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1.
In this study, bioaccumulation and heavy metal resistance of Cd 2+, Cu 2+, Co 2+ and Mn 2+ ions by thermophilic Geobacillus thermantarcticus and Anoxybacillus amylolyticus was investigated. The bacteria, in an order with respect to metal resistance from the most resistant to the most sensitive, was found to be Mn 2+ > Co 2+ > Cu 2+ > Cd 2+ for both G. thermantarcticus and A. amylolyticus. It was determined that the highest metal bioaccumulation was performed by A. amylolyticus in Mn 2+ (28,566 μg/g dry weight), and the lowest metal bioaccumulation was performed by A. amylolyticus in Co 2+ (327.3 μg/g dry weight). The highest Cd 2+ capacities of dried cell membrane was found to be 36.07 and 39.55 mg/g membrane for G. thermantarticus and A. amylolyticus, respectively, and the highest Cd 2+ capacities of wet cell membrane was found to be 14.36 and 12.39 mg/g membrane for G. thermantarcticus and A. amylolyticus, respectively. 相似文献
2.
Complexes formed by reduced glutathione (GSH) with metal cations (Cr 2+, Mn 2+,Fe 2+,Co 2+,Ni 2+,Cu 2+,Zn 2+,Cd 2+,Hg 2+) were systematically investigated by the density functional theory (DFT). The results showed that the interactions of the metal cations with GSH resulted in nine different stable complexes and many factors had an effect on the binding energy. Generally, for the same period of metal ions, the binding energies ranked in the order of Cu 2+>Ni 2+>Co 2+>Fe 2+>Cr 2+>Zn 2+>Mn 2+; and for the same group of metal ions, the general trend of binding energies was Zn 2+>Hg 2+>Cd 2+. Moreover, the amounts of charge transferred from S or N to transition metal cations are greater than that of O atoms. For Fe 2+,Co 2+,Ni 2+,Cu 2+,Zn 2+,Cd 2+ and Hg 2+ complexes, the values of the Wiberg bond indices (WBIs) of M-S (M denotes metal cations) were larger than that of M-N and M-O; for Cr 2+ complexes, most of the WBIs of M-O in complexes were higher than that of M-S and M-N. Furthermore, the changes in the electron configuration of the metal cations before and after chelate reaction revealed that Cu 2+, Ni 2+,Co 2+ and Hg 2+ had obvious tendencies to be reduced to Cu +,Ni +,Co + and Hg + during the coordination process. 相似文献
3.
The present work deals with the biosorption performance of dried and non-growing biomasses of Exiguobacterium sp. ZM-2, isolated from soil contaminated with tannery effluents, for the removal of Cd 2+, Ni 2+, Cu 2+, and Zn 2+ from aqueous solution. The metal concentrations studied were 25 mg/l, 50 mg/l, 100 mg/l, 150 mg/l and 200 mg/l. The effect of solution pH and contact time was also studied. The biosorption capacity was significantly altered by pH of the solution. The removal of metal ions was conspicuously rapid; most of the total sorption occurred within 30 min. The sorption data have been analyzed and fitted to the Langmuir and Freundlich isotherm models. The highest Q max value was found for the biosorption of Cd 2+ at 43.5 mg/g in the presence of the non-growing biomass. Recovery of metals (Cd 2+, Zn 2+, Cu 2+ and Ni 2+) was found to be better when dried biomass was used in comparison to non-growing biomass. Metal removal through bioaccumulation was determined by growing the bacterial strain in nutrient broth amended with different concentrations of metal ions. This multi-metal resistant isolate could be employed for the removal of heavy metals from spent industrial effluents before discharging them into the environment. 相似文献
4.
