Title of Invention	PROCESS FOR REMOVKING A SOLUBLE METAL CONTAINED IN ACIDIC AND/OR BASIC EFFLUENTS ORIGINATING FROM ORGANIC SYNTHESES
Abstract	Process for removing a soluble metal contained in acidic and/or basic effluents originating from organic syntheses The process of the invention for removing a soluble metal comprises the following steps carried out continuously: a) providing basic effluents containing the metal; b) adding a strong acid to the basic effluents until a pH with a value of between 0 and 4 is obtained; c) maintaining the pH at this value; d) adding a complexing agent to precipitate the metal, while monitoring the progress of the precipitation reaction and allowing the resulting solution to decant; and e) filtering the solution to recover acidic slurries containing the precipitated metal, on the one hand, and a filtrate with a reduced content of metal, on the other hand. Application in particular to the processing of phthalocyanin-based pigments.

Title of Invention

PROCESS FOR REMOVKING A SOLUBLE METAL CONTAINED IN ACIDIC AND/OR BASIC EFFLUENTS ORIGINATING FROM ORGANIC SYNTHESES

Abstract

Process for removing a soluble metal contained in acidic and/or basic effluents originating from organic syntheses The process of the invention for removing a soluble metal comprises the following steps carried out continuously: a) providing basic effluents containing the metal; b) adding a strong acid to the basic effluents until a pH with a value of between 0 and 4 is obtained; c) maintaining the pH at this value; d) adding a complexing agent to precipitate the metal, while monitoring the progress of the precipitation reaction and allowing the resulting solution to decant; and e) filtering the solution to recover acidic slurries containing the precipitated metal, on the one hand, and a filtrate with a reduced content of metal, on the other hand. Application in particular to the processing of phthalocyanin-based pigments.

