Advanced Switchable Molecules and Materials for Oil Recovery and Oily Waste Cleanup

Abstract

Advanced switchable molecules and materials have shown great potential in numerous applications. These novel materials can express different states of physicochemical properties as controlled by a designated stimulus, such that the processing condition can always be maintained in an optimized manner for improved efficiency and sustainability throughout the whole process. Herein, the recent advances in switchable molecules/materials in oil recovery and oily waste cleanup are reviewed. Oil recovery and oily waste cleanup are of critical importance to the industry and environment. Switchable materials can be designed with various types of switchable properties, including i) switchable interfacial activity, ii) switchable viscosity, iii) switchable solvent, and iv) switchable wettability. The materials can then be deployed into the most suitable applications according to the process requirements. An in-depth discussion about the fundamental basis of the design considerations is provided for each type of switchable material, followed by details about their performances and challenges in the applications. Finally, an outlook for the development of next-generation switchable molecules/materials is discussed.

Engineering hybrid microgels as particulate emulsifiers for reversible Pickering emulsions

“… 32 In such cases, the phase inversion of microgel-stabilized emulsions from one type to another is conceivable, for example, inversion of o/w to w/o emulsions, which is becoming increasingly important in petroleum chemistry, drug delivery, and biphasic catalysis. 33–36 Nevertheless, the previous reports of switchable Pickering emulsions stabilized by microgels were exclusively between the emlsification and demulsification, and directly triggering the phase inversion of microgel-stabilized emulsions remains a great challenge. For the purpose of reversion between o/w and w/o emulsions, microgels especially capable of being altered with sufficient hydrophobicity from the intrinsic hydrophilic state are required.…”

Janus Nanofiber Antibacterial Membrane for Switchable Separation of Oil/Water Emulsions

“…Treatment and recycling reuse of oily wastewater caused by offshore oil spill accidents and the discharge of food industry have become an urgent hot issue and promote the development of oil/water separation materials. − Conventional commercial separating technologies including floatation, skimming, centrifugation, and gravity separation suffer from low separation efficiency, high energy cost, as well as secondary environmental pollution, which restrict their widespread use.…”

Novel Strategy of Polymers in Combination with Silica Particles for Reversible Control of Oil–Water Interface

“…Most of the stimuli-responsive molecules previously reported in the literature would depend on reversible interactions, including hydrogen bonds, ion pairs, coordinate bonds, etc. Such stimuli-responsive molecules based on chemical interaction generally require sophisticated design and tedious synthesis. ,− In addition, the application scenarios are often quite complicated in terms of the chemical composition of emulsions and processing conditions, such as water quality, oil composition, and geographical and biological environment, which means that selecting the appropriate trigger based on actual conditions is quite important. ,, It ultimately hinges on a balance between the investment costs and the economic benefit of stimuli-responsive molecules. Thus, reducing chemical consumption, improving sustainability, and simplifying processes are extremely rewarding to meet various demands in different applications.…”

“…Normally, the stable emulsions fabricated with all sorts of emulsification systems (surfactants, polymers, nanoparticles, etc.) are essential to protect oil droplets from demulsification, but the superior stability is sometimes undesirable and even detrimental because of the irreversible phase transition behavior. − For example, the emulsified crude oil can poison refinery catalysts and cause rust problems on industrial equipment. , Moreover, the stable emulsions may suppress the activity of the reactants in biphasic solvent systems in emulsion polymerization and often hinder downstream processing and product purification. , Therefore, the oil–water phase separation of emulsions with superior stability has become a sensitive and challenging issue in recent decades.…”

“…20,32−35 In addition, the application scenarios are often quite complicated in terms of the chemical composition of emulsions and processing conditions, such as water quality, oil composition, and geographical and biological environment, which means that selecting the appropriate trigger based on actual conditions is quite important. 1,36,37 It ultimately hinges on a balance between the investment costs and the economic benefit of stimuli-responsive molecules. Thus, reducing chemical consumption, improving sustainability, and simplifying processes are extremely rewarding to meet various demands in different applications.…”