Purification of synthetic diamond and graphite mixtures in catalytic supercritical water oxidation processes

Abstract

Purifying diamonds after high-pressure and high-temperature synthesis is essential for their industrial applications, but classical purification methods usually generate a massive amount of toxic liquid wastes or cannot achieve good separation efficiency in a short time. This work proposes to utilize a catalytic supercritical water oxidation process as an environmentally friendly, fast, and highly selective alternative. To test the technical feasibility, we first examined the oxidation performance of non-catalytic and catalytic processes and discovered that potassium hydroxide and potassium carbonate accelerate oxidation kinetics. We also examine the influence of the oxidation process on the structural and surface characteristics of the synthesized diamonds. Potassium carbonate was chosen as the best homogeneous catalyst that does not deteriorate the synthesized diamond but effectively removes graphite residues. These results demonstrate that catalytic supercritical water oxidation is suitable for purifying synthesized diamonds in industrial mixtures.