Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B7/00—Halogens; Halogen acids
  • C01B7/13—Iodine; Hydrogen iodide
  • C01B7/14—Iodine
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
  • C07C51/347—Preparation of carboxylic acids or their salts, halides or anhydrides by reactions not involving formation of carboxyl groups
  • C07C51/377—Preparation of carboxylic acids or their salts, halides or anhydrides by reactions not involving formation of carboxyl groups by splitting-off hydrogen or functional groups; by hydrogenolysis of functional groups
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B2210/00—Purification or separation of specific gases
  • C01B2210/0001—Separation or purification processing
  • C01B2210/0003—Chemical processing
  • C01B2210/0004—Chemical processing by oxidation
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B2210/00—Purification or separation of specific gases
  • C01B2210/0043—Impurity removed
  • C01B2210/0068—Organic compounds
  • C01B2210/007—Hydrocarbons

Definitions

• the present invention relates to a process for recovering iodine from aqueous solutions containing organic iodine, in particular iodine-containing aromatic compounds.
• Radiographic contrast agents are characterized by comprising a three-iodinated aromatic ring.
• contrast agents and of their intermediates, generates mother liquors and wastewaters containing iodine that, depending on the process, can be present both in an inorganic form at different oxidation states (i.e. as free ions or incorporated into inorganic compounds), or in an organic form (i.e. incorporated in organic compounds).
• a key step for an efficient recovery of the iodine is the removal of the organic iodine incorporated in iodine-containing aromatic compounds, typically iodinated contrast agents and intermediates thereof, and its conversion into molecular iodine that is then recovered.
• EP0106934 discloses a mineralization method for converting iodine contained in organic compounds into iodide in the presence of copper ions or finely dispersed copper. The recovery of the iodine is then carried out by acidification of the mineralized solution, oxidation of the formed iodide and recovery of elemental iodine.
• EP1133346 proposes an improvement of the above process that comprises operating a thermal concentration of mother liquors or wastewater during the mineralization allowing to remove organic solvents, and purifying the concentrated solution by nanofiltration before the oxidative step.
• CN103508421 discloses an alternative iodine recovery procedure in which the conversion (specifically alkaline reduction) of the iodine contained in organic compounds into iodide ions is carried out under reflux at alkaline conditions (pH at least 12), in the presence of a reducing substance selected from copper powder, magnesium powder, zinc powder, iron powder and mixtures thereof.
• alkaline conditions pH at least 12
• a reducing substance selected from copper powder, magnesium powder, zinc powder, iron powder and mixtures thereof.
• a composite H 2 02-FeCl3 oxidizing agent is then exploited to convert iodide ions into molecular iodine, which is then separated by filtration.
• CN105460896 discloses a multi-step method for the recovering of iodine from production wastes in which the iodine contained in organic compounds is converted into molecular iodine or iodide ions under acidic conditions, by using an oxidizing mixture selected from C/Fe 2+ and Fe/Fe 3+ (oxidizing conversion).
• the present invention generally relates to a process for the treatment of aqueous solutions comprising iodine-containing (briefly “iodinated”) aromatic compounds, wherein the iodine contained in said aromatic compounds (hereinafter "organic iodine”) is directly converted into molecular iodine and recovered.
• the present invention relates to a process for recovering molecular iodine from an aqueous solution comprising a iodine-containing aromatic compound and a iodine-containing inorganic compound, said process comprising the steps of:
• step A wherein the pH of the aqueous solution comprising the iodine-containing aromatic compound undergoing the conversion of step A is 1 or lower.
• the present invention relates to a process as defined above wherein the pH of the aqueous solution is 0.5 or lower, e.g. from 0.01 to 0.3.
• the reaction temperature is preferably of at least 80°C or higher, more preferably of at least 90°C or higher, even more preferably of 100°C or higher; the temperature is preferably lower than 300 °C and, more preferably, lower than
• step A is carried out by heating the aqueous solution at a temperature of from 80°C to 300°C, preferably of from 90°C to 200°C, and more preferably of from 100°C to 150°C.
• step A of the iodine contained in the aromatic compound into molecular iodine is efficiently carried out in the absence of a catalyst.
• the conversion is preferably carried out in the presence of inorganic anions, e.g. including halides, sulfates or nitrates.
