Biosorption of Ni (II) by Schizosaccharomyces pombe: kinetic and thermodynamic studies

The potential of the dried yeast, wild-type Schizosaccharomyces pombe, to remove Ni(II) ion was investigated in batch mode under varying experimental conditions including pH, temperature, initial metal ion concentration and biosorbent dose. Optimum pH for biosorption was determined as 5.0. The highest equilibrium uptake of Ni(II) on S. pombe, q _e, was obtained at 25 °C as 33.8 mg g⁻¹. It decreased with increasing temperature within a range of 25–50 °C denoting an exothermic behaviour. Increasing initial Ni(II) concentration up to 400 mg L⁻¹ also elevated equilibrium uptake. No more adsorption took place beyond 400 mg L⁻¹. Equilibrium data fitted better to Langmuir model rather than Freundlich model. Sips, Redlich–Peterson, and Kahn isotherm equations modelled the investigated system with a performance not better than Langmuir. Kinetic model evaluations showed that Ni(II) biosorption process followed the pseudo-second order rate model while rate constants decreased with increasing temperature. Gibbs free energy changes (ΔG°) of the system at 25, 30, 35 and 50 °C were found as −1.47E + 4, −1.49E + 4, −1.51E + 4, and −1.58E + 4 J mol⁻¹, respectively. Enthalpy change (ΔH°) was determined as −2.57E + 3 J mol⁻¹ which also supports the observed exothermic behaviour of the biosorption process. Entropy change (ΔS°) had a positive value (40.75 J mol⁻¹ K⁻¹) indicating an increase in randomness during biosorption process. Consequently, S. pombe was found to be a potential low-cost agent for Ni(II) in slightly acidic aqueous medium. In parallel, it has been assumed to act as a separating agent for Ni(II) recovery from its aqueous solution.     

Biosorption of cadmium and lead ions by ethanol treated waste baker's yeast biomass

The biosorption of cadmium and lead ions from artificial aqueous solutions using waste baker's yeast biomass was investigated. The yeast cells were treated with caustic, ethanol and heat for increasing their biosorption capacity and the highest metal uptake values (15.63 and 17.49 mg g(-1) for Cd(2+) and Pb(2+), respectively) were obtained by ethanol treated yeast cells. The effect of initial metal concentration and pH on biosorption by ethanol treated yeast was studied. The Langmuir model and Freundlich equation were applied to the experimental data and the Langmuir model was found to be in better correlation with the experimental data. The maximum metal uptake values (qmax, mg g(-1)) were found as 31.75 and 60.24 for Cd(2+) and Pb(2+), respectively. Competitive biosorption experiments were performed with Cd(2+) and Pb(2+) together with Cu(2+) and the competitive biosorption capacities of the yeast biomass for all metal ions were found to be lower than in non-competitive conditions.     

Biosorption of nickel(II) ions by using chemically pre-treated Sargassum filipendula biomass in a fixed bed column

The application of fixed bed adsorption is an important separation technique used for heavy metals in environmental pollution control. To design a fixed bed column, it is necessary to find dynamics data in the breakthrough curve form. The objective of this study was to model the biosorption process of nickel by using biomass of Sargassum filipendula in a fixed bed column. Experimental data were generated at 30°C, pH 3, flow rate of 6 ml/min and feed concentrations of 1, 1.5, 2, 3, 5 and 6 mequiv/l. Langmuir isotherm was used to represent the equilibrium data in the column (q _max = 2.496 mequiv/g, b = 0.456 l/mequiv) and in a batch operation of the system (q _max = 1.577 mequiv/g, b = 0.269 l/mequiv). These Langmuir parameters were used to simulate the continuous adsorption process of nickel. The partial differential equations model has taken into consideration the mass transfer resistance in the biosorbent as the key controlling phenomenon, which adequately represented the dynamic biosorption process of nickel.     

Biosorption of Nickel(II) from aqueous solution by the fungal mat of Trametes versicolor (rainbow) biomass: equilibrium, kinetics, and thermodynamic studies

