Use of wetting agents to improve flotation deinking with magnesium oxide

In the past, alkali such as magnesium oxide and calcium hydroxide have been found to be not as effective in causing fibre swelling or in alkaline flotation deinking as sodium hydroxide. The addition of a wetting agent together with magnesium oxide has been found to increase fibre swelling to near that obtained with sodium hydroxide. The chemistry of the wetting agent was found to be important. The addition of the wetting agent with magnesium oxide in deinking using a Lamort laboratory deinking cell was also found to achieve similar deinking efficiency to that achieved with sodium hydroxide as the alkali source. Similar brightness levels were achieved, but the results indicated that slightly better ink removal efficiency occurred with the magnesium oxide system. The effluent from the magnesium oxide system was also found to have a lower dissolved salts content, which is an advantage to mills where salinity is a problem.