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 FT-IR, 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 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
In this paper we show that the active interplay of nonlinear kinetics and transport phenomena in a chemical oscillator can be exploited to induce and control chaos. To this aim we use as a model system the ferroin-catalysed Belousov-Zhabotinsky (BZ) oscillating reaction, which is known to evolve to characteristic chaotic transient dynamics when carried out under batch and unstirred conditions. In particular, chemical chaos was found to appear and disappear by following a Ruelle-Takens-Newhouse (RTN) scenario. Here we use medium viscosity as a bifurcation parameter to tune the reaction-diffusion-convection (RDC) interplay and force the reaction in a specific sequence of dynamical regimes: either (i) periodic → quasi-periodic → chaotic or (ii) periodic → quasi-periodic or (iii) only periodic. The medium viscosity can be set by adding different amounts of surfactant (sodium dodecyl sulphate), known to have a little impact on the reaction mechanism, above its critical micelle concentration. Experimental results are supported by means of numerical simulations of a RDC model, which combines self-sustained oscillations to the related chemically-induced buoyancy convection.
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