CPEIA was obtained by treating sodium montmorillonite with a branched polyethylenimine (Lupasol® PR 8515, active matter > 98%; Mw: 2000; CAS No.: 25987-06-8; ratio of primary, secondary and tertiary amines: 1:0.92:0.70), kindly supplied by BASF Española S.A. (Barcelona, Spain).