Effective biosorption of uranium from aqueous solution by cyanobacterium Anabaena flos-aquae

Cyanoremediation of heavy metals (As(v), Cd(ii), Cr(vi), Pb(ii)) by live cyanobacteria (Anabaena variabilis, and Synechocystis sp.): an eco-sustainable technology

The cyanoremediation technique for heavy metal (HM) removal from wastewater using live cyanobacteria is promising to reduce the pollution risk both for the environment and human health. In this study, two widely recognized freshwater cyanobacteria, Anabaena variabilis and Synechocystis sp., were used to explore their efficacy in HM (As(v), Cd(ii), Cr(vi), Pb(ii)) removal. The different optimum adsorption conditions were pH 8 and 7.5 for A. variabilis and Synechocystis sp., respectively, but the temperature (25 °C) and contact time (48 hours) were the same for both strains. Under these specified conditions, A. variabilis exhibited the capability to remove 25% of As(v), 78% of Cd(ii), 54% of Cr(vi), and 17% of Pb(ii), whereas Synechocystis sp. removed 77% of As(v), 57% of Cd(ii), 91% of Cr(vi), and 77% of Pb(ii) at different initial concentrations. Metal diversity interfered negatively with cyanobacterial growth, especially Cd(ii) and As(v), as measured by OD730, dry biomass, chlorophyll a, and carotenoid production for both strains. Fourier transform infrared spectrum (FT-IR) analysis revealed the existence of diverse surface binding sites for HM adsorption, stemming from proteins and polysaccharides. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) confirmed the presence of HMs on the surface of the cyanobacterial cells. Finally, the zeta potential results indicating alterations in the surface negative charges elucidated the adsorption mechanisms involved in the HM removal by both cyanobacteria. These results provided a comprehensive understanding of the HM adsorption mechanism by cyanobacteria, offering valuable theoretical insights that can be extrapolated to enhance our comprehension of the cyanoremediation mechanisms by various other cyanobacterial strains.

Bacillus sp. strain MRS-1: A potential candidate for uranyl biosorption from uranyl polluted sites

The uranyl tolerance of a metal-resistant Bacillus sp. strain MRS-1, was determined in this current study. This was done due to a rise in anthropogenic activities, such as the production of uranium-based nuclear energy, which contributes to environmental degradation and poses risks to ecosystems and human health. The purpose of the research was to find effective strategies for uranium removal to minimize the contamination. In this paper, the biosorption of uranyl was investigated by batch tests. Bacteria could continue to multiply up to 350 ppm uranyl concentrations, however this growth was suppressed at 400 ppm, that generally accepted as the minimum concentration for bacterial growth inhibition. The optimal conditions for uranyl biosorption were pH 7, 20 °C, and a contact duration of 30 min with living bacteria. According to the findings of an investigation that used isotherm and kinetics models (Langmuir, Freundlich and pseudo second order), Bacillus sp. strain MRS-1 biosorption seemed to be dependent on monolayer adsorption as well as certain functional groups that had a strong affinity for uranyl confirmed by Fourier Transform Infrared Spectroscopy (FTIR) analysis. The shifts/sharping of peaks (1081-3304 cm-1) were prominent in treated samples compared to control one. These functional groups could be hydroxyl, amino, and carboxyl. Our findings showed that Bacillus sp. strain MRS-1 has an elevated uranyl biosorption ability, with 24.5 mg/g being achieved. This indicates its potential as a powerful biosorbent for dealing with uranium contamination in drinking water sources and represents a breakthrough in the cleanup of contaminated ecosystems.