This study investigates the equilibrium, kinetics and thermodynamics of Nickel(II) biosorption from aqueous solution by the fungal mat of Trametes versicolor (rainbow) biomass. The optimum biosorption conditions like pH, contact time, biomass dosage, initial metal ion concentration and temperaturewere determined in the batch method. The biosorbent was characterized by FTIR, SEM and BET surface area analysis. The experimental data were analyzed in terms of pseudo-first-order, pseudo-secondorder and intraparticle diffusion kinetic models, further it was observed that the biosorption process of Ni(II) ions closely followed pseudo-second-order kinetics. The equilibrium data of Ni(II) ions at 303, 313, and 323 K were fitted to the Langmuir and Freundlich isotherm models. Langmuir isotherm provided a better fit to the equilibrium data andthe maximum monolayer biosorption capacity of the T. versicolor(rainbow) biomass for Ni(II) was 212.5 mg/g at pH 4.0. The calculated thermodynamic parameters, ΔG^○, ΔH^○, and ΔS^○, demonstrated that the biosorption of Ni(II) ions onto the T. versicolor (rainbow) biomass was feasible, spontaneous and endothermic at 303 ～ 323 K. The performance of the proposed fungal biosorbent was also compared with that of many other reported sorbents for Nickel(II) removal and it was observed that the proposed biosorbent is effective in terms of its high sorption capacity.     

Biosorption of cadmium ions by different yeast species

Toxicity and accumulation of Cd2+ in yeasts were studied in eight different yeast species. The adaptation to toxic concentration of this metal was dependent on the production of extracellular yeast glycoproteins. The highest concentration of Cd2+ ions in the growth medium was tolerated by a Hansenula anomala, strain while the lowest tolerance was found by the strain of species Saccharomyces cerevisiae. Extracellular glycoproteins of Hansenula anomala absorbed nearly 90% of the total content of Cd2+ ions bound by yeast cells, while extracellular glycoproteins of Saccharomyces cerevisiae bound only 6% of the total amount of cadmium. This difference is caused by the variable composition of the saccharide moiety in the extracellular glycoproteins. The composition of extracellular glycoproteins changed during the adaptation of the yeast cells to the presence of Cd2+ ions.     

Biosorption of lead(II), cadmium(II), copper(II) and nickel(II) by anaerobic granular biomass

Biosorption is potentially an attractive technology for treatment of wastewater for retaining heavy metals from dilute solutions. This study investigated the feasibility of anaerobic granules as a novel type of biosorbent, for lead, copper, cadmium, and nickel removal from aqueous solutions. Anaerobic sludge supplied from a wastewater treatment plant in the province of Quebec was used. Anaerobic granules are microbial aggregates with a strong, compact and porous structure and excellent settling ability. After treatment of the biomass with Ca ions, the cation exchange capacity of the biomass was approximately 111 meq/100 g of biomass dry weight which is comparable to the metal binding capacities of commercial ion exchange resins. This work investigated the equilibrium, batch dynamics for the biosorption process. Binding capacity experiments using viable biomass revealed a higher value than those for nonviable biomass. Binding capacity experiments using non-viable biomass treated with Ca revealed a high value of metals uptake. The solution initial pH value affected metal sorption. Over the pH range of 4.0-5.5, pH-related effects were not significant. Meanwhile, at lower pH values the uptake capacity decreased. Time dependency experiments for the metal ions uptake showed that adsorption equilibrium was reached almost 30 min after metal addition. It was found that the q(max) for Pb2+, Cd2+, Cu2+, and Ni2+ ions, were 255, 60, 55, and 26 mg/g respectively (1.23, 0.53, 0.87, and 0.44 mmol/g respectively). The data pertaining to the sorption dependence upon metal ion concentration could be fitted to a Langmiur isotherm model. Based on the results, the anaerobic granules treated with Ca appear to be a promising biosorbent for removal of heavy metals from wastewater due to its optimal uptake of heavy metals, its particulate shape, compact porous structure, excellent settling ability, and its high mechanical strength.     

Biosorption of Cu(II) and Pb(II) ions from aqueous solution by natural spider silk

Aside from its excellent mechanical properties, spider silk (SS) would offer an active surface for heavy metal interaction due to its rich protein structure. The present study describes the potential use of natural (SS) as a sorbent of heavy metals from aqueous solutions. Single and multi-species biosorption experiments of heavy metals by natural SS were conducted using batch and column experiments. The biosorption kinetics, in general, was found to follow the second-order rate expression, and the experimental equilibrium biosorption data fitted reasonably well to Freundlich isotherm. From the Freundlich isotherm, the biosorption capacities of Cu(II) and Pb(II) ions onto SS were found as 0.20 and 0.007 mmol g?1, respectively. The results showed a decrease in the extent of metal ion uptake with lowering the pH.     

