Molybdate Concentration Research Articles

Enhancing coated paper mechanical properties via doping kaolin with ammonium molybdate

Mechanical properties of paper coating layers are very important in converting and printing operations. Kaolin is commonly used in paper coating as cheap pigment in addition to its superior properties. In this study, a new approach for improving coated paper mechanical properties using doped kaolin with ammonium molybdate was presented. Kaolin and modified kaolin were characterized using several analyses tools (e.g., XRD, SEM, and EDX), and then they were applied in paper coating mixture. The results revealed that the dopant was found in the kaolin as MoOx; this oxide form with its needle shapes led to change in the kaolin crystals, and its presence in high concentrations led to exfoliation of kaolin. Also, at high concentration it was found that MoOx reacted with γ-alumina that is found in kaolin after its heating at 300°C to form aluminum molybdate. It can be observed that modified kaolin increased the coated paper porosity and consequently the opacity; also bulk and thickness were increased. Significant improvement in coated paper tensile strength, bursting strength, tensile energy absorption, and bending stiffness was also noticed. Thermal study also showed that increasing the concentration of ammonium molybdate increased the heat stability of the coated paper.

Differential influence of molybdenum and tungsten on the growth of barley seedlings and the activity of aldehyde oxidase under salinity

The influence of molybdenum, tungsten on germination and growth of barley Hordeum vulgare L. was studied. Results of this study revealed the differential effect of heavy metals on seedlings growth. Exogenous molybdenum treatment stimulated the growth of seedlings. The addition of the metal significantly stimulated root elongation. Contrastingly, the addition of tungsten resulted in increased seed germination and inhibits the growth of seedlings. The negative effect of tungsten on the growth of barley was more profound for roots of plants. In addition, the influence of metals on the growth of plants was also tested in saline conditions. It is shown that under salinity stress plant growth drastically decreased in presence of tungsten. Results of this study showed that activity of molybdenum-containing aldehyde oxidase (AO; EC 1.2.3.1) was also significantly affected by metals. The activity of AO in leaves and roots enhanced with increasing concentrations of molybdate, while tungstate treatment inhibited the enzyme activity. Perhaps, the differential influence of molybdenum and tungsten on the growth of barley is a direct effect of metals on aldehyde oxidase activity in plants. Moreover, the intense negative effect of tungsten treatment on barley growth under salinity conditions emphasizes an important role of aldehyde oxidase in plant resistance to stress factors.

In-situ construction of hierarchical CdS/MoS2 microboxes for enhanced visible-light photocatalytic H2 production

Exploration of highly active and noble-metal-free photocatalysts for high-efficiency photocatalytic water splitting is of great importance. Herein, a facile and effective in-situ hydrothermal method has been developed for preparation of CdS/MoS2 heterostructures with a unique hollow microbox morphology for visible-light-driven water splitting into H2. The influence of MoS2 is systematically investigated in terms of optical properties and photocatalytic activity of the CdS/MoS2 microboxes by varying the concentration of sodium molybdate. Under visible-light irradiation (λ ≥ 420 nm), the CdS/MoS2 microboxes exhibit superior photocatalytic H2 evolution activity (1.36 mmol/g/h) compared to pure CdS microboxes (0.04 mmol/g/h), corresponding to an apparent quantum yield of 14.5% at 420 nm. Photocatalytic mechanism study proves that the MoS2 nanosheets can serve as a co-catalyst and electron acceptor, for the effective promotion of electron transfer and separation of photogenerated charge carriers from CdS to further stimulate the surface H2 evolution kinetics. Furthermore, the well-defined interior voids, low density and shell permeability of the hierarchical CdS/MoS2 microboxes also contribute to the improvement of the photocatalytic performance.

