Purifying seawater has many benefits. Among those include providing potable water for third world countries, adequate amounts of agricultural water supply, and the ability to use the oceanic water supply as a source of drinking water. The current methods for purifying contaminated or salinated water include reverse osmosis and distillation. Both methods are energy-intensive and costly in terms of materials and equipment. Distillation also leaves behind the toxic contaminants which are usually disposed of in wastelands making the environment unsuitable for agriculture, drinking, and farmed animals. The contaminants are sometimes dumped back into the ocean which alters the chemical composition and balance of the sea and affects oceanic wildlife. As a result, it is important to explore alternative methods.
Some alternative methods to reverse osmosis and distillation include temperature swing solvent extraction (TSSE), battery electrode deionization, and forward osmosis. In a TSSE process, an inexpensive solvent reacts to low temperatures to extract freshwater. It involves decreasing the temperature of the solution which results in a lower solubility of water which drives the separation process. TSSE achieves purification up to 98.4%, and it is a low-cost alternative to distillation. It also eliminates the need for contaminant wastelands and has been found easy to scale up.
Another alternative method is bacteria electrode deionization. This method involves directing salty water into channels where electrodes separate purified water from the original feed by capturing the contaminate salts. The downside of this method may be that using too high voltage results in parasitic reactions and electrode oxidation, both of which are irreversible and undesired. To combat this problem, a voltage below the threshold could be used (0.6 V used in cited works). This method requires very low energy consumption which makes it a great substitute for other desalination methods.
Forward osmosis is another method that can replace reverse osmosis and distillation. Water is extracted from a feed using high osmotic pressure. This process can only be used for a hypertonic solution, not a hypotonic one. The setup for this process has two forward osmosis cells with flow chambers. They push towards countercurrent flow along the membrane. In order to replenish the water supply and prevent diffusion back through the undesired part of the membrane, a pump feeds seawater into the tank to compensate for the water that gets purified through the membrane. A downside of this process was found to be that hydrogen and hydroxide diffused through the membrane to maintain a charge balance.
Overall, a method that could be used to change the world would be purifying seawater. The undying supply of seawater could be used to solve droughts, agricultural issues, the world hunger crisis, and if done enough, could help our rising sea levels. As a result, the methods of purification discussed would be great alternatives to the costly and energy consuming current methods.