Immobilization of (Aqueous) Cations in Low pH M-S-H Cement

Incorporation of heavy metal ions in cement hydrates is great interest for the storage and immobilization toxic, hazardous, radioactive wastes using cementitious matrix. Magnesium silicate hydrate (M-S-H) a low pH alternative binder to commonly used Portland cement. Low cements have been considered as promising matrix municipal nuclear waste last decades. It however crucial assure that incorporation secondary not detrimental formation hydration products. Herein, we investigate early stages M-S-H from electrolyte solutions presence wide range cations (LiI, BaII, CsI, CrIII, FeIII, CoII, NiII, CuI, ZnII, PbII, AlIII). The final solid products obtained after 24 h characterized via powder X-ray diffraction (PXRD), attenuated total reflectance-Fourier transformed infrared spectroscopy (FTIR-ATR), elemental analysis energy-dispersive (EDX), scanning electron microscopy (SEM), high-resolution transmission (HR-TEM). In all experiments, main precipitated phase was confirmed be with ratio (total metal/Si) close one. showed strong capacity can incorporate up 30% content at without significantly delaying nucleation M-S-H. has observed Cr, Co, Fe solution prolonging growth period This related higher average metal/total material. Secondary phases co-precipitate some experiments (Fe, Pb, Ni, Zn) were also effectively trapped within Barium only element which carbonate isolated precipitates detected.