The replacement of chromate by molybdate in phosphoric acid-based etch solutions for aluminium alloys

ABSTRACTCorrosion inhibition of aluminium alloys in the acidic solutions is important in the aluminium finishing industry (stripping solutions for anodic films). Sodium molybdate is a potential replacement for chromate-containing species used in the stripping solutions. It was tested as the corrosion inhibitor of 2024 aluminium alloy in orthophosphoric acid solutions. A corrosion rate of the alloy as a function of an initial concentration of sodium molybdate and temperature was determined by using gravimetric and gasometric methods. The corrosion rate was significantly lower in the solutions containing over 5 mM of sodium molybdate when compared to the uninhibited solution. The inhibition efficiency decreased with the increase of the temperature for the constant concentration of sodium molybdate. Sodium molybdate reduced the corrosion of the alloy by adsorption as well as formation of insoluble corrosion products on the alloy.

Characterisation of the simultaneous molybdenum reduction and glyphosate degradation by Burkholderia vietnamiensis AQ5-12 and Burkholderia sp. AQ5-13.

In this novel study, we report on the use of two molybdenum-reducing bacteria with the ability to utilise the herbicide glyphosate as the phosphorus source. The bacteria reduced sodium molybdate to molybdenum blue (Mo-blue), a colloidal and insoluble product, which is less toxic. The characterisation of the molybdenum-reducing bacteria was carried out using resting cells immersed in low-phosphate molybdenum media. Two glyphosate-degrading bacteria, namely Burkholderia vietnamiensis AQ5-12 and Burkholderia sp. AQ5-13, were able to use glyphosate as a phosphorous source to support molybdenum reduction to Mo-blue. The bacteria optimally reduced molybdenum between the pHs of 6.25 and 8. The optimum concentrations of molybdate for strain Burkholderia vietnamiensis strain AQ5-12 was observed to be between 40 and 60mM, while for Burkholderia sp. AQ5-13, the optimum molybdate concentration occurred between 40 and 50mM. Furthermore, 5mM of phosphate was seen as the optimum concentration supporting molybdenum reduction for both bacteria. The optimum temperature aiding Mo-blue formation ranged from 30 to 40°C for Burkholderia vietnamiensis strain AQ5-12, whereas for Burkholderia sp. AQ5-13, the range was from 35 to 40°C. Glucose was the best electron donor for supporting molybdate reduction, followed by sucrose, fructose and galactose for both strains. Ammonium sulphate was the best nitrogen source in supporting molybdenum reduction. Interestingly, increasing the glyphosate concentrations beyond 100 and 300ppm for Burkholderia vietnamiensis strain AQ5-12 and Burkholderia sp. AQ5-13, respectively, significantly inhibited molybdenum reduction. The ability of these bacteria to reduce molybdenum while degrading glyphosate is a useful process for the bioremediation of both toxicants.

Synthesizing Sodium Tungstate and Sodium Molybdate Microcapsules via Bacterial Mineral Excretion

We present a method, the bacterial mineral excretion (BME), for synthesizing two kinds of microcapsules, sodium tungstate and sodium molybdate, and the two metal oxides' corresponding nanoparticles—the former being as small as 22 nm and the latter 15 nm. We fed two strains of bacteria, Shewanella algae and Pandoraea sp., with various concentrations of tungstate or molybdate ions. The concentrations of tungstate and molybdate were adjusted to make microcapsules of different length-to-diameter ratios. We found that the higher the concentration the smaller the nanoparticles were. The nanoparticles came in with three length-to-diameter ratios: 10:1, 3:1 and 1:1, which were achieved by feeding the bacteria respectively with a low concentration, a medium concentration, and a high concentration. The images of the hollow microcapsules were taken via the scanning electron microsphere (SEM). Their crystal structures were verified by X-ray diffraction (XRD)—the crystal structure of molybdate microcapsules is Na2MoO4 and that of tungstate microcapsules is Na2WO4 with Na2W2O7. These syntheses all were accomplished under a near ambient condition.

Synthesizing Sodium Tungstate and Sodium Molybdate Microcapsules via Bacterial Mineral Excretion.

