The influence of the shape and grain size of commercial activated carbons on their sorption efficiency towards organic water pollutants

In this paper, the influence of the shape and grain size of commercial activated carbons on their adsorption efficiency towards organic water pollutants has been investigated. The powdered (L2S), granular (F300), and extruded (WG12) activated carbons were used as adsorbents, while the herbicide (2,4-dichlorophenoxyacetic acid; 2,4-D) and the pharmaceutical (paracetamol; PAR) were chosen as model water pollutants. Adsorption kinetics and adsorption at equilibrium as well as the effect of pH and ionic strength of the solution, were studied. The results showed that the adsorption kinetics followed a pseudo-second-order model and was controlled by the film diffusion. The adsorption rates of 2,4-D and PAR were influenced by both the particle size of the activated carbons tested and their porous structure. The smaller the adsorbent grains and the higher the mesopore volume, the faster the adsorption (WG12 < F300 < L2S). Adsorption at equilibrium was best described by the Langmuir isotherm and was closely related to the specific surface area of the activated carbons rather than to their grain size and shape. The adsorption capacities of L2S, F300, and WG12 were 277.8, 357.1 and 322.5 mg/g for 2,4-D, and 208.3, 250.1 and 277.3 mg/g for PAR, respectively.