A novel magnetite-immobilized cell process for heavy metal removal from industrial effluent

The sorption and desorption of copper (II) (Cu[II]) ions from the wastewater by magnetite-immobilized cells of Pseudomonas putida 5-x with acidic pretreatment were studied. Pretreating cells with 0.6 N HCl was found to enhance greatly the adsorption capacity of biomass up to 85.6 mg/g and had no significant effect on the loss of P. putida 5-x cells during biosorbent pretreatment. The biosorption capacity to Cu2+ of magnetite-immobilized cells of P. putida 5-x harvested during various growth phases was also investigated. The experimental results illustrated that the adsorption capacity to Cu2+ of P. putida 5-x cultured in sulfate-limiting medium reached maximum during the late stationary growth phase or early death phase, and reached minimum during the log growth phase. The mechanism of copper sequestering by this type of biomass was studied via transmission electron microscopy. A degradation of the peptidoglycan layer of the cell wall was observed in the acidic pretreatment, but no further degradation appeared after the adsorption-desorption cycle. Cu(II) accumulated mostly on the surface of the cell walls and was effectively desorbed by the acidic treatment during the desorption process.