We present a method, the bacterial mineral excretion (BME), for synthesizing two kinds of microcapsules, sodium tungstate and sodium molybdate, and the two metal oxides' corresponding nanoparticles—the former being as small as 22 nm and the latter 15 nm. We fed two strains of bacteria, Shewanella algae and Pandoraea sp., with various concentrations of tungstate or molybdate ions. The concentrations of tungstate and molybdate were adjusted to make microcapsules of different length-to-diameter ratios. We found that the higher the concentration the smaller the nanoparticles were. The nanoparticles came in with three length-to-diameter ratios: 10:1, 3:1 and 1:1, which were achieved by feeding the bacteria respectively with a low concentration, a medium concentration, and a high concentration. The images of the hollow microcapsules were taken via the scanning electron microsphere (SEM). Their crystal structures were verified by X-ray diffraction (XRD)—the crystal structure of molybdate microcapsules is Na2MoO4 and that of tungstate microcapsules is Na2WO4 with Na2W2O7. These syntheses all were accomplished under a near ambient condition.

Reduction of Molybdenum by Pseudomonas aeruginosa strain KIK-11 Isolated from a Metal-contaminated Soil with Ability to Grow on Diesel and Sodium Dodecyl Sulphate

Recently, molybdenum is considered as an emerging pollutant for its extreme toxicity to spermatogenesis in some organisms. Bacterial molybdate reduction to colloidal molybdenum blue (Mo-blue) forms the basis for its bioremediation. Molybdenum-reducing Pseudomonas aeruginosa strain KIK-11 was screened for its potential to degrade hydrocarbons and detergents. Optimal molybdate reduction to Mo-blue in this strain was supported by pH between 5.8 and 6.0, temperatures between 25 and 34 oC, molybdate concentration between 30 and 40 mM and a critical phosphate concentration of between 5.0 and 7.5 mM. The isolate was able to survive and grow on SDS and diesel. However, these compounds did not support Mo-blue production. The best electron donor source facilitating molybdate reduction is glucose, followed by galactose, fructose and citrate respectively. The process was inhibited by heavy metals such as copper (II), mercury (II) and silver (I). The bacterium was able to grow and detoxify multiple toxicants, a novel feat that is important in bioremediation.

Isolation and characterization of a metal-reducing Pseudomonas sp. strain 135 with amide-degrading capability

The presence of both heavy metals and organic xenobiotic pollutants in a contaminated site justifies the application of either a multitude of microbial degraders or microorganisms having the capacity to detoxify a number of pollutants at the same time. Molybdenum is an essential heavy metal that is toxic to ruminants at a high level. Ruminants such as cow and goats experience severe hypocuprosis leading to scouring and death at a concentration as low as several parts per million. In this study, a molybdenum-reducing bacterium with amide-degrading capacity has been isolated from contaminated soils. The bacterium, using glucose as the best electron donor reduces molybdenum in the form of sodium molybdate to molybdenum blue. The maximal pH reduction occurs between 6.0 and 6.3, and the bacterium showed an excellent reduction in temperatures between 25 and 40 oC. The reduction was maximal at molybdate concentrations of between 15 and 25 mM. Molybdenum reduction incidentally was inhibited by several toxic heavy metals. Other carbon sources including toxic xenobiotics such as amides were screened for their ability to support molybdate reduction. Of all the amides, only acrylamide can support molybdenum reduction. The other amides; such as acetamide and propionamide can support growth. Analysis using phylogenetic analysis resulted in a tentative identification of the bacterium as Pseudomonas sp. strain 135. This bacterium is essential in remediating sites contaminated with molybdenum, especially in agricultural soil co-contaminated with acrylamide, a known soil stabilizer.

Isolation and characterisation of a Mo-reducing bacterium from Malaysian soil

The issue of heavy metal contamination and toxic xenobiotics has become a rapid global concern. This has ensured that the bioremediation of these toxicants, which are being carried out using novel microbes. A bacterium with the ability to reduce molybdenum has been isolated from contaminated soils and identified as Serratia marcescens strain DR.Y10. The bacterium reduced molybdenum (sodium molybdate) to molybdenum blue (Mo-blue) optimally at pHs of between 6.0 and 6.5 and temperatures between 30°C and 37°C. Glucose was the best electron donor for supporting molybdate reduction followed by sucrose, adonitol, mannose, maltose, mannitol glycerol, salicin, myo-inositol, sorbitol and trehalose in descending order. Other requirements include a phosphate concentration of 5 mM and a molybdate concentration of between 10 and 30 mM. The absorption spectrum of the Mo-blue produced was similar to the previously isolated Mo-reducing bacterium and closely resembles a reduced phosphomolybdate. Molybdenum reduction was inhibited by Hg (ii), Ag (i), Cu (ii), and Cr (vi) at 78.9, 69.2, 59.5 and 40.1%, respectively. We also screen for the ability of the bacterium to use various organic xenobiotics such as phenol, acrylamide, nicotinamide, acetamide, iodoacetamide, propionamide, acetamide, sodium dodecyl sulfate (SDS) and diesel as electron donor sources for aiding reduction. The bacterium was also able to grow using amides such as acrylamide, propionamide and acetamide without molybdenum reduction. The unique ability of the bacterium to detoxify many toxicants is much in demand, making this bacterium a vital means of bioremediation.