Dolomite collected from Surat Thani Province in Thailand was investigated for use as a sorbent for the removal of divalent heavy metal cations from an aqueous solution. The sorbent had a surface area of 2.46 m 2/g and a pH of zero point charge (pHzpc) of 9.2. Batch sorption was used to examine the effect of the pH (pH 3–7) on the sorption capacity of Cd 2+, Pb 2+ and Zn 2+, alone or together as an equimolar mixture at various concentrations. Alone, each heavy metal cation was adsorbed faster at a higher pH, where the sorption of Cd 2+ and Pb 2+ fitted a Langmuir isotherm, but Zn 2+ sorption best fitted a Freundlich isotherm. Under equimolar competitive sorption, the sorption capacity of each cation was decreased by 75.8% (0.29–0.07 mM/g), 82.8% (0.53–0.09 mM/g), and 95.7% (0.84–0.04 mM/g) for Cd 2+, Pb 2+ and Zn 2+, respectively, compared to that with the respective single cation. Desorption of these heavy metal cations from dolomite was low, with an average desorption level of 0.06–17.4%. Furthermore, since dolomite is readily available and rather cheap, it is potentially suitable for use as an efficient sorbent to sorb Cd 2+ and Pb 2+, and perhaps Zn 2+, from contaminated water. 相似文献
5.
One key step of the bioremediation processes designed to clean up heavy metal contaminated environments is growing resistant
cells that accumulate the heavy metals to ensure better removal through a combination of biosorption and continuous metabolic
uptake after physical adsorption. Saccharomyces cerevisiae cells can easily act as cation biosorbents, but isolation of mutants that are both hyperaccumulating and tolerant to heavy
metals proved extremely difficult. Instead, mutants that are hypersensitive to heavy metals due to increased and continuous
uptake from the environment were considered, aiming to use such mutants to reduce the heavy metal content of contaminated
waters. In this study, the heavy metal hypersensitive yeast strain pmr1∆ was investigated for the ability to remove Mn 2+, Cu 2+, Co 2+, or Cd 2+ from synthetic effluents. Due to increased metal accumulation, the mutant strain was more efficient than the wild-type in
removing Mn 2+, Cu 2+, or Co 2+ from synthetic effluents containing 1–2 mM cations, with a selectivity $ {\text{Mn}}^{{{\text{2}} + }} > {\text{Co}}^{{{\text{2}} + }} ~ > {\text{Cu}}^{{{\text{2}} + }} $ {\text{Mn}}^{{{\text{2}} + }} > {\text{Co}}^{{{\text{2}} + }} ~ > {\text{Cu}}^{{{\text{2}} + }} and also in removing Mn 2+ and Cd 2+ from synthetic effluents containing 20–50 μM cations, with a selectivity Mn 2+ > Cd 2+. 相似文献
6.
The aim of this paper was to describe the effect of various metal ions on the activity of protocatechuate 3,4-dioxygenase from Stenotrophomonas maltophilia KB2. We also compared activity of different dioxygenases isolated from this strain, in the presence of metal ions, after induction by various aromatic compounds. S. maltophilia KB2 degraded 13 mM 3,4-dihydroxybenzoate, 10 mM benzoic acid and 12 mM phenol within 24 h of incubation. In the presence of dihydroxybenzoate and benzoate, the activity of protocatechuate 3,4-dioxygenase and catechol 1,2-dioxygenase was observed. Although Fe 3+, Cu 2+, Zn 2+, Co 2+, Al 3+, Cd 2+, Ni 2+ and Mn 2+ ions caused 20–80 % inhibition of protocatechuate 3,4-dioxygenase activity, the above-mentioned metal ions (with the exception of Ni 2+) inhibited catechol 1,2-dioxygenase to a lesser extent or even activate the enzyme. Retaining activity of at least one of three dioxygenases from strain KB2 in the presence of metal ions makes it an ideal bacterium for bioremediation of contaminated areas. 相似文献
7.
