Taking the desilication liquor produced during the alumina recovery of coal fly ash as raw material

mesoporous C-S-H with large specific surface area (401 m2·g-1) was prepared by using the normal precipitation method

of which the molar ratio of calcium to silicon had been controlled. The effects of initial concentration

sorbent dosage

solution pH and ionic strength on the sorption of U(Ⅵ) by C-S-H were systematically investigated

and the sorption kinetics and thermodynamics were also studied. Moreover

the performance of C-S-H on the removal of toxic metals in actual uranium-containing wastewater was evaluated. The results indicated that the transformation of calcium silicate solid in low quality to high-value-added sorbent material had been realized by controlling the synthesis condition. C-S-H of 0.75 g·L-1 still had a high sorption capacity in equilibrium at pH 2 (qe=67.9 mg·g-1)

while UO2(H2O)52+ transformed to UO2(CO3)34- in alkaline solution with high amount of CO32-

and it was not good for the sorption of U(Ⅵ) on the negative surface of C-S-H. When C-S-H dosage increased to 2-5 g·L-1

the removal efficiency of U(Ⅵ) by C-S-H could be maintained at a comparatively higher level (C[U(Ⅵ)]initial=500 mg·L-1

88.3%-93.5%). The equilibrium of the adsorption could be reached within several hours

and the process followed the pseudo-second-order kinetic model and two-stage Weber-Morris equation model. The adsorption followed Langmuir isotherm model. Ion exchange (84.6%) and surface complexation were the main mechanisms accounting for the sorption. The material exhibited a great capacity to remove U

Zn

Hg

Mn and Cd in uranium-containing wastewater. Therefore

C-S-H had great potential to become a promising material to remove the toxic metals from wastewater.