Utilization of Banana Peel as a Novel Substrate for Biosurfactant Production by Halobacteriaceae archaeon AS65

In this study, biosurfactant-producing bacteria was evaluated for biosurfactant production by using banana peel as a sole carbon source. From the 71 strains screened, Halobacteriaceae archaeon AS65 produced the highest biosurfactant activity. The highest biosurfactant production (5.30 g/l) was obtained when the cells were grown on a minimal salt medium containing 35 % (w/v) banana peel and 1 g/l commercial monosodium glutamate at 30 °C and 200 rpm after 54 h of cultivation. The biosurfactant obtained by extraction with ethyl acetate showed high surface tension reduction (25.5 mN/m), a small critical micelle concentration value (10 mg/l), thermal and pH stability with respect to surface tension reduction and emulsification activity, and a high level of salt tolerance. The biosurfactant obtained was confirmed as a lipopeptide by using a biochemical test FT-IR, NMR, and mass spectrometry. The crude biosurfactant showed a broad spectrum of antimicrobial activity and had the ability to emulsify oil, enhance PAHs solubility, and oil bioremediation.     

Exopolysaccharides and Antimicrobial Biosurfactants Produced by Paenibacillus macerans TKU029

Paenibacillus macerans TKU029 can produce exopolysaccharides (EPSs; 3.46 g/L) and a biosurfactant (1.78 g/L) in a medium with 2 % (w/v) squid pen powder as the sole carbon/nitrogen source. The biosurfactant can reduce the surface tension of water from 72.30 to 35.34 mN/m at a concentration of 2.76 g/L and reach an emulsification index of 56 % after a 24-h reaction with machine oil. This biosurfactant is stable at 121 °C for 20 min, over a pH range from 3 to 11, and in <5 % salt solutions. It also shows significant antimicrobial activity, which remains active after treatment at 121 °C and at pH values from 4 to 10, against Escherichia coli BCRC13086, Staphylococcus aureus BCRC10780, Fusarium oxysporum BCRC32121 and Aspergillus fumigatus BCRC30099. Furthermore, human skin shows from 37.3 to 44.3 % hydration after being treated with TKU029 EPSs for 180 min. These results imply that EPSs and the biosurfactant from this strain have potential in cosmetics, for removal of oil contamination, and as antimicrobial agents.     

Interactive optimization of biosurfactant production by Paenibacillus alvei ARN63 isolated from an Iranian oil well

The potential of an indigenous bacterial strain isolated from an Iranian oil field for the production of biosurfactant was investigated in this study. After isolation, the bacterium was characterized to be Paenibacillus alvei by biochemical tests and 16S ribotyping. The biosurfactant, which was produced by this bacterium, was able to lower the surface tension of media to 35 mN/m. Accordingly, thin layer chromatography (TLC) and FT-IR has been carried out to determine compositional analysis of the produced biosurfactant. After all the tests related to characterization of the biosurfactant produced by the isolated bacterium, it was characterized as lipopeptide derivative. The combination of central composite rotatable design (CCRD) and response surface methodology (RSM) was exploited to optimize biosurfactant production. Therefore, variations of four impressive parameters, pH, temperature, glucose and salinity concentrations were selected for optimization of growth conditions. The empirical model developed through RSM in terms of effective operational factors mentioned above was found to be adequate to describe the biosurfactant production. A maximum reduction in surface tension was obtained under the optimal conditions of 13.03 g/l glucose concentration, 34.76 °C, 51.39 g/l total salt concentration and medium pH 6.89.     

