Biosorption of Cr (VI) from aqueous solution by Rhizopus nigricans

The study was aimed to quantify the Cr sorption ability of powdered biomass of Rhizopus nigricans at the best operating conditions. The influence of solution pH, agitation, Cr (VI) concentration, biomass dosage, contact time, biomass particle size and temperature were studied. The optimum pH for biosorption of Cr (VI) was found to be 2.0. Higher adsorption percentage was noted at lower initial concentrations of Cr ions, while the adsorption capacity of the biomass increased with increasing concentration of ions. Optimum biomass dosage was observed as 0.5% (w/v). More than 75% of the ions were removed within 30 min of contact and maximum removal was obtained after 8 h. Biomass particles of smaller size (90 microm) gave maximum adsorption (99.2%) at 100 mg/l concentration. The adsorption capacity increased with increase in temperature and agitation speed and the optimum were determined as 45 degrees C at 120 rpm. Freundlich and Langmuir isotherms were used to evaluate the data and the regression constants were derived. The adsorption rate constant values (Kad) were calculated for different initial concentration of Cr ions and the sorption was found to be higher at lower concentration (100 mg/l) of metal ion.     

Process optimization of batch biosorption of lead using <Emphasis Type="Italic">Lactobacillius bulgaricus</Emphasis> in an aqueous phase system using response surface methodology

Response surface methodology (RSM) based on central composite rotatable design was used to investigate the effects of operating variable, mainly, pH, weight of biomass, and initial lead ion concentration on the lead adsorption capacity at ambient temperature using dried cells of Lactobacillius bulgaricus. Using RSM, quadratic polynomial equation was obtained for predicting the percent of lead ion removal. Analysis of variance showed that the effects of pH and weight of dried biomass were concluded to be the key factors influencing the capacity of lead ion removal. At pH lower than 2 (high acidic condition) and in alkaline condition, there is no significant biosorption. The optimum percent of lead ion removal was found at pH of 6.78, biomass concentration of 6.58 g/l and initial lead concentration 36.22 ppm. In this condition, percent of lead ion removal was 86.21%. This study showed RSM effectiveness for modeling of biosorption process.     

Biosorption of nickel(II) ions by baker's yeast: kinetic, thermodynamic and desorption studies

In this study, the biosorption of nickel(II) ion on deactivated protonated yeast was investigated as a function of temperature at different initial metal ion concentrations. The effect of temperature on the sorption was more significant at lower nickel(II) ion concentrations compared to higher concentrations. The protonated yeast biomass exhibited the highest nickel(II) ion uptake capacity at 27 degrees C at an initial nickel(II) ion concentration of 400mg/l and an initial pH of 6.75. The biosorption capacity decreased from 9.8 to 9.3mg/g at an initial nickel(II) ion concentration of 400mg/l, while at a lower initial concentration of 100mg/l, it decreased from 8.2 to 4.9 mg/g, as the temperature was increased from 27 degrees C to 60 degrees C. The equilibrium data fit better to the Freundlich and Redlich-Peterson isotherm models compared to the Langmuir model in the concentration range studied (10-400mg/l). Kinetic models applied to the sorption data at different temperatures showed that nickel(II) ion uptake process followed the pseudo-second order rate model and the adsorption rate constants decreased with increasing temperature. The activation energy of biosorption (Ea) was determined to be -13.3 kJ/mol using the pseudo-second order rate constants. The results indicated that the biosorption of nickel(II) ion on to baker's yeast was spontaneous and exothermic in nature. Desorption studies revealed that the protonated yeast biomass can be regenerated using 0.1N HCl and reused.     

