Mesoporous activated carbons synthesized by pyrolysis of waste polyester textiles mixed with Mg-containing compounds and their Cr(VI) adsorption

Magnesium acetate, magnesium oxalate and magnesium oxide were employed to prepare waste polyester textiles-based activated carbons with well-developed mesoporous structures. TG analysis was conducted to explore the pyrolysis process and pore-forming mechanism. N-2 adsorption/desorption isotherms, EA, XRD, SEM and FTIR were performed to investigate the influences of different Mg-containing compounds on the physicochemical properties of activated carbons. The results indicated that the samples prepared by two organic magnesium salts exhibited higher specific surface area and porosity than that by magnesium oxide. Diversity in pore structure, morphology and surface groups of the carbons were owing to the differences in grain size of MgO and pyrolysis pathway of Mg-containing compounds. The adsorption isotherm of Cr(VI) for the activated carbons fitted well with Freundlich model, indicating that the adsorption process accorded with the theory of multilayer adsorption. The maximum adsorption capacity of Langmuir model of the sample prepared from magnesium acetate was the highest, and the main adsorption mechanisms were confirmed as electrostatic interaction and reduction reaction.