Recent advances in synthesis techniques for layered double hydroxide composites and hybrids for use in separation of oilfield water-flooding emulsions and wastewater

Oil-contaminated wastewater resulting from spills and discharges is a critical environmental pollution issue. In addition to the petrochemical industry, other well-known sources responsible for the discharge of oil-contaminated wastewater include the dairy industry, edible-oil refineries, the poultry-processing industry, and the pharmaceutical industry. Hence, separation of water from contaminated oil/water emulsion is necessary for its further use. Demulsification of oil/water emulsions provides the best alternative to deal with the oil contaminated wastewater and processing of crude oil and water emulsion after recovery before downstream processing. Demulsification techniques, particularly mechanical separation methods, can be highly energy consuming. To reduce operational expenses, energy efficiency is a key factor when developing demulsification systems. Chemical demulsification offers a cost-effective alternative for commercial applications. Recently, miscellaneous nanoparticle-based materials such as layered double hydroxides (LDHs) have been examined as chemical demulsifiers due to their ability to disturb the stability of oil/water emulsion. In particular, the different techniques that are employed to fabricate different types of LDH composites and membranes are considered of primary importance. Various LDH composites and membranes have been evaluated for demulsification of water and oil emulsions, and they have been found to provide excellent surface properties to serve the purpose of efficient separation of oil and water. Several advantages of LDH composites are also discussed. Numerous other applications for LDH composites are mentioned. Environmental concerns and their mitigation have been considered for future green synthesis of LDH composites.