Fibers Separation Of Cotton Stalk Combined With Organic Solvent Treatment

Cotton stalk is available in abundant and is an underused alternative to natural fibers.Currently,a main treatment of cotton stalk is still field burning or landfill,which is not only wasting resources but also can cause environmental pollution.And it is not in line with the state's strategy of promoting green and sustainable development.Therefore,the high value-added utilization of crop waste has attracted much attention.The main components of cotton stalk are cellulose,hemicellulose and lignin,but the cell wall of cotton stalk is“refractory”,and the fiber matrix separation using traditional cooking method is inefficient and energy consuming,so treatment before and after cooking is extremely important.Therefore,in this work the combination of alcohol and sodium hydroxide was chose to pretreat the cotton stalk,and using ethanol-assisted sulfate cooking to get the cotton stalk pulp with high yield and low lignin content.In order to meet the standard of dissolving pulp,acetic acid was used in post-processing and bleaching was applied finally.It provides a theoretical and technical reference for the fibers separation of lignocellulosic biomass and the preparation of high quality pulp.Firstly,the performances of organic acids?formic acid and acetic acid?,alcohol,alkalis or alcohol-assisted alkalis in terms of removing hemicellulose,lignin and ash of the whole cotton stalk.Among all these pretreatment chemicals,organic acid pretreated cotton stalk showed lowest ash content,while samples treated with sodium hydroxide?NaOH?and ethyl alcohol showed comparable ash contents with significantly lower lignin and hemicellulose levels with a consequent proportion increase in the content of alpha cellulose,indicating it effectively removes hemicellulose and lignin fraction from the biomass.Based on the highest efficiency,parameters of NaOH and ethyl alcohol pretreatment were optimized,results indicated that a maximum hemicellulose and ash extraction was achieved at 3wt%NaOH loading,12wt%C₂H₅OH loading,liquid/solid ratio of 10:1,80min,50?temperature.The yield is 76.5%,and the content of hemicellulose,lignin and ash was decreased by 92.1%,20.3%and 37.7%,respectively.Secondly,ethanol-assisted sulfate cooking was used to pulping,through orthogonal experiment the optimum conditions for the process was established:ethanol concentration 5%,alkali charge 22%,liquid/solid ratio 20:1,cooking temperature 160?,150min.And the yield of pulp is 48.7%which is10.8%higher than that of the traditional sulfate method.And the removal of lignin reached 66.9%.As cotton stalk has much lignin and ash,then the pulped cotton stalk was subjected to the post processing with acetic acid to decrease ash and the residual lignin content further.And the optimized condition was established at 12wt%acetic acid loading,120min treating time,liquid/solid ratio 8:1,and 100?temperature using orthogonal experiment.The yield of cotton stalk was 73.9%and the removal of ash was 89.8%.Lastly,after bleaching with H₂O₂ and ClO₂ experiments,the yield of final dissolving pulp of cotton stalk was 84.6%,?-cellulose 92.41%,acid insoluble lignin 1.05%,pentosane 1.39%,ash 0.06%,intrinsic viscosity 430.6,the degree of polymerization 592.4,and the whiteness is89.27%ISO.The dissolving pulp of cotton stalk was then dissolved and its rheological property was measured to preliminarily test its spinnability.