Reverse Osmosis & Electrodialysis ( Chemistry Animations)

Summary

This video explains the process of desalination, specifically focusing on the removal of salts from brackish water. Two primary methods are discussed: electrodialysis and reverse osmosis. Electrodialysis uses an electric current to move ions through ion exchange membranes, making it an economical but energy-dependent method. Reverse osmosis applies pressure to separate water from higher concentration solutions, efficiently removing impurities. Both methods have their advantages and limitations, such as electrodialysis being susceptible to electricity supply issues and reverse osmosis being cost-effective and suitable for continuous water supply.

Takeaways

• 😀 Desalination refers to the process of removing salts from brackish water to make it suitable for consumption or other uses.
• 😀 Brackish water is a mixture of saltwater and freshwater, and desalination helps remove the salts and impurities.
• 😀 Electrodialysis is a desalination method that uses electric current to move ions through ion-exchange membranes, separating salts from water.
• 😀 In electrodialysis, cation and anion exchange membranes divide the container into compartments, where ions move toward oppositely charged electrodes.
• 😀 One of the key advantages of electrodialysis is that it is an economical method, especially when electricity costs are low.
• 😀 Electrodialysis operates at room temperature, making it more energy-efficient than methods requiring high temperatures.
• 😀 A disadvantage of electrodialysis is that it cannot remove colloidal impurities, and its efficiency depends on continuous electricity supply.
• 😀 Reverse osmosis (RO) is a desalination process where water is forced through a semi-permeable membrane under pressure, leaving salts and impurities behind.
• 😀 Reverse osmosis removes not only salts but also colloidal and suspended impurities, making it effective at purifying water.
• 😀 Reverse osmosis systems are generally durable, with membranes that last a long time but may require cleaning due to fouling.
• 😀 The main advantage of reverse osmosis is its low operational costs and the ability to deliver continuous water supply, but it can consume more energy due to the pressure required.

Q & A

What is desalination?

Desalination is the process of removing salts from salty water, such as brackish water, to make it suitable for use or consumption.

What does brackish water mean?

Brackish water refers to water that has a higher salinity than fresh water but is less salty than seawater. It typically contains a mix of fresh and seawater.

What are the two main methods of desalination discussed in the video?

The two main methods of desalination discussed are electrodialysis and reverse osmosis.

How does electrodialysis work?

Electrodialysis uses direct electric current to transport ions through ion exchange membranes. Cations move towards the cathode, and anions move towards the anode, which leads to desalination in the central compartment while the side compartments concentrate with salty water.

What are the advantages of electrodialysis?

Electrodialysis is an economical method that can operate at room temperature and is a continuous process.

What are the disadvantages of electrodialysis?

Electrodialysis cannot remove colloidal impurities, and it is not effective if electricity supply is inconsistent or if electricity costs are high.

What is osmosis?

Osmosis is the movement of water from a region of low solute concentration to a region of high solute concentration through a semi-permeable membrane, until the concentrations on both sides equalize.

How does reverse osmosis differ from osmosis?

Reverse osmosis is the process where external pressure is applied to the side with higher concentration, forcing water to move from the high concentration side to the low concentration side, opposite of natural osmosis.

What are the advantages of reverse osmosis?

Reverse osmosis can remove colloidal and suspended impurities, ensures an uninterrupted water supply, and has relatively low capital, running, and maintenance costs.

What are some of the key characteristics of the semi-permeable membrane used in reverse osmosis?

The semi-permeable membrane in reverse osmosis is highly durable and selectively allows water to pass through while blocking larger particles, including colloidal and suspended impurities.