| Forest fiber resources are very lack in China,and waste paper fiber has gradually become an important fiber resources of China's pulp and paper industry.Continuously improving the proportion of waste paper fiber and the utilization rate of waste paper is the development trend of China's paper industry under the dual pressures of strict environmental standards and the shortage of fiber resources.However,with the increasing number of waste paper fiber recycling,the hydrogen bond between some fiber was destroyed and did not open as a result the phenomenon of the fiber's keratin,flocculation,agglomeration and so on emerged,which led to a different degree of reduction in the strength of waste paper pulp.Ionic liquid as a kind of new environment friendly medium was widely used in the dissolution,regeneration and application of cellulose.In this paper,Ionic liquid was used to pretreat waste paper pulp to solve the problem of low deinking efficiency of waste paper and serious phenomenon of pulp fiber horny through the softening of ionic liquids,and further improve the performance of waste paper fiber and the strength of the fiber.The effect of pretreatment of ionic liquid [EMIM]DMP on the deinking efficiency of laser printing waste paper and the properties of waste paper pulp were discussed.And the pretreatment conditions were optimized.Ultrasonic chemical combined with enzymatic pretreatment was conduced on laser printing waste paper,deinking efficiency of 33.68% and better deinking effect obtained,brightness of deinked pulp increased 6%ISO and the strength properties improved.The optimal treatment conditions were temperature 30 ?,time 2 min and power 360 w,in which deinking efficiency and brightness increased 33.68% and 6 %ISO respectively,and tearing index,bursting index and tensile index were all better.Laser printing paper was pretreated by ionic liquid [EMIM]DMP and the optimal pretreatment conditions were paper moisture content of 65%,[EMIM]DMP dosage of 15 wt% and temperature of 80 ?,in which the de-inking efficiency was 29.91%,brightness of de-inking pulp was 82.5 %ISO,tensile index 26.8 N·m·g-1,burst index 2.51 kPa·m2·g-1and tear index 16.4 mN·m2g-1.Compared with the unpretreated pulp,liquid,deinking efficiency,brightness,tensile index,burst index and tear index of the de-inking pulp pretreated by ionic liquid increased by 13.0%,5.9%,19.4%,16.74% and 32.32%respectively.the moisture content had significant influence on the deinking efficiency of waste paper during ionic liquid pretreatment process.The treated pulp fibers were partial dissolved,and were difficult to disperse in the pulperwhen the pulp content of waste paper was too low.Compared with the traditional pre-treatment conditions,the ionic liquid can not only improve the de-inking efficiency,but also can modify hornification of fiber and improve its papermaking properties.Analysis of SEM,XRD and FT-IR showed that the more fines on the surface of the fiber and these changes reflect the pretreatment of ionic liquid could facilitate fibrosis and freeness.The graphics of the IR shows that after [EMIM]DMP pretreatment and [EMIM]DMP/ultrasonic reprocessing the absorption intensity of waste paper pulp was increased respectively by 5.42 percent and 7.43 percent,which showed that ultrasound and ionic liquid pretrement can produce more hydroxyl groups.What's more,a comparison of the samples revealed that minor chemical changes occurred during ultrasound and ionic liquid pretreatment.The graphics of X-ray showed that after ultrasonic pretrement the degree of crystallinity of cellulose reduced,which proved that ultrasonic can destroy the crystalline regions of cellulose.It indicated that ultrasonic could act on the surface of fiber,thus making it to produce large number of tiny poresand improved the hornification of fiber. |
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