Production of Microbial Rhamnolipid by Pseudomonas Aeruginosa MM1011 for Ex Situ Enhanced Oil Recovery

Recently, several investigations have been carried out on the in situ bacteria flooding, but the ex situ biosurfactant production and addition to the sand pack as agents for microbial enhanced oil recovery (MEOR) has little been studied. In order to develop suitable technology for ex situ MEOR processes, it is essential to carry out tests about it. Therefore, this work tries to fill the gap. The intention of this study was to investigate whether the rhamnolipid mix could be produced in high enough quantities for enhanced oil recovery in the laboratory scale and prove its potential use as an effective material for field application. In this work, the ability of Pseudomonas aeruginosa MM1011 to grow and produce rhamnolipid on sunflower as sole carbon source under nitrogen limitation was shown. The production of Rha-C₁₀-C₁₀ and Rha₂-C₁₀-C₁₀ was confirmed by thin-layer chromatography and high-performance liquid chromatography analysis. The rhamnolipid mixture obtained was able to reduce the surface and interfacial tension of water to 26 and 2 mN/m, respectively. The critical micelle concentration was 120 mg/L. Maximum rhamnolipid production reached to about 0.7 g/L in a shake flask. The yield of rhamnolipid per biomass (Y _RL/x ), rhamnolipid per sunflower oil (Y _RL/s ), and the biomass per sunflower oil (Y _x/s ) for shake flask were obtained about 0.01, 0.0035, and 0.035 g g^?1, respectively. The stability of the rhamnolipid at different salinities, pH and temperature, and also, its emulsifying activity has been investigated. It is an effective surfactant at very low concentrations over a wide range of temperatures, pHs, and salt concentrations, and it also has the ability to emulsify oil, which is essential for enhanced oil recovery. With 120 mg/L rhamnolipid, 27 % of original oil in place was recovered after water flooding from a sand pack. This result not only suggests rhamnolipids as appropriate model biosurfactants for MEOR, but it even shows the potential as a biosurfactant of choice for actual MEOR applications.     

The influence of vegetable oils on biosurfactant production by Serratia marcescens

The production of biosurfactant, a surface-active compound, by two Serratia marcescens strains was tested on minimal culture medium supplemented with vegetable oils, considering that it is well known that these compounds stimulate biosurfactant production. The vegetable oils tested included soybean, olive, castor, sunflower, and coconut fat. The results showed a decrease in surface tension of the culture medium without oil from 64.54 to 29.57, with a critical micelle dilution (CMD⁻¹) and CMD⁻² of 41.77 and 68.92 mN/m, respectively. Sunflower oil gave the best results (29.75 mN/m) with a CMD⁻¹ and CMD⁻² of 36.69 and 51.41 mN/m, respectively. Sunflower oil contains about 60% of linoleic acid. The addition of linoleic acid decreased the surface tension from 53.70 to 28.39, with a CMD⁻¹ of 29.72 and CMD⁻² of 37.97, suggesting that this fatty acid stimulates the biosurfactant production by the LB006 strain. In addition, the crude precipitate surfactant reduced the surface tension of water from 72.00 to 28.70 mN/m. These results suggest that the sunflower oil’s linoleic acid was responsible for the increase in biosurfactant production by the LB006 strain.     

Optimization of Levan Production by Cold-Active <Emphasis Type="Italic">Bacillus licheniformis</Emphasis> ANT 179 and Fructooligosaccharide Synthesis by Its Levansucrase

Fructooligosaccharides (FOS) and levan attract much attention due to a wide range of applications in food technology and pharmaceutical and cosmetic industry. Bacillus licheniformis ANT 179, isolated from Antarctica soil, produced levansucrase and levan in a medium containing sucrose as carbon substrate. In this study, characterization of levansucrase and production of short-chain FOS and levan were investigated. Temperature and pH optimum of the enzyme were found to be 60 °C and pH 6.0, respectively. The optimization of fermentation conditions for levan production using sugarcane juice by response surface methodology (RSM) was carried out. Central composite rotatable design was used to study the main and the interactive effects of medium components: sugarcane juice and casein peptone concentration on levan production by the bacterium. The optimized medium with sugarcane juice at 20 % (v/v) and casein peptone at 2 % (w/v) was found to be optimal at an initial pH of 7.0 and incubation temperature of 35 °C for 48 h. Under these conditions, the maximum levan concentration was 50.25 g/L on wet weight basis and 16.35 g/L on dry weight basis. The produced inulin type FOS (kestose and neokestose) and levan were characterized by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (NMR) analysis. The study revealed that the levansucrase could form FOS from sucrose. The locally available low-cost substrate such as sugarcane juice in the form of a renewable substrate is proposed to be suitable even for scale-up production of enzyme and FOS for industrial applications. The levan and FOS synthesized by the bacterium are suitable for food applications and biomedical uses as the bacterium has GRAS status and devoid of endotoxin as compared to other Gram-negative bacteria.     

