IL43425A - Continuous process for removing nitrates from wastewaters by extraction - Google Patents

Claims (8)

43425/2 touch the drop phase and promote the joining of the drops. The process according to the invention achieves a removal of about '80 of the nitrates. By using two extraction stages the removal can be increased' to about 95$. Claims

1. A continuous process for removing nitrates from waste waters with the ' minimum possible solvent losses, in which case the nitrate-containing waste water is extracted with a primary, secondary, or tertiary, aliphatic and/or aromatic amine which is substantially water insoluble or which can be made water insoluble by using, as a diluent, aliphatic and/or aromatic hydrocarbons and/or other organic solvents which are either liquid under normal pressure or which have been liquefied from solvents gaseous- under normal pressure, whereafter the waste water essentia ly devoid of nitrates is directed, after phase separationf into the watercourse, and the organic solvent phase is fed into a stripping stage where the nitrates are separated with a strippin chemical, which reacts alkalically, in a usable water solution form, and the solvent phase is returned to the regeneration stage, characterized in that the dispersion composed of the regenerated solvent and the regeneration agent is fed directly into the extraction stage without first separating the phases, and after the stripping stage, the stripping chemical is fed into a return wash carried out with water in order to return the stripping chemical to the stripping stage.

2. A process according to Claim 1, c h a r a c t e r i z e d i n that sulphate ions, e.g., sulphuric acid, are used for regenerating the solvent.

3. A process according to one of the above claims, c ha r a c t e r i z e d i n that the stripping chemical used is an alkali hydroxide, an earth alkali hydroxide, ammonia, or .v/ater solutions of these in different strengths, or organic primary, secondary or tertiary amines with such a carbon chain length that their water solubility is greater than their solubility in an organic solvent. 43425/2

4. A process according to one of the above claims, c h a r a c t e r i z e d i n that the pH of the purified waste water emerging from the extraction is controlled at about 5-10, preferably about 7-9, in order to minimize the solubility of the solvent in the purified waste water*

5. A process according to Claim 4, c h a r a c t e r i z e d •i n that the alkali used for the pH control is an environmentall non-harmful sodium, potassium, or calcium carbonate.

6. A process according to Claim 4 or 5f c h a r a c t e r i z e d i n that the solvent remaining in the purified waste water is v/ashed av/ay in the' solvent circulation with pure solvent taken before ' the regeneration stage in order _to return the' solven remaining in the purified waste water to the circulation.

7. A pjrocess according to Claim 6, c h a r a c t e r i z e d i n that the said solvent wash is carried out in a contact apparatus, through which the purified v/aste water with a controll pH and the organic solvent phase coming from. the return wash of the stripping chemical and effecting the wash are directed.

8. A process according to one of the above claims, c h a r a c t e r i z e d i n that the return wash of th^ stripping chemic is carried out with a byflow of the purified waste water0 : . ·. . :. ·!