Performance and dynamic modelling of biochar and kaolin packed bed adsorption column for aqueous phase methylene blue (MB) dye removal

A practical continuous adsorption study in a packed-bed column was conducted by using two separate layers of kaolin and pine cone based biochar packed bed adsorbents for the removal of methylene blue (MB) dye from its aqueous solution. A series of column experiments were performed to determine the breakthrough curves (BTCs) by varying bed height (3-7 cm), inlet flow rate (13-17 ml/min) and initial dye concentration (50-150 mg/L). The Thomas, Yoon-Nelson, Bed Depth Service Time (BDST) and Dose response (DR) dynamic models were applied to column experimental data under various operational conditions to predict the column breakthrough curves (BTC) using both nonlinear regression and linear regression and to determine various characteristic parameters such as percentage removal of dye, breakthrough time, used bed length, mass transfer zone (MTZ) and dye adsorption density q(total) that are useful for process design. The MB dye adsorption was found to be most favourable under low flow rate, high adsorbent bed height and high initial dye concentrations. The experimental column breakthrough data were in good agreement with the various dynamic models and the results of various model characteristic parameters could be used to scale up the process to an actual industrial column operation. Also, this column study revealed the feasibility of pine cone biochar and kaolin adsorbents as alternative sustainable adsorbents for dye-bearing wastewater treatment.