CA1049163A - Process for the purification of contaminated water - Google Patents
Process for the purification of contaminated waterInfo
- Publication number
- CA1049163A CA1049163A CA75222326A CA222326A CA1049163A CA 1049163 A CA1049163 A CA 1049163A CA 75222326 A CA75222326 A CA 75222326A CA 222326 A CA222326 A CA 222326A CA 1049163 A CA1049163 A CA 1049163A
- Authority
- CA
- Canada
- Prior art keywords
- effluent
- ions
- ferric
- dye
- heavy metal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Water Treatment By Electricity Or Magnetism (AREA)
- Separation Of Suspended Particles By Flocculating Agents (AREA)
- Removal Of Specific Substances (AREA)
Abstract
A PROCESS FOR THE PURIFICATION OF CONTAMINATED WATER
ABSTRACT OF THE DISCLOSURE
The invention concerns the purification of an aqueous liquid, especially effluent from a dyeing process, which is contaminated with coloured substances. The aqueous liquid is treated in the substantial absence of fibres and dye complexing retarders with ferric or ferrous ions, ferric hydroxide is formed therefrom and the ferric hydroxide together with the coloured substances is removed from the aqueous liquid. Dye complexing retarders present can be removed by an ion-exchange pre-treatment. The ferric or ferrous ions may be provided by electrolysis of iron or scrap iron, ferric hydroxide, or ferrous or ferric salts.
ABSTRACT OF THE DISCLOSURE
The invention concerns the purification of an aqueous liquid, especially effluent from a dyeing process, which is contaminated with coloured substances. The aqueous liquid is treated in the substantial absence of fibres and dye complexing retarders with ferric or ferrous ions, ferric hydroxide is formed therefrom and the ferric hydroxide together with the coloured substances is removed from the aqueous liquid. Dye complexing retarders present can be removed by an ion-exchange pre-treatment. The ferric or ferrous ions may be provided by electrolysis of iron or scrap iron, ferric hydroxide, or ferrous or ferric salts.
Description
1~:)49163 This invention relates to the purification of water contaminated with at least coloured substances, and possibly contaminated with other substances, such as acids, salts, and residues from an industrial dyeing process.
The contaminated water is hereafter referred to as an aqueous liquid.
The present invention provides a process for the purification of effluent dyestuff-containing liquid without substantially building up the total dissolved solids content thereof, said effluent liquid being effluent from a dyeing process and which is contaminated with at least one dye and heavy metal ions but which is substantially free from dye complexing retarders, said process comprising the steps of (a) introducing iron ions into the effluent by electrolysis from an iron electrode, (b) oxidizin~ ferrous ions in the effluent to -ferric ions which precipitate as ferric hydroxide and to which the dyes and heavy metal ions adhere, and (c) removing the ferric hydroxide together with the adhering dyes and heavy metal ions.
The coloured substances may be dyes or pigments.
If the water to be treated is effluent from a textile factory it may contain fibres and these can be separated in an initial step by screening or filtration. If dye complexing retarders from an industrial dyeing process are present, they are at least partially removed before the treatment with iron. The removal o~ dye complexing retarders can be carried out by ion~exchange. The ion-exchange resin to be used will depend on the retarder charge. For example an anionic dye complex-ing retarder, such as a sulphonate castor oil can be removedwith a weakly basic anion exchange resin, whereas a cationic - \
--- 1049: IL63 dye complexing retarder can be removed with a weakly acidic cationic exchange resin. The ion exchange treatment can be by upflow treatment, with the area of exchange resin increas-ing in the direction of upflow. The upper diameter of the resin column is such that the upward liquid velocity does not exceed the stokes velocity resin, resulting in the resin beads falling back into the exchange resin bed. Such a partial fluidisation of the bed allows free passage of suspended material through the bed without excessive pressure increase or decrease in effluent flow rate.
,, ., . -20 ~ ~ ~
;, :, ; ' ,~.. ..
., : ' , . ' , ,: ,. :
,' .' . ., ',, '., ' ., , '.
~4~163 The iron ions conveniently are added by elec-trolysis of iron or scrap iron when effluent is to be re-cycled, or by the addition of sulphates, chlorides or nitrates when a build-up of total dissolved solids can be tolerated.
The iron is present as ferrous or ferric ions, depending on the oxidation characteristics of the effluent being treated. If oxidising agents are present in the effluent, any ferrous ions may be oxidised immediately to ferric ions. If the action of oxygen in the air is insuffic-ient, an oxidising agent can be added to ensure the formation of ferric hydroxide.
The pH can be adjusted to give an optimum precipi-tation of ferric hydroxide floc, the actual pH depending preferably on the zeta potential of the colouring material.
