Journal of Environmental Sciences 19(2007) 403–408
Surface reaction of Bacillus cereus biomass and its biosorption
for lead and copper ions
PAN Jian-hua, LIU Rui-xia, TANG Hong-xiao∗
State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences,
Chinese Academy of Sciences, Beijing 100085, China. E-mail: firstname.lastname@example.org
Received 30 March 2006; revised 25 April 2006; accepted 29 April 2006
In this study, the surface chemical functional groups of Bacillus cereus biomass were identified by Fourier transform infrared (FTIR)
analytical technique. It had been shown that the B. cereus cells mainly contained carboxyl, hydroxyl, phosphate, amino and amide
functional groups. The potentiometric titration was conducted to explain the surface acid-base properties of aqueous B. cereus biomass.
The computer program FITEQL 4.0 was used to perform the model calculations. The optimization results indicated that three sites-
three pKas model, which assumed the cell surface to have three distinct types of surface organic functional groups based on the IR
analysis results, simulated the experimental results very well. Moreover, batch adsorption experiments were performed to investigate
biosorption behavior of Cu(II) and Pb(II) ions onto the biomass. Obviously, the adsorption equilibrium data for the two ions were
reasonably described by typical Langmuir isotherm.
Key words: Bacillus cereus; biosorption; Fourier transform infrared (FTIR); acid-base characteristic; heavy metals
Bacteria are common in many geologic environments
where they represent a significant proportion of the over-
all surface area exposed to fluids containing dissolved
solutes. Their cell walls contain a variety of surface
organic functional groups, which exhibit a high affinity
to bind metals (Beveridge and Murray, 1976, 1980; Fein
et al., 1997; Daughney et al., 2002) and other chemical
species (Daughney and Fein, 1998a; Fein and Delea,
1999). The ubiquity of bacterial cells in near-surface fluid-
rock systems and their ability to bind chemicals play a
significant role in many geochemical processes. They also
help in the subsurface transport of contaminants (Corap-
cioglu and Kim, 1995), the accumulation of metal deposits
(Savvichev et al., 1986), mineralization, and fossilization
of microorganisms (Ferris et al., 1988; Konhauser et al.,
1993; Fortin et al., 1997; Warren and Ferris, 1998).
Heavy metals are present in nature and industrial
wastewater. Due to their mobility in the natural water
ecosystem and their toxicity to organisms, the presence of
heavy metals in surface and groundwater causes a major
inorganic contamination problem that is of worldwide
concern (Chang et al., 1996). The behavior, transport, and
ultimate fate of heavy metal in natural systems depend
largely on the sorption with microorganisms, such as
bacteria, fungi, and yeast (Beveridge and Doyle, 1989;
Project supported by the National Natural Science Foundation of China
(No. 20537020, 20677073). *Corresponding author.
Poole and Gadd, 1989). It has been reported that different
types of biomass were capable of efficiently accumulating
heavy metal ions (Volesky and Holan, 1995). One of the
most important types of biosorbents is bacteria biomass.
The adsorption of heavy metals onto bacterial cell walls
has received considerable attention in recent experimental
and modeling studies, including several studies utilizing
site-specific surface complexation approaches (Fein and
Delea, 1997; Daughney and Fein, 1998b; Daughney et
al., 1998, 2002). As an essential part of describing these
biosorption phenomena, the investigations on the cell sur-
face appearance, chemical functional groups identification,
and acid-base characteristics of the biomass are necessary
for predicating metal biosorption behavior in the water
system and modifying metal biosorption property.
Therefore, acid-base titration and metal adsorption ex-
periments were carried out to explore the microbial surface
site reactions and thermodynamic properties of the organic
functional groups, which are displayed on Bacillus cereus
cell wall surfaces. An attempt was also made to analyze the
functional groups of bacterial surface using Fourier trans-
form infrared (FTIR); the knowledge of these functional
groups could be employed to explain the more probable
mechanism of metal immobilization on the cell wall.
1 Materials and methods
1.1 Metal solutions
Metal salts used for the batch adsorption experiment
were of analytical reagent grade: Pb(NO3)2, Cu(NO3)2.
408PAN Jian-hua et al. Vol. 19
IR spectroscopy result shows that the rod-shaped B.
cereus cell mainly contains carboxyl, hydroxyl, phos-
phate, amino, and amide functional groups. Based on
the results of potentiometric titration experiments and
surface complexation model calculation, it is shown
that three sites-three pKas model, as described by the
surface reactions, can reasonably describe the surface acid-
base behaviors of B. cereus biomass/water system. The
Langmuir isotherm can yield the best fit to absorption
experimental data for two metals on the biomass.
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