Fixed-bed Biosorption Research Articles

Biosorption Processes for Natural and Waste Water Treatment – Part II: Experimental Studies and Theoretical Model of a Biosorption Fixed Bed

AbstractA model has been developed for fixed‐bed biosorption performance, i.e. combined action of adsorption of organic water contaminants and their biological destruction in a column. The model contains an adsorption isotherm of the Freundlich type, adsorption kinetics by an overall film mass transfer (Glueckauf equation), maximum bacterial growth,and biological aerobic destruction (Monod model) of the organics by exoenzymes. Bacteria can not penetrate into the pores of the adsorbent. The model was tested using the system aqueous solution of aniline/Pseudomonas putida/Polysorb 40/100. Breakthrough curves in shorter columns have been measured and a velocity‐dependent steady‐state exit concentration was achieved. These curves could be simulated with sufficient accuracy on the basis of isotherm data, mass transfer coefficients and values of biological growth and destruction activity estimated from independent measurements.

Application of simplified rapid equilibrium models in simulating experimental breakthrough curves from fixed bed biosorption reactors

A modelling approach for a fixed bed biosorption column is presented. The Advection–Dispersion–Reaction (ADR) equation has been applied as the basic modelling equation for the special case of Local Equilibrium (LE). The model implements the minimum parameters for describing a fixed bed biosorption column, employing the geometrical dimensions of the bed, the packing arrangement, the operating conditions of the system, and the sorptive characteristics of the biosorbent material. An apparent axial dispersion coefficient has been used as a key parameter of the model. The authors compare model predictions to selected examples of experimental biosorption breakthrough curves reported from pilot scale work. Although the main assumption of the model is that biosorption equilibrium is rapid, the use of an apparent overall dispersion coefficient makes the model applicable for the cases where mass transfer resistances are present in the liquid and solid phases.

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 (tb) 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.

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 (tb) 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/O cycles.

Biosorption of Metal Ions from Aqueous Solutions

Copper biosorption from aqueous solutions by calcium alginate is reported in this paper. The experimental section includes potentiometric titrations of biosorbents, batch equilibrium and kinetic studies of copper biosorption, as well as fixed-bed biosorption experiments. The potentiometric titration results show that the surface charge increases with decreasing pH. The biosorption of copper strongly depends on solution pH; the metal ion binding increases from 0 to 90 percent in pH ranging from 1.5 to 5.0. In addition, a decrease in ionic strength results in an increase of copper ion removal. Kinetic studies indicate that mass transfer plays an important role in the biosorption rate. Furthermore, a fixed-bed biosorption experiment shows that calcium alginate has a significant capacity for copper ion removal. The two-pK Basic Stern model successfully represents the surface charge and equilibrium biosorption experimental data. The calculation results demonstrate that the copper removal may result from the binding of free copper and its hydroxide with surface functional groups of the biosorbents.