Estimation of packed-bed parameters and prediction of breakthrough curves for adsorptive removal of 2,4-dichlorophenoxyacetic acid using rice husk ash

Abstract

In this paper, we studied the physicochemical characteristics of rice husk ash (RHA). Our results show higher surface area, smaller silica-to-carbon ratio, and consequently higher batch adsorption capacity for bigger RHA particles. Packed-bed performance of bigger particles (0.500–0.354mm) was investigated for influent concentration (50–400mg/L), flow rate (1–10 mL/min), and bed height (7–13cm). The maximal removal (53.86%) was achieved for an influent concentration of 50mg/L, flow rate of 7mL/min, and bed height of 9cm. For minimal removal (34.60%), the corresponding parameters were 100mg/L, 7mL/min, and 7cm. Various mathematical models, including bed depth service time, Bohart–Adams, Wolborska, Thomas, Clark, Yoon–Nelson, and deactivation kinetic, are applied to experimental data for breakthrough curve prediction and to determine the optimal bed parameters. According to the bed depth service time model, 10% and 90% breakthrough capacities were determined to be 2628.10 and 7400.03mg/L, respectively. The deactivation kinetic model for the solid–liquid adsorption system is found to best elucidate the packed-bed data. Packed-bed adsorption capacity (mg/m2) for RHA is 2.7 times higher than synthetic activated carbon.