Full Text	1A The invention relates to the processing of industrial effluents originating from various organic synthesis processes. The invention relates more particularly to a process for removing a soluble metal contained in acidic and/or basic effluents originating from organic syntheses, in particular the synthesis of pigments. Organic synthesis processes exist which lead to acidic and/or basic effluents containing a metal which should be removed, partially or totally, in order to be able to discharge these effluents into a river, and thus to satisfy the increasingly strict standards imposed by legislation in force This is the case in particular for the synthesis of certain pigments, such as pigments of the phthalocyanin type which are used in industry in the manufacture of dyes, inks, paints, etc. The phthalocyanin derivatives contained in these pigments can be, in particular, iron, nickel, cobalt, copper, etc. phthalocyanin. The conventional processes for synthesizing these pigments proceed in several steps and lead to the production of acidic and/or basic effluents containing large amounts of metal which should be reduced substantially in order to be able to discharge them into a river. Usually, these acidic and/or basic effluents are combined and are then subjected to a batchwise processing operation. These removal processes, carried out in a batchwise manner, require large-volume storage tanks. In addition, the removal Of the metal is generally carried,out using reagents which need to, be used in large amounts, and whose cost is prohibitive. - 2 - The aim of the invention is, in particular, to overcome the abovementioned drawbacks. The invention is directed more particularly towards providing a process for removing soluble metal, as defined above, which can be carried out continuously and at lower cost than the processes of the prior art. The invention is also directed towards providing such a removal process which can be applied to acidic and/or basic effluents originating most particularly from an organic synthesis of pigments, in particular of phthalocyanin-based pigments. In this particular case, the invention is directed towards providing a process for recovering the metal contained both in acidic effluents and in basic effluents originating from such an organic synthesis of pigments. To this end, the invention proposes a process for removing a soluble metal, as defined in the introduction, in which the process comprises the following steps carried out continuously: a) supplying basic effluents containing the metal; b) adding a strong acid to the basic effluents until a pH with a value of between 0 and 4 is obtained; c) maintaining the pH at this value; d) adding a complexing agent to precipitate the metal, while monitoring the progress of the precipitation reaction and allowing the resulting solution to decant; and e) filtering the solution to recover acidic slurries containing the precipitated metal, on the one hand, and a filtrate with a reduced content of metal, on the other hand. Thus, the process of the invention is carried out continuously and is based essentially on a complexation of the metal contained in basic effluents, which is performed under specific pH conditions, while at the same time monitoring the progress of a precipitation reaction. - 3 - Surprisingly, this precipitation reaction is carried out at a very acidic pH, since it is between 0 and 4, while at the same time monitoring the progress of the precipitation reaction. Decantation and filtration of the resulting solution gives, on the one hand, slurries which contain the precipitated metal and which can be incinerated, and, on the other hand, a filtrate with a substantially reduced content of metal, which can be discharged into a river. This process thus differs from the prior art in that the precipitation reaction proceeds at a very acidic pH, rather than at a more or less neutral pH. As a result, small amounts of complexing agent can be used relative to the amount of solution to be treated. The strong acid used in step b) is advantageously sulphuric acid. In steps b) and c) , the pH value is preferably more or less equal to 3. In step d), the complexing agent is advantageously a carbamate derivative, in particular sodium dimethyldithiocarbamate. According to another characteristic of the invention, the monitoring of the precipitation reaction in step d) comprises monitoring the electrical potential of the solution, and the addition of the complexing agent is carried out for as long as the electrical potential measured has not reached a chosen value. The monitoring of the electrical potential is preferably carried out with the aid of a redox electrode pf the Ag/AgCl type, while the value chosen corresponds to an electrical potential of between 150 and 300 mV; According to another characteristic of the invention, the decantation in step d) is carried out in the presence of an agent which promotes decantation, in particular ferric chloride. In step e) , the filtration is preferably carried out with the aid of a filter press. - 4 - In one preferred application of the invention, the basic effluents in step a) comprise basic effluents originating from an organic synthesis, as a mixture with a basic filtrate resulting from a process for propessing acidic effluents. In particular, the basic effluents in step a) advantageously Originate from a reaction for synthesizing a pigment, in particular a metal phthalo-cyanin. The basic filtrate advantageously originates from a process for flocculating acidic effluents, leading to the production of basic slurries and the said filtrate. These basic effluents can originate from a reaction for synthesizing a pigment, in particular a metal phthalocyanin. Thus, the invention envisages processing both basic effluents and acidic effluents originating from the same reaction for synthesizing a pigment, in particular a metal phthalocyanin. It is thus possible to process these two effluents separately in order to reduce the metal content thereof, instead of processing them together after mixing, as in the previous technique. The invention applies in particular to a process in which the metal to be removed is chosen from iron, cobalt, nickel and corjper. In the description which, follows, given purely by way of example, reference is made to the attached accompanying drawings, in which: - Figure 1 is a flow diagram of a plant for removing a metal contained in acidic effluents originating from an organic synthesis of phthalocyain-based pigments, this plant using a process according to the invention; - Figure 2 is a diagram of a plant for removing metal contained in basic effluents originating from the same process for synthesizing phthalocyanin-based pigments, this plant using a process according to the invention. - 5 - The process according to the invention will be explained in the particular case of processing acidic effluents and basic effluents originating from a process for synthesizing phthalocyanin-based pigments, also referred to as phthalocyanin blue, i.e. a phthalo-cyanin of a metal chosen essentially from iron, cobalt, nickel and copper. In the example attention will be focused on copper phthalocyanin. The diagram in Figure 1 shows a tank 1 for containing acidic effluents originating from the synthesis of pigments of the abovementioned type and containing, in the example, a metal, namely copper. The effluents originating from tank 1 are sent via a pump 2 through a heat exchanger 3 to cool them. Next, these effluents are sent successively into two tanks 4 and 5 in which they are kept stirring and are neutralized by addition of a strong base, sodium hydroxide in the example, until a pH = 8 is obtained. In the example, the strong base is 30% sodium hydroxide originating from storage tanks 22 and 23 and sent, respectively, via pumps 24 and 25. The effluents at pH 8 are introduced into a flocculation tank 6, which is kept stirring, into which is introduced a flocculant originating from a preparation station 7 and sent by means of a pump 8. In the example, an aqueous solution of a flocculant polymer at 1 g/1 is used. The flocculant used is the product known under the brand name Praestol 2540 from the company Stockhausen. About 1 ml of this solution of flocculant is added to 1 litre of effluent, which gives a suspension that is sent to a decantation vat 9. This makes it possible to recover, on the one hand, slurries (line 10) and, on the other hand, a basic filtrate (line 11). The slurries are sent via a pump 12 into a thickener 13 which also receives ferric chloride originating from a container 14 and sent via a pump 15. These slurries are then sent via a pump 16 to a filter press 17 and from there are - 6 - recovered in a skip 18 in order then to be sent to an incineration factory. A basic filtrate is recovered from the filter press 17 and sent to a homogenization tank 29, which is described later with reference to Figure 2. Mother liquors are recovered at the filter press outlet and are sent via a line 19 to a recovery tank 20. These liquors are recovered and sent via a pump 21 to the tank 4. Thus, the plant represented in Figure 1 makes it possible to remove the metal (copper in the example) contained in the acidic effluents, producing, on the one hand, slurries which can be incinerated, and, on the other hand, a filtrate (line 11) which is basic and which still contains metal. This filtrate is also used as starting material in the plant in Figure 2. Reference is now made to Figure 2 to describe the plant for processing the basic effluents. The basic effluents originating from the same process for synthesizing phthalocyanin-based pigments are sent to a tank 26, from where they are taken by means of a pump 27 and sent to a heat exchanger 28 to cool them. Next, these effluents are sent to a homogenization tank 29 which also receives the basic filtrates from the plant in Figure 1. The tank 29 is kept stirring to bring about mixing of the basic effluents and the basic filtrates. The pH of the mixture contained in tank 29 is generally between 10 and 12. The mixture thus homogenized is sent to a tank 30 which is kept stirring and into which is introduced an insolubilizing agent, also referred to as a complexing agent, originating from a storage station 31 and sent via a line 32 by means of a pump 33. In the example, a complexing agent of the carbamate type is used, and advantageously sodium dimethyldithiocarbamate. A strong acid is also added to the tank 30, in the example 98% sulphuric acid, originating from a storage tank 34 and sent via a - 7 - pump 35 through a recycling loop 36 which returns to the storage tank 34. It is essential for the pH of the solution contained in the tank 30 to be adjusted and maintained at an acidic value of between 0 and 4, and preferably substantially equal to 3. To do this, a regulation is carried out on the addition of the sulphuric acid in order to keep this pH constant. This results in a precipitation reaction of the metal, the progress of which reaction is monitored by suitable means. In the example, the electrical potential of the solution is measured using a redox electrode of the Ag/AgCl type, and this complexing agent is added until a potential whose value is chosen as a function of the amount of copper to be complexed is obtained. This value is generally between 150 and 300 mV. As soon as the potential measured reaches this chosen value, the addition of the complexing agent is stopped. An insoluble complex is thus formed in a flocculation tank 37 kept stirring. After flocculation, the solution is sent to a decantation vat 38, thereby allowing the recovery of slurries, which are sent via a pump 39 to a slurry thickener 40. Moreover, effluents with a reduced content of metal are recovered at the outlet of the decantation vat 38 and sent to a recovery tank 41 which feeds a sand filter 42 via a pump 43. Decantation liquors are also recovered at the outlet of the decantation vat 38 and are sent via a line 44 to the tank 20 described previously with reference to Figure 1. A slurry suspension is recovered at the base of the slurry thickener 40 and is sent via a pump 45 to the filter press 17 in Figure 1. The slurry thickener 40 also receives ferric chloride originating from a storage tank 46 and sent via a pump 47. A supernatant is also drawn from the - 8 - slurry thickener 40 and is recycled via a line 48 into the flocculation tank 37. Filtered effluents are drawn from the sand filter 42 and are sent into a tank 49. From there, these filtered effluents are sent via two pumps 50 and 51 to an industrial effluent purification plant 52. Thus, the process of the invention makes it possible to process both acidic effluents via the plant in Figure 1 and basic effluents via the plant in Figure 2, these two types of effluent originating from the same synthetic reaction. The plant in Figure 2 thus processes the basic effluents which have been mixed with the basic filtrates originating from the plant in Figure 1. In one embodiment, acidic effluents of a volume of 100 to 200 m3 per day with a copper content of from 300 to 500 mg/litre, thus representing 45 to 100 kg of copper per day, are processed. The pH of these acidic effluents is 0.5. By this same process, basic effluents representing a volume of from 50 to 75 m3 per day, with a copper content of from 30 to 50 mg/litre, which represents from 1.5 to 3.75 kg of copper per day, are processed. The pH of these basic effluents is 12. After processing by the process of the invention, a filtrate is recovered in a volume of from 150 to 275 m3 per day with a copper content of less than 0.2 mg/litre and having a pH more or less equal to 3. The invention will now be described with reference to two examples concerning a process for removing copper from industrial effluents resulting from the synthesis of pigments derived from copper phthalocyanin. These effluents are the result of a purification and a pigmentation of raw copper phthalocyanin. The effluents to be treated are basic and/or acidic effluents. - 9 - Example 1: Processing for 1 litre of acidic effluents containing soluble copper An aqueous solution (A) of a flocculant polymer at a concentration of 1 gram per litre is prepared. The acidic effluents to be processed, which contain soluble copper at a concentration of 300 to 500 milligrams/litre, are placed under stirring. The pH of these effluents may be between 0 and 6. In a first operation, the required amount of a strong base (for example sodium hydroxide) is added until a pH of 8 is obtained {the optimum pH may be between 7 and 9 depending on the case to be processed). A blue- to green-coloured colloid then forms, due mainly to the formation of copper hydroxide Cu (OH)2. To promote the decantation of the copper hydroxide, 1 millilitre of solution (A) is added per litre of acidic effluents to be processed. After decantation, the copper hydroxide precipitate is filtered off. When the filtration is carried out under pressure, copper slurries with a solids content of about 50% by weight are obtained. The degree of removal of copper from the acidic effluents after this operation is about 90%. To remove the remaining 10% of soluble copper, the process is performed as follows. From the first operation, about 900 ml of an effluent at pH 8 (the pH may be between 7 and 9 depending on the case to be processed) containing