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

Effects of Cesium on Physiological Traits of the Catherine's Moss Atrichum undulatum Hedw

Mosses are proven bioindicators of living environments. It is known that mosses accumulate pollutants from precipitates and, to some lesser extent, from the substrate. In this study, the effects of cesium (Cs) on the physiological traits of acrocarp polytrichaceous Catherine's moss (Atrichum undulatum Hedw.) were studied under controlled, in vitro conditions. Cesium can be found in the environment in a stable form (133Cs) and as a radioactive isotope (134Cs and 137Cs). Belonging to the same group of elements, Cs and potassium (K) share various similarities, due to which Cs can interfere with this essential element and thus possibly alter the plant's metabolism. Results have shown that Cs affects the measured physiological characteristics of A. undulatum, although the changes to antioxidative enzyme activities were not drastic following Cs treatments. Therefore, the activities of antioxidative enzymes at lower pH values are more the consequence of pH effects on enzymatic conformation than simply the harmful effects of Cs. Moreover, Cs did not affect the survival of plants grown on the solid substrate nor plants grown in conditions of light and heavy rain simulation using Cs with variable pH, indicating that Cs is not harmful in this form for the studied species A. undulatum.

Nanostructure of humic acid adsorption layer in the presence of Cs and Sr ions on the surface of waste material obtained from residue after supercritical extraction of hops

Adsorption of ionic molecules at the solid–liquid interface depends on various interactions, particles surface properties as well as the presence of the additional substance in the analyzed systems. The waste material obtained from the supercritical fluid extraction process was used as an adsorbent. The plant-based biosorbent structure was fully characterized. Then the humic acid (constituting the common interfering substance found in the environmental samples) sorption on the hop cones was investigated in the absence and presence of Sr/Cs ions under various pH conditions. Hence, the metal cation valence can influence the interactions between the colloidal system constituents and the adsorption layer structure. Determining the mutual interactions in the complex systems is important due to the potential possibility of using the waste sorbent to remove the radioactive Cs and Sr isotopes from the aquatic environment. Due to the lack of a porous structure of the sorbent and the high surface density of the charge, the metal ions are bound directly on the particles surface. The humic acid (HA) adsorption is greatly pH dependent—the largest removal was achieved under the acidic conditions (Qads = 88.69 mg/g), while the HA sorption process at pH 9 is impeded by a large negative charge deposited at the solid–liquid interface (Qads = 7.06 mg/g). At pH 3, formation of multilayer adsorption structure contributes to the effective removal of organic impurities. The metal ions valence significantly affects the humic acid binding mechanism. Divalent Sr acts like a “bridge” increasing the number of biosorbent active sites (at pH = 3 the HA adsorption increases almost twofold from 88.69 to 156.46 mg/g in the Sr ions), whereas the Cs+ ions leads to the reduction in the HA removal efficiency (Qads. = 46.31 mg/g under the same conditions).

Application of duckweed (Lemna sp.) and water fern (Azolla sp.) in the removal of pharmaceutical residues in water: State of art focus on antibiotics

In recent decades, antibiotic residues in the environment have increased, affecting components of biological communities, from bacteria to plants and animals. Different methods have been used to remove these compounds, including phytoremediation with floating aquatic species such as duckweed and aquatic fern, with positive results. This study analyses information about the removal efficiency of drugs, with a focus on antibiotics, using Lemna and Azolla, which will allow a better understanding of phytoremediation processes from the perspective of plant physiology. The physiological processes of macrophytes in an environment with this type of pollutant and the phytotoxic effects on plants at high concentrations are also analysed. The metabolization of toxic compounds occurs in three phases: phase I begins with the absorption of antibiotics and the secretion of reactive oxygen species (ROS); in phase II, the effects of ROS are neutralized and minimized by conjugation with enzymes such as glutathione transferase or metabolites such as glutathione; and phase III culminates with the storage of the assimilated compounds in the vacuoles, apoplast and cell wall. In this way, plants contribute to the removal of toxic compounds. In summary, there is sufficient scientific evidence on the efficiency of the elimination of pharmaceutical compounds by these floating macrophytes at the laboratory scale, which indicates that their application under real conditions can have good results.

