STABILIZATION OF EMULSIONS BY HETEROCOAGULATION OF CLAY MINERALS USING A MICROFLUIDIC DEVICE

Azarmidokht Gholamipour-Shirazi¹; Marcio Carvalho¹; Jon Otto Fossum²

¹ Department of Mechanical Engineering, Pontificia Universidade Catolica do Rio de Janeiro - PUC-Rio; ² Department of Physics, Norwegian University of Science and Technology - NTNU, Trondheim, Norway

doi:10.20906/CPS/COB-2015-0404

Resumo

Research on emulsions is driven by their wide-spreading use in different industries, such as food, cosmetic, pharmaceutical and oil recovery. Emulsions are stabilized by suitable surfactants (electrostatic stabilization), polymers, solid particles (steric stabilization) or a combination of them. A microfluidic emulsification is the process of droplet formation out of two or more liquids under strictly controlled conditions, without pre-emulsification step. Microfluidic technology offers a powerful tool for investigating the properties of emulsions themselves. In this work, stable O/W emulsions were formed with hydrophilic Laponite RD® nanoparticles adsorbed at the interface of Drakeol 7 ® as the oil phase and water in a Dolomite ® droplet T junction chip. Salt (NaCl or CaCl2) was added to flocculate the laponite particles and hence to increase the emulsion stability. The presence of particles did not influence drop formation dynamics and thus the size of the drops generated. Different flow rates and different Laponite concentrations were examined to determine their effect on the stability of the formed emulsions. In some conditions, emulsions were stable up to 40 days. On the other hand interfacial dilational rheology studies were carried out using the pendant drop method to have an insight into the stabilization mechanism of Laponite nanoparticles. A high mobility of Laponite particles and an elastic film at 1.5% wt and 0.1M concentration of Laponite and NaCl were observed. Moreover, a crumpling was observed upon compression after an overnight aging time.

Palavras-chave: Pickering emulsion; steric stabilization; Microfluidics; emulsion stability