Adsorption of methylene blue by an antibacterial bio-sorbents from ligninsulfonate and tannin

A highly effective ligninsulfonate-tannin adsorbent (LTA) with natural antibacterial activity was developed for the removal of methylene blue (MB) from wastewater. The results of Fourier transform infrared spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS) showed the cross-linking reaction between CL and BWT, the results of scanning electron microscope (SEM) showed a granular structure of LTA with a rough surface. The saturation adsorption capacity of LTA for MB is 629.5 mg∙g-1, and the adsorption process is a heat-absorbing, spontaneous process corresponding to the Langmuir isothermal and the pseudo-second-order kinetic adsorption model. Density functional theory (DFT) calculations were used to further elucidate the adsorption mechanism, which was the synergistic effect of amino groups in methylene blue with phenolic hydroxyl group and sulfonic acid group in LTA. It is unexpected to find that LTA retained the natural antibacterial activity of tannins, and inhibition of E. coli and S. aureus with 80.0% and 82.0%.Thus, LTA has a high value in the removal of dyes and biological contamination from wastewater due to its excellent adsorption capacity, and natural antibacterial properties.