The milder alkalinity results in lower contaminants of water emission in high yieldpulp bleaching

One of the great problems in the bleaching of high yield pulps has been the heavy COD (Chemical Oxygen Demand) load in the bleaching effluent. The replacement ofconventional alkali source with a new alkali substance has been investigated, here. Threelevels of Mg(OH)2 was substituted for three of NaOH in peroxide bleaching of CMP (Chemi-Mechanical Pulping) pulp. This replacement caused to decrease the effluent COD and turbidity. Results have indicated that the pollution load of effluent increased bybleaching chemicals growth, but the increasing in chemicals percentage had an improvingeffect on optical and physical properties of pulp. In Mg(OH)2 bleaching processes, alkali consumption rise had less effect on the increasing in pollution load of bleaching effluentthan conventional process. The residual peroxide of Mg(OH)2 bleaching process, in filtered liquor after pulp bleaching, was higher than it’s conventional bleaching process. Also, the residual peroxide levels increased by bleaching chemicals growth.

کلیدواژه ها:

Bleaching ، Alkali source ، Peroxide ، effluent ، Residual peroxide