Characteristics of uranium biosorption from aqueous solutions on fungus Pleurotus ostreatus

Active carbon-based waste packaging materials for uranium sorption from aqueous solution

Waste (packaging plastic and industrial water) accumulation is one of the great global challenges over the world. Combining waste recycling science and water treatment knowledge are fascinating as applied sciences add value to the safe disposal of waste plastic packaging materials and wastewater. Active carbons (ACs) are prepared from polyethylene terephthalate (PET) at two pyrolysis temperatures (i.e. 450 and 500 °C) and compressed in well-defined designed molds to form cylinder shapes as applied in industry. Particle size (817 and 1074 nm), zeta potential (- 7.17 and - 25.6 mV), surface area (544 and 632 m2/g), and topography of prepared ACs were investigated and discussed. Zeta potential exhibited nice dispersion in accordance to charge value and surficial SEM images prove space hole filling with adsorbed materials after treatment. The prepared activated carbon sorbents have been applied for the removal of radioactive elements from wastewater. The displayed data declare that both sorbents have the same sorption performance, whereas the uranium sorption process using both sorbents is obeyed to pseudo-second-order kinetic model and Langmuir isotherm model. Nevertheless, it is worth noting that the prepared AC at a pyrolysis temperature of 500 °C exhibits higher sorption capacity (38.9 mg g^-1) than that prepared at lower temperature, i.e., 450 °C (36.2 mg g^-1) which indicates that the increase in pyrolysis temperature improves the sorption characteristics of the yield-activated carbon.

Soya bean derived activated carbon as an efficient adsorbent for capture of valuable heavy metals from waste aqueous solution

The removal of hazardous metal ions from liquid waste effluents is very important for water as well as environmental safety. In this regard, this article discusses in detail the U(VI) uptake from aquatic environment using biomass-based Soya Bean activated carbon (labeled as AC-SB). XRD, SEM, FTIR, Raman, and BET analysis were used to characterize the synthesized AC-SB sorbent. Batch-type experiments were used to investigate the effect of various parameters on adsorption efficiency, including pH, metal-ion concentration, temperature, and contact time. The sorption experimental data have been described well with pseudo-second-order kinetic mathematical equations. The equilibrium state of the uptake reaction was 120 min. The Langmuir isotherm model accurately described the equilibrium process which declares that the uranium sorption is a monolayer and homogeneous process. The sorption capacity of the prepared AC was 32.7 mg g−1. Thermodynamic analysis explore that the U(VI) uptake process is endothermic, feasible and spontenous process. The displayed results demonstrate that the prepared AC-SB sorbent could be used as the proper material for uranium sorption from real matrix samples.

New insights into the sorption of U(VI) on kaolinite and illite in the presence of Aspergillus niger

The regulation effect of Aspergillus niger to the sorption behavior of U(VI) on kaolinite and illite was studied through investigating the enrichment of U(VI) on kaolinite-Aspergillus niger and illite-Aspergillus niger composites. Kaolinite- or illite-A. niger composites were prepared through co-culturation method. Results showed that U(VI) sorption on kaolinite and illite in different pH ranges could be attributed to ion exchange, outer-sphere complexes (OSCs), and inner-sphere complexes (ISCs), while only the ISCs on the bio-composites. Moreover, micro-spectroscopy tests revealed that U(VI) coordinate with phosphate, amide, and carboxyl groups on illite- and kaolinite- A. niger composites. X-ray photoelectron spectroscopy (XPS) further found that U(VI) was partly reduced to non-crystalline U(IV) by A. niger in the bio-composites, occurring as phosphate coordination polymers or biomass-associated monomers. The findings herein provide further insight into the immobilization and migration of uranium in environments.

Effect of Temperature and Cell Viability on Uranium Biomineralization by the Uranium Mine Isolate Penicillium simplicissimum