Medicago truncatula Molybdate Transporter type 1 (MtMOT1.3) is a plasma membrane molybdenum transporter required for nitrogenase activity in root nodules under molybdenum deficiency.

Molybdenum, as a component of the iron-molybdenum cofactor of nitrogenase, is essential for symbiotic nitrogen fixation. This nutrient has to be provided by the host plant through molybdate transporters. Members of the molybdate transporter family Molybdate Transporter type 1 (MOT1) were identified in the model legume Medicago truncatula and their expression in nodules was determined. Yeast toxicity assays, confocal microscopy, and phenotypical characterization of a Transposable Element from Nicotianatabacum (Tnt1) insertional mutant line were carried out in the one M.truncatula MOT1 family member specifically expressed in nodules. Among the five MOT1 members present in the M.truncatula genome, MtMOT1.3 is the only one uniquely expressed in nodules. MtMOT1.3 shows molybdate transport capabilities when expressed in yeast. Immunolocalization studies revealed that MtMOT1.3 is located in the plasma membrane of nodule cells. A mot1.3-1 knockout mutant showed impaired growth concomitant with a reduction of nitrogenase activity. This phenotype was rescued by increasing molybdate concentrations in the nutritive solution, or upon addition of an assimilable nitrogen source. Furthermore, mot1.3-1 plants transformed with a functional copy of MtMOT1.3 showed a wild-type-like phenotype. These data are consistent with a model in which MtMOT1.3 is responsible for introducing molybdate into nodule cells, which is later used to synthesize functional nitrogenase.

Effects of molybdenum on nutrition, quality, and flavour compounds of strawberry (Fragaria×ananassa Duch. cv. Akihime) fruit

Molybdenum (Mo) is an essential trace element in plant nutrition and physiology. It affects photosynthesis and photosynthate accumulation, therefore also affecting fruit quality and nutritional content. This study assessed the effects of different sodium molybdate (Na2MoO4) concentrations on strawberry. Five different Mo concentrations were applied in this experiment, including 0, 67.5, 135, 168.75, 202.5 g ha−1, respectively. The mineral concentration, including nitrogen (N), Mo, iron (Fe), copper (Cu), and selenium (Se) was assessed in strawberry fruit, as well as chlorophyll content, nutrition quality, taste and aroma. Results showed that net photosynthetic rate (Pn) and chlorophyll content for the strawberry plants increased with an increase in Mo concentration; and the contents of N, Mo, Fe, Cu, total soluble solids (TSS), titratable acidity (TA), sweetness, some sugars, organic acids, and some volatile compounds in the fruit all increased, as well. However, the Mo concentration did not significantly affect the concentrations of Se, sucrose, lactic acid, acetic acid, and some aroma compounds. Fruit sprayed with 135 g ha−1 Mo exhibited the highest TSS and sweetness values, as well as the highest N and Fe concentrations among all the treatments. Pn value and chlorophyll content, fructose, glucose, sorbitol and total sugar contents in fruit supplied with 135 g ha−1 Mo were also higher than that in other treatments. Fruit sprayed with a Mo concentration of 67.5 g ha−1 exhibited significantly higher ascorbic acid (AsA) values than that of control. Ninety-seven volatile compounds were identified in fruit extracted by head-space solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). Fruits sprayed with 135 g ha−1 Mo had the highest concentrations of six characteristic aroma compounds, including methyl butanoate, γ-decalactone, ethyl butanoate, methyl hexanoate, γ-dodecalactone, and ethyl caproate.

