Rapid, Selective Heavy Metal Removal from Water by a Metal-Organic Framework/Polydopamine Composite.

Daniel T Sun,Davide Tiana,Seyed Mohamad Moosavi,Wendy L Queen,Emad Oveisi,David K Britt,Li Peng,Washington S Reeder

doi:10.1021/acscentsci.7b00605

Abstract

Drinking water contamination with heavy metals, particularly lead, is a persistent problem worldwide with grave public health consequences. Existing purification methods often cannot address this problem quickly and economically. Here we report a cheap, water stable metal–organic framework/polymer composite, Fe-BTC/PDA, that exhibits rapid, selective removal of large quantities of heavy metals, such as Pb2+ and Hg2+, from real world water samples. In this work, Fe-BTC is treated with dopamine, which undergoes a spontaneous polymerization to polydopamine (PDA) within its pores via the Fe3+ open metal sites. The PDA, pinned on the internal MOF surface, gains extrinsic porosity, resulting in a composite that binds up to 1634 mg of Hg2+ and 394 mg of Pb2+ per gram of composite and removes more than 99.8% of these ions from a 1 ppm solution, yielding drinkable levels in seconds. Further, the composite properties are well-maintained in river and seawater samples spiked with only trace amounts of lead, illustrating unprecedented selectivity. Remarkably, no significant uptake of competing metal ions is observed even when interferents, such as Na+, are present at concentrations up to 14 000 times that of Pb2+. The material is further shown to be resistant to fouling when tested in high concentrations of common organic interferents, like humic acid, and is fully regenerable over many cycles.

Highlights

With an estimated 1 billion people without access to clean drinking water and 2 million casualties per year, water contamination is currently one of the world’s leading causes of death.[1]
Fe-BTC, synthesized using known procedures,[25] possesses empty mesoporous cages of 25 and 29 Å diameter that can be accessed via microporous windows of about 5.5 and 8.6 Å
Density functional theory (DFT) calculations were utilized to assess the feasibility of PDA binding to Fe3+ sites (Figure S10 and Table S2)

Summary

■ INTRODUCTION

With an estimated 1 billion people without access to clean drinking water and 2 million casualties per year, water contamination is currently one of the world’s leading causes of death.[1] This problem is only expected to worsen as the World Health Organization (WHO) estimates that climate change will limit access to clean water for as much as half of the world’s population,[2] and a recent United Nations report projects that the world could face a 40% water shortage in as few as 15 years.[3] A surge in energy production and an exponential increase in heavy metal use in industrial processes have caused a rise in human exposure to toxic heavy metals in recent decades.[4] The high toxicity and prevalence of cadmium, chromium, lead, arsenic, and mercury put them among the greatest concern. ACS Central Science the production of large quantities of chemical sludge.[5] As a result, even well documented cases of contamination in developed countries are left without remediation These inadequacies have sparked our interest in the exploration of inexpensive metal−organic frameworks (MOFs) for water purification. The resulting composite combines high capacity, selectivity, and a record-breaking removal rate of Pb2+ and Hg2+ ions, making it a highly promising material for decontamination of drinking water

■ RESULTS AND DISCUSSION

■ CONCLUDING REMARKS

■ ACKNOWLEDGMENTS

■ REFERENCES