Application Of Wood-based Biochar In Pervaporation Membranes

With the consumption of coal,oil and nature gas,the development of renewable clean energy was imperative,producing ethanol by biomass fermentation was get more and more attention.In order to improve the efficiency of ethanol separation,in this dissertation,Lodgepole pine bark,Larch wood,Larch bark were as raw material to prepare biochar under nitrogen at different temperatures,respectively.And then the biochar was modified at different conditions.As the adsorption properties of modified biochar,the samples were used as filler with polydimethylsiloxane(PDMS)as the matrix of composite membrane,cellulose acetate(CA)membrane as support layer,then the pervaporation(PV)composite membrane was sucessfully prepared.In a 10 wt.%ethanol/water solution,the PV performance of composite membranes were tested.The effect of different modified biochar,feed concentration,feed temperature and experimental period on PV performance of composite membrane were studied in detail.The experimental results showed that the composite membranes with deferent modified biochar particles were all alcohol permselective membranes.Compared to Larch wood and Larch powder,Lodgepole pine biochar had more residual groups,the separation performance of composite membranes with modified Lodgepole pine biochar were increased most significantly.The prepared composite membranes with different modified biochar particles are all alcohol selective.compared with larch bark and larch wood,due to contain more residual organic groups,lodgepole pine bark could be modified for improving the separation performance of composite membrane.Biochar was prepared at 300,600,and 900 ?,extracted by Soxhlet with toluene/ethanol(V:V=2:1),the biochar samples were grinded down to the nanoscale,then hydroxyl was grafted on the surface of biochar.The biochar was modified with silane coupling agent aminopropyltriethoxysilane(KH-550),therefore the hydrophobic group was introduced on the surface of biochar.The experiment results of separation factor and permeation flux were tested.The preparation conditions of PDMS/CA composite membrane filled with modified KH-550 nanoparticles were optimized by response surface methodology(RSM).The effects of preparation conditions on the PV composite membrane were investigated,including the preparation temperature,the weight ratio of KH-550/biochar nanoparticles and the adding quantity of biochar nanoparticles.20 groups of experiments were established by the statistical software Design-Expert 8.0.6,and the regression equations between the experimental variables and the response results were designed.The other 4 groups of experiments were used to confirm the experimental results.In this study,the main effect,the subordinate effect and the secondary effects of the above three variables on the permeation flux and separation factor were discussed.The silane coupling agent vinyltriethoxysilane(YDH-171)was used to modify the biochar prepared in different temperature,compared to aminopropyl of KH-550,vinyl of YDH-171 was more hydrophobic,and had better compatibility with PDMS.YDH-171 modified biochar as raw materials was used to prepare PV composite membrane.The conposite membranes had better separation performance.PDMS/CA composite membrane with modified biochar nanoparticles had excellent stablity.The feed concentration was 10 wt.%,the feed temperature was 40?,the experiment period was 168 h,the separation performance of composite membrane with YDH-171 modified biochar maintain almost constant.The phenolic resin was mixed with pine bark for two hours under the condition of 180 ?,and the sample was broken into powder and grinded and crushed down to the nanoscale by ball mill.The prepared nanoparticles had more hydroxyl groups with the addition of phenolic resin which would be more hydrophobic after modification.The modified samples were used as fillers to prepare the composite membrane.The prepared composite membrane has great separation performance in PV test.The SiO2 coated biochar nanoparticles(BCNPs)core-shell structure were prepared by sol-gel-precipitation method.The BCNPs as the filler was added into the PDMS matrix,and its pervaporation performance was tested.The experimental results showed that the ethanol separation performance was significantly improved.The possible reason is that the hydrophobic property of the biological carbon nanoparticles was improved dramaticly,and the adsorption capacity of biological carbon is retained.The performance of BCNPs was analyzed by XRD and XPS.