Title of Invention	"AN IMPROVED PROCESS FOR DE DYEING OF LIQUID WASTE."
Abstract	The present invention provides an improved process for de dyeing of liquid waste. The water soluble dye is removed by adopting reverse micelle technique. The waste water containing organic ionic dye in solution form is contacted with the oppositely charged surfactant in water immiscible solvent under stirring followed by separating colorless water phase and solvent phase containing dye encapsulated reverse micelle by gravity. Further the encapsulated dye also can be recovered using counter-ionic surfactant, if so desired, for reuse.

Title of Invention

"AN IMPROVED PROCESS FOR DE DYEING OF LIQUID WASTE."

Abstract

The present invention provides an improved process for de dyeing of liquid waste. The water soluble dye is removed by adopting reverse micelle technique. The waste water containing organic ionic dye in solution form is contacted with the oppositely charged surfactant in water immiscible solvent under stirring followed by separating colorless water phase and solvent phase containing dye encapsulated reverse micelle by gravity. Further the encapsulated dye also can be recovered using counter-ionic surfactant, if so desired, for reuse.

Full Text	The present invention relates to an improved process for de dyeing of liquid waste. The invention particularly relates to removal of dyes from liquid waste by liquid liquid extraction. More particularly, the invention relates to removal of organic ionic dyes by liquid liquid extraction using reverse micelle. Dyes are, generally, cyclic organic compounds with relatively high molecular weights, ionic in nature and soluble in water. Almost every industry, but mainly textile industry uses dyes to color its products. Effluents from industries such as carpet manufacturing, dyeing, textile, pulp & paper, leather, and distillery contain various types of dyes that should be removed before discharging the effluent to the environment in the interest of public order and impairment of ecosystem. Though some dyes are inert and nontoxic in nature particularly at the level of concentration discharged into the receiving water, the colour they impart is very undesirable due to adverse aesthetic effect, some dyes at a concentration of COAGULATION& SEDIMENTATION: _1. Japanese Patent No. JP 551786 published on 04-12-1980, teaches de-dyeing of dyeing waste water to colorless and transparent water using Al (OH) 3 and Al2O3 as coagulating agent. 2. Canadian Patent No. CN 1121488 published on 01-05-1996 advocates use of ferric salts as coagulant for removal of color from dyeing waste water. 3. Japanese Patent No.JP 2000095802 published on 04-04-2000 describes use of new polysaccharide produced by a specific gram-negative bacterium as a coagulant. These methods result in generation of large quantity of sludge and thus appear to be uneconomical as they require additional infrastructure for disposal of sludge. ADSORPTION METHOD: 1. PCT Patent application No. WO 02/42228 published on 30-05-2002 relates to using bioadsorbent material for removal of color. The bioadsorbent material is a specific bacterium immobilized on charcoal. However, it is applicable to removal of color from textile effluents containing azo dye. 2. Poots et al proposed in 1976, peat, wood as an adsorbent for the removal dye. Silica, charcoal, hard wood sawdust, bentonite clay, rice husk, fly ash are couple of other adsorbents, which find potentially useful for color removal. However, these adsorbents pose the problem of regeneration. Additionally some of them are quite expensive. OXIDATION METHOD: Among oxidation methods, UV/ozone or UV/H2O2 is found to be better technology for removal of dye from wastewater. A refernce can be made to Ruppet et al., 1994 and Huang& Shu, 1995. However significant dilution of dye containing waste is required for the effective use of UV oxidation. FLOATATION; A novel method using colloidal gas aphrons (CGA) was advised by Roy et. Al in 1992. CGA is bubble encapsulated in a thin, aqueous soapy film. The dyes are encapsulated in the soapy shells of the CGAs due to coulombic attraction between the dye and the surfactant molecules and helps in removal of dye due to floatation. Membrane separation technology, and biological degradation are some of the alternative methods for removal of color. All these methods suffer from one or the other drawbacks. Some of these methods require stringent process conditions. Some are cost intensive, takes longer