Biogenic Mn oxides are expected to have great potential in the control of water pollution due to their high catalytic activity, although information on biological Mn oxidation is not currently sufficient. In this study, the growth of a Mn oxidizing microorganism, Pseudomonas putida MnB1, was examined, with the Mn oxides formed by this strain characterized. The growth of P. putida MnB1 was not significantly influenced by Mn(II), but showed a slightly decreased growth rate in the presence of Pb(II) and EE2, indicating their insignificant adsorption onto the cell surface. Mn oxides were formed by P. putida MnB1, but the liquid growth medium and resulting biogenic solids were poorly crystalline, nano-sized particles. Biogenic Mn oxidation by P. putida MnB1 followed Michaelis-Menten kinetics, with stoichiometric amounts of Mn oxides formed, which corresponded with the initial Mn(II) concentration. However, the formation of Mn oxides was inhibited at high initial Mn(II) concentration, suggesting mass transfer obstruction of Mn(II) due to the accumulation of Mn oxides on the extracellular layer. Mn oxidation by P. putida MnB1 was very sensitive to pH and temperature, showing sharp decreases in the Mn oxidation rates outside of the optimum ranges, i.e. pH 7.43-8.22 and around 20-26 o C.

Adsorption of heavy metals by sawdust was investigated to evaluate the effectiveness of using sawdust to remove heavy metals from aqueous solutions. Kinetic and isotherm studies were carried out by considering the effects of initial concentration and pH. The adsorption isotherms of heavy metals fitted the Langmuir or Freundlich model reasonably well. The adsorption capacity of metal was in the order Pb 2+ > Cu 2+ > Zn 2+. A high concentration of co-existing ions such as Ca 2+ and Mg 2+ depressed the adsorption of heavy metal. Adsorption data showed that metal adsorption on sawdust follows a pseudo-second-order reaction. Kinetic studies also indicated that both surface adsorption and intraparticle diffusion were involved in metal adsorption on sawdust. Column studies prove that sawdust could be effective biosorbent for the removal of heavy metals from aqueous phase.

Peroxyoxalate chemiluminescence (PO-CL) spectra obtained simultaneously and continuously using a CCD spectrometer provide evidence of the complexity of PO-CL reactions.

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