Influence of Bentonite Proportion in Natural Clay on Pb2+ ions Sorption: Response Surface Methodology,Kinetics and Equilibrium Studies

The influence of natural clay's bentonite proportion on Pb²⁺ sorption capacity was investigated using response surface methodology (RSM), kinetics and equilibrium studies. Experiments were conducted at different initial pH (3–7), bentonite to clay ratio (0–100%), initial Pb²⁺ ions concentration (20–120 mg/L) and sorbent dosage (0.2–1 g). Under the RSM study, data obtained from 27 experiments undertaken were found to fitted second-order polynomial model (R² = 0.998 and R²-predicted = 0.994). Analysis of variance showed that the Pb²⁺ sorption capacity was influenced according to the order; initial concentration> mass of adsorbent > initial pH > bentonite proportion. Optimal operating conditions were obtained at initial pH 5, 0.2 g sorbent dosage, 30% bentonite to clay ratio and 100 mg/L Pb²⁺ ion concentration. Regardless of the bentonite proportion, Pb²⁺ sorption kinetics followed pseudo-second-order associated with intra-particle diffusion. The sorption isotherm for the clay which was described by Freundlich yielded higher adsorption capacity (25 mg/g) while that of the bentonite was described by Langmuir model with lower maximum sorption capacity of 15 mg/g. These results suggest that sorption of the Pb²⁺ ions was not likely to significantly impact on the removal of Pb²⁺ ions during electrokinetic remediation process of clay having different proportion of bentonite.     

The mechanism of cadmium removal from aqueous solution by nonmetabolizing free and immobilized live biomass of Rhizopus oligosporus

A preliminary study on the removal of cadmium by nonmetabolizing live biomass of Rhizopus oligosporus from aqueous solution is presented. The equilibrium of the process was in all cases well described by the Langmuir sorption isotherm, suggesting that the process was a chemical, equilibrated and saturable mechanism which reflected the predominantly site-specific mechanism on the cell surface. A curve of Scatchard transformation plots reflected the covalent nature of Cd²⁺ adsorption by the cells. The maximum cadmium uptake capacities were 34.25 mg/g for immobilized cells and 17.09 mg/g for free cells. Some factorial experiments in shake flasks were performed in order to investigate the effect of different initial cadmium concentrations and biomass concentrations on the equilibrium. Experimental results showed a reverse trend of the influence of the immobilized and free biomass concentration on the cadmium specific uptake capacity. The immobilized cells had a higher specific cadmium uptake capacity with increasing biomass concentrations compared to free cells. In a bioreactor, the cadmium uptake capacity of immobilized cells (q_max = 30.1–37.5 mg/g) was similar to that observed in shake flask experiments (q_max = 34.25 mg/g) whereas with free cells the bioreactor q_max of 4.8–13.0 mg/g; was much lower than in shake flasks (q_max = 17.09 mg/g), suggesting that cadmium biosorption by immobilized cells of R. oligosporus might be further improved in bigger reactors. EDAX and transmission electron microscopic experiments on the fungal biomass indicated that the presence of Cd²⁺ sequestrated to the cell wall was due to bioadsorption.     

Biosorptive removal of arsenic from drinking water

A biomass derived from the plant Momordica charantia has been found to be very efficient in arsenic(III) adsorption. An attempt was made to use this biomass for arsenic(III) removal under different conditions. The parameters optimized were contact time (5-150 min), pH (2-11), concentration of adsorbent (1-50 g/l), concentration of adsorbate (0.1-100mg/l), etc. It was observed that the pH had a strong effect on biosorption capacity. The optimum pH obtained for arsenic adsorption was 9. The influence of common ions such as Ca(2+), Mg(2+), Cd(2+), Se(4+), Cl(-), SO(4)(2-), and HCO(3)(-), at concentrations varying from 5 to 1000 mg/l was investigated. To establish the most appropriate correlation for the equilibrium curves, isotherm studies were performed for As(III) ion using Freundlich and Langmuir adsorption isotherms. The pattern of adsorption fitted well with both models. The biomass of M. charantia was found to be effective for the removal of As(III) with 88% sorption efficiency at a concentration of 0.5mg/l of As(III) solution, and thus uptake capacity is 0.88 mg As(III)/gm of biomass. It appears that this biomass should be used as a palliative food item. Further it also appears that the dietary habits may play a role in the toxic effects of ingested arsenic.     

