Studies on chromium(VI) adsorption-desorption using immobilized fungal biomass

Adsorption of surfactant micelles and Cd2+/Zn2+ in micellar-enhanced ultrafiltration

Micellar-enhanced ultrafiltration (MEUF) is a powerful treatment developed to remove heavy metals from wastewater. Efficient removal of Cd(2+)/Zn(2+) from wastewater was performed by MEUF using a polysulfone hollow ultrafiltration membrane, with sodium dodecyl sulfate (SDS) as the surfactant. The adsorption of surfactant micelles and Cd(2+)/Zn(2+) in MEUF was studied by changing the surfactant dosage and the Cd(2+)/Zn(2+) concentration in the feed. In addition, kinetics, adsorption isotherms, and thermodynamic rules were analyzed, and X-ray photoelectron spectroscopy (XPS) was conducted. It was found that when the Cd(2+)/Zn(2+) feed concentration was 50 mg/L, and the SDS dosage reached 2.15 g/L, the concentration of heavy metal ions in the permeate stabilized at around 1-4 mg/L, and the adsorption of Cd(2+)/Zn(2+) on SDS micelles followed second-order kinetics and the Langmuir isotherm laws. Adsorption is a spontaneous endothermic process in which the adsorption force is principally the attraction of opposite electrical charges.

Biosorption of uranium (VI) by immobilized Aspergillus fumigatus beads

Biosorption of uranium (VI) ions by immobilized Aspergillus fumigatus beads was investigated in a batch system. The influences of solution pH, biosorbent dose, U (VI) concentration, and contact time on U (VI) biosorption were studied. The results indicated that the adsorption capacity was strongly affected by the solution pH, the biosorbent dose and initial U (VI) concentration. Optimum biosorption was observed at pH 5.0, biosrobent dose (w/v) 2.5%, initial U (VI) concentration 60 mg L(-1). Biosorption equilibrium was established in 120 min. The adsorption process conformed to the Freunlich and Temkin isothermal adsorption models. The dynamic adsorption model conformed to pseudo-second order model.

Biosorption of lead using immobilized Aeromonas hydrophila biomass in up flow column system: factorial design for process optimization

Free and immobilized biomass of Aeromonas hydrophila has been utilized for the removal of Pb(II) from aqueous solution. Fitness of Langmuir sorption model to the sorption data indicated the sorption was monolayer and uptake capacity of biomass was 163.9 and 138.88 mg/g for the free and immobilized biomass respectively. 85.38% Pb(II) removal was achieved at bed height of 19 cm and flow rate of 2 mL/min and BDST model was in a good agreement with the experimental results (r(2)>0.997). An attempt has been made to optimize the process conditions for the maximum removal using Central Composite Design with the help of Minitab 15 software and the result predicted by optimization plots was 88.27% which is close to the experimental data i.e. 85.38%. Sorption-desorption studies revealed that polysulfone immobilized biomass could reused up to 16 cycles and bed was completely exhaust after 33 cycles.

Biosorption of copper(II) and cadmium(II) from aqueous solutions by free and immobilized biomass of Aspergillus niger

This study investigates the ability of Aspergillus niger resting cells entrapped into poly(vinyl alcohol) (PVA) network to remove Cu(II) and Cd(II) from single ions solutions. The performance of free and immobilized biosorbent was evaluated by equilibrium and kinetic studies. The PVA-immobilized fungal biosorbent removed Cu(II) and Cd(II) rapidly and efficiently with maximum metal removal capacities of 34.13 mg/g and 60.24 mg/g, respectively. These values of heavy metal uptake at equilibrium were higher than the amount of Cu(II) and Cd(II) removal by free biomass (17.60 mg/g and 69.44 mg/g, respectively). Biosorption equilibrium data were best described by Langmuir isotherm model. The biosorption kinetics followed the pseudo-second order model and intraparticle diffusion equation. The results obtained suggest that the immobilized biosorbent holds great potential for wastewater treatment applications.

Cadmium biosorption by polyvinyl alcohol immobilized recombinant Escherichia coli

Recombinant Escherichia coli expressing human metallothionein protein was immobilized with polyvinyl alcohol (PVA) for the removal of cadmium from solution. The adsorption ability was strongly affected by pH with optimal performance at pH 5.0, while it was less sensitive to temperature over the range of 20-42 degrees C. The adsorption kinetics and equilibrium of PVA-immobilized cells was best described by pseudo-second order model and Langmuir isotherm, respectively. Over the Cd concentrations range of 10-150 mg/l, PVA-cells had the highest Cd removal percentage (82.7%) at 10mg Cd/l and a biomass loading of 15.4 wt.%. Better adsorption ability was obtained when biomass loading was increased, as the highest adsorption capacity of 4.29 mg/g was achieved at 33.0 wt.% of biomass (initial Cd concentration=100mg/l). An aqueous solution of 0.01 M Na(3)NTA displayed the best desorption efficiency (57-89%) for four A/D cycles, while 51-61% of the original adsorption capacity was retained after regeneration.

