Περίληψη:
We recently discovered that a Ca2+ two-dimensional framework, namely
[Ca(H4L)(DMA)(2)]center dot 2DMA (Ca-MOF), was capable of exchanging
the Ca2+ ions with Cu2+ almost quantitatively in a matter of seconds in
aqueous solution. Herein, we report that Ca-MOF exhibits the capability
of both removal and voltammetric determination of heavy metal ions in
aqueous media. Ca-MOF shows one of the highest Pb2+ sorption capacities
(similar to 522 mg g(-1)) reported for MOFs. More importantly, a column
filled with Ca-MOF (1% wt) particles dispersed in silica sand (99% wt)
can quantitatively remove traces of Pb2+ (similar to 100 ppb) from a
relatively large volume of a wastewater simulant solution (containing a
large excess of competitive ions). Ca-MOF is also highly efficient for
sorption of Cd2+, Ni2+ and Zn2+, even in the presence of several
competitive cations. Actually, the Cd2+ sorption capacity (similar to
220 mg g(-1)) of Ca-MOF is one of the largest reported for MOFs.
Furthermore, detailed Ni2+ and Zn2+ sorption studies of MOFs have not
been described prior to this work. The mechanism of the M2+ (M2+ = Pb2+,
Cd2+, Ni2+, Zn2+) exchange process was elucidated based on a series of
spectroscopic, analytical and X-ray diffraction methods. In addition, a
simple ready-to-use electrochemical sensor based on modified graphite
paste with Ca-MOF was fabricated and successfully utilized for the
determination of Pb2+, Cd2+, Cu2+ and Zn2+ at mu g L-1 levels in aqueous
solutions by anodic stripping voltammetry (ASV). Overall, this work
demonstrates, for the first time, a dual function of a MOF as a sorbent
and as an electrochemical sensor for heavy metal ions, thus opening a
new window for materials with application in both environmental
remediation and monitoring.
