Smart membranes for oil-water emulsions separation: A review

Pollution is a huge challenge in today's time. It is adversely affecting the living life on earth. Starting from the air in the atmosphere to the noise we hear. It is a big barrier to being healthy as it is impacting our health adversely.

 One type of that includes water pollution. Water pollution is generally caused due to the harmful waste released in the water by industries, domestic reasons, oil leakage in petroleum, etc. This type of pollution mainly affects marine life, but it also affects other lives due to the consumption of this polluted water.

Keywords: water pollution, oily water, oil spills, membrane, fouling, bionics, oil-                         water separation  

Among all the reasons, there is a huge amount of oily wastewater produced due to oil spills. Oil spill incidents mainly occur due to industrial petroleum operations and processing. Oily wastewater has several adverse effects on the marine environment. This is already witnessed previously during the oil spill that occurred due to petroleum transport pipelines, storage tanks, or transport facilities. Due to the effects of oil spills, marine life is affected to a wide extent. Not only oily water affects marine life, but life outside it. It causes various health problems as this contaminated water can be consumed by humans.

 Several technological ways can be used to separate oil from water:

1.   Absorption

2.   Dissolved air flotation

3.   Coagulation

4.   Gravity separation

5.   Biological treatment.

But all of these methods have some drawbacks such as less removal efficiency, high operational cost, high energy consumption, corrosion, and production of contaminated solid waste.

With the widespread of growth in separation technologies, researchers have found that various membranes can be used to overcome the drawbacks of these methods. Membranes have several reasons to be used for oil-water separation. The reasons include that the membranes have a small footprint, they are environment friendly, cost-effective, highly productive, low chemical consumption, steady operation, and they are highly efficient in separation.  

The recent study based on the membrane separation method includes four sections:

1.   Membrane properties and characterization for oily wastewater separation.

2.   The employed materials to fabricate membranes (i.e. metallic, organic, inorganic, hybrid materials)

3.   Primary materials for designing membranes (i.e. mixed matrix nanocomposites and multilayer nanocomposites)

4.   Membrane fabrication techniques and surface modification methods.

The potential to fabricate membranes with tunable properties has improved for oil and water separation.

The membrane separation method is very effective for removing oil droplets. However, traditional membranes face the issue of membrane fouling occurring on surfaces and internal structures. This creates limitations for membranes in terms of practical operations.

But, adopting biometric hierarchical roughness in membrane design has proven to be of great interest. The new generation of membranes based on bionics provides a new way for antifouling oil-water separation.