Application of graphene oxide nanosheets in the coagulation-flocculation process for removal of Total Organic Carbon (TOC) from surface water

Organic compounds in aquatic environments are one of the severe concerns in water treatment plants because of their role in increasing microbial growth in water supply systems and producing toxic by-products after chlorination. In other words, Natural Organic Matters (NOMs) can react with chlorine and be transformed into compounds, which were already proven to be carcinogenic. The primary purpose of this present study is assessing the role of Graphene Oxide (GO) in coagulation-flocculation process in TOC removal and the application of Fe3O4 for enhancing sedimentation rate. The physical, chemical, and morphological properties of GO and Fe3O4 were characterized by FT-IR, XRD, DLS, FE-SEM, and VSM. The experiments were designed using Box-Behnken to study the key parameters such as pH, GO, and FeCl3 concentration on TOC and turbidity removal. At the optimized points derived from Design-Expert software, GO concentration, FeCl3 concentration, and pH were reported 18 mg/L, 36 mg/L, and 7.5, respectively. The results were analyzed by UT isotherms, Radke-Prausnitz, Temkin, Langmuir, Freundlich, and Dubinin-Radushkevich, Redlich-Peterson. Radke-Prausnitz exhibited a lower error than the others. The maximum adsorption capacity of 1608 mg/g was obtained, which is related to the Langmuir isotherm. The experiment results demonstrated that using GO and Fe3O4 has significant effects on TOC and turbidity removal rate and settlement rate in coagulation-flocculation process.