Thiosemicarbazone modified zeolitic imidazolate framework (TSC-ZIF) for mercury() removal from water

• Published in: RSC advances Vol. 11; no. 27; pp. 16192 - 16199
• Main Authors: Jaafar, Amani, Platas-Iglesias, Carlos, Bilbeisi, Rana A
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 30-04-2021; The Royal Society of Chemistry
• Subjects: Adsorption; Aldehydes; Aqueous solutions; Chemistry; Heavy metals; Imidazole; Mercury (metal); Mercury compounds; Metal-organic frameworks; Regeneration; Stability; Wastewater; Zeolites
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/d1ra02025k

Zeolitic imidazolate frameworks (
ZIF-8
), and their derivatives, have been drawing increasing attention due to their thermal and chemical stability. The remarkable stability of
ZIF-8
in aqueous and high pH environments renders it an ideal candidate for the removal of heavy metals from wastewater. In this study, we present the preparation of novel aldehyde-based zeolitic imidazolate frameworks (
Ald-ZIF
) through the integration of mixed-linkers: 2-methylimidazole (
MIM
) and imidazole-4-carbaldehyde (
AldIM
). The prepared
Ald-ZIFs
were post-synthetically modified with bisthiosemicarbazide (
Bisthio
) and thiosemicarbazide (
Thio
) groups, incorporating thiosemicarbazone (
TSC
) functionalities to the core of the framework. This modification results in the formation of TSC-functionalized ZIF derivatives (
TSC-ZIFs
). Thiosemicarbazones are versatile metal chelators, hence, adsorption properties of
TSC-ZIFs
for the removal of mercury(
ii
) from water were explored. Removal of mercury(
ii
) from homoionic aqueous solutions, binary and tertiary systems in competition with lead(
ii
) and cadmium(
ii
) under ambient conditions and neutral pH are reported in this study.
MIM
3.5
:Thio
1
:Zn
improved the removal efficiency of mercury(
ii
) from water, up to 97% in two hours, with an adsorption capacity of 1667 mg g
−1
. Desorption of mercury(
ii
) from
MIM
3.5
:Thio
1
:Zn
was achieved under acidic conditions, regenerating
MIM
3.5
:Thio
1
:Zn
for five cycles of mercury(
ii
) removal.
TSC-ZIF
derivatives, designed and developed here, represent a new class of dynamically functionalized adsorption material displaying the advantages of simplicity, efficiency, and reusability.
Zeolitic imidazolate frameworks
Ald-ZIF
were obtained by mixing two imidazole-based linkers with zinc(
ii
). Post-synthetically modified
Ald-ZIFs
with thiosemicarbazide group improved mercury(
ii
) removal efficiency from water at a capacity of 1667 mg g
−1
.