Sulfuric acid bleaching of kraft pulp 1: Bleaching of hardwood and softwood kraft pulps

To develop a new nonchlorine bleaching technology, hardwood and softwood kraft pulps, before and after oxygen-alkali predelignification, were treated with dilute sulfuric acid solutions (pH 1.0-1.8) at 100°C for 1 h and then extracted with aqueous sodium hydroxide at 70°C for l h. Hardwood kraft pulp was successfully bleached. The delignification selectivity was similar to that seen with oxygen-alkali bleaching; and it was greatly enhanced by the addition of sodium nitrate and sodium nitrite. The sulfuric acid bleaching can replace the presently adopted oxygen and chlorine stages if the additives are allowed. This bleaching process was also effective for oxygen-bleached hardwood kraft pulp, but it was less effective for softwood kraft pulp and oxygen-bleached softwood kraft pulp. The effectiveness of the addition of sodium nitrate and sodium nitrite was more apparent for softwood kraft pulp than for hardwood kraft pulp.Part of this report was presented at the 7th International Symposium on Wood and Pulping Chemistry, Beijing, July 1993     

Examination of polychlorinated dibenzo-<Emphasis Type="Italic">p</Emphasis>-dioxins and polychlorinated dibenzofurans in process water of kraft pulp bleaching mill using chlorine dioxide from the aspect of environmental water quality

Process water of a pulp mill with extended kraft cooking, two-stage oxygen delignification, and chlorine dioxide bleaching was examined from the aspect of a new standard for environmental water quality in Japan. According to the new standard, the concentration of dioxins – polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, coplanar polychlorinated biphenyls – in environmental water is restricted to less than 1pg TEQ/l. We clarified that the concentrations of the dioxins in sewers in the chlorine dioxide stage and the alkali stage were less than 1pg TEQ/l and that the 2,3,7,8-tetrachlorodibenzofuran concentrations were 0.5pg/l or less. In addition, a main source of 1,3,6,8- and 1,3,7,9-tetrachlorodibenzo-p-dioxins in the process water seemed to be an agrochemical in water supplied from a river.     

Studies on hypersaline-tolerant white-rot fungi IV: effects of Mn 2+ and NH 4 + on manganese peroxidase production and Poly R-478 decolorization by the marine isolate Phlebia sp. MG-60 under saline conditions

Manganese peroxidase (MnP) production by Phlebia sp. MG-60 is strongly regulated by Mn²⁺ and NH₄⁺ at various sea salt incubation conditions. Extra-added Mn²⁺ and NH₄⁺ obviously inhibited MnP production, but sea salts relieved the inhibition partially or completely. Three media were prepared: Kirk medium with addition of 0%–5% sea salts (KS medium), a high level of Mn²⁺ (300mg/l) in KS medium (HM-KS medium), and a high level of NH₄⁺ (430mg/l) in KS medium (HN-KS medium). Without addition of sea salts, the dye Poly R-478 was significantly decolorized by low MnP activity (about 200U/l) and a low level of laccase activity (about 100U/l) in KS and HM-KS media. In the cultures in which laccase activity was almost completely inhibited by 3% and 5% sea salts, MnP activity higher than 400U/l was necessary for Poly R-478 decolorization in all of the three media. We first report the linear correlation of MnP activity and decolorization of Poly R-478 under saline conditions and the effect of laccase on this relation.