Evaluation of epigallocatechin gallate (EGCG) to remove Pb(II) using spectroscopic and quantum chemical calculation method

Recently, (−)-epigallocatechin-3-gallate (EGCG) has been highly reviewed for its beneficial chemical properties. In this study, the formation mechanism of the complexes obtained by EGCG and Pb(II) was investigated in an aqueous solution, using a molar ratio method with the verification of UV–Vis spectrometry, scanning electron microscope (SEM), quantum calculation, and Fourier transform infrared spectrometry (FTIR). The SEM results showed that the morphology of EGCG changed from spherical or approximately spherical shapes to massive structures. The molar ratio method and the UV–Vis absorption spectroscopy were effective in determining the complex composition, and the resulting data indicated that the EGCG–Pb(II) complex was formed with an optimum EGCG:Pb molar ratio of 1:2 at pH 5.0. A quantum computation with Parametric Method 7 (PM7) and FTIR spectra were useful to identify the molecular structure of the complex. The results evidently exhibited the changes of molecular structure of EGCG before versus after the complexation reaction, and a complex formation was observed. In general, this work would be favorable to the further research on complexation of EGCG with other metal ions. Such complexes will make a reference for treating wastewater streams polluted by toxic metals.