Process for treating heavy ash or slag in general

A process for treating heavy ash or slag in general, characterised by mixing, in the interior of a rotating body, the heavy ash and/or slag and a water quantity in a weight ratio between 0.8 and 2, while simultaneously passing into the rotating body a flow of gaseous CO 2 in a concentration between 90 and 100% v/v for a period not exceeding 2 hours, on termination of the mixing stage the material being passed through at least one screen by which it is separated into ash of diameter greater than 5 mm and a mixture of water and ash with the ash of diameter less than 1 mm, said ash greater than 5 mm being subjected to deferrization treatment, to be then fed to a temporary store, the mixture of water and ash less than 1 mm being subjected to filtration treatment, the filtrate from which consists of a fine fraction of washed and carbonated slag, the water, containing salts washed from the slag and certain heavy metals, being fed to a water purification plant.