Using Lignin To Construct Iron-zinc Oxide/carbon Composite Material And Its Performance Exploration

Biomass lignin material is a class of aromatic-based compound and is abundant in plants,which is considered as a promising renewable resource.Every year,paper industries in the world produce a large amount of industrial-lignin by-products in the production process.At present,the technique to efficiently utilize lignin still remains rare and challenging.Simple burning or direct discharge disposal not only pollutes natural environment,but also waste resource,which does not meet the strategy of wideworld sustainable development.Therefore,it is an urgent and desirable topic to develop and extend applications of industrial lignin and accomplish value-added utilization.In this thesis,sodium lignosulfonate,a by-product of paper pulping,was used as a raw material to couple with zinc and/or iron oxides.Their composites were explored for applications in photocatalytically treating wastewater and energy storage devices.The important points are shown as follows.Firstly,the amine group is introduced into sodium lignosulfonate by the Mannich reaction to form lignin amine?LA?.The newly-added amines and the original carboxyl groups of the lignin allow LA to be an amphoteric surfactant having both cationic and anionic properties.The amine-functionalized lignin was combined with Fe₃O₄ by self-assembly principle to prepare an easily separable Fe₃O₄/LA amphoteric adsorbent.The adsorption properties of Fe₃O₄/LA were investigated by using the cationic dye methylene blue?MB?and the anionic dye acid red?AR?as the target adsorption materials,as well as corresponding adsorption mechanism.The experimental results show that Fe₃O₄/LA has excellent adsorption properties for both anionic and cationic dyes.It has excellent adsorption performance for cationic dye MB under alkaline and neutral conditions,and the adsorption capacity can reach 102 mg/g.The adsorption performance of anionic dye AR is better under the acidic condition than under alkaline condition,affording the maximum adsorption capacity of 89.3 mg/g.The adsorption process of Fe₃O₄/LA on the two dyes satisfies the Freundlich adsorption isotherm model and is attributed to the pseudo second-order kinetic equation.Secondly,we explored industrial lignin to prepare photocatalyst and its application in treating wastewater.The semiconductor material ZnO was modified by using LA as a nitrogen-containing carbon source,and consequently ZnO was anchored onto Fe₃O₄/LA,which together was calcined to form Fe₃O₄/C/ZnO composite.The photocatalytic properties of ternary composite were studied.Representatively,Fe₃O₄/C/ZnO-0.5prepared with 0.5 g LA shows the best photocatalytic performance.The removal rate is as high as 99%for MB,and 97%for antibiotic drug norfloxacin?NF?under ultraviolet light.Under the visible light,our composite still maintains extremely high degradation efficiency for MB,Rhodamine B and NF.Finally,the prepared Fe₃O₄/LA was subjected to one-step activation and carbonization.Removing Fe₃O₄ by hydrochloric acid produces nitrogen and sulfur doped porous carbon?NSC?.We fabricated it into the electrode material of supercapacitor,and explored effects of different carbonization temperature and activation ratio on its energy storage performance.The optimal preparation condition was unraveled as the carbonization temperature of 700°C,and the activation ratio of mFe₃O₄/LA:mKOH?mass ratio?=3:1.The newly-synthesized NSC has a high specific capacitance,i.e,specific capacitance as high as 240.9 F at a current density of 1 A/g.