The objective of the present work was to evaluate the performance of two-stage adsorber of activated carbon from oil palm empty fruit bunch for methylene blue removal. The model was developed to predict optimum adsorbent mass and time at a specified volumes and concentrations of dye solution. Results show that the adsorbent mass can be reduced by 6.67%. Operating time taken to attain the equilibrium in a two-stage adsorber has dramatically decreased from 22 h to 0.52 h. In the performance evaluation, the adsorbent mass in stage-1 is higher than in stage-2, which lessen the workload to achieve equilibrium. A two-stage adsorber aids to optimize the mass and contact time for different percentage of dye removal that economically feasible for industrial applications.

The present work was aimed to evaluate the optimum mass of crab shell biochar and adsorption contact time in a two-stage adsorber design for malachite green. The model was developed to predict optimum adsorbent mass and adsorption profiles at specified volumes and concentrations of dye effluent. Results show that the adsorbent mass can only be reduced by 1.91 % because of the adsorbent’s strong affinity towards malachite green. Accordingly, the adsorption contact time to achieve equilibrium has dramatically reduced from 150 min to 31 min. In the performance evaluation, the adsorbent mass in stage-1 is always higher than that in stage-2 to subside the adsorbent load in achieving the target removal at optimum dosage. From the response surface methodology, the most significant parameters in two-stage adsorber design are adsorption time at stage-2 and malachite green concentration. The predicted values of adsorbent mass and time are essential in designing the cost-competitive two-stage adsorption process for industrial wastewater treatment.