Binding of divalent metal ions to calcium-free peroxidase: thermodynamic and kinetic studies

Thermodynamics of binding of divalent metal ions including Ca(2+) , Mg(2+) , Ba(2+) , and Cd(2+) to Ca-free horseradish peroxidase (HRP) enzyme was investigated using UV/VIS spectrophotometry and molecular-mechanic (MM) calculations. According to the obtained binding and thermodynamic parameters, trend of the relative binding affinities of these divalent metal cations was found to be: Ca(2+) >Cd(2+) >Mg(2+) >Ba(2+) . Binding analysis based on Scatchard and Hill models showed positive cooperativity effect between the two distal and proximal binding sites. Furthermore, kinetics of binding and reconstitution process was examined (using relaxation-time method) for binding of Ca(2+) (as the typical metal ion) to Ca-free HRP, which was found a second-order type having a two-step mechanism involving fast formation of Ca-free HRP/1?Ca(2+) as the kinetic intermediate in step 1. Finally, by means of MM calculations, the comparative stability energies were evaluated for binding of M(2+) metal cations to Ca-free HRP. Based on MM calculations, preferential binding of Ca(2+) ion was occurred on distal and proximal binding sites of Ca-free HRP associated with higher stability energies (E(total) ). Indeed, among the divalent metal ions, Ca(2+) with the highest binding affinity (maximum value of K(bin) and minimum value of ΔG$\rm{{_{bin}^{0}}}$), maximum value of exothermic binding enthalpy, and stability energies stabilizes the HRP structure along with an optimized catalytic activity.     

Biosorption and desorption studies of chromium (III) by free and immobilized Rhizobium (BJVr 12) cell biomass

Experiments with free cell biomass (cells + exopolysaccharides) ofRhizobium BJVr 12 (mungbean isolate) showed that amount ofCr³⁺ ion sorbed is influenced by the amount of biomass toCr³⁺ concentration ratio and time of contact. A ratio of 0.5 gfresh biomass to 10.0 ml 5.03 ppm Cr³⁺ sorbed 0.0275 mg Crequivalent to an uptake of 2.86 mg Cr g-¹ dry biomass and 1.0g: 10.0 ml sorbed 0.0366 mg Cr equivalent to an uptake of 1.9 mg Crg-¹ biomass. Immobilized cell biomass in ceramic beads and inaquacel (a porous cellulose carrier with a charged surface) were moreefficient than free cell biomass in adsorbing Cr(III). A reduction of49.7percnt; of Cr(III) for free cells, 95.6% for cells immobilized inceramic beads and 94.6% for cells in aquacel was achieved after 48hours under shaken conditions. Sorption capacities of immobilized cellbiomass in ceramic beads and aquacel ranged from 5.01 to 5.06 mg Crg^-1 dry cell biomass. The biosorption of Cr³⁺follows generally the Langmuir and Freundlich models of adsorption at lowCr³⁺ concentrations. The Langmuir constant for immobilizedcells in ceramic beads are: Q₀, 0.065 mmol Crg^-1 biomass; b (affinity constant), - 694 lmmol^-1 Cr and for cells in aquacel Q, 0.07 mmol Crg^-1 biomass; b, - 694 l mmol Cr g^-1 Cr. TheFreundlich constants are: K, 0.071 mmol Cr g^-1 biomass; n,0.13 g^-1 biomass l^-1 and for aquacel: K, 0.074mmol g^-1 biomass; n, 0.13 g^-1 biomass. Biotrapsmade up of immobilized cells in ceramic beads and aquacel were tested foradsorbing Cr(III) using two different flow rates: 0.5 ml/min and 1.5 ml/min.A significantly higher amount of Cr(III) was adsorbed at the lower flow rateof 0.5 ml/min. Biosorption of Cr³⁺ is competitive. Thetreatment of a waste water sample containing 6.03 ppm Cr³⁺ andother cations with the biomass reduced the Cr³⁺ concentrationto that much lower than for the test solution containing only Cr. Recoveryof biosorbed Cr(III) was by treatment at a different pH using dilute HClsolution. Recovery was higher for cells imbibed in ceramic beads thanaquacel. Percentage recoveries for cells in aquacel are 46.4% at pH1.0, 33.0% at pH 3.0 and 6.6% at pH 6.0–7.0. For cellsin ceramic beads, percentage recoveries are: 93.1% at pH 1.0,75.6% at pH 3.0 and 16.4% at pH 6.0–7.0. Biosorption ofCr³⁺ by cells immobilized in ceramic beads is reversible butonly partially for cells in aquacel.     

