Title
Effect of introducing ozone prior to elemental chlorine free bleaching of wheat straw pulp on pulp paper and effluent properties
Authors
SANDEEP KUMAR TRIPATHI NISHI KANT BHARDWAJ and HIMADRI ROY GHATAK

Received June 16, 2018
Published Volume 53 Issue 1-2 January-February
Keywords elemental chlorine free bleaching, ozone bleaching, wheat straw pulp, viscosity, brightness, kappa number

Abstract
Ozone has been considered for the development of greener processes for hardwood and softwood pulps. This paper summarizes the results obtained using ozone bleaching on wheat straw pulp, followed by elemental chlorine free bleaching. This work evaluated the effect of introducing ozone bleaching on the optical properties of wheat straw pulp, along with the content of metal ions and hexenuronic acid in the pulp, pulp strength and morphological properties, as well as effluent properties. Introducing an ozone stage into the ECF bleaching sequence of wheat straw pulp improved pulp brightness by 2.5 units, pulp whiteness – by 4.0 units, while reducing the hexenuronic acid content by 21.6% and brightness reversion – by 34.8%, and allowed attaining physical strength and morphological properties comparable to those of the control. The introduction of the ozone treatment reduced the Fe, Cu and Mn content in the pulp by 6%, 11% and 31%, respectively. It also significantly reduced the COD in the bleaching filtrate by 41.2%, BOD – by 39.6%, colour level – by 57.9% and AOX – by 47.3%, compared to the control. The introduction of ozone prior to elemental chlorine free bleaching of wheat straw pulp was demonstrated to improve effluent quality, while yielding comparable pulp and paper properties.