time to be effective or require large infrastructure. Thus there is a need to develop a simple cost effective method wherein the dye also can be recovered and recycled, if so desired. The main object of the present invention is to provide a simple & effective method for removal of water-soluble dye adopting liquid liquid extraction mechanism. Another object of the present invention is to remove water-soluble dye using reverse micelle. Still another object is to provide a method that is feasible on industrial scale. Yet another object is to provide a method that adopts low maintenance technology and does not require any sophisticated infrastructure. Still another object is to provide a method that is not time consuming. Another object of the present invention is to provide a process that is precise and reproducible. Still yet another object of the present invention is to provide a method that can facilitate easy recovery of dye, using counter-ionic surfactants, for recycling or re-use purposes. The reverse micelles are spontaneously and reversibly formed nanometer-sized aggregates of surfactant molecules surrounding microscopic water core in non-polar solvents. The reverse micelles are formed by contacting an aqueous phase with an immiscible organic phase containing surfactants. The reverse micelle formation occurs in organic solvents in order to minimize interactions between the polar heads of surfactant in non-polar medium. The polar head-groups of surfactant molecules form the core of aggregates while their hydrophobic parts face the apolar solvent. The polar head-groups are drawn together by hydrogen bonding in the presence of minimal amount of water and they are thermodynamically stable. The mean aggregation number of reverse micelles in dry solvent is significantly smaller than the normal micelles. Thus, the concept of Critical Micelle Concentration (CMC) used for surfactants in aqueous solution is not generally transferable to reverse micelle. The reverse micelles, also called as water-in-oil micro emulsions, possess special characteristics of spontaneous formation, isotropically clear appearance, low viscosity, relatively large interfacial area, ultra low interfacial tension and large solubilisation capacity. All these properties attribute higher potential for use of reverse micelles for effective and efficacious removal of water-soluble dyes from liquid waste. This is the first time ever, the reverse micelles are being used for removal of water-soluble dye from liquid wastes. Accordingly the present invention provides an improved process for de dyeing of liquid waste which comprises of following steps: a) contacting waste water containing organic ionic dye in solution form with the oppositely charged surfactant in water immiscible solvent under stirring, b) transferring the dispersion thus formed to a separating chamber, and c) separating colorless water phase and solvent phase containing dye encapsulated reverse micelle by gravity followed by recovering the encapsulated dye using counter-ionic surfactant if so desired. One of the embodiment of the present invention is that the surfactants used may be cationic or anionic surfactants soluble in water immiscible solvents depending on the type of dye intended to be removed. However, the surfactants used may preferably be, but not limited to, Sodium Dodecylbenzene Sulfonate (SDBS), Hexadecyltrimethyl Ammonium Bromide (HTAB), Cetylpyridinium Chloride (CPC), and Sodium-2-diethyl hexyl sulfosuccinate (AOT). SDBS and AOT are anionic in nature with CMC values of 500 and 1110 respectively, while CPC and HTAB are cationic in nature, having CMC values of 525 and 350 respectively. The other embodiment of the present invention is that the solvents used may be aliphatic or aromatic alcohols with C > 7, or their aromatic esters. The alcohols used may be exemplified by, but not restricted to, amyl alcohol, benzyl alcohol, iso-octane and methyl benzoate, preferably amyl alcohol. Another embodiment of the present invention is that the potential dyes that can be removed by the process of the present invention may be such as: Basic Dyes: - Rhodamine B, Magenta P, Methy Violet 2B, Victoria Blue B H/C, Diamond Green , Malachite Green XLS, Bismark Brown G, Acidic Dyes: - Tartrazine NS, Yellow GL, Metanil Yellow, Orange GT, Orange II , Crystal Orange G, Orange MSRL , Croceine S. MOO, Scarlet 3R , Milling Scarlet G, Scarlet ML , Fast Red A, Milling Red RS, Red 3BN, Silk Red 3B, Red 3B Maroon V , Violet MB , Violet 4BS, Patent Blue AS, Blue C2G , Navy Blue MTR, Navy Blue 2RNX, Leather Br. HEDG, Brown SG , Brown 5G , Brown, Brown 2RL, Resorcine Brown RD, Black 10BX , Black WA, Black NB, Black MRL, Green 6B , Black MR Further, the solvent to water ratio varies from 1:1 to 1:10, preferably 1:2. Ratio of Dye: Solvent: Water: Surfactant may be 20-40mg: 50ml: 100ml: 30- 40mg preferably 30 mg: 50 ml: 100 ml: 40mg.. Increase in the surfactant may require more phase separation time. The pH may be between 3 to 7 when cationic surfactant is used and >7.0 when anionic surfactant is used. Still other embodiment of the present invention is that the process can be conducted at a temperature ranging from 10° to 50° C without significant change in the efficiency. However, Room temperature is preferred. Yet another embodiment of the present invention is that the contacting of liquid waste and surfactant solution may be effected for a period of 5 minutes preferably for 15 minutes. Still yet another embodiment of the present invention is that the separation of two phases in step (c), may be performed for a period of 40 minutes to 2 hours if solvent used is amyl alcohol, 3 to 4 hours when benzyl alcohol is used as solvent and 7 to 8 hours when solvent used is benzyl ester. The process of the present invention is described below in detail: The removal of organic dyes by liquid liquid extraction method using reverse micelles was conducted in two steps. In the first step, a given volume of aqueous solution containing dye was added to the solvent containing oppositely charged surfactant under continuous stirring. This results in the formation of reverse micelle with the dye molecules encapsulated in them with simultaneous transfer of the reverse micelles to the solvent phase. In the second phase two-phase dispersion was transferred to a separating chamber such as separating funnel to enable separating the solvent and aqueous phases by gravity. The colorless water phase on separation can be used for various purposes while the solvent phase containing dye encapsulated reverse micelles can be discarded or further treated with counter ionic surfactant to recover the dye if so desired. The invention is further defined by reference to the following example, which is intended to be illustrative. The examples are not meant to limit in any manner the effective scope of the invention as herein defined and claimed. Consequently, any variation of the invention described above is not to be regarded as departure from the scope of the invention claimed. The invention has been described in terms of its embodiments and certain modifications and equivalents as will be apparent to those skilled in the art and are intended to be included within the scope of present invention. Further the invention is also described with reference to the drawing in which Fig. I represents the schematic diagram of the process of the present invention. EXAMPLE 1 100 ml aqueous phase containing 20 mg methyl orange or eosin yellow or orange G dye (anionic) present in is gently mixed with 50 ml amyl alcohol containing 30 mg hexadecyl trimethyl ammonium bromide (HTAB) or cetyl pyridinium chloride (CPC) surfactants (cationic) for five min in a container. Normally equilibrium is reached with in the stirring time as mentioned. On reaching equilibrium, the whole mixture is transferred to a separating column where clean aqueous phase is separated from the dye encapsulated reverse micelles present in amyl alcohol in about one hour due to gravity. 100% removal of dye from aqueous phase is estimated through UV spectrophotometer. If 40 mg methyl orange or eosin yellow or orange G dye is present initially in the aqueous phase, 90 % removal of dye is observed when 30 mg HTAB or CPC is used in 50 ml amyl alcohol. Removal of anionic dye is increased to about 20% at high pH (i e., 10-12) compared to low pH ( EXAMPLE 2 100 ml aqueous phase containing 30 mg methylene blue or malachite green dye (cationic) is gently mixed with 50 ml amyl alcohol containing 40 mg sodium dodecyl benzene sulphonate (SDBS) or Aerosol-OT (AOT) surfactants (anionic) for five min in a container. Normally equilibrium is reached with in the stirring time as mentioned. The whole mixture is then transferred to a separating column where clean aqueous phase is separated from the dye encapsulated reverse micelles present in amyl alcohol in about one hour due to gravity. 