• Preferred aqueous solutions (to be treated) further comprise iodide ions.
• the invention relates to a process for the treatment and the recovery of iodine from aqueous solutions containing iodinated aromatic compounds in which the iodine incorporated in these compounds is converted into molecular iodine at a pH lower than 1, in the absence of a catalyst.
• the invention relates to a process for the treatment and the recovery of iodine from aqueous liquors of industrial processes for the manufacturing of radiographic contrast agents or iodinated intermediates thereof.
• iodine-containing aromatic compound refers to aromatic compounds, comprising at least one iodine atom linked to a carbon atom(s) thereof;
• organic iodine refers to iodine contained in organic, preferably aromatic, compounds, typically covalently linked to the carbon atom(s) thereof;
• iodine-containing inorganic compound refers to iodine contained in inorganic compounds, such as inorganic acids or salts, including iodide ions;
• iodide or "iodide ions” refers to iodine with oxidation number -1, i.e. as ion , which may be combined with a proton or with any other positive counterion, generally in dissociated form when in aqueous solution;
• inorganic iodine refers to iodine at different oxidation states, including iodine contained in inorganic compounds, such as inorganic acids or salts (e.g. iodic acid or iodate).
• the invention relates, in general, to a process for the treatment and the recovery of molecular iodine from an aqueous solution comprising a iodine- containing aromatic compound and a iodine-containing inorganic compound, said process comprising the steps of:
• step A wherein the pH of the aqueous solution comprising the iodinated aromatic compound undergoing the conversion of step A is 1 or lower.
• the step A of the process is carried out under acidic condition, as above discussed.
• Suitable conditions include a pH below 1 and, preferably, below 0.5. More preferably, the step A of the process is carried out with aqueous solutions having a pH below 0.3, e.g. about 0. If necessary, the pH of the solution to be treated may be suitably adjusted to these pH values, e.g. by addition of a (strong) acid, for instance selected from HCI, H 3 P0 4 , and 50% H 2 S0 4 .
• a (strong) acid for instance selected from HCI, H 3 P0 4 , and 50% H 2 S0 4 .
• the reaction is preferably operated at a temperature above 80°C; for instance of from 80°C and 300 °C and, more preferably, from 90°C to 200°C.
• step A of the process is carried out at a temperature ranging from 100°C to 150°C, e.g. about 140°C-150°C.
• the step A of the process comprises operating a conversion of iodine contained in an aromatic compound directly into molecular iodine, that is carried out by heating aqueous solutions having pH below 1 and, preferably below 0.5, at a temperature above 90°C, and, preferably, of from 100°C to 150°C, e.g. of about 140°C-150°C.
• the direct conversion of the iodine contained in aromatic compounds into molecular iodine is, in particular, a hydrodeiodination reaction.
• hydrodeiodination (or “protodeiodination”) comprises within its meaning a reaction in which a iodine atom linked to a carbon atom of an aromatic ring is replaced by a hydrogen atom.
• Aqueous solutions to be subjected to the hydrodeiodination include a iodine- containing aromatic compound.
• concentration of the aromatic compounds in the solution is, preferably, of at least 0.01 mg/g and preferably ranges e.g. from 0.1 mg/g to 20 mg/g.
• the aqueous solution subjected to the hydrodeiodination comprises iodine-containing aromatic compounds and iodide ions.
• Suitable examples of these solutions include, for instance, aqueous liquors coming from industrial processes for the manufacturing of iodinated contrast agents, especially of non-ionic x-ray contrast agents, that typically have pH below 1 and comprise:
• aqueous liquors may further comprise:
• inorganic iodine other than iodides or molecular iodine; • non-iodinated organic compounds;
• non-iodinated inorganic anions such as chlorides, sulfates, phosphates, and so on.
• the weight ratio iodide : organic iodine (i.e. the amount by weight of iodide ion vs. the amount by weight of iodine incorporated into aromatic compounds) in solution is of at least 0.5 or higher.
• the ratio is of at least 1 or higher, and, even more preferably, at least 2 or higher, up to e.g. 10.
• this conversion is achieved in the absence of a dehalogenation or conversion catalyst.
• step A the hydrodeiodination reaction of step A is carried out at atmospheric pressure and temperatures below 100°C.
• the step A is operated at higher temperatures, e.g. above 100°C.
