The effect and spectral response mechanism of dissolved organic matter (DOM) in Pb(II) adsorption onto biochar

This study investigated the interaction of biochar-derived dissolved organic matter (DOM) and metal pollutant Pb(II) during adsorption. Research data showed that the adsorption capacity of biochar and residual biochar (after removal of DOM) was 277.62 and 204.47 mg g−1, respectively, indicating that DOM played a significant role in enhancing the adsorption efficiency of Pb(II). The results indicated that the adsorption process of Pb(II) on biochar and residual biochar followed the pseudo-second-order kinetic equation (R2 > 0.99), and the adsorption isotherm was much closer Freundlich model. A combination of three-dimensional excitation-emission matrix (3D-EEM), synchronous fluorescence, Fourier transform infrared spectroscopy (FT-IR), and two-dimensional correlation spectroscopy (2D-COS) was employed to investigate the interaction between DOM and Pb(II). 3D-EEM indicated the presence of four major components of DOM, namely two protein-like substances, one humic acid-like substance, and one fulvic acid-like substance. The synchronous fluorescence revealed a gradual quenching of the fluorescence of the DOM sample with an increase in Pb(II) concentration, indicating a static quenching mechanism between DOM and Pb(II). FTIR-2D-COS analysis showed a specific sequence of DOM binding with Pb(II) is as follows: 1500 > 1010 > 880 > 1390 > 1260 cm−1. This findings have significant implications for the role of DOM in environmental science and have potential applications in various fields. [Display omitted] •DOM plays a significant role in the removal of Pb(II) pollution by biochar.•Humic acid-like and fulvic acid-like substances dominate the binding process between DOM and Pb(II).•The quenching mechanism between DOM and Pb(II) is static quenching.•The amide N-H and C-N groups in DOM exhibit a preferential binding affinity for Pb(II).