The intensification of industrial technology increased heavy metal contamination in aquatic systems. Since inorganic pollutants cannot be degraded, an efficient removal system must be designed in order to detoxify heavy metal-contaminated wastewaters. Metal ion biosorption by microorganisms is an interesting mechanism which can be exploited for this purpose. The purple bacterium Rhodobacter sphaeroides is known for its ability to tolerate under phototrophic conditions high concentrations of several heavy metal ions and to bioaccumulate Ni2+ and Co2+ ions. In this work Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectroscopy and X-Ray Photoelectron Spectroscopy (XPS) have been employed for getting information about Ni2+ binding onto R. sphaeroides cell surface. The ability to bind nickel ions was evaluated both in free cells and in calcium alginate-immobilized biomass. Before Ni2+ exposure the bacterial biomass was washed thoroughly with KCl 0.1 M in order to fully saturate with K+ ions the negatively charged cell envelopes. XPS measurements revealed that treatment with Ni2+ resulted in full displacement of K+ ions from free R. sphaeroides cells, indicating high affinity between nickel ions and surface functional groups. Moreover ATR-FTIR measurements showed that Ni2+-treatment induce the shift of absorption bands arising from symmetric and asymmetric stretching modes of cell surface carboxylate groups, in agreement with their involvement in metal complexation. Calcium alginate beads entrapping bacterial biomass were prepared dropping a cell suspension supplemented with sodium alginate into 2% CaCl . XPS analysis of Ni2+-treated beads revealed that the exposure of cells to Ca2+ strongly inhibited Ni2+ uptake suggesting that displacement of Ca2+ by nickel ions does not occur. These data are of interest in order to identify optimal conditions for the efficient removal of Ni2+ by means of phototrophic bacterial biomass.
Bacterial phototrophic biomass as biosorbent for the removal of Nickel(II) from waste-waters
M Trotta;F Milano;
2015
Abstract
The intensification of industrial technology increased heavy metal contamination in aquatic systems. Since inorganic pollutants cannot be degraded, an efficient removal system must be designed in order to detoxify heavy metal-contaminated wastewaters. Metal ion biosorption by microorganisms is an interesting mechanism which can be exploited for this purpose. The purple bacterium Rhodobacter sphaeroides is known for its ability to tolerate under phototrophic conditions high concentrations of several heavy metal ions and to bioaccumulate Ni2+ and Co2+ ions. In this work Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectroscopy and X-Ray Photoelectron Spectroscopy (XPS) have been employed for getting information about Ni2+ binding onto R. sphaeroides cell surface. The ability to bind nickel ions was evaluated both in free cells and in calcium alginate-immobilized biomass. Before Ni2+ exposure the bacterial biomass was washed thoroughly with KCl 0.1 M in order to fully saturate with K+ ions the negatively charged cell envelopes. XPS measurements revealed that treatment with Ni2+ resulted in full displacement of K+ ions from free R. sphaeroides cells, indicating high affinity between nickel ions and surface functional groups. Moreover ATR-FTIR measurements showed that Ni2+-treatment induce the shift of absorption bands arising from symmetric and asymmetric stretching modes of cell surface carboxylate groups, in agreement with their involvement in metal complexation. Calcium alginate beads entrapping bacterial biomass were prepared dropping a cell suspension supplemented with sodium alginate into 2% CaCl . XPS analysis of Ni2+-treated beads revealed that the exposure of cells to Ca2+ strongly inhibited Ni2+ uptake suggesting that displacement of Ca2+ by nickel ions does not occur. These data are of interest in order to identify optimal conditions for the efficient removal of Ni2+ by means of phototrophic bacterial biomass.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