• suitable equipments are exploited, allowing to reach reaction temperatures of about 140°C-150°C, for example comprising a tank where the upper end opens with an outer flange to the body of the tank, allowing to operate the hydrodeiodination reaction at a pressure higher than atmospheric pressure, speeding the completion of the hydrodeiodination reaction.
• the operative pressure may for instance vary from 1 atm to 85 atm , preferably from 1 atm to 15 atm, more preferably from 1 atm to 5 atm, e.g. of about 3.5 bar.
• reaction times enabling for a complete conversion of a iodine- containing aromatic compound within liquors to molecular iodine will depend on iodide ion content and on the hydrodeiodination conditions, e.g. including reaction temperature and solution pH .
• hydrodeiodination is carried out with aqueous solutions having high iodide ion content, e.g. at least equal (by weight) to the content of organic iodine, and pH below 0.5, e.g.
• a conversion of the organic iodine into molecular iodine of at least 90% (w/w), more preferably of 95% (w/w) and, most preferably, of 97% (w/w) or even more (with respect to the iodine amount comprised in the aromatic compounds of the original starting solution) is achieved in less than 3 hours, for instance in a time ranging from 20 min to 120 min, and, preferably from 20 min to 60 min.
• step A of the process is carried out at a lower temperature, e.g. of about 100°C
• an analogous conversion is achieved in a time e.g. of from 20 to 50 hours, preferably from 20 to 30 hours, and more preferably of about 25 hours.
• step B After (or during) the hydrodeiodination of step A has occurred, the remaining aqueous solution is processed according to step B to collect the formed molecular iodine, optionally after having oxidized the residual inorganic iodine through step A'.
• the molecular iodine formed during step A of the process is directly removed (at least in part) by sublimation from the reaction environment (e.g. in a continuous manner), with formation of a vapor stream of pure iodine that is then collected e.g. in a separate device, according to step B of the process.
• the molecular iodine produced during step A may remain in the aqueous solution inside the reactor until completion of the reaction, where it precipitates (e.g. after cooling) and is then removed by filtration.
• step A the process further comprises an optional step A', including the oxidation of possible residual iodide ions into molecular iodine.
• the optional step A' may advantageously be carried out to treat aqueous solutions rich of iodides, e.g. in which the ratio iodides : organic iodine (in solution) is above 0.5, preferably above 1.
• the oxidation of step A' is carried out under acidic conditions, e.g. by addition of an oxidizing agent to the acidic solutions resulting from step A.
• the oxidizing agent is added to the acidic solutions collected from step A, converting possible residual iodide ions within liquors to molecular iodine.
• the oxidizing agent may be added directly into the reactor in which the hydrodehalogenation occurs, once it is finished.
• Suitable oxidizing agents are for instance selected from the group consisting of hypochlorite, chlorate, chlorine (gas), nitrite and hydrogen peroxide, the latter being particularly preferred.
• the oxidizing agent e.g. hydrogen peroxide (H2O2)
• H2O2 is added, for instance portionwise, to the acidic solution collected from step A, in a time of from 30 to 120 min, and, preferably, from 50 to 70 min., e.g. of about 60 min, until the redox potential of the mixture reaches 600 mV (see, for instance, D. R. Lide, CRC Handbook of Chemistry and Physics, ed. 83 rd , 2002 CRC Press LLC, from pag . 8-21 to pag. 8- 23).
• H2O2 hydrogen peroxide
• the H2O2 is added to the solution collected from step A previously cooled, e.g. to a temperature below 50°C, preferably of from 20°C to 40°C and, more preferably of from 20°C to 30°C, e.g. at room temperature, thereby promoting the precipitation of the molecular iodine formed by oxidation of iodides, which is then collected by filtration, according to step B of the process.
• the step A' of the process comprises a portionwise addition of H2O2 directly to acidic liquors resulting from step A, maintained under stirring in the same reactor at a temperature of about 100°C.
• the molecular iodine formed at step A, and, optionally, at step A', is suitably removed from hot liquors by sublimation, with formation of a vapor stream of pure iodine that is then collected e.g. in a separate device, according to step B of the process.
• the step B of the process comprises removing the iodine formed during steps A and/or A' of the process by sublimation, e.g. in a vapor stream, and collecting the sublimed iodine in separate containers.