For example, if the residual dye or other colouring matter is anionic, a positive zeta potential on the ferric hydroxide flocculate would be desirable, and vice versa. Thus, the pH may be less than 6.6 for treating an aqueous liquid con-taining an anionic residual dye. Similarly the pH can beadjusted to the optimum value for adsorbing colouring materials which have a zero zeta potential, or which form complexes with ferrous or ferric ions, or their hydroxides.
The ferric hydroxide flocculate containing the dye, pigment or the like adsorbed, absorbed or complexed there-with may be separated by thickening, clarification, flota-tion, centrifuging, filtration, or the like, or a combination of two or more such steps. As the solubility of ferrous hydroxide is in the region of 5 to 15 mg/litre, it is desir-` 30 able to oxidise all the iron to the ferric state, thereby ., .
' .
. ' .
- , - . . .. - . . . ., , . .. .. . . :
.,, . :, ., . , ~ : . :
~, ~ . ... : " . . ' ~04~1~3 reducing the solubility to less than 1 mg/litre and ensuring precipitation of all iron as ferric hydroxide. -The treated effluent may then be passed through a colour detection apparatus or system, e.g. a spectrophoto-meter, photometer, turbudity meter, or the like, or examined by eye. The treated effluent may then be recycled to be treated again with iron, or accepted for further use.
The pH of the effluent may be adjusted for further use, e.g. to a pH suitable for use in a dyehouse. The ion exchanye resin used to remove retarders may be regenerated in known manner to yield dye complexing regarder which can be recycled to the dyehouse. Buffer solutions (e.g. based on acetic acid, sodium acetate and sodium hydroxide) may be used for pH adjustment. The ferric hydroxide may be used as landfill, or may be incinerated and the iron oxides re-used in the electrolysis step.
The invention is illustrated by reference to the following non-limiting Example, read with the accompanying flowsheet.
. .
Example : The effluent was from a dyehouse and contained:
Acetlc Acid Sodium acetate Dye complexing retarder - Sulphonated caster oil Antifoamer Cadionic dye (DYE) Suspended matter such as fibres and synthetic starches.
The fibres present were first removed by screen-ing and then the dye complexing retarder was removed by ''. . '' . ' ", ... . , . . ,. " .: ,, ., ,:
.
~4~ 3 upflow ion exchange using a weakly basic anion exchanger (Amberlite IRA 93).
The reactions which occurred were as follows:
Protonation of resin in acid solution.
RlNH2 + (H) ~ RlNH3 Dissociation of sulphonated castor oil
The contaminated water is hereafter referred to as an aqueous liquid.
The present invention provides a process for the purification of effluent dyestuff-containing liquid without substantially building up the total dissolved solids content thereof, said effluent liquid being effluent from a dyeing process and which is contaminated with at least one dye and heavy metal ions but which is substantially free from dye complexing retarders, said process comprising the steps of (a) introducing iron ions into the effluent by electrolysis from an iron electrode, (b) oxidizin~ ferrous ions in the effluent to -ferric ions which precipitate as ferric hydroxide and to which the dyes and heavy metal ions adhere, and (c) removing the ferric hydroxide together with the adhering dyes and heavy metal ions.
The coloured substances may be dyes or pigments.
If the water to be treated is effluent from a textile factory it may contain fibres and these can be separated in an initial step by screening or filtration. If dye complexing retarders from an industrial dyeing process are present, they are at least partially removed before the treatment with iron. The removal o~ dye complexing retarders can be carried out by ion~exchange. The ion-exchange resin to be used will depend on the retarder charge. For example an anionic dye complex-ing retarder, such as a sulphonate castor oil can be removedwith a weakly basic anion exchange resin, whereas a cationic - \
--- 1049: IL63 dye complexing retarder can be removed with a weakly acidic cationic exchange resin. The ion exchange treatment can be by upflow treatment, with the area of exchange resin increas-ing in the direction of upflow. The upper diameter of the resin column is such that the upward liquid velocity does not exceed the stokes velocity resin, resulting in the resin beads falling back into the exchange resin bed. Such a partial fluidisation of the bed allows free passage of suspended material through the bed without excessive pressure increase or decrease in effluent flow rate.
,, ., . -20 ~ ~ ~
;, :, ; ' ,~.. ..
., : ' , . ' , ,: ,. :
,' .' . ., ',, '., ' ., , '.
~4~163 The iron ions conveniently are added by elec-trolysis of iron or scrap iron when effluent is to be re-cycled, or by the addition of sulphates, chlorides or nitrates when a build-up of total dissolved solids can be tolerated.
The iron is present as ferrous or ferric ions, depending on the oxidation characteristics of the effluent being treated. If oxidising agents are present in the effluent, any ferrous ions may be oxidised immediately to ferric ions. If the action of oxygen in the air is insuffic-ient, an oxidising agent can be added to ensure the formation of ferric hydroxide.
