Study On Deinking Of Enzyme-assisted Cardanol-based Surfactants And Application Of Deinked Pulp

With the continuous diminution of the earth's forest resources and the increasing emphasis on environmental protection,secondary fibers have become an important fiber source in the papermaking industry around the world.As an increasing category of waste paper,mixed office waste paper is playing an increasingly important role in the recycling of waste paper because of its large quantity,good quality,and low price.In this thesis,mixed office waste paper is taken as the research object,and the natural product cardanol is used as raw material to synthesize the environment-friendly surfactant cardanol polyoxyethylene ether,and it is compounded with other surfactants with good biodegradability to discuss the excellent ratio,preparation of a green and efficient deinking agent.It was applied to the traditional alkaline chemical deinking to explore its optimal deinking process.Secondly,under the neutral conditions,the composite surfactant promoted cooperative deinking process employing cutinase and amylase instead of traditional chemicals was also studied.The optimum addition amount and optimal deinking process of cutinase and amylase were discussed,and the deinking pulp was compared with traditional alkaline chemical deinking in terms of deinking pulp quality and environmental protection.In this thesis,the deinked pulp obtained by the optimal deinking process was also used as raw material,and the nanocellulose was prepared by the combination of the refining treatment-TEMPO oxidation-homogenization treatment.The influence of the amount of primary oxidant on the carboxyl content of oxidized cellulose,the yield of oxidized product,the average degree of polymerization,and the settling properties of the fiber were investigated.The morphology,size and properties of the prepared nano-cellulose were characterized.The results show that the surfactant cardanol polyoxyethylene ether?CPE?synthesized from cardanol has good biodegradability and deinking property,and there is a good relationship between the surfactant and the commercially available deinking agent.The composite surfactant with a mass ratio of CPE/AEO-9/AES 1:1:1 can be used in traditional alkaline deinking process to improve the quality of deinking pulp from mixed office waste paper,which exhibited the whiteness of 90.45%ISO,ink removal rate of 91.96%,tensile index of 19.58 N·m·g^-1,and tear index of 7.23 mN·M²·g^-1.By replacing the chemicals in traditional alkaline chemical deinking with cutinase and amylase,the neutral enzymatic deinking process can further improve the quality of deinked pulp with the whiteness of 92.24%ISO,ink removal rate of 92.63%,tensile index of 24.83N·m·g^-1,and tear index 9.48 m N·M²·g^-1.The neutral enzymatic deinking process is superior to the traditional alkaline chemical deinking process from the perspectives of deinking pulp quality,environmental protection,and production cost.The optimum process conditions for neutral enzymatic deinking are the surfactant amount of 0.2%,cutinase dosage of 10 U/g,amylase dosage of 5 U/g.The nano-cellulose with a diameter of about 10 nm and a length distribution of between100-150 nm can be successfully prepared by a combination of deinked pulp as a raw material and a pre-refining-TEMPO oxidation-high pressure homogenization process.The refining pressure is?3.33±0.1?N/mm,the refining time is 15 min;the NaClO consumption in the TEMPO oxidation stage is 6.0 mmol·g^-1;The homogenizing treatment stage uses a high pressure homogenizer model AH2010,which is cycled three times at a pressure of 300 bar and seven times at a pressure of 900 bar.