Ultrapure water

Ultrapure water (also known as high-purity water) is water that has been purified to uncommonly stringent specifications. It is water that has been treated to the highest levels of purity for all contaminant types, including: organic and inorganic compounds; dissolved and particulate matter; volatile and non-volatile, reactive and inert; hydrophilic and hydrophobic; and dissolved gases. Ultrapure water is used in a variety of industrial and scientific applications where the presence of impurities can interfere with the process or experiment, such as in semiconductor manufacturing, pharmaceuticals, and laboratory settings.

Production

The production of ultrapure water is a complex and multi-staged process. It typically involves several steps to remove the various contaminants present in regular water. The most common methods include:

• Reverse osmosis: A process where water is forced through a semi-permeable membrane, leaving contaminants behind.
• Ion exchange: This method uses resins to replace undesirable ions with ones that are less objectionable.
• Electrodeionization: Combines ion exchange and electric currents to remove ions from water.
• Ultraviolet oxidation: Uses UV light to break down organic molecules.
• Ultrafiltration: A process that removes particles and macromolecules from water by passing it through a porous membrane.

Each of these processes targets specific contaminants and may be used in combination to achieve the desired level of purity.

Applications

Ultrapure water is critical in several industries and fields, including:

• Semiconductor Manufacturing: The production of semiconductors requires water that is free from any contaminants that could interfere with the manufacturing process.
• Pharmaceuticals: Ultrapure water is used in the formulation of medications and as a solvent in the production of pharmaceuticals to ensure product safety and efficacy.
• Power Generation: In power plants, especially those involving steam turbines, ultrapure water is used to avoid corrosion and scaling.
• Laboratories: Research and analytical laboratories use ultrapure water in experiments to ensure that results are not compromised by water impurities.

Standards and Specifications

The quality of ultrapure water is defined by several standards and specifications, including the resistivity (measured in megohms-cm), total organic carbon (TOC) levels, and the presence of particulate matter. The most stringent specification is often required in the semiconductor industry, where water resistivity must be higher than 18.2 MΩ-cm at 25°C, and TOC levels must be kept to a minimum.

Challenges

Maintaining the purity of ultrapure water is challenging due to the potential for contamination at any point in the production process or within the distribution system. Contamination can occur from the materials used in the construction of the water purification system, from airborne contaminants, or from the containers used to store the water.

Conclusion

Ultrapure water is essential for the success of many industrial and scientific processes. Its production involves sophisticated technology and equipment to remove virtually all contaminants. As industries and technologies evolve, the demand for ultrapure water with even stricter purity standards is likely to increase.