Depending on the type of ore processed, flotation effluents generally contain metallic ions such as Fe, Cu, Zn, Mo and Pb, in addition to cyanide, sulphides and dissolved organic compounds (xanthates, collectors and frothers). The basic concept presented in this essay is the treatment of flotation effluents for water reuse instead of its disposal. Thereby, the authors propose the following integrated treatment system based on oxidation and precipitation:(i) Clarification of flotation effluent; (ii) Clarification of flotation effluent; Catalyzed oxidation at a controlled pH and simultaneous precipitation of hydroxides/metal oxides; (iii) Separation of precipitates; (iv) Return of treated effluent to the flotation plant.The treatment strategy involves the oxidation of cyanide species, sulphides and/or collectors in order to remove flotation reagents and active products from the decomposition of organic materials. In this way, dissolved metal cations are released to be precipitated as oxides and hydroxides at a pH range between 8 and 9. By removing these constituents, the recycled water back to the concentrator will be free of substances that could potentially interfere with the flotation system. The process comprises the following reaction stages:Cyanide oxidation CN- + Oxidante → CNO- + H2O Cu(CN)3- + Oxidante → Cu2+ + 3 CNO- + 3 H2O Zn(CN)3- + Oxidante → Zn2+ + 3 CNO- + 3 H2O CNO- + 2 H2O → HCO3- + NH3 NH3 → NH3 (g)Precipitation of metals: Zn2+ + 2 OH- → Zn(OH)2 (s) Cu2+ + 2 OH- → Cu(OH)2 (s) MoO42- + Ca(OH)2 → CaMoO4 (s) + 2 OH- Fe3+ + Ca(OH)2 → Fe(OH)3 (s) + Ca2+ Pb2+ + CO32- → PbCO3 (s)Hydrolysis of xanthates and oxidation of sulphides: 6 ROCS2- + 3H2O → 6ROH + CO32- + 3CS2 + 2CS32 CS32- + 3 H2O → CO32- + 3 H2S CS2 + 2 H2O → CO2 + 2 H2S S2- + 4 H2O2 à SO42- + 4 H2OPrecipitation of sulphates and carbonates: CO32- + Ca2+ → CaCO3 (s) SO42- + Ca2+ → CaSO4 (s)The essay contains a "case study" of the treatment of effluents from a real operating plant. This will serve to demonstrate the utility of the concept of this treatment and the potential savings in water supply to the plant.