Evaluation and Adsorption Modeling of Continuous Adsorption of Malachite Green Pigments Onto Sawdust-Derived Activated Carbon in a Fixed Bed Column

The adsorption of malachite green pigments onto activated carbon was carried out in a continuous fixed-bed column. The aim of this study is to investigate the adsorption of malachite green dye onto activated carbon derived from sawdust in a fixed-bed column, evaluating the process behavior for enhanced pollutant removal. The prepared activated carbon was characterized by Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDS), Fourier Transform Infrared Spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET) surface area analysis. The column performance was evaluated by varying bed heights (1.25, 2.5, and 5.0 cm) while keeping other factors such as influent flow rate (5 mL/min) and concentration (500 mg/L) constant to obtain experimental breakthrough curves. From the breakthrough curves, it was observed that the breakthrough time (tb) increased from 180 min to 270 and 330 min for bed heights of 1.25, 2.5, and 5.0 cm respectively. The exhaustion time (td) for the adsorbent bed increased from 390 min to 420 and 510 min as bed height increased from 1.25 to 2.5 and 5.0 cm respectively. The adsorption capacity (qo) was found to be 221.54, 148.34, and 91.22 mg/g for bed heights of 1.25, 2.5, and 5.0 cm respectively. The removal efficiency of malachite green was 54.53%, 67%, and 68.82% for bed heights of 1.25, 2.5, and 5.0 cm respectively. The performance of the column was analyzed using the Thomas, Adams-Bohart, and Yoon-Nelson models. The rate constant for all three models decreased with increasing bed height, while the time required for 50% adsorbate breakthrough increased with increasing bed height. The Adams-Bohart model, which presented consistently high R² values ranging from 0.8344 to 0.9229, was the most suitable model for describing the experimental data.