Preparation and application of silver oxide/sawdust nanocomposite for Chromium(VI) ion removal from aqueous solutions using column system

This study describes the removal of Cr (VI) ions from aqueous solutions using silver oxide/sawdust nanocomposite (Ag2O/SD NC) that was prepared using the chemical precipitation method. Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR) techniques were used for characterization of Ag2O/SD NC. The effect of various parameters such as feed solution pH (2, 6, and 10), influent concentration of Chromium (VI) (25-100 mg/L), flow rate (1-5 mL/min) and bed depth (4-12 cm) on breakthrough curves (BTC) were investigated. Three well-known column adsorption kinetics models including Thomas, Adams-Bohart and Bed Depth Service Time (BDST) models were applied to fitting the column experimental data. Based on Thomas model, the equilibrium adsorption reached 13.41 mg/g when a Cr (VI) polluted solution with influent concentration of 25 mg/L Cr (VI) passed through the column with a flow rate of 2 mL/min. Desorption studies reveal that recovery of uploaded Cr (VI) from the Ag2O/SD NC adsorbent or exhausted column regeneration can readily be achieved using a dilute solution of NaOH (0.01 M) as eluent. This study indicated that the Ag2O/SD NC can be used as an effective, efficient and environmentally friendly adsorbent for the removal of Cr (VI) ions from water resources.