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

Abstract

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-, CO32–, NO3–,and SO42-, 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.