| In China,fast-growing poplar has been widely used and developed in the pulp and papermaking industry due to its short growth cycle,the characteristics of renewable and strong fibers with high quality,.The disadvantage of high yield pulp(HYP)of fast-growing poplar,such as poor strength properties and high fine fiber content,limited its further application.Thus the properties of poplar HYP usually need to be modified with different method.In this study,poplar pulp fibers were pretreated under different conditions,and tested through the modern analytical instruments,including canada standard freeness(CSF)tester,fiber quality analyzer(FQA),surface area analyzer(SAA),surface charge density measuring instrument,environmental scanning electron(SEM)microscopy,thermogravimetric analysis and physical properties analysis of papers.The aim was to investigate the effects of ultrasonic-chemical and biological enzymes treatment and obtain optimized treatment conditions.Firstly,effect of ultrasonic assisted xylanase treatment chemical mechanical pulp(CMP)was carried out.The results showed that the optimized treatment conditions were ultrasonic power of 120 W,xylanase dosage of 30 U/g,and temperature of 40~?C for 30 min.Compared to the untreated pulp with a CSF of 450 mL,CMP pulp treated by xylanase alone and ultrasonic assisted xylanase increased rapidly to 675 mL and 700 mL,with an increase of50.0%and 55.6%,respectively.Compared to the untreated pulp with SSA of 4.8 m~2/g,SSA of the pulp treated by xylanase alone increased 6.0 m~2/g,and SSA of the pulp treated by ultrasonic-assisted xylanase increased to 6.5 m~2/g,with an increase of 25.0%and 35.4%,respectively.SEM images showed that xylanase treatment and ultrasonic assisted xylanase treatment all could change the fiber surface morphology,promote the pulp fibrillation.Effect of ultrasonic assisted xylanase treatment was more obvious and fiber surfaces were etching depth.FQA analysis showed that the average fibers length and the average fibers width changed slightly,the fine content decreased as positive effect.Fibers fibrillation were enhanced with porous surface and exposed more fibers in the treating process of xylanase and ultrasonic wave,,thereby the pulp drainability and pore size distribution were improved.Then,the effect of ultrasonic assisted ionic liquid(1-allyl-3-methyl imidazolium chloride([AMIM]Cl)treatment on poplar chemi-thermomechanical pulp(CTMP)was discussed.The results showed that the optimal treatment conditions were ultrasonic power of120 W,ionic liquid dosage of 5 mL/g dry pulp,reaction temperature of 60~?C,and reaction time of 30 min.Under those conditions,compared to untreated pulp with a CSF of 760 mL,the CSF of CMP pulp treated by ionic liquid alone and ultrasonic assisted ionic liquid decreased rapidly to 580 mL and 550 mL,with the decrease of 23.7%and 27.6%,respectively.Compared to untreated pulp with a WRV of 1.45 g/g),the WRV of pulp treated by ionic liquid simple was 1.68 g/g,and the pulp treated by ultrasonic-assisted ionic liquid was 1.76 g/g,with the increments of 15.9%and 21.4%,respectively.Compared to untreated pulp with a SSA of-10?eq/g,the SSA of pulp treated by ionic liquid simple was-16?eq/g,and the pulp treated by ultrasonic-assisted ionic liquid was-18?eq/g,with the decrease of 60.0%and 80.0%,respectively.Compared to untreated pulp,FQA analysis of pulp treated by ionic liquid alone and ultrasonic-assisted ionic liquid showed that the average fibers length decreased by 8.0%and 8.2%,and the average width increased by 1.0%and 5.4%,kink index increased by 9.5%and 20.3%,and the SSA increased by 47.3%and 134.1%.Compared to the untreated pulp,the tensile index,tear index,burst index and folding times of pulp treated by ionic liquid increased by 30.1%,32.0%,8.8%and 100.0%,respectively.For the pulp treated by ultrasonic-assisted ionic liquid,they increased by 41.0%,36.0%,11.7%and 150.0%,respectively.In terms of improving the strength of the pulp,the effect of ultrasonic assisted ionic liquid was better than that of ionic liquids alone.Finally,the effect of ultrasonic-assisted sodium hydroxide(NaOH)treatment on poplar CTMP were discussed.The results showed that the optimal treatment conditions were sodium hydroxide solution concentration of 3%,reaction temperature of 30~?C and reaction time of 30min.Under these conditions,compared to untreated pulp with a CSF of 504 mL,CSF of CMP pulp treated by sodium hydroxide alone and ultrasonic assisted sodium hydroxide increased rapidly to 565 mL and 605 mL,with the increase of 12.1%and 20.0%,respectively.At the same time,the cellulose content increased by 19.4%and 20.5%,hemicellulose content decreased by 23.6%and 31.3%,acid insoluble lignin content decreased by 7.9%and 11.9%,and the acid soluble lignin content decreased by 4.5%and 27.3%.In terms of fibers quality treated by NaOH alone and ultrasonic assisted NaOH,FQA analysis showed that the average fibers length increased by 3.8%and 1.0%,and the average fibers width decreased by 2.8%and 2.1%,and the fines content decreased by 18.3%and 19.7%.Compared to untreated pulp,tensile index,burst index and tear index of the pulp treated by NaOH alone increased by42.2%,72.9%and 40.0%,and for the pulp treated by ultrasonic assisted NaOH they increased by 45.6%,79.2%and 36.0%,respectively. |
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