Macrocyclic nickel(II) complexes: Spectroscopic studies and crystal structure of bis(difluoroboron-alpha-furilglyoximato)nickel(II)

Bis (difluoroboron - α - furilglyoximato) nickel (II), C₂₀H₁₂O₈N₄B₂F₄Ni, was prepared by cyclization of its hydrogen-bonded precursor with BF₃·OEt₂. The compound crystallizes in the space group P2₁/_c with a = 11.162(2), b = 5.569(2), c = 19.527(3) Å, β = 100.08(1)°, U = 1195.1(3) ų, and Z = 2. The structure was refined to an R value of 0.033 using 2371 unique reflections collected with a CAD4-SDP diffractometer system. Unlike the corresponding planar macrocyclic as well as hydrogen-bonded dimethylglyoximates, the title compound neither dimerizes not exhibits columnar stacked structure. The 14-member macrocycle is planar except the B atoms, and no metal-metal interactions are observed in this compound. The complexation and cyclization reactions were investigated using spectral data. The structure is compared with other macrocyclic complexes.     

Simultaneous determination of thermodynamic and kinetic parameters of aminopolycarbonate complexes of cobalt(II) and nickel(II) based on isothermal titration calorimetry data

The influence of the different side chain residues on the thermodynamic and kinetic parameters for complexation reactions of the Co²⁺ and Ni²⁺ ions has been investigated by using the isothermal titration calorimetry (ITC) technique supported by potentiometric titration data. The study was concerned with the 2 common tripodal aminocarboxylate ligands, namely, nitrilotriacetic acid and N‐(2‐hydroxyethyl) iminodiacetic acid. Calorimetric measurements (ITC) were run in the 2‐(N‐morpholino)ethanesulfonic acid hydrate (2‐(N‐morpholino) ethanesulfonic acid), piperazine‐N ,N ′‐bis(2‐ethanesulfonic acid), and dimethylarsenic acid buffers (0.1 mol L⁻¹, pH 6) at 298.15 K. The quantification of the metal‐buffer interactions and their incorporation into the ITC data analysis enabled to obtain the pH‐independent and buffer‐independent thermodynamic parameters (K , ΔG , ΔH , and ΔS ) for the reactions under study. Furthermore, the kinITC method was applied to obtain kinetic information on complexation reactions from the ITC data. Correlations, based on kinetic and thermodynamic data, between the kinetics of formation of Co²⁺ and Ni²⁺ complexes and their thermodynamic stabilities are discussed.     

Estimation of the ferrous-transferrin binding constants based on thermodynamic studies of nickel(II)-transferrin

The equilibrium constants for the binding of Ni2+ to human serum transferrin in 0.01 M hepes containing 5 mM sodium bicarbonate at 25 degrees C and pH 7.4 have been measured. The effective binding constants are log K1 = 4.10 +/- 0.15 and log K2 = 3.23 +/- 0.31 for the reactions Ni2+ + apoTr (K1) in equilibrium Ni2+-Tr. Ni2+ + Ni2+-Tr (K2) in equilibrium Ni2+-Tr-Ni2+ where the explicit terms for bicarbonate and hydrogen ion have been incorporated into the effective binding constants. Titration of both forms of mono(ferric)transferrin indicates that unlike other metal ions, Ni2+ binds preferentially to the N-terminal binding site, but that the site preference is rather small. A linear-free-energy relationship (LFER) for the complexation of Ni2+ and Fe2+ has been prepared. This LFER has been used to estimate effective binding constants of log K1 = 3.2 and log K2 = 2.5 for the ferrous-transferrin complex. These ferrous constants have been combined with the literature binding constants for ferric-transferrin to estimate formal reduction potentials of -340 mV vs. NHE for the C-terminal site and -280 mV for the N-terminal site.     

Biosorption of a textile dye (Acid Blue 40) by cone biomass of Thuja orientalis: estimation of equilibrium, thermodynamic and kinetic parameters

Biosorption of Acid Blue 40 (AB40) onto cone biomass of Thuja orientalis was studied with variation in the parameters of pH, contact time, biosorbent and dye concentration and temperature to estimate the equilibrium, thermodynamic and kinetic parameters. The AB40 biosorption was fast and the equilibrium was attained within 50 min. Equilibrium data fitted well to the Langmuir isotherm model in the studied concentration range of AB40 and at various temperatures. Maximum biosorption capacity (q(max)) for AB40 was 2.05 x 10(-4)mol g(-1) or 97.06 mg g(-1) at 20 degrees C. The changes of Gibbs free energy, enthalpy and entropy of biosorption were also evaluated for the biosorption of AB40 onto T. orientalis. The results indicate that the biosorption was spontaneous and exothermic. Kinetics of biosorption of AB40 was analyzed and rate constants were also derived and the results show that the pseudo-second-order kinetic model agrees very well with the experimental data.     

