The widespread industrial use of cobalt and its salts has raised concerns associated with its efficient removal from wastewater. In this study, a mesoporous calcium-silicate material (MCSM, 733 m(2) g(-1)) was prepared from desilication liquor of coal fly ash and examined for use in adsorbing Co(II) from aqueous solutions. At 2 g L-1 dosage, 109.6-154.8 mg of Co(II) could be removed by 1 g of MCSM in the pH 2-7 within 4 h. The effective component for sorption was found to be a layered single-chain calcium-silicate-hydrate(I), and its negatively charged surface was helpful for Co(II) sorption (PHpzc = 1.6). Before precipitation, 76.7% of Co(11) was efficiently removed via ion exchange with Ca(II) in MCSM, while the rest of Co(11) was probably adsorbed by surface complexation. The sorption followed Langmuir one-site isotherms and the kinetics was controlled by surface and intra-particle diffusion processes. Unlike conventional sorbents or ion exchangers, increasing the MCSM dosage represents a viable and economic option for improving adverse effects from practical wastewater (strong acidity, high Co(II) concentration, and high salinity). More than 98.7% of the Co(II) and metal radionuclides could be removed from the wastewater samples using 15.4 g L-1 of MCSM. The results suggest that MCSM has the potential for use as an effective and low-cost sorbent for removing Co(II), as well as related hazardous metal ions from wastewater. lifter being used as an sorbent, MCSM is suitable for use as a substitute of cement and disposed by inexpensive solidification/stabilization technique. 2015 Elsevier B.V. All rights reserved.