• the iodine produced during step A may remain in such reactor until optional step A' starts.
• the vapor stream containing iodine is conveyed and collected in an adsorption liquid, e.g. an organic solvent or, preferably, in alkali, e.g. 30% sodium hydroxide (NaOH), in which I 2 disproportionates into iodate (I +5 ) and iodide ( ⁇ 1 ) ions.
• an adsorption liquid e.g. an organic solvent or, preferably, in alkali, e.g. 30% sodium hydroxide (NaOH), in which I 2 disproportionates into iodate (I +5 ) and iodide ( ⁇ 1 ) ions.
• alkali e.g. 30% sodium hydroxide (NaOH)
• NaOH sodium hydroxide
• I2 sulfuric acid
• an aqueous solution with variable (generally decreasing from A to B) amounts of residual organic, inorganic and/or molecular iodine is obtained.
• the process of the invention further comprises an additional step C for recovering optional residual traces of organic iodine, inorganic iodine and/or molecular iodine. Residual traces of organic iodine may for instance derive from an incomplete deiodination at step A of the process, for example carried out at a temperature or for a time lower than optimal, or with waste not sufficiently acid, or particularly poor of iodides.
• Residual traces of molecular iodine may otherwise derive from an incomplete recovery in step B, for example carried out by precipitation and filtration from an aqueous solution in which the molecular iodine has a (even reduced) solubility, or caused by an incomplete sublimation from the aqueous solution.
• Step C is, for instance, carried out by feeding the aqueous liquors deriving from step B, i.e. that remain after removal and collection of the iodine formed in steps A and/or A', into one or more columns loaded with absorbent material, e.g. carbon or XAD resins. Residual traces of organic, inorganic and/or molecular iodine are first fixed on the column(s) and then desorbed, e.g. by use of suitable solvents or bases, to give a concentrated solution that can be recycled to step A of the process, or may alternatively be treated according to the known procedures, for instance as disclosed in EP0106934.
• absorbent material e.g. carbon or XAD resins
• step C of the above process preferably comprises:
• a solvent or base for example NaOH 30%
• step A of the process optionally after acidification to the above values; or, alternatively
• step ii) subjecting the basic solutions collected at step ii) to a mineralization e.g. as disclosed in EP0106934, converting organic iodine into iodides that are recycled to step A or step A' of the process, or directly oxidized to molecular iodine that is then collected by filtration or sublimation, as above said.
• a mineralization e.g. as disclosed in EP0106934, converting organic iodine into iodides that are recycled to step A or step A' of the process, or directly oxidized to molecular iodine that is then collected by filtration or sublimation, as above said.
• Molecular iodine (I2) from step ii) above is typically disproportionated into iodate (I +5 ) and iodide ( ⁇ 1 ) ions.
• the process of the invention comprises:
• the above process comprehensive of any variant thereof, is of general use, and allows to efficiently treat solutions (particularly industrial liquors) containing iodine under different forms (e.g. organic iodine in a mixture with iodides, molecular and/or inorganic iodine as defined above).
• the process provides a substantially quantitative recovery of the total iodine content, independently on the concentration of each iodine form, with collection of exhausted wastes substantially free from iodine, that can be discharged .
• optional traces of inorganic iodine at oxidation state above 1 may typically be converted into molecular iodine.
• the absorption/desorption step C allows an efficient recovery of the organic iodine present in diluted solutions without application of any concentration treatment, such as thermal concentration. Since thermal concentration is highly energy demanding, its elimination is particularly advantageous in processes applied on a large industrial scale.
• the process of the invention allows to efficiently treat strongly acidic liquors, e.g . directly collected from industrial manufacturing process of radiographic agent intermediates, which typically comprise high iodides content, promoting an exhaustive conversion of organic iodine within liquors into molecular iodine directly in step A, with a substantially quantitative recovery of the total iodine, from steps A and A' of the process, as shown, for instance, with tests of examples 1 and 9.
• step A oxidizing a possible resid ual iodide ion into molecular iodine by adding an oxidizing agent to the solution of step A;
• the above process may be carried out as above widely discussed, by implementing the steps A to C in the provided order, where the hydrodeiodination of iodinated aromatic compounds according to the step A precedes the oxidation of residual iodides carried out according to step A', optionally directly in the same reactor, with formation of molecular iodine which is collected according to step B, and the remaining solution is optionally subjected to the recovery of optional residues of organic iodine and/or molecular iodine according to step C of the proposed procedure.
