| Lignin is the sole aromatic compound that can be obtained from renewableresources. Because it is inexpensive and non-toxic, the potential of exploitation andvalue is endowed. Currently, the lignin has not been utilized fully, but it is used as asource of fuel or discharged without any treatment process, which caused consequentheavy waste of resources and severe pollution of environment. So how to makehigh-value use of this natural polymer has important practical significance andeconomic benefits. In this paper, in order to take advantage of high-value lignin,preparation methods and synthesis mechanism of four types lignin-based quaternaryammonium type anion adsorbent are discussed, and the physicochemical propertiesand adsorption performance of the adsorption are also discussed in detail.Firstly, the lignin was used as the matrix, and the lignin-based quaternaryammonium type anion adsorbent was produced in DMF solution and NaOH aqueoussolution respectively.In DMF solution, lignin-based quaternary ammonium type anion adsorbent(D-LQA) was produced with pyridine as catalyst, and the mechanism of its synthesiswas investigated and analyzed. The L9orthogonal experiment was designed to find theoptimal synthesis reaction parameters which were lignin: pyridine: triethylamine=2g:3mL:12mL. The optimal experimental temperature was70℃, and the reaction timewas7h. The yield was188.6%and the nitrate removal was91.2%. And verify thereaction temperature is the main influencing factors.NaOH solution is not only environmentally friendly but also has a good economy.In NaOH solution, lignin-based quaternary ammonium type anion adsorbent (CS-LQA)was produced without catalyst, and the mechanism of its synthesis was investigatedand analyzed. The impacts on the entire organic synthesis reaction which is caused byNaOH solution were discussed, and its yield was also analyzed. The result ofexperiment showed that when the NaOH concentration was6mol/L, the yield andadsorption capacity of CS-LQA were123.6%and38.3mg/g.D-LQA and CS-LQA physicochemical properties were characterized by themodern analytical testing. By31P-NMR testing, the total amount of lignin hydroxylwas6.67mol/kg and the highest conversation rate of hydroxyl was judged to be about21.9%. By infrared spectroscopy (FTIR) analyzing, D-LQA and CS-LQA structure contains a large number of positively charged quaternary ammonium groups. D-LQAand CS-LQA adsorption performance was tested and the characteristics of adsorptionthermodynamics and kinetics of the adsorption were discussed. The adsorptioncapacity (74.53mg/g) of D-LQA is higher than the commercially available adsorbentand the adsorption capacity (38.3mg/g) of CS-LQA during the average of thecommercially available adsorbent. And due to its simple preparation technology,environmentally friendly, non-toxic, and with good economic and environmentalbenefits, so it has the potential to replace the commercially available adsorbent.Finally we discussed the other two different methods to synthetic lignin-basedquaternary ammonium type anion adsorbent. First, in ethanol solvent, the absorbentwas derived with perchloric acid as catalyst under the condition of acid. Meanwhile,the influence of raw material lignin type and solvent type were discussed, and theresults show that coniferous wood alkali lignin and ethanol solution are better thanothers. Secondly, in DMF solution, lignin-based quaternary ammonium type anionadsorbent was produced after chloridizing by thionyl chloride.The adsorption capacities of sulfate, phosphate, nitrate and dichromate by usingthe two kinds of products were compared. The results show that: The first productadsorption capacity is KNO3> K2Cr2O7> NaSO4> KH2PO4. The second productadsorption capacity for NaSO4and KNO3is better, and alkali lignin adsorbent andsodium lignosulfonate based adsorbent adsorption capacity of KNO3are relativelygood, and organic extracting lignin based adsorbent adsorption effect of K2Cr2O7isrelatively good. |
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