<p>A method and apparatus for treatment of the fly ash are described wherein heavy metals are separated and wherein there is formed a leaching resistant slag; the fly ash is introduced into a reactor into an oxidizing gas stream which is heated to at least 2500 degrees C. in a plasma generator; the fly ash melts and forms liquid drops of slag and a carbonaceous or hydrocarbonaceous material is added to the gas stream which burns and supplies extra energy to the process; the ratio of oxygen and carbon is regulated so that the ratio CO2/CO+CO2 is kept within the limits 0.4-0.9; heavy metals in the fly ash such as zinc and lead are reduced and passed into the gas phase with the gas discharged from the reactor, cooled and washed and the metal oxides are separated; the slag is collected in the bottom of the reactor and can be continuously tapped via a slag lock; the slag's content of calcium oxide and silicon dioxide can be regulated by the admixture of a slag-forming material with a high content of silicon dioxide.</p>
