عنوان مقاله [English]
Background and objectives: Efficient use of waste papers and improve their quality has always been one of the targets in the pulp and paper industries. This study aimed to compare two stages bleaching of deinked pulp of newspaper and Magazine recycled pulp mixture using Sodium Dithionite (Y) and hydrogen peroxide (P).
Materials and methods: Firstly, the pulp was bleached using 1% hydrogen peroxide and in the next stage bleaching was performed using 0.5 and 0.75 percent dithionite and of hydrogen peroxide Respectively for 60, 90 and 120 minute.
Results: The results showed that with increase dosage of hydrogen peroxide in the second stage of PP sequence, decrease in bulk, opacity and increase in strength properties wasn't significant but increase in brightness and effluent COD showed significant changes. Prolongation of bleaching time in the second stage of PP sequence cause significant reduction in bulk, opacity and increase of effluent COD, brightness and strength properties. with increase the time of bleaching reactions in second stage of PY sequence, bulk and opacity reduction and increase in strength properties and brightness wasn’t significant, but with chemical dosage increasing, just brightness increasing was significant. Also, according to the results, with increase of chemical dosage in second stage of PY sequence, increase in the amount of Effluent COD load wasn’t significant, but with increasing of time of bleaching reactions in second stage of this sequence, increase in the amount COD load was significant.
Conclusion: Regarding to the results, effluent’s COD, brightness level and strength properties of PP sequence was higher than PY while bulk and opacity of that was lower than PY ones.