Microbial and plant derived biomass for removal of heavy metals from wastewater

Effect of amendments on phytoavailability and fractionation of copper and zinc in a contaminated soil

The ability of amendments to modify the soil properties and influence plants to immobilise Cu and Zn was studied in a naturally contaminated, additionally spiked podzolic soil. Lolium perenne L (perennial rye grass), Festuca rubra L (creeping red fescue) and Poa pratensis L (Kentucky blue grass) were tested in a pot study in the presence of soil amendments (lime, phosphate, and compost, individually and in combination) to assess the effect of soil-plant-amendment interaction on phytostabilisation. The ability of treatments to stabilize metals was assessed on the basis of metal fractionation in soil, partitioning of metals in plants, and metal uptake by the plants. Significant partitioning of Cu into immobile forms occurred as a result of the growth of Festuca rubra, and of Zn by the growth of Poa pratensis. Application of lime significantly reduced the exchangeable fraction of Zn, whereas phosphate application had an accelerating effect on exchangeable Cu. With combined application of amendments, the plant metal concentration decreased by more than 40% for Cu and 70% for Zn, compared to soils receiving no amendments. Combined application of amendments, in conjunction with growth of Festuca and Poa, can be recommended for phytostabilising of Cu and Zn in moderately contaminated acid soils of southwest British Columbia.

Characterization of metal removal by os sepiae of Sepiella maindroni Rochebrune from aqueous solutions

To develop low cost metal adsorbents with less secondary pollution, metal adsorption from the aqueous solutions by the raw os sepiae (ROS) and alkali (NaOH)-pretreated OS (APOS) of the cuttlefish (Sepiella maindroni Rochebrune) was characterized. The capacities of adsorption of ROS and APOS were estimated to be 299.26 mg Cu g(-1) and 299.58 mg Cu g(-1), respectively. Metal adsorption by OS was significantly improved by appropriately increasing initial pH in the solution but hardly affected by temperature change within a wide range of 15-45 degrees C. Cu adsorption of both ROS and APOS was well described neither by Langmuir model nor by Freundlich model. Metal adsorption by OS fell in the order of Fe > Cu approximately = Cd > Zn in the solution with mixed metals, but followed the sequence of Cd > Cu > Fe approximately = Zn in the solutions respectively, with a single metal of Fe, Cu, Cd and Zn. The changes in Ca amounts in OS and solutions in adsorption strongly correlated with removal efficiencies of the metals. Obvious shifts of stretching bands of numbers of groups in OS after and before adsorption and the pretreatment occurred. It was concluded: (1) that metal adsorption by OS involves ion exchange, which occurred mainly between Ca rather than K and Na that OS itself contains and metals that were added in the solution, (2) that metal adsorption-promoting effects by NaOH pretreatment likely involve deprotonation of surface groups in OS, exposure of more functional groups, and increase in specific surface areas and (3) that related mechanisms for adsorption also likely include surface complexation, electrostatic adsorption and even micro-deposition. The results also indicated that OS is a very promising absorbent for metal removal from electroplating wastewater.

Biosequestration via cooperative binding of copper by Ralstonia pickettii

Ralstonia pickettii isolated from copper-contaminated lake sediment are adapted to high levels of copper after 100 years of selective pressure. Two R. pickettii strains (12D and 12J) were selected for the studies reported herein due to their distinct differences in genomic structure, different metal resistance patterns and carriage of a filamentous phage. Copper sequestration studies revealed that these strains could bind up to 27.44 (12D) and 38.19 (12J) mg copper per g dry weight of cells and that viable cells sequestered more copper than heat-killed cells. Viable cells and heat-killed cells had significantly different saturation binding curves, indicating that one or more unique copper sequestration mechanism(s) was involved in binding by viable cells. Electron microscopy showed alteration of cell outer envelope after cells were grown in the presence of copper, suggesting that the accumulation of copper was membrane associated. X-ray Absorption Near Edge Structure and Extended X-ray Absorption Fine Structure revealed that the copper sequestered was present as Cu(II) and bound to oxygen and/or nitrogen. Recent completion of the genome sequence revealed that an approximately 220 kb region was enriched with metal resistance and transporter genes found in multiple copies. Comparative sequence analysis revealed that several genes may have been derived from horizontal transfer. Hence, rapid adaptation of R. pickettii to high concentrations of metal appears due to robust gene duplication and importation of several types of resistance determinants.

