Juncus Effusus-based Composite And Its Purification Of Persistent Organic Pollutants

With the rapid development of global economy and industrialization,environmental pollution problems have become increasingly serious.Among them,persistent organic pollutants（POPs）have become a difficult problem in the field of environmental pollution control due to their strong toxicity,wide transmission distance,long residual period and bioaccumulation.Therefore,the convenient and efficient removal of POPs from the environment has become a popular research topic.As a natural cellulose fiber material,Juncus effusus（JE）is expected to be an ideal material for gas separation and water purification due to its unique three-dimensional mesh structure and biodegradable properties.In this thesis,based on the unique interoperable porous structure of natural JE fibers,we introduced functional polymers and made structural modulation to make them possess the corresponding properties,so as to achieve the separation and purification of multi-phase POPs.Cigarette mainstream smoke（MS）was selected as the target for the study of gas-phase POPs,and a JE-based cigarette filter with high adsorption capacity was designed.The microscopic morphology,pore size distribution and physicochemical properties of the JE fiber before and after modification were systematically investigated by simple dip-coating method using polyvinylpyrrolidone（PVP）to modulate the internal pore structure and size of JE.The adsorption of polynuclear aromatic hydrocarbons（PAHs）on the JE-based cigarette filters on in mainstream smoke was investigated by changing the filling density of the JE fibers and the composition structure of the cigarette filters,and the interception mechanism was further elaborated by classical filtration principles and particle motion models.The results show that the interconnected channels and three-dimensional network structure of the JE fiber,combined with the film-forming and wetting viscosity of PVP,enable the prepared JE cigarette filters to exhibit good MS interception performance and excellent adsorption performance on PAHs.Compared with the conventional acetate cigarette filters,the filtration effect of JE cigarette filters on PAHs in MS was more significant,with a removal efficiency of 61.79%,which was22.57%higher than that of CAF filters（39.22%）.Using the oil-water mixture in liquid-phase POPs as the research object,a JE grass-based polyurethane（PU）elastic composite material was prepared based on the lipophilic and hydrophobic properties of JE itself,which can quickly absorb oil and facilitate recycling.The microscopic morphology,chemical composition,and mechanical properties of the JE fibers before and after modification were systematically investigated,and the corresponding oil-water contact angles were calculated.The effect of polymer content on the properties of JE was investigated by varying the concentration of the introduced polymer.The results showed that with the increase of PU concentration,the intrinsic porous structure of the JE fiber was gradually covered by the PU porous membrane,and the fiber thus possessed the compressive resilience performance,but the hydrophobic property was subsequently reduced.It was found that JE/PU-6 fiber has the best overall performance and can achieve efficient adsorption of many kinds of oil agents,and the adsorption amount can reach 3.7～9.6 times of its own mass.In addition,the PU-modified JE fiber has good cycling stability and can maintain high adsorption capacity and be recycled after several compression and adsorption cycles.In order to solve the problem of water pollution by solid phase dye particles during the dyeing process of ethanol-water（EtOH-H₂O）system,a carbon nanotube（CNT）/polyvinyl alcohol（PVA）/JE-based solar evaporator was prepared by layer assembly.The light absorption performance,thermal performance and affinity performance to EtOH-H₂O solution of the JE-based solar evaporator were systematically investigated.By changing the composition of the device,the structural parameters for the optimal evaporation efficiency were explored,and the evaporator with this parameter evaporated up to 2.43 kg m^-2 h^-1 of EtOH-H₂O solution,which improved the performance by about 63.1%compared to direct evaporation(1.49 kg m^-2 h^-1).The feasibility of this JE-based solar evaporator was verified by simulating the purification experiments of dye wastewater from EtOH-H₂O system,and a large-size evaporator synergistic collection device was prepared for practical application studies under natural outdoor light,with an average daily collection capacity of 6.4 kg m^-2 of clean liquid.Through the above three research elements,the separation and purification of solid,liquid and gas phase POPs by JE fiber was achieved.The corresponding modification methods were used for different types of pollutants,and the intrinsic structure and properties of the JE fibers were fully integrated to provide the corresponding purification performance,which broadened the application scope of JE fibers and provided a valuable reference for the functionalized modification of cellulose fibers.