Since there are several types of resin designed to remove different types of contaminants, the regeneration processes can change. In general, the principle of resin regeneration is based on the contact of the resin with the necessary ions to allow the exchange of ions with those to be removed.
In general, at Durpro, when we regenerate resin, it comes in mixed bed tanks. This means that there are two types of resins in the tanks: anionic and cationic. To start the regeneration process, the resins must first be separated. To do this, the resin is placed in a column that will be filled with water. Due to the movement of the water, the anionic resin will go at the top of the tank as it lighter, and the cationic resin, which is heavier, will falls at the bottom.
Once separated, the cationic resin is treated with hydrochloric acid (HCl) or, in some cases, sulfuric acid (H2SO4). While the anionic resin is treated with caustic soda (NaOH).
The step of exposing the resin to the chemicals is used to restore the ions needed to perform the ion exchange. After the resin has been exposed to the appropriate chemical concentration for a specified time, it must be rinsed until there is no trace of chloride for cationic resin and sodium for anionic resin.
After rinsing, the resin is mixed and transferred to a reservoir or to the customers' containers. Before being transported, the resin tanks and vessels must be purged of water to prevent resin separation due to vibration. In addition to preventing separation, water purging protects against freezing during the winter, which could damage the tanks.