanol and then filtered to remove the insoluble mercuric sulfate. After

  evaporation of the ethanol, the thio-2-vinyl is obtained

  3-benzimidazole with a very low yield of 1.2%.

  The melting point of this product is substantially

140WC.

  These solutions are irradiated in vacuum-sealed ampoules, under y-radiation from a source of cobalt 60. The dose received is 2 megarads and is

  delivered at a rate of 0.1 megarad / hour. After ir-

  radiation, recovering the solid phases formed in the bulb, and after drying and grinding they are used for the decontamination of heavy metals aqueous effluents.

  The following examples illustrate the effectiveness of

  solid phases thus obtained. In these examples

  ples, the term "PVB-3" refers to the support in

  which complexing agent is thio-2-benzimidazo

  the, and by PVB-4 the support in which the agent

  plexant is thio-2-vinyl-3-benzimidazole.

  After obtaining resin granules that are yellowish in the case of PVB-3 or whitish

  in the case of PVB-4, these granules are washed successively

  with cold water, hot water, alcohol and then

  the hot alcohol until the disappearance of the agent

  plexant in the filtrates obtained, the agent content

  complexing filtrates being determined by colorimetric

  sorts with a detection threshold of 10 ppm.

  The effectiveness of the supports thus treated for the decontamination of copper or

mercury of aqueous solutions.

  EXAMPLE 1: Copper decontamination tests.

  100 cm 3 of a solution of copper sulphate at 100 ppm of copper and at pH 8, 1 g of the support PVB-3 or PVB-4 are introduced and the mixture is stirred at room temperature.

ambient for 2 hours.

  It can be seen that the copper solutions do not

  from blue to green, quickly in the case of PVB-3 and more progressively in the case of PVB-4, and

  the resins also become green.

  The solution is then filtered and collected

  the first F1 filtrate having a pH of 3.7.

  The PVB-3 or PVB-4 support is then washed.

  the solution with 100 cm3 of distilled water

  stirring for 1 hour, then filter, and

collects the filtrate obtained F2.

  The medium is then washed a second time

  PVB-3 or PVB-4 with 100 cm3 of water containing 10% of

  of hydrochloric acid, for 1 hour with stirring,

  filter and collected a filtrate F3.

  The copper content of each is determined

  filtrates F1, F2 and P3 thus obtained, by colorimetric

trie (reaction with ammonia).

  The results obtained are given in the table

1 below.

TABLE I

Copper content Filtrates

PVB-3 PVB-4

  F1 -20 ppm 10 to 20 ppm F2 10 ppm 10 ppm F3 60-70 ppm 50-60 ppm Residual content is also determined

  thio-2-benzimidazole or thio-2-vinyl-3-benzimidine

  dazole F1 filtrate by the method of Wavelet, and we see that these F1 filtrates contain from 10 to

vpm of complexing agent.

  In view of these results, it can be seen that

  supports of the invention make it possible to eliminate the

  part of the copper, and that, on the other hand,

  Then, it can be recovered by an acidic wash of the support.

  EXAMPLE 2 Mercury Decontamination Test

  In this test, a support of the type

  PVB-4 for the removal of mercury from a

  of mercury chloride HgCl2 at 100 ppm of mercury

cure and at pH 8.

  As before, we use lg of the support

  PVB-4 added to 100 cm3 of the seawater solution.

  curing, and one carries out the same operations as in the case of Example 1 to obtain a first filtrate Fl, then a filtrate F2 'After recovering the filtrate F2 the support is washed with 100 cm3 of an aqueous solution

  10% nitric acid for one hour under stirring.

  then filtered and recovered F3 filtrate.

  As in Example 1, we determine the

  mercury levels of each of the recovered filtrates F1, F2 and F3, by colorimetry using as reagent

dithizone.

  The results obtained are given in the table

2 below.

TABLE 2

  Filtrates Hg content F1 30-40 ppm F2 <10 ppm F3 30-40 ppm

  EXAMPLE 3: Copper decontamination tests.

