Experimental and theoretical evidence for competitive interactions of tetracycline and sulfamethazine with reduced graphene oxides
Competitive interactions of common antibiotics (i.e. tetracycline (TC) and sulfamethazine (SMZ)) with reduced graphene oxides (rGOs) were demonstrated by batch experiments, spectroscopic analysis and DFT calculations. The sorption capacities of TC and SMZ are much higher than that of the TC single system and that of the SMZ single system. The sorption isotherms of TC and SMZ on rGOs in single- and binary-solute systems can be satisfactorily fitted by Langmuir and Freundlich models, respectively. The maximum sorption capacities of rGOs at pH 6.0 and 298 K were 219.10 mg g−1 and 174.42 mg g−1 for TC and SMZ, respectively, indicating that the rGOs presented excellent sorption performance for antibiotics. According to SEM, FT-IR, UV-vis and XPS analysis, the highly efficient sorption of TC and SMZ on rGOs was mainly due to the π–π interaction and high surface energy sites derived from defects, edges and groove areas. The DFT calculations indicated that the sorption energy of TC on rGOs (1.12 eV) was higher than that of SMZ (0.70 eV), suggesting higher sorption affinity of rGOs for TC as compared to SMZ. These findings were crucial to efficiently eliminate various antibiotics from aqueous solutions in environmental pollution cleanup.