Diffusion of hydrophilic organic micropollutants in granular activated carbon with different pore sizes
Piai, Laura ; Dykstra, Jouke E. ; Adishakti, Mahesa G. ; Blokland, Marco ; Langenhoff, Alette A.M. ; Wal, Albert van der - \ 2019
Water Research 162 (2019). - ISSN 0043-1354 - p. 518 - 527.
Activated carbon - Adsorption kinetics - Hydrophilic micropollutants - Intra-particle diffusion - Pore diffusion
Hydrophilic organic micropollutants are commonly detected in source water used for drinking water production. Effective technologies to remove these micropollutants from water include adsorption onto granular activated carbon in fixed-bed filters. The rate-determining step in adsorption using activated carbon is usually the adsorbate diffusion inside the porous adsorbent. The presence of mesopores can facilitate diffusion, resulting in higher adsorption rates. We used two different types of granular activated carbon, with and without mesopores, to study the adsorption rate of hydrophilic micropollutants. Furthermore, equilibrium studies were performed to determine the affinity of the selected micropollutants for the activated carbons. A pore diffusion model was applied to the kinetic data to obtain pore diffusion coefficients. We observed that the adsorption rate is influenced by the molecular size of the micropollutant as well as the granular activated carbon pore size.
Effect of pore size distribution and particle size of porous metal oxides on phosphate adsorption capacity and kinetics
Suresh Kumar, Prashanth ; Korving, Leon ; Keesman, Karel J. ; Loosdrecht, Mark C.M. van; Witkamp, Geert Jan - \ 2019
Chemical Engineering Journal 358 (2019). - ISSN 1385-8947 - p. 160 - 169.
Adsorption kinetics - Diffusion - Particle size - Phosphate adsorption - Pore size distribution - Porous metal oxide
Phosphate is a vital nutrient but its presence in surface waters even at very low concentrations can lead to eutrophication. Adsorption is often suggested as a step for reducing phosphate down to very low concentrations. Porous metal oxides can be used as granular adsorbents that have a high surface area and hence a high adsorption capacity. But from a practical point of view, these adsorbents also need to have good adsorption kinetics. The surface area of such adsorbents comes from pores of varying pore size and the pore size distribution (PSD) of the adsorbents can affect the phosphate adsorption kinetics. In this study, the PSD of 4 different adsorbents was correlated with their phosphate adsorption kinetics. The adsorbents based on iron and aluminium (hydr)oxide were grinded and the adsorption performance was studied as a function of their particle size. This was done to identify diffusion limitations due to the PSD of the adsorbents. The phosphate adsorption kinetics were similar for small particles of all the adsorbents. For larger particles, the adsorbents having pores larger than 10 nm (FSP and DD6) showed faster adsorption than adsorbents with smaller pores (GEH and CFH). Even though micropores (pores < 2 nm) contributed to a higher portion of the adsorbent surface area, pores bigger than 10 nm were needed to increase the rate of adsorption.