Synthesis of NaA-zeolite microspheres by conversion of geopolymer and their performance of Pb (II) removal

A simple and sustainable preparation process for converting metakaolin-based geopolymers into NaA-zeolite microspheres (NaA-ZMs) via suspension dispersion method under mild condition was explored. Then NaA-ZMs used for static and dynamic Pb (II) removal. The maximum adsorbed amount (Q(max)) and removal rate (R-max) of the static removal were 584 mg/g and 99.99% respectively. The Q(max) and R-max of the dynamic removal were 880 mg/g and 74.5% respectively. It could be concluded that NaA-ZMs could be excellent Pb (II) adsorbents whether in the static or the dynamic removals. Because the ions exchange between Na (I) and Pb (II) is the main removal mechanism, the morphology of NaA-ZMs damaged slightly after Pb (II) adsorption. Moreover, the specific surface area, average pore diameter and pore volume of the NaA-ZMs between before and after Pb (II) adsorption changed from 3.82 m(2)/g, 4.62 nm and 0.004 cm(3)/g to 163.79 m(2)/g, 2.42 nm and 0.099 cm(3)/g, respectively.

Automated summary

This study successfully converted metakaolin-based geopolymers into NaA-zeolite microspheres for static and dynamic Pb (II) removal. The NaA-ZMs showed excellent Pb (II) adsorption performance in both static and dynamic removals. The morphology and pore structure of the NaA-ZMs slightly changed after Pb (II) adsorption.