| Manganese is much abundant in steel products,ranking only second to the amount of ion.During the refine process of manganese,producing plenty of manganese slag and waste water containning manganese,which easily pollute the environment.The manganese is not only one of the essential trace elements for human being,but for other creatures.However,excessive manganese also has a certain toxic effects.Excessive intake of manganese for human can cause the nervous system lesions.Tetracycline is a kind of broad spectrum antibiotics.It is widely used in human therapy,veterinary drugs and feed additives,which made its production and use growing rapidly in the world.Its excessive use can cause the pollution of water and soil,so it has aroused more and more attention.Electrochemical adsorption technology is the combination of electrochemical technology and the adsorption process.With applied voltage,the target pollutants were adsorbed on the working electrode.Biomass material-Pomelo Peel was chosen as working electrode.Many studies have shown that after carbonation,pomelo peel has a 3D macroporous mesh structure.In addation,it has been widely used in super capacitor electrodes and lithium battery,and so on.Pomelo peel after carbonation was used as working electrode in our study.Composite electrode with polyaniline was obtained by cyclic voltammetry.Tetracycline antibiotic and Mn2+ were selected as target pollutant.We studied the adsorption of tetracycline and Mn2+ on carbon electrode and composite electrode at room temperature,including the factors affecting the adsorption,adsorption behavior and adsorption mechanism.The main contents are as follows:(1)The biomass materials-pomelo peel acted as the working electrode after carbonation.SEM showed that the carbon electrode has a 3D mesh structure with macropore,which is thought to improve the active surface and shorten the path during adsorption process.Composite electrode with polyaniline was prepared by cyclic voltammograms at-0.2V-0.9V.The factors affecting the combination of carbon electrode and polyaniline,such as the scanning speed,the initial concentration of aniline and the scanning segments were all studied.The results showed that a perfect composite electrode could be obtained in an electrolyte solution consisted of 0.5M H2SO4 and 0.2M aniline,under the scanning rate of 0.01V/s and the cyclings of 5.The characterizations including SEM,XRD,FT-IR and mechanical strength test all showed that polyaniline well combined with carbon electrode.In addition,the electrochemical characterizations of two electrodes,including cyclic voltammograms test and constant current charge and discharge test were also conducted.The carbon electrode showed the characteristics of electric double layer capacitors,and composite electrode demonstrated the characteristics of pseudocapacitance.The specific capacitances of composite electrode at different scan rate were significant higher than carbon electrode.At the scanning speed of 0.05 V/s,the specific capacitance of composite electrode is about three times than that of carbon electrode.(2)The carbon electrode had a good adsorption effect to Mn2+.The experimental results show that the solution pH,initial concentration of Mn2+and reaction time all had a great effect on adsorption process.The maximum adsorption rate(88.20%)was achieved after 3000s reaction with the solution pH 4.0 and the initial concentration of Mn2+was 20mg/L.Dynamic fitting results show that the pseudo-first-order kinetic model can explained the adsorption process well(R2=0.9443).This suggests that the adsorption of Mn2+on carbon electrode was mainly by physical adsorption,that was the adsorption driven by cation exchange function.Adsorption model fitting draws a conclusion that both surface diffusion and intra-particle diffusion existed in adsorption process of Mn2+,though.(3)Tetracycline antibiotic were well adsorption on the carbon electrode and composite electrode.For carbon electrode,when solution pH was 7.0,the initial concentration of tetracycline was 20mg/L,after 3000 s,the adsorption system was reached adsorption equilibrium with maximum adsorption efficiency(95.11%).While for composite electrode,the equilibrium time was 5000s,and the equilibrium adsorption rate was 92.32%.Dynamic fitting results show that the pseudo-first-order kinetics model could fitted the carbon electrode’s adsorption data well(R2=0.9991).For the composite electrode,pseudo-second-order kinetics model was more suitable for adsorption data.This suggests that,the adsorption process of tetracycline antibiotics on carbon electrode give priority to physical adsorption,while the adsorption process on composite electrode is mainly by chemical adsorption.Adsorption model fitting showed that surface diffusion and intra-particle diffusion both existed in the process of adsorption on carbon electrode and composite electrode.But the interface layer thickness of adsorption on carbon electrode is larger than that of composite electrodes,therefore,the adsorption rate of carbon electrode was faster than the composite electrode. |
PDF Full Text Request