Kinetic modeling for the biosorption of copper by pretreated Aspergillus niger biomass

In this present work, a kinetic model for biosorption of copper was developed considering the possibility of different forms of functional groups being present on the surface of the biomass prepared from Aspergillus niger. Results showed that metal uptake by A. niger was a mass transfer driven process, requiring only 30min to achieve 70% adsorption efficiency. Copper sorption by A. niger was influenced by the biomass dose, initial metal ion concentration, and pH of the solution. The Langmuir and Freundlich adsorption isotherms were used to describe the behavior of the system at different pH. The retention capacity of the biomass was determined at pH 6.0 to be equal to 23.62mg/g of biomass. The pretreatment with formalin improved the uptake of metal ion.     

Biosorption of cadmium and chromium in duckweed Wolffia globosa

The biosorption of cadmium (Cd) and chromium (Cr) by using dried Wolffia globosa biomass were investigated using batch technique. The effects of concentration and pH solution on the adsorption isotherm were measured by determining the adsorption isotherm at initial metal concentrations from 10 to 400 mg/L and pH 4 to 7 for Cd, and pH 1.5 to 6 for Cr. The adsorption equilibria were found to follow Langmuir models. The maximum adsorption capacity (Xm) at pH 7 in W. globosa-Cd system was estimated to be 80.7 mg/g, while the maximum removal achieved at pH 4, pH 5, and pH 6 were 35.1, 48.8, and 65.4 mg/g, respectively. The Xm at pH 1.5 in W. globosa--Cr system was estimated to be 73.5 mg/g, while the maximum removal achieved at pH 3, pH 5, and pH 6 were 47.4, 33.1, and 12.9 mg/g, respectively. The effects of contact times on Cd and Cr sorption indicated that they were absorbed rapidly and more efficiently at lower concentrations.     

Removal of lead from solution by the non-viable biomass of the water fern Azolla filiculoides

Non-viable biomass of the aquatic fern, Azolla filiculoides, removed up to 93 mg lead/g biomass from solution. Lead removal varied from 30% of the initial lead concentration at pH 1.5 to approximately 95% at pH values of 3.5 and 4.5. Lead removal decreased to 30% of the initial lead concentration if the lead concentration was initially over 400 mg/l. Lead removal remained at approximately 90% between 10 °C and 50 °C. Biomass concentration (4–8 mg/l) had little effect on lead removal. © Rapid Science Ltd. 1998     

Lead removal by Spirulina platensis biomass

In this investigation, we report on the biosorption of Pb (II) from aqueous solutions by the nonliving biomass of the micro-alga (cyanobacterium) Spirulina platensis. Propagation of the micro-alga was carried out in outside oblong raceway ponds. The biomass was cleaned, dried and used for the investigation. The effects of pH, adsorbent dose, temperature, initial concentration of Pb (II), and contact time on the adsorption of lead by the dry biomass were studied. The experiments were carried out in 250 ml conical flasks containing 100 ml of test solutions using an orbital incubator at 150 rpm. Concentrations of the metal before and after the experiments were measured using Atomic Absorption Spectrophotometer. Very high levels of Pb (II) removal (>91%) were obtained. The optimum conditions for maximal adsorption by S. platensis were found to be pH 3; 2 g of adsorbent dose; incubation at 26°C; 100 mg/l of lead initial concentration and 60 minutes of contact time. The experimental data fitted well with Freundlich isotherm equation with R² values greater than 0.97. Based on our results, we recommend the utilization of S. platensis biomass for heavy metal removal from aqueous solutions.     

