Nanoscale zero-valent iron/silver@activated carbon-reduced graphene oxide: Efficient removal of trihalomethanes from drinking water

AC-supported nanoscale zero-valent iron composites (nZVI/AC) exhibit significant environmental implications for trihalomethanes (THMs)-contaminated water remediation. To improve the adsorption and degradation capability of AC, herein, a composite (nZVI/Ag@AC-RGO) consisting of AC, reduced graphene oxide (RGO), nanoscale zero-valent iron (nZVI), and silver (Ag) was synthesized and characterized using several techniques, such as scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy , N 2 adsorption-desorption isotherms, and X-ray photoelectron spectroscopy (XPS). The analysis of textural and morphological structures showed that a tightly-attached RGO film , amorphous iron, and weak crystal silver nanoparticles with a size of 20–30 nm were evenly immobilized on the support. Specific surface area increased by 19.12% after supporting RGO, while it decreased after supporting nZVI and Ag due to the partial blockage of micropores. The Fe surface was concurrently coated by iron oxides (Fe 2 O 3 , FeOOH) and Ag. THMs were eliminated through multilayer reaction processes. The values of the adsorption constant (K F ) of chloroform (CHCl 3 ), dichlorobromoethane (CHBrCl 2 ), dibromochloroethane (CHBr 2 Cl), and tribromomethane (CHBr 3 ) adsorbed by nZVI/Ag@AC-RGO increased by 34.4, 33.7, 81.6, and 67.3%, respectively, compared to pristine AC. THMs with more Br atoms exhibited better removal efficiency and adsorption capacity, along with a higher oxidation degree of the Fe surface. CHBrCl 2 and CHBr 2 Cl mainly decomposed into chloromethane (CH 3 Cl) and dichloromethane (CH 2 Cl 2 ), and CHBr 3 and CHCl 3 primarily degraded into dibromomethane (CH 2 Br 2 ) and CH 2 Cl 2 , respectively, along with generating Cl − and Br − . Conclusively, THMs-contaminated water could be remediated by coupling AC pre-enrichment and the reactivity of nZVI/Ag.