100% removal of dye from aqueous phase is estimated through UV spectrophotometer. If 40 mg methylene blue or malachite is present initially in the aqueous phase, 95 % removal of dye is observed when 40 mg AOT or SDBS is used in 50 ml amyl alcohol. Removal of cationic dye is increased to about 20% at low pH (i e., 3-5) compared to high pH (>7). Similar percentage removal for all the cationic and anionic dyes is obtained when benzyl alcohol or methyl benzoate solvent is used instead of amyl alcohol for the formation of reverse micelles. When iso-octane is used as solvent, higher quantity of surfactant was required for the same percentage removal of dye obtained for the other solvents as mentioned above. For example, 80 mg AOT in 50 ml iso-octane is required for the 90 % removal of 20 mg malachite green from 100 ml aqueous phase. Phase separation of amyl alcohol (50 ml) from aqueous phase (100 ml) is faster (one hour) in the presence of 30 mg HTAB compared to other solvents (benzyl alcohol: four hours; methyl benzoate: 8 hours). Thus the residence time for the dye removal process by reverse micelles depends on the phase separation time since the transfer of dye from aqueous phase reverse micelle phase is very fast (2-3 min.). No appreciable effect of temperature on the percentage removal of dye was observed when all the phases taking part in the dye removal process is varied between 10° C to 50° C. ADVANTAGES: • The process is simple & effective. • The process is precise and reproducible. • The process is feasible on industrial scale. • The process adopts low maintenance technology and hence does not require sophisticated infrastructure. • The process is time saving and environment friendly. • The process facilitates recovery of dye using counter ionic surfactants for recycling. We Claim: 1. An improved process for de dyeing of liquid waste which comprises of following steps: a) contacting waste water containing organic ionic dye in solution form with the oppositely charged surfactant in water immiscible solvent under stirring, b) transferring the dispersion thus formed to a separating chamber, & c) separating colorless water phase and solvent phase containing dye encapsulated reverse micelle by gravity followed by recovering the encapsulated dye using counter-ionic surfactant if so desired. 2. An improved process as claimed in claim 1, wherein the surfactant used is cationic or anionic that is soluble in water immiscible solvent. 3. An improved process as claimed in claim 1, wherein the anionic surfactant used is the one with CMC values between 500 and 1110 respectively and is preferably selected from Sodium Dodecylbenzene Sulfonate (SDBS), and Sodium-2-diethyl hexyl sulfosuccinate (AOT) 4. An improved process as claimed in claim 1, wherein cationic surfactant used is the one having CMC values of 525 and 350 respectively and is preferably selected from Hexadecyltrimethyl Ammonium Bromide (HTAB), Cetylpyridinium Chloride (CPC). 5. An improved process as claimed in claim 1, wherein water immiscible solvent used is aliphatic or aromatic alcohol having C > 7, or their ester. 6. An improved process as claimed in claim 1 & 5, wherein the alcohol used is amyl , benzyl, iso-octane preferably amyl alcohol. 7. An improved process as claimed in claim 1,5 & 6, wherein the ester used is methyl benzoate. 8. An improved process as claimed in claim 1, wherein the ratio of water immiscible solvent to waste water ranges from 1:1 to 1: 10. 9. An improved process as claimed in claim 1& 8 wherein the ratio of solvent to waste water is 2:1. 10. An improved process as claimed in claim 1, wherein the ratio of dye: solvent: water: surfactant varies between 20-40 mg: 50 ml: 50-500 ml: 30-40 mg preferably 30 mg: 50 ml: 100 ml: 40mg. 1 l.An improved process as claimed in claim 1, wherein the contacting is effected at a temperature of 10 to 50 C, preferably at ambient temperature. 12. An improved process as claimed in claim 1, wherein the contacting is effected for a period of 5 minutes preferably for 15 minutes. 13. An improved process as claimed in claim 1, wherein the contacting is carried out at a pH between 3 to 7 when surfactant used is cationic and pH > 7 when anionic surfactant is used. 14. An improved process as claimed in claim 1, wherein the separation of two phases in step (c), is performed for a period of 40 minutes to 2 hours if solvent used is amyl alcohol, 3 to 4 hours when benzyl alcohol is used as solvent and 7 to 8 hours when solvent used is benzyl ester. 15. An improved process for de dyeing of liquid waste substantially as here in described.