Biosorption of lead and copper from aqueous solutions by pre-treated crab and arca shell biomass

Sorption potential of pretreated crab and arca shell biomass for lead and copper from aqueous media was explored. The effects of pH, initial concentration, biosorbent dosage and contact time were studied in batch experiments. Effects of common ions like sodium, potassium, calcium and magnesium on the sorption capacity of pretreated crab and arca biomasses were also studied. At equilibrium, the maximum uptake by crab shell biomass was 19.83+/-0.29 and 38.62+/-1.27 mg/g for lead and copper, respectively. In case of arca shell biomass the maximum uptake capacity was 18.33+/-0.44 mg/g and 17.64+/-0.31 mg/g for lead and copper, respectively. Combined effect of all the common ions up to 50 microg/ml concentration was negligible for both the metals using both biomasses. Sorption isotherms were studied to explain the removal mechanism of both elements by fitting isotherms data into Lagergren, Freundlich and Langmuir equations.     

Removal of lead(II) by Saccharomyces cerevisiae AUMC 3875

The removal of lead(II) from artificial aqueous solution using live and dead biomass of Saccharomyces cerevisiae AUMC 3875 was investigated. The minimum inhibitory concentration (MIC) value of S. cerevisiae AUMC 3875 for lead(II) was 600 mg/l. For live and dead biomass, maximum lead(II) uptake capacities were achieved at pH?5.0, initial metal ion concentration 300 mg/l, and biomass dosage 3 g/l. Maximum biosorption capacities were reached after 3 h and 20 min for live and dead cells, respectively. Fourier Transform Infrared spectroscopy (FTIR) results revealed the important role of C?=?O,? OH,? NH, protein amide II band, $ \mathrm{PO}_2^{-} $ , mannans, sulphur and sulphur-oxygen compounds in lead(II) uptake. Scanning electron microscopy analysis (SEM) showed that the cell surface morphology and surface area/volume ratio changed greatly after lead(II) uptake. Transmission electron microscopy analysis (TEM) confirmed the involvement of both extracellular adsorption and intracellular penetration through the cell wall. X-ray powder diffraction (XRD) analysis revealed the presence of Pb(SO₄),Pb₂OSO₄ by dead biomass and Pb₃O₂(SO₄),Pb₂OSO₄ by live biomass. Energy dispersive X-ray microanalysis (EDAX) confirmed the occurrence of sulphur, oxygen and lead(II) on the cell wall. The removal of lead(II) from storage battery industry wastewater was performed by dead biomass efficiently.     

Application of principal component analysis for the optimisation of lead(II) biosorption

Current study was focused on optimising lead(II) biosorption carried out by living cells of Arthrospira platensis using Principal Component Analysis. Various experimental conditions were considered: initial metal concentration (50 and 100 mg/l), solution pH (4.0, 4.5, 5.0, 5.5) and contact time (10, 20, 30, 40, 50 and 60 min) at constant rotary speed 200 rpm. It was found that when the biomass was separated from experimental solutions by the filtration, almost 50% of initial metal dose was removed by the filter paper. Moreover, pH was the most important parameter influencing examined processes. The Principal Component Analysis indicated that the most optimum conditions for lead(II) biosorption were metal initial concentration 100 mg/l, pH 4.5 and time 60 min. According to the analysis of the first component it might be stated that the lead(II) uptake increases in time. In overall, it was found to be useful for analysing data obtained in biosorption experiments and eliminating insignificant experimental conditions. Experimental data fitted Langmuir and Dubinin–Radushkevich models indicating that physical and chemical absorption take place at the same time. Further studies are necessary to verify how sorption–desorption cycles affect A. platensis cells.     

Effect of salinity on vanadate biosorption by Halomonas sp. GT-83: Preliminary investigation on biosorption by micro-PIXE technique

