The removing some toxic metals from waters by biosorption method

Recently, heavy metal pollution is one of the most important environmental problems and also waters are affectedsignificantly from this pollution. For removing of the toxic metals from aqueous solutions, usually it is used traditional methods such as chemical precipitation, hyperfiltration, ion exchange, evaporation, electrochemical applications. But these methods are not effective enough especially for removing metal ions having low concentration in waters and their high cost of application are economically rather challenging. Nowadays, biosorption method, in which organisms such as bacteria, algae and fungi are used powerful alternative to traditional methods when mentioned problems are considered. Because becoming toxic metals in waters can be removed effectively with low cost and selectively even at ppb levels via using biosorption method. In our study, the removal abilities of Bacillus subtilis ATCC 6051 and two wild type strains of Bacillus licheniformis for Cd(II), Cu(II), Pb(II), Ni(II), Zn(II) ve Fe(II) ions was evaluated in aqueous solutions of these metals with using batch method. In this context, in order to deterrmining optimum conditions, several parameters including initial concentration, temperature, pH, amount of biosorbent and time were investigated . Kinetics studies showed that biosorptions of these metal ions were more compatible with the pseudo-second kinetic model. In addition, activation energy was calculated with using rate constant at different temperatures. Once the adsorption isotherm energy was evaluated in Freundlich and Langmuir isotherm models, it was seen that the adsorption was compatible with Langmuir isotherm and thermodynamic functions such as free energy change (ΔG), enthalpy change (ΔH) and entropy change (ΔS) were calculated by using these data. Once high efficienty of these biosorbents was seen in aqueous solutions, the abilitiy of these biosorbents on removing mentioned metal ions that may present low concentrations in drinking water, riwer water and waste water also was tested with ICP-MS. Finally, while the interactions of biosorbent and metal ions was determined with using FTIR spectroscopy, the usability of biosorbents at high temperatures was tested by using TGA-DTA analyses. In conclusion, biosorbents used in our study could remove efficiently and selectively metal ions: Cd(II), Cu(II), Pb(II), Ni(II), Zn(II) and Fe(II) from their aqueous solutions. Moreover, these biosorbents were also applied to water samples originated from natural systems (drinking water, river water and waste water) and it was seen that these biosorbents removed efficiently mentioned metal ions even at low concentrations Key Words: Biosorption, Heavy metals, Adsorption, Bacillus subtilis, Bacillus licheniformis, Thermodynamic parameters, Isotherms.