Synthesis of Magnetic Calcium Silicate Hydrate (M-C-S-H) and Its Adsorption Behaviors of Heavy Metal Ions in Wastewater

A novel inorganic nanocomposite with excellent robustness, magnetic calcium silicate hydrate (M-C-S-H), is synthesized at extremely low cost yet presents rapid adsorption rate and superhigh adsorption capacity. Cu(II), Cd(II), Co(II) and Cr(III) can be completely removed at low M-C-S-H dosage. The adsorption processes are spontaneous, following the Langmuir adsorption isotherm model. It was found that about 72% of Cu(II), 82% of Cd(II), 84% of Co(II) and 94.5% of Cr(III) were removed by exchanging with the interlayer Ca(II) in M-C-S-H, and the rest was removed through other mechanisms including chemical microprecipitation and surface complexation adsorption facilitated by electrostatic attraction. M-C-S-H maintained well both its structure and morphology during the adsorption process. Meanwhile, good regeneration performance was also observed that the adsorption capacity of nearly 53–72% can be retained after four cycles of Cu(II) treatment. Furthermore, massive wastewater treatment was successfully carried out through a specially designed platform. All these results demonstrate that M-C-S-H is an efficient and robust adsorbent for heavy metal ions which has great application potential in aqueous systems.