Thirty-eight soil samples were collected from crude oil contaminated land in south of Iran. Initial screening of a total of 100 bacterial isolates, resulted in the selection of one isolate with maximum adsorption capacity of 52.7 mg vanadate/g dry weight. It was tentatively identified as Halomonas sp. according to morphological and biochemical properties and named strain GT-83. Removal of vanadate by biosorption with Halomonas sp. GT-83 was very sensitive to solution pH. Vanadate adsorption decreased with increasing pH, with maximum adsorption capacities achieved in at pH 3.0 in the absence and in the presence of increasing concentrations of salt. Vanadate-salt biosorption studies were also performed at this pH value. Equilibrium uptakes of vanadate increased with increasing vanadate concentration up to 600 mg/l. Maximum metal removal (91.8%) took place at pH 3.0 with initial vanadate concentration of 100 mg/l, which got reduced (84.8%) in the presence of 50 g/l salt. The equilibrium sorption data were analyzed by using Freundlich isotherm. The specific uptake of vanadate increased at low cell concentration and decreased when cell concentration exceeded 0.75 g/l. The paper also demonstrates the potential value of micro-PIXE in biosorption studies.     

Characterization of Pb<Superscript>2+</Superscript> biosorption from aqueous solution by<Emphasis Type="Italic"> Rhodotorula glutinis</Emphasis>

The yeast Rhodotorula glutinis was examined for its ability to remove Pb(2+) from aqueous solution. Within 10 min of contact, Pb(2+) sorption reached nearly 80% of the total Pb(2+) sorption. The optimum initial pH value for removal of Pb(2+ )was 4.5-5.0. The percentage sorption increased steeply with the biomass concentration up to 2 g/l and thereafter remained more or less constant. Temperature in the range 15-45 degrees C did not show any significant difference in Pb(2+ )sorption by R. glutinis. The light metal ions such as Na(+), K(+), Ca(2+), and Mg(2+) did not significantly interfere with the binding. The Langmuir sorption model provided a good fit throughout the concentration range. The maximum Pb(2+ )sorption capacity q(max) and Langmuir constant b were 73.5 mg/g of biomass and 0.02 l/mg, respectively. The mechanism of Pb(2+) removal by R. glutinis involved biosorption by direct biosorptive interaction with the biomass through ion exchange and precipitation by phosphate released from the biomass.     

Improvement of heavy metal biosorption by mycelial dead biomasses (Rhizopus arrhizus, Mucor miehei and Penicillium chrysogenum): pH control and cationic activation

Abstract: Fungal mycelial by-products from fermentation industries present a considerable affinity for soluble metal ions (e.g. Zn, Cd, Ni, Pb, Cr, Ag) and could be used in biosorption processes for purification of contaminated effluents. In this work the influence of pH on sorption parameters is characterized by measuring the isotherms of five heavy metals (Ni, Zn, Cd, Ag and Pb) with Rhizopus arrhizus biomass under pH-controlled conditions. The maximum sorption capacity for lead was observed at pH 7.0 (200 mg g^-l), while silver uptake was weakly affected. The stability of metal-biosorbent complexes is regularly enhanced by pH neutralization, except for lead. A transition in sorption mechanism was observed above pH 6.0. In addition, comparison of various industrial fungal biomasses ( R. arrhizus, Mucor miehei and Penicillium chrysogenum indicated important variations in zinc-binding and buffering properties (0.24, 0.08 and 0.05 mmol g^−l, respectively). Without control, the equilibrium pH (5.8, 3.9 and 4.0) is shown to be related to the initial calcium content of the biosorbent, pH neutralization during metal adsorption increases zinc sorption in all fungi (0.57, 0.52 and 0.33 mmol g-l) but an improvement was also obtained (0.34, 0.33 and 0.10 mmol g⁻¹) by calcium saturation of the biomass before heavy metal accumulation. Breakthrough curves of fixed bed biosorbent columns demonstrated the capacity of the biosorbent process to purify zinc and lead solutions in continuous-flow systems, and confirmed the necessity for cationic activation of the biosorbent before contact with the heavy-metal solution.     