from 30 to 50 milligrams per litre of soluble copper are recovered. To process the 900 ml of effluents resulting from the processing of the first operation, the potential of the solution is monitored with a redox electrode. The solution to be processed is acidified to an optimum pH of 3 (the pH may be between 0 and 4 depending on the case under consideration) using a strong acid, for example hydrochloric acid. If the redox electrode is an electrode of the Ag/AgCl type, a metal-complexing agent (such as sodium dimethyldithio-carbamate) is added at pH 3 until an optimum potential - 10 - of about 230 mV is obtained. The addition of the complexing agent depends on the redox potential measured; the amount of complexing agent added depends on the concentration of soluble copper and on the type of copper complexes present in solution. A brown-coloured copper precipitate forms. To assist the decantation of this precipitate, a coagulant such as FeCl3 can be used. After decantation and filtration, a filtrate and copper slurries are recovered. The filtrate contains only 0.2 milligram per litre of soluble copper. If the filtration is carried out under pressure, the copper slurries have a solids content which can be up to 50% by weight. Example 2: Processing for 1 litre of acidic effluents and 1 litre of basic effluents both containing soluble copper The process is performed as in Example 1. From the first operation, about 900 ml of an effluent (B) at pH 8 (the pH may be between 7 and 9 depending on the case to be processed) containing from 30 to 50 milligrams per litre of soluble copper are recovered. The 900 ml of effluent (B) are mixed with 1 litre of basic effluents (C) at pH 12 (the pH may be between 8 and 13) containing from 10 to 70 milligrams per litre of soluble copper. The proportion between the volumes of the effluents (B) and (C) may be different from that mentioned in the example. To process the mixture of effluents (B) and (C), the potential of the solution is monitored with a redox electrode. The solution to be processed is acidified to an optimum pH of 3 (the pH may be between 0 and 4 depending on the case under consideration) using a strong acid, for example hydrochloric acid. If the redox electrode is an electrode of the Ag/AgCl type, a metal-complexing agent (such as sodium dimethyldithiocarbamate) is added at pH 3 until an optimum potential of about 230 mV is obtained. The - 11 - addition of the complexing agent depends on the redox potential measured; the amount of complexing agent added depends on the concentration of soluble copper and on the type of copper complexes present in solution. A brown-coloured copper precipitate forms. To assist the decantation of this precipitate, a coagulant such as FeCl3 can be used. After decantation and filtration, a filtrate and copper slurries are recovered. The filtrate contains only 0.2 milligram per litre of soluble copper. If the filtration is carried out under pressure, the copper slurries have a solids content which may be up to 50% by weight. Needless to say, the invention is not limited to the examples and embodiments described above but extends to other variants. Thus, although the invention has been described with particular reference to the removal of a metal in pigments of phthalocyanin type, it can be applied to the removal of a metal in other industrial effluents. WECLAMIE - 12- 1. Process for removing a soluble metal contained in acidic and/or basic effluents originating from an organic synthesis, in particular of pigments, characterized in that it comprises the following steps carried out continuously: a) providing basic effluents containing the metal;Sach as herein described' b) adding a strong acid such as herein described to the basic effluents until a pH with a value of between 0 and 4 is obtained; c) maintaining the pH at this value; such as herein describedd) adding a complexing agent to such as herein described precipitate the metal, while monitoring the progress of the precipitation reaction and allowing the resulting solution to decant; and e) filtering the solution to recover acidic slurries containing the precipitated metal, on the one hand, and a filtrate with a reduced content of metal, on the other hand. 2. Process according to Claim 1, characterized in that the strong acid used in step b) is sulphuric acid. 3. Process according to either of Claims 1 and 2, characterized in that, in steps b) and c), the pH value is more or less equal to 3. 4. Process according to one of Claims 1 to 3, characterized in that the complexing agent added in step d) is a carbamate derivative. 5. Process according to Claim 4, characterized in that the complexing agent is sodium dimethyldithio- carbamate. 6. Process according to one of Claims 1 to 5, characterized in that the monitoring of the precipitation reaction in step d) comprises monitoring the electrical potential of the solution, and in that the complexing agent is added for as long as the electrical potential measured has not reached a chosen value. 7. Process according to Claim 6, characterized in that the monitoring of the electrical potential in - 13 - step d) is carried out by means of a redox electrode of the Ag/AgCl type and in that the value chosen corresponds to an electrical potential of between 150 and 300 mV. 8. Process according to one of Claims 1 to 7, characterized in that the decantation in step d) is carried out in the presence of an agent which promotes decantation, in particular ferric chloride. 9. Process according to one of Claims 1 to 8, characterized in that the filtration in step e) is carried out by means of a filter press. 10. Process according to one of Claims 1 to 9, characterized in that the basic effluents in step a) comprise basic effluents originating from an organic synthesis as a mixture with a basic filtrate resulting from a process for processing acidic effluents. 11. Process according to Claims 1 to 8, characterized in that the basic effluents in step a) originate from a reaction for synthesizing a pigment, in particular a metal phthalocyanin. 12. Process according to either of Claims 10 and 11, characterized in that the basic filtrate originates from a process for flocculating acidic effluents, leading to the production of basic slurries and the said basic filtrate. 13. Process according to one of Claims 10 to 12, characterized in that the acidic effluents originate from a reaction for synthesizing a pigment, in particular a metal phthalocyanin. 14. Process according to Claims 11 and 13, taken in combination, characterized in that the basic effluents and the acidic effluents originate from the same reaction for synthesizing a pigment, in particular a metal phthalocyanin such as herein described. 15. Process according to one of Claims 1 to 14, characterized in that the metal to be removed is chosen from iron, cobalt, nickel and copper. Process for removing a soluble metal contained in acidic and/or basic effluents originating from organic syntheses The process of the invention for removing a soluble metal comprises the following steps carried out continuously: a) providing basic effluents containing the metal; b) adding a strong acid to the basic effluents until a pH with a value of between 0 and 4 is obtained; c) maintaining the pH at this value; d) adding a complexing agent to precipitate the metal, while monitoring the progress of the precipitation reaction and allowing the resulting solution to decant; and e) filtering the solution to recover acidic slurries containing the precipitated metal, on the one hand, and a filtrate with a reduced content of metal, on the other hand. Application in particular to the processing of phthalocyanin-based pigments.

