Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Reexamination Certificate
2001-07-17
2003-08-05
Fortuna, Ana (Department: 1723)
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
C210S651000, C423S019000, C423S486000, C423S502000
Reexamination Certificate
active
06602419
ABSTRACT:
DISCLOSURE
The present invention relates to a novel process for the recovery of iodine from solutions containing iodinated organic compounds, in particular non-ionic contrast agents.
The most modern contrast agents, i.e. the non-ionic ones, are usually 2,4,6-triiodo-1,3-benzenedicarboxylic acid derivatives, characterized by a strong bond of the iodine atoms to the aromatic ring. The strength of said bond is however also affected by the structure of the concerned compound.
Due to environmental reasons, the effluents should be completely free from iodinated organic compounds, while for economic reasons as much iodine as possible should be recovered, in that it is now rare and expensive. In this case, economic and environmental needs meet.
The problem has arisen for some time, as evidenced by a series of patents concerning this process (see for example: WO 98/07661; WO 94/10083; NO 9100001; EP 106934). In particular, EP 106934, filed in the Applicant' name in 1982, discloses the process for the mineralisation of iodine, which comprises heating the solutions of the contrast agents for 30 minutes-2 hours at 100-150° C. in a strong alkali excess in the presence of 100 to 2500 ppm of copper ions or of finely dispersed copper.
The recovery of iodine after mineralisation is carried out according to known methods, usually by oxidation of the formed iodide with mild means. The formed iodine is recovered and concentrated, for example, by extraction or by sublimation in air or vapour stream. Iodine can also be recovered from the extraction solvent (for example toluene) by treatment with aqueous alkali hydroxide, and the iodine vapours obtained in the sublimation can be collected, for example, through absorption in alkali hydroxide solutions by iodide-iodate dismutation.
Iodine is known to quantitatively regenerate from the alkali hydroxide solution by acidification following dismutation.
It can easily be evinced from EP 106934 (page 6, Table) that the temperature of the mineralisation process depends on the type of the contrast agent.
The conditions for the preparation of Iopamidol and Metrizamide, which then represented the novel class of non-ionic compounds (i.e. in which the carboxylic groups are in the form of amides with aminoalcohols), are more drastic than those for the ionic compounds, i.e. those having at least one acid group on the aromatic ring (acetrizoic, diatrizoic, iothalamic, iopronic, iopanoic acids, iodamide and adipiodone). For example, the best results are achieved when heating the 2% Iopamidol solution to 150° C. in the presence of 2500 ppm of copper ion.
The most diffused compounds are at present the non-ionic ones. The preparation thereof usually involves crystallizations from a solvent, usually alcoholic, both in the intermediate steps and the final one.
The presence of solvents in wastes from which iodine has to be recovered makes carring out the cited process more difficult, particularly in the following steps:
when the mineralisation process is carried out, according to the teaching of the Patent, at least at 100° C., it is difficult to reach said temperature due to the low-boiling organic solvent (such as a lower alcohol), unless operating under pressure;
the presence of the solvents, in particular alcohols, makes the precipitation of iodine after sublimation problematic, unless using a system of scrubber;
when using an alternative process for recovering the sublimated iodine (treatment with alkali and subsequent precipitation of iodine by acidification), side-formation of iodoform takes places due to the presence of compounds having RCOCH
3
/RCHOHCH
3
groups.
Said reaction, which has to be absolutely avoided for environmental reasons, also prevents the recovery of iodine due to the precipitation of iodoform.
finally, it is necessary to increase the amount of oxidizer necessary to oxidize the iodide formed after mineralisation.
A further technical problem which had not been evidenced in the above Patent is that, after the mineralisation step, phenol or quinone organic compounds are present which cause a consumption of oxidizer in the subsequent oxidation step and moreover have a high environmental impact, in that they are not biodegradable.
