Comparative study on characterization and adsorption properties of activated carbons with H3PO4 and H4P2O7 activation employing Cyperus alternifolius as precursor

Two activated carbons employing Cyperus alternifolius as precursor were produced by using two different activating agents, H3PO4 and H4P2O7 (AC-H3PO4 and AC-H4P2O7). Both of activated carbons were allowed by single-step to get carbonized at 450 °C in a muffle furnace for 1 h. Activated carbons differed with the physical structure and chemical properties which were derived from Scanning Electron Microscope, N2 adsorption/desorption isotherms and Fourier-transform infrared spectroscopy (FTIR). Batched sorption studies were performed to compare the ciprofloxacin (CIP) adsorption properties of two carbons. The results indicated that AC-H3PO4 had 1066.4 m2/g of surface area and 1.151 cm3/g of total pore volume, while AC-H4P2O7 had 1040.3 m2/g of surface area and 1.227 cm3/g of total pore volume. Moreover, AC-H4P2O7 exhibited a higher portion of mesopores than AC-H3PO4. Fourier transform infrared spectra indicated two samples had similar functional groups. For both adsorbents, the adsorption kinetics followed the pseudo-second-order model. The adsorption equilibrium data were very well represented by three commonly used isotherm model for AC-H3PO4 (Langmuir, Freundlich and Temkin equations). As for AC-H4P2O7, the adsorption isotherm models fitted the data in the order: Langmuir > Temkin > Freundlich isotherms. The thermodynamic parameters indicated that the adsorption of CIP onto both adsorbents was spontaneous and thermodynamically favorable, with exothermic nature of the adsorption of CIP onto AC-H3PO4 and endothermic nature onto AC-H4P2O7.

► H3PO4 activation is used to prepare Cyperus alternifolius activated carbon.
► H4P2O7 activation is used to prepare Cyperus alternifolius activated carbon.
► H4P2O7 activation exhibited a higher portion of mesopores than H3PO4 activation.
► Sorption kinetics, isotherms and pH-dependent adsorption behaviors are evaluated.