Biosorption properties of hexavalent chromium on to biomass of tobacco-leaf residues

Equilibrium isotherms of Cr(VI) uptake by tobacco-leaf residues, under controlled solution pH and temperature, were obtained with batch uptake experiments. Batch uptake kinetics under different initial Cr(VI) concentrations was also obtained. The results showed that Cr(VI) uptake capacities of the tobacco-leaf residues were up to 113.2 mg g(-1) (dry wt). The uptake capacity was found to be dependent on solution pH and the maximum values were obtained at a pH of around 1.0. On the other hand, the effect of temperature the uptake capacity was found to be small. All equilibrium isotherms were well correlated with the standard Langmuir equation. Kinetics profiles showed that the uptake process was fast, and equilibrium was reached within 30 minutes of mixing contact. The role of polyphenols in Cr(VI) biosorption was studied and the results indicated that complex formation with Cr(VI) may be an important mechanism for Cr(VI) removal. The study indicated that abundantly available tobacco-leaf residues can be used as efficient biosorbent materials for Cr(VI) removal from wastewater.

Batch and continuous biosorption of Cu(2+) by immobilized biomass of Arthrobacter sp

The ability of free and polysulphone immobilized biomass of Arthrobacter sp. to remove Cu(2+) ions from aqueous solution was studied in batch and continuous systems. The Langmuir and Freundlich isotherm models were applied to the data. The Langmuir isotherm model was found to fit the sorption data indicating that sorption was monolayer and uptake capacity (Q(o)) was 175.87 and 158.7mg/g for free and immobilized biomass respectively at pH 5.0 and 30 degrees C temperature, which was also confirmed by a high correlation coefficient, a low RMSE and a low Chi-square value. A kinetic study was carried out with pseudo-first-order reaction and pseudo-second-order reaction equations and it was found that the Cu(2+) uptake process followed the pseudo-second-order rate expression. The diffusivity of Cu(2+) on immobilized beads increased (0.402x10(-4) to 0.435x10(-4)cm(2)/s) with increasing concentration from 50 to 150mg/L. The maximum percentage Cu(2+) removal (89.56%) and uptake (32.64mg/g) were found at 3.5mL/min and 20cm bed height. In addition to this the Bed Depth Service Time (BDST) model was in good agreement with the experimental data with a high correlation coefficient (>0.995). Furthermore, sorption and desorption studies were also carried out which showed that polysulphone immobilized biomass could be reused for up to six sorption-desorption cycles.

Selective removal of Cr(VI) ions from aqueous solutions including Cr(VI), Cu(II) and Cd(II) ions by 4-vinyl pyridine/2-hydroxyethylmethacrylate monomer mixture grafted poly(ethylene terephthalate) fiber

In this study, a new reactively fibrous adsorbent was prepared by grafting 4-vinyl pyridine (4-VP) and 2-hydroxyethylmethacrylate (HEMA) monomer mixture onto poly(ethylene terephthalate) (PET) fibers for removal of Cr(VI), Cu(II) and Cd(II) metal ions from aqueous solution by using batch adsorption method. The influence of various parameters such as graft yield (GY), pH, adsorption time, initial ion concentration and adsorption temperature was investigated. The selectivity of the reactive fiber was also examined. The results show that the adsorbed amount of metal ions followed as given in the order Cr(VI)>Cd(II)>Cu(II). At pH 3, Cr(VI) was removed by 99% while the initial concentration of ions was at 5 mg L(-1) and by 94% at 400 mg L(-1). It was found that the grafted fiber is more selective for Cr(VI) ions in the mixed solution of Cr(VI)-Cu(II), Cr(VI)-Cd(II) and Cr(VI)-Cu(II)-Cd(II) at pH 3 and it was observed that the grafted fibers are stable and regenerable by acid and base without losing their activity.

