Comparative Study On Bleaching Of Aspen CMP Between Reductive Electrochemical And Conventional Process

This paper study on reductive electrochemical bleaching process of Aspen small timbers or thrubberies CMP with sodium dithionite generated in situ and the method of bleaching solution recycling.the traditional hydrogen peroxide bleaching and sodium dithionite bleaching were proceeded as comparison experiment.A compare was made on the brightness and the parameters of the wastewater among the three bleaching processes and point out the advantages and characteristics of the reductive electrochemical bleaching process of Aspen CMP with sodium dithionite generated in situ.In this experiment,firstly the single-stage and the second stage processes was proceeded by Aspen small timbers or thrubberies CMP which was bleached with the traditional hydrogen peroxide and sodium dithionite process respectively.Results were got,the optimum reaction conditions,the data of brightness gain and the testing result of wastewater quality of the two bleaching processes.Then the reductive electrochemical bleaching process of Aspen small timbers or thrubberies CMP with sodium dithionite generated in situ was peoceeded,in this process sodium sulphite was deoxidized and generate sodium dithionite which bleach pulp in situ. Results of single-stage bleaching show the highest brightness gain (11.8%ISO) was obtained while the variation of sodium and the temperature settled at 0.8 mol/L and 70℃, respectively, pH and current were 5.0 and 4.0A,which is 2.6%ISO higher compared with the traditional method.The brightness gain of 10.9%ISO also can be obtained when the consumption of sodium sulphite was reduced to 0.4mol/L. The recycle bleaching process was carried out under this condition the brightness gain of 10.6%ISO was obtained while the actual average consumption of sodium sulphite can touch to 2.8% on OD pulp.The advantages was obvious compare to traditional processes. A lot of operation costs for sodium sulphiteand was reduced and pollutant discharge for unit weight of pulp is reduced greatly because of introducting of recycle bleaching process and commercially viable was got at the same time.