Fixed-bed column dynamics of tetracycline hydrochloride using commercial grade activated carbon: comparison of linear and nonlinear mathematical modeling studies

Abstract

Continuous column dynamic studies were carried out for the removal of tetracycline hydrochloride (TC-HCl) using commercial grade activated carbon. Experimental investigations were carried out for various factors such as flow rates (1.5, 3, and 5 mL min⁻¹), initial concentrations (200, 400, and 600 μg L⁻¹), and bed height (4.5, 10 cm). Experimental breakthrough curves were generated using concentration–time profile with the empirical data. The total adsorbed quantities and equilibrium uptake rates were determined by evaluating the breakthrough curves obtained at different flow rates, different initial concentrations, and different bed heights. The exhaustion time and bed capacity increased with bed height and initial concentrations and found to increase with the decrease in flow rates. The theoretical breakthrough curves were predicted using Adam–Bohart, Wolborska, Thomas, Yoon–Nelson, and Wang’s model. A comparative analysis of linear and nonlinear least square methods was employed for estimating the kinetic parameters using experimental data. Error analysis was carried out for best fitting models. The results from dynamic studies showed that a maximum adsorption capacity was achieved for an initial concentration of 600 μg L⁻¹ bed height of 10 cm and flow rate of 1.5 mL min⁻¹. From the kinetic models, Thomas and Yoon–Nelson model gave a better fit with linear and nonlinear regression analysis. The same was proved statistically. The nonlinear regression analysis was comparatively much better than that of linear regression analysis as observed.

Keywords:

• Tetracycline hydrochloride (TC-HCl)
• Fixed-bed reactor
• Activated carbon
• Mathematical modeling
• Error analysis
• Thomas model
• Yoon–Nelson
• Adam–Bohart
• Wang
• Wolborska