Sorption of Cr(VI) ions on two Lewatit-anion exchange resins and their quantitative determination using UV-visible spectrophotometer

The sorption of Cr(VI) from aqueous solutions with macroporous resins which contain quarternary amine groups (Lewatit MP 64 and Lewatit MP 500) was studied at varying Cr(VI) concentration, adsorbent dose, pH, contact time and temperature. Batch shaking sorption experiments were carried out to evaluate the performance of Lewatit MP 64 and Lewatit MP 500 anion exchange resins in the removal of Cr(VI) from aqueous solutions. The concentration of Cr(VI) in aqueous solution was determined by UV-visible spectrophotometer. The ion exchange process, which is dependent on pH, showed maximum removal of Cr(VI) in the pH range 3-7 for an initial Cr(VI) concentration of 1x10(-3) M. The optimum pH for Cr(VI) adsorption was found as 5.0 for Lewatit MP 64 and 6.0 for Lewatit MP 500. The maximum Cr(VI) adsorption at pH 5.0 is 0.40 and 0.41 mmol/g resin for Lewatit MP 64 and Lewatit MP 500 anion exchangers, respectively. The maximum chromium sorption occurred at approximately 60 min for Lewatit MP 64 and 75 min for Lewatit MP 500. The suitability of the Freundlich and Langmuir adsorption models was also investigated for each chromium-sorbent system. The uptake of Cr(VI) by the anion exchange resins was reversible and so it has good potential for the removal of Cr(VI) from aqueous solutions. Both ion exchangers had high bonding constants but Lewatit MP 500 showed stronger binding. The rise in the temperature caused a slight decrease in the value of the equilibrium constant (K(c)) for the sorption of Cr(VI) ion.

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 100mg/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.

Biotechnological potential of Azolla filiculoides for biosorption of Cs and Sr: Application of micro-PIXE for measurement of biosorption

The presence of Cs and Sr in culture medium of Azolla filiculoides caused about 27.4% and 46.3% inhibition of biomass growth, respectively, in comparison to A. filiculoides control weight which had not metals. Biosorption batch experiments were conducted to determine the Cs and Sr binding ability of native biomass and chemically modified biosorbents derived from Azolla namely ferrocyanide Azolla sorbents type 1 and type 2 (FAS1 and FAS2) and hydrogen peroxide Azolla sorbent (HAS). The best Cs and Sr removal results were obtained when A. filiculoides was treated by 2M MgCl(2) and 30ml H(2)O(2) 8mM at pH 7 for 12h and it was then washed by NaOH solution at pH 10.5 for 6h. Pretreatment of Azolla have been suggested to modify the surface characteristics which could improve biosorption process. The binding of Cs and Sr on the cell wall of Azolla was studied with micro-PIXE and FT-IR.

Removal of chromium (VI) using poly(methylacrylate) functionalized guar gum

Using persulfate/ascorbic acid redox pair, poly(methylacrylate) was grafted on to guar gum and the conditions for the grafting were optimized. The copolymer sample having maximum %G was evaluated for the removal of Cr(VI) and the sorption conditions were optimized. The sorption was found pH dependent, pH 1.0 being the optimum value. Sorption data at pH 1.0 were modeled using both the Langmuir and Freundlich isotherms where the data fitted better to Freundlich isotherm. The equilibrium sorption capacity of 29.67mg/g was determined from the Langmuir isotherm. The sorption followed a pseudo-second-order kinetics with a rate constant 2.5x10(-4)gmg(-1) min(-1). The grafted product was also evaluated for Cr(VI) removal from local electroplating industrial waste water. The regeneration experiments revealed that the guar-graft-poly(methylacrylate) could be successfully reused for five cycles. In the present study conductivity measurements were used instead of conventional photometric method for determining Cr(VI) concentration in the equilibrium solutions and the results obtained have been compared with photometric method. Optimum Cr(VI) binding under highly acidic conditions indicated significant contribution of non electrostatic forces in the adsorption process.

Removal of chromium (VI) from aqueous solution using walnut hull

In this study, removal of chromium (VI) from aqueous solution by walnut hull (a local low-cost adsorbent) was studied. The extent of adsorption was investigated as a function of solution pH, contact time, adsorbent and adsorbate concentration, reaction temperature and supporting electrolyte (sodium chloride). The Cr (VI) removal was pH-dependent, reaching a maximum (97.3%) at pH 1.0. The kinetic experimental data were fitted to the first-order, modified Freundlich, intraparticle diffusion and Elovich models and the corresponding parameters were obtained. A 102.78 kJ/mol Ea (activation energy) for the reaction of chromium (VI) adsorption onto walnut indicated that the rate-limiting step in this case might be a chemically controlled process. Both the Langmuir and Freundlich isotherms were suitable for describing the biosorption of chromium (VI) onto walnut hull. The uptake of chromium (VI) per weight of adsorbent increased with increasing initial chromium (VI) concentration up to 240-480 mg/L, and decreased sharply with increasing adsorbent concentration ranging from 1.0 to 5.0 g/L. An increase in sodium chloride (as supporting electrolyte) concentration was found to induce a negative effect while an increase in temperature was found to give rise to a positive effect on the chromium (VI) adsorption process. Compared to the various other adsorbents reported in the literature, the walnut hull in this study shows very good promise for practical applicability.

