Hydrometallurgical decomposition of pyrite and marcasite in a microwave field

The decomposition of pyrite and marcasite in a nitric acid medium heated by microwave energy has been investigated. It was found that microwave exposure could effectively improve the leaching kinetics of both minerals. Marcasite had a substantially higher decomposition rate than pyrite. The decomposition rate increased with an increase in leaching temperature and concentration of acid and with a decrease in particle size. Only 5–7% of the dissolved sulphur was transformed into elemental sulphur. A kinetic study showed that the decomposition of both minerals was controlled by chemical reactions on the surfaces of particles.