Study On The Preparation Of Biomass Adsorbent And Adsorption Property For Dye Solution

The flax of agricultural wastes and walnut shell were used as raw material,modified with NaOH,NaOH+L-malic acid,NaOH+glutaraldehyde and citric acid,and activated with the ZnCl2 activator,to prepare a cellulose adsorbent.Those adsorbents were used to removal three aromatic methane dyes?methyl violet?MV?and malachite green?MG??.In the experiment,the affecting factors of modified concentration,time,temperature,and adsorbent dosage,adsorption temperature,time,and initial dye concentration were investigated.According to the single factor of experiments,the orthogonal test and response surface experiment were optimized the adsorption conditions.The characterization of adsorbent were studied by SEM and FT-IR.The adsorption mechanism were studied with the adsorption kinetics equation,isotherm adsorption model and thermodynamic parameters.The main results were as follows:1)Under the optimal modified condition?0.50 mol/L NaOH solution,ultrasonic power250 W,temperature 70? and 30min.?and the optimal adsorption condition?the flax dosage0.08 g,initial MV concentration 80 mg/L,temperature 40? and 100 min?,the adsorption capacity and removal rate were higher than the FW?flax waste?,improved 0.60 mg/g and2.42%compared with that of the FW,respectively.2)The adsorbent was prepared with 0.20 mol/L L-malic acid and 1.00 mol/L NaOH under the stirring temperature 40? for 100 min,which was marked as NLFW?flax waste modifying by NaOH and L-malic?.Under the optimal condition?adsorption time 100 min,temperature 50?,the adsorbent dosage 0.30 g and initial MV concentration 80 mg/L?,the adsorption capacity and removal rate of MV were 39.47 mg/g and 99.67%,respectively.Compared with the FW,the adsorption capacity and removal rate of the NLFW improved23.30 mg/g and 18.87%,respectively.3)The glutaraldehyde concentration of 0.05 mol/L and 1.00 mol/L NaOH was stirred at temperature 25? for 6 h,to prepare the adsorbent of marking as NGFW?flax waste modifying by NaOH and glutaraldehyde?.The adsorption properties were obviously better than that of the FW.With adsorbent dosage 0.20 g,initial MG concentration 100 mg/L and temperature 25?,the maximum adsorption capacity and removal rate were 33.26 mg/g and99.78%,improved 1.60 mg/g and 3.42%compared with the FW,respectively.4)Under the optimal condition?0.30 mol/L citric acid,stirring time 90 min,temperature25? and the CFW?flax waste modifying by citric acid?dosage 0.10 g,initial MV concentration 100 mg/L,adsorption time 120 min?,the adsorption capacity and removal rate were 23.75 mg/g and 95.00%,respectively.And under the optimal condition?0.50 mol/L citric acid,stirring temperature 100? and time 120 min,the CFW dosage 0.10 g,the initial MG concentration 100 mg/L,and adsorption time 120 min?,the adsorption and removal rates were 24.03 mg/g and 96.11%,respectively.5)NFW and NLFW adsorption process of MV were better with pseudo-second-order kinetic equation?R² were 0.999 and 0.999,respectively?;the NFM adsorption process of MV were accordance with the Langmuir model?R²=0.998?,the NLFW and CFW adsorption processes were more consistent with the Freundlich model?R² were 0.984 and 0.950,respectively?;the CFW and NGFW adsorption MG processes were accordance with the pseudo-second-order kinetic equation and the Freundlich model?R² were 0.999,1.000,0.971,and 0.996,respectively?.The processes of NFW adsorption MV and CFW adsorption MG were belong to spontaneous endothermic and entropy increase process.The NLFW adsorption MV and NGFW adsorption MG and CFW adsorption MV processes were spontaneous exothermic and entropy increase process.6)The results of orthogonal test on MV adsorption by NLFW showed that under the optimal combination condition of modification temperature 60?,adsorption time 120 min,the adsorbent dosage 0.50 g,and the optimal combination condition of the adsorbent dosage0.10 g,modification temperature 60?,and adsorption time 120 min,the adsorption capacity and removal rate were 39.99 mg/g and 99.99%,respectively.The verified experiment showed that the difference value between the optimal condition experiment and the orthogonal test were 0.035 mg/g and 0.129%,respectively.The model could used to study the NLFW adsorb MV dye solution.7)The experimental results of CFW adsorption MG by the response surface experiment showed that the actual values and predicted values had better linear fitting.Under the optimal combination condition?modified temperature 60?,time 60 min,and CFW dosage 0.30 g?,the adsorption capacity and the removal rate were 22.55 mg/g and 90.22%,respectively.After analyzing,the predicted values of this combination were 22.59 mg/g and 90.38%.The difference value between the experimental value and the predicted value were very small,indicating that the model could be used to predict experimental values.8)SEM characterization showed that the adsorbents of NGFW had enhanced adsorption performance and increased adsorption capacity.After modifying NaOH and glutaraldehyde,a lot of pores are formed on the surface of the NGFW and more dyes could be adsorbed.The FTIR chart showed that the flax contained a large number of-OH,-C-O-C-and-CH2-functional groups.These groups had a good adsorption function for dye solution adsorption.The shape of FT-IR adsorption peak was almost unchanged,but the intensity of the adsorption peak changed significantly,and improved the adsorption performance.9)In the range of 0.01⁰.80 mol/L of hydrochloric acid concentration,the desorption rate rose quickly.The hydrochloric acid concentration was greater than 0.80 mol/L,the desorption rate gradually balanced,the desorption rate was up to 100.08%10)Lightwave combination C₁ synergism walnut shell activated carbon on adsorption malachite green had a certain effect.The optimal adsorption conditions were activated carbon dosage 0.01 g,malachite green concentration 400 mg/L,radiation time 2.00 min.The adsorption process were more consistent with the pseudo-second-order kinetic equation?R²=0.993?,and the Langmuir adsorption isotherm equation?R²=0.992?.