Comparative study on characterization of activated carbons prepared by microwave and conventional heating methods and application in removal of oxytetracycline (OTC)

The paper presents advantages and limitations of microwave heating in preparation of lotus stalk-based activated carbon by comparing the characteristic and adsorption properties of carbons with microwave (Mic-LSAC) and conventional (LSAC) heating methods employing H3PO4 as chemical agent. Mic-LSAC was produced with radiation power of 700 W and radiation time of 15 min. LSAC was allowed by single step to get carbonized at 450 °C in a muffle furnace for 1 h. Both produced carbons showed typical Type IV nitrogen adsorption isotherms. Mic-LSAC had large surface area of 1434 m2/g and micropore volume of 1.337 cm3/g, while LSAC had surface area of 1220 m2/g and micropore volume of 1.191 cm3/g. Moreover, Mic-LSAC had higher portion of mesopores than LSAC. Boehm's titration results and Fourier transform infrared spectra indicated that Mic-LSAC possessed smaller acidic oxygen functionalities. Mic-LSAC had higher pHpzc, more ordered stacking of layer compared to LSAC. For both adsorbents, the adsorption kinetics followed the pseudo-second-order model and the adsorption equilibrium data were very well represented by the Langmuir isotherm. The maximum adsorption capacities obtained at pH 2.80 were 564.97 mg/g and 537.63 mg/g for Mic-LSAC and LSAC, respectively. The differences of textual and chemical characteristics caused by heating method were related to adsorption capacity.

► Microwave heating is used to prepare lotus stalk-based activated carbon. ► Conventional heating is also used to prepare lotus stalk-based activated carbon. ► The different properties between these two kinds of carbons are compared. ► We correlate the properties of carbons with the ability to adsorb oxytetracycline.