Metal binding by melanins: studies of colloidal dihydroxyindole-melanin, and its complexation by Cu(II) and Zn(II) ions

Melanins are colloidal pigments known to have a high affinity for metal ions. In this work, the nature of the metal-binding sites are determined and the binding affinities are quantified. Initial potentiometric titrations have been performed on synthetic dihydroxyindole (DHI) melanin solutions to determine the chemical speciation of quinole/quinone subunits. Two types of acidic functionalities are assignable: catechol groups, with pK(a) between 9 and 13, and quinone imines (QI), with pK(a) of 6.3. The presence of the quinone-imine tautomer has, to our knowledge, never been assessed in polymeric melanins. Melanin solutions obtained from N-methylated DHI lack the pK(a) 6.3 buffer, consistent with its inability to form the quinone-imine tautomer. EPR spectroscopy of the DHI-melanin samples demonstrates that the semiquinone radical is in too low a concentration to contribute to the bulk binding of metals. Changes in the titration curves after addition of Cu(II) and Zn(II) ions were analyzed to obtain the binding constants and stoichiometry of the metal-melanin complexes, using the BEST7 program. UV-Vis spectra at neutral and high pH are used to identify absorbances due to Cu-bound quinone imine and catechol groups. The derived binding constants were used to determine speciation of the Cu(II) and Zn(II) ions coordinated to the quinone imine and catechol groups at various pH. The mixed complexes, Zn(QI)(Cat)(-) and Cu(QI)(Cat)(-) are shown to dominate at physiological pH.     

Biosorption of cadmium (II) ions by immobilized cells of Pycnoporus sanguineus from aqueous solution

Biosorption of cadmium (II) ions from aqueous solution onto immobilized cells of Pycnoporus sanguineus (P. sanguineus) was investigated in a batch system. Equilibrium and kinetic studies were conducted by considering the effect of pH, initial cadmium (II) concentration, biomass loading and temperature. Results showed that the uptake of cadmium (II) ions increased with the increase of initial cadmium (II) concentration, pH and temperature. Langmuir, Freundlich and Redlich-Peterson isotherm models were used to analyze the equilibrium data at different temperatures. Langmuir isotherm model described the experimental data well followed by Redlich-Peterson and Freundlich isotherm models. Biosorption kinetics data were fitted using pseudo-first, pseudo-second-order and intraparticle diffusion. It was found that the kinetics data fitted well the pseudo-second-order followed by intraparticle diffusion. Thermodynamic parameters such as standard Gibbs free energy (Delta G0), standard enthalpy (Delta H0) and standard entropy (Delta S0) were evaluated. The result showed that biosorption of cadmium (II) ions onto immobilized cells of P. sanguineus was spontaneous and endothermic nature.     

Potential methods for selective accumulation of nickel(II) ions by plants

The selective uptake of nickel ions by certain plant species is described. The observed selectivity relative to metal ions such as cobalt and iron cannot be explained on the known binding constants to oxygen-donor ligands, e.g., citrate. Nitrogen donors are shown to have adequate selective interaction.     

Kinetic studies of the interaction of uranyl ions with inorganic pyrophosphatase from baker's yeast.

Kinetic measurements were performed to test the effect of uranyl ions on the enzymatic hydrolysis of pyrophosphate. A strong inhibition of the enzyme was found. From a Dixon-plot an inhibition competitive to the substrate magnesium pyrophosphate and an inhibitory constant of Ki = 3 . 10(-7) M was deduced.     

Biosorption of nickel (II) from effluent of electroplating industry by immobilized cells of Bacillus species

In this study, Ni (II) biosorption capacity of immobilized cells of Bacillus sp. was investigated. Biosorption of Ni (II) was carried out in batch experiments and the important environmental conditions were optimized. The uptake of metal was rapid, and equilibrium was attained within 270 min. Bacillus strains (ten cultures) were isolated from nickel electroplating effluent by heat shock method. These isolates were grown up in nutrient broth supplemented with Ni (II)(50 mg/L). The culture, exhibiting maximum biosorption capacity (q^max: 118 mg/g), was selected and labeled Bacillus Bio‐4. In order to develop an economical biosorption process cell mass of Bacillus, Bio‐4 was immobilized in Na‐alginate. It was concluded from the results that biosorption of nickel is highly dependent on the type of sorbent and experimental conditions employed. Our results demonstrate that 6.0 mg immobilized cells (18 mg cell biomass in 3.0 mL of 1% Na alginate) had a maximum biosorption capacity of 113 mg Ni(II) per liter of suspension at pH 8.0, 100 rpm and 25°C. The Ni (II) removal was estimated to be 97.4%.