Interrelations of structure, electric surface charge, and hydrophobicity of organo-mica and –montmorillonite, tailored with quaternary or primary amine cations

ORTA, MARÍA DEL MAR; FLORES, FEDERICO M.; MORANTES, CÉSAR FERNÁNDEZ; CURUTCHET, GUSTAVO; TORRES SÁNCHEZ, ROSA M.

MATERIALS CHEMISTRY AND PHYSICS

ELSEVIER SCIENCE SA

Lugar: Amsterdam; Año: 2018

0254-0584

In this work, organo-montmorillonite (organo-Mt) and organo-synthetic mica (organo-mica), obtained by quaternaryor primary amine cations (octadecyltrimethylammonium (ODTMA) or octadecyl-amine (ODA), respectively)exchanged at 50% and 100% of their respective CEC, were thoroughly characterized and tested forpyrimethanil uptake. The interlayer entrance of both surfactants for Mt loaded at 50% and 100% CEC indicated aclose basal space (of around 1.5 and 1.8 nm, respectively). However, for synthetic mica (Na-Mica-4) the basalspace shifted to higher values (3.5 and 3.9 nm and 4.7 and 5.0 nm, for ODTMA and ODA at 50% and 100% CEC,respectively) than those of organo-Mts, keeping the interlayer surface partially free for ODTMA-Mica-4 samples.Tg analysis revealed that the actual ODA loadings were around 40% and 80% for both clays and for ODTMAexchanged Mts, while the actual ODTMA loading for organo-mica samples did not exceed 10.6%. The decrease ofnegative zeta potential evidenced the presence of ODA or ODTMA at the external surfaces of organo-Mt, whilethe zeta potential curves for organo-mica samples described the system as a mixture of individual surfactants andNa-Mica-4 sample. Total specific surface area (TSSA) and contact angle (CA) measurements revealed a generalhydrophobicity increment with the presence of both surfactants. Interrelations of these parameters point out thedifferent affinity and steric hindrance of the polar head of both surfactants with the solid surfaces, which alsoconditioned pyrimethanil adsorption.