The remediation of heavy-metal-contaminated sites represents a serious environmental problem worldwide. Currently, cost- and time-intensive chemical treatments are usually performed. Bioremediation by heavy-metal-tolerant microorganisms is considered a more eco-friendly and comparatively cheap alternative. The fungus Penicillium simplicissimum KS1, isolated from the flooding water of a former uranium (U) mine in Germany, shows promising U bioremediation potential mainly through biomineralization. The adaption of P. simplicissimum KS1 to heavy-metal-contaminated sites is indicated by an increased U removal capacity of up to 550 mg U per g dry biomass, compared to the non-heavy-metal-exposed P. simplicissimum reference strain DSM 62867 (200 mg U per g dry biomass). In addition, the effect of temperature and cell viability of P. simplicissimum KS1 on U biomineralization was investigated. While viable cells at 30°C removed U mainly extracellularly via metabolism-dependent biomineralization, a decrease in temperature to 4°C or use of dead-autoclaved cells at 30°C revealed increased occurrence of passive biosorption and bioaccumulation, as confirmed by scanning transmission electron microscopy. The precipitated U species were assigned to uranyl phosphates with a structure similar to that of autunite, via cryo-time-resolved laser fluorescence spectroscopy. The major involvement of phosphates in U precipitation by P. simplicissimum KS1 was additionally supported by the observation of increased phosphatase activity for viable cells at 30°C. Furthermore, viable cells actively secreted small molecules, most likely phosphorylated amino acids, which interacted with U in the supernatant and were not detected in experiments with dead-autoclaved cells. Our study provides new insights into the influence of temperature and cell viability on U phosphate biomineralization by fungi, and furthermore highlight the potential use of P. simplicissimum KS1 particularly for U bioremediation purposes.

Graphical Abstract

Constructing new Fe3O4@MnOx with 3D hollow structure for efficient recovery of uranium from simulated seawater

Enrichment of uranium from seawater is a promising method for addressing the energy crisis. Current technologies are generally not effective for enriching uranium from seawater because its concentration in seawater is low. In this study, new Fe₃O₄@MnO_x with 3D hollow structure, which is capable of enriching low concentration uranium, was prepared via a novel redox etching method. The physicochemical characteristics of Fe₃O₄@MnO_x were studied with TEM, HRTEM, SEAD, FTIR, XRD, and N₂ adsorption-desorption analysis. Dynamic kinetic studies of different initial U(VI) concentrations revealed that the pseudo-second-order model fit the sorption process better, and the sorption rates of Fe₃O₄@MnO_x in 1, 10, and 25 mg/L U(VI) solution were 0.0124, 0.00298, and 0.000867 g/mg·min, respectively. Isothermal studies showed that the maximum sorption amounts were 50.09, 56.27, and 64.62 mg/g for 1, 10, and 25 mg/L U(VI), respectively, at pH 5.0 and 313 K, suggesting that Fe₃O₄@MnO_x could effectively enrich low concentration U(VI) from water. The sorption amount of U(VI) did not significantly decrease in the presence of Na⁺, Mg²⁺, and Ca²⁺. HRTEM, FTIR, and XPS results demonstrated that Fe(II) and Mn/Fe-O-H active sites in Fe₃O₄@MnO_x were accounted for the high and specific enrichment efficiency. A column experiment was conducted to evaluate the U(VI) sorption efficiency of Fe₃O₄@MnO_x in simulated seawater. The U(VI) sorption efficiency remained above 80% in 28 days run. Our findings demonstrate that Fe₃O₄@MnO_x has extraordinary potential for the enrichment of uranium from simulated seawater.

Uranium(VI) bioassociation by different fungi - a comparative study into molecular processes

After the Chernobyl and Fukushima incidents it has become clear that fungi can take up and accumulate large quantities of radionuclides and heavy metals, but the underlying processes are not well understood yet. For this study, the molecular interactions of uranium(VI) with the white-rot fungi, Schizophyllum commune and Pleurotus ostreatus, and the soil-living fungus, Leucoagaricus naucinus, were investigated. First, the uranium concentration in the biomass was determined by time-dependent bioassociation experiments. To characterize the molecular interactions, uranium was localized in the biomass by transmission electron microscopy analysis. Second, the formed uranyl complexes in both biomass and supernatant were determined by fluorescence spectroscopy. Additionally, possible bioligands in the supernatant were identified. The results show that the discernible interactions between metals and fungi are similar, namely biosorption, accumulation, and subsequent crystallization. But at the same time, the underlying biochemical mechanisms are different and specific to the fungal species. In addition, Schizophyllum commune was found to be the only fungus that, under the chosen experimental conditions, released tryptophan and other indole derivatives in the presence of uranium(VI) as determined by nuclear magnetic resonance spectroscopy. These released substances most likely act as messenger molecules rather than serving the direct detoxification of uranium(VI).