Full Text

1A
The invention relates to the processing of industrial effluents originating from various organic synthesis processes.
The invention relates more particularly to a process for removing a soluble metal contained in acidic and/or basic effluents originating from organic syntheses, in particular the synthesis of pigments.
Organic synthesis processes exist which lead to acidic and/or basic effluents containing a metal which should be removed, partially or totally, in order to be able to discharge these effluents into a river, and thus to satisfy the increasingly strict standards imposed by legislation in force
This is the case in particular for the synthesis of certain pigments, such as pigments of the phthalocyanin type which are used in industry in the manufacture of dyes, inks, paints, etc.
The phthalocyanin derivatives contained in these pigments can be, in particular, iron, nickel, cobalt, copper, etc. phthalocyanin.
The conventional processes for synthesizing these pigments proceed in several steps and lead to the production of acidic and/or basic effluents containing large amounts of metal which should be reduced substantially in order to be able to discharge them into a river.
Usually, these acidic and/or basic effluents are combined and are then subjected to a batchwise processing operation.
These removal processes, carried out in a batchwise manner, require large-volume storage tanks.
In addition, the removal Of the metal is generally carried,out using reagents which need to, be used in large amounts, and whose cost is prohibitive.

- 2 -
The aim of the invention is, in particular, to overcome the abovementioned drawbacks.
The invention is directed more particularly towards providing a process for removing soluble metal, as defined above, which can be carried out continuously and at lower cost than the processes of the prior art.

The invention is also directed towards providing such a removal process which can be applied to acidic and/or basic effluents originating most particularly from an organic synthesis of pigments, in particular of phthalocyanin-based pigments.
In this particular case, the invention is directed towards providing a process for recovering the metal contained both in acidic effluents and in basic effluents originating from such an organic synthesis of pigments.
To this end, the invention proposes a process for removing a soluble metal, as defined in the introduction, in which the process comprises the following steps carried out continuously:
a) supplying basic effluents containing the metal;
b) adding a strong acid to the basic effluents until a
pH with a value of between 0 and 4 is obtained;
c) maintaining the pH at this value;
d) adding a complexing agent to precipitate the metal,
while monitoring the progress of the precipitation
reaction and allowing the resulting solution to decant;
and
e) filtering the solution to recover acidic slurries
containing the precipitated metal, on the one hand, and
a filtrate with a reduced content of metal, on the
other hand.
Thus, the process of the invention is carried out continuously and is based essentially on a complexation of the metal contained in basic effluents, which is performed under specific pH conditions, while at the same time monitoring the progress of a precipitation reaction.

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Surprisingly, this precipitation reaction is carried out at a very acidic pH, since it is between 0 and 4, while at the same time monitoring the progress of the precipitation reaction. Decantation and filtration of the resulting solution gives, on the one hand, slurries which contain the precipitated metal and which can be incinerated, and, on the other hand, a filtrate with a substantially reduced content of metal, which can be discharged into a river.
This process thus differs from the prior art in that the precipitation reaction proceeds at a very acidic pH, rather than at a more or less neutral pH. As a result, small amounts of complexing agent can be used relative to the amount of solution to be treated.
The strong acid used in step b) is advantageously sulphuric acid.
In steps b) and c) , the pH value is preferably more or less equal to 3.
In step d), the complexing agent is advantageously a carbamate derivative, in particular sodium dimethyldithiocarbamate.
According to another characteristic of the invention, the monitoring of the precipitation reaction in step d) comprises monitoring the electrical potential of the solution, and the addition of the complexing agent is carried out for as long as the electrical potential measured has not reached a chosen value.
The monitoring of the electrical potential is preferably carried out with the aid of a redox electrode pf the Ag/AgCl type, while the value chosen corresponds to an electrical potential of between 150 and 300 mV;
According to another characteristic of the invention, the decantation in step d) is carried out in the presence of an agent which promotes decantation, in particular ferric chloride.
In step e) , the filtration is preferably carried out with the aid of a filter press.

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In one preferred application of the invention, the basic effluents in step a) comprise basic effluents originating from an organic synthesis, as a mixture with a basic filtrate resulting from a process for propessing acidic effluents.
In particular, the basic effluents in step a) advantageously Originate from a reaction for synthesizing a pigment, in particular a metal phthalo-cyanin.
The basic filtrate advantageously originates from a process for flocculating acidic effluents, leading to the production of basic slurries and the said filtrate.
These basic effluents can originate from a reaction for synthesizing a pigment, in particular a metal phthalocyanin.
Thus, the invention envisages processing both basic effluents and acidic effluents originating from the same reaction for synthesizing a pigment, in particular a metal phthalocyanin.
It is thus possible to process these two effluents separately in order to reduce the metal content thereof, instead of processing them together after mixing, as in the previous technique.
The invention applies in particular to a process in which the metal to be removed is chosen from iron, cobalt, nickel and corjper.
In the description which, follows, given purely by way of example, reference is made to the attached accompanying drawings, in which:
- Figure 1 is a flow diagram of a plant for removing a
metal contained in acidic effluents originating from an
organic synthesis of phthalocyain-based pigments, this
plant using a process according to the invention;
- Figure 2 is a diagram of a plant for removing metal
contained in basic effluents originating from the same
process for synthesizing phthalocyanin-based pigments,
this plant using a process according to the invention.

