Green composite tea waste and activated carbon from bamboo fiber: structural and optical properties, chemical bonding, and adsorption of lead pb(ii) performance

Developing efficient and effective adsorbents for lead (Pb(II)) ions is essential for promoting a sustainable, green environment and clean water. This study investigated a green composite material from tea waste and activated carbon (TW/AC) for Pb(II) ion adsorption. Structural properties, including crystal and amorphous phases, were analyzed using X-ray diffraction (XRD). The chemical bonding of the composite was identified from Fourier-transform infrared (FTIR) spectroscopy spectra, while the adsorption performance for Pb(II) ions was evaluated using atomic absorption spectroscopy (AAS). Optical properties, dielectric function, and phonon vibration before and after the adsorption process were quantitatively assessed from FTIR spectra. The highest adsorption capacity for Pb(II) ions was 167.7 mg/g at pH 7, achieved within 60 min using 80% TW. The adsorption process, supported by the amorphous structure, showed minimal changes in crystallinity, from 89.06 to 86.56%, with slight adjustments in chemical bonding and the distance between two optical phonon modes, Δ(LO-TO), reducing from 89 to 76. These findings suggest that Pb(II) ions are well-integrated into the dangling bonds of the amorphous structure, with pores acting as ion traps. The surface states identified in the TW/AC composite from FTIR spectra—such as -OH, -C = C, C = O, and -CH groups can form covalent bonds with Pb(II) ions, thereby enhancing the adsorption capacity.