Preparation of nZVI/MCM-41/rGO for efficient adsorption of cadmium ions from aqueous solution

Cadmium (Cd) emissions have a negative impact on both human health and the environment. Although nano zero-valent iron (nZVI) offers a lot of potential for water pollution treatment, it has been constrained by its instability and ease of aggregation. For the elimination of Cd(II) from aqueous solution, nZVI/MCM supported nZVI (nZVI/MCM-41/rGO) was designed to improve its dispersion and stability. It had a rough, porous structure with apparent Fe (0) crystallinity and slight rGO crystallinity. On the surface of nZVI/MCM-41/rGO, several oxygen-containing groups were detected. The specific surface area was 15.94 cm 2 /g, and the pore diameter was concentrated at 23.82 nm. The best performance was occurred at pH 6 with an adsorbent dosage of 2 g/L, and a maximum adsorption capacity of 31 mg/g was achieved after 600 min. Cd(II) removal process was well fitted with second-order kinetic, Langmuir and Freundlich isotherm. The thermodynamic parameter was also analyzed and proved that it was an endothermic (ΔH° > 0) and spontaneous (ΔG° < 0) progress. During adsorption, the crystal type and functional groups of nZVI/MCM-41/rGO did not change, but Fe (0) was oxidized.