Synthesis of N-doped Carbon Xerogel (N-CX) and its Applications for Adsorption Removal of Microcystin-LR

Abstract

N-doped carbon xerogel (N-CX) is synthesized and used for adsorption removal of microcystin-LR (MC-LR) from aqueous solution. Characterizations including N<inf>2</inf> physisorption, TEM and XPS indicate that N atoms are doped into the N-CX and the material has porous structure. Adsorption tests show that the N-CX is efficient for MC-LR adsorption, with adsorption capacity of 1916.2 μg g^-1, which is higher than that of commercial activated carbon (1034.13 μg g^-1) and graphene oxide (1700 μg g^-1). The material is recyclable after desorption treatment by washing with NaOH solution, with no loss of uptake within five cycles. Effect of initial MC-LR concentration, temperature, and pH on the adsorption behavior is further investigated, to realize the adsorption process, showing that the adsorption process obeys the Langmuir isotherm and pseudo-second-order equation. Thermodynamical calculation indicates that the adsorption of MC-LR onto N-CX is a spontaneous and exothermic process, with the Gibbs free energy (ΔG) of -16.1 kJ mol^-1 and enthalpy (ΔH) of -18.45 kJ mol^-1.