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

A novel multi-functional and environmental friendly tannic acid polymer (Fe-TA-HCHO) with Fe 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-TA-HCHO possessed uniform structure and particle size as well as plentiful functional groups. The resulted Fe-TA-HCHO material as a adsorbent to remove methylene blue, sunset yellow, Pb, Hg, and AsO from water. The results suggested that Fe-TA-HCHO polymer (pHpzc is 2.33) showed different adsorption properties for anionic pollutants (sunset yellow and AsO) and cationic pollutants (methylene blue, Pb, and Hg). The material exhibited remarkable selectivity for adsorption and separation of pollutants. The maximum adsorption capacities calculated from Langmuir model for methylene blue, Pb, and Hg were 154.32, 819.67, and 699.30 mg g, 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.