| The utilization of bamboo pulp can alleviate the shortage of wood raw materials in China's papermaking industry,and at present,the use of high yield bamboo pulp will have a good development prospect.The high yield pulp has many advantages,such as high yield,good physical properties,and small environmental pollution,however,the bleachability and whiteness stability of high yield bamboo pulp are relatively poor,which seriously restricts the application of high yield bamboo pulp,especially the development of advanced paper.In this paper,amylase,lipase and protease were used to pretreat the non-lignin components in SCMP pulp.The effects of starch,lipids and protein on the bleaching performance of SCMP pulp were discussed,which provided theoretical basis for improving the whiteness and whiteness stability of high yield bamboo pulp.The experimental results are as follows:(1)Pretreatment of SCMP pulp with amylase,lipase and protease can improve the bleachability and whiteness stability of the pulp,the optimal process conditions are as follow:Amylase pretreatment: amylase dosage was 10 IU/g,treatment time was 20 min,starch degradation rate reached more than 31%,pulp whiteness was up to 12.6%,yellowing value decreased by 16.69% at 8h of aging;Protease pretreatment: the amount of protease was 5 IU/g,the treatment time was 60 min,the protein degradation rate was more than 82%,the brightness of pulp increased by 6%,and the yellowing value decreased by 12.47% after 8h aging;Lipase pretreatment: lipase dosage is 10 IU/g,treatment time is 50 min,fat degradation rate is more than 80%,pulp whiteness is increased by 5.8% at the highest,and yellowing value is reduced by 27.69% after 8h aging;Under the optimum conditions,the whiteness of pulp pretreated by amylase,lipase and protease increased by 11.8%,10.95% and 12.9% respectively,which indicated that enzyme pretreatment could save bleaching agent,improve the bleachability of pulp and improve the bleachability of pulp.(2)XPS results showed that after pretreatment with lipase,protease and amylase,the C1 s content of pulp decreased,the percentage of O increased,O/C value increased,the increase of O/C in SCMP pulp was 41%,41%,20%,and that in bleached pulp was 16.4%,20.4%,and 17.5%,respectively.Among them,the lignin on the surface of SCMP pulp decreased by 10.58%,12.8% and 9.24%,indicating that pretreatment with three enzymes could reduce the lignin and extract on the surface of fiber and increase the bleachability of SCMP pulp.(3)SEM-EDS analysis showed that the content of N and S in SCMP pulp and bleached pulp changed little before and after pretreatment with lipase,protease and amylase,while the content of C decreased and the content of O increased.The O/C of SCMP pulp increased from 30.26% to 33.37%,43.85% and 36.65%,and the O/C of bleached pulp increased from 27.97% to 33.7%,42.61% and 36.1%,respectively,which indicated that enzyme pretreatment can reduce extract and lignin content on the surface of the fiber,improve the bleaching performance of pulp.(4)The results of PY-GCMS showed that the guaiacol structure and some compounds with double bond structure such as alkene,ketone,ester and phenol in SCMP pulp were reduced after lipase,protease and amylase treatment;In addition,the relative content of some starch pyrolysis products such as 1,6-dehydrated-d-galactofuranose and 2-(5H)-furanone was reduced. |
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