Hierarchical sand-modified KCC-1 composite as a robust adsorbent in a continuous flow fixed-bed reactor for water purification

Lead (Pb) is one of the most hazardous heavy metals found in wastewater. Adsorption in a continuous fixed-bed column is used for treating large volumes of wastewater, and the efficiency of this process can be monitored using the breakthrough curve. In this study, fibrous nanosilica (KCC-1) from rice husk ash was employed as an adsorbent and modified using granular sand to prevent it from being difficult to separate from the Pb. The study fabricates a continuous fixed-bed adsorption column loaded with modified-sand KCC-1 to examine the impact of flow rate (10–40 mL min−1), bed height (3–12 cm), and concentrations (50–200 mg L−1) on Pb2+ adsorption. The experiment operated for 5 h, with samples taken every 30 min and analyzed using a UV-Vis spectrophotometer. The results showed that the highest percentage of Pb2+ removal arose at a flow rate of 10 mL min−1, with an adsorption capacity, q, of 29.49 mg g−1, a residence time of 5.0 min, and a removal efficiency of 94.50%. In addition, the adsorption breakthrough was obtained by the Thomas, Adam-Bohart, and Yoon-Nelson models. Based on the adsorption efficiency findings using sand-modified KCC-1, all three models are suitable for describing the adsorption process.