Full Text

The present invention relates to an improved process for de dyeing of liquid waste. The invention particularly relates to removal of dyes from liquid waste by liquid liquid extraction. More particularly, the invention relates to removal of organic ionic dyes by liquid liquid extraction using reverse micelle. Dyes are, generally, cyclic organic compounds with relatively high molecular weights, ionic in nature and soluble in water. Almost every industry, but mainly textile industry uses dyes to color its products. Effluents from industries such as carpet manufacturing, dyeing, textile, pulp & paper, leather, and distillery contain various types of dyes that should be removed before discharging the effluent to the environment in the interest of public order and impairment of ecosystem. Though some dyes are inert and nontoxic in nature particularly at the level of concentration discharged into the receiving water, the colour they impart is very undesirable due to adverse aesthetic effect, some dyes at a concentration of COAGULATION& SEDIMENTATION: _1. Japanese Patent No. JP 551786 published on 04-12-1980, teaches de-dyeing
of dyeing waste water to colorless and transparent water using Al (OH) 3 and Al2O3 as coagulating agent.
2. Canadian Patent No. CN 1121488 published on 01-05-1996 advocates use of ferric salts as coagulant for removal of color from dyeing waste water.
3. Japanese Patent No.JP 2000095802 published on 04-04-2000 describes use of new polysaccharide produced by a specific gram-negative bacterium as a coagulant. These methods result in generation of large quantity of sludge and thus appear to be uneconomical as they require additional infrastructure for disposal of sludge.
ADSORPTION METHOD:
1. PCT Patent application No. WO 02/42228 published on 30-05-2002 relates to using bioadsorbent material for removal of color. The bioadsorbent material is a specific bacterium immobilized on charcoal. However, it is applicable to removal of color from textile effluents containing azo dye.
2. Poots et al proposed in 1976, peat, wood as an adsorbent for the removal dye. Silica, charcoal, hard wood sawdust, bentonite clay, rice husk, fly ash are couple of other adsorbents, which find potentially useful for color removal. However, these adsorbents pose the problem of regeneration. Additionally some of them are quite expensive.
OXIDATION METHOD:
Among oxidation methods, UV/ozone or UV/H2O2 is found to be better
technology for removal of dye from wastewater. A refernce can be made to Ruppet et al., 1994 and Huang& Shu, 1995. However significant dilution of dye
containing waste is required for the effective use of UV oxidation.
FLOATATION;
A novel method using colloidal gas aphrons (CGA) was advised by Roy et. Al in 1992. CGA is bubble encapsulated in a thin, aqueous soapy film. The dyes are encapsulated in the soapy shells of the CGAs due to coulombic attraction between the dye and the surfactant molecules and helps in removal of dye due to floatation.
Membrane separation technology, and biological degradation are some of the alternative methods for removal of color.
All these methods suffer from one or the other drawbacks. Some of these methods require stringent process conditions. Some are cost intensive, takes longer time to be effective or require large infrastructure. Thus there is a need to develop a simple cost effective method wherein the dye also can be recovered and recycled, if so desired.
The main object of the present invention is to provide a simple & effective method for removal of water-soluble dye adopting liquid liquid extraction mechanism.
Another object of the present invention is to remove water-soluble dye using reverse micelle.
Still another object is to provide a method that is feasible on industrial scale. Yet another object is to provide a method that adopts low maintenance technology and does not require any sophisticated infrastructure. Still another object is to provide a method that is not time consuming. Another object of the present invention is to provide a process that is precise and reproducible.
Still yet another object of the present invention is to provide a method that can facilitate easy recovery of dye, using counter-ionic surfactants, for recycling
or re-use purposes.