Biosorption of uranium from aqueous solutions by Azolla sp. and Limnobium laevigatum

The main goal of this study was to assess alternatives to the current challenges on environmental quality and circular economy. The former is here addressed by the treatment of radioactively contaminated solutions, and the latter by using abundant and low-cost biomass. In this paper, we examine the biosorption of hexavalent uranium (U(VI)) in a batch system using the macrophytes Limnobium laevigatum and Azolla sp. by three operational parameters: biomass dose, metal ion concentration, and contact time. Simulated solutions were firstly addressed with two biomasses, followed by studies with real liquid organic radioactive waste (LORW) with Azolla sp. The batch experiments were carried out by mixing 0.20 g biomass in 10 mL of the prepared solution or LORW. The total contact time employed for the determination of the equilibrium times was 240 min, and the initial U(VI) concentration was 0.63 mmol L^-1. The equilibrium times were 15 min for L. laevigatum and 30 min for Azolla sp. respectively. A wide range of initial U(VI) concentrations (0.25-36 mmol L^-1) was then used to assess the adsorption capacity of each macrophyte. Isotherm models validated the adsorption performance of the biosorption process. Azolla sp. presented a much higher U(VI) uptake (0.474 mmol g^-1) compared to L. laevigatum (0.026 mmol g^-1). When in contact with LORW, Azolla sp. removed much less uranium, indicating an adsorption capacity of 0.010 mmol g^-1. In conclusion, both biomasses, especially Azolla sp., can be used in the treatment of uranium-contaminated solutions.

Metal Detoxification in Land Plants: From Bryophytes to Vascular Plants. STATE of the Art and Opportunities

Potentially toxic elements are a widespread concern due to their increasing diffusion into the environment. To counteract this problem, the relationship between plants and metal(loid)s has been investigated in the last 30 years. In this field, research has mainly dealt with angiosperms, whereas plant clades that are lower in the evolutive scale have been somewhat overlooked. However, recent studies have revealed the potential of bryophytes, pteridophytes and gymnosperms in environmental sciences, either as suitable indicators of habitat health and elemental pollution or as efficient tools for the reclamation of degraded soils and waters. In this review, we summarize recent research on the interaction between plants and potentially toxic elements, considering all land plant clades. The focus is on plant applicability in the identification and restoration of polluted environments, as well as on the characterization of molecular mechanisms with a potential outlet in the engineering of element tolerance and accumulation.

Efficacious bioremediation of heavy metals and radionuclides from wastewater employing aquatic macro- and microphytes

Cytotoxic, mutagenic, and carcinogenic contaminants, such as heavy metals and radionuclides, have become an alarming environmental concern globally, especially for developed and developing nations. Moreover, inefficient prevalent wastewater treatment technologies combined with increased industrial activity and modernization has led to increase in the concentration of toxic metals and radioactive components in the natural water bodies. However, for the improvement of ecosystem of rivers, lakes, and other water sources different physicochemical methods such as membrane filtration, reverse osmosis, activated carbon adsorption, electrocoagulation, and other electrochemical treatment are employed, which are uneconomical and insufficient for the complete abatement of these emerging pollutants. Therefore, the application of bioremediation employing aquatic macrophytes and microphytes have gained considerable importance owing to the benefits of cost-effectiveness, eco-friendly, and higher energy efficiency. Thus, the present review aims to enlighten the readers on the potential application of algae, cyanobacteria, plant, and other aquatic micro- and macrophytes for the elimination of carcinogenic metals and radioactive isotopes from wastewater. Additionally, the use of transgenic plants, genetically modified species, algal-bacterial symbiosis for the enhancement of removal efficiency of mutagenic contaminants are also highlighted. Furthermore, species selection based on robustness, mechanism of different pathways for heavy metal and radionuclide detoxification are elucidated in this review article.

