Istituto Guido Donegani S.p.a.

Massimo Stolfi

Adriano Mattera

Marino Quaglino

Pasqualino Spighi

Disclosed is a process for removing boron compounds from aqueous effluents. The effluents are contacted, under stirring, with a divalent metal sulphate Me.sub.I SO.sub.4 and a divalent metal hydroxyde Me.sub.II (OH).sub.2, the sulphate-hydroxyde couple being selected from the group consisting of BeSO.sub.4 --Ba(OH).sub.2 ; BeSO.sub.4 --Sr(OH).sub.2 ; BeSO.sub.4 --Ca(OH).sub.2 ; MgSO.sub.4 --Ba(OH).sub.2 ; MgSO.sub.4 --Sr(OH).sub.2 ; MgSO.sub.4 --Ca(OH).sub.2 ; CaSO.sub.4 --Ba(OH).sub.2 ; CaSO.sub.4 --Sr(OH).sub.2 ; SrSO.sub.4 --Ba(OH).sub.2 ; ZnSO.sub.4 --Ba(OH).sub.2 ; ZnSO.sub.4 --Sr(OH).sub.2 ; ZnSO.sub.4 --Ca(OH).sub.2 ; CdSO.sub.4 --Ba(OH).sub.2 ; CdSO.sub.4 --Sr(OH).sub.2 and CdSO.sub.4 --Ca(OH).sub.2. The sulfate Me.sub.I SO.sub.4 and the hydroxide Me.sub.II (OH).sub.2, by reaction with each other, cause the sulphate Me.sub.II SO.sub.4 and the hydroxide Me.sub.I (OH).sub.2 to precipitate. The amount of Me.sub.II (OH).sub.2 is at least stoichiometric in respect of the amount of Me.sub.I SO.sub.4 and the precipitation pH is within the range of 7 to 10 when Me.sub.I SO.sub.4 is ZnSO.sub.4, and 10 to 13 in the other cases. At the end of the precipitation the mixture is subjected to decantation and to filtration or centrifugation, thus separating the boron-containing precipitate from the purified effluents.

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Milan, Italy

Massimo Stolfi