Preparation And Application Of Pickering Emulsifier Based On Alginate

Emulsions stabilized by solid particles instead of traditional emulsifier were discovered by Pickering as early as 1907, subsequently this type of emulsions is also called Pickering emulsions. Pickering emulsions can avoid some negative effects of traditional surfactants, such as toxicity, foamability and so on. And it has unique self-assembly effect of the interface particles. Therefore, Pickering emulsions has aroused great attention of scholars.Sodium alginate (S A) is a kind of natural polysaccharide. And it has many advantages such as cheap and available, non-poisonous, non-immunogenicity, good biocompatibility and biodegradability and so on. In this article, SA and and its hydrophobic modified derivatives were used to devolope micro-nano gels which were constructed as a new type of Pickering emulsifier. The Pickering emulsifier we developed will have potentially broad application in the fields of medicine, food, and cosmetics.Through the ionic crosslinking method, calcium alginate micro-nano gel (SA-Ca) was gotten, using SA as raw material and CaCl2 as crosslinking agent. The particle size and distribution of SA-Ca were studied by Dynamic Light Scattering (DLS). The results showed that the SA-Ca particles has small particle size and narrow distribution. The effect of the concentration of SA and CaCl2 on SA-Ca particle size and distribution was investigated. The experimental results showed that SA-Ca particles with controllable uniform size can be prepared by the ionic crosslinking method. The experimental operation is simple and the process is easy and green. But the particle concentration of prepsred SA-Ca is too low and it is difficult to make it used as Pickering emulsifier directly. By a simple inverse-emulsion method, calcium alginate micro-nano gel (SA-Ca) was gottenvia the aid of confined impingement jets (CIJ) mixer. The particle size, distribution and stabilityof SA-Ca were studied by Dynamic Light Scattering (DLS). The effect of the dosage of surfactant, the volume ratio oil to water and the concentration of SA and CaCl2 on SA-Ca particle size and distribution was investigated. The best experimental conditions was gotten:the dosage of surfactant is 1% of oil, chloroform:SA solution is 3:1, the concentration of SA is 15 g/L and the concentration of CaCl2 is 0.5 mol/L. The dry morphology of SA-Ca particle was characterized by transmission electron microscopy (TEM) and scanning electron microscope (SEM). The results showed that SA-Ca particles has a regular spherical morphology and uniform size distribution. Three phase contact angle which can show the surface wettability of the SA-Ca particle was measured by video contact angle meter. And the SA-Ca particles showed a strong hydrophilic. Therefore, the hydrophobic modification of the SA-Ca particle should be conducted before it is used as Pickering emulsifier.Amphiphilic sodium alginate amidation derivatives CsNSA of different substitution degree were synthesized by the reaction of sodium alginate with aliphatic amine, using 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC-HC1) as a coupling agent. The purified products were characterized by fourier transform infrared spectroscopy(FTIR), elementary analysis(EA). The prepared C8NSA was used to developed C8NSA-Ca particles by inverse-emulsion method. The effect of the substitution degree of substitution degree, and the concentration of SA and CaCl2 on C8NSA-Ca particle size and distribution was investigated. The best experimental conditions were determined with the goal of stabilizing emulsions with high-stability and uniform size. The choosen experimental conditions was that the substitution degree of C8NSA is 30.76%, the concentration of C8NSA is 10 g/L and the concentration of CaCl2 is 0.5 mol/L. The particle size, distribution and dry morphology were characterized by DLS, TEM and SEM. And the results showed that the C8NSA-Ca is uniform with a round-likely roundness morphology. Hydration particle size is about 400 nm and dry particle size is about 200 nm. Three phase contact angle of the C8NSA-Ca particle was measured by video contact angle meter. It showed that the volume of the three phase contact angle of the C8NSA-Ca increased with the increasement of substitution degree of C8NS A. And all of them are significantly larger than that of SA-Ca. The three phase contact angle of the 30.76%C8NSA-Ca is close to 90°which can prove that the 30.76%C8NSA-Ca particles have good conditions to stablized emulsion.The prepared 30.76%C8NSA-Ca particles were used as Pickering emulsifier to stabilize liquid paraffin/water emulsion. Several important factors which influence the stability of emulsion were studied. The results showed that the stabilisation of the emulsion can be improved with the increasement of the concentration of 30.76%CsNSA-Ca particle. After the particle concentration reaches a certain degree, the emulsion stability and emulsion droplet size and distribution has not been obviously improved with the increasement of the concentration of 30.76%C8NSA-Ca particle. Oil phase volume fraction affects the stability and type of the emulsion. The Pickering emulsion phase inversed when the oil phase volume fraction is over 0.7. Adjusting the pH and concentration of electrolyte can also change the stability of the emulsion. The Pickering emulsion droplet size stabilized by 30.76%C8NSA-Ca particle can reach the minimum. Rheological analysis showed that the emulsion viscosity was higher and the elastic behavior was stronger when of the concentration of 30.76%C8NSA-Ca particle was higher. The fluorescence microscopic manifestations of the emulsion proved that 30.76%C8NSA-Ca particle adsorption on the oil-water interface, forming a layer of granular membrane which coated the dispersed phase droplet. The granular membrane can prevent the dispersed phase droplet coalescence effectively so as to achieve the goal of a stable emulsion.