• the process of the invention may be carried out without including step A'.
• the step C comprising the recovery of any residual organic or molecular iodine is carried out directly after the recovery of iodine formed in step A of the process, carried out (this latter) according to step B.
• step B may start before the respective termination of these steps.
• the step C of the process may precede the step A', thereby removing residual organic iodine from the solution obtained at step A.
• the subsequent oxidation of the iodides may conveniently be carried out at lower temperatures, e.g. at room temperature, by leading to the precipitation of molecular iodine that is filtered and optionally further purified according to known procedures.
• the process of the invention finds efficient use in the treatment of liquids collected from industrial processes for the preparation of x- ray contrast agents and iodinated intermediates thereof, including iodinated or partially iodinated derivatives of benzene mono or dicarboxylic acids or aminobenzene mono- or di-carboxylic acids (e.g. mono-, di- and triiodinated derivatives of aminobenzenedicarboxylic acids).
• These manufacturing processes include, as a common step, the iodination of an aromatic substrate, more typically the 5-amino-l,3-benzenedicarboxylic acid, e.g. carried out as disclosed in W096/37458.
• the manufacturing processes of radiographic contrast agents may comprise the iodination of ⁇ , ⁇ '-bis-amides of the 5-amino-l,3- benzenedicarboxylic acid, e.g. compounds of formula (I)
• Ri is a C1-C3 alkyl substituted by one or more hydroxyl groups
• Ri is a propanediol, e.g. 1,3-propanediol, and R2 is H .
• Mother liquors directly collected from above iodination processes include, as such, optimal acidic conditions, namely pH below 1 and typically below 0.5, significant amounts of unreacted iodides, and iodinated, or partially iodinated, aromatic compounds (e.g. mono-, di- and triiodinated derivatives of 5-amino-l,3- benzenedicarboxylic acids).
• liquors may thus efficiently be treated with the process of the invention as such, namely without requiring any thermal concentration or addition of acids or optional additional reactants, by leading to an overall iodine recovery yield e.g. exceeding 95%, preferably of from 96 to 100%, more preferably from 97 to 100 % and most preferably of from 98 to 100%, e.g. of from 98 to 99% directly at step B.
• an overall iodine recovery yield e.g. exceeding 95%, preferably of from 96 to 100%, more preferably from 97 to 100 % and most preferably of from 98 to 100%, e.g. of from 98 to 99% directly at step B.
• the invention relates to a process for the treatment and the recovery of the iodine from liquors directly collected from the industrial iodination processes for the manufacturing of a radiographic intermediate selected from the group consisting of 5-amino-2,4,6-triiodo-l,3-benzenedicarboxylic acid and 1,3-benzendicarboxamides thereof of the above formula (I).
• the process comprises the recovery and recycling of iodine from aqueous liquors collected from the industrial process for the manufacturing of 5-amino-2,4,6-triiodo-l,3-benzenedicarboxylic acid.
• compositions thereof essentially comprising organic iodine as mono-, di- and triiodinated derivatives of 5-amino-l,3-benzendicarboxylic acid, or of a 1,3- benzendicarboxamides of this same, and iodides.
• Step A HYDRODEIODINATION
• the mixture was heated to 100°C and kept under stirring for about 24 h : hydrodeiodination occurred with formation of purple vapors of molecular iodine, that were collected by absorption in the trap containing sodium hydroxide.
• Iodine collected in the trap corresponded to about 31.6% of the initial total iodine content.
• the resulting mixture was further stirred at the same temperature for 1 h to complete the reaction and the iodine sublimation and then cooled to room temperature in 80 min.
• the exhausted solution (0.926 kg) contained a residual amount of iodides (0.08 g) and organic iodine (0.055 g).
• step A' the iodine collected in the trap corresponded to an overall recovery yield of 98.8%.
• Step A HYDRODEIODINATION
• Iodine collected in the trap corresponded to about 48% of the initial total iodine content.
• step A' iodine collected in the trap corresponded to an overall recovery yield of 96.0%.