It has now surprisingly been found that the above cited problems can be solved by concentrating the solution obtained under the mineralisation conditions described in EP 106,934 and purifying said solution by nanofiltration before the oxidative step, thereby improving the overall yield of process.
It is therefore an object of the present invention a process for the recovery of iodine from mother liquors or wastes with a percentage of organic solvents at most of 95% (w/w), containing iodinated organic compounds, by mineralisation of organic iodine (in the presence of copper ions or finely dispersed metallic copper in alkali aqueous solution) and subsequent transformation of the formed iodide into elementary iodine, characterized in that the aqueous solution, after mineralisation, is concentrated under atmospheric pressure and at the boiling temperature and is subsequently subjected to nanofiltration.
The process is particularly suitable for the treatment of solutions of non-ionic iodinated contrast agents, such as: Iopamidol, Iohexol, Iopromide, Ioxilan, Iomeprol, Iopentol, Ioversol. The process of the invention can also be applied to ionic contrast agents, if the above stated conditions are fulfilled. In this case, aqueous or organic solvents solutions will be present, depending on compound or waste to be treated and on the synthetic step.
The solution is preferably adjusted to a volume ranging from 85% to 25% (w/w) of the starting volume. Said procedure is easily applicable to waste solutions from the synthesis of ionic or non-ionic contrast agents, possibly in the presence of solvents, and it allows to decrease the COD from values of 20.000-40.000 mg/L to 4.000-9.000 mg/L through demolition of the organic molecules present and removal of any solvents.
The conditions of the mineralisation process of the present invention are the same as those disclosed in EP 106,934.
The copper catalyst is added in amounts from 100 to 3000 ppm, preferably 500-1000 ppm, and pH is kept at 12 during the whole mineralisation step.
The process of the invention comprises heating the solution to be deiodinated at the boiling temperature and under atmospheric pressure.
This, of course, involves rather long times such as:
4 to 6 hours for mineralising a solution of Iopamidol, Iomeprol, Iohexol, Metrizamide or of a generic non-ionic contrast agent, in concentration of 2%-10% (w/w) with an at most 95% (w/w) content in alcoholic solvent;
2 to 3 hours for mineralising a solution of the mother liquors from the production of Iopamidol intermediates containing 3%-15% (w/w) of iodinated intermediate, with the following maximum contents (w/w): 2-butanol 20%, methylchloroform 5%, n-butyl acetate 4%, n-dodecane 3% (w/w) and tert-butanol 30%. As mentioned above, the process of the invention can also be used for mother liquors from production cycles of other ionic contrast agents such as:
3,5-acetylamino-2,4,6-triiodo-benzoic acid sodium salt (DIAC), acetrizoic acid (3-acetamino-2,4,6-triiodobenzoic acid);
adipione (3,3′-[(I,1,6-dioxo-1,6-hexanediyl)diimino]-bis-2,4,6-triiodobenzoic acid;
iodossamic acid (3,3′-[(1,16-dioxo-4,7,10,13-tetraoxahexadecane-1,16-diyl)diimino]-bis-2,4,6-triiodo benzoic acid;
iothalamic acid (3-(acetylamino)-2,4,6-triiodo-5-[(methylamino)carbonyl]-benzoic acid;
iopronic acid (2-[[2-[3-(acetylamino-2,4,6-triiodo-phenoxy]ethoxy] methyl]butanoic acid;
iopanoic acid, 3-amino-&agr;-ethyl-2,4,6-triiodobenzenepropionic acid.
The above Patent did not envisage any concentration or elimination step of the organic solvents (see examples 1, 2, 4, 5, 7, 27, 55).
In Examples 3 and 6, concerning non-ionic contrast agents (Iopamidol and Metrizamide) it is even necessary to use an autoclave or a sealed container to carry out the mineralisation at 130-150° C. for 1 hour.
Conve
Desantis Nicola
Incandela Salvatore
Peretto Ilaria
Viscardi Carlo Felice
Bracco Imagining S.p.A.
Fortuna Ana
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