  In this test, PVB-3 carriers are used

  and PVB-4 which have been regenerated after being used

  for the fixation of copper or mercury.

  For this regeneration, it is washed successively

  the support with hydrochloric acid or nitric acid N / 10, then with distilled water,

  soda N / 10 and finally distilled water.

  The supports thus regenerated are then used.

  res for copper decontamination of a solution

  consisting of 40 ml of a solution of sulphate of

  At this point, 1 g of the support is mixed with 40 ml of the solution, and the same operations are carried out as in Example 1 to recover successively the filtrates F1, F2.

  and F3 and their copper content is determined by

  flame-free atomic absorption trometry to obtain

better accuracy.

  The results obtained are given in the table

paragraph 3 below.

TABLE 3

Copper content Filtrates

PVB-3 PVB-4

  F1 0.25 ppm <0.05 ppm P2 0.10 ppm <0.05 ppm F3 30 ppm 35 ppm Based on these results, it can be seen that

  PVB-4 support provides a high rate of decon-

copper tamination.

  EXAMPLE 4: mercury decontamination

  A regenerated PVB-4 support is used as in Example 3, and 1 g of this support is mixed with 100 ml of a 90 ppm HgCl 2 mercury solution.

mercury and at pH 8.

  The same operations as in Example 2 are carried out in order to recover the filtrates F1, F2 and F3, and the mercury content is determined on each of these filtrates by atomic absorption spectrometry.

without flame.

  The results obtained are given in the table

4 below.

TABLE 4

  Filtrates Mercury content (ppm) F1 9 (pH = 5.8)

F2 0.26

F3 60

Claims (13)

  1. Purification device for decontaminating   heavy metals of aqueous effluents, characteris-   in that it comprises a hybrid copolymer support   crosslinked drophilic in which an agent is incorporated   capable of complexing said heavy metals, said   cross-linked polymer being capable of absorbing said ef- fluent.   2. Device according to claim 1,   characterized in that the copolymer is a copolymer acrylic and / or methacrylic.   3. Device according to any one of the   Claims 1 and 2, characterized in that the copoly-   hydrophilic mother is a copolymer of at least one mono-   monounsaturated hydrophilic mother and at least one polyunsaturated monomer.   4. Device according to claim 3,   characterized in that the monounsaturated monomer is acrylic acid.   5. Device according to any one of the   Claims 3 and 4, characterized in that the monomer   polyunsaturated is trimethylol propyl triacrylate born.   6. Device according to any one of the   claims 1 to 5, characterized in that the agent   to complex the said heavy metals is thio-   2-benzimidazole or thio-2-vinyl-3-benzimidazole.   7. Device according to any one of the   Claims 1 to 6, characterized in that the support is a copolymer of 85 to 95% by weight of monomer   monounsaturated hydrophilic and 5 to 15% by weight of Polyunsaturated name.   8. Device according to any one of the   Claims 1 to 7, characterized in that the content of the carrier medium capable of complexing said heavy metals is from 2 to 20% by weight relative to the weight   total of the medium containing said agent.   9. Process for the preparation of a purification device for the decontamination of effluents   aqueous composition according to any one of claims 1   8, characterized in that the support is formed into   cross-linked hydrophilic polymer containing the common   plexant by polymerization of a solution comprising at least one monounsaturated hydrophilic monomer, at least   a polyunsaturated monomer and an agent capable of plex the heavy metals.   10. The method of claim 9, wherein   in that the polymerization is carried out by irradiation of the solution by means of ionizing radiation.   11. Process according to any one of the   9 and 10, characterized in that the solution is an alcoholic solution.   12. Process according to any one of the   9 to 11, characterized in that one carries out   polymerization under vacuum or inert atmosphere.   13. Use of the purification device   according to any one of claims 1 to 8, for   Copper or mercury decontamination of aqueous effluents.