[Characteristic and ion exchanges during Cu2+ and Cd2+ biosorption by Stenotrophomonas maltophilia]

The characteristics of Cu2+ and Cd2+ biosorption by Stenotrophomonas maltophilia (S. maltophilia) under different biomass, metal concentration and glutaraldehyde content were studied and the correlations among metal biosorption, NO3- removal and ion release were analyzed. The mechanism was explored through ion biosorption, exchange, conversion and release. The experimental results demonstrated that S. maltophilia was an efficient strain to remove Cu2+ and Cd2+. The biosorption efficiencies of Cu2+ and Cd2+ achieved 96.3% and 83.9%, respectively after dealing with 0.05 mmol x L(-1) aqueous solutions for 120 min with dry biosorbent dosage of 0.2 g x L(-1). Cu2+ and Cd2+ biosorption by S. maltophilia included surface adsorption, transmembrane active transportation, bioaccumulation of NO3- and reduction of NO3- to NO2-. The intracellular transfer and reduction of NO3- to NO2- during biosorption by S. maltophilia were energy-consuming biological processes. It could also promote the release of Cl-, PO4(3-), SO-4(2-), Na+, NH4+, K+ and Ca2+. From FTIR investigation, involvement of various functional groups like acetylamino, hydroxyl and carboxyl in the binding of Cu2+ and Cd2+ was evident. Moreover, XPS results proved that the valence state of Cu2+ and Cd2+ did not changed by biosorption.