Determination of ink removal and bleaching properties of old news and magazine papers

The aim of this study was to determine the effects of chemical agents on yield, ink removal, strength and optical properties of recycled pulp during pulping, flotation and bleaching stages.The study designed at tree stages. Firstly, the effects of calcium ion concentration and collectors such as fatty acid soap and sodium dodesil sulfate on yield, ink removal and optical properties of flotation deinked pulps were investigated. The most effective results namely higher ink removal with minimum yield loss obtained by 0.001 mol/l calcium chlorine and 1% fatty acid soap addition.At the second stages of the study for avoiding alkaline darkening, bleaching agents such as hydrogen peroxide, sodium perborate tetrahydrate and sodium parcarbonate were investigated. The effects of these chemicals on ISO brightness, CIE L*a*b* color and ink elimination values of deinked pulps were compared and the highest results obtained by sodium percarbonate addition (1% active oxygen) without alkaline usage.At the last part of the study, bleaching characteristics and color stability of deinked pulps were investigated. For bleaching pulp, oxidative agents like hydrogen peroxide and sodium percarbonate and reductive agents like sodium dithionite, formamidin sulfunic acid and sodium borohydride were used. The effects of these bleaching agents on ISO brightness, color values and strength properties of pulps were compared and the best ISO brightness values were obtained by sodium percarbonate and formamidin sulfinic acid usage. In addition, the best color removal values were obtained by sodium borohydride usage. In this respect, sodium percarbonate combined with formamidin sulfunic acid and sodium borohydride so ISO brightness value could be increased to 62.34% ISO. When the test papers exposed irradiation, the colors of paper couldn?t be stable because of rich mechanical pulp content. Consequently in terms of color stability, most resistant results obtained by sodium borohydride bleaching stages.