Staged alkali and hydrogen peroxide treatment of poplar chemi-mechanical pulp

Abstract

In order to improve the physical properties and brightness of poplar chemi-mechanical pulp, a new staged alkali and hydrogen peroxide treatment method was proposed and applied. Wood chips were impregnated and swelled with an alkali solution and then treated with a hydrogen peroxide bleaching liquor. A thorough evaluation and comparison of the physical properties and brightness of the pulps that underwent different treatment methods was conducted. The results showed that when the pulp was treated with an alkali and hydrogen peroxide treatment method with an alkali dosage of 6% and a hydrogen peroxide dosage of 6%, the tear index was 3.64 mN‧m2/g, the tensile strength was 3.61 kN/m, and the pulp brightness was 67.1% (ISO). The obtained physical properties and brightness of the alkali and hydrogen peroxide method treated pulp were greater than the traditional alkaline hydrogen peroxide method values, as well as the values of any other single treatment methods.

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“…There are two phases during the bleaching reaction between lignin and H 2 O 2 : the chromophore structures of lignin are first destroyed by oxidizing the carbonyl structure and quinoid structure of the lignin side chain; subsequently, H 2 O 2 may react with the benzoquinone structure of lignin to change the solubility of lignin, or react with the side-chain carbonyl and carbon− carbon double bond of lignin to further oxidative degradation, leading to lignin removal. 53 This was most likely that the reaction area between the lignin and the bleaching solution was mainly stopped on the surface modification rather than polymer degradation. As demonstrated by the results, an alkali dosage of 4% and a H 2 O 2 dosage of 12% are the optimum technological conditions for comprehensive consideration.…”