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 nickel(II) from aqueous solution by brown algae: equilibrium, dynamic and thermodynamic studies

The biosorption characteristics of nickel(II) ions using the brown algae (Cystoseria indica, Nizmuddinia zanardini, Sargassum glaucescens and Padina australis) were investigated. Experimental parameters affecting the biosorption process such as pH level, contact time, initial metal concentration and temperature were studied. The equilibrium data fitted very well to the Langmuir adsorption model in the concentration range of nickel(II) ions and at all the temperatures studied. Evaluation of the experimental data in terms of biosorption dynamics showed that the biosorption of nickel(II) onto algal biomass followed the pseudo-second-order dynamics well. The calculated thermodynamic parameters (Delta G degrees, Delta H degrees and DeltaS degrees) showed that the biosorption of nickel(II) ions were feasible, spontaneous and endothermic at the temperature ranges of 293-313 K.

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.

Isotherms, kinetics and thermodynamic studies of adsorption of Cu2+ from aqueous solutions by Mg2+/K+ type orange peel adsorbents

Orange peel (OP) was used as raw material to prepare two novel adsorbents: MgOP (Mg(2+) type orange peel adsorbent) and KOP (K(+) type orange peel adsorbent). FTIR and SEM were used to characterize the adsorbents. Effects of pH, solid/liquid ratio, time and metal ion concentration on the Cu(2+) adsorption by these two adsorbents were investigated. The isotherms data were analyzed using the Langmuir, Freudlich, Temkin and Dubinin-Radushkevich models. Langmuir model provides the best correlation for the adsorption of Cu(2+) by both MgOP and KOP, and the mono-layer adsorption capacity for Cu(2+) removal by MgOP and KOP are 40.37 and 59.77 mg/g, respectively. The adsorbed amounts of Cu(2+) increased with the increase in contact time and reached equilibrium within 20 min. The kinetics data were analyzed using four adsorption kinetic models: the pseudo-first and second-order equations, the Elovich equation and intraparticle diffusion equation. Results show that the pseudo-second-order equation fits the experimental data very well. Thermodynamic studies showed the spontaneous and exothermic nature of the adsorption of Cu(2+) by MgOP and KOP.

Heavy metal removal potential of dried Salvinia biomass

Investigations were carried out to evaluate heavy metal adsorption capacity of Salvinia. Batch experiments showed that dry plant biomass possess good potential to adsorb heavy metals such as Ni, Co, Cr, Fe, and Cd. The metal adsorption increased with increase in initial metal concentration. The data obtained fitted well with Freundlich equilibrium isotherm. Further characterization of plant biomass showed presence of both acidic and basic surface functionalities that might facilitate binding of metal ions. Fourier transform infrared (FTIR) spectra of plant biomass suggested involvement of carbonyl (C=O), carboxyl (-COO), and hydroxyl (-OH) groups in binding heavy metals to plant biomass. The studies establish S. natans as an effective biosorbent for removing heavy metals from wastewater and further emphasize biomass utilization in wastewater treatment technologies.

Combined effects of Cu, Cd, Pb, and Zn on the growth and uptake of consortium of Cu-resistant Penicillium sp. A1 and Cd-resistant Fusarium sp. A19

Microorganisms can be important biosorbents for heavy metal remediation of contaminated soils and wastewaters. With different types and concentrations of heavy metals, strains display different resistance and removal abilities to the heavy metals. The objective of this study was to investigate the effects of single and multiple heavy metals on the growth and uptake of consortium of two types of fungal strains, Penicillium sp. A1 and Fusarium sp. A19. These fungal strains were tested to be tolerant to several heavy metals. A1, A19, and their combination (A1+A19) were inoculated on potato dextrose agar (PDA), Czapek Dox agar (CDA), and potato dextrose broth (PDB) containing Cu(2+), Cd(2+), Pb(2+), and Zn(2+). Experimental results showed that the combined inoculation of A1 and A19 had profound effects on the growth of the two fungi in PDA and CDA under the treatments with Cu(2+) and mixed Cd(2+)+Zn(2+). The amount of metals through bioaccumulation by A1, A19, and A1+A19 was significantly higher than that through biosorption by these fungi. The highest amount of Cd, Cu, and Zn accumulated by fungal biomass was obtained in the presence of Cd(2+)+Cu(2+)+Zn(2+) in PDB. Compared with the individual A1 or A19 used in PDB, A1+A19 accumulated higher amount of Cu and Pb in the presence of Cd(2+)+Cu(2+)+Pb(2+) and higher amount of Pb in the presence of Cd(2+)+Cu(2+)+Zn(2+)+Pb(2+). Our results indicated that there was no simple relationship between the metal biosorption by fungal biomass and the fungal metal tolerance. The biomass of A1+A19 cultivated in PDB absorbed higher amount of metals than A1 or A19 in the presence of single metals and their combinations. The results suggested that the applicability of growing fungi tolerant to heavy metals provided a potential biotechnology for treatment of wastewaters with heavy metal pollutions.

