The most important membrane technologies used to remove phenols from wastewater are extractive membrane bioreactors and hollow fiber membranes; photocatalytic membrane reactors; high-pressure membrane processes such as nanofiltration, reverse osmosis, and pervaporation; and membrane distillation [3, 9, 24].

Phenolics are a group of organic compounds that are commonly found in industrial wastewater. They are considered as pollutants due to their toxic and harmful effects on the environment and human health. Therefore, it is essential to remove phenolics from wastewater before it is discharged into water bodies. One effective method for the removal of phenolics from wastewater is the reverse osmosis method.

Reverse osmosis (RO) is a water purification process that uses a partially permeable membrane to remove ions, molecules, and larger particles from water. This technique is based on the principle of applying pressure to overcome the osmotic pressure and force the water through the membrane, leaving behind the contaminants.

Here is a detailed explanation of why the reverse osmosis method is suitable for removing phenolics from wastewater:

1. High Removal Efficiency: Reverse osmosis membranes have pore sizes ranging from 0.0001 to 0.001 microns, which allows them to effectively remove small molecules like phenolics. The membrane acts as a barrier, allowing only water molecules to pass through and rejecting larger organic compounds, including phenolics.

2. Selective Separation: The RO process is highly selective, meaning it can differentiate between different types of molecules based on their size and charge. Phenolics have a relatively larger molecular size compared to water molecules, making them more likely to be rejected by the membrane.

3. Concentration Gradient: Reverse osmosis operates on the principle of creating a concentration gradient across the membrane. As the wastewater flows through the membrane, the concentration of phenolics on the feed side is higher than the permeate side. This concentration gradient drives the transport of phenolics from the feed side to the permeate side, resulting in their removal from the wastewater.

4. Continuous Operation: Reverse osmosis is a continuous process that can be operated for extended periods without significant loss of efficiency. This makes it suitable for treating large volumes of wastewater containing phenolics.

In conclusion, the reverse osmosis method is an effective and efficient technique for the removal of phenolics from wastewater. It offers high removal efficiency, selective separation, and continuous operation, making it a suitable choice for industrial wastewater treatment.