Applying Cryo-X-ray Photoelectron Spectroscopy to Study the Surface Chemical Composition of Fungi and Viruses

Interaction between microorganisms and their surroundings are generally mediated via the cell wall or cell envelope. An understanding of the overall chemical composition of these surface layers may give clues on how these interactions occur and suggest mechanisms to manipulate them. This knowledge is key, for instance, in research aiming to reduce colonization of medical devices and device-related infections from different types of microorganisms. In this context, X-ray photoelectron spectroscopy (XPS) is a powerful technique as its analysis depth below 10 nm enables studies of the outermost surface structures of microorganism. Of specific interest for the study of biological systems is cryogenic XPS (cryo-XPS). This technique allows studies of intact fast-frozen hydrated samples without the need for pre-treatment procedures that may cause the cell structure to collapse or change due to the loss of water. Previously, cryo-XPS has been applied to study bacterial and algal surfaces with respect to their composition of lipids, polysaccharides and peptide (protein and/or peptidoglycan). This contribution focuses onto two other groups of microorganisms with widely different architecture and modes of life, namely fungi and viruses. It evaluates to what extent existing models for data treatment of XPS spectra can be applied to understand the chemical composition of their very different surface layers. XPS data from model organisms as well as reference substances representing specific building blocks of their surface were collected and are presented. These results aims to guide future analysis of the surface chemical composition of biological systems.

Potential Usage of Edible Mushrooms and Their Residues to Retrieve Valuable Supplies for Industrial Applications

Currently, the food and agricultural sectors are concerned about environmental problems caused by raw material waste, and they are looking for strategies to reduce the growing amount of waste disposal. Now, approaches are being explored that could increment and provide value-added products from agricultural waste to contribute to the circular economy and environmental protection. Edible mushrooms have been globally appreciated for their medicinal properties and nutritional value, but during the mushroom production process nearly one-fifth of the mushroom gets wasted. Therefore, improper disposal of mushrooms and untreated residues can cause fungal disease. The residues of edible mushrooms, being rich in sterols, vitamin D2, amino acids, and polysaccharides, among others, makes it underutilized waste. Most of the published literature has primarily focused on the isolation of bioactive components of these edible mushrooms; however, utilization of waste or edible mushrooms themselves, for the production of value-added products, has remained an overlooked area. Waste of edible mushrooms also represents a disposal problem, but they are a rich source of important compounds, owing to their nutritional and functional properties. Researchers have started exploiting edible mushroom by-products/waste for value-added goods with applications in diverse fields. Bioactive compounds obtained from edible mushrooms are being used in media production and skincare formulations. Furthermore, diverse applications from edible mushrooms are also being explored, including the synthesis of biosorbent, biochar, edible films/coating, probiotics, nanoparticles and cosmetic products. The primary intent of this review is to summarize the information related to edible mushrooms and their valorization in developing value-added products with industrial applications.

U(VI) adsorption in water by sodium alginate modified Bacillus megaterium

The surface of Bacillus megaterium was modified by coating sodium alginate. The modified B. megaterium before and after adsorption were characterized by SEM, FTIR and XPS. The effects of pH, reaction time, initial U(VI) concentration and adsorbent dosage on the adsorption of U(VI) by the modified B. megaterium were studied by batch adsorption experiments. The adsorption process was studied by pseudo-first-order kinetics and pseudo-second-order kinetic models, Langmuir and Freundlich isotherms. The results showed that the maximum adsorption capacity of U(VI) was 74.61 mg g^-1 under the conditions of pH 5.0, adsorbent 0.2 g l^-1, 30°C and initial U(VI) concentration of 15 mg l^-1. The adsorption process accords with pseudo-first-order kinetics and Langmuir isotherm. The adsorption capacity of U(VI) by the modified B. megaterium was still higher than 80% after five times of desorption and reuse experiments. In conclusion, the sodium alginate modified B. megaterium was an ideal material for U(VI) biosorption.

Preparation and uranium (VI) biosorption for tri-amidoxime modified marine fungus material

The preparation, characterization, and uranium (VI) adsorption properties of tri-amidoxime modified marine fungus material (ZZF51-GPTS-EDA-AM/ZGEA) were investigated in this study. ZGEA was synthesized by four steps of condensation, nucleophilic substitution, electrophilic addition, and nitrile amidoxime and characterized by a series of methods containing FT-IR, TGA, SEM, and BET. Contrasted with uranium (VI) adsorption capacity of original fungus mycelium (15.46 mg g^-1) that of the functional material (584.60 mg g^-1) was great under the optimal factors such as uranium (VI) ion concentration 40 mg L^-1, solid-liquid ratio 50 mg L^-1, pH of solution 5.5, and reaction time 120 min. The above data were obtained by the orthogonal method. The cyclic tests showed that ZGEA had good regeneration performance, and it could be recycled at least five adsorption-desorption processes. The thermodynamic experimental adsorption result fitted Langmuir and Freundlich models, which explored monolayer and double layers of uranium (VI) adsorption mechanism, and the kinetic adsorption results were in better consistent with the pseudo-second-order and pseudo-first-order dynamic models (R² > 0.999).