Application of orange peel xanthate for the adsorption of Pb2+ from aqueous solutions

Pristine orange peel was chemically modified by introducing sulfur groups with the carbon disulfide treatment in alkaline medium. The presence of sulfur groups on orange peel xanthate were identified by FTIR spectroscopic study. Equilibrium isotherms and kinetics were obtained and the effect of various parameters including equilibrium pH, contact time, temperature and initial ion concentration on adsorption of Pb(2+) were studied by batch experiments. The maximum adsorption capacity of orange peel xanthate was 204.50 mg g(-1), which was found to increase by about 150% compared to that of pristine orange peel. The adsorption process can attain equilibrium within 20 min, and kinetics was found to be best-fit pseudo-second-order equation. Temperature has little effect on the adsorption capacity of orange peel xanthate. In addition, the adsorption mechanism was suggested to be complexation.

Biosorption equilibria of binary Cd(II) and Ni(II) systems onto Saccharomyces cerevisiae and Ralstonia eutropha cells: application of response surface methodology

Present study investigated the biosorption of Cd(II) and Ni(II) from aqueous solution onto Saccharomyces cerevisiae and Ralstonia eutropha non-living biomass. Biomass inactivated by heat and pretreated by ethanol was used in determination of optimum conditions. The important process parameters, such as initial solution pH (2-8), initial Ni(II) concentration (11-42 mg/l), initial Cd(II) concentration (11-42 mg/l), and biomass dosage (0.2-4.7 g/l) were optimized using design of experiments (DOE). A central composite design (CCD) under response surface methodology (RSM) was applied to evaluate and optimize the efficiency of removing each adsorbent. Moreover, the two responses were simultaneously studied by using a numerical optimization methodology. The optimum removal efficiency of Cd(II) and Ni(II) onto S. cerevisiae was determined as 43.4 and 65.5% at 7.1 initial solution pH, 4.07 g/l biomass dosage, 16 mg/l initial Ni(II) concentration and 37 mg/l initial Cd(II) concentration. The optimum removal efficiency of Cd(II) and Ni(II) onto R. eutropha was ascertained as 52.7 and 50.1% at 5.0 initial solution pH, 2.32 g/l biomass dosage, 28 mg/l initial Ni(II) concentration and 37 mg/l initial Cd(II) concentration. The present analysis suggests that the predicted values are in good agreement with experimental data. The characteristics of the possible interactions between biosorbents and metal ions were also evaluated by scanning electron microscope (SEM) and Fourier transform infrared (FT-IR) spectroscopy analysis.

Fast removal of copper ions from aqueous solution by chitosan-g-poly(acrylic acid)/attapulgite composites

Novel chitosan-g-poly(acrylic acid)/attapulgite (CTS-g-PAA/APT) composites were applied as adsorbents for the removal of Cu(II) from aqueous solution. The effects of the initial pH value (pH(0)) of Cu(II) solution, contact time (t), APT content (wt%) and the initial concentration of Cu(II) solution (C(0)) on the adsorption capacity of the composites were investigated. Results from kinetic experimental data showed that the Cu(II) adsorption rate on the composites with 10, 20 and 30 wt% APT was fast and more than 90% of the maximum adsorption capacity for Cu(II) occurred within the initial 15 min. The adsorption kinetics was better described by the pseudo-second order equation, and their adsorption isotherms were better fitted for the Langmuir equation. The results of the five-time consecutive adsorption-desorption studies showed that the composites had high adsorption and desorption efficiencies, which implies that the composites may be used as quite effective adsorbents for the removal of Cu(II) from aqueous solution.

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.

Sorption of paraquat and 2,4-D by an Oscillatoria sp.-dominated cyanobacterial mat

The present study characterises sorption of two pesticides, namely, paraquat (PQ) and 2,4-dichlorophenoxyacetic acid (2,4-D) by an Oscillatoria sp.-dominated cyanobacterial mat. Sorption of PQ onto the test mat was not significantly affected by the pH of the solution within the pH range 2-7. However, 2,4-D sorption was strongly influenced by the solution pH and was maximum at pH 2. Whereas PQ sorption increased with increase in temperature, 2,4-D sorption showed an opposite trend. The sorption of PQ and 2,4-D achieved equilibrium within 1 h of incubation, independent of concentration of pesticide and mat biomass in the solution. The pseudo-second-order kinetic model better defined PQ sorption than the pseudo-first-order model, whereas 2,4-D sorption was well defined by both the models. Sorption isotherms of both the pesticides showed L-type curve. Freundlich model more precisely defined PQ sorption than Langmuir model, thereby suggesting heterogeneous distribution of PQ binding sites onto the biomass surface. However, the Langmuir model more correctly defined 2,4-D sorption, thus, indicating homogeneous distribution of 2,4-D binding sites onto the biomass surface. The test biomass is a good sorbent for the removal of PQ because it could, independent of pH of the solution, sorb substantial amount of PQ (q(max) = 0.13 mmol g(-1)).

