RETENTION
One of the most controlled processes in papermaking industry is retention. It consists in increasing the quantity of fibres and fillers (the 2 most important raw materials) inside paper. As a result, the concentration of these products in waste water is lower. So, waste water treatment is cheaper and manufacturing profitability increases.
Aluminium salts, SAL and PAC, are used as coagulants to increase the retention of paper with other organic components such as Polyelectrolites, and they can also be used as ionic demand controllers.
