| Lotus stalk activated carbon (AC) was prepared from a perennial aquatic plant, Lotus stalk by H3PO4 activation and ultrasound digestion and tested for its antibiotic adsorption. Cu-impregnated and Fe-impregnated activated carbons were prepared by dipping and used for the removal of cephalexin from aqueous solutions. The effects of modification on carbon surface properties and adsorption capacities were analyzed and batch experiments were carried out to investigate their adsorption progresses and mechamisms.The preparation condition of AC was at a H3PO4 concentration of 40%, an impregnation ratio of 2:1, an impregnation time of 12 h, an activated temperature of 450℃, and an activated time of 1 h. Two modified activated carbons(AC-Cu and AC-Fe) were prepared by dipping and heating methods. The modified ACs were characterized by N2 adsorption-desorption isotherms and Fourier transform infrared spectroscopy (FTIR). The results showed that the Brunauer-Emmett-Teller surface area and average pore size of the original activated carbon were 1031.840 m2/g and 2.8677 nm, respectively. After modifying, its specific surface area decreased and the average pore size increased, but the adsoiption capacities of cephalexin incrased.The adsorption kinetics and isotherms of cephalexin (CEX) in aqueous solution were studied for AC, AC-Cu and AC-Fe. The kinetics and equilibrium data agreed well with the pseudo-second-order kinetics model and Freundlich isotherm model for all three adsorbents. Kinetic studies showed that the adsorption reached equilibrium at about 60 h. The results also showed that the adsorption capacitiesof AC-Cu and AC-Fe were larger than the capacity of AC and AC-Fe was found to be the most effective at the removal of CEX in solution, and the maximum adsorption capacity can reach to 75.1180mg/g.Furthermore, batch experiments were conducted to study the effects of pH (2.5—10.5), initial concentration of CEX (4-16mg/L), ionic strength (10-1000mM) on CEX removal. |
PDF Full Text Request