The reverse micelles are spontaneously and reversibly formed nanometer-sized aggregates of surfactant molecules surrounding microscopic water core in non-polar solvents. The reverse micelles are formed by contacting an aqueous phase with an immiscible organic phase containing surfactants. The reverse micelle formation occurs in organic solvents in order to minimize interactions between the polar heads of surfactant in non-polar medium. The polar head-groups of surfactant molecules form the core of aggregates while their hydrophobic parts face the apolar solvent. The polar head-groups are drawn together by hydrogen bonding in the presence of minimal amount of water and they are thermodynamically stable. The mean aggregation number of reverse micelles in dry solvent is significantly smaller than the normal micelles. Thus, the concept of Critical Micelle Concentration (CMC) used for surfactants in aqueous solution is not generally transferable to reverse micelle. The reverse micelles, also called as water-in-oil micro emulsions, possess special characteristics of spontaneous formation, isotropically clear appearance, low viscosity, relatively large interfacial area, ultra low interfacial tension and large solubilisation capacity. All these properties attribute higher potential for use of reverse micelles for effective and efficacious removal of water-soluble dyes from liquid waste.
This is the first time ever, the reverse micelles are being used for removal of water-soluble dye from liquid wastes.
Accordingly the present invention provides an improved process for de dyeing of liquid waste which comprises of following steps:
a) contacting waste water containing organic ionic dye in solution form with the oppositely charged surfactant in water immiscible solvent under stirring,
b) transferring the dispersion thus formed to a separating chamber, and
c) separating colorless water phase and solvent phase containing dye encapsulated reverse micelle by gravity followed by recovering the encapsulated dye using counter-ionic surfactant if so desired.
One of the embodiment of the present invention is that the surfactants used may
be cationic or anionic surfactants soluble in water immiscible solvents
depending on the type of dye intended to be removed.
However, the surfactants used may preferably be, but not limited to, Sodium
Dodecylbenzene Sulfonate (SDBS), Hexadecyltrimethyl Ammonium Bromide
(HTAB), Cetylpyridinium Chloride (CPC), and Sodium-2-diethyl hexyl
sulfosuccinate (AOT). SDBS and AOT are anionic in nature with CMC values of
500 and 1110 respectively, while CPC and HTAB are cationic in nature, having
CMC values of 525 and 350 respectively.
The other embodiment of the present invention is that the solvents used may be
aliphatic or aromatic alcohols with C > 7, or their aromatic esters. The alcohols
used may be exemplified by, but not restricted to, amyl alcohol, benzyl alcohol,
iso-octane and methyl benzoate, preferably amyl alcohol.
Another embodiment of the present invention is that the potential dyes that can
be removed by the process of the present invention may be such as:
Basic Dyes: -
Rhodamine B, Magenta P, Methy Violet 2B, Victoria Blue B H/C, Diamond Green , Malachite Green XLS, Bismark Brown G,
Acidic Dyes: -
Tartrazine NS, Yellow GL, Metanil Yellow,
Orange GT, Orange II , Crystal Orange G, Orange MSRL , Croceine S. MOO,
Scarlet 3R , Milling Scarlet G, Scarlet ML , Fast Red A, Milling Red RS,
Red 3BN, Silk Red 3B, Red 3B Maroon V , Violet MB , Violet 4BS, Patent Blue AS, Blue C2G , Navy Blue MTR, Navy Blue 2RNX, Leather Br. HEDG, Brown SG , Brown 5G , Brown, Brown 2RL, Resorcine Brown RD, Black 10BX , Black WA, Black NB, Black MRL, Green 6B , Black MR
Further, the solvent to water ratio varies from 1:1 to 1:10, preferably 1:2. Ratio of Dye: Solvent: Water: Surfactant may be 20-40mg: 50ml: 100ml: 30-
40mg preferably 30 mg: 50 ml: 100 ml: 40mg.. Increase in the surfactant may
require more phase separation time. The pH may be between 3 to 7 when
cationic surfactant is used and >7.0 when anionic surfactant is used.
Still other embodiment of the present invention is that the process can be
conducted at a temperature ranging from 10° to 50° C without significant
change in the efficiency. However, Room temperature is preferred.
Yet another embodiment of the present invention is that the contacting of
liquid waste and surfactant solution may be effected for a period of 5
minutes preferably for 15 minutes.
Still yet another embodiment of the present invention is that the separation
of two phases in step (c), may be performed for a period of 40 minutes to 2
hours if solvent used is amyl alcohol, 3 to 4 hours when benzyl alcohol is
used as solvent and 7 to 8 hours when solvent used is benzyl ester.
The process of the present invention is described below in detail:
The removal of organic dyes by liquid liquid extraction method using reverse
micelles was conducted in two steps. In the first step, a given volume of
aqueous solution containing dye was added to the solvent containing