Highly effective sustainable membrane based cyanobacteria for uranium uptake from aqueous environment

Wastewater from industrial process of uranium ore mining contains a large amount of this radioactive pollutant. Regarding the advantages of biosorption, it was found that varieties of biomasses such as agricultural waste, algae and fungi are effective for uranium removal. However, there is limited research on cyanobacteria, therefore, cyanobacteria, Anagnostidinema amphibium (CAA) was investigated by batch method for the first time for biosorption of uranium (VI). Optimization of biosorption parameters showed that maximum removal efficiency of 92.91% was reached at pH range of 9-11 with 50 mg of cyanobacteria to 100 mg/L U(VI) initial concentration, at 25 °C within 40 min. Used biosorbent exhibited very good selectivity for U(VI) ions and reusability in IV sorption/desorption cycles. Characterization of CAA surface was performed by FTIR, EDS, EDXRF and SEM analysis and it has shown various functional groups (CONH, COOH, OH, PO alkyl group) and that it is very rich in elements such as iron, potassium and calcium. In binary systems, contained of U(VI) and selected ions, CAA exhibits very good selectivity towards U(VI) ions. Kinetic data revealed the best accordance of experimental data with the pseudo-second-order model and isotherms data agreed with Freundlich model. Thermodynamic data implied that U(VI) biosorption process by A. amphibium exhibited spontaneity and modelling of the investigated process showed that the adsorption of uranium ions occurs mainly via peptidoglycan carboxyl groups. Overall results show that these cyanobacteria with a maximum sorption capacity of 324.94 mg/g have great potential for the processing of wastewater polluted with uranium (VI).

Pb2+-imprinted thermosensitive antibacterial adsorbent derived from sodium alginate and PNIPAM for Pb2+ recovery

Two sodium alginate-based Pb²⁺-imprinted thermosensitive hydrogels (SPIT (without ɛ-PL) and SPPIT (with ɛ-PL)) were synthesized, with sodium alginate and ɛ-polylysine (ɛ-PL) as the matrix, N-isopropylacrylamide as the monomer. Characterization with differential scanning calorimeter, Fourier transform infrared spectroscopy, thermogravimetric analyzer, scanning electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy confirmed the aimed structure of the hydrogels. The adsorption capacity of SPIT and SPPIT for Pb²⁺ was 98.64 mg/g and 153.49 mg/g, respectively. Washing the Pb²⁺-loaded adsorbent with 10 °C deionized water, SPIT and SPPIT achieved a desorption efficiency of 94.59 % and 97.51 %, respectively. After 10 cycles of adsorption-desorption process, the adsorption capacity and desorption efficiency remained at about 80-88 % of the original ones, expressing excellent reusability. In a mixture containing eight metal ions (Pb²⁺, Cu²⁺, Mg²⁺, Ca²⁺, Cd²⁺, Na⁺, K⁺, Fe³⁺), the adsorption capacity of SPIT to Pb²⁺ was 92.49 mg/g, and that of SPPIT was 102.49 mg/g, much higher than that to the other ions (1.50-11.38 mg/g on SPIT, 9.48-27.45 mg/g on SPPIT), showing excellent adsorption selectivity. The introduction of ɛ-PL enhanced the adsorption capacity, antibacterial ability and stability of the hydrogel, ensuring better application potential in real wastewater.

Uranium biosorption by hydroxyapatite and bone meal: evaluation of process variables through experimental design

Biosorption has been examined for the treatment of aqueous solutions containing uranium, a radiotoxic pollutant. Nevertheless, the evaluation of the role of process variables by experimental design on the use of hydroxyapatite and bone meal as biosorbents for uranium has not yet been previously addressed. In this study, the effects of adsorbent dosage (M), initial uranium concentrations ([U]0), and solution pH were investigated, using a two-level factorial design and response surface analysis. The experiments were performed in batch, with [U]0 of 100 and 500 mg L-1, pH 3 and 5, and adsorbent/uranium solution ratios of 5 and 15 g L-1. Contact time was fixed at 24 h. Removal rates were higher than 88%, with a maximum of 99% in optimized conditions. [U]0 and M were found to be the most influential variables in U removal in terms of adsorption capacity (q). The experiments revealed that bone meal holds higher adsorption capacity (49.87 mg g-1) and achieved the highest uranium removal (~ 100%) when compared to hydroxyapatite (q = 49.20 mg g-1, removal = 98.5%). The highest value of q for both biomaterials was obtained for [U]0 = 500 mg L-1, pH 3, and M = 5 g L-1. Concerning the removal percentage, bone meal achieved the best performance for [U]0 = 500 mg L-1, pH 3, and M = 15 g L-1. Further experiments were made with real radioactive waste, resulting in a high uranium adsorption capacity for both materials, with 22.11 mg g-1 for hydroxyapatite and 22.08 mg g-1 for bone meal, achieving uranium removal efficiencies higher than 99%.

