Adsorption of bromo-phenol blue from an aqueous solution onto thermally modified granular charcoal

Abstract

The adsorption phenomenon of bromo-phenol blue onto pristine and thermally evacuated granular charcoal (GC) was studied via a batch technique at 25 °C. The effect of evacuation temperature on the GC surface and pore structure (e.g. pore volume and diameter) was studied by Fourier transform infrared spectroscopy (FT-IR), point of zero charge (PZC), proximate analysis, Brunauer, Emmett and Teller (BET) method and field emission scanning electron microscopy (FE-SEM). The FT-IR spectra of the samples after evacuation showed considerable decrease in the acidic functional groups. PZC showed that the surface of the evacuated charcoal became basic as the evacuation temperature was increased from 300 to 800 °C. Volatile matter decreased while ash and fixed carbon contents increased during evacuation, which led to an increase in the micro-pore volume from 0.25 to 0.42 cm 3 g −1, meso-pore volume from 0.04 to 0.13 cm 3 g −1, pore diameter from 5.01 to 6.21 nm, and specific surface from 150.32 to 254.70 m 2 g −1. Adsorption of the bromo-phenol blue onto charcoal, increased as the evacuation temperature was increased from 300 to 800 °C. The interaction of bromo-phenol blue with charcoal was proposed to have occurred via hydrogen bonding. The adsorption data fitted well with the Langmuir equation, which indicated that the monolayer adsorption has occurred at specific sites within the adsorbent.