MgベースSCPについて (2)
廃液の性質と処理
1975 年 29 巻 2 号 p. 77-83
詳細
1975 年 29 巻 2 号 p. 77-83
The cooking properties and pulp qualities of magnesium-base semichemical pulps obtained by the four modified cooking methods, i. e (1) magnefite, (2) slurry [Mg(OH)2+Mg(HSO3)2], (3) high-yield sulfite, (4) two-component (SO2+MgSO4); were descrised in the previous report2) . In this paper, the vapor-phase magnefite cooking method of Shide wood (Carpinus sp.) is further examined and its cooking properties and pulp qualities compared with those of the other four procedures.
In the vapor-phase magnefite method, fewer chemicals were required for the delignification process than in the other four cooking methods. The lignin content in the vapor-phase pulps was about 16% (based on pulps yielded in 70%) which is smaller than that of the two-components, magnefite and slurry pulps. However, the brightness of unbleached vapor-phase pulps was lower than that of the other four pulps.
When the five different waste liquors were neutralized to pH 7, only the color of the waste liquor from the two-components method was especially dark, as shown in Fig.3. In the case of a pulp yield ranging from 65 to 70%, the COD values of the waste liquors from the five methods (based on 200g of oven dried wood) were very similar to each other, as shown in Table 4.
Treatment of the waste liquors for pollution alleviation was then performed with lime, active carbon and aluminum sulfate to remove color and COD from the waste liquors. Treatment with aluminum sulfate removed about 90% of the color and the lime treatment removed about 85%, though neither removed much COD. However, a high COD reduction accompanied by a lower color reduction was observed when using active carbon. The lower the pH of the waste liquor, the higher the degree of the color reduction observed, as shown in Fig. 4, but COD reduction in waste liquors with a lower pH is small, as shown in Fig. 6.
