Preparati On Of Bagasse Cellulose/Montmorillonite Compos Ite Beads As Adsorbents For Dye Adsorption

In recent years with the rapid development of our country's economy,a number of high pollution of industrial and mining enterprises have emerged,which cause all sorts of pollution,and placed a heavy burden on the homeland on which mankind depends.To address such problems,many sewage treatment technologies have also been developed.Among them,the adsorption as a kind of advanced technology is widely used.The preparation of renewable adsorbents from agricultural and forestry wastes or clay minerals has attracted much attention.In this thesis work,two experimental studies were carried out:one was the preparation of modified bagasse cellulose and its adsorption towards amino black 10B;the other was the preparation of bagasse cellulose based composite beads and its adsorption behaviors on anionic and cationic dyes.In the preparation of modified bagasse cellulose as adsorbent for the removal of amino black 10B,the bleached bagasse pulps were employed as raw materials.Cellulose was obtained by the removal of hemicellulose and lignin,and then modified to get aminated cellulose.The materials were characterized using SEM and FTIR;and the adsorption properties of the anionic dye amino black 10B in simulated wastewater were studied.The results of SEM and FTIR characterization confirmed the effectiveness of pretreatment and amination modification.The pH value had a significant effect during dye Ab elimination.The optimal experimental conditions for the adsorption of Ab on modified cellulose were as follows:pH 2-4,the adsorbent dosage at 1 g/L,adsorption temperature 20?;and the removal rate could reach 99%.Kinetic model fitting results indicated that the adsorption process of Ab on modified cellulose accorded with pseudo-second order kinetics.Thermodynamic results showed that the adsorption process was an exothermic reaction with the decrease of entropy.The isothermal adsorption fitting results suggested that the adsorption of Ab on ACeMt was more in line with the Langmuir model.The affinity of the adsorbent on Ab was relatively large,which was preferential adsorption;and the maximum monolayer adsorption capacity was 248.14mg/g.In the preparation of bagasse cellulose matrix composite beads and the adsorption properties of anionic and cationic dyes,in view of the practical application of adsorbent in packed column,CeMt was prepared by a facile coagulation bath method,and then modified to the final product(Named ACeMt).Then ACeMt was employed for the elimination of anion and cationic dyes.The samples such as CeMt and ACeMt were characterized by SEM,FTIR,BET,XRD and TGA.The influencing factors such as pH,adsorbent dose,adsorption time and temperature were investigated;and the experimental data were also fitted with various isotherms and dynamic models.The sphericity is the best when the ratio of OMt/cellulose is 1:1.FTIR analysis showed that montmorillonite and cellulose were successfully modified.BET test indicates that ACeMt has a typical mesoporous structure;the specific surface area reached the maximum when the content of calcium carbonate was 30%;the average pore width was 3-10nm.XRD diffraction pattern shows that the cellulose is crystallization I type,and crystallinity is higher after the pretreatment;the d-spacing of montmorillonite layer was increased from 4.95 A to 5.76 A after oxalic acid modification.TGA curve showed that OMt presented a three-stage decreasing trend,demonstrating the presence of oxalic acid during pyrolysis and carbonization;and the grafting rate of oxalic acid was about 23%.The amine grafting rate of cellulose in ACeMt was about 5%.In the adsorption experiment,the optimal adsorption pH was 7,2-4 for AO and Ab,respectively.0.5g/L was selected as the optimal adsorbent dosage for both dyes.The equilibrium adsorption capacity of AO was significantly affected by temperature and increased with the increase of temperature.However,the effect of temperature on Ab adsorption was negligible;and the adsorption capacity decreased with the increase of temperature.The adsorption of both AO and Ab conforms to the pseudo-second-order kinetic model.From the perspective of mass transfer kinetics,the adsorption of the two dyes on ACeMt is mainly controlled by film diffusion,followed by pore diffusion,and finally reaches equilibrium.For isothermal adsorption,the adsorption processes of the two dyes were more consistent with the Redlich-Peterson model.The maximum adsorption capacity of ACeMt on AO was 1336.17mg/g,which is significantly higher than that of common adsorbents.The dual-component equilibrium data were best correlated with theuncompetitive Langmuir isotherm models.The ratios of Qmix/Q0 were 1.41 and 4.95 for AO and Ab,respectively,both greater than 1.Therefore,AO and Ab in the two systems showed synergistic effects in the adsorption process.The adsorption process is mainly driven by electrostatic interaction,hydrogen bonds and other intermolecular forces.