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High-Affinity Detection and Capture of Heavy Metal Contaminants using Block Polymer Composite Membranes
journal contribution
posted on 2018-12-06, 14:50 authored by Yizhou Zhang, Joseph R. Vallin, Jugal Kishore Sahoo, Feng Gao, Bryan W. Boudouris, Matthew J. Webber, William A. PhillipAdsorptive 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 × 104 L m–2 h–1 bar–1) sorbent platform based on polysulfone and polystyrene-b-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., Pd2+, Cd2+,
Hg2+, Pb2+, Zn2+, Co2+, Ni2+, Fe2+, Nd3+, and Sm3+). This platform removes these metal contaminants from solution with
a sorbent capacity of 1.2 mmol g–1 [based on Cu2+ uptake]. The metal capture performance of the functionalized
membranes persists in spite of high concentrations of competitive
ions, with >99% removal of Pb2+ and Cd2+ 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 × 104 L mol–1. 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.
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binding affinitiesfeed solutionsmetal ions undermembrane-based sorbentsHigh-Affinity Detectionsaturation capacitymetal ion complexationsurface chemistrysorbent saturationsorbent capacityfluorescence quenchingbinding sitesmetal-binding terpyridine ligandspolyethylenimine brushesbreakthrough experimentshigh-affinity bindingtrace concentrationsmetal-binding ligandflow conditionssequential attachmenttransition metal ionswater suppliesBlock Polymer Composite Membranes Adsorptive membranes offermetal ion contaminantschallengeterpyridine moietyfunctionalized membranesbackground electrolytesseawater solutionssource waterspolyethylenimine brushes increasesorbent platformHeavy Metal Contaminantsmetal contaminants
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