Sorption of hazardous metals from single and multi-element solutions by saltbush biomass in batch and continuous mode: interference of calcium and magnesium in batch mode

Batch studies were performed to determine the interference of calcium (Ca) and magnesium (Mg) on the sorption of Cu(II), Cd(II), Cr(III), Cr(VI), Pb(II), and Zn(II) [from CuSO(4), K(2)Cr(2)O(7), Pb(NO(3))(2), Cr(NO(3))(3), ZnCl(2), and Cd(NO(3))(2)] by saltbush (Atriplex canescens) biomass. The results demonstrated that Ca and Mg at concentrations of at least 20 times higher than the concentration of most of the target metals did not interfere with the metal binding. The data show that the batch binding capacity from a multimetal solution at pH 5.0 was (micromol/g) about 260 for Cr(III) and Pb, and about 117, 54, and 49 for Cu, Zn, and Cd, respectively. The use of 0.1M HCl allowed the recovery of 85-100% of the bound Cu, Cr(III), and Pb, and more than 37% of the bound Cd and Zn. The column binding capacity for Pb was about 49 micromol/g from both the single and multimetal solutions, while it was, respectively about 35 and 23 micromol/g for Cr(III). The binding capacity for Cu and Zn from the single and multimetal column experiments was 35 micromol/g and less than 10 micromol/g, respectively. The stripping data from the single column experiment showed that 0.1M HCl allowed the recovery of all the bound Cu and Zn, 90% and 74% of the bound Pb and Cr(VI), respectively, and less than 25% of the bound Cd and Cr(III), while the stripping from the multimetal experiment showed that 0.1M HCl allowed the recovery of all the bound Cu and about 74%, 54%, 43%, and 40% of the bound Pb, Zn, Cd, and Cr(III), respectively.

Poly(methylmethacrylate) grafted chitosan: An efficient adsorbent for anionic azo dyes

Present study reports on peroxydisulfate/ascorbic acid initiated synthesis of Chitosan-graft-poly(methylmethacrylate) (Ch-g-PMMA) and its characterization by FTIR, XRD and (13)C NMR. The copolymer remained water insoluble even under highly acidic conditions and was evaluated to be an efficient adsorbent for the three anionic azo dyes (Procion Yellow MX, Remazol Brilliant Violet and Reactive Blue H5G) over a wide pH range of 4-10 being most at pH 7. The adsorbent was also found efficient in decolorizing the textile industry wastewater and was much more efficient than the parent chitosan. Equilibrium sorption experiments were carried out at different pH and initial dye concentration values. The experimental equilibrium data for each adsorbent-dye system were successfully fitted to the Langmuir and Freundlich sorption isotherms. Based on Langmuir model Q(max) for yellow, violet and blue dyes was 250, 357 and 178, respectively. Thermodynamic parameters of the adsorption processes such as DeltaG degrees , DeltaH degrees , and DeltaS degrees were calculated. The negative values of free energy reflected the spontaneous nature of adsorption. The adsorption kinetic data of all the three dyes could be well represented by pseudo-second-order model with the correlation coefficients (R(2)) being 0.9922, 0.9997 and 0.9862, for direct yellow, reactive violet and blue dye, respectively with rate constants 0.91 x 10(-4), 1.82 x 10(-4) and 1.05 x 10(-4) g mg(-1)min(-1), respectively. At pH 7, parent chitosan also showed pseudo-second-order kinetics. The temperature dependence of dye uptake and the pseudo-second-order kinetics of the adsorption indicated that chemisorption is the rate-limiting step that controls the process.

