Silica oxide encapsulated natural zeolite for high efficiency removal of low concentration heavy metals in water

The removal of trace heavy metals from water is of great importance for human’s health, and it is highly desirable to develop efficient adsorption material to reach this target. SiO 2 encapsulated natural zeolite (SiEZ) was prepared as the adsorption material, which was characterized with TEM , SEM, XRD and BET. The adsorption capacitance of Pb 2+ , Cd 2+ , Cu 2+ , Zn 2+ , and Mn 2+ over SiEZ are 186, 10.3, 12.3, 9.0, and 4.2 mg g −1 , respectively. The highest removal percentages of Pb 2+ , Cd 2+ , Cu 2+ , Zn 2+ , and Mn 2+ over SiEZ can reach 99%, 98%, 98%, 98%, and 97%, respectively, at the initial heavy metals’ concentrations of 10 ppm. SiEZ is highly selective for the removal of Pb 2+ when five metals co-exist. SiEZ can be recycled for heavy metal removal ; at the first cycle, the removal percentage of Pb 2+ can reach 99%; after SiEZ is repeatedly used for four times, the removal percentage of Pb 2+ can still remain 83.8%. More importantly, elemental distribution measurement technology reveals that Pb 2+ and Zn 2+ in SiEZ can move from SiO 2 to NZ, which is helpful to understand the heavy metal transport in the composite.