Effect of Chelating Pretreatment on Photocatalysis Bleaching

Abstract

After ethylene diamin tetra-acetic acid (EDTA) chelating pretreatment, in unbleached pulps the content of metal ions Mg2+、Mn2+、Fe3+、Zn2+ and Cu2+ are reduced in varying degrees by atomic absorption spectroscopy analysis, among the ions, the maximum removal rates are Cu2+ and Mg2+. And when the added amount of EDTA is 0.6%, the removal result of metal ions is the best. After chelating pretreatment, the pulp’s brightness has been increased about 4.3%ISO~5.2%ISO, the pulp’s hardness has been reduced by 0.7%~1.0%, and the pulp’s viscosity has been kept well. Besides, when the added dosage of EDTA is 0.6%, the increasing of whiteness and the decreasing of hardness are the greatest. Through the contrast research of photocatalysis bleaching to the two pulps of before and after pretreatment, the results has been found that the brightness of photocatalysis bleached pulp been increased about 3.0%ISO, and the decreasing rates of hardness reach to the maximum, and the viscosity remains well.