Adsorption and desorption of pentachlorophenol on cells of Mycobacterium chlorophenolicum PCP-1

The sorption behavior of pentachlorophenol (PCP) by the Gram-positive bacterium Mycobacterium chlorophenolicum PCP-1 was quantitatively characterized in this work, with emphasis on the effects of biomass and pH and on the reversibility of PCP adsorption. Both the adsorption and desorption of PCP showed a fast kinetic, reaching an equilibrium in less than 1.5-min mixing under the experimental conditions. For PCP concentrations up to 600 mumol/L no saturation of the adsorption was observed and the adsorption isotherms can be adequately described by the Freundlich equation. The adsorption capacity (q(ads)) of M. chlorophenolicum PCP-1 increased significantly with decreasing biomass in the low concentration range (below 0.5 g/L). The biomass concentration merely affected the capacity constant K of the Freundlich model while the intensity parameter n remained constant. The q(ads) also increased with decreasing pH, particularly at acidic pH values. Again, the pH effect was mainly reflected by the change of K. Based on these results a correlation for q(ads), in which K is a function of both biomass concentration and pH, was obtained to describe the adsorption isotherms at different biomass concentrations and pH values. The desorption of PCP was also found to be strongly affected by pH. At pH 5.4 the adsorption was almost completely irreversible, while a nearly complete desorption was obtained at pH 7. The effect of pH on the sorption behavior was found to be related to the ionization of PCP. The irreversibly adsorbed PCP is a strict function of concentration of undissociated PCP, while the reversibly adsorbed PCP correlates well with the concentration of ionic PCP. The irreversible adsorption has a much higher adsorption capacity than the reversible adsorption. These findings led to the derivation of a semimechanistic model that satisfactorily describes the sorption of PCP by M. chlorophenolicum. The results obtained also give clues to the patterns and mechanism(s) of PCP adsorption by microbial cells. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 480-489, 1997.     

Removal of cadmium(II) ion from aqueous system by dry biomass, immobilized live and heat-inactivated Oscillatoria sp. H1 isolated from freshwater (Mogan Lake)

Oscillatoria sp. H1 (Cyanobacteria, microalgae) isolated from Mogan Lake was used for the removal of cadmium ions from aqueous solutions as its dry biomass, alive and heat-inactivated immobilized form on Ca-alginate. Particularly, the effect of physicochemical parameters like pH, initial concentration and contact time were investigated. The sorption of Cd(II) ions on the sorbent used was examined for the cadmium concentrations within the range of 25-250 mg/L. The biosorption of Cd(II) increased as the initial concentration of Cd(II) ions increased in the medium up to 100 mg/L. Maximum biosorption capacities for plain alginate beads, dry biomass, immobilized live Oscillatoria sp. H1 and immobilized heat-inactivated Oscillatoria sp. H1 were 21.2, 30.1, 32.2 and 27.5 mg/g, respectively. Biosorption equilibrium was established in about 1 h for the biosorption processes. The biosorption was well described by Langmuir and Freundlich adsorption isotherms. Maximum adsorption was observed at pH 6.0. The alginate-algae beads could be regenerated using 50 mL of 0.1 mol/L HCl solution with about 85% recovery.     

Kinetic and Equilibrium Studies of Cr(VI) Biosorption by Dead <Emphasis Type="Italic">Bacillus licheniformis</Emphasis> Biomass

Many studies have been carried out on the biosorption capacity of different kinds of biomass. However, reports on the kinetic and equilibrium study of the biosorption process are limited. In our experiments, the removal of Cr(VI) from aqueous solution was investigated in a batch system by sorption on the dead cells of Bacillus licheniformis isolated from metal-polluted soils. Equilibrium and kinetic experiments were performed at various initial metal concentrations, pH, contact time, and temperatures. The biomass exhibited the highest Cr(VI) uptake capacity at 50°C, pH 2.5 and with the initial Cr(VI) concentration of 300 mg/g. The Langmuir and Freundlich models were considered to identify the isotherm that could better describe the equilibrium adsorption of Cr(VI) onto biomass. The Langmuir model fitted our experimental data better than the Freundlich model. The suitability of the pseudo first-order and pseudo second-order kinetic models for the sorption of Cr(VI) onto Bacillus licheniformis was also discussed. It is better to apply the pseudo second-kinetic model to describe the sorption system.