Effective adsorption of sulfate ions with poly(m-phenylenediamine) in aqueous solution and its adsorption mechanism

Sulfate adsorption by poly(m-phenylenediamine)s (PmPDs) with various oxidation states synthesized through chemically oxidative polymerization was investigated. Series of sorption experiments were conducted, and the adsorption mechanism and the relationship between oxidation state and adsorption performance were studied with the characterization of Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), pH tracking and energy calculation. The results show that the adsorption performance in acidic solution is improved with the decrease of oxidation state of poly(m-phenylenediamine) (PmPD). The rate constant is as high as 425.5 mg/(g·min) in the short equilibrium time of 30 min. The estimated highest adsorptivity of sulfate ions is 95.1%. According to the Langmuir equation, the adsorbance is 108.5 mg/g. The sulfate desorption efficiency is about 95% and the accumulative adsorbance is up to 487.95 mg/g in 5 cycles.