Bioregeneration of activated carbon and activated rice husk loaded with phenolic compounds: Kinetic modeling

Abstract

A kinetic model consisting of first-order desorption and biodegradation processes was developed to describe the bioregeneration of phenol- and p-nitrophenol-loaded powdered activated carbon (PAC) and pyrolyzed rice husk (PRH), respectively. Different dosages of PAC and PRH were loaded with phenol or p-nitrophenol by contacting with the respective phenolic compound at various concentrations. The kinetic model was used to fit the phenol or p-nitrophenol concentration data in the bulk solution during the bioregeneration process to determine the rate constants of desorption, k d , and biodegradation, k. The results showed that the kinetic model fitted relatively well ( R 2 > 0.9) to the experimental data for the phenol- and p-nitrophenol-loaded PAC as well as p-nitrophenol-loaded PRH. Comparison of the values of k d and k shows that k is much greater than k d . This indicates clearly that the desorption process is the rate-determining step in bioregeneration and k d can be used to characterize the rate of bioregeneration. The trend of the variation of the k d values with the dosages of PAC or PRH used suggests that higher rate of bioregeneration can be achieved under non-excess adsorbent dosage condition.