IE904387A1 - Method for water treatment with simultaneous flocculation¹and adsorption with the aid of partially hydrophobic¹polyelectrolytes - Google Patents

Abstract

Water treatment process using gels (I) and/or cationic polymers which are at the same time flocculating agents and adsorbent agents. in which x = y - z 0 < y < 1 0 < z < 0.1 1

Description

The present invention relates to a method for water treatment using partially hydrophobic polyelectrolytes which are simultaneously flocculating agents and adsorbants.

The treatment of water, in particular industrial, domestic and drinking water, consists in removing, in particular, suspended particles, pathogenic microorganisms and molecules in solution which may prove dangerous on consumption of the water, or for the environment in the case of waste.

The following are found amongst the methods for removing the above elements: - coagulation or flocculation, which enables suspended particles (clay, silica, etc) to be collected in the form of large flakes or floes, followed by settling and then a filtration permitting removal of the floes.

The following may be mentioned as examples of flocculating agents: ferric chloride, aluminium sulphate, aluminium salts, and, in particular, those described in EP—A-327,419, and water-soluble polyelectrolytes, such as products obtained by chloromethylation of polystyrene followed by amination with the aid of a tertiary amine as described in C.A.S 94(16) 122281d, C.A.S 89(12) 908 26p, C.A.S 78(10) 62 023d.

- Oxidation, the aim of which is essentially to remove organic matter and to disinfect the water by - 3 destroying the pathogenic microoganisms by means of, for example, H2O2, O3, Cl2, C102 or NaClO.

- The removal of organic molecules in solution, such as aromatic compounds, by adsorption with adsorbants such as active charcoal, which can also act as a filter for the residual suspended matter.

As indicated above, the various methods aim to remove undesirable particles or elements. In order to carry out a complete treatment of naturally occurring water, it will very often be necessary to use the 3 methods described above.

The present invention relates to a method for the treatment of naturally occurring or waste water which enables the suspended particles and organic compounds in solution to be removed simultaneously.

The method uses partially hydrophobic polyelectrolytes which are, at one and the same time, flocculating agents for inorganic and/or organic suspended particles and adsorbants for dissolved organic compounds.

The flocculating and adsorbing agents used in the present invention are partially hydrophobic polyelectrolytes. They may be cationic polystyrene gels and/or straight-chain cationic polymers.

The cationic polystyrene gels according to the invention are partially crosslinked styrene polymers carrying alkylamine, preferably methylamine or ethylamine, CH2-CH) (CH2 CH (01 O Rl ( ch2 ) n—R2 C1©\R3 - 4 groups, which can be represented by the following formula (I): -v_^CH2-CH) — Ύ —(CH2-CH^ in which x = y + z 5 O < y < 1 o < z < o.l £ n < 5 and preferably n < 2 and Rlz R2 and R3, which may be identical or different, being a hydrogen atom or an alkyl group having from 1 to 10 carbon atoms, preferably methyl or ethyl or hydrogen.

The synthesis of products carrying methylammonium groups is described, in particular, in French Patent Specification 2,190,860.

R can be the result of a chemical bridging between 15 the chains or can originate from side reactions during the amination process.

The degree of crosslinking DCr is defined by DCr (t) = 100 X z (I) The degree of cationicity DCa is defined by DCa (%) = 100 X y. - 5 The degree of swelling Q of the cationic gel in deionised water is expressed as g of water absorbed per g of dry polymer.

The straight-chain cationic polymers according to 5 the invention are cationic polymers derived from styrene which correspond, in particular, to the following formula: (II) in which 0.3 < x < 1 £ n < 5 and preferably n < 2 Rlr r2 and R3, which may be identical or different, being a hydrogen atom or an alkyl group having from 1 to 10 carbon atoms, and preferably ethyl or methyl.

They may be obtained by nucleophilic substitution of chlorine by an amine or by ammonia carried out on chloroalkylstyrene (and styrene) (co)polymers.

The degree of cationicity DCa of the straight-chain cationic polymers is defined by DCa (%) = 100 X x.

As indicated above, the partially hydrophobic polyelectrolytes are capable of simultaneously removing suspended particles and organic compounds or micropollutants - 6 in solution in the water.

The implementation of the method for water treatment according to the invention using the above flocculating and adsorbing agents can in general be similar to that using aluminium salts as flocculating agents. The flocculating and adsorbant agent or agents is or are introduced into the agueous medium to be treated, which should then be agitated in order to ensure a good dispersion and a good contact between the agent or agents and the particles and compounds to be removed.

The agitation should be adjusted so as to maintain a good compromise between the development of floes and their mechanical destruction due to too rapid agitation.

The floes can be allowed to settle, filtered off 15 and the purified supernatant recovered.

The amount of flocculating and adsorbing agent necessary to purify the water depends on its degree of cationicity DCa and its degree of crosslinking (in the case of cationic gels).

