Preparation Of Activated Carbon From Cattail Fiber And Its Study Of The Adsorption Properties Of2,4-dichlorophenol And2,4,6-trichlorophenol

An effective activated carbon was prepared from Cattle fiber by phosphoric acid activation. Based on the physicochemical characterization, its adsorption ability to remove the chlorophenols from water was evaluated. Desorption studies were examined in further elucidating the mechanism of adsorption and the feasibility of regenerating the spent activated carbon.By orthogonal test, the best preparation condition of CFAC was at a H3PO4concentration of40%, an impregnation ratio of2.5:1, an impregnation time of12h, an activated temperature of400℃, and an activated time of1h.BET, SEM, FTIR, elementary analysis and point of zero charge (PZC) titration methods were used to characterize physicochemical properties of CFAC. Results showed that a heterogeneous structure in terms of both size and shape was highly developed and widely distributed on the carbon surface. The Brunauer-Emmett-Teller surface area was890m2/g, and its average pore size of the activated carbon was3.88nm, indicating a mesoporous structure. After phosphoric acid activation, the concentration of C is much higher than the raw material. Some groups were formed on the carbon surface, and the carboxyl and phenolic groups were the major oxygen-containing functional group. And the PZC of the carbon is5.13.In order to verify the adsorption capacity of CFAC to2,4-DCP and2,4,6-TCP, the effects of experimental parameters such as initial concentration, contact time, pH and temperature on the adsorption were investigated. The adsorption kinetics and thermodynamics were also discussed. The result of adsorption experiment showed that CFAC could effectively remove2,4-DCP and2,4,6-TCP, with the adsorption capacities of142.86mg/g and192.31mg/g, respectively. The result showed that the acidic concentration was beneficial to the adsorption process. Comparing to2,4-DCP, the adsorption of2,4,6-TCP is more susceptible to the effect of pH. This is due to the difference between the adsorbates. The adsorption kinetics was best represented by the pseudo-second-order kinetic model, indicating a chemical adsorption process. The Intraparticle diffusion model curves reflect the different stages of the adsorption process:chlorophenol molecules first gathered quickly through the liquid film on the activated carbon surface; and then through the pore into the interior; with the increase of the adsorption capacity, the internal diffusion resistance increases, the diffusion rate declining, and ultimately achieve adsorption equilibrium. This indicates that the intraparticle diffusion was not the only rate limiting step. Other kinetic processes were simultaneously occurring and contribute to the adsorption mechanism. Comparing with the Langmuir and Tempkin isotherms models, the equilibrium adsorption data was well described by the Freundlich model. Thermodynamic study showed that the adsorption was a non-spontaneous, exothermic process.The regeneration study showed that the thermal treatment was an effective method to regenerate the exhausted carbon, and the regenerated carbon still has greater adsorption capacities.