- 5 -
The process according to the invention will be explained in the particular case of processing acidic effluents and basic effluents originating from a process for synthesizing phthalocyanin-based pigments, also referred to as phthalocyanin blue, i.e. a phthalo-cyanin of a metal chosen essentially from iron, cobalt, nickel and copper.
In the example attention will be focused on copper phthalocyanin.
The diagram in Figure 1 shows a tank 1 for containing acidic effluents originating from the synthesis of pigments of the abovementioned type and containing, in the example, a metal, namely copper.
The effluents originating from tank 1 are sent via a pump 2 through a heat exchanger 3 to cool them. Next, these effluents are sent successively into two tanks 4 and 5 in which they are kept stirring and are neutralized by addition of a strong base, sodium hydroxide in the example, until a pH = 8 is obtained. In the example, the strong base is 30% sodium hydroxide originating from storage tanks 22 and 23 and sent, respectively, via pumps 24 and 25.
The effluents at pH 8 are introduced into a flocculation tank 6, which is kept stirring, into which is introduced a flocculant originating from a preparation station 7 and sent by means of a pump 8.
In the example, an aqueous solution of a flocculant polymer at 1 g/1 is used. The flocculant used is the product known under the brand name Praestol 2540 from the company Stockhausen. About 1 ml of this solution of flocculant is added to 1 litre of effluent, which gives a suspension that is sent to a decantation vat 9. This makes it possible to recover, on the one hand, slurries (line 10) and, on the other hand, a basic filtrate (line 11). The slurries are sent via a pump 12 into a thickener 13 which also receives ferric chloride originating from a container 14 and sent via a pump 15. These slurries are then sent via a pump 16 to a filter press 17 and from there are

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recovered in a skip 18 in order then to be sent to an incineration factory.
A basic filtrate is recovered from the filter press 17 and sent to a homogenization tank 29, which is described later with reference to Figure 2.
Mother liquors are recovered at the filter press outlet and are sent via a line 19 to a recovery tank 20. These liquors are recovered and sent via a pump 21 to the tank 4.
Thus, the plant represented in Figure 1 makes it possible to remove the metal (copper in the example) contained in the acidic effluents, producing, on the one hand, slurries which can be incinerated, and, on

the other hand, a filtrate (line 11) which is basic and which still contains metal. This filtrate is also used as starting material in the plant in Figure 2.
Reference is now made to Figure 2 to describe the plant for processing the basic effluents.
The basic effluents originating from the same process for synthesizing phthalocyanin-based pigments are sent to a tank 26, from where they are taken by means of a pump 27 and sent to a heat exchanger 28 to cool them. Next, these effluents are sent to a homogenization tank 29 which also receives the basic filtrates from the plant in Figure 1. The tank 29 is kept stirring to bring about mixing of the basic effluents and the basic filtrates. The pH of the mixture contained in tank 29 is generally between 10 and 12.
The mixture thus homogenized is sent to a tank 30 which is kept stirring and into which is introduced an insolubilizing agent, also referred to as a complexing agent, originating from a storage station 31 and sent via a line 32 by means of a pump 33. In the example, a complexing agent of the carbamate type is used, and advantageously sodium dimethyldithiocarbamate. A strong acid is also added to the tank 30, in the example 98% sulphuric acid, originating from a storage tank 34 and sent via a

- 7 -
pump 35 through a recycling loop 36 which returns to the storage tank 34.
It is essential for the pH of the solution
contained in the tank 30 to be adjusted and maintained
at an acidic value of between 0 and 4, and preferably
substantially equal to 3. To do this, a regulation is
carried out on the addition of the sulphuric acid in
order to keep this pH constant.
This results in a precipitation reaction of the metal, the progress of which reaction is monitored by suitable means.
In the example, the electrical potential of the solution is measured using a redox electrode of the Ag/AgCl type, and this complexing agent is added until a potential whose value is chosen as a function of the amount of copper to be complexed is obtained. This value is generally between 150 and 300 mV. As soon as the potential measured reaches this chosen value, the addition of the complexing agent is stopped.
An insoluble complex is thus formed in a flocculation tank 37 kept stirring.
After flocculation, the solution is sent to a decantation vat 38, thereby allowing the recovery of slurries, which are sent via a pump 39 to a slurry thickener 40. Moreover, effluents with a reduced content of metal are recovered at the outlet of the decantation vat 38 and sent to a recovery tank 41 which feeds a sand filter 42 via a pump 43.
Decantation liquors are also recovered at the outlet of the decantation vat 38 and are sent via a line 44 to the tank 20 described previously with reference to Figure 1.
A slurry suspension is recovered at the base of the slurry thickener 40 and is sent via a pump 45 to the filter press 17 in Figure 1.
The slurry thickener 40 also receives ferric chloride originating from a storage tank 46 and sent via a pump 47. A supernatant is also drawn from the

