Effect of pH in the Hypochlorite Bleaching on Dissolving Pulp Properties of Cotton Linter

The effect of bleaching with sodium hypochlorite, as one of the most important parameters in obtaining optimal alpha cellulose pulp from cotton linter was studied. In this respect, unbleached cotton linter pulp was prepared from Parchin chemical industry co., bleached by HEA sequence in pH=9, 11 and 13; and then its chemical structures properties such as alpha cellulose, degree of polymerization, carbonyl groups, carboxyl groups, microkappa, ash content, acid insoluble materials and brightness were characterized. The lowest amount of alpha cellulose and lignin content were achived at pH=9,. Also, carbonyl and carboxyl groups were obtained in the highest level as well as sulfuric acid insoluble and ash content in this pH. By increasing of pH to 11, maximum amount of alpha cellulose and pulp brightness and also minnimum amount of ash content were obtained. In pH=13, less delignification was occurred while the lowest carboxyl groups were also observed in this pH. Therefore, according to results, pH=11 was suggested for industrial alpha cellulose production.