WO1999021801A1

WO1999021801A1 - Method for water purification based on the fenton reaction

Info

Publication number: WO1999021801A1
Application number: PCT/SK1998/000016
Authority: WO
Inventors: Josef Prousek; Ladislav Maro
Original assignee: Prox T.E.C. Poprad, S.R.O.
Priority date: 1997-10-29
Filing date: 1998-10-26
Publication date: 1999-05-06
Also published as: SK280649B6; CZ138398A3; AU9660298A; WO1999021801B1; SK146597A3; CZ290006B6

Abstract

The invention relates to a method for water purification based on the Fenton reaction the nature of which consists in that to the water adjusted to pH = 2.0 to 4.0 FeSO4.7H2O in an amount of 0.05 % to 0.40 % by weight, and H2O2 in an amount of 0.03 % to 0.45 % by weight are added, the composition is further mixed for 60 to 90 minutes at a temperature of 10 to 30 °C, and it is left to react for additional 10 to 35 minutes to finish the reaction, then it is neutralized to pH = 7.0 to 8.0, and further a flocculant, based on polyacrylamide copolymers, and/or a coagulant in an amount of 0.01 to 1.5 % by weight is added under intensive stirring, and the mixture is allowed to sedimentate for 0.5 to 3 hours, after which the cleaned water is separated from the sediment.

Description

Method for water purification based on the Fenton reaction

Technical Field

The invention relates to a method for water purification based on the Fenton reaction.

Background Art

Vater purification using the Fenton reaction, i.e. treating water with H O2 and FeSθ4.7H2θ, described in the papers of J.H. Carey, Vater Poll. Res. J. Canada _.27_., 1, 1992; S.H. Lin and C.F. Peng, Environ. Technol . 16_., 693, 1995; and in a onothematic number, edited by A. Vogelpohl and S.U. Geissen, Oxidation Technologies for Vater and Vastewater Treatment, Vater Sci . Technol. 3_5_. (4), 1 - 306, 1997; represents an important step in the field of technology of wastewater cleaning. These technologies are generally called Advanced Oxidation Technologies (AOTs) .

One of the first works in this field is that of V.G. Ku??, Vater Res. 26_., 881, 1992, who carried the Fenton reaction out at a temperature of 50 °C, and after its accomplishment he worked only with the upper layer of clear liquid instead of the whole bulk, by which procedure he achieved relatively high values of removed colour and COD. Therefore, the results obtained do not reflect reality, because the author didn't work with the whole bulk of water to be cleaned. A disadvantage of the method used is also the fact that the originating precipitate was sedimenting for at least 4 hours.

A disadvantage of all works published so far consists in the fact that in most cases the efficiency of COD removing is only 60 to 80 %. The lower COD values are caused by using an inappropriate ratio of Hy^-_j and the Fe salt. These procedures often lead to formation of a fine disperse system and thereby to prolongation of the sedimentation time up to 24 hours. There is also a disadvantage that worse technological parameters are achieved, like sedimentation rate, flocculus shape and filterability . A further disadvantage is the necessity of high investment costs for the appropriate equipment.

A serious disadvantage of the above works is the fact that using of AOTs leads to a high extent of degradation of pure substance, for example of phenol, 4-chlorophenol and the like, in model waters, and they practically haven't dealt with real wastewaters.

Disclosure of Invention

The above given disadvantages are eliminated by the method according to this invention, the nature of which consists in that to the water adjusted to pH = 2.0 to 4.0 FeS0₄.7H₂0 in an amount of 0.05 % to 0.40 % by weight, and ^2^2 ^^{n an amount} of 0.03 % to 0.45 % by weight, are added, the composition is further mixed for 60 to 90 minutes at a temperature of 10 to 30 °C, and it is left to react for additional 10 to 35 minutes to finish the reaction, then it is neutralized to pH =7.0 to 8.0, and further a flocculant, based on polyacrylamide copolymers , and/or a coagulant in an amount of 0.01 to 1.5 % by weight is added under intensive stirring , then the mixture is left to sedimentate for 0.5 to 3 hours, after which the cleaned water is separated from the sediment .

As a flocculant a cation active, anion active or a neutral flocculant may be used.

A mixture of water, FeSO^ .7H2O in an amount of 0.05 % to 0.40 % by weight, and H₂θ2 in an amount of 0.03 % to 0.45 % by weight may be mixed for 60 to 90 minutes at a temperature of 10 to 30 °C in the presence of the day light, solar radiation or artificial UV-VIS radiation.

A mixture of water, FeSO^ .7H2O in an amount of 0.05 % to 0.40 % by weight, and H2O2 in an amount of 0.03 % to 0.45 % by weight may be mixed for 60 to 90 minutes at a temperature of 10 to 30 °C in the dark. As a coagulant polyaluminium chloride, polyaluminium sulfate, aluminium sulfate, ferric chloride or aluminium chloride may be used.

