Activated carbon coated palygorskite as adsorbent by activation and its adsorption for methylene blue

An activation process for developing the surface and porous structure of palygorskite/carbon (PG/C) nanocomposite using ZnCl2 as activating agent was investigated. The obtained activated PG/C was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (SEM), and Brunauer–Emmett–Teller analysis (BET) techniques. The effects of activation conditions were examined, including activation temperature and impregnation ratio. With increased temperature and impregnation ratio, the collapse of the palygorskite crystal structure was found to accelerate and the carbon coated on the surface underwent further carbonization. XRD and SEM data confirmed that the palygorskite structure was destroyed and the carbon structure was developed during activation. The presence of the characteristic absorption peaks of CC and C–H vibrations in the FTIR spectra suggested the occurrence of aromatization. The BET surface area improved by more than 11-fold (1201 m2/g for activated PG/C vs. 106 m2/g for PG/C) after activation, and the material appeared to be mainly microporous. The maximum adsorption capacity of methylene blue onto the activated PG/C reached 351 mg/g. The activated PG/C demonstrated better compressive strength than activated carbon without palygorskite clay.

Graphical abstractWe successfully prepared a kind of activated-carbon-coated palygorskite absorbent by ZnCl2 activation. The BET surface area improved to more than 11-fold high after activation. The maximum adsorption capacity of methylene blue onto the activated carbon coated with palygorskite reached 351 mg/g. The adsorbent also had better compressive properties than activated carbon implying the potential application as block adsorbent in waste treatment industries.Figure optionsDownload full-size imageDownload as PowerPoint slide