Fabrication Of Activated Carbon Derived From Polyester Fabric Wastes Based On Ferrous Salts Agents

At present,with the development of China’s economic construction,the quantity expansion of the textile industry has put great pressure on energy and resource consumption.The disposal of such a great number of textile wastes has become one of the severe challenges we have to face currently.As one of the largest output of textile wastes,polyester fabric wastes are hard-biodegraded,consist of complicated components and the traditional treatment methods have given rise to many environmental problems.However,the main recycling methods also have the disadvantages of low recycling rate,cumbersome process and high operating cost.In recent years,a novel method of utilizing textile wastes as a precursor to activated carbon using a pyrolysis-activation technique has attracted much attention.Traditional activating agents have high performance in pore-forming process,but there are concerns about their high toxicity,secondary pollution and equipment corrosion.Therefore,iron salts were used as a new-type of green environmental activating agent to the preparation of polyester textile wastes based activated carbon.According to the physicochemical properties of carbons,FeCl₂ was proved to be an excellent activator.Moreover,further investigations were also conducted in this study,such as the optimal conditions and pore-forming mechanism,which were aimed to clarify the pore-forming pathway during the pyrolysis process.Meanwhile,eriochrome black T and Cr（VI）were used as model adsorbates to evaluate the adsorption behaviors of activated carbon,which provided certain data and theoretical support for its practical application.The main results of this study are as follows:（1）Different inorganic iron salts were selected as activating agents to the preparation of activated carbons.Various characterization analyses were conducted to investigate the different characteristics in pore-forming pathway of these carbons.The results showed that FeCl₂ and FeCl₃ could increase the turbulence of graphite structure,improving the surface activity and adsorption capacity.Furthermore,C-Cl bonds were formed on the surfaces of carbon activated by FeCl₂ and FeCl₃,they also had well-developed porosity with BET surface area around 1400 m²/g,the former exhibited higher mesoporosity,larger pore size and volume,which were more conducive to the adsorption of macromolecular organic pollutants.By contrast,C-S bond cannot be detected on the surfaces of carbon activated by FeSO₄,and its pore structures might heavily depended on the Fe-species occupation and gases released during the pyrolysis,BET surface area was only 380 m²/g.Therefore,FeCl₂ was selected as an activator due to its excellent pore-forming effect.（2）FeCl₂ was used as activating agent to the preparation polyester fabric wastes based activated carbon.Derived from the single factor experiments and Box-Behnken design results,surface area response could well described by the models,the fitting degree was 91%.Activation temperature showed the most significant effect on the BET surface area of activated carbon and the optimal conditions were as follows:mass ratio of 1:1,temperature of 700°C,and activation time of 1.5 h,the predicted value of BET surface area was 1420.19 m²/g.TG-FTIR-GC/MS,TEM and XRD were provided to illuminate the synergistic pore-forming effect of Fe²⁺and Cl^-.On the one hand,Cl^-enabled the beginning of the addition reaction to form carbon chain,and then large amount of pore structures were generated by cyclization,aromatization and spatial crosslinking processes.On the other hand,Fe²⁺can effectively inhibit the generation of tars in the pyrolysis process,enhancing the carbon yield,meanwhile Fe-species were favorable for the formation of pore structure.（3）The adsorption performance of activated carbon was estimated using eriochrome black T and Cr（VI）,the result showed that the increased initial pH had a negative effect on the adsorption of these two target pollutants.The removal rate reached the maximum at pH of 2,which was closely related to the charge and surface functional groups between activated carbon and adsorbates.Based on the magnitude of R²,the adsorption of eriochrome black T followed the Langmuir model,and the maximum adsorption capacity was 450.23 mg/g,suggesting the monolayer adsorption process,which might be related to the pore-filling effect,electrostatic attraction,π-πinteraction and H-bonding.The adsorption of Cr（VI）followed the Freundlich model,the maximum adsorption capacity was 113.56 mg/g,manifesting the adsorption was based on multilayer adsorption process,which might accompany with the pore-filling effect,electrostatic attraction and reduction of functional groups.