If a flocculant or its combination with a coagulant is used, the sedimentation time is considerably shortened to 0.5 to 3 hours, and the value of removed COD is substantially better. Also the quality of flocculi of the resulting slurry is considerably better, the flocculi have a defined 'shape, thus improving also the possibilities of better filtration of the slurry.

Vhen determining COD and adjusting pH the whole bulk of the real wastewater to be cleaned is used which, of course , results in the determination of the true parameters of the cleaned water .

Because of its simplicity the method according to this invention can be used as one purification step in equipments which are parts of a wastewater purification plant, as the purification method doesn't require any special equipment for accomplishing this operation. Thus the method according to this invention eliminates complexity of equipments used so far, it improves technological parameters of the arising slurry, decreases time demands, it substantially increases efficiency of the removed chemical oxygen demand (COD) , and recently it belongs to the economically most efficient procedures used among the AOTs technologies. The simple purification method may be used in a stationary, semicontinuous and a continuous arrangement as a prepurification operation, one of the purification steps or final cleaning steps for the purification of polluted water before draining it off to a recipient.

Examples of embodiments

Example 1

A 500 ml Erlenmayer flask was charged with 300 ml of wastewater from perfume production with the original value of COD = 1855 mg.l^"1, and 5 % H₂S0₄ was used to adjust the pH value to 3.0. Then 1.09372 g of FeS0₄.7H₂0 and 1.6 ml of 30 % H2O2 were added under stirring. The composition was stirred for 90 minutes at a temperature of 22 °C on an electromagnetic mixer (200 r.min ) and then it was left to stand for 30 minutes . After 30 minutes it was neutralized by a solution of sodium carbonate to pH =7.0, then one drop of 0.1 % aqueous solution of the cationic flocculant Zetag 57 was added.' After 30 minutes of sedimentation the value of COD was determined in the clear liquid. The resulting value of COD = 240 mg.l^"1, the efficiency of removed COD was 87 %.

Example 2

A 500 ml Erlenmayer flask was charged with 300 ml of wastewater from perfume production with the original value of COD = 3111 mg.l^" , and 5 % H₂S0₄ was used to adjust its pH value to 3.0. Then 0.82029 g of FeS0₄.7H₂0 and 2.4 ml of 30 % H2O2 were added under stirring. The composition was stirred for 90 minutes at a temperature of 22 °C on an electromagnetic stirrer (200 r.min^" ) and then it was left to stand for 30 minutes . After 30 minutes it was neutralized by a solution of sodium carbonate to pH = 7.0. After 30 minutes of sedimentation the efficiency of removed COD was 81 %.

Example 3

The procedure and the kind of water to be purified were the same as in Example 2 except that after addition of the Fenton reagent and neutralization 1 drop of 0.1% aqueous solution of the cationic flocculant Zetag 57 was added. Resulting value of COD = 480 mg.l . Efficiency of removed COD was 87 %, i.e. 6 % higher compared to example 2 without using the flocculant . Examp le 4

Vastewater from the production of synthetic fibres with the original value of COD = 1556 mg.l^" .The procedure was the same as in Example 1 except that 0.27343 g of FeS0₄.7H₂0 and 0.8 ml of 30 % H₂0₂ were added. Resulting value of COD = 658 mg.l^" , efficiency of removed COD was 58 %.

Example 5

To 300 ml of a humine macerate?? water sample, polluted with petroleum substances (4.43 mg.l^" ), with the original value of COD = 1828 mg.l^"1 and with pH 2.980 1.09372 g of FeS0₄.7H2O and 1.6 ml of 30 % H2O2 were added under stirring at a temperature of 23 °C. The composition was stirred for 1 hour and then it was left to stand for 30 minutes. Then it was neutralized, whereby voluminous precipitate resulted to which 1 drop of 0.1 % solution of the flocculant Zetag 57 and 1 drop of the coagulant polyaluminium chloride (PAC-10 Novaflok) were added under stirring. After 1 hour of standing the resulting value of COD=508 mg.l^"1 (72 %) and after 3 hours of standing 376 mg.l^"J (79 %) .

Example 6

The water sample and procedure were the same as in example 4 except that pH = 2.96 and 0.54686 g of FeS0₄.7H₂0 and 1.6 ml of 30 % H 2 ^were added, and the reaction was exposed to intensive solar radiation for 90 minutes at a temperature of 32 °C. Then it was left to stand for 30 minutes and after neutralization to pH = 7.0 in the whole bulk voluminous precipitate arised to which 1 drop of the flocculant Zetag 57 was added. After 1 hour of sedimentation the resulting value of COD = 543 g.l^" (70 %) for the clear liquid . Example 7

The procedure was the same as in example 5 except that 1000 ml of wastewater with adjusted pH = 2.994 were used to which 1.82287 g of FeS0₄.7H₂0 and 5.33 ml of 30 % H₂0₂ were added. After 1 hour of standing the resulting value of COD = 729 mg.l^"1 (60 %) and after 21 hours of standing 484 mg.l^" (74 %) . The content of petroleum substances decreased • from 4.43 mg.l^" to 2.84 mg.l^" (36 %) .