A novel method to synthesize molybdenum doped TiO2 films with enhanced photocatalytic activity

Micro arc oxidation method was utilized to prepare molybdenum doped TiO2 films through adding sodium molybdate into the electrolyte for the first time. The effect of sodium molybdate concentration on the morphology, crystal structure and photophysical properties of the films was investigated by field emission scanning electron microscopy, X-ray diffraction and UV–vis spectrophotometry. The results showed that with increasing of sodium molybdate concentration, the pores of films decreased in size and increased in number, more anatase phase transformed to rutile phase in the films and inter-plane spacing of the films increased. Furthermore, the absorption edges of the films shifted towards longer wavelength and the band gap energies of the films decreased with increasing the concentration of sodium molybdate. In addition, the photocatalytic degradation of methylene blue showed that the photocatalytic activity of the molybdenum doped TiO2 film was about 2.3 times that of pure TiO2 film.

Effects of Additives on the Electrodeposition of Nano-Grained Ni-Mo Alloys

Nano-grained (ng) materials have attracted much interest in the past few decades, as these materials are expected to have superior properties to their coarse-grained counterparts. Nevertheless, owing to the large fraction of grain boundary, the grain boundary energy becomes so high with the grain size down to a few nanometers that it is challenging to synthesize ng metals with extremely fine grain size. One possible way to do this is to prepare ng alloys instead of pure ng metals by choosing appropriate alloy systems with a tendency of segregation, as the segregation of solute atoms at grain boundaries will reduce grain boundary energy and thus stabilize the nanostructure. Electrodeposition has been found very promising in synthesis of ng metals, where additives are usually introduced to reduce grain size by moving the onset deposit potential negatively and consequent increasing the nucleation rate. In the electrodeposition of ng alloys, however, it is to be explored the effect of additives to the composition and the grain size of the synthesized ng alloy. It is the purpose of the present work to explore the effect of additives (saccharin and 1, 4-butynediol) in the synthesis of ng Ni-Mo alloy film in aqueous citrate-ammonia electrolyte with different concentration of sodium molybdate (Na2MoO4·H2O) ranging from 0.5 to 7 g/L. The chemical composition of ng deposits were determined by Energy-dispersive X-ray spectroscopy (EDS). The microstructure of the synthesized ng Ni-Mo films were characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM) with the grain size determined by TEM dark field images. Voltammetry was employed to evaluate the effect of additives and also sodium molybdate to the deposition of Ni-Mo. XRD results demonstrate that the as-deposited Ni-Mo films are all single fcc solid solutions. It is found Mo content in the deposits increases with the concentration of sodium molybdate in the electrolyte irrespective of the presence of additives. In addition, additives do not induce significant difference in the composition of the alloy deposits at a certain concentration of molybdate. The average grain size of the deposits decreases with the increase of sodium molybdate concentration from 44 nm to 5 nm corresponding to 0.5 g/L and 7g/L Na2MoO4·H2O respectively in plain solution, but the grain size reduces to 16 nm and 4 nm respectively in additives-added electrolyte corresponding to the same Na2MoO4·H2O concentration range. It is evident that saccharin and 1, 4-butynediol pronouncedly reduce the grain size of ng Ni-Mo when the Na2MoO4·H2O concentration is low but this reduction gradually gets small with the increase of molybdate concentration. Steady state polarization curves with the addition of additives and molybdate indicate an interaction between the saccharin, 1, 4-butynediol and the sodium molybdate, which correlates well with the composition and the characterized microstructure of ng Ni-Mo films.

