EVALUATION AND ADSORPTION MODELING OF CONTINUOUS ADSORPTION OF MALACHITE GREEN PIGMENTS ONTO SAWDUST-DERIVED ACTIVATED CARBON IN A FIXED BED COLUMN

The study was conducted to investigate the adsorption of malachite green dye onto activated carbon prepared from sawdust in a fixed-bed column, with the aim of understanding the process dynamics and improving pollutant removal efficiency. 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 performances were 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 mins to 270 and 330 mins for bed heights of 1.25, 2.5, and 5 cm, respectively. The exhaustion time (td) for the adsorbent bed was found to increase from 390 mins to 420 mins and 510 mins as bed height increased from 1.25 to 2.5 and 5 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 cm, respectively. The removal efficiency of malachite green was found to be 54.53%, 67%, and 68.82% for bed heights of 1.25, 2.5, and 5 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 heights, while the time required for 50% adsorbate breakthrough increased with increasing bed height. The Adams-Bohart model, which presented consistently high R² values within the range of 0.8344 to 0.9229, is the most suitable model for describing the experimental data.