The pH can be adjusted to give an optimum precipi-tation of ferric hydroxide floc, the actual pH depending preferably on the zeta potential of the colouring material.
For example, if the residual dye or other colouring matter is anionic, a positive zeta potential on the ferric hydroxide flocculate would be desirable, and vice versa. Thus, the pH may be less than 6.6 for treating an aqueous liquid con-taining an anionic residual dye. Similarly the pH can beadjusted to the optimum value for adsorbing colouring materials which have a zero zeta potential, or which form complexes with ferrous or ferric ions, or their hydroxides.
The ferric hydroxide flocculate containing the dye, pigment or the like adsorbed, absorbed or complexed there-with may be separated by thickening, clarification, flota-tion, centrifuging, filtration, or the like, or a combination of two or more such steps. As the solubility of ferrous hydroxide is in the region of 5 to 15 mg/litre, it is desir-` 30 able to oxidise all the iron to the ferric state, thereby ., .
' .
. ' .
- , - . . .. - . . . ., , . .. .. . . :
.,, . :, ., . , ~ : . :
~, ~ . ... : " . . ' ~04~1~3 reducing the solubility to less than 1 mg/litre and ensuring precipitation of all iron as ferric hydroxide. -The treated effluent may then be passed through a colour detection apparatus or system, e.g. a spectrophoto-meter, photometer, turbudity meter, or the like, or examined by eye. The treated effluent may then be recycled to be treated again with iron, or accepted for further use.
The pH of the effluent may be adjusted for further use, e.g. to a pH suitable for use in a dyehouse. The ion exchanye resin used to remove retarders may be regenerated in known manner to yield dye complexing regarder which can be recycled to the dyehouse. Buffer solutions (e.g. based on acetic acid, sodium acetate and sodium hydroxide) may be used for pH adjustment. The ferric hydroxide may be used as landfill, or may be incinerated and the iron oxides re-used in the electrolysis step.
The invention is illustrated by reference to the following non-limiting Example, read with the accompanying flowsheet.
. .
Example : The effluent was from a dyehouse and contained:
Acetlc Acid Sodium acetate Dye complexing retarder - Sulphonated caster oil Antifoamer Cadionic dye (DYE) Suspended matter such as fibres and synthetic starches.
The fibres present were first removed by screen-ing and then the dye complexing retarder was removed by ''. . '' . ' ", ... . , . . ,. " .: ,, ., ,:
.
~4~ 3 upflow ion exchange using a weakly basic anion exchanger (Amberlite IRA 93).
The reactions which occurred were as follows:
Protonation of resin in acid solution.
RlNH2 + (H) ~ RlNH3 Dissociation of sulphonated castor oil
2 SO3Na~__ ~R2 SO3 + Na+
Ion exchange reaction (Extraction of sulphonate).
RlNH3 + R2SO3 - -~ RlNH3 3 2 As a weak basic anion exchanger was used, only the strong acids, such as sulphonates and sulphates were removed from the effluent. The anion exchanger was treated from time to time to recover the dye complexing retarder and to regenerate the anion exchange resin. Carboxylic anions -such as CH3COO were not removed on passing the effluent through the resin but would be removed if a strongly basic anion exchanger were used, resulting in more frequent resin regenerations. `~
After adding scrap iron, electrolysis of the effluent from the resin was then effected using a Standard D.C. power supply and applying Farraday's Laws of Electrolysis to determine the amount of iron ions liberated in the effluent.
Ferric hydroxide formation was carried out by the addition of hydrogen peroxide and using oxygen from air introduced by airation of effluent. The optimum precipitation pH for removal of cationic dye was pH = 8. The sodium acetate and acetic acid acted as a buffer.
Anionic dyes with a negative charge, by comparison, have an optimum precipitation pH between 5 and 6. The Z.E.T.A. ~ ~
,.
'~ - .
, .
. , .
:, . ", . " . ,.",.~ -' '' " ' ' '. ' '' ' "' ' " ". ~, ' . ' ' ' ~ ~
, , - . . . .
"' ' ', ' -. ' '.: ', ' ' ' ' .
: -potential of ferric hydroxide is positive and increasingfor pH values less than 6 and negatively increasing for pH values greater than 7.
Sludge thickening was achieved using a clarifier, and ferric hydroxide fines were removed from the overflow by candle filters and rotary vacuum filters using diatom-aceous earth.
Colour detection was carried out using Beckman ~
spectrophotometer. Once the colour was acceptable, the pH ~ -was adjusted to 4,7 with acetic acid, and the treated liquid was supplied to the dye house and re-used (after adding about 20% of water since some water had been lost on fibre removal and in thickened sludge drying beds). Rejected effluent was re-supplied to the electrolysis step. By recycling the treated liquid, loss of useful soluble substances and out-side contamination were avoided.
