Continuous nitrate removal from waste waters, e.g from fertiliser industry, by (i) extn with water-insoluble or insolubilised primary, sec or tert aliphatic and/or aromatic amines, using liq or liquefied aliphatic and/or aromatic hydrocarbons and/or other org. solvents as diluents, followed by (ii) phase-separation, discharge of nitrate-free was waste water, stripping the org. solvent, separating the nitrate in usable water-soluble form by means of =1 basic stripping chemical and regenerating solvent, takes place by (a) passing the solvent and regenerating agent dispersion formed directly to extn step. without prior phase separation and (b) passing stripping chemicals used in stripping to be re-washed with water for recycling to stripping step. Solvent losses are minimised. Pref. stripping chemicals are alkali or alkaline earth hydroxides, partic. NH3 and amines with higher solubility in water than in org. solvents.
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