Cu(II) removal from water by trimercapto-s-triazine trisodium salt modified alkaline lignin

To overcome the poor removal ability of alkaline lignin (AL) toward heavy metals, trimercapto-s-triazine trisodium salt (TMT) was selected as the modifying agent to introduce reaction groups. The Fourier transform infrared (FT-IR) spectra and the scanning electron microscopy (SEM) suggested that -SNa, C-N, and C = N groups were successfully introduced. Copper (II) was applied to evaluate the uptake performance of the adsorbent (AL-TMT). Adsorbent dosage and solution pH were taken into account to study their effects in the batch experiments. The pseudo-second-order dynamics and Langmuir models better described the experimental data. Nitrogen (N) and carbon (C) functional groups in thiotriazinone carried by AL-TMT were determined to be the primary uptake sites through X-ray photoelectron spectroscopy (XPS), FT-IR, and electrostatic potential (ESP). The selective experiments of AL-TMT toward Cd(II), Cu(II), Pb(II), Zn(II), Co(II), and Mg(II) were performed. It showed that AL-TMT possessed better adsorption selectivity toward Cu(II) than others. Furthermore, the density functional theory (DFT) calculations of thiotriazinone in AL-TMT also exhibited the lowest binding energy toward Cu than toward others. This work may provide a theoretical basis to facilitate the extraction of specific heavy metals from water or wastewater by using such modified alkaline lignin.

Automated summary

To improve the removal ability of alkaline lignin (AL) towards heavy metals, trimercapto-s-triazine trisodium salt (TMT) was used as a modifying agent to introduce reaction groups. The successful introduction of -SNa, C-N, and C = N groups was confirmed by FT-IR spectra and SEM. The adsorption performance of the modified AL-TMT towards copper (II) was evaluated, and the results showed better adsorption selectivity towards Cu(II) than other heavy metals. This research provides a theoretical basis for the extraction of specific heavy metals from water or wastewater using modified alkaline lignin.