Enhanced adsorption performance of oxidised coconut coir for removal of Cd(II) ions by multi-column arrangement in series.

Biosorption potential of oxidised coconut coir (OCC) for removal of Cd(II) was evaluated by multi-column arrangement by connecting three columns in series. Effect of flow rate at 5, 10 and 15 mL/min was studied at 30 mg/L initial Cd(II) concentration. The dynamic capacity of the system was found to be 321, 206 and 83 mg/L for 5, 10 and 15 mL/min flow rates, respectively, by applying the bed depth service time model. Biosorbent usage rates for single-column and multi-column systems were compared. Better utilisation of biosorbent was observed when the columns are connected in series at similar operating parameters. A simple acid-base regeneration procedure was found to be effective in desorbing/regenerating the cadmium bound biosorbent. Adsorption efficiency was found to decrease from 76.3% for the first cycle to 72.2% and 70.6% in the second and third cycles, respectively. Regeneration efficiencies were more than 94% up to 3 cycles. The study highlights the effectiveness of the multi-column system in biosorption against the conventional single-column system.