چكيده به لاتين
Pickering emulsions are a class of emulsions stabilized by surface-active colloid particles or solid particles instead of small molecular surfactants that cause serious damages into the ecosystem. This phenomenon has been discovered by Ramsden and Pickering since the early 20th century. It attracted a huge attention due to their potential applications in food, cosmetics, and pharmaceuticals, and other fields because of the advantages such as: non-toxicity, biodegradability, the encapsulation efficiency, and etc. Emulsions generally consist of solid particles at the interface of two immiscible liquids and their small spherical droplets with narrow size distributions. The solid particles are adsorbed at the liquid–liquid interface and reduce the interfacial energy of the system which means, the required energy to desorbtion is much higher than the thermal energy, so a stable emulsion is produced. There are many factors affecting the stability of emulsions including concentration, interactions between the particles, shape, size, and the wettability of which the two classes of emulsion (water-in-oil (W/O) or oil-in-water (O/W)) can be formed. There are many solid particles such as: polymer micelles, latex particles, inorganic particles, proteins, and even bacterial cellulose nanocrystals have been employed to stabilize Pickering Emulsions which among them, the bio-based materials have a great importance due to the environmental issues and their high potential in playing the role of hydrophobic-hydrophilic stabilizers. One of the most interesting areas in which these solids have been appeared is the catalysis and developing chemical reactions due to their great advantageous shown in figure x. Amid the chemical reactions, the Knoevenagel condensation with the ability to the formation of c-c bond in essential intermediates in the production of pharmaceuticals, pesticides, and fine chemicals has received considerable attention, especially in industry. Conventionally, this condensation is carried out using an aldehyde and a C-H acid in the presence of a base. Nowadays, the sequential oxidation of alcohols to aldehyde followed by the Knoevenagel reaction has attracted a great deal of attention compared to the classical multi-step reactions. Indeed, in the cascade reactions there is no need to the isolation of intermediates and wasting the solvents. In this paper, we presented an oil in water Pickering emulsion, which was stabilized by shilajit@Fe composites. Shilajit is a mixture of humic acids (85%) and non-humic compounds (15%) founding in the layer of rocks in many mountain ranges. These pale-brown to blackish-brown exudates has been applied in various fields such as: catalyst, dose-dependent inhibitor against herpes simplex virus, human cytomegalovirus, and respiratory syncytial virus (RSV). the behavior of the prepared Pickering emulsion and also the effect of various factors such as pH, the amount of solid particles and the ratio of oil to water on the properties of the Pickering emulsion were investigated. Also, a Sh/Fe-stabilized Pickering emulsion and its catalytic performance for the Knoevenagel condensation reaction were investigated.
