Study On Photocatalytic Bleaching Of Kraft Pulp And Photo-degradation Of Lignin

Photocatalytic bleaching of pulp is a environmentally friendly bleaching method.In order to study the degradation behavior of ligin in the prcess of pheotocatalytic bleaching of pulp in the article,photocatalytic bleaching of kraft pulp was investigated by using self-assembly device for photocatalytic bleaching.In the experiments,Rose Bengal(RB) was used as photosensitizer to activate oxygen into singlet oxygen.Photocatalytic bleaching technology of kraft pulp was optimizad through single factor experiments.Then the photocatalytic degradation of the lignin was studied, and use UV and FTIR to analyse the changes of functional groups of degraded lignin. The results showed that:Firstly, there must have oxygen to participate during the photocatalytic bleaching of the kraft pulp. The effect of Titanium dioxide and Rose bengal on kraft pulp:under alkaline conditions, RB> TiO2.Secondly,according to single factor experiments,the optimun bleaching condition of pahotocatalytic bleaching of Young pulp were followed as:Rose bengal(RB)0.5%(based on oven dry pulp), NaOH dosage5%(based on oven dry pulp), time120minutes, pulp concentration0.5%; The optimun bleaching condition of pahotocatalytic bleaching of Masson pine pulp were followed as:Rose bengal(RB)0.1%(based on oven dry pulp), NaOH dosage5%(based on oven dry pulp), time120minutes, pulp concentration0.5%. The optimun bleaching condition of pahotocatalytic bleaching of two kraft pulp were same rather than the amount of the photosensitizer.Thirdly, in the presence of oxygen and UV light conditions, lignin have a greater degree of degradation; The main reason for degradation of them was that benzene ring of phenyl propane structural cracked,which lead to the strand breaking of lignin molecule.Finally, Rose bengal has played an active role in the process of photocatalytic bleaching of wheat straw lignin, but it is not reflected in the process of photocatalytic degradation of kraft lignin.However,the degradation rate of two kraft lignin have a degree difference. Rose Bengal (RB) has a certain selectivity in the photocatalytic degradation of lignin. Finally,the behavior in the process of photocatalytic reaction between black liquor lignin and residual lignin of unbleached pulp has a certain similarity. To some extent, study the structural changes of black liquid lignin in the process photocatalytic degradation can provide a theoretical basis for photocatalytic bleaching of pulp.