Decreasing calcium oxalate scaling by partial substitution of Mg(OH)_2 for NaOH in the peroxide bleaching of mechanical pulps

摘要

Calcium oxalate scaling can be minimized by partially replacing NaOH with Mg(OH)_2 as the alkali source in the peroxide bleaching of mechanical pulps.The amount of precipitated oxalate was negligible when 30-50% of the NaOH was replaced with Mg(OH)_2 during bleaching.A higher brightness was also achieved compared to the NaOH-based peroxide process.The addition of MgSO_4 at a high dosage to a peroxide stage can also decrease the amount of precipitated oxalate,but this approach is not as effective as the partial replacement of NaOH with Mg(OH)_2.