Ultrafast Recovery of Uranium from Seawater by Bacillus velezensis Strain UUS-1 with Innate Anti-Biofouling Activity

Highly-efficient recovery of uranium from seawater is of great concern in the growing demand for nuclear energy. Bacteria are thought to be potential alternatives for uranium recovery. Herein, a Bacillus velezensis strain, UUS-1, with highly-efficient uranium immobilization capacity is isolated and is used in the recovery of uranium from seawater. The strain exhibits time-dependent uranium recovery capacity and only immobilizes uranium after growing for 12 h. The carboxyl group together with the amino group inside the bacterial cells, but not previously identified phosphate group, are essential for uranium immobilization. UUS-1 shows broad-spectrum antimicrobial activity by producing diverse antimicrobial metabolites, which endows the strain with innate resistance to the biofouling of marine microorganisms. Based on the dry weight of the initially used bacterial cultures, UUS-1 concentrates uranium by 6.26 × 105 times and reaches the high immobilization capacity of 9.46 ± 0.39 mg U g-1 bacterial cultures in real seawater within 48 h, which is the fastest uranium immobilization capacity observed from real seawater. Overall considering the ultrafast and highly-efficient uranium recovery capacity and the innate anti-biofouling activity, UUS-1 is a promising alternative for uranium recovery from seawater.

Preparation, uranium (VI) absorption and reuseability of marine fungus mycelium modified by the bis-amidoxime-based groups

Bis-amidoxime-based claw-like-functionalized marine fungus material (ZZF51-GPTS-DCDA-AM) was prepared for study to absorb the low concentration uranium (VI) from aqueous solution. A series of characterization methods such as SEM, TGA and FT-IR were applied for the functionalized materials before and after modification and adsorption. The experimental results suggested that the amidoxime groups were successfully grafted onto the surface of mycelium powder and provided the special binding sites for the absorption of uranium (VI). In the absorption research, uranium (VI) initial concentration, pH and equilibrium time were optimized as 40 mg L−1, 6.0, and 110 min by L4 3 orthogonal experiment, respectively, and the maximum absorption capacity of the prepared material was 370.85 mg g−1 under the optimum batch conditions. After five cycling process, the desorption rate and regeneration efficiency of the modified mycelium were found to be 80.29 % and 94.51 %, respectively, which indicated that the material had an adequately high reusability property as a cleanup tool. The well known Langmuir and Freundlich isotherm adsorption model fitting found that the modified materials had both monolayer and bilayer adsorption to uranium (VI) ions. Simultaneously, the pseudo-second-order model was better to illustrated the adsorption kinetics process. The enhanced adsorption capacity of uranium (VI) by the modified fungus materials over raw biomass was mainly owing to the strong chelation of amidoxime groups and uranium (VI) ions.

pH-dependent microbial reduction of uranium(VI) in carbonate-free solutions: UV-vis, XPS, TEM, and thermodynamic studies

U(VI)_aq bioreduction has an important effect on the fate and transport of uranium isotopes in groundwater at nuclear test sites. In this study, we focus on the pH-dependent bioreduction of U(VI)_aq in carbonate-free solutions and give mechanistic insight into the removal kinetics of U(VI)_aq. An enhancement in the removal of U(VI)_aq with increasing pH was observed within 5 h, e.g., from 19.4% at pH 4.52 to 99.7% at pH 8.30. The removal of U(VI)_aq at pH 4.52 was due to the biosorption of U(VI)_aq onto the living cells of Shewanella putrefaciens, as evidenced by the almost constant UV-vis absorption intensity of U(VI)_aq immediately after contact with S. putrefaciens. Instead, the removal observed at pH 5.97 to 8.30 resulted from the bioreduction of U(VI)_aq. The end product of U(VI)_aq bioreduction was analyzed using XPS and HRTEM and identified as nanosized UO₂. An increasing trend in the biosorption of U(VI)_aq onto heat-killed cells was also observed, e.g., ~ 80% at pH 8.38. Evidently, the U(VI)_aq that sorbed onto the living cells at pH > 4.52 was further reduced to UO₂, although biosorption made a large contribution to the initial removal of U(VI)_aq. These results may reveal the removal mechanism, in which the U(VI)_aq that was sorbed onto cells rather than the U(VI)_aq complexed in solution was reduced. The decreases in the redox potentials of the main complex species of U(VI)_aq (e.g., [Formula: see text] and [Formula: see text]) with increasing pH support the proposed removal mechanism.