Production and Properties of a Surface-Active Lipopeptide Produced by a New Marine Brevibacterium luteolum Strain

Microbial-derived surfactants are molecules of great interest due to their environmentally friendly nature and low toxicity; however, their production cost is not competitive when compared to synthetics. Marine microorganisms are exposed to extremes of pressure, temperature, and salinity; hence, they can produce stable compounds under such conditions that are useful for industrial applications. A screening program to select marine bacteria able to produce biosurfactant using low-cost substrates (mineral oil, sucrose, soybean oil, and glycerol) was conducted. The selected bacterial strain showed potential to synthesize biosurfactants using mineral oil as carbon source and was identified as Brevibacterium luteolum. The surface-active compound reduced the surface tension of water to 27 mN m^?1 and the interfacial tension (water/hexadecane) to 0.84 mN m^?1 and showed a critical micelle concentration of 40 mg L^?1. The biosurfactant was stable over a range of temperature, pH, and salt concentration and the emulsification index (E₂₄) with different hydrocarbons ranging from 60 to 79 %. Structural characterization revealed that the biosurfactant has a lipopeptide nature. Sand washing removed 83 % of crude oil demonstrating the potential of the biosurfactants (BS) for bioremediation purposes. The new marine B. luteolum strain showed potential to produce high surface-active and stable molecule using a low-cost substrate.     

Production of a Bioemulsifier with Potential Application in the Food Industry

Biosurfactants are of considerable interest due to their biodegradability, low degree of toxicity, and diverse applications. However, the high production costs involved in the acquisition of biosurfactants underscore the need for optimization of the production process to enable viable application on an industrial scale. The aims of the present study were to select a species of Candida that produces a biosurfactant with the greatest emulsifying potential and to investigate the influence of components of the production medium and cultivation conditions. Candida utilis achieved the lowest surface tension (35.53 mN/m), best emulsification index (73 %), and highest yield (12.52 g/l) in a medium containing waste canola frying oil as the carbon source and ammonium nitrate as the nitrogen source. The best combination of medium components and cultivation conditions was 6 % (w/v) glucose, 6 % (w/v) waste canola frying oil, 0.2 % (w/v) ammonium nitrate, 0.3 % (w/v) yeast extract, 150 rpm, 1 % inoculum (w/v), and 88 h of fermentation. The greatest biosurfactant production and the lowest surface tension were achieved in the first 24 h of production, and the maximum biomass production was recorded at 72 h. The biosurfactant produced from C. utilis under the conditions investigated in the present study has a potential to be a bioemulsifier for application in the food industry.     

Synthesis,Characterization, and Oil Recovery Application of Biosurfactant Produced by Indigenous <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> WJ-1 Using Waste Vegetable Oils

