Adsorbability characteristic of hollow SiO_2 nanospheres for heavy metal ions

The adsorbability of hollow SiO2 nanospheres of high adsorption capacity and large specific surface area for Pb2+,Cu2+,and Cr3+ ions was investigated.The absorbtion equilibrium data were fitted by Langmuir linear equation.The results show that hollow SiO2 nanospheres have high adsorption capacity for heavy metal ions,the adsorption capacities for Pb2+,Cu2+ and Cr3+ ions are 1.256,0.681,and 0.563 mmol/g,respectively.As the fitting data shown,there is a strong correlation between the adsorption capacity and ion characteristics(covalent index and charge density).The adsorption capacity increases with the increase in covalent index or decrease in charge density.The adsorption constant is related to electric field intensity of ion(effective nuclear charge),and the adsorption constant increases with the increase in effective nuclear charge of ion.This adsorption process should belong to chemisorption.The regenerated adsorbent can be reused many times.