Adsorption of cesium from aqueous solution by raw and concentrated nitric acid-modified bamboo charcoal

The study is conducted to explore the potential of bamboo charcoal (BC) as an adsorbent to remove cesium from aqueous solution. Low temperature carbonized BC (500 °C) is prepared and the surface of the BC is modified with 70% concentrated boiling nitric acid (BC-AC). Specific surface area, field emission scanning electron microscope (FESEM), fourier transform infra-red (FTIR) spectroscopy, and point of zero charge (pH_pzc) of BC and BC-AC have been investigated in this study. The results demonstrate that BC-AC is enriched with oxygen-containing functional groups but its porous structure and surface area are decreased when compared with the raw BC. Optimum cesium adsorption conditions onto BC and BC-AC have been determined by investigating the contact time, pH of solution, adsorbent dosage and initial solution concentration in batch adsorption process. It has been observed that maximum cesium adsorption capacity is 0.17 and 45.87 mg/g for BC and BC-AC, respectively. It has also been observed that almost 100% cesium could be removed from water at up to 400 mg/L concentrated cesium solution by BC-AC whereas the removal capacity of cesium by BC is very poor. The experimental adsorption data of both BC and BC-AC follows the pseudo-second-order kinetic. The Freundlich adsorption equilibrium isotherm data is more appropriate than the Langmuir isotherm for adsorption of cesium by BC. However, adsorption isotherm data for BC-AC is a better fit with Langmuir isotherm than the Freundlich isotherm model. Furthermore, the separations factor (R_L) and the surface coverage (θ) for Langmuir isotherm confirms that the proposed adsorption process is the most suitable for BC-AC. This study suggests that BC-AC could be effectively used for the removal of cesium from environmental water.