Highly efficient, rapid, and concurrent removal of toxic heavy metals by the novel 2D hybrid LDH–[Sn2S6]

According to a United Nations report, by 2050 nearly six billion people worldwide will suffer from clean water scarcity. This is mostly because of the exponential proliferation of world population, urbanization, industrialization, and water pollution. Heavy metals are common water pollutants that can pose grave public health consequences. Existing water purification systems are lack of materials that have the potential for quick, simultaneous, efficient, and cost-efficient removal of numerous toxic metals from wastewater. Here, we report the design and synthesis of an economically viable Layered Double Hydroxides - Stannic Sulfide, LDH–[Sn₂S₆] that exhibits a rapid, efficient, selective, and concurrent removal of Cu²⁺, Ag⁺, Cd²⁺, Pb²⁺, and Hg²⁺ from parts per million (ppm) level to below 5 parts per billion (ppb) satisfying World Health Organization’s (WHO) safe drinking water limit. Moreover, LDH–[Sn₂S₆] shows exceptionally high removal efficiencies of the above metals in acidic, neutral, and basic conditions. LDH–[Sn₂S₆] also demonstrates enormous sorption capacities of 378, 978, 332, 579, and 666 mg/g for Cu²⁺, Ag⁺, Cd²⁺, Pb²⁺, and Hg²⁺, respectively. Remarkably, LDH–[Sn₂S₆] displays extraordinary tolerance to the concentrations of Na⁺, Ca²⁺, Mg²⁺, Cl^-, CO₃^2–, NO₃^–,and SO₄^2-, and other constituents in tap and river water, it efficiently sequestrates Cu²⁺, Ag⁺, Cd²⁺, Pb²⁺, and Hg²⁺ from ppm to safe drinking water levels in minutes. LDH–[Sn₂S₆] shows pseudo-second-order sorption kinetics suggesting chemisorption adsorption mechanism involving M−S bonding. Altogether, the regeneratable LDH–[Sn₂S₆] becomes an exceptional material that shows ultrahigh removal, unprecedented selectivity, rapid adsorption kinetics, wide pH stability, and a massive adsorption capacity. The integration of these features places LDH–[Sn₂S₆] at the top of all adsorbents known to date and thus could be used for wastewater purifications.