The fate of chlorine species during high temperature chlorine dioxide bleaching

Chlorine dioxide bleaching of nineteen non-wood plant pulps

“…No change of pulp viscosity was observed for chia pulp. But other studied showed that the D HT E treatment at 95°C for resulted in significant drop in post extraction pulp viscosity as compared to the DE one (Ventorim et al 2005, Ragnar 2003). Pulp exposed to high time/temperature reaction and acid pH may undergo slight carbohydrate hydrolysis.…”

“…The highest brightness advantage in D HT stage than D 0 stage after (EP) stage was 3 % for dhaincha oxygen delignified pulp. Ventorim et al (2005) found the first chlorine dioxide stage at high temperature (D HT ) decreased the brightness by 2.5 % ISO and kappa number by 46 % (1.9 units) after extraction stage as compared to the conventional D stage. Their results were also supported by others (Ragnar andLindström 2004, Eiras et al 2003).…”

“…Thus, at the early stage of the reaction most of the chlorine dioxide reacts with lignin, but the HexA remains in the pulp and are eliminated later through pulp acid hydrolysis stages (Eiras et al 2003). Ventorim et al (2005) revealed that a partial acid hydrolysis of HexA occurred in D HT treatment resulting into decrease in generation of chlorinated organic halides. Ventorim et al (2005) also found that at a similar ClO 2 dose (kappa factor 0.20 at pH 3.0) in D HT bleaching produced 46.3 % less AOX in the filtrate in relation to the D 0 .…”

“…Ventorim et al (2005) revealed that a partial acid hydrolysis of HexA occurred in D HT treatment resulting into decrease in generation of chlorinated organic halides. Ventorim et al (2005) also found that at a similar ClO 2 dose (kappa factor 0.20 at pH 3.0) in D HT bleaching produced 46.3 % less AOX in the filtrate in relation to the D 0 . Brogdon (2009) stated is his review that hot A-stage removed 30 to 90 % of HexA entering into the bleach plant and some lignin as well.…”

“…The hot acid treatment also formed new lignin phenolic hydroxyl groups, which may form new chromophores (Uchida et al 1999). Many of the research were carried out on D HT at initial stage of bleaching of hardwood pulp (Ragnar and Lindström 2004, Ventorim et al 2005, Zhang et al 2018, Tavast et al 2011, Davies et al 2009, Lachenal and Chirat 2000 but available literature on non-wood/agricultural residues pulps are scarce.…”