EFFICIENCY AND EFFLUENT CHARACTERISTICS FROM Mg(OH)2-BASED PEROXIDE BLEACHING OF HIGH-YIELD PULPSAND DEINKED PULP

摘要

The present research project, devoted to peroxide bleaching, evaluated magnesium hydroxide [Mg(0H)2] as a substitute of sodium hydroxide [NaOH] for different mechanical pulps and deinked pulp. The analysis of the results obtained on both TMP and CTMP showed that the use of Mg(OH)2 as a substitute of NaOH in peroxide bleaching allowed a reduction in both magnesium hydroxide and sodium silicate concentration, and a higher concentration of residual peroxide, which could be recirculated in the process. In deinked pulp, a significant reduction in Mg(OH)2 concentration was also achieved. The yield of the bleaching process was improved by 1 to 2%, yet the final brightness level was slightly lower. Other benefits related to the effluent were observed, such as a significant reduction of the cationic demand and a decrease of some environmental parameters, e.g. the biochemical oxygen demand (BOD), the chemical oxygen demand (COD), the dissolved solids (DS) and the total organic carbon (TOC).