Ultrasound-assisted adsorption of paraquat herbicide from aqueous solution by graphene oxide/ mesoporous silica

Abstract

In the present study, the graphene oxide (GO) nanosheets /mesoporous SiO2 nanocomposites were prepared from graphene oxide without any surfactant. The obtained GO/SiO2 was synthesized through a simple two-step reaction, including modified Hummer's method and sol-gel route using a mixture of tetraethylorthosilane (TEOS). The as-synthesized GO/SiO2 composite was characterized by FE-SEM, EDS, XRD, FTIR, BET and element mapping. The as-synthesized GO/SiO2 composite used as an adsorbent to remove herbicide paraquat (PQ) from aqueous solution by ultrasound-assisted. To investigate the influence of various variables including initial concentration of PQ, pH and mass of adsorbent in batch experiments based on CCD. The equilibrium data were better explained by Langmuir isotherm model and adsorption capacity of GO/SiO2 from Langmuir model was 31.34 mg g−1. The exothermic enthalpy change of −48.791 kJ mol−1 and the results indicated the spontaneous nature based on negative Gibbs free energy change for adsorption of PQ by GO/SiO2. The presence 0.1 M of NaCl, Na2CO3 and KNO3 salt in aqueous solution have a significant effect on the adsorption of PQ.