A bacterial strain was isolated and cultured from the oil excavation areas in tropical zone in northern China. The biochemical characteristics and partial sequenced 16S rRNA gene of isolate, WJ-1, was identical to those of cultured representatives of the species Pseudomonas aeruginosa. This bacterium was able to produce a type of biosurfactant. Compositional analysis revealed that the extracted biosurfactant was composed of high percentage lipid (∼74%, w/w) and carbohydrate (∼20%, w/w) in addition to a minor fraction of protein (∼6%, w/w). The best production of 50.2 g/l was obtained when the cells were grown on minimal salt medium containing 6.0% (w/v) glucose and 0.75% (w/v) sodium nitrate supplemented with 0.1% (v/v) element solution at 37 °C and 180 rpm after 96 h. The optimum biosurfactant production pH value was found to be 6.0–8.0. The biosurfactant of WJ-1, with the critical micelle concentration of 0.014 g/L, could reduce surface tension to 24.5 mN/m and emulsified kerosene up to EI₂₄ ≈95. The results obtained from time course study indicated that the surface tension reduction and emulsification potential was increased in the same way to cell growth. However, maximum biosurfactant production occurred and established in the stationary growth phase (after 90 h). Thin layer chromatography, Fourier transform infrared spectrum, and mass spectrum analysis indicate the extracted biosurfactant was affiliated with rhamnolipid. The core holder flooding experiments demonstrated that the oil recovery efficiency of strain and its biosurfactant was 23.02% residual oil.     

Ethanol Production from Sugarcane Bagasse Hydrolysate Using Pichia stipitis

The objective of this study was to evaluate the ethanol production from the sugars contained in the sugarcane bagasse hemicellulosic hydrolysate with the yeast Pichia stipitis DSM 3651. The fermentations were carried out in 250-mL Erlenmeyers with 100 mL of medium incubated at 200 rpm and 30 °C for 120 h. The medium was composed by raw (non-detoxified) hydrolysate or by hydrolysates detoxified by pH alteration followed by active charcoal adsorption or by adsorption into ion-exchange resins, all of them supplemented with yeast extract (3 g/L), malt extract (3 g/L), and peptone (5 g/L). The initial concentration of cells was 3 g/L. According to the results, the detoxification procedures removed inhibitory compounds from the hemicellulosic hydrolysate and, thus, improved the bioconversion of the sugars into ethanol. The fermentation using the non-detoxified hydrolysate led to 4.9 g/L ethanol in 120 h, with a yield of 0.20 g/g and a productivity of 0.04 g L^?1 h^?1. The detoxification by pH alteration and active charcoal adsorption led to 6.1 g/L ethanol in 48 h, with a yield of 0.30 g/g and a productivity of 0.13 g L^?1 h^?1. The detoxification by adsorption into ion-exchange resins, in turn, provided 7.5 g/L ethanol in 48 h, with a yield of 0.30 g/g and a productivity of 0.16 g L^?1 h^?1.     

The Wettability Alteration and the Effect of Initial Rock Wettability on Oil Recovery in Surfactant-based Enhanced Oil Recovery Processes

Wettablity alteration of rock surface is an important mechanism for surfactant-based enhanced oil recovery (EOR) processes. Two salt and temperature-tolerant surfactant formulations were developed based on the conditions of high temperature (97–120°C) and high salinity (20 × 10⁴ mg/L) reservoirs where a surfactant-based EOR process is attempted. Both the two sufactant formulations can achieve ultralow interfacial tension level (≤10^?3 mN/m) with crude oil after aging for 125 days at reservoir conditions. Wettability alteration of core slices induced by the two surfactant formulations was evalutated by measuring contact angles. Core flooding experiments were carried out to study the influence of initial rock wettabilities on oil recovery in the crude oil/surfactant/formation water/rock system. The results indicated that the two formulations could turn oil-wet core slices into water-wet at 90–120°C and 20 × 10⁴ mg/L salinity, while the water-wet core slices retained their hydrophilic nature. The core flooding experiments showed that the water-wet cores could yield higher oil recovery compared with the oil-wet cores in water flooding, surfactant, and subsequent water flooding process. The two surfactant formulations could successfully yield additional oil recovery in both oil-wet and water-wet cores.     

