Excellent adsorption of orange acid II on a water fern– derived micro- and mesoporous carbon

Abstract The present research has been focused on preparation, characterization and acid orange adsorption behavior of a porous activated carbon derived from water fern. Several basic and acidic activation including green approaches have been applied for the activation process. The prepared activated carbons were characterized using X-ray diffraction (XRD), differential thermal and thermal gravimetric analyses (DTA/TGA), Raman, Fourier transform infrared and X-ray photoelectron spectroscopy (FTIR), N 2 sorption and high-resolution transmission electron microscopy (HR-TEM). XRD and Raman spectroscopy results confirmed the successful preparation of carbon with good crystallinity from all of the activation processes. These results confirmed that the prepared carbons from acidic approaches have better crystallinity. The obtained activated carbon with citric acid as a green activator can approximately be considered as microporous carbons with surface area and micropore volume of 617 m 2  g −1 and 0.2 cm 3  g −1 , respectively. Maximum total pore volume and specific surface area of 0.74 cm 3  g −1 and 1437.6 m 2  g −1 , was achieved for NaOH basic activation approach. The ability of the NaOH prepared activated carbons was investigated for removing acid orange II as an anionic adsorbate from aqueous solutions. Results showed that the adsorption follows the Langmuir theory and the adsorption capacity and energy were 666.6 mg g −1 and 14.9 kJ mol −1 , respectively. A large amount of surface area and micro-porosities in the synthesized porous carbon, oxygen-containing functional groups and bridging effect of sulfur was explained as the reasons for this excellent adsorption behavior.