Construction a hybrid biosorbent using Scenedesmus quadricauda and Ca-alginate for biosorption of Cu(II), Zn(II) and Ni(II): kinetics and equilibrium studies

The potential use of the immobilized fresh water algae (in Ca-alginate) of Scenedesmus quadricauda to remove Cu(II), Zn(II) and Ni(II) ions from aqueous solutions was evaluated using Ca-alginate beads as a control system. Ca-alginate beads containing immobilized algae were incubated for the uniform growth at 22 degrees C for 5d ays. Adsorption of Cu(II), Zn(II) and Ni(II) ions on the immobilized algae showed highest values at around pH 5.0. Adsorption of Cu(II), Zn(II) and Ni(II) ions on the immobilized algae increased as the initial concentration of metal ions increased in the medium. The maximum adsorption capacities of the immobilized algal biosorbents for Cu(II), Zn(II) and Ni(II) were 75.6, 55.2 and 30.4 mg/g (or 1.155, 0.933 and 0.465 mmol/g) biosorbent, respectively. When the heavy metal ions were in competition, the amounts of adsorbed metal ions were found to be 0.84 mol/g for Cu(II), 0.59 mol/g for Ni(II) and 0.08 mol/g for Zn(II), the immobilised algal biomass was significantly selective for Cu(II) ions. The adsorption-equilibrium was also represented with Langmuir, Freundlich and Dubinin-Radushkevich adsorption isotherms. The adsorption of Cu(II), Zn(II) and Ni(II) ions on the immobilized algae followed second-order kinetic.

Uptake of Re(VII) from aqueous solutions by Bacillus sp. GT-83-23

Thirty-eight water samples were collected from various areas of Anzali lagoon, Iran. Initial screening of a total of 100 bacterial isolates, resulted in the selection of one isolate with maximum adsorption capacity. It was tentatively identified as Bacillus sp. and named strain GT-83-23. The optimum pH of the medium was found to be 2.0 for Re(VII) adsorption. Uptakes of Re(VII) increased with increasing Re(VII) concentration and decreased sharply by the presence of increasing concentrations of NaCl. The kinetic of Re(VII) sorption by Bacillus sp. GT-83-23 was fast, reaching more than 62% of the total sorption capacity within 5 min. As the cell concentration increased, the amount of Re(VII) adsorbed by each cell (specific uptake) decreased, whereas the total amount of Re(VII) adsorbed enhanced. Cells immobilized in calcium alginate gel took up 77% of the Re(VII). The binding of Re(VII) on the Bacillus sp. GT-83-23 was studied with micro-PIXE.

Kinetic studies for the biosorption of lead and copper ions by Penicillium simplicissimum immobilized within loofa sponge

Biosorption potential of Penicillium simplicissimum (Penicillium sp.) immobilized within loofa sponge (PSILS) for lead and copper from aqueous media was explored. The effects of pH, contact time and initial concentration were studied in batch experiments. The maximum uptake of metal ions was obtained at pH 5.0. Biosorption equilibrium was established by 60 min. The pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models were applied to study the kinetics of the biosorption processes. The pseudo-second-order kinetic model provided the best correlation (R(2)>0.999) of the experimental data compared to the pseudo-first-order and intraparticle diffusion kinetic models. The maximum heavy metal ions adsorbed was found to be 152.6 and 112.3mg/g for Pb(II) and Cu(II), respectively. It was found that the biosorption of both Pb(II) and Cu(II) on PSILS was correlated well (R(Pb)(2)=0.999 and R(Cu)(2)=0.9978) with the Langmuir equation as compared to Freundlich isotherm equation under the concentration range studied. PSILS was regenerated by washing with a 100mM solution of HCl. The desorption efficiency was as high as 98%. The PSILS was reused in five adsorption-desorption cycles with negligible decrease in biosorption capacity. The present work showed that PSILS was an efficient biosorbent for removal of heavy metal ions from aqueous solution.

Novel chromium tolerant microorganisms: isolation, characterization and their biosorption capacity

Effluent from tannery, electroplating and electronic industries contain chromium which is highly toxic. This paper reports isolation of chromium tolerant microorganisms from solid waste as well as liquid effluent of an electroplating industry. Nine isolates were obtained that can tolerate chromium concentration up to 700 mg/L. They reach their stationary phase within 8-12h and can biosorb 95% of initial 200mg/L concentration of chromium within 4-10h. Fourier Transform Infra Red analysis of the biomass exposed to chromium indicates that amino and carboxylate groups in the biomass are involved in biosorption process. 16S RNA results of two most active organisms indicate that they are Bacillus marisflavi and Arthrobacter sp. and they show 98% and 96% homology similarity in the phylogenetic tree, respectively.