Structural Investigation on the Efficient Capture of Cs+ and Sr2+ by a Microporous Cd-Sn-Se Ion Exchanger Constructed from Mono-Lacunary Supertetrahedral Clusters

Visualization of the ion exchange mechanism for 137Cs and 90Sr decontamination bears significance for safe radioactive liquid waste reprocessing and emergency response enhancement to nuclear accident. Here, the remediation of...

Identification of a Stable Hydrogen-Driven Microbiome in a Highly Radioactive Storage Facility on the Sellafield Site

The use of nuclear power has been a significant part of the United Kingdom’s energy portfolio with the Sellafield site being used for power production and more recently reprocessing and decommissioning of spent nuclear fuel activities. Before being reprocessed, spent nuclear fuel is stored in water ponds with significant levels of background radioactivity and in high alkalinity (to minimize fuel corrosion). Despite these challenging conditions, the presence of microbial communities has been detected. To gain further insight into the microbial communities present in extreme environments, an indoor, hyper-alkaline, oligotrophic, and radioactive spent fuel storage pond (INP) located on the Sellafield site was analyzed. Water samples were collected from sample points within the INP complex, and also the purge water feeding tank (FT) that supplies water to the pond, and were screened for the presence of the 16S and 18S rRNA genes to inform sequencing requirements over a period of 30 months. Only 16S rRNA genes were successfully amplified for sequencing, suggesting that the microbial communities in the INP were dominated by prokaryotes. Quantitative Polymerase Chain Reaction (qPCR) analysis targeting 16S rRNA genes suggested that bacterial cells in the order of 10⁴–10⁶ mL^–1 were present in the samples, with loadings rising with time. Next generation Illumina MiSeq sequencing was performed to identify the dominant microorganisms at eight sampling times. The 16S rRNA gene sequence analysis suggested that 70% and 91% from of the OTUs samples, from the FT and INP respectively, belonged to the phylum Proteobacteria, mainly from the alpha and beta subclasses. The remaining OTUs were assigned primarily to the phyla Acidobacteria, Bacteroidetes, and, Cyanobacteria. Overall the most abundant genera identified were Hydrogenophaga, Curvibacter, Porphyrobacter, Rhodoferax, Polaromonas, Sediminibacterium, Roseococcus, and Sphingomonas. The presence of organisms most closely related to Hydrogenophaga species in the INP areas, suggests the metabolism of hydrogen as an energy source, most likely linked to hydrolysis of water caused by the stored fuel. Isolation of axenic cultures using a range of minimal and rich media was also attempted, but only relatively minor components (from the phylum Bacteroidetes) of the pond water communities were obtained, emphasizing the importance of DNA-based, not culture-dependent techniques, for assessing the microbiome of nuclear facilities.

Combined use of tannic acid-type organic composite adsorbents and ozone for simultaneous removal of various kinds of radionuclides in river water

