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.
EXTENDED DELIGNIFICATION OF OLD CORRUGATED CONTAINER AND TOTALLY CHLORINE FREE BLEACHING OF THE PULP
The paper industry has taken various steps to address environmental concerns and raw material limitations. Among them, paper recycling has been shown to be a viable option. In this study, the alkaline sulfite pulping of old corrugated containers (OCC) to produce bleachable pulp was investigated. A combination of one of the three active alkali levels (14, 16, and 18%; Na2O, and oven-dry weight of OCC); one of two pulping temperatures (145 and 175oC), and one of two pulping times (60 and 120 minutes) and sodium sulfite to sodium hydroxide ratio of 30/70 (mol/mol) were examined. After preliminary pulping and evaluation, pulp with a kappa number of 18.3 and brightness of 50.2%, which was produced applying 18% active alkali, sodium sulfite to sodium hydroxide ratio of 30:70, and pulping time and temperature of 120 minutes and 175oC, respectively, having the yield of 64.0% (based on oven dry weight of washed OCC) and 72.7% (based on original weight of the OCC as received), respectively, was selected for totally chlorine free (TCF) bleaching trials. Brightness, opacity, tensile, and tear strength indices of this pulp were measured as 50.2%, 81.4%, 27.7 N.m/g, and 12.35 mN.m2/g, respectively. Bleaching of this pulp applying 3% H2O2 and 2.25% NaOH at 90 minutes generated bleached pulp with brightness and opacity as 57.1% and 78.2%, respectively. The bleaching yield was measured as 92%. Tensile and tear strength indices of this pulp were measured as 25.1 Nm/g and 12.4 mN.m2/g, respectively.
Self-assembly of pyridinium-tailored anthracene amphiphiles into supramolecular hydrogels.
The mixing of a polyacid cross-linker with a pyridinium-functionalized anthracene amphiphile afforded a supramolecular hydrogel through a self-assembly process that was primarily driven by π-stacking and electrostatic interactions.