A new approach to study the decolorization of complex reactive dye bath effluent by biosorption technique

This work focused on the development of a practical biosorbent for the decolorization of textile effluents. The fermentation waste, Corynebacterium glutamicum biomass, when decarboxylated and immobilized in polysulfone matrix performed well in decolorization of simulated reactive dye bath effluent comprised of four different reactive dyes and other auxiliary chemicals. The regeneration of polysulfone-immobilized C. glutamicum was successful with the aid of 0.01 M NaOH as the eluant, which enabled the biosorbent to maintain consistent decolorization efficiency for up to 25 cycles. An up-flow packed column loaded with polysulfone-immobilized biomass performed well in the continuous treatment of Remazol effluent. Samples collected after 14 h of column operation revealed almost zero color and TOC. The column was also able to decrease the TDS level from 55,840 to 33,480 mg/L. Column regeneration experiments revealed that the biosorbent was able to continuously treat Remazol effluent over ten cycles, with more than 90.6% decolorization efficiency.

Interaction of chromium with resistant strain Aspergillus versicolor: investigation with atomic force microscopy and other physical studies

The interaction of chromium and a chromate resistant Aspergillus versicolor strain has been studied by atomic force (AFM) and transmission electron (TEM) microscopies. The nanomechanical properties such as cell wall rigidity and elasticity were measured by force spectroscopy and found to be 0.61 +/- 0.08 N/m, and 20.5 +/- 2.1 MPa, respectively. On chromium binding, ultrastuctural changes of the cell wall along with the formation of layered structures on the cell wall were observed. TEM and AFM micrographs demonstrate the accumulation of chromium on the cell wall, which were rough and irregular compared with the smooth pristine mycelia. The surface roughness, cell wall rigidity and elasticity increased to 35.5 +/- 3.5 nm, 0.88 +/- 0.05 N/m, and 62.5 +/- 3.5 MPa, respectively, from the corresponding values of 5.2 +/- 0.68 nm, 0.61 +/- 0.02 N/m, and 20.5 +/- 2.1 MPa for the pristine mycelia. X-ray photoelectron spectroscopy and Fourier transform infrared studies suggest that bound chromium was reduced to its trivalent state by the cell wall components. The reduced chromium species on the cell surface further electrostatically bind chromate ions forming layered structure on the cell wall.

Application of a magnetotactic bacterium, Stenotrophomonas sp. to the removal of Au(III) from contaminated wastewater with a magnetic separator

In this study, the feasibility of applying a magnetotactic bacterial isolate (MTB), Stenotrophomonas sp. to the removal of Au(III) was investigated. Biosorption experiments showed that Au(III) biosorption capacity exhibited no significant difference in the initial pH range of 1.0-5.5, while decreased more significantly in the initial pH range of 5.5-13.0. Langmuir isotherm indicated that the maximum Au(III) biosorption capacity of Stenotrophomonas sp. were 506, 369 and 308 mg g(-1) dry weight biomass at the initial pH values of 2.0, 7.0 and 12.0, respectively. Thiourea was proved to be an effective desorbent to recover Au from the MTB biomass and 91% Au adsorbed on the biomass could be recovered at equilibrium when the thiourea concentration was 0.8M. The magnetic separator developed by our research team used for separating Au loaded MTB biomass showed high separation efficiency, with 100% biomass removed at the magnetic intensity of 1200 Gs in 180 min. The analyses from FTIR and XRD further confirmed that the reduction of Au(III) to Au(0) by the reductants on the MTB biomass occurred, and the deposition of nano-crystal Au(0) particles, ranging from 24.7 to 31.4 nm, could be estimated on the biomass surface.

Biosorption of methylene blue from aqueous solution using free and polysulfone-immobilized Corynebacterium glutamicum: batch and column studies

The amino acid fermentation industry waste, Corynebacterium glutamicum, has been found to possess excellent biosorption capacity towards methylene blue (MB). Due to practical difficulties in solid-liquid separation and biomass regeneration, C. glutamicum was immobilized in a polysulfone matrix. The pH edge experiments revealed that neutral or alkaline pH values favored MB biosorption. Isotherm experiments indicated that C. glutamicum, when in immobilized state, exhibited slightly inferior dye uptake compared to free biomass. Also considering the two forms, immobilized biomass took a long time to attain equilibrium. An attempt to identify the diffusion limitations in immobilized beads was successful, with the Weber-Morris model clearly indicating intraparticle as the rate controlling step. Regeneration of the free biomass was not possible as it tended to become damaged under strong acidic conditions. On the other hand, immobilized biomass performed well with 99% desorption of MB from the biosorbent with the aid of 0.1 mol/l HCl. The immobilized biomass was also successfully regenerated and reused for three cycles without significant loss in sorption capacity. An up-flow packed column loaded with immobilized biomass was employed for the removal of MB. The column performed well in the biosorption of MB, exhibiting a delayed and favorable breakthrough curve with MB uptake and % removal of 124 mg/g biomass and 70.1%, respectively.

