Removal of heavy metals from aqueous solutions by modified waste silk

In order to reuse the waste fabric and develop a novel textile-based adsorbent for heavy metal removal, the waste silk fabric was modified by tannic acid (TA) and the prepared adsorbents were characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) analysis. The removal of Cd(II), Cu(II), and Ni(II) ions from aqueous solutions was investigated using the modified silk fabric (TA-SF) under various conditions and the adsorption behavior of heavy metal ions was compared with the original silk fabric. The results showed that the maximum metal adsorption amounts reached 100% in 10 min. The adsorption isotherm models were demonstrated using Langmuir, Freundlich, and Temkin isotherm models, and the adsorption of TA-SF to Cd(II), Cu(II), and Ni(II) were well fitted with Langmuir isotherm than Freundlich and Temkin isotherm model. Moreover, the adsorption kinetics was well fitted with to the pseudo-first-order and pseudo-second-order kinetic models, and adsorption kinetics indicated that the former model was better suited than the latter. For 60 mg/L initial concentrations of Cd(II), Cu(II), and Ni(II) at pH 9.0, the adsorbents' maximum adsorption capacity was 8.03 mg g(-1), 7.42 mg g(-1), and 7.47 mg g(-1), respectively. Within 5 min, the absorbed metal ions on TA-SF could mostly be desorbed. Moreover, TA-SF can adsorb heavy metal ions from dyeing aqueous solution, showing its capability of simultaneous removal of heavy metal and waste dyes. The results suggest that the lower-cost TA-SF could be an effective adsorbent for removing heavy metals from industrial wastewater.

Automated summary

In this study, a novel textile-based adsorbent was developed by modifying waste silk fabric with tannic acid. The results showed that the modified fabric exhibited high adsorption capacity and efficiency for the removal of heavy metal ions from aqueous solutions. The adsorption behavior of the adsorbent was well fitted with Langmuir isotherm and pseudo-first-order kinetic model. Moreover, the adsorbent demonstrated the capability of simultaneous removal of heavy metal ions and waste dyes.