One-pot synthesis of multi-functional and environmental friendly tannic acid polymer with Fe3+ and formaldehyde as double crosslinking agents for selective removal of cation pollutants

A novel multi-functional and environmental friendly tannic acid polymer (Fe 3+ -TA-HCHO) with Fe 3+ and formaldehyde as double crosslinking agents together with cysteine as heteroatom source was prepared by a one-pot hydrothermal method. Characterization with transmission electron microscope (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectrometer (FT-IR), and elemental analysis demonstrated that the Fe 3+ -TA-HCHO possessed uniform structure and particle size as well as plentiful functional groups. The resulted Fe 3+ -TA-HCHO material as a adsorbent to remove methylene blue, sunset yellow, Pb 2+ , Hg 2+ , and AsO 3 3− from water. The results suggested that Fe 3+ -TA-HCHO polymer (pHpzc is 2.33) showed different adsorption properties for anionic pollutants (sunset yellow and AsO 3 3− ) and cationic pollutants (methylene blue, Pb 2+ , and Hg 2+ ). The material exhibited remarkable selectivity for adsorption and separation of pollutants. The maximum adsorption capacities calculated from Langmuir model for methylene blue, Pb 2+ , and Hg 2+ were 154.32, 819.67, and 699.30 mg g −1 , respectively. This is the first time that tannic acid polymer is synthesized by double crosslinking method, which not only developed a promising adsorbent for selective removal of cation pollutants, but also opened up a new avenue for synthesis and application of tannic acid polymer.