Application of nanomaterials for demulsification of oily wastewater: A review study

Industrial wastewater is the main source of environmental pollutants such as hydrocarbon compounds. This type of wastewater is in the form of oil in water emulsion. Depending on the size of droplets, they can be as micro-emulsion or nano-emulsion. Nano-emulsions are very stable and their destabilization is very difficult. This type of pollutant is dangerous and cause several problems for human health. Therefore, separation of oil/water emulsion, especially stable emulsions (droplets size smaller than 0.1 mu m) is essential. There are several approaches for wastewater treatment, including reverse osmosis, micro-filtration, nano-filtration, electrochemical, membrane, photocatalytic reaction, catalytic process, and adsorption method. Among these methods, adsorbents and catalysts are the most widely used because of the low-costs, high performance and simplicity. Activated carbon is one of the most important materials to eliminate contaminants from water. However, activated carbon has several disadvantages. Recently, the use of nanomaterials such as nano-adsorbents and nanocatalysts have been extensively used due to the high specific area, high capacity, high reusability and high efficiency. This article focuses on the application of nano-catalysts and nano-adsorbents and providing new data for destabilization and demulsification of hydrocarbon compounds (e.g., oil, gas condensate, and grease) from wastewater. Also, the benefits, applications and limitations of nanoadsorbents in water and wastewater treatment have been studied. Moreover, effective factors on the stability of oil/water emulsion were studied. Furthermore, the reusability of these nano-materials after the uptake process was studied. Previous studies indicate that NiFe2O4/sawdust nanoadsorbent has a high reusability and after 10 cycles of reusing, no significant change in its sorption capacity has been observed. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Industrial wastewater containing hydrocarbon compounds is harmful to human health. To separate oil/water emulsions and treat wastewater, methods such as adsorbents and catalysts can be used. Nanoadsorbents and nanocatalysts are widely used due to their high efficiency and reusability.