Heavy metal ions (Pb 2+, Cd 2+, Mn 2+, Cu 2+, and Cr 2O 7 2?) were biosorbed by brown seaweeds ( Hizikia fusiformis, Laminaria japonica, and Undaria pinnatifida) collected from the southern coast of South Korea. The biosorption of heavy metal ions was pH-dependent showing a minimum absorption at pH 2 and a maximum biosorption at pH 4 (Pb 2+, Cd 2+, Mn 2+, and Cr 2O 7 2?) or pH 6 (Cu 2+). Biosorption increased most noticeably for pH changes from 2 to 3. In the latter pH range, biosorption increased, because a higher pH decreased the electrostatic repulsion between metal ions and functional groups on the seaweed. In the pH range of 2 ~ 4, biosorption of negatively-charged chromium species (Cr 2O 7 ?2) followed the pattern of positively-charged metal ions (Pb 2+, Cd 2+, Mn 2+, and Cu 2+). This suggests that the most prevalent chromium species were positively-charged Cr 3+, reduced from Cr 6+ in Cr 2O 7 ?2. Whereas positively-charged heavy metal ions (Pb 2+, Cd 2+, Mn 2+, and Cu 2+) reached a plateau after the maximum level, biosorption of chromium ions decreased noticeably between pH 5 and 8. Kinetic data showed that biosorption by brown seaweed occurred rapidly during the first 10 min, and most of the heavy metals were bound to the seaweed within 30 min. Equilibrium adsorption data for a lead ion could fit well in the Langmuir and Freundlich isotherm models with regression coefficients ( R 2) between 0.93 and 0.98. 相似文献
8.
The potentials of Adansonia digitata root powders (ADRP) for adsorption of Pb 2+, Cd 2+ and Cu 2+ from aqueous solutions was investigated. Physico-chemical analysis of the adsorbent (ADRP) shows that hydroxyl, carbonyl and amino groups were predominant on the surface of the adsorbent. Scanning Electron Microscope (SEM) image revealed its high porosity and irregular pores in the adsorbent while the Energy Dispersive X-ray Spectrum showed the major element with 53.0% Nitrogen, 23.8% carbon, 9.1% calcium, 7.5% potassium and 6.6% magnesium present. The found optimal conditions were: initial concentration of the metal ions = 0.5 mg/L, pH = 5, contact time = 90 min, adsorbent dose = 0.4 g and particle size = 32 µm. Freundlich isotherm showed good fit for the adsorption of Pb 2+, Cd 2+ and Cu 2+. Dubinin-Radushkevich isotherm revealed that the adsorption processes were physisorption Cd(II) and Cu(II) but chemisorption with respect to Pb(II) ions. The kinetics and thermodynamic studies showed that Pseudo-second order and chemisorptions provided the best fit to the experimental data of Pb (II) ions only. Batch desorption result show that desorption in the acidic media for the metal ions were more rapid and over 90% of the metal ions were recovered from the biomass. 相似文献
9.
A water‐soluble, high‐output fluorescent sensor, based on a lumazine ligand with a thiophene substituent for Cd 2+, Hg 2+ and Ag + metal ions, is reported. The sensor displays fluorescence enhancement upon Cd 2+ binding (log β = 2.79 ± 0.08) and fluorescence quenching by chelating with Ag + and Hg 2+ (log β = 4.31 ± 0.15 and 5.42 ± 0.1, respectively). The mechanism of quenching is static and occurs by formation of a ground‐state non‐fluorescent complex followed by rapid intersystem crossing. The value of the Stern–Volmer quenching rate constant ( kq) by Ag + ions is close to 6.71 × 10 12 mol/L/s at 298 K. The thermodynamic parameters ( ΔG, ΔH and ΔS) were also evaluated and indicated that the complexation process is spontaneous, exothermic and entropically favourable. The quantitative linear relationship between the softness values of Klopman ( σK) or Ahrland ( σA) and the experimental binding constants ( β) being in the order of Hg 2+ > Ag + > Cd 2+ suggests that soft–soft interactions are the key for the observed sensitivity and selectivity in the presence of other metal ions, such as: Pb 2+, Ni 2+, Mn 2+, Cu 2+, Co 2+, Zn 2+ and Mg 2+ ions. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
10.
