Chlorine dioxide bleaching of soda-anthraquinone jute pulp to a very high brightness.
Bleaching of soda-anthraquinone jute pulp by chlorine dioxide (ClO2) was studied to reach a target brightness of above 88% for the purpose of using less bleaching chemicals. The performance of either chlorine dioxide or peroxide in the final bleaching to boost brightness was also studied. The experimental results revealed that the final brightness depended on ClO2 charge in the Do and D1 stages. The brightness reversion was lower when the final stage brightening was done by peroxide. The use of Mg(OH)2 in the D1 and D2 stages improved the final brightness due to the formation of less chlorate and chlorite during the Mg(OH)2- based ClO2 brightening stages. The strength properties of pulp bleached by peroxide in the final stage was slightly better than that from ClO2 as the final ClO2 bleaching stage.
Influence of eucalypt wood supply on pulp brightness stability
One hundred different 5.5-year-old eucalypt wood clones were cooked to Kappa number 15 to 17.5 and the resulting kraft pulps oxygen-delignified to Kappa 9.5 to 11.5 under fixed conditions. Thirteen samples showing large variations in effective alkali requirement, pulp yield and O2-stage performance were selected for brightness reversion studies. These samples were bleached to 90 to 91% ISO. Heat reversion of the eucalypt kraft pulps was strongly influenced by the wood supply, with brightness losses of 2.1 to 3.6 and 0.8 to 1.7% ISO for ODEDD and ODEDP bleached pulps, respectively. Pulps bleached by the ODEDP sequence showed reversion values 1.3 to 1.9% ISO lower than those bleached by the ODEDD sequence. Pulp carbonyl content decreased by 35 to 40% during the final peroxide bleaching stage. Pulp carbonyl and carboxyl groups as well as permanganate number correlated positively with brightness reversion. Pulping, oxygen delignification and ECF bleaching performances showed no correlation with brightness reversion.
The first ground cricket (Orthoptera: Trigonidiidae: Nemobiinae) from mid-Cretaceous Burmese amber
Abstract A new genus and species, Birmaninemobius hirsutus gen. et sp. nov., is described on the basis of a well-preserved orthopteran specimen in mid-Cretaceous Burmese amber and attributed to the subfamily Nemobiinae (ground crickets) of the family Trigonidiidae (Grylloidea). As the first record of Nemobiinae from mid-Cretaceous Burmese amber, this new taxon not only provides novel morphological diversity in ground crickets but also indicates that the ground crickets lived in Burma (Tethyan islands) as early as the mid-Cretaceous.