Preparation,Adsorption,and Regeneration Of Waste Polyester Textiles Derived-activated Carbon

The increasing waste textiles and untreated dye-containing water have posed great threat to the safety of environment.Activated carbon with attractive adsorption performance was prepared via a ZnCl₂ activated pyrolysis of waste polyester textiles.The preparation parameters were optimized by orthogonal experiments and single factor experiments.Activated carbon with optimal adsorption performance could be prepared by the following procedure.Waste polyester textiles were initially pretreated by soaking in 45 wt%ZnCl₂ solution.The pretreated raw material was then pyrolyzed in the nitrogen atmosphere at900 ^oC for 90 min with a ramping rate of 5 ^oC·min^-1.These as-prepared samples were systematically characterized by thermos-gravimetric analysis?TGA?,Fourier transform infrared spectroscopy?FT-IR?,X-ray diffraction?XRD?,scanning electron microscope?SEM?,transmission electron microscope?TEM?and porosity analyzer.The as-obtained activated carbon has a maximum BET surface area and a total pore volume of 1037.6 m²·g^-1 and 0.9271 cm³·g^-1,respectively.Adsorption performance of activated carbon was measured by selecting iodine?I₂?,methylene blue?MB?and phenol?PhOH?as target dyes.Experimental results showed that activated carbon has attractive performance towards adsorption of I₂,MB and PhOH.The corresponding adsorption capacity of activated carbon toward I₂,MB and PhOH is measured to be 1015.59,411.0and 296.41 mg·g^-1,respectively.Attractive adsorption performance is attributed to rich surface functional groups and abundant pore structure in activated carbon.Adsorption performance of the activated carbon was further investigated by selecting methylene orange?MO?as target dye.Experimental result shows that the dosage of activated carbon,concentration of methylene orange,temperature and time could influence the final adsorption performance.When the dosage of activated carbon is 2 g/L,the removal rate of MO solution with a concentration of 400 mg/L can reach up to 98.95%.Adsorption of MO by activated carbon is found to be an endothermic process.The adsorption capacity of activated carbon toward MO is in positive correlation to the test temperature and time.The corresponding adsorption process could be divided into three stages:rapid adsorption,slowadsorptionandadsorptionequilibrium.The adsorption/desorption equilibrium could be reached after 90 min.Further analysis revealed that the adsorption of MO by activated carbon agrees well with the monolayer adsorption model proposed by Langmuir.Further kinetic fitting indicated adsorption of MO by activated carbon could be described by the pseudo-secondary kinetics equation.In addition,the adsorption process is found to be synergetically governed by intra-particle diffusion,liquid film diffusion and surface adsorption.The regeneration of adsorbate saturated activated carbon could not only alleviate its pollution to environment but also improve the recycle efficiency.Regeneration of activated carbon was realized by the thermal pyrolysis of MO saturated activated carbon.The regeneration parameters were optimized based on regeneration efficiency and mass loss rate of activated carbon.A high regeneration efficiency of 93.41%can be realized by pyrolysis of the MO saturated activated carbon at 600 ^oC for 30 min.The corresponding adsorption capacity toward MO was measured to be 186.11 mg·g^-1.Phase and crystal structure of regenerated activated carbon is similar to its pristine stage.There are still a large number of hydrophilic functional groups on the surface of regenerated activated carbon,which was conducive to its dispersion and adsorption.The porous structure of activated carbon was well restored after the regeneration.The BET specific surface area of regenerated activated carbon was measured to be 859.24 m²·g^-1,which is about 84.24%of its original value.Activated carbon could be effectively regenerated for three times,considering the regeneration efficiency and mass loss rate.A moderate regeneration efficiency of 85.45%and adsorption capacity of 170.25 mg·g^-1 could be maintained after a third regeneration treatment.