Acutolysin D, isolated from the venom of Agkistrodon acutus, possesses marked haemorrhagic and proteolytic activities. The molecular weight and the absorption coefficients ( A
1%
280) of acutolyisn D have been determined to be 47,850 ± 8 amu and 9.3 by mass spectrometer and UV spectrum, respectively. The effects of metal ions on the conformation and activity of acutolysin D have been studied by following fluorescence, circular dichroism and biological activity measurements. Acutolysin D contains two Ca 2+-binding sites and two Zn 2+-binding sites determined by atomic absorption spectrophotometer. Zn 2+ is essential for the enzyme activities of acutolysin D, however, the presence of 1 m M Zn 2+ significantly decreases its caseinolytic activity and intrinsic fluorescence intensity at pH 9.0 due to Zn(OH) 2 precipitate formation. Ca 2+ is important for the structural integrity of acutolysin D, and the presence of 1 m M Ca 2+ markedly enhances its caseinolytic activity. Interestingly, the caseinolytic activity which is inhibited partly by Cu 2+, Co 2+, Mn 2+ or Tb 3+ and inhibited completely by Cd 2+, is enhanced by Mg 2+. The fluorescence intensity of the protein decreases in the presence of Cu 2+, Co 2+, Cd 2+ or Mn 2+, but neither for Ca 2+, Mg 2+ nor for Tb 3+. Zn 2+, Ca 2+, Mg 2+, Cu 2+, Mn 2+, Co 2+ and Tb 3+ have slight effects on its secondary structure contents. In addition, Cd 2+ causes a marked increase of antiparallel β-sheet content from 45.5% to 60.2%. 相似文献
11.
Bioaccumulation and heavy metal resistance of Cd 2+, Cu 2+, Ni 2+, Zn 2+ and Mn 2+ ions by thermophilic Geobacillus toebii subsp. decanicus and Geobacillus thermoleovorans subsp. stromboliensis were investigated. The metal resistance from the most resistant to the most sensitive was found as Mn > Ni > Cu > Zn > Cd
for both Geobacillus thermoleovorans subsp . stromboliensis and Geobacillus toebii subsp. decanicus. It was determined that the highest metal bioaccumulation was performed by Geobacillus toebii subsp. decanicus for Zn (36,496 μg/g dry weight cell), and the lowest metal bioaccumulation was performed by Geobacillus toebii subsp. decanicus for Ni (660.3 μg/g dry weight cell). Moreover, the dead cells were found to biosorbe more metal in their membranes compared
to the live cells. In the presence of 7.32 mg/l Cd concentration, the levels of Cd absorbed in live and dead cell membranes
were found as 17.44 and 46.2 mg/g membrane, respectively. 相似文献
12.
In liver homogenate the biosynthesis of N-acetylneuraminic acid using N-acetylglucosamine as precursor can be followed stepwise by applying different chromatographic procedures. In this cell-free system 16 metal ions (Zn 2+, Mn 2+, La 3+, Co 2+, Cu 2+, Hg 2+, VO
3
–
, Pb 2+, Ce 3+, Cd 2+, Fe 2+, Fe 3+, Al 3+, Sn 2+, Cs + and Li +) and the selenium compounds, selenium(IV) oxide and sodium selenite, have been checked with respect to their ability to influence a single or possible several steps of the biosynthesis of N-acetylneuraminic acid. It could be shown that the following enzymes are sensitive to these metal ions (usually applied at a concentration of 1 mmoll –1): N-acetylglucosamine kinase (inhibited by Zn 2+ and vandate), UDP- N-acetylglucosamine-2-epimerase (inhibited by zn 2+, Co 2+, Cu 2+, Hg 2+, VO
3
–
, Pb 2+, Cd 2+, Fe 3+, Cs +, Li +, selenium(IV) oxide and selenite), and N-acetylmannosamine kinase (inhibited by Zn 2+, Cu 2+, Cd 2+, and Co 2+). Dose dependent measurements have shown that Zn 2+, Cu 2+ and selenite are more efficient inhibitors of UDP- N-acetylglucosamine-2-epimerase than vanadate. As for the N-acetylmannosamine kinase inhibition, a decreasing inhibitory effect exists in the following order Zn 2+, Cd 2+, Co 2+ and Cu 2+. In contrast, La 3+, Al 3+ and Mn 2+ (1 mmoll –1) did not interfere with the biosynthesis of N-acetylneuraminic acid. Thus, the conclusion that the inhibitory effect of the metal ions investigated cannot be regarded as simply unspecific is justified.Dedicated to Professor Theodor Günther on the occasion of his 60th birthday 相似文献
13.