Tannic acid-type organic composite adsorbents (PA316TAS, AR-01TAS, PYRTAS, WA10TAS, WA20TAS, and WA30TAS), combined with hydrolyzed and sulfonated tannic acid (TAS) and porous-type strongly basic anion-exchange resin (PA316), benzimidazole-type anion-exchange resin embedded in high-porous silica beads (AR-01), pyridine-type anion-exchange resin (PYR), acrylic-type weakly basic anion-exchange resin (WA10), or styrene-type weakly basic anion-exchange resins (WA20 and WA30) for simultaneous removal of various kinds of radionuclides in river water were successfully synthesized. The adsorption behavior of twelve kinds of simulated radionuclides (Mn, Co, Sr, Y, Ru, Rh, Sb, Te, Cs, Ba, Eu, and I (I^- and IO₃^-)) on these composite adsorbents has been studied in real river water at room temperature. PA316TAS adsorbents showed much higher distribution coefficients (K_d) for all metal ions. TAS structure has more selective adsorption ability for Mn, Co, Sr, Y, Cs, Ba, Eu, and IO₃^-. On the other hand, Y, Ru, Rh, Sb, Te, Eu, I (I^- and IO₃^-) were adsorbed on both PA316 and TAS structures. To evaluate the validity of these mechanistic expectations, the respective chemical adsorption behaviors of Mn, Co, Sr, etc. and PA316TAS adsorbent were examined in river water ranging in temperature from 278 to 333 K. As was expected, one adsorption mechanism for Mn, Co, Sr, Cs, and Ba systems and two types of adsorption mechanisms for Y, Ru, Rh, Sb, Te, Eu, I (I^- and IO₃^-) systems were observed. On the other hand, the precipitation of Mn, Co, Y, Ru, Rh, Te, and Eu was formed by ozonation for river water, that is, ozone can transform Mn, Co, Y, Ru, Rh, Te, and Eu ions into the insoluble precipitates. Hence, one straight line for Sr, Cs, Ba systems and two types of straight lines for Sb, I (I^- and IO₃^-) systems were obtained in river water treated with ozone. The chromatography experiments of Cs, Sr, I (I^- and IO₃^-) were carried out to calculate their maximum adsorption capacities. The obtained maximum adsorption capacities of Cs, Sr, and I^- mixed with IO₃^- were 1.7 × 10^-4 (Cs), 1.8 × 10^-3 (Cs/O₃), 7.8 × 10^-5 (Sr), 5.6 × 10^-4 (Sr/O₃), 5.4 × 10^-2 (I^- and IO₃^-), 3.1 × 10^-2 (I^- and IO₃^-/O₃) mol/g - PA316TAS. It was discovered that the maximum adsorption capacities of I^- and IO₃^- for the composite adsorbent is unprecedented high and the capacity become much greater than an order of magnitude, compared with those of previous reports. This phenomenon suggests the formation of electron-donor-acceptor (EDA) complexes or pseudo EDA complex. Based on these results, it was concluded that the combined use of tannic acid-type organic composite adsorbents and ozone made it possible to remove simultaneously and effectively various kinds of radionuclides in river water in the wide pH and temperature ranges.

Behavior and Mechanism of Cesium Biosorption from Aqueous Solution by Living Synechococcus PCC7002

Many efforts have focused on the adsorption of metals from contaminated water by microbes. Synechococcus PCC7002, a major marine cyanobacteria, is widely applied to remove metals from the ocean's photic zone. However, its ability to adsorb cesium (Cs) nuclides has received little attention. In this study, the biosorption behavior of Cs(I) from ultrapure distilled water by living Synechococcus PCC7002 was investigated based on kinetic and isotherm studies, and the biosorption mechanism was characterized by Fourier-transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectrometry, and three-dimensional excitation emission matrix fluorescence spectroscopy. Synechococcus PCC7002 showed extremely high tolerance to Cs ions and its minimal inhibitory concentration was 8.6 g/L. Extracellular polymeric substances (EPS) in Synechococcus PCC7002 played a vital role in this tolerance. The biosorption of Cs by Synechococcus PCC7002 conformed to a Freundlich-type isotherm model and pseudo-second-order kinetics. The binding of Cs(I) was primarily attributed to the extracellular proteins in EPS, with the amino, hydroxyl, and phosphate groups on the cell walls contributing to Cs adsorption. The biosorption of Cs involved two mechanisms: Passive adsorption on the cell surface at low Cs concentrations and active intracellular adsorption at high Cs concentrations. The results demonstrate that the behavior and mechanism of Cs adsorption by Synechococcus PCC7002 differ based on the Cs ions concentration.

Immobilization of cesium-resistant bacterial cells by radiation polymerization and their bioremoval efficiency

Biological approaches for the removal of heavy metals and radionuclides from contaminated water are reported. The present study was carried out with the objective of identifying bacterial strains for the uptake of cesium that could be used for bioremediation. Polymer carriers prepared by radiation polymerization were used for the immobilization of bacteria and the efficiency of free cells and immobilized cells for the removal of cesium was evaluated. Thirty-five bacterial isolates were screened for resistance to cesium and five bacterial isolates based on resistance to cesium (BR-3, BR-6, BR-21, BR-39, BR-40) were selected for immobilization. Polymer carriers were prepared using 10, 20, 30, 40 and 50% acrylamide at different doses of 1 to 5 kGy gamma radiation. The polymer carriers prepared using 30% and 40% acrylamide at 5 kGy were found to be suitable based on gel fraction and absorption capacity for the immobilization of bacterial cells. Bioremoval of cesium by free and immobilized bacterial cells was evaluated. Significant reductions of 76-81% cesium were observed with bacterial cells immobilized by radiation polymerization.