Chromium removal from a real tanning effluent by autochthonous and allochthonous fungi

Heavy metals represent an important ecological and health hazard due to their toxic effects and their accumulation throughout the food chain. Conventional techniques commonly applied to recover chromium from tanning wastewaters have several disadvantages whereas biosorption has good metal removal performance from large volume of effluents. To date most studies about chromium biosorption have been performed on simulated effluents bypassing the problems due to organic or inorganic ligands present in real industrial wastewaters that may sequestrate the Cr(III) ions. In the present study a tanning effluent was characterized from a mycological point of view and different fungal biomasses were tested for the removal of Cr(III) from the same tanning effluent in which, after the conventional treatments, Cr(III) amount was very low but not enough to guarantee the good quality of the receptor water river. The experiments gave rise to promising results with a percentage of removed Cr(III) up to 40%. Moreover, to elucidate the mechanisms involved in biosorption process, the same biomasses were tested for Cr(III) removal from synthetic aqueous solutions at different Cr(III) concentrations.

Application of low-cost adsorbents for dye removal--a review

Dyes are an important class of pollutants, and can even be identified by the human eye. Disposal of dyes in precious water resources must be avoided, however, and for that various treatment technologies are in use. Among various methods adsorption occupies a prominent place in dye removal. The growing demand for efficient and low-cost treatment methods and the importance of adsorption has given rise to low-cost alternative adsorbents (LCAs). This review highlights and provides an overview of these LCAs comprising natural, industrial as well as synthetic materials/wastes and their application for dyes removal. In addition, various other methods used for dye removal from water and wastewater are also complied in brief. From a comprehensive literature review, it was found that some LCAs, in addition to having wide availability, have fast kinetics and appreciable adsorption capacities too. Advantages and disadvantages of adsorbents, favourable conditions for particular adsorbate-adsorbent systems, and adsorption capacities of various low-cost adsorbents and commercial activated carbons as available in the literature are presented. Conclusions have been drawn from the literature reviewed, and suggestions for future research are proposed.

Enhanced biosorption of nickel(II) ions by silica-gel-immobilized waste biomass: biosorption characteristics in batch and dynamic flow mode

Batch and dynamic flow biosorption studies were carried out using the waste biomass entrapped in silica-gel matrix for the removal of nickel(II) ions from synthetic solutions and real wastewater. Batch biosorption conditions were examined with respect to initial pH, S/L ratio, contact time, and initial nickel ion concentration. Zeta potential measurements showed that immobilized biosorbent was negatively charged in the pH range of 3.0-8.0. The immobilized biomass was found to possess relatively high biosorption capacity (98.01 mg g(-1)), and biosorption equilibrium was established in a short time of operation (5 min). The equilibrium data were followed by Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models. Scanning electron microscope analysis was used to screen the changes on the surface structure of the waste biomass after immobilization and nickel(II) biosorption. Sorbent-sorbate interactions were confirmed by Fourier transform infrared spectroscopy. The applicability of sorbent system was investigated in a continuous mode, and column studies were performed under different flow rate, column size, and biosorbent dosage. Also, the proposed sorbent system was successfully used to remove the nickel ions from industrial wastewater in dynamic flow treatment mode. The results showed that silica-immobilized waste biomass was a low-cost promising sorbent for sequester of nickel(II) ions from synthetic and real wastewater.

Biosorbents for heavy metals removal and their future

A vast array of biological materials, especially bacteria, algae, yeasts and fungi have received increasing attention for heavy metal removal and recovery due to their good performance, low cost and large available quantities. The biosorbent, unlike mono functional ion exchange resins, contains variety of functional sites including carboxyl, imidazole, sulphydryl, amino, phosphate, sulfate, thioether, phenol, carbonyl, amide and hydroxyl moieties. Biosorbents are cheaper, more effective alternatives for the removal of metallic elements, especially heavy metals from aqueous solution. In this paper, based on the literatures and our research results, the biosorbents widely used for heavy metal removal were reviewed, mainly focusing on their cellular structure, biosorption performance, their pretreatment, modification, regeneration/reuse, modeling of biosorption (isotherm and kinetic models), the development of novel biosorbents, their evaluation, potential application and future. The pretreatment and modification of biosorbents aiming to improve their sorption capacity was introduced and evaluated. Molecular biotechnology is a potent tool to elucidate the mechanisms at molecular level, and to construct engineered organisms with higher biosorption capacity and selectivity for the objective metal ions. The potential application of biosorption and biosorbents was discussed. Although the biosorption application is facing the great challenge, there are two trends for the development of the biosorption process for metal removal. One trend is to use hybrid technology for pollutants removal, especially using living cells. Another trend is to develop the commercial biosorbents using immobilization technology, and to improve the biosorption process including regeneration/reuse, making the biosorbents just like a kind of ion exchange resin, as well as to exploit the market with great endeavor.