Biosorption of uranium by immobilized Nostoc sp. and Scenedesmus sp.: kinetic and equilibrium modeling

Different activities related to uranium mining and nuclear industry may have a negative impact on the environment. Bioremediation of nuclear pollutants using microorganisms is an effective, safe, and economic method. The present study compared the uranium biosorption efficiency of two immobilized algae: Nostoc sp. (cyanophyte) and Scenedesmus sp. (chlorophyte). Effects of metal concentration, contact time, pH, and biosorbent dosage were also studied. The maximum biosorption capacity (60%) by Nostoc sp. was obtained at 300 mg/l uranium solution, 60 min, pH 4.5, and 4.2 g/l algal dosage, whereas Scenedesmus sp. maximally absorbed uranium (65 %) at 150 mg/l uranium solution, 40 min, pH 4.5, and 5.6 g/l of algal dosage. The interaction of metal ions as Na₂SO₄, FeCl₃, CuCl₂, NiCl₂, CoCl₂, CdCl₂, and AlCl₃ did not support the uranium biosorption by algae. The obtained data was adapted to the linearized form of the Langmuir isotherm model. The experimental q_max values were 130 and 75 mg/g for Nostoc sp. and Scenedesmus sp., respectively. Moreover, the pseudo-second-order kinetic model was more applicable, as the calculated parameters were close to the experimental data. The biosorbents were also characterized by Fourier-transform infrared spectroscopy (ATR-FTIR), energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM) analyses. The results suggest the applicability of algae, in their immobilized form, for recovery and biosorption of uranium from aqueous solution.

Ecofriendly Composite as a Promising Material for Highly-Performance Uranium Recovery from Different Solutions

The development of new materials based on biopolymers (as renewable resources) is substantial for environmental challenges in the heavy metal and radionuclide ions removal contaminations. Functionalization of chitosan with sulfonic groups was achieved for improving the uranium sorption, not only from slightly acidic leachate, but also for the underground water. The prepared hydrogel based on chitosan was characterized by series of analysis tools for structure elucidation as FTIR spectroscopy, textural properties using nitrogen adsorption method, pH_PZC (by pH-drift method), thermogravimetric analysis (TGA), SEM, and SEM-EDX analyses. The sorption was performed toward uranium (VI) ions for adjustment of sorption performances. The optimum sorption was performed at pH 4 (prior to the precipitation pH). The total sorption was achieved within 25 min (relatively fast kinetics) and was fitted by pseudo-first order rate equation (PFORE) and resistance to intraparticle diffusion equation (RIDE). The maximum sorption capacity was around 1.5 mmol U g^-1. The sorption isotherms were fitted by Langmuir and Sips equations. Desorption was achieved using 0.3 M HCl solution and the complete desorption was performed in around 15 min of contact. The sorption desorption cycles are relatively stable during 5 cycles with limit decreasing in sorption and desorption properties (around 3 ± 0.2% and 99.8 ± 0.1%, respectively). The sorbent was used for removal of U from acid leachate solution in mining area. The sorbent showed a highly performance for U(VI) removal, which was considered as a tool material for radionuclides removing from aquatic medium.

Biosorption of Uranium from aqueous solution by green microalga Chlorella sorokiniana

