Novel thermally stable organo-montmorillonites from phosphonium and imidazolium surfactants

► Purity and drying conditions are crucial for the thermal stability of bentonite. ► After purification, the thermal stability of bentonite increases significantly. ► Highly stable organoclays are produced from phosphonium or imidazolium surfactants. ► As the chain length of the surfactant increases, the thermal stability decreases.