Potential of higher plants, algae, and cyanobacteria for remediation of radioactively contaminated waters

The potential of photosynthetic organisms to remediate radioactively contaminated water was evaluated for scenarios related to nuclear installations and included the following radionuclides: ¹³⁷Cs, ¹³⁴Cs, ¹³⁶Cs, ⁹⁰Sr, ¹³¹I, ²³⁹Pu, ²⁴¹Am, ¹³²Te/¹³²I, ⁵⁸Co, ⁶⁰Co, ⁵¹Cr, ^110mAg, ⁵⁴Mn, ¹²⁴Sb, ⁵⁹Fe, ⁶⁵Zn, ⁹⁵Zr, and ⁹⁵Nb. An extensive literature review was undertaken leading to the creation of a database including more than 20,000 entries from over 100 references in which terrestrial and aquatic plants, macro- and microalgae, cyanobacteria and biosorbents derived from these organisms were used to clean water from these specific radionuclides or their stable isotopes. In a first phase, the remediation potential of the organisms and biosorbents was evaluated for the individual elements based on parameters such as plant uptake, removal percentage, and bioconcentration factor, and for two radionuclide mixtures based on the ability of the organisms/biosorbents to work under mixture conditions. As the experimental and environmental conditions will influence the performance of the organisms and biosorbents, a literature-based evaluation of the most influencing or restricting parameters was made and water pH, competing ions, and the chemical modification of biosorbents showed to be of major importance. Finally, the most promising organisms and biosorbents were identified using a specifically developed selection procedure taking into account their performance and robustness. Ranking was done based on clear criteria with a distinct weight and scoring scheme. As such, 20 organisms/biosorbents were identified that showed high potential to clean waters contaminated with (mixtures of) radionuclides related to nuclear installations and which can be used for further experimental investigations.

Synergistic interface behavior of strontium adsorption using mixed microorganisms

The proper handling of low-level radioactive waste is crucial to promote the sustainable development of nuclear power. Research into the mechanism for interactions between bacterium and radionuclides is the starting point for achieving successful remediation of radionuclides with microorganisms. Using Sr(II) as a simulation radionuclide and the mixed microorganisms of Saccharomyces cerevisiae and Bacillus subtilis as the biological adsorbent, this study investigates behavior at the interface between Sr(II) and the microorganisms as well as the mechanisms governing that behavior. The results show that the optimal ratio of mixed microorganisms is S. cerevisiae 2.0 g L^-1 to B. subtilis 0.05 g L^-1, and the optimal pH is about 6.3. Sr(II) biosorption onto the mixed microorganisms is spontaneous and endothermic in nature. The kinetics and the equilibrium isotherm data of the biosorption process can be described with pseudo-second-order equation and the Langmuir isotherm equation, respectively. The key interaction between the biological adsorbent and Sr(II) involves shared electronic pairs arising from chemical reactions via bond complexation or electronic exchange, and spectral and energy spectrum analysis show that functional groups (e.g., hydroxyl, carboxyl, amino, amide) at the interface between the radionuclide and the mixed microorganisms are the main active sites of the interface reactions.

