Engineering the Performance and Stability of Molybdenum Disulfide for Heavy Metal Removal.

Molybdenum disulfide (MoS 2 ) has recently emerged as one of the most promising water nano-based adsorbent materials for heavy metal removal with the potential to provide an alternative to conventional water decontamination technologies. In this study, we demonstrate the trade-off between mercuric removal capacity and overall MoS 2 adsorbent stability, both driven by MoS 2 synthesis parameters. A bottom-up hydrothermal synthesis setup at various growth temperatures was employed to grow flower-like MoS 2 films onto planar alumina supports. A thorough material characterization suggests that an increase in growth temperature from 150 to 210 °C results in higher MoS 2 crystallinity. Interestingly, elevated growth temperatures resulted in poor mercuric removal (525 mg g -1 , K = 2.2 × 10 -3 h -1 ), yet showed enhanced chemical stability ( i.e ., minimal molybdenum leaching during exposure to mercury). On the other hand, low growth temperatures produce amorphous supported MoS 2 , exhibiting superb mercuric removal capabilities (5158 mg g -1 , K = 36.1 × 10 -3 h -1 ) but displaying poor stability, resulting in substantial byproduct molybdate leaching. Mercuric removal by crystalline MoS 2 was accomplished by adsorption and electrostatic attraction-based removal mechanisms, whereas redox reactions and HgS crystallization-based removal mechanisms were more dominant when using amorphous MoS 2 for mercury removal. Overall, our study provides essential insights into the delicate balance between MoS 2 mercuric removal capabilities and MoS 2 degradation, both related to material synthesis growth conditions. Employment of nano-enabled water treatments in general, and MoS 2 for heavy metal removal in particular, requires us to better understand these important fundamental trade-off behaviors to achieve sustainable, effective, and responsible implementation of nanotechnologies in large scale systems.