Fluorescence as a potential monitoring tool for recycled water systems: a review

A rapid, highly sensitive and selective detector is urgently required to detect contamination events in recycled water systems - for example, cross-connection events in dual reticulation pipes that recycle advanced treated sewage effluent - as existing technologies, including total organic carbon and conductivity monitoring, cannot always provide the sensitivity required. Fluorescence spectroscopy has been suggested as a potential monitoring tool given its high sensitivity and selectivity. A review of recent literature demonstrates that by monitoring the fluorescence of dissolved organic matter (DOM), the ratios of humic-like (Peak C) and protein-like (Peak T) fluorescence peaks can be used to identify trace sewage contamination in river waters and estuaries, a situation analogous to contamination detection in recycled water systems. Additionally, strong correlations have been shown between Peak T and biochemical oxygen demand (BOD) in rivers, which is indicative of water impacted by microbial activity and therefore of sewage impacted systems. Hence, this review concludes that the sensitive detection of contamination events in recycled water systems may be achieved by monitoring Peak T and/or Peak C fluorescence. However, in such systems, effluent is treated to a high standard resulting in much lower DOM concentrations and the impact of these advanced treatment processes on Peaks T and C fluorescence is largely unknown and requires investigation. This review has highlighted that further work is also required to determine (a) the stability and distinctiveness of recycled water fluorescence in relation to the treatment processes utilised, (b) the impact of matrix effects, particularly the impact of oxidation, (c) calibration issues for online monitoring, and (d) the advanced data analytical techniques required, if any, to improve detection of contamination events.

Cadmium tolerance and adsorption by the marine brown alga Fucus vesiculosus from the Irish Sea and the Bothnian Sea

Cadmium (Cd) uptake capacities and Cd tolerance of the marine alga Fucus vesiculosus from the Irish Sea (salinity 35 psu) and from the Bothnian Sea (northern Baltic, 5 psu) were quantified. These data were complemented by measurements of changes in maximal photosynthetic rate (P(max)), dark respiration rate and variable fluorescence vs. maximal fluorescence (F(v):F(m)). At concentrations between 0.01 and 1 mmol Cd l(-1), F. vesiculosus from the Bothnian Sea adsorbed significantly more (about 98%) Cd compared with F. vesiculosus from the Irish Sea. The photosynthetic measurements showed that the Bothnian Sea F. vesiculosus were more sensitive to Cd exposure than the Irish Sea algae. The algae from the Irish Sea showed negative photosynthetic effects only at 1 mmol Cd l(-1), which was expressed as a decreased P(max) (-12.3%) and F(v):F(m) (-4.6%). On the contrary, the algae from the Bothnian Sea were negatively affected already at Cd concentrations as low at 0.1 mmol Cd l(-1). They exhibited increased dark respiration (+11.1%) and decreased F(v):F(m) (-13.9%). The results show that F. vesiculosus from the Bothnian Sea may be an efficient sorption substrate for Cd removal from Cd contaminated seawater and this algae type may also have applications for wastewater treatment.

Modeling the effect of pH on kinetics of heavy metal ion biosorption. A theoretical approach based on the statistical rate theory

The effect of pH is studied on the equilibrium and kinetics of heavy metal biosorption. A concept of an effective surface capacity is introduced to describe the equilibrium isotherms of metal ion adsorption. That effective surface capacity is controlled by adsorption of protons. The obtained simple theoretical expressions appear to be very efficient in correlating equilibrium isotherms of adsorption of two kinds of heavy metal ions on two kinds of biosorbents. Next, the statistical rate theory is applied to develop the related expressions for adsorption kinetics. These expressions appear to be very efficient in correlating kinetic isotherms measured at various pH values.

Treatment of chromium(VI) solutions in a pilot-scale bioreactor through a biofilm of Arthrobacter viscosus supported on GAC

The aim of this work is to evaluate the applicability of a biofilm to the removal of chromium in solution, at a pilot scale. The effect of the initial concentration of metal on the biosorption behavior of an Arthrobacter viscosus biofilm supported on granular activated carbon, in batch and column essays was also analyzed. Six isotherm equations have been tested in the present study. The best fit was obtained with the Freundlich model. It was observed that as the initial chromium concentration increases, the uptake increases too, but the removal percentage decreases, with values between 95.20% (C(0)=5mg/l) and 38.28% (C(0)=1000 mg/l). The batch adsorption studies were used to develop a pilot bioreactor able to remove chromium from aqueous solutions. Data obtained in a pilot-scale reactor showed an average removal percentage of 99.9%, during the first 30 days, for the initial concentration of 10mg/l and an average removal percentage of 72%, for the same period and for the initial concentration of 100mg/l. Uptake values of 11.35 mg/g and 14.55 mg/g were obtained, respectively, for the initial concentration of 10 and 100mg/l. The results obtained are very promising and encourage the utilization of this biofilm in environmental applications.

