Authors: MEHDI RAHMANINIA, AHMAD JAHAN LATIBARI, S. AHMAD MIRSHOKRAEI, MOHAMMAD AZADFALLAH
Abstract: The ever increasing volume of waste newspaper indicates the importance and availability of this paper for recycling. However, aging of the print, especially offset print, plays an important role in recycling, which requires additional consideration. The effects of aging and sodium hydroxide on de-inking of old newspaper is investigated. In all, 4 natural aging periods (0, 4, 8, and 12 months) and 5 concentrations of sodium hydroxide (0%, 0.5%, 1.0%, 1.5%, and 2.0% on bone-dry (BD) weight of the paper) were employed to study the de-inking of offset printed newspaper. Optical properties of recycled paper, including brightness, yellowness, and absorption coefficient, were measured. The results indicate that the treatment of non-aged newspaper with 1.5% sodium hydroxide produced the best de-inking. Aging newspaper for 4 months and longer decreased the brightness of de-inked pulp and increased the absorption coefficient, whereas higher doses of sodium hydroxide increased brightness and decreased the absorption coefficient. No significant difference was observed between 1.5% and 2% sodium hydroxide. Aging decreased yellowness and sodium hydroxide increased it.
Keywords: Aging, Absorption Coefficient, Brightness, De-inking, Yellowness
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