The retained templates as "helpers" for the spherical meso-silica in adsorption of heavy metals and impacts of solution chemistry.

The spherical mesoporous silica (meso-silica) MCM-41 and those with different dosage of the retained templates were prepared and characterized. Particularly, effects of the retained template and its dosage on the adsorption of typical heavy metals (Cu and Cd) in the synthesized materials were investigated. The results indicated that the retained templates acted as "helpers" for the adsorption of Cu and Cd in the spherical meso-silica MCM-41, and the maximum adsorption capacities (Q) increased with the increase of the retained template dosage. The interaction between the metal ions and the cationic heads of the templates contributed to the enhancement effect due to the anions (Cl and OH) electronically adsorbed on the interface of the template micelles. Additionally, the presented results indicated that the adsorption of Cu and Cd depended on pH and high ion strength of the solution but not on the coexisted humic acid.