Isolation of Cr(VI) reducing bacteria from industrial effluents and their potential use in bioremediation of chromium containing wastewater

The present study was aimed to assess the ability of Bacillus sp. JDM-2-1 and Staphylococcus capitis to reduce hexavalent chromium into its trivalent form. Bacillus sp. JDM-2-1 could tolerate Cr(VI) (4800 microg/mL) and S. capitis could tolerate Cr(VI) (2800 microg/mL). Both organisms were able to resist Cd2+ (50 microg/mL), Cu2+ (200 microg/mL), Pb2+ (800 microg/mL), Hg2+ (50 microg/mL) and Ni2+ (4000 microg/mL). S. capitis resisted Zn2+ at 700 microg/mL while Bacillus sp. JDM-2-1 only showed resistance up to 50 microg/mL. Bacillus sp. JDM-2-1 and S. capitis showed optimum growth at pH 6 and 7, respectively, while both bacteria showed optimum growth at 37 degrees C. Bacillus sp. JDM-2-1 and S. capitis could reduce 85% and 81% of hexavalent chromium from the medium after 96 h and were also capable of reducing hexavalent chromium 86% and 89%, respectively, from the industrial effluents after 144 h. Cell free extracts of Bacillus sp. JDM-2-1 and S. capitis showed reduction of 83% and 70% at concentration of 10 microg Cr(VI)/mL, respectively. The presence of an induced protein having molecular weight around 25 kDa in the presence of chromium points out a possible role of this protein in chromium reduction. The bacterial isolates can be exploited for the bioremediation of hexavalent chromium containing wastes, since they seem to have a potential to reduce the toxic hexavalent form to its nontoxic trivalent form.

Enhancement of bioremediation by Ralstonia sp. HM-1 in sediment polluted by Cd and Zn

In this study, the potential for the application of the bioaugmentation to Cd and Zn contaminated sediment was investigated. A batch experiment was performed in the lake sediments augmented with Ralstonia sp. HM-1. The degradation capacity of 18.7 mg-DOC/l/day in the treatment group was bigger than that of the blank group (4.4 mg-DOC/l/day). It can be regarded as the result of the reduction of the metal concentration in the liquid phase due to adsorption into the sediments, with the increased alkalinity resulting from the reduction of sulfate by sulfate reducing bacteria (SRB). The removal efficiency of cadmium and zinc in the treatment group was both 99.7% after 35 days. Restrain of elution to water phase from sediment in the Ralstonia sp. HM-1 added treatment group was also shown. In particular, the observed reduction of the exchangeable fraction and an increase in the bound to organics or sulfide fraction in the treatment group indicate its role in the prevention of metal elution from the sediment. Therefore, for bioremediation and restrain of elution from the sediment polluted by metal, Ralstonia sp. augmentation with indigenous microorganism including SRB, sediment stabilization and restrain of elution to surface water is recommended.

Cadmium removal from simulated wastewater to biomass byproduct of Lentinus edodes

A kind of agricultural waste, the byproduct of brown-rot fungus Lentinus edodes, was used as an efficient biosorbent for the removal of cadmium from water in this paper. The sorption conditions, such as pH, the dose of biomass and the initial concentration of cadmium were examined. Three kinds of adsorption models were applied to simulate the biosorption data. Uptake of cadmium was higher in weak acid condition than in strong acid condition. Nearly no sorption of cadmium occurred when the pH value was lower than 2.5. Biosorption isothermal data could be well simulated by Freundlich model, and then Langmuir and Temkin model. Langmuir simulation of the biosorption showed that the maximum uptake of cadmium was 5.58mmol/g in weak acid condition, which was much higher than many other biosorbents. The exchanged proton was highly related to the uptake of cadmium in weak acid condition. Fourier transform infrared spectrums and energy-dispersive X-ray microanalyzer were used to reveal ion-exchange mechanism between cadmium and the functional groups or participated inorganic metal ions during biosorption.