- 8 -
slurry thickener 40 and is recycled via a line 48 into the flocculation tank 37.
Filtered effluents are drawn from the sand filter 42 and are sent into a tank 49. From there, these filtered effluents are sent via two pumps 50 and 51 to an industrial effluent purification plant 52.
Thus, the process of the invention makes it possible to process both acidic effluents via the plant in Figure 1 and basic effluents via the plant in Figure 2, these two types of effluent originating from the same synthetic reaction. The plant in Figure 2 thus processes the basic effluents which have been mixed with the basic filtrates originating from the plant in Figure 1.
In one embodiment, acidic effluents of a volume of 100 to 200 m3 per day with a copper content of from 300 to 500 mg/litre, thus representing 45 to 100 kg of copper per day, are processed. The pH of these acidic effluents is 0.5.
By this same process, basic effluents representing a volume of from 50 to 75 m3 per day, with a copper content of from 30 to 50 mg/litre, which represents from 1.5 to 3.75 kg of copper per day, are processed. The pH of these basic effluents is 12.
After processing by the process of the invention, a filtrate is recovered in a volume of from 150 to 275 m3 per day with a copper content of less than 0.2 mg/litre and having a pH more or less equal to 3.
The invention will now be described with reference to two examples concerning a process for removing copper from industrial effluents resulting from the synthesis of pigments derived from copper phthalocyanin. These effluents are the result of a purification and a pigmentation of raw copper phthalocyanin. The effluents to be treated are basic and/or acidic effluents.

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Example 1: Processing for 1 litre of acidic effluents containing soluble copper
An aqueous solution (A) of a flocculant polymer at a concentration of 1 gram per litre is prepared.
The acidic effluents to be processed, which contain soluble copper at a concentration of 300 to 500 milligrams/litre, are placed under stirring. The pH of these effluents may be between 0 and 6.
In a first operation, the required amount of a strong base (for example sodium hydroxide) is added until a pH of 8 is obtained {the optimum pH may be between 7 and 9 depending on the case to be processed). A blue- to green-coloured colloid then forms, due mainly to the formation of copper hydroxide Cu (OH)2. To promote the decantation of the copper hydroxide, 1 millilitre of solution (A) is added per litre of acidic effluents to be processed. After decantation, the copper hydroxide precipitate is filtered off. When the filtration is carried out under pressure, copper slurries with a solids content of about 50% by weight are obtained. The degree of removal of copper from the acidic effluents after this operation is about 90%. To remove the remaining 10% of soluble copper, the process is performed as follows.
From the first operation, about 900 ml of an effluent at pH 8 (the pH may be between 7 and 9 depending on the case to be processed) containing from 30 to 50 milligrams per litre of soluble copper are recovered.
To process the 900 ml of effluents resulting from the processing of the first operation, the potential of the solution is monitored with a redox electrode. The solution to be processed is acidified to an optimum pH of 3 (the pH may be between 0 and 4 depending on the case under consideration) using a strong acid, for example hydrochloric acid. If the redox electrode is an electrode of the Ag/AgCl type, a metal-complexing agent (such as sodium dimethyldithio-carbamate) is added at pH 3 until an optimum potential

- 10 -
of about 230 mV is obtained. The addition of the complexing agent depends on the redox potential measured; the amount of complexing agent added depends on the concentration of soluble copper and on the type of copper complexes present in solution.
A brown-coloured copper precipitate forms. To assist the decantation of this precipitate, a coagulant such as FeCl3 can be used. After decantation and filtration, a filtrate and copper slurries are recovered. The filtrate contains only 0.2 milligram per litre of soluble copper. If the filtration is carried out under pressure, the copper slurries have a solids content which can be up to 50% by weight.
Example 2: Processing for 1 litre of acidic effluents and 1 litre of basic effluents both containing soluble copper
The process is performed as in Example 1.
From the first operation, about 900 ml of an effluent (B) at pH 8 (the pH may be between 7 and 9 depending on the case to be processed) containing from 30 to 50 milligrams per litre of soluble copper are recovered.
The 900 ml of effluent (B) are mixed with 1 litre of basic effluents (C) at pH 12 (the pH may be between 8 and 13) containing from 10 to 70 milligrams per litre of soluble copper. The proportion between the volumes of the effluents (B) and (C) may be different from that mentioned in the example.
To process the mixture of effluents (B) and (C), the potential of the solution is monitored with a redox electrode. The solution to be processed is acidified to an optimum pH of 3 (the pH may be between 0 and 4 depending on the case under consideration) using a strong acid, for example hydrochloric acid. If the redox electrode is an electrode of the Ag/AgCl type, a metal-complexing agent (such as sodium dimethyldithiocarbamate) is added at pH 3 until an optimum potential of about 230 mV is obtained. The

- 11 -
addition of the complexing agent depends on the redox potential measured; the amount of complexing agent added depends on the concentration of soluble copper and on the type of copper complexes present in solution.
A brown-coloured copper precipitate forms. To assist the decantation of this precipitate, a coagulant such as FeCl3 can be used. After decantation and filtration, a filtrate and copper slurries are recovered. The filtrate contains only 0.2 milligram per litre of soluble copper. If the filtration is carried out under pressure, the copper slurries have a solids content which may be up to 50% by weight.
Needless to say, the invention is not limited to the examples and embodiments described above but extends to other variants.
Thus, although the invention has been described with particular reference to the removal of a metal in pigments of phthalocyanin type, it can be applied to the removal of a metal in other industrial effluents.

