In-situ Generation of Peroxide in the Bleaching of Deinked Pulp

摘要

Peroxide has proven to be very successful in bleaching of deinked mixture of ONP(old newsprint)and OMG(old magazines).The possibility of sodium perborate and sodium percarbonate as the oxidizing agents in the bleaching of industrially deinked pulp with a high mechanical pulp content was investigated.Both chemicals generate hydrogen peroxide in aqueous solution.In the bleaching with peroxide,sodium hydroxide must be used in order to produce perhydroxyl anions.The advantage of using peroxide generators is that sodium hydroxide is not required,for sodium perborate the alkalinity is provided by borate and for sodium percarbonate,the alkalinity is provided by sodium carbonate.The results are compared with those of the initial deinked pulp and with pulp bleached using hydrogen peroxide.The efficiency of the bleaching was evaluated in terms of optical properties(ISO brightness,opacity,color coordinate,residual ink contents)and physical properties(breaking length,burst,tear).Results of the dissolution of organic material during bleaching or the amount of stickies in the final pulp and total organic contents of the bleaching effluent are presented.