Low-cost supports used to immobilize fungi and reliable technique for removal hexavalent chromium in wastewater

The main goal of this study was to exploit low-cost and efficient sorbents for the removal and recovery of Cr(VI) in wastewater. Three supports of sawdust, polyurethane and alginate were applied to immobilize living and dead R. cohnii cells, respectively. There was a distinct increase in the Cr(VI) removal efficiency before and after the HCl-pretreatment. Langmuir adsorption isotherm model was well used to describe the distribution of Cr(VI) between the liquid and solid phases in batch studies. The values of q0 predicted by Thomas model were near to experimental ones in the experiments of packed column. The breakthrough curves calculated with this model were consistent well with experimental ones at a largely extent. Desorption, regeneration and reuse of the packed column were studied. After 5 cycles, adsorption capacity was still kept at higher level, reaching to 91.4, 87.9, 91.4 and 93.3mg/l contrasted with the first cycle (94.1, 90.4, 94.8 and 98.5mg/l) and the desorption efficiency were 85.0%, 96.2%, 93.4% and 91.4% compared with the first cycle (87.6%, 95.4%, 96.7% and 94.3%), corresponding to living cells immobilized with sawdust, polyurethane, and dead cells immobilized with polyurethane and alginate, respectively. The results indicated that the packed columns with the immobilized living and dead R. cohnii cells were the better option to adsorb, desorb and recover Cr(VI) from wastewater.

Competition of Reactive red 4, Reactive orange 16 and Basic blue 3 during biosorption of Reactive blue 4 by polysulfone-immobilized Corynebacterium glutamicum

Competition of Reactive red 4 (RR4), Reactive orange 16 (RO16) and Basic blue 3 (BB3) during biosorption of Reactive blue 4 (RB4) by polysulfone-immobilized protonated Corynebacterium glutamicum (PIPC) was investigated in batch and column mode of operations. Through potentiometric titrations, and with the aid of proton-binding model, carboxyl, phosphonate and amine were identified as functional groups of PIPC, with apparent pK(a) values of 3.47+/-0.05, 7.08+/-0.07 and 9.90+/-0.05 mmol/g, respectively. Since reactive dyes release dye anions (ROSO(3)(-)) in solutions, the positively charged amine groups were responsible for biosorption. PIPC favored biosorption at pH 3 when RB4 was studied/used as single-solute; while the presence of RR4 and RO16 severely affected the RB4 biosorption. When present as a single-solute, PIPC recorded 184.5mg RB4/g; while PIPC exhibited 126.9, 120.9 and 169.6 mg RB4/g in the presence of RR4, RO16 and BB3, respectively. In general, the accessibility of amine group depends on the molecular size, number of sulfonate groups and reactivity of each reactive dye. Single and multicomponent Freundlich equations successfully described the biosorption isotherms. With 0.1M NaOH, it is possible to reuse PIPC for RB4 biosorption in 10 repeated cycles. Column experiments in an up-flow packed column coincided with batch results, that is PIPC showed strong preference towards highly reactive and relatively small RB4 anions; however, the presence of competing dyes hinder the RB4 column biosorption performance.

Removal of chromium (VI) from aqueous solution using treated oil palm fibre

This study proposed an oil palm by-product as a low-cost adsorbent for the removal of hexavalent chromium [Cr (VI)] from aqueous solution. Adsorption of Cr (VI) by sulphuric acid and heat-treated oil palm fibre was conducted using batch tests. The influence of pH, contact time, initial chromium concentration and adsorbent dosage on the removal of Cr (VI) from the solutions was investigated. The optimum initial pH for maximum uptake of Cr (VI) from aqueous solution was found to be 1.5. The removal efficiency was found to correlate with the initial Cr (VI) concentration, adsorbent dosage as well as the contact time between Cr (VI) and the adsorbent. The adsorption kinetics tested with pseudo first order and pseudo second order models yielded high R(2) values from 0.9254 to 0.9870 and from 0.9936 to 0.9998, respectively. The analysis of variance (ANOVA) showed significant difference between the R(2) values of the two models at 99% confidence level. The Freundlich isotherm (R(2)=0.8778) described Cr (VI) adsorption slightly better than the Langmuir isotherm (R(2)=0.8715). Difficulty in desorption of Cr (VI) suggests the suitability of treated oil palm fibre as a single-use adsorbent for Cr (VI) removal from aqueous solution.