Bioconversion of Sodium Dodecyl Sulphate to Rhamnolipid by Pseudomonas aeruginosa: A Novel and Cost-Effective Production Strategy

The utility of rhamnolipids in industry is currently limited due to the high constraints in its economic production. In this scenario, the novel utility of sodium dodecyl sulphate (SDS) as carbon source could serve as promising cost-effective strategy. Screening of effective SDS biodegraders led to the isolation of Pseudomonas aeruginosa S15 capable of concomitant SDS degradation and biosurfactant synthesis. SDS-based rhamnolipid production was proved on SDS minimal agar plates using cetyl trimethylammonium bromide–methylene blue method and optimised in SDS-based minimal salt (SBS) medium. SDS proved to be an ideal carbon source for rhamnolipid synthesis with a high substrate to product conversion rate yielding 6.9 g/l of rhamnolipids from 1 g/l SDS in 5 days. Fast atom bombardment mass spectroscopy analysis of the purified biosurfactant proved the presence of mono- and di-rhamnolipids, viz., Rha-C₁₀-C₁₀, Rha-C₁₀-C₁₂ and Rha-Rha-C₁₀-C₁₀ with surface active properties. The secreted rhamnolipids were not utilised by S15 as a carbon source, but it caused a dispersion of bacterial biofilms in SBS medium. To the best of our knowledge, this is the first report on bioconversion of synthetic detergent to biodetergent. This SDS-based novel methodology presents a more economised mode of rhamnolipid synthesis utilising SDS as sole carbon source.     

Biosurfactant production by Rhodococcus erythropolis grown on glycerol as sole carbon source

The production of biosurfactant by Rhodococcus erythropolis during the growth on glycerol was investigated. The process was carried out at 28°C in a 1.5-L bioreactor using glycerol as carbon source. The bioprocess was monitored through measurements of biosurfactant concentration and glycerol consumption. After 51 h of cultivation, 1.7 g/L of biosurfactant, surface, and interfacial tensions values (with n-hexadecane) of 43 and 15 mN/m, respectively, 67% of Emulsifying Index (E ₂₄), and 94% of oil removal were obtained. The use of glycerol rather than what happens with hydrophobic carbon source allowed the release of the biosurfactant, originally associated to the cell wall.     

Kinetics of thiophene hydrodesulfurization over a supported Mo–Co–Ni catalyst

In this study, the kinetics of thiophene (TH) hydrodesulfurization (HDS) over the Mo–Co–Ni-supported catalyst was investigated. Trimetallic catalyst was synthesized by pore volume impregnation and the metal loadings were 11.5 wt % Mo, 2 wt % Co, and 2 wt % Ni. A large surface area of 243 m²/g and a relatively large pore volume of 0.34 cm³/g for the fresh Mo–Co–Ni-supported catalyst indicate a good accessibility to the catalytic centers for the HDS reaction. The acid strength distribution of the fresh and spent catalysts, as well as for the support, was determined by thermal desorption of diethylamine (DEA) with increase in temperature from 20 to 600 °C. The weak acid centers are obtained within a temperature range between 160 and 300 °C, followed by medium acid sites up to 440 °C. The strong acid centers are revealed above 440 °C. We found a higher content of weak acid centers for fresh and spent catalysts as well as alumina as compared to medium and strong acid sites. The catalyst stability in terms of conversion as a function of time on stream in a fixed bed flow reactor was examined and almost no loss in the catalyst activity was observed. Consequently, this fact demonstrated superior activity of the Mo–Co–Ni-based catalyst for TH HDS. The activity tests by varying the temperature from 200 to 275 °C and pressure from 30 to 60 bar with various space velocities of 1–4 h^?1 were investigated. A Langmuir–Hinshelwood model was used to analyze the kinetic data and to derive activation energy and adsorption parameters for TH HDS. The effect of temperature, pressure, and liquid hourly space velocity on the TH HDS activity was studied.     

