Preparation Of The Modified Lignin-Based Materials And Their Adsorption Behaviors

Lignosulfonate sodium（LS）,a kind of papermaking by-products who possesses numerous hydrophobic benzene ring and various polar functional groups in their structure,has already been used as surfactants,water adsorbents,cationic flocculants,adsorbents,and so on.However,LS is difficult to be used as an adsorption material for the treatment of industrial wastewater directly,because LS can dissolve in water easily.In this thesis,two modifying methods were designed to prepare the modified Lignosulfonate sodium based（brief name as modified lignin-based in the thesis）adsorption materials based on the laboratory previous work,and the preparation as well as the adsorption behavior of modified lignin-based to the cationic dye methylene blue（MB）have been studied.The main works are shown as following.1.Preparation of the carboxymethylated lignosulfonate sodium cross-linked polymer（CLP）was studied.Using chloroacetic acid as a modifier and epichlorohydrin（EPI）as a cross-liked agent,LS was carboxymethylated firstly and then cross-linked by EPI.Main reaction conditions which affected the carboxymethylation and cross-linked polymerization were carried out.CLP was characterized by ¹³C CP-MAS NMR spectroscopy,FTIR,SEM（EDS）,TG,and BET.Results showed that benzene ring,the basic structural units of LS,existed in CLP.2.Using carboxymethyl cellulose sodium（CMC）as the second component,the preparation of LS and CMC cross-linked copolymer（CLC）was studied.Effects of the feeding ratio of LS to CMC,reaction solvent and EPI dosage(V_EPI/m_（LS+CMC）)on Q_e of CLC to MB were investigated.Results showed that cross-linked copolymer CLC with the stable Q_e could be obtained under the conditions of the feeding ratio 2:1,EPI dosage of 2 ml·g^-1 and 50%ethanol-water as reaction solution;¹³C CP-MAS NMR spectroscopy and FTIR showed that there were both benzene ring and CMC unites in CLC.3.Adsorption properties of CLP and CLC to MB were studied systematically.Effects of ratio of solid to liquid(g·L^-1),MB initial mass concentration（C₀）,pH and adsorption temperature on the adsorption properties were investigated.Results showed both Q_e of CLP and CLC to MB increased with the increase of pH from 1 to 6;Q_e kept almost changeless when pH was over 6.Both Q_e increased firstly and then decreased with the increase of temperature within temperature from 10℃to 55℃;both maximal Q_e appeared at 25℃.The adsorption of MB onto CLP and CLC could be attributed to comprehensive effects of van der Waals′force,static attraction,hydrogen bond,electron pair sharing/transfer,π-πstacking and the like.At 25℃,using of 0.25g L^-1 loading,C₀ of 100 mg·L^-1 and pH 6.5,Q_e and removal efficiency E%of CLP to MB was 384.6 mg·g^-1 and 96.1,respectively,and that of CLC was 392.7 mg·g^-1 and98.2,respectively.When C₀ was 200 mg·L^-1,E%of CLP and CLC to MB were 89.3and 94.1,respectively.Hence,CLP and CLC can be acted as a high performance adsorption material for adsorbing MB,and the adsorption capacity of CLC to MB was better than that of CLP.In addition,co-existence of Pb²⁺in MB solution impeded the adsorption of CLP and CLC to MB.4.The study on the adsorption behaviors of CLP and CLC to MB was carried out systematically.Both adsorption isotherms followed with the Langmuir model.On the basis of Langmuir model,the maximum adsorption capacity of CLP and CLC to MB reached 813.0 mg·g^-1 and 1186.6 mg·g^-1,respectively.Both adsorption kinetics followed Pseudo-Second-order kinetic model,and both internal diffusions were not the adsorption rate-controlling step.Due to△G^?<0 in the studied range of temperature from 10℃to 55℃,the adsorption of CLC to MB was a spontaneous process.Within temperature from 10℃to 25℃,both△H^?and△S^?were positive,and the adsorption was an endothermic and entropy increasing process;Within temperature from 25℃to 55℃,both△H^?and△S^?were negative,the adsorption was an exothermic and entropy decreasing process.At beginning of the adsorption,the adsorption behavior of CLC to MB could be described by Liquid Film Diffusion mode.5.The recycling usage methods of CLP and CLC were studied.Using acetic acid-ethanol as a desorption agent,E%of CLP to MB remained about 80 after 6 cycles.Using ethanol-water as a desorption agent,E%of CLC to MB remained about 60 after6 cycles.Figure 54 table 14 reference 61...