The recovery of Au and Cu from a printed board using supercritical water was studied, and the effects of the treatment with and without an oxidant on the components of the printed board were compared. Over 99 wt.% of metallic Au and metallic Cu was recovered in the solid form by oxidant-free supercritical water treatment at 400 degrees C and 25 MPa. However, the maximal removal of solid organics was 70 wt.% due to char-generation. Promotion of hydrolysis and inhibition of char-generation enhanced the removal of solid organics to nearly 90 wt.% at 380 degrees C. Under oxidative conditions, complete separation of solid organics from the inorganics occurred within 60 min. Metallic Au was unaltered and successfully recovered. Over 90 wt.% of metallic Cu was oxidized within 5 min, and only Cu oxides were recovered after 30 min. Oxidation of organics was promoted by coexisting Cu compounds contained in the printed board. (C) 2014 Elsevier B.V. All rights reserved.