Characterization and study of sorptive properties of differently prepared organoclays from a brazilian natural bentonite - Vianna, Marilda Mendonça Guazzelli Ramos; Dweck, Jo; Kozievitch, Valquiria de Fátima Justo; Valenzuela Díaz, Francisco Rolando; Büchler, Pedro Maurício (Journal of Thermal Analysis and Calorimetry,, 2005)