**2.1. Materials**

Commercial clays ClNa, Cl30B, Cl20A and Cl15A were kindly offered by Southern Clay Products Inc. PMAA (polymethacrylic acid, Janssen Chimica), Salecan (Souzhou Chemicals), N, N′-methylenebisacrylamide (Sigma Aldrich) and ammonium persulfate (Sigma Aldrich) were used as received.
