Mechanistic study on demulsification of water-in-diluted bitumen emulsions by ethylcellulose

Photoinduced demulsification of emulsions using a photoresponsive gemini surfactant

This Article reports on the influence of light irradiation on the stability of emulsions prepared using a photoresponsive gemini surfactant (C7-azo-C7) having an azobenzene skeleton as a spacer. When mixtures of trans C7-azo-C7 aqueous solution and n-octane are homogenized, stable emulsions are obtained in a specific region of weight fraction and surfactant concentration. Fluorescence microscopy observations using a small amount of fluorescent probes show that the stable emulsions are oil-in-water (O/W)-type. UV irradiation of stable O/W emulsions promotes the cis isomerization of trans C7-azo-C7 and leads to the coalescence of the oil (octane) droplets in the emulsions, that is, demulsification. While the equilibrated interfacial tension (IFT) between aqueous trans C7-azo-C7 solution and octane is almost the same as that between aqueous cis C7-azo-C7 and octane, the occupied area per molecule for C7-azo-C7 at octane/water interface decreases with the cis photoisomerization of trans isomer. Dynamic IFT measurement shows that UV irradiation to the interface between aqueous trans C7-azo-C7 solution and octane brings about an increase in the interfacial tension, indicating that the Gibbs free energy at the interface increases. From these results, the cis isomerization of trans C7-azo-C7 molecules at the O/W interface due to UV irradiation leads to direct contact between the water and octane phases, because of the reduction of molecular area at the interface, and subsequently makes the emulsions demulsified.

Ca2+ ion responsive pickering emulsions stabilized by PSSMA nanoaggregates

A novel Ca(2+) ion responsive particulate emulsifier, which is based on copolymer nanoaggregates, is reported in this work. Results from dynamic light scattering (DLS) and cryo-transmission electron microscopy (cryo-TEM) indicate that the formation of poly (4-styrenesulfonic acid-co-maleic acid) sodium salt (PSSMA) nanoaggregates is strongly dependent on Ca(2+) concentration. The PSSMA copolymer only aggregates above a critical Ca(2+) concentration (0.2 M) with an average diameter of 10-40 nm. After dilution with water, PSSMA nanoaggregates are rapidly redissolved again. On the basis of the properties of PSSMA nanoaggregates, Ca(2+) ion responsive Pickering emulsions were successfully prepared. At high Ca(2+) concentrations, the emulsions with high stability against coalescence can be prepared with the size in the submicrometer range as determined by DLS. Cryo-TEM and dynamic interfacial tension results confirm the adsorption of PSSMA nanoaggregates at the interface, which is the key to the stability of the emulsions. More importantly, rapid demulsification can be achieved by dilution with water on demand. It is because, upon dilution with water, PSSMA nanoaggregates undergo a transition from stable nanoaggregates to individual polymer chains, which leads to interfacial desorption of nanoaggregates and rapid demulsification of emulsions. Thus, this finding presents a new manipulation on emulsion stability and is expected to provide a useful guidance in the fields of oil recovery, food science, environment protection, and so on.

Cantilevered-capillary force apparatus for measuring multiphase fluid interactions

A new instrument is presented for investigating interactions between individual colloidal particles, emulsion droplets, foam bubbles, and other particle-particle or particle-surface interactions. Measurement capabilities are demonstrated by measuring interfacial tension, coalescence time for emulsion droplets, adhesion between giant multilamellar vesicles, and adhesion between model food emulsion particles. The magnitude of the interaction force that can be measured or imposed, ranges from 1 nN to 1 mN for particles ranging in size from 10 μm to 1 mm in diameter.

Application of rhamnolipid as a novel biodemulsifier for destabilizing waste crude oil

Waste crude oil emulsion was inevitably produced in the petroleum industrial process, causing harmful impact on the ecological and social environment. In this study, rhamnolipid was for the first time investigated for demulsification of waste crude oil. As found in this paper, rhamnolipid treatment could obtain over 90% of dewatering efficiency on refractory waste crude oil and such efficient demulsification was confirmed on model emulsions. As further demonstrated on the pilot scale (100 L), rhamnolipid treatment could recover over 98% of crude oil from the wastes. The recovered oil contained less than 0.3% of water and thus can directly re-enter into refinery process while the aqueous phase can be disposed into dischargeable water due to largely reduced soluble COD after subjected to 5 days of active sludge treatment. It seems that rhamnolipids as biodemulsifiers were of great prospects in the industrial demulsification of waste crude oil.