Separation Of Lignin From Residues Of Corncob Bioethanol Production And Preparation Of Nano-lignin

The increasing energy crises and environmental concerns for fossil resources have emphasized the need to produce sustainably renewable fuels.Major efforts to this issue are focused on the conversion of renewable biomass into clean fuels.Lignocellulosic materials are the most promising feedstock for generation of a renewable,carbon neutral substitute for existing liquid fuels.Inevitably,a great amount of bioethanol production residues will be produced annually in the biorefinery.However,a key point is the valorization of the lignin in bioethanol production residues.Therefore,the focus of this thesis is the separation of lignin from residues of corncob bioethanol production by a solid-liquid extraction method using alkali solution and then precipitated by sulfuric acid,and then,ultrafining the separated lignin into nano-scale lignin.Firstly,the chemical composition of the bio-residue from corncob bioethanol production was measured,then the alkali treatment of the bio-residue was investigated.Effects of alkali dosage,reaction temperature,time and solid-liquid ratio on the extraction of lignin were explored.The results show that the optimum conditions for alkali treatment:alkali dosage is 8%,reaction temperature is 80?,reaction time is 1.5h and solid-liquid ratio is 1:6,the lignin dissolution yield is 31.68%.Secondly,the lignin yield,Zeta potential,morphology and size distribution through the acidification process were investigated.The separated lignin samples were characterized by UV-Vis,FT-IR,EDS,SEM and TGA to determinate the structural and morphological features and thermal stability.The results show that the acidification temperature and final pH have great effects on aggregation behavior in the lignin aqueous solutions.The pronounced tendency of gelation of lignin occurred at low temperature,for example 25?.pH about 3.0 and temperature 65? are the suitable acidification conditions for lignin separation.The EDS and FTIR analyses suggest the lignin's impurity,which might be attributed to coprecipitated or condensed proteins.The SEM images reveal the lignin have a loose cluster form,bonded with smaller particles.Again,three mechanical methods were applied to ultrafine lignin into nanoparticles,including high shear emulsification,ultrasonication and high pressure homogenization.The prepared nanolignin was dimensionally and morphologically characterized.The results confirm that high pressure homogenization method is most efficient to prepare nanolignin.The average particle size of the nanolignin is 42.5nm,obtained by high pressure homogenization in a lOg/L aqueous solution of lignin with homogenization pressure 30MPa and time 20min.SEM images demonstrated nanolignin was sphere,with a mean particle size around 50 nm.Finally,Sodium carboxymethylcellulose(CMC-Na),dodecyl sodium sulfate(SDS)and sodium lignosulfonate were used to modify the nanolignin suspensions stability.The influences of CMC-Na,SDS and sodium lignosulfonate amount on the properties of the stability were investigated.The results indicate that sodium lignosulfonate has the best effect on stability of the nanolignin suspensions among the stablizers,Nanolignin suspensions were obtained with average particle size of 44.2 nm,and Zeta potential of-61.79 mV when the added amount of sodium lignosulfonate is 1.5%.Nanolignin suspension remains a good stability state after 14 days.