Cellulose-based adsorbents loaded with zero-valent iron for removal of metal ions from contaminated water

Sawdust loaded with zero-valent iron (S-ZVI) was prepared using a liquid phase reduction method for removing heavy metal ions from contaminated water. Surface chemistry and morphology of adsorbents were characterized with Fourier transform infrared (FT-IR) spectrometry, X-ray diffraction (XRD), scanning electron microscopy (SEM), SEM-mapping, EDX, and X-ray photoelectron spectrum (XPS). The results demonstrated that the zero-valent iron was successfully loaded onto the sawdust. The impact of various factors such as pH, initial metal ion concentration, temperature, and contact time on the removal capability of the adsorbents was systematically investigated. The equilibrium adsorption data showed that the adsorption of arsenic ions and Cr(III) followed the Langmuir model well, and the maximum adsorption reached 111.37 and 268.7 mg/g in an aqueous solution system. In addition, the adsorption kinetics was more accurately described by the pseudo-second-order model, suggesting the domination of chemical adsorption. Meanwhile, the results on recyclability indicated that the high performance of S-ZVI on the removal of arsenic ions was well maintained after three regeneration cycles. The adsorption mechanism revealed in this work suggested that S-ZVI improved the dispersion of ZVI by minimizing the agglomeration, thus leading to highly effective adsorption via chelation, electrostatic interaction, and redox reaction.