A kinetic and equilibrium study of competitive adsorption between atrazine and Congo red dye on activated carbon: the importance of pore size distribution

A series of phenolic resin-based microporous activated carbon fibers (ACF) with different micropore size distributions were used to assess the role of pore size distribution (PSD) in the mechanism of competitive adsorption between the organic micropollutant, atrazine. and a compound larger in size, Congo red dye (CR). Batch kinetic and equilibrium experiments with the CR/atrazine system consisted of single-solute, simultaneous adsorption, CR preloading followed by atrazine contact, and atrazine preloading followed by CR contact. Based on the previous pore characterization studies and the PSD, two types of pore structures were proposed: telescopic pores and branched pores. With the telescopic pore structure, evidence is presented to support a transition from surface pore blockage to pore constriction (without loss of atrazine capacity) to direct competition for adsorption sites, with increasing average micropore size. With the branched pore structure (micropores branching off from mesopores), direct competition for adsorption sites in a fraction of the large micropores and pore constriction and pore blockage of smaller micropores were found to be important. The kinetics of adsorption was found to be important in determining the impact of simultaneous adsorption, while CR surface coverage and preloading time were the key factors controlling the impact of preloading on atrazine adsorption. (C) 2000 Elsevier Science Ltd. All rights reserved.