Facile one-step hydrothermal synthesis of α-FeO/g-CN composites for the synergistic adsorption and photodegradation of dyes.

With the expansion of industrialization, dye pollution has become a significant hazard to humans and aquatic ecosystems. In this study, α-FeO/g-CN- (where is the relative percentage of α-FeO) composites were fabricated by a one-step method. The as-prepared α-FeO/g-CN-0.5 composites showed excellent adsorption capacities for methyl orange (MO, 69.91 mg g) and methylene blue (MB, 29.46 mg g), surpassing those of g-CN and many other materials. Moreover, the ionic strength and initial pH influenced the adsorption process. Relatively, the adsorption isotherms best fitted the Freundlich model, and the pseudo-second-order kinetic model could accurately describe the kinetics for the adsorption of MO and MB by α-FeO/g-CN-0.5. Electrostatic interaction and π-π electron donor-acceptor interaction were the major mechanisms for MO/MB adsorption. In addition, the photocatalytic experiment results showed that more than 79% of the added MO/MB was removed within 150 min. The experimental results of free-radical capture revealed that holes (h) were the major reaction species for the photodegradation of MO, whereas MB was reduced by the synergistic effect of hydroxyl radicals (·OH) and holes (h). This study suggests that the α-FeO/g-CN composites have an application potential for the removal of dyes from wastewater.