Uranium and its compounds are radioactive and toxic, as well as highly polluting and damaging the environment. Novel uranium adsorbents with high biosorption capacity that are both eco-friendly and cost-effective are continuously being researched. The non-living biomass of the fresh water green microalga Chlorella sorokiniana was used to study the biosorption of uranium from aqueous solution. The biosorption of uranium from aqueous solutions onto the biomass of microalga C. sorokiniana was investigated in batch studies. The results showed that the optimal pH for uranium biosorption onto C. sorokiniana was 2.5. Uranium biosorption occurred quickly, with an equilibrium time of 90 min. The kinetics followed a pseudo-second-order rate equation, and the biosorption process fit the Langmuir isotherm model well, with a maximum monolayer adsorption capacity of 188.7 mg/g. The linear plot of the DKR model revealed that the mean free energy E = 14.8 kJ/mol, confirming chemisorption adsorption with ion exchange mode. The morphology of the algal biomass was investigated using a scanning electron microscope and energy dispersive X-ray spectroscopy. The FTIR spectroscopy analysis demonstrated that functional groups (carboxyl, amino, and hydroxyl) on the algal surface could contribute to the uranium biosorption process, which involves ion exchange and uranium absorption, and coordination mechanisms. Thermodynamic simulations indicated that the uranium biosorption process was exothermic (ΔH = -19.5562 kJ/mol) and spontaneous at lower temperatures. The current study revealed that C. sorokiniana non-living biomass could be an efficient, rapid, low-cost, and convenient method of removing uranium from aqueous solution.

A critical review of uranium contamination in groundwater: Treatment and sludge disposal

Dissolved uranium in groundwater at high concentrations is an emerging global threat to human and ecological health due to its radioactivity and chemical toxicity. Uranium can enter groundwater by geochemical reactions, natural deposition from minerals, mining, uranium ore processing, and spent fuel disposal. Although much progress has been made in uranium remediation in recent years, most published reviews on uranium treatment have focused on specific methods, particularly adsorption. This article systematically reviews the major treatment technologies, explains their mechanism and progress of uranium removal, and compares their performance under various environmental conditions. Of all treatment methods, adsorption has received much attention due to its ease of use and adaptability under various conditions. However, salinity and competition from other ions limit its application in actual field conditions. Biosorption and bioremediation are also promising methods due to their low-cost and chemical-free operation. Strong base anion exchange resins are more effective at typical groundwater pH conditions. Advanced oxidation processes like photocatalysis produce less sludge and are effective even at low uranium concentrations. Electrocoagulation shows significantly improved performance when organic ligands are added prior to treatment. The significant advantages of membrane filtration are high removal efficiency and the ability to recover uranium. While each technology has its merits and demerits, no single technology is entirely suitable under all conditions. One major area of concern with all technologies is the need to dispose of liquid and solid waste generated after treatment safely. Future research must focus on developing hybrid and state-of-the-art technologies for effective and sustainable uranium removal from groundwater. Developing holistic management strategies for uranium removal will hinge on understanding its speciation, mechanisms of fate and transport, and socio-economic conditions of the affected areas.

U(VI) and Th(IV) recovery using silica beads functionalized with urea- or thiourea-based polymers - Application to ore leachate

Urea and thiourea have been successfully deposited at the surface of silica beads (through one-pot reaction with formaldehyde) for designing new sorbents for U(VI) and Th(IV) recovery (UR/SiO₂ and TUR/SiO₂ composites, respectively). These materials have been characterized by FTIR, titration, elemental analysis, BET, TGA, SEM-EDX for identification of structural and chemical properties, and interpretation of binding mechanisms. Based on deprotonation of reactive groups (amine, carbonyl, or thiocarbonyl) and metal speciation, the optimum pH was ~4. Uptake kinetics was fast (equilibrium within 60-90 min). Although the kinetic profiles are fitted by the pseudo-first order rate equation, the resistance to intraparticle diffusion cannot be neglected. Sorption isotherms were fitted by Langmuir equation (maximum sorption capacities: 1-1.2 mmol g^-1). Thermodynamics are also investigated showing differences between the two types of functionalized groups: exothermic for TUR/SiO₂ and endothermic for UR/SiO₂. Metal desorption is highly effective using 0.3-0.5 M HCl solutions: total desorption occurs within 30-60 min; sorption/desorption properties are remarkably stable for at least 5 cycles. The sorbents have marked preference for U(VI) and Th(IV) over alkali-earth and base metals at pH_eq ~4.8. By preliminary precipitation steps, it is possible "cleaning" ore leachates of pegmatite ore, and recovering U(VI) and Th(IV) using functionalized silica beads. After elution and selective recovery by precipitation with oxalate (Th-cake) and alkaline (U-cake), the metals can be valorized.