31P-nmr has been used to investigate the specific interaction of three divalent metal ions, Mg 2+, Mn 2+, and Co +2, with the phosphate groups of DNA. Mg 2+ is found to have no significant effect on any of the 31P-nmr parameters (chemical shift, line-width, T1, T2, and NOE) over a concentration range extending from 20 to 160 m M. The two paramagnetic ions, Mn 2+ and Co 2+, on the other hand, significantly change the 31P relaxation rates even at very low levels. From an analysis of the paramagnetic contributions to the spin–lattice and spin–spin relaxation rates, the effective internuclear metal–phosphorus distances are found to be 4.5 ± 0.5 and 4.1 ± 0.5 Å for Mn 2+ and Co 2+, respectively, corresponding to only 15 ± 5% of the total bound Mn 2+ and Co 2+ being directly coordinated to the phosphate groups (inner-sphere complexes). This result is independent of any assumptions regarding the location of the remaining metal ions which may be bound either as outer-sphere complexes relative to the phosphate groups or elsewhere on the DNA, possibly to the bases. Studies of the temperature effects on the 31P relaxation rates of DNA in the absence and presence of Mn 2+ and Co 2+ yielded kinetic and thermodynamic parameters which characterize the association and dissociation of the metal ions from the phosphate groups. A two-step model was used in the analysis of the kinetic data. The lifetimes of the inner-sphere complexes are 3 × 10 ?7 and 1.4 × 10 ?5 s for Mn 2+ and Co 2+, respectively. The rates of formation of the inner-sphere complexes with the phosphate are found to be about two orders of magnitude slower than the rate of the exchange of the water of hydration of the metal ions, suggesting that expulsion of water is not the rate-determining step in the formation of the inner-sphere complexes. Competition experiments demonstrate that the binding of Mg 2+ ions is 3–4 times weaker than the binding of either Mn 2+ or Co 2+. Since the contribution from direct phosphate coordination to the total binding strength of these metal ion complexes is small (~15%), the higher binding strength of Mn 2+ and Co 2+ may be attributed either to base binding or to formation of stronger outer-sphere metal–phosphate complexes. At high levels of divalent metal ions, and when the metal ion concentration exceeds the DNA–phosphate concentration, the fraction of inner-sphere phosphate binding increases. In the presence of very high levels of Mg 2+ (e.g., 3.1 M), the inner-sphere ? outer-sphere equilibrium is shifted toward ~100% inner-sphere binding. A comparison of our DNA results and previous results obtained with tRNA indicates that tRNA and DNA have very similar divalent metal ion binding properties. A comparison of the present results with the predictions of polyelectrolyte theories is presented. 相似文献
14.
Summary The uptake kinetics and intracellular location of cobalt ( 60Co), manganese ( 54Mn) and zinc ( 65Zn) have been characterized in Chlorella salina. Uptake of all three metals was biphasic. The initial rapid phase was independent of light, temperature or the presence of metabolic inhibitors. This first phase of metabolism-independent biosorption was followed by a slower phase of uptake that was apparently dependent on metabolism and decreased by incubation in the dark, or in the light at low temperature or in the presence of metabolic inhibitors. This latter phase of metal accumulation followed Michaelis-Menten kinetics. However, when expressed in the form of a Lineweaver-Burk plot two distinct phases were apparent for each metal with the following K m values ( M); Co 2+, 19 and 266; Mn 2+, 2 and 760; Zn 2+, 4 and 635. For all three metals cellular compartmentation analysis showed that large amounts of metal were bound to intracellular components and to the cell wall. There was also a higher concentration of each metal in the vacuole than in the cytosol, indicating transport of the metals across the tonoplast which may, in part, account for the multi-phasic uptake systems detected. The influence of competing divalent ions on the active uptake of Co 2+ and Mn 2+ was also studied. When the concentration of divalent ion was the same as that of Co 2+ the uptake of the latter was not affected, indicating a specific system for the uptake of Co 2+. However, Mn 2+ uptake inhibited by Mg 2+, Zn 2+ and Cd 2+, but not by Co 2+, which indicated that Mn 2+, Mg 2+ and Cd 2+ may enter the cells via a common system with different affinities for each metal. 相似文献
15.