oppositely charged surfactant under continuous stirring. This results in the
formation of reverse micelle with the dye molecules encapsulated in them
with simultaneous transfer of the reverse micelles to the solvent phase. In the
second phase two-phase dispersion was transferred to a separating chamber such as separating funnel to enable separating the solvent and aqueous phases by gravity. The colorless water phase on separation can be used for various purposes while the solvent phase containing dye encapsulated reverse micelles can be discarded or further treated with counter ionic surfactant to recover the dye if so desired.
The invention is further defined by reference to the following example, which is intended to be illustrative. The examples are not meant to limit in any manner the effective scope of the invention as herein defined and claimed. Consequently, any variation of the invention described above is not to be regarded as departure from the scope of the invention claimed. The invention has been described in terms of its embodiments and certain modifications and equivalents as will be apparent to those skilled in the art and are intended to be included within the scope of present invention. Further the invention is also described with reference to the drawing in which Fig. I represents the schematic diagram of the process of the present invention.
EXAMPLE 1
100 ml aqueous phase containing 20 mg methyl orange or eosin yellow or orange G dye (anionic) present in is gently mixed with 50 ml amyl alcohol containing 30 mg hexadecyl trimethyl ammonium bromide (HTAB) or cetyl pyridinium chloride (CPC) surfactants (cationic) for five min in a container. Normally equilibrium is reached with in the stirring time as mentioned. On reaching equilibrium, the whole mixture is transferred to a separating column where clean aqueous phase is separated from the dye encapsulated reverse
micelles present in amyl alcohol in about one hour due to gravity. 100% removal of dye from aqueous phase is estimated through UV spectrophotometer. If 40 mg methyl orange or eosin yellow or orange G dye is present initially in the aqueous phase, 90 % removal of dye is observed when 30 mg HTAB or CPC is used in 50 ml amyl alcohol. Removal of anionic dye is increased to about 20% at high pH (i e., 10-12) compared to low pH ( EXAMPLE 2
100 ml aqueous phase containing 30 mg methylene blue or malachite green dye (cationic) is gently mixed with 50 ml amyl alcohol containing 40 mg sodium dodecyl benzene sulphonate (SDBS) or Aerosol-OT (AOT) surfactants (anionic) for five min in a container. Normally equilibrium is reached with in the stirring time as mentioned. The whole mixture is then transferred to a separating column where clean aqueous phase is separated from the dye encapsulated reverse micelles present in amyl alcohol in about one hour due to gravity. 100% removal of dye from aqueous phase is estimated through UV spectrophotometer. If 40 mg methylene blue or malachite is present initially in the aqueous phase, 95 % removal of dye is observed when 40 mg AOT or SDBS is used in 50 ml amyl alcohol. Removal of cationic dye is increased to about 20% at low pH (i e., 3-5) compared to high pH (>7).
Similar percentage removal for all the cationic and anionic dyes is obtained when benzyl alcohol or methyl benzoate solvent is used instead of amyl alcohol for the formation of reverse micelles. When iso-octane is used as
solvent, higher quantity of surfactant was required for the same percentage removal of dye obtained for the other solvents as mentioned above. For example, 80 mg AOT in 50 ml iso-octane is required for the 90 % removal of 20 mg malachite green from 100 ml aqueous phase.
Phase separation of amyl alcohol (50 ml) from aqueous phase (100 ml) is faster (one hour) in the presence of 30 mg HTAB compared to other solvents (benzyl alcohol: four hours; methyl benzoate: 8 hours). Thus the residence time for the dye removal process by reverse micelles depends on the phase separation time since the transfer of dye from aqueous phase reverse micelle phase is very fast (2-3 min.).
No appreciable effect of temperature on the percentage removal of dye was observed when all the phases taking part in the dye removal process is varied between 10° C to 50° C.
ADVANTAGES:
• The process is simple & effective.
• The process is precise and reproducible.
• The process is feasible on industrial scale.
• The process adopts low maintenance technology and hence does not require sophisticated infrastructure.
• The process is time saving and environment friendly.
• The process facilitates recovery of dye using counter ionic surfactants for recycling.