Pyrolysis of Eucalyptus wood in a fluidized-bed reactor

Eucalyptus wood can be utilized as a biomass feedstock for conversion to bio-oil using a pyrolysis process. Eucalyptus wood samples were initially pyrolyzed on a laboratory-scale pyrolysis system at different values in the ranges of 300–800 °C and 0.050–0.300 L min^?1 to determine the effects of operation temperature and N₂ flow rate, respectively, on the yields of products. Then, the bio-oil in the highest yield (wB = 44.37 %), which was obtained at pyrolysis final temperature (450 °C), heating rate (35 °C min^?1), particle size (850 μm), and sweeping flow rate (0.200 L min^?1), was characterized by Fourier transform infra-red spectroscopy, gas chromatography/mass spectrometry and column chromatography. Subsequently, it was shown that the operating temperature and N₂ gas flow rate parameters affected the product yields. Also, some important physico-chemical properties of the pyrolytic oil obtained in high yield were determined as a calorific value of 37.85 MJ kg^?1, an empirical formula of CH_1.651O_0.105N_0.042S_0.001, a rich chemical content containing many different chemical groups, a density of 981.48 kg m^?3, and a viscosity of 61.24 mm² s^?1. Based on the determined properties of the pyrolytic oil, it was concluded that the use of pyrolytic oil derived from Eucalyptus wood may be useful for the production of alternative liquid fuels and fine chemicals after the necessary improvements.     

Biosorption behaviors of uranium (VI) from aqueous solution by sunflower straw and insights of binding mechanism

Uranium (VI)-containing water has been recognized as a potential longer-term radiological health hazard. In this work, the sorptive potential of sunflower straw for U (VI) from aqueous solution was investigated in detail, including the effect of initial solution pH, adsorbent dosage, temperature, contact time and initial U (VI) concentration. A dose of 2.0 g L^?1 of sunflower straw in an initial U (VI) concentration of 20 mg L^?1 with an initial pH of 5.0 and a contact time of 10 h resulted in the maximum U (VI) uptake (about 6.96 mg g^?1) at 298 K. The isotherm adsorption data was modeled best by the nonlinear Langmuir–Freundlich equation. The equilibrium sorption capacity of sunflower straw was observed to be approximately seven times higher than that of coconut-shell activated carbon as 251.52 and 32.37 mg g^?1 under optimal conditions, respectively. The positive enthalpy and negative free energy suggested the endothermic and spontaneous nature of sorption, respectively. The kinetic data conformed successfully to the pseudo-second-order equation. Furthermore, energy dispersive X-ray, fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy demonstrated that U (VI) adsorption onto sunflower straw was predominantly controlled by ion exchange as well as complexation mechanism. The study revealed that sunflower straw could be exploited for uranium remediation of aqueous streams as a promising adsorbent.     

Pyrolysis of pine needles: effects of process parameters on products yield and analysis of products

Pyrolysis of pine needles was carried out in a semi-batch reactor. The effects of pyrolysis parameters such as temperature (350–650 °C), heating rate (10 and 50 °C min^?1), nitrogen flow rate (50–200 cm³ min^?1) and biomass particle size (0.25–1.7 mm) were examined on products yield. Maximum bio-oil yield of 43.76% was obtained at pyrolysis temperature of 550 °C with a heating rate of 50 °C min^?1, nitrogen flow rate of 100 cm³ min^?1 for biomass particle size of 0.6 < d _p < 1 mm. The characterization of pyrolysis products (bio-oil, bio-char) has been made through different instrumental methods like Fourier transform infrared spectroscopy, gas chromatography–mass spectrometry, nuclear magnetic resonance spectroscopy (¹H NMR), X-ray powder diffraction, field emission scanning electron microscope and Brunauer–Emmett–Teller surface area analysis. The empirical formula of the bio-oil and bio-char was found as CH_1.47O_0.36N_0.005 and CH_0.56O_0.28N_0.013 with heating value of 26.25 and 25.50 MJ kg^?1, respectively. Results show that bio-oil can be potentially valuable as a renewable fuel after upgrading and can be used as a feedstock for valuable chemicals production. The properties of bio-char reveal that it can be used as solid fuels, as a cheap adsorbent and as a feedstock for activated carbon production.     

