[Adsorption of perchlorate in water by granular activated carbon and impact factors analysis]

The adsorption of perchloric ion (ClO4-) on granular activated carbon (GAC) was studied in aqueous solution through batch experiments. The effect of pH, initial ClO4- concentration and co-existed anions on ClO4- adsorbed by GAC, adsorption kinetics and isothermal models were studied. The results show that the adsorption capacity of ClO4- on GAC decreases in the alkaline solution, and increases with the increasing initial concentration. The competitive adsorption exists between co-existed anions and ClO4- on GAC and the order of competitive effect is SO4(2-) > NO3- > CO3(2-) > H2PO4- > BrO3- approximately Cl-. The adsorption process follows pseudo-second order kinetics. The existed pore diffusion probably is the main rate-controlling step of adsorption process. In addition, adsorption of ClO4- on GAC fits the Langmuir, Freundlich and Tempkin isothermal models in the range of experimental concentration. The adsorption of ClO4- on GAC is spontaneous and exothermic, and the increase of temperature decreases the adsorption capacity. The maximum adsorption capacity is 13.00, 11.21 and 8.04 mg x g(-1) at the temperatures of 288, 298 and 308 K, respectively. Adsorption of ClO4- on GAC is favorable, but the reaction conditions, such as temperature, pH and co-existed concentration, should be controlled to improve the adsorption efficiency.