Preparation and characterization of bio-organoclays using nonionic surfactant
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Preparation and characterization of bio-organoclays using nonionic surfactant Ilaria Calabrese1 • Giuseppe Cavallaro1 • Giuseppe Lazzara1 • Marcello Merli2 Luciana Sciascia2 • Maria Liria Turco Liveri1
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Received: 6 May 2015 / Revised: 5 August 2015 / Accepted: 19 September 2015 Ó Springer Science+Business Media New York 2015
Abstract The present study was aimed at the preparation and characterization of tailor made hybrid materials, whose peculiar hosting capability could be exploited in biotechnological applications. With this purpose, the modification of K10 montmorillonite by intercalation of Tween 20 surfactant, was accomplished. The influence of two internal parameters, namely pH and surfactant/clay ratio, on the surfactant uptake ability by clay was investigated. The adsorption mechanism was elucidated on the basis of complementary kinetic and equilibrium studies and, then, corroborated by the useful information provided by the FTIR, TGA and XRD characterization. The gathered results allow to draw the conclusion that the whole surfactant uptake is the result of two contributions: a site-limiting component, governed by negative cooperative interactions, which takes into account for the Tween 20 adsorption onto the pristine clay, and a non-specific linear partitioning component, related to the adsorption of the surfactant onto the in situ prepared organo-clay. Moreover, at strongly acidic pH, a mechanism consisting of two-steps pathways involving two non-energetically equivalent binding sites of the clay surfaces, was proposed, while, on increasing the
Electronic supplementary material The online version of this article (doi:10.1007/s10450-015-9697-1) contains supplementary material, which is available to authorized users. & Marcello Merli [email protected] 1
Dipartimento di Fisica e Chimica, Universita` degli Studi di Palermo, Viale delle Scienze - Parco d’Orleans II - Pad. 17, 90128 Palermo, Italy
2
Dipartimento di Scienze della Terra e del Mare (DiSTeM), Universita` degli Studi di Palermo, Via Archirafi 36, 90123 Palermo, Italy
pH, the clay interlayer becomes the sole available site for the surfactant uptake. In the light of the interesting results obtained, among the plethora of potential biotechnological applications, the present paper suggests the exploitation of the prepared organo-clays to improve the performance of either hydrophilic or hydrophobic drug carriers systems. Keywords Organo-clays Montmorillonite Tween 20 Adsorption kinetic Isotherm Dual mode models Drug delivery system
1 Introduction The opportune functionalization of clay materials represents a promising strategy to design new materials with peculiar features for technological applications (Sa´nchezMartı´n et al. 2008; Lee and Tiwari 2012; Cavallaro et al. 2014a, b; Shen 2001; Ruiz-Hitzky et al. 2010). The attention of many scientists recently focused in the study of the resulting organoclays as drug delivery systems (DDS), i.e., pharmaceutical formulations which are able to change the rate and/or the time and/
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