Bioflocculant Exopolysaccharide Production by Azotobacter indicus Using Flower Extract of Madhuca latifolia L

Efficacy of Azotobacter indicus ATCC 9540 strain for production exopolysaccharide (EPS) bioflocculant was investigated. Mahua flower extract (Madhuca latifolia L), a natural substrate at the concentration of 20 g L^?1, gave maximum recovery of EPS followed by sucrose and mannitol as compared to other carbon sources after 172 h. Yeast extract was found to be the most effective nitrogen source as compared to beef extract, sodium nitrate, ammonium sulfate, casein hydrolysate, and urea for the production of EPS. EPS production was increased in presence of nitrogen (5.51 g L^?1) as compared to nitrogen-free medium (3.51 g L^?1), and fermentation time was also reduced by 28 h. Maximum EPS production (6.10 g L^?1) was found in the presence of 20 g L^?1 flower extract and 0.5 g L^?1 yeast extract containing Ashby’s media with 180 rpm at 30 °C at 144 h, under controlled conditions in 2.5 L fermenter using optimized medium. The isolated EPS showed cation-dependent flocculating activity. Concentration of EPS played an important role in bioflocculating activity which increased in a concentration-dependent manner up to a certain limit, with the maximum flocculation of 72% at 500 mg L^?1 concentration but remained almost static after this concentration. Extracted polymer was characterized by different chemical tests, FT-IR spectroscopy, and TLC which showed presence of uronic acids, O-acetyl groups, and Orcinol with suggestive indication of alginate like polymer. This study suggests that use of M. latifolia L. flowers can be a potential alternative bioresource for production of exopolysaccharide.     

Extraction of pertechnetates from HNO<Subscript>3</Subscript> solutions into ionic liquids

The effect of the oxidation temperature of sintered UO₂ pellets on the powder properties of U₃O₈ was studied in the temperature range 250–900 °C in air. The U₃O₈ was obtained at 450 °C after 180 min and its particle size and surface area are respectively, 35 µm and 0.7 m²/g. The reduction of the U₃O₈ powder resulted in UO₂ after 30 min with a surface area of 0.8 m²/g. This value was improved more than 3.5 times by applying five alternating oxidation–reduction cycles.     

Sorption study of uranium from aqueous solution on ordered mesoporous carbon CMK-3

The ability of ordered mesoporous carbon CMK-3 has been explored for the removal and recovery of uraium from aqueous solutions. The textural properties of CMK-3 were characterized using small-angle X-ray diffraction and N₂ adsorption–desorption, and the BET specific surface area, pore volume and the pore size were 1143.7 m²/g, 1.10 cm³/g and 3.4 nm. The influences of different experimental parameters such as solution pH, initial concentration, contact time, ionic strength and temperature on adsorption were investigated. The CMK-3 showed the highest uranium sorption capacity at initial pH of 6.0 and contact time of 35 min. Adsorption kinetics was better described by the pseudo-second-order model and adsorption process could be well defined by the Langmuir and Freundlich isotherm. The thermodynamic parameters, ?G°(298 K), ?H° and ?S° were determined to be ?7.7, 21.5 k J mol^?1 and 98.2 J mol^?1 K^?1, respectively, which demonstrated the sorption process of CMK-3 towards U(VI) was feasible, spontaneous and endothermic in nature. The adsorbed CMK-3 could be effectively regenerated by 0.05 mol/L HCl solution for the removal and recovery of U(VI). Complete removal (99.9 %) of U(VI) from 1.0 L industry wastewater containing 15.0 mg U(VI) ions was possible with 2.0 g CMK-3.