Coal gangue, a prevalent solid waste in the coal industry, has long been a significant concern due to its substantial production volume and potential environmental hazards. However, it contains valuable components such as silica and alumina, making it a promising raw material for synthesizing cementitious materials. This study focused on the synthesis of coal gangue-based magnesium silicate hydrate (M-S-H) and calcium silicate hydrate (C-S-H) through mechanical–thermal–chemical composite activation treatment. The cementitious activity of coal gangue samples and the characterization of the resulting cementitious materials were analyzed using ICP-AES, FTIR, XRD, SEM, and DSC-TG. Results indicated that calcination temperature, calcination time, the Ca/Si molar ratio, and the Mg/Si molar ratio were key factors influencing the cementitious activity of coal gangue, exhibiting a positive correlation with the dissolution amounts of Si⁴⁺ and Al³⁺. When kaolin in coal gangue was fully decomposed into active Al₂O₃ and SiO₂, the cementitious activity of coal gangue reached its peak. M-S-H and C-S-H were successfully synthesized after 7 days of curing at room temperature, significantly reducing the synthesis time. The synthesized M-S-H and C-S-H exhibited large specific surface areas, good mechanical properties, and well-developed pore structures, making them suitable as mesoporous materials that provide numerous active sites for adsorbing metal ions.

To elucidate the environmental geochemistry characteristics of groundwater in Huainan Coalfield, the largest coalfield in southern China, 59 groundwater samples from 12 locations were collected and measured for 18 heavy metals (Li, V, Cu, Pb, Zn, Cd, Ni, Mn, Co, Cr, Fe, Ba, Al, Be, Ti, Sr, Mo, and As), pH, and 7 ions (K⁺, Na⁺, Ca²⁺, Mg²⁺, Cl^–, SO₄^2–, and HCO₃^–). The Fe and Mn contents of most water samples were within class III of the People’s Republic of China Quality Standard for Groundwater. The Pb, Zn, Cd, Cr, Co, and Ba contents were assessed by the fuzzy mathematical method, and their levels in the groundwater were within class II. pH was negatively correlated with 11 heavy metals (Li, V, Cu, Pb, Zn, Cd, Ni, Mn, Cr, Ba, and Sr) and positively correlated with Al, Ti, and Co. The ranking of uptake rates affected by pH was Al > Ba > Ti > Si > Li > Mn. The Li content was correlated with six ions (Na⁺, Ca²⁺, Mg²⁺, Cl^–, SO₄^2–, and HCO₃^–), Sr was correlated with the first five ions, and Ba was correlated with the first four ions. Principal component analysis of V, As, Mn, Pb, Cd, Ni, Cr, Li, and Zn in the groundwater indicated that they derived from lixiviation of soil and rocks, precipitation, surface runoff, and surface pollution by heavy metals.