Biomass-derived 3D Network Structure Carbonaceous Aerogels Adsorbents For The High Selective Adsorption And Mechanism Of Borate Ions And Iodide Ions

Most of the adsorption-separation materials are suffering from low environmental protection performance and high price for adsorption of low concentration iodine and boron in brine.This thesis is focused on improving the separation performance with low cost by using novel biomass carbonaceous aerogel materials as iodine and boron adsorbents.These new biomass carbonaceous aerogel materials are prepared by using biomass waste which has a wide range of sources and environmentally friendly property.The adsorption behavior of adsorbent on trace boron and iodine in solution and the adsorption mechanism are comprehensively investigated.These results provide a good reference for the separation of low concentration boron and iodine in the real brine.?1?Watermelon biomass carbonaceous aerogel?WMCA?was prepared by using hydrothermal-freezing-drying method.According to the SEM images,there are a large number of 3D pore structures on the surface and inside of WMCA,which is conducive to the adsorption of WMCA.The hydroxyl and carboxyl functional groups on the surface and inside of WMCA were confirmed from the FT-IR and XPS analysis results,which are favorable for the surface modification of WMCA.?2?The I^-adsorbents of WMCA@KH-560 and WMCA@N235 were prepared by modifying WMCA with?-glycidoxypropyltrimethoxysilane?KH-560?and tris-decylalkyltertiaryamine?N235?,respectively.The SEM,XPS,FT-IR characterizations,the adsorption kinetics and thermodynamics of WMCA@KH-560 and WMCA@N235were fully studied.On the surface and interior of the WMCA@KH-560 and WMCA@N235,there are a lot of 3D network pore structures and effective functional groups which contain epoxy and nitrogen atoms.When WMCA@KH-560 is at pH¹.5and WMCA@N235 is at pH².0,they show good adsorption performance of I^-in solution with the maximum adsorption capacity of 2.35 mmol/g and 0.5 mmol/g,respectively.The adsorption kinetics results show that the adsorption rate of WMCA@N235 is fast with the adsorption equilibrium time of 2 h.The temperature has little effect on adsorption,and both these two adsorption processes fit the pseudo-second-order kinetics model and the Langmuir monolayer adsorption model well.The mechanism analysis indicates that I^-adsorption under acidic conditions is protonation.WMCA@KH-560 adsorbs I^-through the electrostatic action of epoxy group protonation and WMCA@N235 through the tertiary amine protonation.?3?The precursor KH-550@EP@NMDG was prepared by the reaction of?-aminopropyltriethoxysilane?KH-550?,N-methyl-D-glucosamine?NMDG?and epichlorohydrin?EP?.Ultrasonic reaction of WMCA with the precursor obtained WMCA@KH-550@EP@NMDG?WKEN?.The WKEN was characterized by SEM,FT-IR and XPS,and the adsorption kinetics,thermodynamics of borate were investigated.The results show that there are a lot of 3D network pore structures both on the surface and interior of the WKEN.More hydroxyl functional groups on the surface of WKEN were found compared with WMCA,which benefits the adsorption of borate.The maximum adsorption amount of borate by WKEN was obtained?1.48mmol/g?at pH⁹.5,and the adsorption kinetics showed that the adsorption equilibrium time of WKEN was 17 h.The adsorption amount decreased with the increase of temperature.The whole adsorption process fits to the pseudo-second-order kinetics adsorption model and the Langmuir monolayer adsorption model.WKEN adsorbs borate by complexation reaction between hydroxyl functional groups and borate.?4?Different types of biomass carbonaceous aerogel?Pomelo peel biomass carbonaceous aerogel PCA,Durian peel biomass carbonaceous aerogel DCA,Watermelon peel biomass carbonaceous aerogel WMCA,Carbonized pomelo Peel biomass carbonaceous aerogel CPCA,Carbonized watermelon biomass carbonaceous aerogel CWMCA?were prepared by hydrothermal-freezing-drying method and hydrothermal-carbonization method.These biomass carbonaceous aerogel adsorbents containingPCA@KH-560,PCA@N235,DCA@KH-560,DCA@N235,WMCA@KH-560,WMCA@N235,WMCA@KH-560,WMCA@N235,CPCA@KH-560,CPCA@N235,CWMCA@KH-560 and CWMCA@N235 were modified by KH-560 and N235.The characterizations of N₂ adsorption-desorption,SEM,FT-IR,et al were obtained.The comparison of adsorption performances among these adsorption materials were discussed in this thesis.The results show that the specific surface area of the carbonaceous aerogels after carbonization are significantly increased,and can be increased several times to several tens of times depending on the different raw materials.However,the active functional groups on the surface are dramatically reduced.Specific surface area and I^-adsorption capacity of biomass after carbonization are larger than that of the non-carbonized biomass carbonaceous aerogels,but the active functional groups on the surface are significantly reduced,after the carbonized carbonaceous aerogels,the loading capacity of the functional group material is better than that before carbonization,and the adsorption performance to the I^-is also higher than that before carbonization.