WECLAMIE - 12-
1. Process for removing a soluble metal contained
in acidic and/or basic effluents originating from an
organic synthesis, in particular of pigments,
characterized in that it comprises the following steps
carried out continuously:
a) providing basic effluents containing the metal;Sach as herein described'
b) adding a strong acid such as herein described to the basic effluents until a
pH with a value of between 0 and 4 is obtained;
c) maintaining the pH at this value;
such as herein describedd) adding a complexing agent to such as herein described precipitate the metal,
while monitoring the progress of the precipitation reaction and allowing the resulting solution to decant; and
e) filtering the solution to recover acidic slurries
containing the precipitated metal, on the one hand, and
a filtrate with a reduced content of metal, on the
other hand.
2. Process according to Claim 1, characterized in
that the strong acid used in step b) is sulphuric acid.
3. Process according to either of Claims 1 and 2,
characterized in that, in steps b) and c), the pH value
is more or less equal to 3.
4. Process according to one of Claims 1 to 3,
characterized in that the complexing agent added in
step d) is a carbamate derivative.
5. Process according to Claim 4, characterized in
that the complexing agent is sodium dimethyldithio-
carbamate.
6. Process according to one of Claims 1 to 5,
characterized in that the monitoring of the
precipitation reaction in step d) comprises monitoring
the electrical potential of the solution, and in that
the complexing agent is added for as long as the
electrical potential measured has not reached a chosen
value.
7. Process according to Claim 6, characterized in
that the monitoring of the electrical potential in

- 13 -
step d) is carried out by means of a redox electrode of the Ag/AgCl type and in that the value chosen corresponds to an electrical potential of between 150 and 300 mV.
8. Process according to one of Claims 1 to 7,
characterized in that the decantation in step d) is
carried out in the presence of an agent which promotes
decantation, in particular ferric chloride.
9. Process according to one of Claims 1 to 8,
characterized in that the filtration in step e) is
carried out by means of a filter press.
10. Process according to one of Claims 1 to 9,
characterized in that the basic effluents in step a)
comprise basic effluents originating from an organic
synthesis as a mixture with a basic filtrate resulting
from a process for processing acidic effluents.
11. Process according to Claims 1 to 8,
characterized in that the basic effluents in step a)
originate from a reaction for synthesizing a pigment,
in particular a metal phthalocyanin.
12. Process according to either of Claims 10 and
11, characterized in that the basic filtrate originates
from a process for flocculating acidic effluents,
leading to the production of basic slurries and the
said basic filtrate.
13. Process according to one of Claims 10 to 12,
characterized in that the acidic effluents originate
from a reaction for synthesizing a pigment, in
particular a metal phthalocyanin.
14. Process according to Claims 11 and 13, taken in
combination, characterized in that the basic effluents
and the acidic effluents originate from the same
reaction for synthesizing a pigment, in particular a
metal phthalocyanin such as herein described.
15. Process according to one of Claims 1 to 14,
characterized in that the metal to be removed is chosen
from iron, cobalt, nickel and copper.

Process for removing a soluble metal contained in acidic and/or basic effluents originating from organic
syntheses
The process of the invention for removing a soluble metal comprises the following steps carried out continuously: a) providing basic effluents containing the metal; b) adding a strong acid to the basic effluents until a pH with a value of between 0 and 4 is obtained; c) maintaining the pH at this value; d) adding a complexing agent to precipitate the metal, while monitoring the progress of the precipitation reaction and allowing the resulting solution to decant; and e) filtering the solution to recover acidic slurries containing the precipitated metal, on the one hand, and a filtrate with a reduced content of metal, on the other hand. Application in particular to the processing of phthalocyanin-based pigments.

Documents:

00246-cal-2000 abstract.pdf

00246-cal-2000 claims.pdf

00246-cal-2000 correspondence.pdf

00246-cal-2000 description(complete).pdf

00246-cal-2000 drawings.pdf

00246-cal-2000 form-1.pdf

00246-cal-2000 form-18.pdf

00246-cal-2000 form-2.pdf

00246-cal-2000 form-3.pdf

00246-cal-2000 form-5.pdf

00246-cal-2000 letters patent.pdf

00246-cal-2000 p.a.pdf

00246-cal-2000 priority document others.pdf

00246-cal-2000 priority document.pdf

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Patent Number

202632

Indian Patent Application Number

246/CAL/2000

PG Journal Number

10/2007

Publication Date

09-Mar-2007

Grant Date

09-Mar-2007

Date of Filing

25-Apr-2000

Name of Patentee

FRANCOLOR PIGMENTS

Applicant Address

B.P 25, F-60870 RIEUX

Inventors:

#	Inventor's Name	Inventor's Address
1	NAHON KAREN	12 AVENUE GEORGES CLEMENCEAU , F-94300 VINCENNES
2	COISPEAU GERARD,	13 RUE VINCELOT, F-27400 LOUVIERS

PCT International Classification Number

C 02 F 1/62

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	9905790	1999-05-06	France