A method is for producing a moulding sand that is in particular recirculated, for foundry purposes. A mixture of a granular substance and aggregates, such as a binding agent and water, are added to a material that is not capable of swelling in water. The latter material has cavities with a specific surface area of more than 10 m.sup.2/g, in particular more than 50 m.sup.2/g and preferably more than 100 m.sup.2/g, for improving the characteristics of the moulding sand and/or for reducing the emission of harmful and/or odorous substances.