Comparative studies of sorption of phenolic compounds onto carbon-encapsulated iron nanoparticles, carbon nanotubes and activated carbon

The systematic comparative adsorption studies of three phenolic compounds (phenol, 2-chlorophenol and 4-chlorophenol) from aqueous solutions onto three types of carbon sorbents are presented. The equilibrium sorption studies along with sorption kinetics were investigated onto carbon-encapsulated iron nanoparticles, multi-wall carbon nanotubes and granulated activated carbon. These carbon sorbents have significantly different morphological and textural properties. Their surface area varied between 36 and 1187 m(2) g(-1). The highest adsorption capacity (280-550 mg/g) was found for activated carbon. The uptakes of adsorbates onto carbon nanotubes and carbon-encapsulated iron nanoparticles were substantially lower, i.e. 24-87 mg/g and 5-11 mg/g, respectively. The performed sorption kinetics studies revealed that the sorption kinetic rates for carbon nanotubes and carbon-encapsulated iron nanoparticles are 2-3 orders of magnitude larger (2-10 x 10(-2) g mg(-1) min(-1)) in comparison to activated carbon (1.9-4.5 x 10(-4) g mg(-1) min(-1)). The sorption performance and sorption kinetics were systematically discussed in the frames of morphology and textural properties of sorbents and the properties of adsorbates. Additionally, it was demonstrated that the sorption capacity of carbon nanotubes and carbon-encapsulated iron nanoparticles can be largely improved by the post-synthesis activation process. In this case the adsorption capacities increased even 2-7 times. The spent sorbents were regenerated in acetone. It was also found that carbon nanotubes and carbon-encapsulated iron nanoparticles retain up to 65% of their pristine adsorption performance, whilst the sorption capacity of activated carbon is reduced of 80%. (C) 2014 Elsevier B.V. All rights reserved.