Effect of introducing ozone in elemental chlorine free bleaching of pulp on generation of chlorophenolic compounds

Effect of using ozone before elemental chlorine free (ECF) bleaching of oxygen delignified wheat straw pulp produced following soda-anthraquinone pulping on bleaching effluent and pulp properties was studied. The effluent generated during bleaching of pulp contains high amount of adsorbable organic halogens (AOX), chemical oxygen demand (COD), biochemical oxygen demand (BOD) and highly toxic chlorophenolic compounds. This study is aimed to utilise green chemistry approach during bleaching of one of the abundantly used agro residue wheat straw for improving the quality of bleaching effluent and pulp properties. Introducing ozone stage before ECF bleaching resulted in significant reduction of chloriphenolic compounds like chlorocatechols by 48.9 Vs, chloroguaiacols by 33.3 %, chlorovanillins by 28.4 % and chlorophenols by 26.7 % in the effluent compared to those of control. Incorporation of ozone before ECF bleaching BOD, COD, AOX and colour were reduced by 40.0 Vs, 41.1%, 46.7 % and 57.8 Vs, respectively, as compared to control. Optical properties like brightness and whiteness of the pulp bleached using ozone were also improved by 2.5 units and 4.0 units, respectively as compared to that with control.