Thermostable dipeptidase from Bacillus stearothermophilus, a typical metalloenzyme containing 1.0g atom of Zn per mole of subunit of the dimeric enzyme was markedly activated by exogenous divalent metal ions such as Mn 2+, Co 2+, and Cd 2+ . In contrast, several others including Ba 2+, Hg 2+, and Cu 2+ considerably inhibited the enzyme, even the inherent metal, Zn 2+, being slightly inhibitory. To study the metal-binding properties of this dipeptidase, the enzyme was completely resolved to the inactive, Zn-free apoenzyme by treatment with EDTA in the presence of guanidine hydrochloride in a weakly acidic buffer. The apoenzyme was readily reconstituted by incubation with either Zn 2+, Mn 2+, or Co 2+, restoring the catalytic activity. The Mn-reconstituted enzyme had nearly twice the activity of the original Zn-enzyme. Combined with kinetic analyses of reconstitution of the apoenzyme with metal ions, these results show that the enzyme has two non-identical metal-binding sites, each with a different property. Furthermore, substitution of Mn 2+ or Co 2+ for Zn 2+ considerably lowered the thermostability of the enzyme without affecting the overall conformation of the enzyme protein, suggesting that the prosthetic Zn is playing dual roles in conformational stability and catalysis of the thermostable dipeptidase. 相似文献
16.
Marine algae—as inexpensive and renewable natural biomass—have attracted the attention of many investigators to be used to preconcentrate and biosorb many heavy metal ions. Impressed by this concept, the metal uptake capacity of Egyptian marine algae was examined using representatives of green and brown algae, namely, Ulva lactuca L. and Sargassum latifolium (Turner) C. Agardh, respectively. The biosorption efficiencies of Cu 2+, Co 2+, Ni 2+, Cd 2+, Hg 2+, Ag 2+, and Pb 2+ ions seem to depend on the type of the algae used as well as the conditions under which the uptake processes were conducted. It was demonstrated that a pH range of 7.5–8.8 was optimum for the removal of the tested metals. Similarly, the uptake process was markedly accelerated during the first 2 h using relatively low metal level and sufficient amounts of the dried powdered tested algae. 相似文献
17.
Copper-induced metallothionein (MT) synthesis in Saccharomyces cerevisiae was investigated in order to associate this exclusively with Cu 2+
in vivo, when cultured in nutrient medium containing other heavy metal ions. Expression of the CUP1 promoter/ lacZ fusion gene was inhibited by all heavy metal ions tested, especially Cd 2+ and Mn 2+. By adding Cd 2+ and Mn 2+ at 10 M concentration, the -galactosidase activity decreased by about 80% and 50% of the maximum induction observed with 1 mM CuSO 4, respectively. Furthermore, cell growth was markedly inhibited by combinations of 1 mM-Cu 2+ and 1 M-Cd 2+. Therefore, the yeast S. cerevisiae could not rely on MT synthesis as one of the copper-resistance mechanisms, when grown in a Cd 2+ environment. In contrast, the presence of Mn 2+ in the nutrient medium showed alleviation rather than growth inhibition by high concentrations of Cu 2+. The recovery from growth inhibition by Mn 2+ was due to decreased Cu 2+ accumulation. Inhibitory concentrations of Co 2+, Ni 2+ and Zn 2+ on expression of the CUP1p/ lacZ fusion gene were at least one order of magnitude higher than that of Cd 2+ and Mn 2+. These results are discussed in relation to Cu 2+ transport and Cu-induced MT synthesis in the copper-resistance mechanism of the yeast S. cerevisiae. 相似文献
18.