In general, the higher the DCa the smaller the amount of flocculating and adsorbing agent necessary for flocculation/adsorption.

The partially crosslinked polystyrene gels carrying alkylamine groups according to the invention are good adsorbants; this is the case even without there being suspended particles present in the medium which are capable - 7 of flocculating.

Moreover, compared with active charcoal, they have the advantage of adsorbing the dissolved compounds more rapidly.

The following Examples further illustrate the present invention.

ECAMELE_J= A - Adsorption effect of the gels An agueous suspension of gel (SAMPLES A to D) having a concentration of between 0.1 and 0.35 g of gel sec/1 of deionised water is prepared in a screw-top tube with TeflonR cap.

A solution of pyrene in ethanol (concentration122.5 mg of pyrene/1 of ethanol) is added. The pyrene concentration in the suspension is 0.15 ppm.

The suspension is agitated for about one hour by rotary agitation of the tube ( « 1 rev/10 sec). The supernatant is then separated from the gel by filtration through a metal grating of 63 μπι mesh under atmospheric pressure.

The gels for SAMPLES A to D are partially crosslinked polystyrenes carrying methylammonium groups with R j — R2 — R3= H · They are prepared in accordance with French Patent 25 Specification 2,190,860 and their characteristics are indicated below.

Sample No. DCr (%) DCa (%) Q (g/g) A l±0.5 92±5 300±30 B 2±0.5 92±5 120±10 C 3±0.5 92±5 70±10 D 2±0.5 50±5 40±5 The pyrene contained in the supernatant is 10 determined by UV spectroscopy and the adsorption A of the micropollutant by the gel is calculated: initial micropollutant concentration micropollutant concentration in the supernatant A (%) = 100 X -----------------------------------initial concentration Cp - Cs = 100 X --------Cp B - Adsorption and flocculation effects of the gels An agueous silica suspension having a silica concentration of 4 g per 1 of deionised water is prepared in a screw-top tube with a Teflon cap.

The silica used, which is washed with deionised 25 water before it is used, is a precipitated silica consisting of spherical particles having a radius, for 90% of said - 9 particles, of between 10 and 80 nm and corresponding to a number average of 33 nm. Its specific surface area is 35 m2/g and its mass per unit volume is 2.2 g/cm3.

The addition of the micropollutant is carried out 5 in a manner identical to that described in I.A. The suspension is agitated rapidly for 30 seconds in order to homogenise it and is then agitated by rotary agitation of the tube («20 rev/min) for 30 min.

The concentration Cs of the micropollutant (pyrene) in the supernatant after centrifuging is determined by UV spectroscopy. The adsorption corresponding to each Cp is calculated.

The gels tested are SAMPLES A to D as defined in EXAMPLE I.A.

The adsorption values are identical to those obtained under A (see Table I).

For SAMPLES A, C and D, the optimum flocculation o.f.c. corresponding to the ratio of the minimum amount of flocculating and adsorbing agent to be introduced into the water to flocculate the maximum amount of suspended particles is determined. The o.f.c is expressed in mg of dry gel introduced per g of silica removed.

The results are collated in Table II.

The dry gel of Sample B is taken up and ground for min using the Ultra-TurraxR method at low speed on the one hand and at high speed on the other hand. The o.f.c is - 10 determined for each of the grindings; the results are collated in Table III.

EXAMPLE 2 A - Adsorption effect of the gels 5 The operating method described in Example l.A is repeated using 1-hydroxyanthraguinone as micropollutant present in the agueous suspension in an amount of 0.7 ppm.

The adsorption of 1-hydroxyanthraquinone is determined by the method indicated in l.A on Samples A, B and D.

The results are collated in Table IV.

EXAMPLE 3 A - Adsorption and flocculation effects of the straightchain polymers An agueous silica suspension having a silica concentration of 5.3 g/1 of deionised water is prepared. The silica used has the same characteristics as those described in l.B.

An agueous polymer solution (SAMPLES E to H) and a solution of pyrene in ethanol (concentration 122.5 mg/1) are prepared and added to the suspension under the same conditions as described in l.B.

JThe polymer concentration in the mixture is varied between 0.01 and 0.2 g/1, the pyrene concentration being fixed at 0.15 ppm.

The polymers of Samples E to H are obtained by free - 11 radical (co)polymerisation of chloromethylstyrene (and styrene) followed by a nucleophilic substitution of chlorine by triethylamine in the presence of chloroform.

Their characteristics are summarized below.

Sample No. DCa (*) MW E F 100 77 18 000 7 500 10 G H 45 35 10 000 10 000 The suspension is agitated rapidly for about 1 hour and the supernatant is then separated from the floes by centrifuging (15,000 g for 1 hour).

