| In recent years,with the shortage of raw materials in the pulp and paper industry and the increasing public awareness of environmental protection,the recycling of waste paper has attracted more and more attention.Therefore,improving the recycling efficiency of waste paper plays an important role in solving raw materials shortage,reducing energy consumption,and protecting the environment.However,the waste paper fiber has the disadvantages of swelling ability reduce,paper strength decrease and poor water filtration performance during the process of recycling,which cannot meet the requirement of high-quality products so that severely restricts it using in the paper industry.Therefore,research the technology to improve the recycling of waste paper is needed.As an emerging technology,bio-enzyme technology has been widely used in the pulp and paper industry especially cellulase.The modification of waste paper fibers using cellulase can improve the drainage properties,bleaching properties of waste paper pulp,and improve the deinking efficiency of waste paper,thereby improving the recycling of waste paper.In this paper,the mixed office waste paper were used as the main raw material,and mixed office waste paper were treated using cellulase / aspartic acid system to improve the recycling properties of the waste paper fiber.Firstly,the physical properties of office waste paper fibers were studied treated with cellulase/aspartic acid system from the dosage of cellulase,dosage of aspartic acid,reaction temperature and reaction time.The results showed that the strength properties of cellulase/aspartic acid system treated pulp was increased.The optimum processing conditions for cellulase/aspartic acid system modified MOW were: 14.74 U/g of cellulase,2.19% aspartic acid(based on the oven dried weight of the pulp),temperature 49.0 °C,and reaction time 55.96 min.At optimum enzymatic system,the tensile index,burst index and water retention value(WRV)were increased by 16.05%,14.39%,and 36% compared to control pulp.The content of carboxyl groups increased 32.84% compared to the control pulp after modified by cellulase/aspartic acid system.After modification,the crystallinity index of the fiber was decreased by 37.58% compared to the control sample.Secondly,in view of the problem that hard deinking during the process of MOW recycling,the deinking effect of cellulose/aspartic acid system deinking MOW was studied.The deinking process condition of the enzymatic system was optimized from the aspects of cellulase dosage,aspartic acid dosage,reaction temperature,reaction time and pulp concentration.The results showed that MOW had the best deinking effect under the conditions of 15 U / g of cellulase,2% of aspartic acid,50 ° C reaction temperature,60 min reaction time,and 8% pulp consistency.Under the optimum deinking conditions,the brightness was improved by 2.2% and the effective residual ink concentration was reduced by 14.02% compared with the MOW without enzyme deinking,that is,the deinking efficiency reached 14.02%.After the cellulase/aspartic acid treatment,the O/C content of the pulp surface increased by 36.19% compared with the control.Next,to clarify the mechanism of cellulase/aspartic acid system synergistic modified laccase(C/A-ML)treatment office waste paper,the fiber morphology parameters,hydrogen bond patterns,cellulose crystallinity,and fiber microstructure were observed via fiber quality analyzer(FQA),Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),and scanning electron microscopy(SEM).The results showed that the effective residual ink concentration of enzyme deinked pulp decreased compared with untreated MOW pulp,the fiber length and curl index slightly decreased;FTIR analysis revealed that after cellulase,modified laccase,and C-M/Las treatment,the content of intermolecular hydrogen bonds O-(6)H…O-(3')increased by 14.65%,13.37%,and 19.80%,respectively;XRD analysis showed that the enzyme system treatment can reduce the fiber crystallinity and inhibit the fiber property decay;SEM micrographs of fibers treated with enzymes revealed that the fiber surface became rough and more fibrils appeared.Finally,aspartic acid,glutamic acid,histidine and glycine synergistic cellulase treatment improving office waste paper recycling properties were discussed.Under the conditions of 15 U / g of cellulase,reaction temperature 50 °C,reaction time 60 min,pulp concentration of 8% and a certain p H value of 7,the dosage of amino acid added was changed to analysis the recycling properties of office waste paper treated by different mediators synergistic cellulase.The results showed that the optimal dosages of aspartic acid,glutamic acid,histidine and glycine were 2%,3%,3% and 2%,respectively.The physical properties were studied after cellulase synergistic different mediator treatment.Compared with the control sample,cellulase synergistic different mediator treat office waste paper can improve the recycling properties. |
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