Programmed gradient descent biosorption of strontium ions by Saccaromyces cerevisiae and ashing analysis: A decrement solution for nuclide and heavy metal disposal

One of the waste disposal principles is decrement. The programmed gradient descent biosorption of strontium ions by Saccaromyces cerevisiae regarding bioremoval and ashing process for decrement were studied in present research. The results indicated that S. cerevisiae cells showed valid biosorption for strontium ions with greater than 90% bioremoval efficiency for high concentration strontium ions under batch culture conditions. The S. cerevisiae cells bioaccumulated approximately 10% of strontium ions in the cytoplasm besides adsorbing 90% strontium ions on cell wall. The programmed gradient descent biosorption presented good performance with a nearly 100% bioremoval ratio for low concentration strontium ions after 3 cycles. The ashing process resulted in a huge volume and weight reduction ratio as well as enrichment for strontium in the ash. XRD results showed that SrSO4 existed in ash. Simulated experiments proved that sulfate could adjust the precipitation of strontium ions. Finally, we proposed a technological flow process that combined the programmed gradient descent biosorption and ashing, which could yield great decrement and allow the supernatant to meet discharge standard. This technological flow process may be beneficial for nuclides and heavy metal disposal treatment in many fields.

Cobalt separation by Alphaproteobacterium MTB-KTN90: magnetotactic bacteria in bioremediation

Bioremediation of toxic metals by magnetotactic bacteria and magnetic separation of metal-loaded magnetotactic bacteria are of great interest. This bioprocess technique is rapid, efficient, economical, and environmentally friendly. In this study, cobalt removal potential of a novel isolated magnetotactic bacterium (Alphaproteobacterium MTB-KTN90) as a new biosorbent was investigated. The effects of various environmental parameters in the cobalt removal and the technique of magnetic separation of cobalt-loaded bacterial cells were studied. Cobalt removal by MTB-KTN90 was very sensitive to pH solution; higher biosorption capacity was observed around pH 6.5-7.0. When biomass concentration increased from 0.009 to 0.09 g/l, the biosorption efficiency increased from 13.87 % to 19.22 %. The sorption of cobalt by MTB-KTN90 was rapid during the first 15 min (859.17 mg/g dry weight). With the increasing of cobalt concentrations from 1 to 225 mg/l, the specific cobalt uptake increased. Maximum cobalt removal (1160.51 ± 15.42 mg/g dry weight) took place at optimum conditions; pH 7.0 with initial cobalt concentration of 115 mg/l at 60 min by 0.015 g/l of dry biomass. The results showed maximum values for constants of Langmuir and Freundlich models so far. The biosorption mechanisms were studied with FTIR, PIXE, and FESEM analysis. Cobalt-loaded MTB-KTN90 had ability to separate from solution by a simple magnetic separator. Magnetic response in MTB-KTN90 is due to the presence of unique intracellular magnetic nanoparticles (magnetosomes). The orientation magnetic separation results indicated that 88.55 % of cobalt was removed from solution. Consequently, Alphaproteobacterium MTB-KTN90 as a new biosorbent opens up good opportunities for the magnetic removal of cobalt from the polluted aquatic environments.

Bioanalytics in Quantitive (Bio)imaging/Mapping of Metallic Elements in Biological Samples

The aim of this article is to describe selected analytical techniques and their applications in the quantitative mapping/(bio)imaging of metals in biological samples. This work presents the advantages and disadvantages as well as the appropriate methods of scope for research. Distribution of metals in biological samples is currently one of the most important issues in physiology, toxicology, pharmacology, and other disciplines where functional information about the distribution of metals is essential. This issue is a subject of research in (bio)imaging/mapping studies, which use a variety of analytical techniques for the identification and determination of metallic elements. Increased interest in analytical techniques enabling the (bio)imaging of metals in a variety of biological material has been observed more recently. Measuring the distribution of trace metals in tissues after a drug dose or ingestion of poison-containing metals allows for the studying of pathomechanisms and the pathophysiology of various diseases and disorders related to the management of metals in human and animal systems.

Influence of adsorption parameters on cesium uptake from aqueous solutions- a brief review

Due to rapid population growth, technological advancement and industrial revolution, the rate of generated waste effluents has become a grave concern.