A comparative study of alginate beads and an ion-exchange resin for the removal of heavy metals from a metal plating effluent

The capacity of dry protonated calcium alginate beads to sorb metals from an industrial effluent was studied and compared with a commercial ion-exchange resin (Lewatit TP 207). Both sorbents decreased zinc, nickel, iron and calcium concentrations in the effluent, and released sodium during treatment. Alginate beads removed lower amounts of heavy metals than the resin, but exhibited faster uptake kinetics. Zinc desorption from the sorbents was achieved in 30 minutes using 0.1 M HCl or 0.1 M H(2)SO(4). Desorption ratios with these acids varied between 90 and 100% for alginate, and 98 to 100% for the ion-exchange resin. Reusability tests with HCl showed that alginate beads can stand acid desorption and recover binding capacity. Overall, the comparison of dry protonated alginate beads with the resin supports the potential of the biosorbent for the treatment of industrial effluents.

Cadmium, zinc and copper biosorption mediated by Pseudomonas veronii 2E

Adsorption properties of bacterial biomass were tested for Cd removal from liquid effluents. Experimental conditions (pH, time, cellular mass, volume, metal concentration) were studied to develop an efficient biosorption process with free or immobilised cells of Pseudomonas veronii 2E. Surface fixation was chosen to immobilise cells on inert surfaces including teflon membranes, silicone rubber and polyurethane foam. Biosorption experiments were carried out at 32 degrees C and controlled pH; maximal Cd(II) retention was observed at pH 7.5. The isotherm followed the Langmuir model (K(d)=0.17 mM and q(max)=0.48 mmol/g cell dry weight). Small changes in the surface negative charge of cells were observed by electrophoretic mobility experiments in presence of Cd(II). In addition, biosorption of 40% Cu(II) (pH 5 and 6.2) and 50% Zn(II) and 50% Cd(II) (pH 7.5) was observed from mixtures of Cu(II), Zn(II) and Cd(II) 0.5mM each.

Fourier Transform Infrared Spectroscopic characterization and optimization of Pb(II) biosorption by fish (Labeo rohita) scales

The present study reports the use of locally available fish (Labeo rohita) scales for Pb(II) removal from aqueous solutions under different experimental conditions. Maximum Pb(II) adsorption (196.8 mg g(-1)) occurred at pH 3.5. Pb(II) sorption was found to be pH, dose, initial metal concentration, contact time and shaking speed dependent while particle size and temperature independent. Experimental data of Pb(II) biosorption onto fish scales fitted well to Freundlich isotherm model in comparison to the model of Langmuir. The fast adsorption process in first 30 min followed by subsequent slow adsorption rate was suitably described by pseudo-second order model. In addition, this study was designed to evaluate the effect of physical and chemical pretreatments on surface properties of fish scales by the application of Fourier Transform Infrared (FTIR) Spectroscopic analysis. Physical pretreatments resulted in partial degradation of some functional groups. Alkaline pretreatments of fish scales did not have any significant influence on the nature of functional groups responsible for Pb(II) uptake, while acidic pretreatments resulted in degeneration of the most of functional groups on biosorbent cell wall. FTIR analysis confirmed the involvement of amino, carboxylic, phosphate and carbonyl groups in Pb(II) biosorption by fish scales.

Chromium tolerance and reduction potential of a Bacillus sp.ev3 isolated from metal contaminated wastewater

This study was aimed at assessing the ability of Bacillus sp.ev3 to reduce hexavalent chromium into its trivalent form. Bacillus sp.ev3 could tolerate Cr(6+) (4800 microg/mL), Pb(2+) (800 microg/mL), Cu(2+) (200 microg/mL), Cd(2+) (50 microg/mL), Zn(2+) (400 microg/mL), Ni(2+) (4000 microg/mL) and Hg(2+) (50 microg/mL). Bacillus sp.ev3 showed optimum growth at 37 degrees C and pH at 7. Bacillus sp.ev3 could reduce 91% of chromium from the medium after 96 h and was also capable to reduce 84% chromium from the industrial effluents after 144 h. Cell free extracts of Bacillus sp.ev3 grown in the presence of Cr showed reduction of 70%, 45.6% and 27.4% at concentrations of 10 microg Cr(6+)/mL, 50 microg Cr(6+)/mL and 100 microg Cr(6+)/mL, respectively.

A new chlorophycean nickel hyperaccumulator

Bioremediation of nickel by chlorophycean bioremediator, Chlorococcum hemicolum was investigated. The growth rates at various concentrations of Ni2+ were assessed in terms of protein level and 12 mg L(-1) of the Ni2+ is the tolerance limit (46.76% level of growth kinetics). Absorption/adsorption kinetics was estimated after 240 h of Ni2+ treatments. Absorptions were higher than adsorption with maximum accumulation factor (AF) of 1.37. Ni2+ concentration and absorption were linearly related (r=0.98; p>0.01). Other biochemical parameters like total sugar, chlorophyll and carotenoids were also quantified to correlate the state of metabolism and these exhibited reduction due to heavy metal stress.

