Preparation And Application Of Polyaniline-Poly(Styrene Sulfonate)Hydrogel Based Activated Carbon

Conducting polymer has attracted much attention due to its excellent conductivity and machinability.It also has other merits,such as,designable characteristic,easily forming and low cost.Polyaniline is one of the most widely studied and applied conducting polymer.To meet the demands to the structure and property,researchers have been devoted themselves to developing polyaniline with novel structure,preferable performance and easy synthesis,aiming to diversify the categories of conducting polymer and enlarge the scopes of applications.In this thesis,we described an effective approach for the fabrication of PAn-PSS hydrogels with special microstructure.And we applied reasonably to electrochemistry field after analyzing the structure and property of PAn-PSS hydrogel.PAn-PSS hydrogels were also pyrolysed and activated to obtain activated carbons.The carbon derivatives of PAn-PSS hydrogel were detected and applied to satisfy the modern industry.The main contents and results are summarized as follows:(1)Preparation of Polyaniline-poly(styrene sulfonate)(PAn-PSS)hydrogels.PAn-PSS hydrogels were synthesized between positively-charged PAn chains and negatively-charged PSS chains.Phase diagram was plotted to systematically investigate the gelation conditions for the PAn-PSS system.The electrostatic interaction was proposed to be the origin force for the gelation of the materials.A hierarchical porous microstructure consisting of oriented ID nanofibers of about 25?35 nm was observed in the hydrogels by SEM and AFM.There existed macrospores,mesopouses and microspores.The results of FT-IR and XRD showed that both PAn-PSS hydrogels and PAn-PSS colloids were amorphous.It was investigated that a unique transformation of hydrogels to colloidal particles in alkaline solutions.PAn-PSS hydrogel exhibited a conductivity of 0.22 S/cm,while PAn-PSS displayed a conductivity of 0.10 S/cm.(2)Application of PAn-PSS hydrogels on electrochemistry.Due to the special structure and property of PAn-PSS hydrogel,it was employed as the electrode material in supercapacitor.In comparison with conventional PAn-PSS colloids,PAn-PSS hydrogels were demonstrated to possess improved capacitance performance,such as higher energy density,higher power density and better electrochemical stability.The discharge capacitances of PAn-PSS hydrogel and PAn-PSS colloid at a current density of 0.2 A/g were calculated to be 232 and 212 F/g;Several segments of cyclic voltammograms were conducted to deposit the Pt particles on the surface of PAn-PSS hydrogels.Pt particles were distributed relatively separately on the PAn-PSS hydrogel,and the size of the particles was 100 nm in average.The PAn-PSS hydrogel-Pt electrode had 19%more current density than the PAn-PSS colloid-Pt electrode.The current density at 2500 s of PAn-PSS hydrogel-Pt catalyst electrode was 0.2543 mA/cm2.(3)Pyrolysis of polyaniline-poly(styrene sulfonate)hydrogels to prepare activated carbons.PAn-PSS hydrogel powders were heated to carbonization temperature(500,600,700 and 800 0C,respectively)and maintained for 2 h in a nitrogen atmosphere.The heating rate was 5 0C/min.Then,the as-prepared carbonized materials were activated by KOH activation method.The AC500 and AC600 samples showed main pore size distribution between 2 nm and 5 nm.The main pore size distributions of AC700 and AC800 are under 1 nm.When the carbonization temperature was 600 ?,both the BET surface area(SBET)and total pore volume(Vtot)reach maximum at 3275 m2/g and 1.924 cm3/g,respectively.Furthermore,the ratios of mesoporous volume to total pore volume of AC600 samples were also remarkably up to above 70%;AC650 was also obtained by heating the PAn-PSS hydrogels to 650? and being activated by KOH.Similar to the AC500 and AC600,it possessed plenty of mesoporous structure.The BET surface area(SBET)and total pore volume(Vtot)of AC650 were 2613 m2/g and 1.873 cm3/g,respectively.The ratio of mesoporous pore volume to total pore volume of AC650 was about 54%.The ratio of pyridinic nitrogen,amino nitrogen,pyrrolic nitrogen and quaternary nitrogen was 0.6:1:0.86:0.73 according to the result of XPS analysis.(4)Adsorption of middle toxin and mini toxin on PAn-PSS hydrogel based activated carbon.AC500,AC600,AC700 and AC800 showed VB12 equilibrium adsorption of 983,587 and 452 mg/g,respectively,at 37 ?.Comparing with Freundlich equation,Langmuir equation was more suitable to fit the data of adsorption.The correlation coefficients R2 are all more than 0.998.The adsorption capacities for AC500,AC600,AC700 and AC800 are 56.46%,97.1%,37.2%and 24.3%.The adsorption rate of AC600 can reach 72.9%within 1 h.The kinetic process of VB12 on AC500,AC600,AC700 and AC800 samples were in a more favorable agreement with the pseudo second order model than with pseudo first order model or intraparticle diffusion kinetic models,suggesting chemical interaction plays a decisive role in the adsorption rate;In comparison with the coconut shell activated carbon particles,AC650 showed a better(P<0.05,statistically)adsorption ability of 341.2 mg/g.Freundlich model was employed to describe the isothermal adsorption behavior of creatinine on AC650.The coefficient of determination(R2)was greater than 0.98,showing that creatinine is easy to be adsorbed on the AC650 surfaces.The study of the adsorption kinetics showed that the equilibrium condition of creatinine adsorption on AC650 can be reached within 7 h and can reach a higher adsorption ratio of 53.7%than the coconut shell activated carbon.The adsorption equilibrium time of creatinine is in proximity to the residence time of food in gastrointestinal,which meets the requirement of pharmacokinetics.Kinetic adsorption data were well fitted according to the pseudo-second-order model,the R2 of which was 0.9994.(5)Preparation and application of PAn-PSS hydrogel based activated carbon composite.AC600-PAn composite was synthesized by in-situ polymerization.IR,TG-DTG and XPS were utilized to analyze the property of the composite.The results indicated that the composite had little mass loses and preferable thermal stability.It also had certain level of proton doping.Cyclic voltammograms and other tests were employed to examine the AC600-PAn composite.It showed a good capacitance performance and rate capability due to the synergy effect of double-layer capacitance of AC600 and the Faraday capacitance of the PAn.At the current densities of 0.5 A/g,1 A/g,2 A/g and 5 A/g,the discharge capacitances were calculated to be154.8,148.4,142.8 and 132 F/g,and the energy densities were calculated to be 21.5,20.6,19.8 and 18.3 Wh/kg.