• Step C TREATMENT ON CARBON COLUMN
• the solution was loaded on a carbon column, charged with 30.5 g of dry carbon (equivalent to a bed of 80 ml. of wet carbon).
• the loading operation was performed at a flow rate of 3 BV/h and 60°C, heating both solution and carbon.
• the obtained solution (412 g) had organic iodine and iodides contents respectively of 5.24 g/kg and 0.56 g/kg and can be treated according to the prior art conditions described in EP106934 or recycled in step A.
• the carbon bed can be recycled and reused.
• Step A HYDRODEIODINATION
• the mixture was heated to 100 °C and kept under stirring for about 25 h : hydrodeiodination occurred with formation of purple molecular iodine vapors that were collected by absorption in the trap containing sodium hydroxide.
• Iodine collected in the trap corresponded to about 33% of the initial total iodine content.
• the resulting mixture was further stirred at the same temperature for 1 h to complete the reaction and the iodine sublimation and then cooled to room temperature in 60 min.
• the exhausted solution (3.563 kg) contained a residual amount of iodides/molecular iodine (0.07 g/kg) and organic iodine (0.15 g/kg).
• step A' iodine collected in the trap corresponded to an overall recovery yield of 97.4%.
• the experiment was done in a closed reactor, to test the impact on the conversion of a temperature higher than 100 ° C, about 140°C.
• the obtained solution was equally portioned in 10 ml. closed reactors and heated to 140 °C keeping under stirring.
• the test has been carried out to assess the effect of suboptimal hydrodeiodination temperatures.
• Step A HYDRODEIODINATION
• the mixture was heated to 100 °C and kept under stirring for about 25.5 h : hydrodeiodination occurred with formation of purple molecular iodine vapors that were collected by absorption in the trap containing sodium hydroxide.
• Iodine collected in the trap corresponded to about 67.8 % of the initial total iodine content.
• the resulting mixture was further stirred at the same temperature for 1.5 h to complete the reaction and the iodine sublimation and then cooled to room temperature in 60 min.
• the exhausted solution (866.95 g) contained only residual organic iodine (0.48 mg/g).
• step A' iodine collected in the trap corresponded to an overall recovery yield of 84.7%.
• the test comprises a partial hydrodeiodination, purportedly operated jointly with the oxidation step, to evaluate the effectiveness of step C) in compensating any suboptimal hydrodeiodination conditions
• PARTIAL HYDRODEIODINATION + OXIDATION 3.700 kg of a mother liquor solution, obtained from a iodination process e.g . disclosed in W096/37458, with pH ⁇ 0.1, containing 37.08 g of iodides and 7.32 g of organic iodine (mainly as mono-, di- and triiodinated derivatives of 5-amino- l,3- benzendicarboxylic acid) were loaded in a jacketed reactor, equipped with a mechanical stirrer and a thermometer and connected to a drechsel trap, filled with a 15% sodium hydroxide solution.
• a mother liquor solution obtained from a iodination process e.g . disclosed in W096/37458, with pH ⁇ 0.1, containing 37.08 g of iodides and 7.32 g of organic iodine (mainly as mono-, di- and triiodinated derivatives of 5-amino
• the solution was heated to 100 °C in about 1 h and then 5% aqueous hydrogen peroxide (approximately 95 g) was added keeping the mixture at 100°C; the addition was performed in 1 h until the redox potential of the mixture reached 600 mV: molecular iodine formed during the reaction sublimed and vapours were collected by absorption in the trap.
• the resulting mixture was further stirred at the same temperature for 1 h to complete the reaction and the iodine sublimation and then cooled to room temperature in 80 min.
• the exhausted solution (3.419 kg) contained a residual amount of iodides (0.53 g) and organic iodine (4.39 g).
• the loading was performed at 20-25°C with a flow rate of 2 BV/h and was stopped when the column Col2 started to release iodinated organic compounds (breakthrough point).
• the eluate (9.673 kg) from Col2 contained a residual amount of iodides (0.18 g/kg) and organic iodine (0.04 g/kg), corresponding to an overall iodine recovery of 98.5%.
• Step A HYDRODEIODINATION
• step A' is carried out as disclosed in Example 1. At the end of step A' iodine collected in the trap corresponded to an overall recovery yield of 99.0%.
• test exemplifies a process according to the invention that does not include step A'.

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