Biosorption behavior and mechanism of cesium-137 on Rhodosporidium fluviale strain UA2 isolated from cesium solution

In order to identify a more efficient biosorbent for (137)Cs, we have investigated the biosorption behavior and mechanism of (137)Cs on Rhodosporidium fluviale (R. fluviale) strain UA2, one of the dominant species of a fungal group isolated from a stable cesium solution. We observed that the biosorption of (137)Cs on R. fluviale strain UA2 was a fast and pH-dependent process in the solution composed of R. fluviale strain UA2 (5 g/L) and cesium (1 mg/L). While a Langmuir isotherm equation indicated that the biosorption of (137)Cs was a monolayer adsorption, the biosorption behavior implied that R. fluviale strain UA2 adsorbed cesium ions by electrostatic attraction. The TEM analysis revealed that cesium ions were absorbed into the cytoplasm of R. fluviale strain UA2 across the cell membrane, not merely fixed on the cell surface, which implied that a mechanism of metal uptake contributed largely to the cesium biosorption process. Moreover, PIXE and EPBS analyses showed that ion-exchange was another biosorption mechanism for the cell biosorption of (137)Cs, in which the decreased potassium ions were replaced by cesium ions. All the above results implied that the biosorption of (137)Cs on R. fluviale strain UA2 involved a two-step process. The first step is passive biosorption that cesium ions are adsorbed to cells surface by electrostatic attraction; after that, the second step is active biosorption that cesium ions penetrate the cell membrane and accumulate in the cytoplasm.

Phytodegradation potential of bisphenolA from aqueous solution by Azolla Filiculoides

Many organic hazardous pollutants such as bisphenolA (BPA) which are toxic and not easily biodegradable can concerns for environmental pollution worldwide. The objective of this study was to examine whether Azolla Filiculoides is able to remove BPA from aqueous solutions. In this study, the Azolla with different biomass (0.3, 0.6, 0.9, 1.2 g) has been cultured in solution that was contained 5, 10, 25 and 50 ppm BPA. Samples were collected every 2 days from all of containers. The analytical determination of BPA was performed by using of DR4000 uv-visible at λmax = 276 nm. The results indicated that Azolla has high ability to remove BPA from aqueous solutions. The BPA removal was 60-90%. The removal efficiency is increasing with decreasing of BPA concentration and increasing of biomass amount and vice versa. The removal efficiency was more than 90% when BPA concentration was 5 ppm and amount of biomass was 0.9gr. It is concluded that Azolla able remove BPA by Phytodegradation from the aqueous solutions. Since conventional methods of BPA removal need to high cost and energy, phytoremediation by Azolla as a natural treatment system can decrease those issues and it can be a useful and beneficial method to removal of BPA.

Thin and thick target PIXE analyses to assess the mechanism of Cu2+ removal by Egeria densa

In this work the PIXE technique was used to study the mechanism of metal sorption by dead biomass. Several batch copper-sorption experiments were performed by using Egeria densa biomass. PIXE measurements were performed in solid and liquid samples. Element concentrations in biosorbent samples were determined using the Clara software. Based on the mass balance among the major elements in the liquid and solid phases before and after the Cu-removal experiments, an ion exchange process is suggested as the main mechanism.

Biosorption of strontium from aqueous solution by fungus Aspergillus terreus

INTRODUCTION

The biosorption characteristics of strontium ions using fungus Aspergillus terreus were investigated. Experimental parameters affecting the biosorption process such as pH, contact time, initial metal concentration, and temperature were studied.

MATHEMATICAL DESCRIPTION

Fungus A. terreus exhibited the highest strontium uptake capacity at 15°C at an initial strontium ion concentration of 876 mg L(-1) and an initial pH of 9. Biosorption capacity increased from 219 to 308 mg g(-1) with a decrease in temperature from 45°C to 15°C at this initial strontium concentration. The equilibrium data fitted very well to the Langmuir adsorption model in the concentration range of strontium ions and at all the temperatures studied.

CONCLUSION

Evaluation of the experimental data in terms of biosorption dynamics showed that the biosorption of strontium onto fungus followed the pseudo-second-order dynamics well (R(2) > 0.985). The calculated thermodynamics parameters (-1.64 < ∆G° < -1.93 kJ mol(-1) at temperatures of 45-15°C, ∆H° = -4.83 kJ mol(-1) and ∆S° = -0.01 kJ mol(-1) K(-1)) showed that the biosorption of strontium ions were feasible, spontaneous, and exothermic at the temperature ranges of 15-45°C.

