Study On Preparation Of Improved Biomass-based Ion Exchange Fiber And Nitrate Adsorption Property

Luffa sponge for column adsorption has many characteristics. Luffa sponge willexpands to long cylindrical when it is moist, has natural mesh structure, has strongtenacity and good biodegradable. In this study, we hope to solve the problems causedby pyridine as catalyst(fetid, difficult to clean, secondary pollution and so on) on thepremise of keeping the original size and mesh structure. At the same time, improvingthe adsorption capacity of modified luffa sponge as soon as possible. Therefore, weexpect to prepare a improved biomass-based ion exchange fiber with high adsorptioncapacity which could be used for the adsorption of nitrate nitrogen in low nitrogencontent of water.Improved biomass-based ion exchange fiber(IB-IEF) was prepared by alkalipretreatment of sodium hydroxide and the grafting of epichlorohydrin andethylenediamine onto luffa sponge fiber (LSF). Respectively from the shape of rawmaterial, concentration of alkali treatment reagent, grafting reaction in each stage ofeach reagent dosage, reaction time and reaction temperature to determine the scope ofthe levels of various factors in the orthogonal experiment. And orthogonal experimentwere performed which with2mg/l of nitrate as the adsorbate according to yield andnitrate removal as evaluation indices. The order of factors affecting and the optimumpreparation conditions were determined by the intuitive analysis of single index andmulti-index comprehensive balance analysis. Then the LSF，the alkali pretreated LSFand the IB-IEF were analyzed by modern analysis and testing technology. At thesame time, the adsorption performances of IB-IEF were tested by static adsorptiontest. Kinetics studies of adsorption and thermodynamics studies of adsorption werecarried out to find the optimum adsorption conditions. Finally the regenerationadsorption experiment was carried out. The conclusions of this study are as follows.(1) The alkali treatment is helpful to improve yield and the adsorption efficiency.The modification effect of dense luffa is better than loose luffa.(2) When triethylamine was used as the graft group, the modification effects isbetter than dimethylamine. The order of the important influencing factors for orthogonal expiration were: the second stage reaction temperature(85℃)＞the thirdstage reaction temperature（85℃）＞the dose of ethylenediamine(8ml).(3) The surface of the alkali pretreated LSF was smoother than LSF, and lots ofholes were observed on the surface of IB-IEF by SEM. It was demonstrated thatspecific surface area of LSF and IB-IEF are small by BET method. According toelemental analysis, the nitrogen content of IB-IEF was significantly higher thanLSF’s. And IR spectrums of IB-IEF and LSF demonstrated amino groups weregrafted onto IB-IEF. By XRD analysis,the order of crystallinity was: the alkalipretreated LSF＞LSF＞IB-IEF.(4) The results indicate that the range of3～10was a suitable pH values fornitrate adsorption; Product adsorption was exothermic process. The maximumadsorption capacity Qmaxwas1.348mmol/g when the temperature is20℃; The wholeadsorption process conforms to the pseudo secondary dynamics equation; Theactivation energy is2.63KJ/mol, which indicated the adsorption process was aphysical adsorption process. When the time reaches30minutes, the adsorption couldreach equilibrium;(5) The adsorption capacity of IB-IEF,which was used after5cycles ofadsorption and desorption, could still reach93%of the original adsorption capacity.