"Effects of acid pre-hydrolysis and xylanase treatment on pulp brightness and bleaching effluent"

Abstract

EUF bleaching ( Elemental chlorine free bleaching) is a bleaching process in which elemental chlorine is substituted by chlorine dioxide as a result less chlorinated organic compounds are observed in case of elemental chlorine free bleaching. However, ECF bleaching also result in production of chlorinated organic compounds to some extent. Alternatively, new bleaching technology such as enzymatic bleaching and acid pre-hvdrolysis are getting introduced in paper industries for the m in inlization of' cli lorinated organic compounds from the bleaching effluents. Among the other enzymes, xylanase enzymes have been using by researchers because it is free of cellulase activity, hence cause less degradation to cellulose. Enzyme treatment produces high brightness paper without harming the physical strength of paper. Hexenuronic acids ( IlexA ) are produced during the kraft pulping at mild alkaline conditions. During the time of' bleaching these hexenuronic acids consume bleaching reagents such as dO2 and 02 which leads to the increase in bleaching chemical demand. At the time of' kappa determination these hexenuronic acids consume permanganate chemical which result in increase in kappa number than the actual kappa number. Therefore, production of'these hexenuronic acids should he minimized before bleaching process. These hexenuronic acids can he minimized by using acid pre-hydrolysis before the bleaching of ki'al't pulp. Acid treatment cause hydrolysis of these hexenuronic acid hut cannot remove completely. So both of the bleaching technologies, enzymatic treatment and acid pre-hydrolysis are newly advanced bleaching technologies which produces high brightness of' pulp with minimum amount of' chlorinated organic compounds in bleaching effluent without oi' less harming to physical properties of paper.