In this work, we successfully prepared the musselinspired polydopamine microspheres (PDA-Ms) with controllable sizes, through a facile self-oxidative polymerization method. The prepared PDA-M biomaterial with environmentally benign properties exhibits efficient lead(II) sequestration against high salts of competitive Ca(II), Mg(II), or Na(I) ions. It reveals 30 times greater than the commercial ion-exchanger 001x7 by selectivity evaluation. Kinetic results show that an exceedingly rapid lead(II) uptake can be achieved below 1 min. More attractively, the prepared PDA-Ms further exhibit the distinguished application ability with superior treated capacity of ∼42000 kg contaminated water/kg sorbent, and the effluents can be reduced from 1000 μg/L to below 10 μg/L, reaching the drinking water standard (WHO), which is equal to 200 times greater than commercial ion exchanger resin (∼210 kg) and granular activated carbon (∼120 kg). In addition, the exhaust PDA-M material can be well regenerated and repeated use using binary 1% HCl + 5% Ca(NO 3 ) 2 solution. X-ray photoelectron spectroscopy (XPS), zeta potential, and FT-IR analysis prove that such satisfactory performances can be ascribed to the following aspects (1) the well-dispersed nanoscale morphology and highly charged property will achieve the rapid adsorption and sufficient sorbent utilization. That is, the negatively-charged PDA sphere can exert the famous Donnan membrane effects for target lead(II) enrichment and diffusion enhancement; (2) the strong amine and carbonyl/hydroxyl group within the matrix can offer sorption selectivity for powerful lead(II) capture. Effective performances as well as environmentally friendly features suggest PDA-M material is a promising lead(II)-removing candidate for water remediation.
Nanocomposites for purification of
trace heavy metal to the μg/L
level remain a hard task and pressing matter, which is mainly challenged
by their stable small size (<10 nm) formation and slow ion diffusion.
To overcome these problems, we designed an engineered sub-10 nm nanocomposite
with exceptional performances in heavy metal removal, e.g., Pb. It
relies on a cooperative adsorption, originating from the fixation
of charged SO3H groups and in situ external surface deposition
of sub-10 nm ZrO2 nanocrystals over a polydopamine (PDA)
layer. Not only does the PDA interface favor the formation of stable
and active sub-10 nm ZrO2 nanocrystals, but also the external
growth of nano-ZrO2 on the PDA layer further maximizes
Zr utilization and shortens the heavy metal diffusion distance. In
addition, the charged SO3H groups of the matrix can drive
trace heavy metal ions from the bulk solution to the vicinity of absorbents
with several orders of magnitude enrichment (∼31000 times),
significantly increasing the interaction possibility between the sub-10
nm ZrO2 nanocrystals and the target heavy metals. These
hybrid adsorbents exhibited superior selectivity with a distribution
coefficient of 10500 mL/g, wide solution pH usage (∼2.0–7.0),
rapid kinetics, and satisfactory filtration performances (>99.5%
removal)
in Pb removal. A remarkable capacity of ∼7240 L water/kg sorbent
with low effluent (∼1 μg/L) was achieved in the treatment
of the contaminated river stream, and the saturated adsorbents can
be regenerated and reused with a negligible capacity loss. Our work
therefore presents a new concept and benchmark for the lead(II) adsorbent
and brings a new perspective for mitigating the problem of diverse
heavy metal contamination.
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