METHOD FOR THE PRECIPITATION OF ARSENIC AND HEAVY METALS FROM ACIDIC PROCESS WATER

The invention relates to a method for the precipitation of arsenic and heavy metals from acidic, in particular sulphuric acid, process water (12), containing both arsenic and heavy metals, comprising a precipitation method phase (II) with a sulphide precipitation stage (C) in which arsenic and at least one primary heavy metal are precipitated together, wherein a sulphide precipitating agent (16) is added to the process water (12) such that arsenic is precipitated as arsenic sulphide and the at least one primary heavy metal is precipitated as metal sulphide. The sulphide precipitation stage (C) comprises a first sulphide precipitation step (C.1) in which a sulphide precipitating agent is added to the process water (12) in a first sulphide precipitation reactor (14), whereby an intermediate fluid (22) is generated still containing arsenic or still containing arsenic and the primary heavy metal. The intermediate fluid (22) is transferred into a second sulphide precipitation reactor (30) after the first sulphide precipitation step (C.1). The sulphide precipitation stage (C) comprises a second sulphide precipitation step (C.2) in which a sulphide precipitating agent is added to the intermediate fluid (22) in the second precipitation reactor, whereby a residual fluid (32) is generated which is substantially free from arsenic.