Adsorptive Removal Of Tetracycline And Ni(Ⅱ) By Activated Carbon Prepared From Iris Tectorum

Iris tectorum was employed as precursor to prepare activated carbon (ITAC) by H3PO4and ammonium phosphate((NH4)2HPO4,NH4H2PO4and (NH4)3PO4)activation. The activated carbons were characterized and tested for tetracycline (TC) and Ni(II) adsorption capacities. Ferric nitrate was employed to modify activated carbon (ITAC-Fe) during H3PO4activation and ability of modified activated carbon and original carbon for removal of TC was investigated. The effects of experimental parameters, such as contact time, dosage, pH, temperature and ionic strength on the adsorption performance were investigated. The adsorption kinetics and thermodynamics were used to analyze the adsorption process and explored adsorption mechanisms.The activated carbons before and after modification were characterized and the results showed that mixing with iron increased the BET surface area, total pore volume and the adsorption capacity as compared to the original carbon. FTIR and Boehm’s titration suggested that ITAC-Fe was characteristic of more acidic functional groups than ITAC. Adsorption of TC on both samples exhibited a strong pH-dependent behavior and adsorption capacity reduced rapidly with the increasing solution pH. The surface area and total pore volume of AC-(NH4)3PO4were much higher than AC-(NH4)2HPO4and AC-NH4H2PO4, while AC-(NH4)2HPO4had largest micropore volume ratio. Boehm’s titration results suggested that AC-(NH4)2HPO4possessed more acidic functional groups than AC-NH4H2PO4and AC-(NH4)3PO4. The ionic strength had a strong influence on adsorption and adsorption capacity reduced rapidly with the increasing ionic strength. The three samples had a large adsorption capacity for Ni(II) and are excellent adsorbents.The adsorption capacity of activated carbon increased after modification and the maximum adsorption capacity for TC increased from of625.25mg/g to769.03mg/g. The maximum Ni(II) adsorption capacities of AC-(NH4)2HPO4(40.00mg/g) was higher than that of AC-NH4H2PO4(38.61mg/g) and AC-(NH4)3PO4(34.60mg/g). The adsorption kinetics for TC and Ni(II) agreed well with the pseudo-second-order model and the adsorption isotherms data were well described by Langmuir model. The intra-particle process was not the only control step and the adsorption process was also influenced by other factors. Thermodynamics results indicated that the Langmuir isotherm equation can better describe the adsorption isotherms. The adsorption process of Ni(II) was a spontaneous and endothermic process.