cumulo di bentonite

Mining and processing

Bentonite is a raw material present in many countries and mined in open pit quarries. Bentonite deposits are most often quite large, with lenticular beds, only a few meters deep. Bentonite production process features ore mining, sodium activation – if required -, drying, and milling. Sodium activation is performed to convert calcium bentonite to sodium bentonite, in which calcium ions are exchanged for sodium carbonate. Through drying, bentonite natural moisture content of about 25-35% is reduced. Since bentonite is hygroscopic, this is a difficult process that has to be performed under controlled temperature, in order not to damage its molecular structure. As a matter of fact, at temperature values above 500 °C, crystallisation water is irreversibly removed from bentonite, which loses all its properties and is turned into a grog (aggregates).