An industrial strain of Saccharomyces cerevisiae collected from the waste of a brewing industry was used to remove lead, cadmium and copper from aqueous solutions (1?m m). Metal removal efficiency by using either biomass suspension directly diluted into the metal solutions or biomass previously incubated and washed in distilled water was compared. In all experiments with unwashed biomass a shift in the medium pH from 4.5 to a final value in the 7.0–8.0 range occurred. This pH increase was responsible for a metal precipitation effect associated to the metal biosorption. A very different pH profile was observed when washed biomass was used leading to different removal profiles for Cd 2+ and Pb 2+ and a similar one for Cu 2+. In the absence of biomass, medium components and/or the excreted intracellular products proved to interfere in the metal removal and to be responsible for 80% Pb 2+ precipitation, in the pH 4.5–5.0 range. To initial metal solution pH, leading to the lowest residual ion concentrations, after 96?h of contact with unwashed biomass and in the absence of pH adjustment, was 4.5–5.0. Continuous or stepwise adjustment of medium pH to this range during the process was unfavourable for metal removal, being the continuous adjustment the worst procedure. In this case, Cd 2+ was not biosorbed and Cu 2+ removal decreased from 76 to 33%. However, Pb 2+ was always extensively removed (89%) and only slightly affected by pH control. The global results suggest different removal mechanisms for each cation. Cu 2+ was removed by both metal sorption and precipitation, due to the pH shift that occurred during the process, while Cd 2+ removal showed to be completely dependent of this pH shift. Pb 2+ was totally and quickly removed, by precipitation, in the presence of the biomass suspension and at pH 4.5. Moreover, the biosorbent changes occurring during the process played an important role in the metal removal when non-viable microbial biomass is used. 相似文献
19.
Heavy metal sequestration by a multimetal resistant Pseudomonas strain isolated from a uranium mine was characterized for its potential application in metal bioremediation. 16S rRNA gene analysis revealed phylogenetic relatedness of this isolate to Pseudomonas fluorescens. Metal uptake by this bacterium was monophasic, fast saturating, concentration and pH dependent with maximum loading of 1048 nmol Ni 2+ followed by 845 nmol Co 2+, 828 nmol Cu 2+ and 700 nmol Cd 2+ mg ?1 dry wt. Preferential metal deposition in cell envelope was confirmed by TEM and cell fractionation. FTIR spectroscopy and EDX analysis revealed a major role of carboxyl and phosphoryl groups along with a possible ion exchange mechanism in cation binding. Binary system demonstrated selective metal binding affinity in the order of Cu 2+ > Ni 2+ > Co 2+ > Cd 2+. A comparison with similar metal uptake reports considering live bacteria strongly indicated the superiority of this strain in metal sequestration, which could be useful for developing efficient metal removal system. 相似文献
20.
This paper reports the synthesis of azomethine-modified gold nanoparticles with azomethine (azomethine-AuNPs) in aqueous media, which were characterized by FT-IR spectroscopy, ultraviolet–visible spectroscopy (UV-Vis), dynamic light scattering (DLS), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). The azomethine-AuNPs were employed as colorimetric for Cr3+ and Co2+ ions at pH 6.2–7.5 and 8.1–9.1, at room temperature in aqueous solution. In the presence of Cr3+ and Co2+, the azomethine-AuNPs induce aggregation of the nanoparticles. Upon aggregation, the surface plasmon absorption band red-shifts so that the nanoparticle solution appears a blue color. The sensitivity of azomethine-AuNPs towards other metal ions, Mg2+, Mn2+, Cr6+, Na+, Ni2+, Ag+, Al3+, Ca2+, Cd2+, Cu2+, Fe2+, Fe3+, Hg2+, Cd2+, K+, Co3+, Ni2+, Pb2+, and Zn2+ are negligible. This highly selective sensor allows a direct quantitative assay of Co2+ and Cr3+ with colorimetric detection limits of 83.22 and 108 nM, respectively. 相似文献
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