Stress responses of duckweed (Lemna minor L.) and water velvet (Azolla filiculoides Lam.) to anionic surfactant sodium-dodecyl-sulphate (SDS)

Surfactants are used for several purposes and recently they have attracted the attention for their ability to modify the behavior of other preexistent or co-disposed contaminants, although their use or discharge in wastewaters can represent a real or potential risk for the environment. Lemna minor L. and Azolla filiculoides Lam. are floating aquatic macrophytes, very effective in accumulating several pollutants including sodium dodecyl sulphate (SDS). In this work we evaluated the effects of SDS on these species by determining the stress ethylene production via laser-based trace gas detection, and the activities of enzymes involved in stress response, such as guaiacol peroxidase (G-POD), phenylalanine ammonia-lyase (PAL) and polyphenol-oxidase (PPO). Phenolics content was also determined. The macrophytes were treated with different concentrations of SDS for one week. SDS affected duckweed enzymatic activities and phenol content. While in the fern phenolics amount, PAL, G-POD and PPO activities were not affected by SDS except for 100 ppm SDS, the only concentration that was taken up and not completely degraded. Stress ethylene production was induced only in the fern treated with 50 and 100 ppm SDS.

Phytoremediation potential of aquatic macrophyte, Azolla

Aquatic macrophytes play an important role in the structural and functional aspects of aquatic ecosystems by altering water movement regimes, providing shelter to fish and aquatic invertebrates, serving as a food source, and altering water quality by regulating oxygen balance, nutrient cycles, and accumulating heavy metals. The ability to hyperaccumulate heavy metals makes them interesting research candidates, especially for the treatment of industrial effluents and sewage waste water. The use of aquatic macrophytes, such as Azolla with hyper accumulating ability is known to be an environmentally friendly option to restore polluted aquatic resources. The present review highlights the phytoaccumulation potential of macrophytes with emphasis on utilization of Azolla as a promising candidate for phytoremediation. The impact of uptake of heavy metals on morphology and metabolic processes of Azolla has also been discussed for a better understanding and utilization of this symbiotic association in the field of phytoremediation.

Biosorption of cesium(I) from aqueous solution by a novel exopolymers secreted from Pseudomonas fluorescens C-2: equilibrium and kinetic studies

The biosorption characteristics of Cs(I) ions from aqueous solution using exopolymers (PFC02) produced from Pseudomonas fluorescens C-2 were investigated as a function of pH, biosorbent dosage, contact time and initial concentration. pH played a major role in the adsorption process, and the optimum pH for the removal of Cs(I) was 8.0. Langmuir, Freundlich and Dubinin-Radushkevich (D-R) models were applied to describe the biosorption isotherm of the Cs(I) ions by PFC02. The Lagergren first-order, pseudo second-order kinetic and intraparticle diffusion models were used to test the kinetic data. Langmuir model and D-R model fitted the equilibrium data better than the Freundlich isotherm. The monolayer adsorption capacities of PFC02 as obtained from Langmuir isotherm at 25 degrees C was found to be 32.63 mg/g. From the D-R isotherm model, the mean free energy was calculated as 26.73 kJ/mol, indicating that the biosorption of cesium was chemisorption. The biosorption process was rapid, and the kinetic rates were best fitted to the pseudo second-order model, which indicated the biosorption process operated through chemisorption mechanism. FT-IR analysis of PFC02 showed the possible functional groups responsible for cesium adsorption were hydroxyl, carboxyl, carbonyl and sulphonate groups. SEM analysis showed the porous structure of the material while EDX analysis confirmed the adsorption of Cs(I) on PFC02. Cesium adsorbed onto the PFC02 could be desorbed efficiently using 1 mol/L HNO3, and the enrichment factor was 50.0. Furthermore, PFC02 could be reused five times with only about 8.25% regeneration loss. The developed method was successfully utilized for the removal of Cs(I) ions from aqueous solution.

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.