Multivariate Metal–Organic Framework/Single-Walled Carbon Nanotube Buckypaper for Selective Lead Decontamination

The search for efficient
technologies empowering the selective
capture of environmentally harmful heavy metals from wastewater treatment
plants, at affordable prices, attracts wide interest but constitutes
an important technological challenge. We report here an eco-friendly
single-walled carbon nanotube buckypaper (SWCNT-BP) enriched with
a multivariate amino acid-based metal–organic framework (MTV-MOF)
for the efficient and selective removal of Pb2+ in multicomponent
water systems. Pristine MTV-MOF was easily immobilized within the
porous network of entangled SWCNTs, thus obtaining a stable self-standing
adsorbing membrane filter (MTV-MOF/SWCNT-BP). SWCNT-BP
alone shows a moderately good removal performance with a maximum adsorption
capacity of 180 mg·g–1 and a considerable selectivity
for Pb­(II) ions in highly concentrated multi-ion solutions over a
wide range of lead concentration (from 200 to 10000 ppb). Remarkably,
these features were outperformed with the hybrid membrane filter MTV-MOF/SWCNT-BP, exhibiting enhanced selectivity and adsorption
capacity (310 mg·g–1, which is up to 42% higher
than that of the neat SWCNT-BP) and consequently enabling a more efficient
and selective removal of Pb2+ from aqueous media. MTV-MOF/SWCNT-BP was able to reduce [Pb2+] from
the dangerous 1000 ppb level to acceptable limits for drinking water,
below 10 ppb, as established by the current EPA and WHO limits. Thus,
the eco-friendly composite MTV-MOF/SWCNT-BP shows the
potential to be effectively used several times as a reliable adsorbent
for Pb2+ removal for household drinking water or in industrial
treatment plants for water and wastewater lead decontamination.