For each Cp, the concentration Cs of the micropollutant (pyrene) in the supernatant is determined by UV spectroscopy and the corresponding adsorption A is calculated.

The results are collated in Table V.

The o.f.c is determined for each of the Samples E to H. The o.f.c is expressed as g of polymer introduced per g of silica removed.

The results are collated in Table VI.

B - Flocculation effects of the straight-chain polymers A synthetic water of Seine-water type is prepared, - 12 consisting of: Twice-exchanged water filtered at 0.45 μιη 2 1 Na2CO3 672 mg Na2SO4 148 mg CaCl2,6H2O containing 80 g/1 of Ca2+ 2 ml MgCl2,6H2O containing 48.6 g/1 of Mg2+ 0.5 ml Humic acid (disodium salt from Aldrich) 28 mg Bentonite 100 mg The synthetic water has a pH of 8.36, its turbidity is 10.5 NTU and its organic matter content corresponds to 8.6 mg 02/l.

This synthetic water is treated with the gels of Samples E and H and with a basic aluminium chlorosulphate (SAMPLE I) containing (% by weight): Al3+ 10 (expressed as A12O3) Cl 9. 32 so42- 2. 25 Ca2+ 0.21 Basicity 47% Jar-test flocculation experiments are carried out using the following operating method: - one-litre beaker, - 13 - temperature 15°C - synthetic water - HYDROCURE-type SLH6 jar-test - rapid agitation for 1 min 30 sec after addition of the 5 flocculating agent followed by slow agitation for 13 min 30 sec, that is to say sufficient for there to be coalescence but preventing settling of the floes.

The mixture is then allowed to settle for 30 min and the supernatant is then filtered off.

The turbidity in NTU is determined for various proportions of flocculating agent introduced.

The results are collated in Table VII.

TABLE I SAMPLE NUMBERS A (%) A, B and C D Cp 0.05 40 ± 10 70 ± 8 (g/i) 0.1 60 ± 10 90 ± 10 0.3 85 ± 10 95 ± 5 0.4 90 ± 10 95 ± 5 TABLE II SAMPLE NO. o.f.c (mg/g) A 250 C 700 D 1 800 TABLE III Type of grinding o.f.c (mg/g) No grinding 700 Grinding at low speed 250 Grinding at high speed 190 TABLE IV A (%) SAMPLE Nos. A B D Cp 0.1 17 ± 5 20 ± 5 35 + 5 (g/1) 0.5 30 ± 10 35 ± 10 60 ± 10 1 40 ± 10 40 ± 10 80 ± 10 - 15 TABLE V A (%) SAMPLE Nos. E and F G H Cp 0.025 15 ± 5 60 ± 5 (g/1) 0.05 25 ± 5 70 ± 10 87 ± 10 0.065 27 ± 5 73 ± 10 91 ± 10 0.1 40 ± 5 78 ± 10 93 ± 10 0.12 40 ± 5 80 ± 10 94 ± 10 0.15 90 ± 10 TABLE VI SAMPLE No. o.f.c (mg/g) A (%) E 8 20 ± 5 F 12 30 ± 5 G 16 80 ± 10 20 H 18 94 ± 10 - 16 TABLE VII Turbidity of the supernatant (NTU) Amount of flocculant * (g/m3) 0.5 1 2 3 4 5 SAMPLE NO./ E 3.1 2 1.8 1.7 1.65 1.8 10 H I 4.9 3.2 1.6 2 * For basic aluminium chlorosulphate it is expressed as g of Al2O3/m3.

The adsorption results indicated in Tables I, IV and V are averages calculated from ten measurements.

Claims (9)

1. A product represented by the formula: -MCH 2 -CH)~^ in which x = y + z 5 0 < y < 1 0 < z < 0.1 1 < n < 5 each of R lf R 2 and R 3 , which may be identical or different, is a hydrogen atom or an alkyl group having from 1 to 10 10 carbon atoms, and R is a divalent bridging group, of the formula: CH 2 -CH) CH i^T (CH 2— ei < C H 2 >n ci© R3 Ri Rl (II) I - 18 in which 0.3 < x < 1 and n, Rj, R 2 and R 3 are as defined above.

2. A product according to claim 1 in which n < 2.

3. A product according to claim 1 or 2 in which at 5 least one of Rj, R 2 and R 3 is methyl, ethyl or hydrogen.

4. A product according to claim 1 substantially as described in Example 1 or 3.

5. Method for water treatment, which comprises incorporating in it at least one product as claimed in any 10 one of claims 1 to 4.

6. Method according to Claim 5 for the treatment of water containing pyrene and/or 1-hydroxyanthraquinone.

7. Method according to Claim 5 or 6 for the treatment of water containing silica and/or bentonite. 15

8. Method according to claim 5 substantially as described in any one of Examples 1 to 3.

9. Water whenever treated by a method as claimed in any one of claims 5 to 8.