We Claim:
1. An improved process for de dyeing of liquid waste which comprises of following steps:
a) contacting waste water containing organic ionic dye in solution form with the oppositely charged surfactant in water immiscible solvent under stirring,
b) transferring the dispersion thus formed to a separating chamber, &
c) separating colorless water phase and solvent phase containing dye encapsulated reverse
micelle by gravity followed by recovering the encapsulated dye using counter-ionic surfactant if so desired.
2. An improved process as claimed in claim 1, wherein the surfactant used is cationic or anionic that is soluble in water immiscible solvent.
3. An improved process as claimed in claim 1, wherein the anionic surfactant used is the one with CMC values between 500 and 1110 respectively and is preferably selected from Sodium Dodecylbenzene Sulfonate (SDBS), and Sodium-2-diethyl hexyl sulfosuccinate (AOT)
4. An improved process as claimed in claim 1, wherein cationic surfactant used is the one having CMC values of 525 and 350 respectively and is preferably selected from Hexadecyltrimethyl Ammonium Bromide (HTAB), Cetylpyridinium Chloride (CPC).
5. An improved process as claimed in claim 1, wherein water immiscible solvent used is aliphatic or aromatic alcohol having C > 7, or their ester.
6. An improved process as claimed in claim 1 & 5, wherein the alcohol used is amyl , benzyl, iso-octane preferably amyl alcohol.
7. An improved process as claimed in claim 1,5 & 6, wherein the ester used is methyl benzoate.
8. An improved process as claimed in claim 1, wherein the ratio of water
immiscible solvent to waste water ranges from 1:1 to 1: 10.
9. An improved process as claimed in claim 1& 8 wherein the ratio of solvent to
waste water is 2:1.
10. An improved process as claimed in claim 1, wherein the ratio of dye: solvent: water: surfactant varies between 20-40 mg: 50 ml: 50-500 ml: 30-40 mg preferably 30 mg: 50 ml: 100 ml: 40mg.
1 l.An improved process as claimed in claim 1, wherein the contacting is effected at a temperature of 10 to 50 C, preferably at ambient temperature.
12. An improved process as claimed in claim 1, wherein the contacting is effected for a period of 5 minutes preferably for 15 minutes.
13. An improved process as claimed in claim 1, wherein the contacting is carried out at a pH between 3 to 7 when surfactant used is cationic and pH > 7 when anionic surfactant is used.
14. An improved process as claimed in claim 1, wherein the separation of two phases in step (c), is performed for a period of 40 minutes to 2 hours if solvent used is amyl alcohol, 3 to 4 hours when benzyl alcohol is used as solvent and 7 to 8 hours when solvent used is benzyl ester.
15. An improved process for de dyeing of liquid waste substantially as here in described.

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Patent Number

271063

Indian Patent Application Number

377/DEL/2003

PG Journal Number

06/2016

Publication Date

05-Feb-2016

Grant Date

29-Jan-2016

Date of Filing

26-Mar-2003

Name of Patentee

INDIAN INSTITUTE OF TECHNOLOGY-DELHI (IITD)

Applicant Address

HAUZ KHAS, NEW DELHI-110016, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	BASU SUDDHASATWA	DEPARTMENT OF CHEMICAL ENGINEERING INDIAN INSTITUTE OF TECHNOLOGY, HAUZ KHAS, NEW DELHI-110016, INDIA.

PCT International Classification Number

C02F 1/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA