Removal and recovery of lead fixed-bed biosorption with immobilized bacterial biomass

Fixed-bed columns packed with immobilized biomass of Pseudomonas aeruginosa PU21 were utilized to remove lead (Pb) from the contaminated water. Effects of the immobilization method, bed length, flow rate, and the particle size on the performance of Pb removal by the biosorption columns were systematically investigated. Calcium alginate-immobilized cells were found to hold better Pb capacity than polyacrylamide (PAA)-entrapped cells. Typical saturation capacity of calcium alginate (CA)-immobilized cells was 280 mg Pb/g, and 31 mg Pb/g for PAA-immobilized cells. Results of fixed-bed biosorption showed that the breakthrough time (t(b)) appeared to increase with the bed length, but decreased with the flow rate. The typical overall adsorption efficiency (Q) was within 50-60%, and did not appreciably fluctuate with changes in the operation conditions or the particle size. The initial rate of adsorption was facilitated nearly 40% as the size of immobilized cells was reduced from 3.5 mm to 2 mm, whereas the particle size did not affect the equilibrium adsorption of the immobilized biomass. The length of unused bed (LUB) remained constant with different bed length, while it slightly increased with the raising of the Pb loading rate. The metal-laden column was regenerated by elution of HCl solution (pH 2.0). For up to four adsorption/desorption (A/D) cycles, the metal recovery efficiency of each cycle was over 98%, and the recovery ratio was 8:1 and 27:1 for PAA and CA-immobilized cells, respectively. The regenerated beds were able to restore over 66% of their original adsorption capacity after four successive A/D cycles.