Drinking water pollution with heavy metals is a global problem with dire public health consequences. Existing water purification methods are unable to the rapid and concurrent removal of toxic metals to trace levels. Here, we introduce the new 2D hybrid LDH–[Sn₂S₆] as an unprecedented sorbent that shows highly efficient and concurrent removal of Cu²⁺, Ag⁺, Cd²⁺, Pb²⁺, and Hg²⁺ from ppm (mg/L) to ppb (µg/L) level. In mixed-ion states of Zn²⁺, Co²⁺, Ni²⁺, Ag⁺, Cu²⁺, Hg ²⁺, Pb²⁺, and Cd²⁺ (10 ppm each, 80 ppm in total), LDH–[Sn₂S₆] shows simultaneous removal of > 99.9 % of Cu²⁺, Ag⁺, Cd²⁺, Pb²⁺ , and Hg²⁺ enabling the final concentrations below 5 ppb. At this mixed-ion states, the selectivity order was obtained as Zn²⁺, Co²⁺, Ni²⁺ << Ag⁺, Cu²⁺ < Hg ²⁺ < Pb²⁺, Cd²⁺. Remarkably, LDH–[Sn₂S₆] removes over 99.0 % of Cu²⁺, Ag⁺, Cd²⁺, Pb²⁺, and Hg²⁺at pH ~ 2 to 9 preserving high distribution constant (K_d) ~ 10⁵ to 10⁷ mL/g in the entire pH range. LDH–[Sn₂S₆] shows enormous sorption capacities (q_m) of 378, 978, 332, 579 and 666 mg/g for Cu²⁺, Ag⁺, Cd²⁺, Pb²⁺, and Hg ²⁺, respectively. Strikingly, in the mixed-ion sate of Zn²⁺, Co²⁺, Ni²⁺, Ag⁺, Cu²⁺, Hg ²⁺, Pb²⁺, and Cd²⁺ in potable water (1 ppm each; ~8 ppm in total), the adsorption of Ag⁺, Cu²⁺, Hg ²⁺, Pb²⁺, and Cd²⁺ is extremely rapid. LDH–[Sn₂S₆] can simultaneously remove noxious Ag⁺, Hg ²⁺, Pb²⁺, and Cd²⁺ down to 5 ppb just in seconds, yielding the World Health Organization (WHO) defined drinkable levels. LDH–[Sn₂S₆] shows the sorption kinetics that follows a pseudo-second-order model, suggesting that chemisorption adsorption mechanisms involve through M-S bonding. Altogether, the LDH–[Sn₂S₆] becomes an exceptional material that shows ultrahigh removal, unprecedented selectivity, extremely rapid adsorption kinetics, a wide range of pH stability, and a massive adsorption capacity. The integration of such exceptional features places LDH–[Sn₂S₆] at the top of all adsorbents known to date. Thus, this cost-effective material could be used for wastewater purifications.

Jing Nie

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