Surface characterization of polyethyleneterephthalate (PET) based activated carbon and the effect of pH on its adsorption capacity from aqueous phenol and 2,3,4-trichlorophenol solutions

A predominantly microporous activated carbon produced from polyethylenetere phthalate (PET) by physical activation (burn-off 50%) has a BET surface are a of 1170 m(2)/g and a total pore volume of 0.625 cm(3)/g. Its surface poss esses an amphoteric nature due to the oxygen functionalities present, howev er, the majority of the groups are basic. The adsorption of phenol and 2.3, 4-trichlorophenol has been studied from aqueous solution of different pH (p H=3, 11 and unbuffered) on this carbon. The adsorption mechanism depends bo th on the pH of the solutions and the pK(a) of the phenols, as the former i nfluences the surface chemistry of the carbon as well. In the case of the p henol, a competitive adsorption takes place, as the interactions are weak i n all three media investigated. The triple chlorine substitution in the 2,3 ,4-trichlorophenol significantly increases the strength of the interactions in comparison with phenol. Due to its smaller pK(a) value, in unbuffered m edium ionic interaction occurs, as has been concluded from the shape of the isotherm and the outstandingly high value of the adsorption equilibrium co nstant. Competitive adsorption takes place only in the basic media. where t he adsorption of the 2,3,4-trichlorophenol is hindered by electrostatic rep ulsion. (C) 2001 Elsevier Science Ltd. All rights reserved.