Example 8

To 300 ml of wastewater from the production of chemical fibres with the original value of COD = 1112 mg.l^" and adjusted pH = 3.0 0.54686 g of FeS0₄.7H₂0 and 1.6 ml of 30 % H2O2 were added. The composition was stirred for 1 hour at a temperature of 24 °C, then it was left to stand for 30 minutes. After 30 minutes it was neutralized to pH = 7.0, 1 drop of 0.1 % solution of the flocculant Zetag 57 was added and it was left to sedimentate for 1 hour. The resulting value of COD = 17 mg.l^" (98.5 %) . The ammonia content decreased from 344.2 mg.l^" to 240.5 mg.l^" (30 %) .

Example 9

To 300 ml of model coloured wastewater, containing 100 mg.l^" of the dye Isolan Orange S-RL, with pH = 3.0 the Fenton reagent/0.54686 g of FeS0₄.7H₂0 and 0.8 ml of 30 % H2O2 were added. Further procedure was the same as in example 1 except that after neutralization 1 drop of 0.1 % aqueous solution of the cationic flocculant Superflock C 496 was added. After 1 hour of standing the efficiency of dye removing was 99.5 % and COD = 86 %.

Example 10

To 300 ml of model coloured wastewater, containing 100 100 mg.l of the dye Isolan Marineblau S-RL,with pH =3.0 the Fenton reagent/0.54686 g of FeS0₄.7H₂0 and 0.8 ml of 30 % ^2^2 ^were added. The procedure was the same as in example 1 except that after neutralization 1 drop of 0.1 % aqueous solution of the anionic flocculant Superflock A 130 was added . After 1 hour of standing the efficiency of dye removing was 95.7 % and COD = 80 % .

Example 11'

To 300 ml of model coloured wastewater, containing 100 mg.l of the dye Isolan Gelb S-GL, with pH = 3.0 the Fenton reagent/0.27343 g of FeS0₄.7H₂0 and 0.8 ml of 30 % H₂0₂ were added. The procedure was the same as in example 1 except that the solution of the dye and the Fenton reagent was exposed to solar radiation for 1.5 hours at a temperature of 10 °C, and after neutralization 1 drop of 0.1 % aqueous solution of the cationic flocculant Zetag 57 was added. After 1 hour of standing the efficiency of dye removing was 99.0 % and COD = 91 %.

Industrial Applicability

The method according to this invention may be used in purification of not only industrial wastewaters , but also of supply waters. It is possible to use this method of purification within a wastewater purification plant as one of its purification steps, for pretreat ent of wastewater before the purification plant or as the final step of water purification behind the purification plant before draining the water off into a recipient.

Claims

C L A I M S

1. A method of water purification based on the Fenton reaction, characterized in that to the water, adjusted to pH = 2.0 to 4.0 FeS0₄.7H₂0 in an amount of 0.05 % to 0.40 % by weight, and

^{an amoun} ┬░f 0.03 % to 0.45 % by weight, are added, the composition is further stirred for 60 to 90 minutes at a temperature of 10 to 30 ┬░C, and it is left to react for' additional 10 to 35 minutes to finish the reaction, then it is neutralized to pH = 7.0 to 8.0, and further a flocculant, based on polyacrylamide copolymers, and/or a coagulant in an amount of 0.01 to 1.5 % by weight is added under intensive stirring, the mixture is allowed to sedimentate for 0.5 to 3 hours, after which the cleaned water is separated from the sediment.

2. A method according to claim 1, characterized in that as the flocculant, based on polyacryl copolymers, a cationic, anionic or neutral flocculant is used.

3. A method according to claims 1 and 2, characterized in that as the coagulant polyaluminium chloride, polyaluminium sulfate, aluminium sulfate, ferric chloride or aluminium chloride is used.

4. A method according to claims 1 to 3 , characterized in that a mixture of water, FeS0₄.7H2O in an amount of 0.05 % to 0.40 % -by weight, and H₂0₂ in an amount of 0.03 % to 0.45 % by weight is stirred for 60 to 90 minutes at a temperature of 10 to 30 ^CC in the presence of the day light, solar radiation or artificial UV-VIS radiation.

5. A method according to claims 1 to 3 , characterized in that a mixture of water, FeS0₄.7H_?0 in an amount of 0.05 % to 0.40 % by weight, and H₂0₂ in an amount of 0.03 % to 0.45 % by weight is stirred for 60 to 90 minutes at a temperature of 10 to 30 ┬░C in the dark.

6. A method according to claims 1 to 5 , characterized in that it is carried out in stationary, semicontinuous and continuous equipments.