Efficient Heavy Metal Removal from Water by Polydopamine Confined ZrO2 Nanocrystals with Improvements in Nanoparticles Utilization and Ion Diffusion

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 SO 3 H groups and in situ external surface deposition of sub-10 nm ZrO 2 nanocrystals over a polydopamine (PDA) layer. Not only does the PDA interface favor the formation of stable and active sub-10 nm ZrO 2 nanocrystals, but also the external growth of nano-ZrO 2 on the PDA layer further maximizes Zr utilization and shortens the heavy metal diffusion distance. In addition, the charged SO 3 H 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 ZrO 2 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.