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. SiO2 encapsulated natural zeolite (SiEZ) was prepared as the adsorption material, which was characterized with TEM, SEM, XRD and BET. The adsorption capacitance of Pb2+, Cd2+, Cu2+, Zn2+, and Mn2+ over SiEZ are 186, 10.3, 12.3, 9.0, and 4.2 mg g(-1), respectively. The highest removal percentages of Pb2+, Cd2+, Cu2+, Zn2+, and Mn2+ 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 Pb2+ when five metals co-exist. SiEZ can be recycled for heavy metal removal; at the first cycle, the removal percentage of Pb2+ can reach 99%; after SiEZ is repeatedly used for four times, the removal percentage of Pb2+ can still remain 83.8%. More importantly, elemental distribution measurement technology reveals that Pb2+ and Zn2+ in SiEZ can move from SiO2 to NZ, which is helpful to understand the heavy metal transport in the composite.