A facile method to achieve dopamine polymerization in MOFs pore structure for efficient and selective removal of trace lead (II) ions from drinking water.

Heavy metals are seriously hazardous contaminants and drinking water has been identified as an important route of human exposure to them. Herein, to efficiently and selectively remove trace heavy metal ions, a facile method was reported to achieve the slow polymerization of dopamine in the cages of MIL-100 (Fe) via ultrasonic treatment followed by the hydrolysis of the urea. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), Brunner-Emmet-Teller (BET) and pore size distribution determination confirmed the formation of the polydopamine (PDA) and binding with the unsaturated Fe site in MIL-100 (Fe) pores. The composite not only retained pore structure of MOFs but also contained abundant reactive functional groups. When initial lead concentration was 150 ppb and 20 ppm calcium coexisted at pH of 6.5 ± 0.25, the effluent lead concentration met the safe drinking water standard in several tens of seconds, and decreased to 1.13 ppb in 10 min. The adsorption rate reached 99.35%. The synthetic strategy effectively overcomes mass transfer resistance of trace heavy metal ions and provides a facile approach to prepare adsorption materials for efficient and selective removal of trace heavy metal ions from drinking water.