High-Affinity Detection and Capture of Heavy Metal
Contaminants using Block Polymer Composite Membranes
Yizhou Zhang
Joseph R. Vallin
Jugal Kishore Sahoo
Feng Gao
Bryan W. Boudouris
Matthew J. Webber
William A. Phillip
10.1021/acscentsci.8b00690.s001
https://acs.figshare.com/articles/journal_contribution/High-Affinity_Detection_and_Capture_of_Heavy_Metal_Contaminants_using_Block_Polymer_Composite_Membranes/7429856
Adsorptive membranes
offer one possible solution to the challenge
of removing and recovering heavy metal ion contaminants and resources
from water supplies. However, current membrane-based sorbents suffer
from low binding affinities, leading to issues when contaminants are
present at trace concentrations or when the source waters have a high
concentration of background electrolytes that compete for open binding
sites. Here, these challenges are addressed in the design of a highly
permeable (i.e., permeability of ∼2.8 × 10<sup>4</sup> L m<sup>–2</sup> h<sup>–1</sup> bar<sup>–1</sup>) sorbent platform based on polysulfone and polystyrene-<i>b</i>-poly(acrylic acid) composite membranes. The membranes possess a
fully interconnected network of poly(acrylic acid)-lined pores, which
enables the surface chemistry to be tailored through sequential attachment
of polyethylenimine brushes and metal-binding terpyridine ligands.
The polyethylenimine brushes increase the saturation capacity, while
the addition of terpyridine enables high-affinity binding to a diversity
of transition metal ions (i.e., Pd<sup>2+</sup>, Cd<sup>2+</sup>,
Hg<sup>2+</sup>, Pb<sup>2+</sup>, Zn<sup>2+</sup>, Co<sup>2+</sup>, Ni<sup>2+</sup>, Fe<sup>2+</sup>, Nd<sup>3+</sup>, and Sm<sup>3+</sup>). This platform removes these metal contaminants from solution with
a sorbent capacity of 1.2 mmol g<sup>–1</sup> [based on Cu<sup>2+</sup> uptake]. The metal capture performance of the functionalized
membranes persists in spite of high concentrations of competitive
ions, with >99% removal of Pb<sup>2+</sup> and Cd<sup>2+</sup> ions
from artificial groundwater and seawater solutions. Breakthrough experiments
demonstrate the efficient purification of feed solutions containing
multiple heavy metal ions under dynamic flow conditions. Finally,
fluorescence quenching of the terpyridine moiety upon metal ion complexation
offers an in situ probe to monitor the extent of sorbent saturation
with a Stern–Volmer association constant of 2.9 × 10<sup>4</sup> L mol<sup>–1</sup>. The permeability, capacity, and
affinity of these membranes, with high-density display of a metal-binding
ligand, offer a chemically tailored platform to address the challenges
that arise in ensuring clean water.
2018-12-06 14:50:50
binding affinities
feed solutions
metal ions under
membrane-based sorbents
High-Affinity Detection
saturation capacity
metal ion complexation
surface chemistry
sorbent saturation
sorbent capacity
fluorescence quenching
binding sites
metal-binding terpyridine ligands
polyethylenimine brushes
breakthrough experiments
high-affinity binding
trace concentrations
metal-binding ligand
flow conditions
sequential attachment
transition metal ions
water supplies
Block Polymer Composite Membranes Adsorptive membranes offer
metal ion contaminants
challenge
terpyridine moiety
functionalized membranes
background electrolytes
seawater solutions
source waters
polyethylenimine brushes increase
sorbent platform
Heavy Metal Contaminants
metal contaminants