New biosorbent materials for heavy metal removal: product development guided by active site characterization

Olive pomace wastes were used as precursors for the development of new biosorbents for heavy metals. Thermal and/or chemical treatments were addressed in terms of their effects on functional group properties and copper removal. Product development was guided by experimental characterization (potentiometric titrations, IR spectra, copper biosorption, total surface area) and theoretical modeling of acid-base properties. Olive pomace was characterized by negative charge due to dissociation of two weakly acidic sites (carboxylic and phenolic). After thermal treatment, a char-like material was obtained, characterized by basic sites with positive charge in the acidic pH range. Copper biosorption properties of this material were improved with respect to olive pomace due to the binding ability of pyrone-like sites. Both native and carbonized olive pomace samples were chemically treated by HNO(3). Experimental tests were performed according to factorial designs and analysis of variance was used to evaluate significant effects on copper removal of both oxidant concentration and temperature. Chemical treatment by HNO(3) of carbonized material developed negatively charged groups in the acidic pH range (carboxylic groups), but presented a decreased copper removal. Chemical treatment by HNO(3) of olive pomace without carbonization gave biosorbents with acid-base properties similar to those of native olive pomace, but with a significant increase of copper biosorption. Specific carboxylic-copper interactions indicated by IR spectra and increased surface area due to chemical treatment were simultaneously responsible for such improvement.

Batch and column studies of biosorption of heavy metals by Caulerpa lentillifera

The biosorption of Cu(II), Cd(II), and Pb(II) by a dried green macroalga Caulerpa lentillifera was investigated. The sorption kinetic data could be fitted to the pseudo second order kinetic model. The governing transport mechanisms in the sorption process were both external mass transfer and intra-particle diffusion. Isotherm data followed the Sips isotherm model with the exponent of approximately unity suggesting that these biosorption could be described reasonably well with the Langmuir isotherm. The maximum sorption capacities of the various metal components on C. lentillifera biomass could be prioritized in order from high to low as: Pb(II)>Cu(II)>Cd(II). The sorption energies obtained from the Dubinin-Radushkevich model for all sorption systems were in the range of 4-6 kJ mol(-1) indicating that a physical electrostatic force was potentially involved in the sorption process. Thomas model could well describe the breakthrough data from column experiments. Ca(II), Mg(II), and Mn(II) were the major ions released from the algal biomass during the sorption which revealed that ion exchange was one of the main sorption mechanisms.

Biosorption of Cr(VI) by three different bacterial species supported on granular activated carbon: a comparative study

The ability of three different bacterial species supported on granular activated carbon (GAC) to remove hexavalent chromium from low concentration liquid solutions was investigated, in batch and column studies. The microorganisms tested were Cr(VI) reducing types: Streptococcus equisimilis (CECT 926), Bacillus coagulans (CECT 12) and Escherichia coli (CECT 515). The results showed metal uptake values of 5.82, 5.35 and 4.12 mg/g(bios.), respectively, for S. equisimilis, B. coagulans and E. coli, for an initial metal concentration of 100 mg/l. In the same order and for the initial concentration of 50 mg/l, metal uptake values were 2.33, 1.98 and 3.60 mg/g(bios.). Finally, for the initial metal concentration of 10 mg/l, those values were, respectively, 0.66, 1.51 and 1.12 mg/g(bios.). Studies made with an industrial effluent, with the aim of testing these biofilms in a real situation, showed values of Cr uptake of 0.083, 0.090 and 0.110 mg/g(bios.), respectively, for S. equisimilis, B. coagulans and E. coli, for an initial concentration of 4.2 mg/l of total Cr. The quantification of polysaccharides, playing a key role in the whole process, was made and it was concluded that the production of polysaccharides is higher for B. coagulans followed by S. equisimilis and E. coli (9.19, 7.24 and 4.77 mg/g(bios.)). The batch studies data were described using the Freundlich, Langmuir, Redlich-Peterson, Dubinin-Radushkevich, Sips and Toth model isotherms. The best fit was obtained with Sips and Toth model isotherms, respectively, for the S. equisimilis and for the B. coagulans biofilms. For the E. coli biofilm the Freundlich, Redlich-Peterson, Sips and Toth models fitted very well to the experimental data. The Adams-Bohart, Wolborska and Yoon and Nelson models were applied to column studies data. Those models were found suitable for describing the dynamic behaviour of the columns with respect to the inlet chromium concentration. Obtained results showed that the biofilms tested are very promising for the removal of Cr(VI) in diluted industrial wastewater. Despite differences in the cell wall structure and composition, the three bacteria exhibit comparable sorption affinities towards chromium, in the open systems studies. The Gram-positive bacteria tested (B. coagulans and S. equisimilis) presented best metal removal percentages in batch studies.