226Ra, 238U and Cd adsorption kinetics and binding capacity of two cyanobacterial strains isolated from highly radioactive springs and optimal conditions for maximal removal effects in contaminated water

Biomass-based decontamination methods are among the most interesting water treatment techniques. In this study, 2 cyanobacterial strains, Nostoc punctiforme A.S/S4 and Chroococcidiopsis thermalis S.M/S9, isolated from hot springs containing high concentrations of radium (²²⁶Ra), were studied to be associated with removal of radionuclides (²³⁸U and ²²⁶Ra) and heavy metal cadmium (Cd) from aqueous solutions. The adsorption equilibrium data was described by Langmuir and Freundlich isotherm models. Kinetic studies indicated that the sorption of 3 metals followed pseudo-second-order kinetics. Effects of biomass concentration, pH, contact time, and initial metal concentration on adsorption were also investigated. Fourier-transform infrared spectroscopy revealed active binding sites on the cyanobacterial biomass. The obtained maximum biosorption capacities were 630 mg g^-1 and 37 kBq g^-1 for ²³⁸U and ²²⁶Ra for N. punctiforme and 730 mg g^-1 and 55 kBq g^-1 for C. thermalis. These 2 strains showed maximum binding capacity 160 and 225 mg g^-1, respectively for Cd adsorption. These results suggest that radioactivity resistant cyanobacteria could be employed as an efficient adsorbent for decontamination of multi-component, radioactive and industrial wastewater.

Adsorption behavior of U(VI) on doped polyaniline: the effects of carbonate and its complexes

In carbonate-buffer seawater or salt lake brines, three main uranium complexes, U(VI)-CO3 and Ca/Mg-U(VI)-CO3 complexes had been highlighted so far. In this paper, the effects of carbonate and its complexes on U(VI) adsorption onto doped polyaniline (PANI) were investigated using batch adsorption experiments. The adsorption equilibrium of U(VI) on doped PANI was reached within 30 min of contact time when U(VI)-CO3 complexes dominated the aqueous chemistry. Pseudo-second order and Langmuir isotherm models indicated that adsorption occurred on the homogeneous surface via monolayer chemisorption. Moreover, the increase in pHinitial, dissolved carbonate, calcium and magnesium concentrations could suppress the uranium adsorption process. The adsorption mechanisms under the weakly basic conditions were primarily involved in uranium anion species adsorption on nitrogen-containing functional groups instead of the anion exchange reactive sites on the doped PANI surface sites, whereas the U(VI)-CO3 complexes had a greater affinity than the Ca/Mg-U(VI)-CO3 complexes. The findings of this study are significant for the extraction of uranium resources from salt lake brines or seawater and for the prediction of uranium adsorption behaviors in weakly basic solution environments.

Lead and uranium sorptive removal from aqueous solution using magnetic and nonmagnetic fast pyrolysis rice husk biochars

This paper discusses the sorption characteristics of Pb(ii) and U(vi) on magnetic and nonmagnetic rice husk biochars.

Preparation, characterization, uranium (VI) biosorption models, and conditions optimization by response surface methodology (RSM) for amidoxime-functionalized marine fungus materials

Amidoxime-functionalized marine fungus Fusarium sp. #ZZF51 (ZGDA) was synthesized and studied to adsorb uranium (VI) from the aqueous solution. Different instrumental techniques such as FTIR, SEM, and TGA were employed for the characterization of the manufactured materials, and theirs ability of removal uranium (VI) was optimized using RSM. The experimental results showed the maximum adsorption capacity for the synthesized materials was 230.78 mg g−1 at the following optimization conditions: S–L ratio 150 mg L−1, pH 5.13, uranium (VI) initial concentration 40 mg L−1, and equilibrium time 122.40 min. More than 85% of the absorbed uranium (VI) could be desorbed by 0.5 or 1.0 mol L−1 HCl, and the modified mycelium could be reused at least five times. The thermodynamic experimental data of adsorption uranium (VI) could fit better with Langumir and Freundlich isotherms models, and the pseudo-second-order model was better to interpret the kinetics process. The modified fungus materials exhibited the better sorption capacity for uranium (VI) in comparison with raw biomass should be attributed to the strong chelation of amidoxime to uranium (VI) ions.