CADMIUM REMOVAL IN A BIOSORPTION COLUMN

New biosorbent material derived from a ubiquitous brown marine alga Ascophyllum nodosum has been examined in packed-bed flow-through sorption columns. It effectively removed 10 mg/L of cadmium down to 1.5 ppb levels in the effluent representing 99.985% removal. The experimental methodology used was based on the early Bohart and Adams sorption model, resulting in quantitative determination of the characteristic process parameters which can be used for performance comparison and process design. An average metal loading of the biosorbent (N-0) determined was 30 mg Cd/g, corresponding closely to that observed for the batch equilibrium metal concentration of 10 mg Cd/L. The critical bed depth (D-min) for the potable water effluent quality standard (0.005 mg Cd/L) varied with the column feed flow rate (2.4 to 9.6 L/h.cm(2)) from 20 to 50 cm. The sorption column mass transfer and dispersion coefficients were determined, which are also required for solving the sorption model equations. (C) 1994 John Wiley & Sons, Inc.