Biosorption of trivalent chromium by free and immobilized blue green algae: kinetics and equilibrium studies

The process of biosorption of trivalent chromium (Cr(3+)) by live culture of Spirulina platensis and the sorption potential by the dried biomass, in both free and immobilized states have been investigated for a simulated chrome liquor in the concentration range of 100-4500 ppm. Both live and dried biomass were very good biosorbents as they could remove high amounts of chromium from tannery wastewater. Polyurethane foam and sodium alginate were used as immobilizing agents and their performances compared. Biosorption kinetic data on Cr(3+) sorption onto dried biomass were analyzed using pseudo-first-and pseudo-second-order kinetic models in batch column experiments. The second-order equation was more appropriate to predict the rate of biosorption. Subsequently, the effects of height of packing & diameter of the column, concentration of blue-green algae (BGA) in varying amounts of sodium alginate, chromium concentration were studied. The results fit into both Langmuir & Freundlich isotherm models with very high regression coefficients. Furthermore, equilibrium studies using retan chrome liquor (RCL), with a chromium concentration of 1660 ppm, obtained from a tannery also showed promising results. In general, our studies indicate the efficacy of the algal species in removal of chromium from tannery wastewater.

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.

Application of response surface methodology to cell immobilization for the production of palatinose

Response surface methodology (RSM), based on multivariate non-linear model, was applied to study the interactions and optimization of the immobilization parameters for cell entrapment, namely alginate concentration, cell loading and bead diameter using Erwinia rhapontici NCPPB 1578 that produced palatinose. ANOVA analysis and statistical parameters calculations showed that RSM could be used effectively to model and improve a complex system like cell immobilization. Palatinose yield was increased by 40%. The maximum yield of 140 mg/ml was achieved in a batch of 1h at alginate concentration of 5% w/v, cell loading of 5 g l(-1) and 2.25 mm bead diameter. Thus, the E. rhapontici NCPPB 1578 immobilization in alginate bead and subsequent palatinose yield was successfully improved by application of RSM technique.

Efficient multicyclic sorption and desorption of lead ions on facilely prepared poly(m-phenylenediamine) particles with extremely strong chemoresistance

Nitric acid, hydrochloric acid and EDTA were carefully chosen as desorbent to systematically evaluate the adsorption/desorption performance of the Pb(2+)-adsorbing fine microparticles of poly(m-phenylenediamine). The sorption/desorption efficiency was maximized by optimizing desorption condition including the desorbent concentration, contact time, and desorption mode. The variation of the solution pH with Pb(2+) desorption was recorded to speculate the desorption mechanism. The practical reusability of the microparticles was elaborated through the sorption-desorption cycle experiments in an optimum condition. It was found that the desorption was very rapid with an equilibrium time of several minutes. A strong dependence of the desorbability on the species and concentration of the desorbents was observed. When 20 mM EDTA was chosen as the desorbent, the highest desorptivity was up to 94.2% that was much higher than those using nitric and hydrochloric acids. A successive sorption-desorption study employing nitric acid indicated that the microparticles could be simply regenerated and reutilized for more than 5 cycles together with Pb(2+) re-adsorption efficiency of about 50% and accumulative Pb(2+) adsorption capacity of up to 720.4 mg L(-1). Facilely prepared, extremely chemoresistant and cost-effective PmPD microparticles would be potentially used for multicyclic sorption of lead ions from aqueous solution.

Biosorption of reactive black 5 by Corynebacterium glutamicum biomass immobilized in alginate and polysulfone matrices

Corynebacterium glutamicum, a lysine fermentation industry waste, showed promise for the removal of Reactive black 5 (RB5). Due to practical difficulties in solid-liquid separation, the free biomass was immobilized in two polymer matrices: calcium alginate and polysulfone. Initially, the optimization of biomass loading in polymeric beads and bead dosage were examined. Of the different combinations examined, 4% (with bead dosage of 2 g per 40 ml) and 14% (with bead dosage of 1 g per 40 ml) in the case of alginate and polysulfone beads, respectively, were identified as the optimal conditions. According to the Langmuir model, at pH 1, the maximum RB5 uptakes of 352, 282 and 291 mg g(-1) were observed for free, alginate and polysulfone-immobilized biomass, respectively. According to the Weber-Morris model, intraparticle diffusion was found to be the potential rate limiting step for the immobilized beads. Regeneration experiments, with 0.01 M NaOH and Na(2)CO(3) as eluents, revealed that polysulfone beads exhibited invariable RB5 uptake capacity and very high mechanical stability even at the end of twentieth cycle, confirming the technical feasibility of the biosorption process for industrial applications.