, 30 _7_ ; . , : ... .
~' . , . : , : . , .
.
Ion exchange reaction (Extraction of sulphonate).
RlNH3 + R2SO3 - -~ RlNH3 3 2 As a weak basic anion exchanger was used, only the strong acids, such as sulphonates and sulphates were removed from the effluent. The anion exchanger was treated from time to time to recover the dye complexing retarder and to regenerate the anion exchange resin. Carboxylic anions -such as CH3COO were not removed on passing the effluent through the resin but would be removed if a strongly basic anion exchanger were used, resulting in more frequent resin regenerations. `~
After adding scrap iron, electrolysis of the effluent from the resin was then effected using a Standard D.C. power supply and applying Farraday's Laws of Electrolysis to determine the amount of iron ions liberated in the effluent.
Ferric hydroxide formation was carried out by the addition of hydrogen peroxide and using oxygen from air introduced by airation of effluent. The optimum precipitation pH for removal of cationic dye was pH = 8. The sodium acetate and acetic acid acted as a buffer.
Anionic dyes with a negative charge, by comparison, have an optimum precipitation pH between 5 and 6. The Z.E.T.A. ~ ~
,.
'~ - .
, .
. , .
:, . ", . " . ,.",.~ -' '' " ' ' '. ' '' ' "' ' " ". ~, ' . ' ' ' ~ ~
, , - . . . .
"' ' ', ' -. ' '.: ', ' ' ' ' .
: -potential of ferric hydroxide is positive and increasingfor pH values less than 6 and negatively increasing for pH values greater than 7.
Sludge thickening was achieved using a clarifier, and ferric hydroxide fines were removed from the overflow by candle filters and rotary vacuum filters using diatom-aceous earth.
Colour detection was carried out using Beckman ~
spectrophotometer. Once the colour was acceptable, the pH ~ -was adjusted to 4,7 with acetic acid, and the treated liquid was supplied to the dye house and re-used (after adding about 20% of water since some water had been lost on fibre removal and in thickened sludge drying beds). Rejected effluent was re-supplied to the electrolysis step. By recycling the treated liquid, loss of useful soluble substances and out-side contamination were avoided.
, 30 _7_ ; . , : ... .
~' . , . : , : . , .
.
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for the purification of effluent dyestuff-containing liquid without substantially building up the total dissolved solids content thereof, said effluent liquid being effluent from a dyeing process and which is contaminated with at least one dye and heavy metal ions but which is substantially free from dye complexing retarders, said process comprising the steps of (a) introducing iron ions into the effluent by electrolysis from an iron electrode, (b) oxidizing ferrous ions in the effluent to ferric ions which precipitate as ferric hydroxide and to which the dyes and heavy metal ions adhere, and (c) removing the ferric hydroxide together with the adhering dyes and heavy metal ions.
2. A process for the purification of effluent dyestuff-containing liquid without substantially building up the total dissolved solids content thereof, said effluent liquid being effluent from a dyeing process which is contaminated with at least one dye and heavy metal ions, said effluent also containing dye complexing retarders, which process comprises the steps of (a) at least partially removing the dye complexing retarders by ion exchange, (b) introducing iron ions into the effluent by electrolysis from an iron electrode, (c) oxidizing ferrous ions in the effluent to ferric ions which precipitate as ferric hydroxide and to which the dyes and heavy metal ions adhere, and (d) removing the ferric hydroxide together with the adhering dyes and heavy metal ions.
3. A process according to claim 2, wherein the ion-exchange is carried out by upflow treatment with the area of ion-exchange resin increasing in the direction of upflow.
4. A process according to claim 3 wherein the ion-exchange resin is treated to regenerate the dye complexing retarder which is circulated back to the dyeing process.
5. A process according to claim 1 where an oxidizing agent is added to the liquid to oxidize the ferrous ions to ferric ions.
6. A process according to claim 2 wherein an oxidizing agent is added to the liquid to oxidize the ferrous ions to ferric ions.
7. A process according to claim 1 wherein the pH of the treated effluent is adjusted to a more acidic value and recycled to the dyeing process.
8. A process according to claim 2 wherein the pH of the treated effluent is adjusted to a more acidic value and recycled to the dyeing process.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA75222326A CA1049163A (en) | 1975-03-14 | 1975-03-14 | Process for the purification of contaminated water |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA75222326A CA1049163A (en) | 1975-03-14 | 1975-03-14 | Process for the purification of contaminated water |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1049163A true CA1049163A (en) | 1979-02-20 |
Family
ID=4102559
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA75222326A Expired CA1049163A (en) | 1975-03-14 | 1975-03-14 | Process for the purification of contaminated water |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1049163A (en) |
-
1975
- 1975-03-14 CA CA75222326A patent/CA1049163A/en not_active Expired
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