Characterization of polyvinyl alcohol film doped with sodium molybdate as solid polymer electrolytes

In this paper, optical and electrical properties of solid films of polyvinyl alcohol (PVA) complexed with different concentration of sodium molybdate (Na2MoO4) have been analyzed. The shift and decrease in intensity of FTIR spectra of PVA doped with 9 wt.% of Na2MoO4 indicates the formation of charge-transfer complex between the cations of the sodium salt and the hydroxyl groups of PVA. The XRD results showed that the amorphous domains of PVA polymer matrix increased upon addition of Na2MoO4 salt. An increase of absorption and refractive index for solid electrolyte films has been observed. The decrease in optical band gap from 6.35 eV for pure PVA to 4.37 eV for PVA doped with 9 wt.% Na2MoO4 was observed. The results of electrical measurement showed that the conductivity increases as Na2MoO4 content increases. The DC conductivity of about 1.09 × 10− 6 S/cm was achieved for PVA incorporated with 9 wt.% Na2MoO4 salt. The AC conductivity spectra exhibit a dispersion manner at high frequencies. The behavior of the frequency exponent (s) with temperature was used to interpret the mechanism of ion transport. The variation of DC conductivity with temperature follows Arrhenius equation. The dielectric constant increased with increasing temperature and decreased with increasing frequency.

Molybdate in Rhizobial Seed-Coat Formulations Improves the Production and Nodulation of Alfalfa.

Rhizobia-legume symbiosis is the most well researched biological nitrogen fixation system. Coating legume seeds with rhizobia is now a recognized practical measure for improving the production of legume corp. However, the efficacy of some commercial rhizobia inoculants cannot be guaranteed in China due to the low rate of live rhizobia in these products. A greenhouse experiment was conducted to assess the effects of different rhizobial inoculant formulations on alfalfa productivity and nitrogen fixation. Two rhizobia strains, (ACCC17631 and ACCC17676), that are effective partners with alfalfa variety Zhongmu No. 1 were assessed with different concentrations of ammonium molybdate in seed-coat formulations with two different coating adhesives. Our study showed that the growth, nodulation, and nitrogen fixation ability of the plants inoculated with the ACCC17631 rhizobial strain were greatest when the ammonium molybdate application was0.2% of the formulation. An ammonium molybdate concentration of 0.1% was most beneficial to the growth of the plants inoculated with the ACCC17676 rhizobial strain. The sodium carboxymethyl cellulose and sodium alginate, used as coating adhesives, did not have a significant effect on alfalfa biomass and nitrogen fixation. However, the addition of skimmed milk to the adhesive improved nitrogenase activity. These results demonstrate that a new rhizobial seed-coat formulation benefitted alfalfa nodulation and yield.

Effect of a Mixture of Saccharin and 2-Butyne-1,4-diol on Electrodeposition of Nano-Grained Ni-Mo Alloys

Single face centered cubic (fcc) phase nano-grained Ni-Mo alloys were fabricated by electrodeposition in aqueous citrate-ammonia electrolytes with different concentration of sodium molybdate (0.5–7 g/L) with the addition of a mixture of saccharin and 2-butyne-1,4-diol. The effect of the additives mixture on the surface morphology and roughness, composition and grain size of nano-grained Ni-Mo deposits was investigated. It is demonstrated that this additives mixture effectively reduced surface roughness by eliminating bumps and tiny holes. Additionally, the additives mixture significantly reduced the grain size, especially when the concentration of sodium molybdate is low. The minimum grain size achieved with the presence of additives mixture is 4.4 nm with a Mo content of 18.7 at.%. Energy dispersive spectroscopy results indicated that the mixture of additives has little influence on the composition of the derived nano-grained Ni-Mo alloy. Steady state partial polarization together with chronopotentiometry were employed to evaluate the modification of additives to the cathodic process. It is exhibited that electrochemical behavior with the presence of additives correlates well with their effect on composition and grain size of nano-grained Ni-Mo alloys.

Inhibition of Bicarbonate-Chloride Corrosion and Passivation of Carbon Steel under Open-Circuit Conditions by Molybdate

Molybdate's inhibition of localized corrosion and passivation of AISI 1020 carbon steel in pH 9 and pH 10 solutions containing bicarbonate/carbonate and chloride anions was investigated under open-circuit conditions. The critical molybdate concentration required to prevent pitting corrosion in these solutions was determined. Using Design of Experiments and statistical analysis, the main and interaction effects of these anions on the polarization resistance were identified. Results show that the immersion time (a measure of the degree of passivation) and the presence of other ions can affect the effectiveness of a corrosion inhibitor. A combination of XPS and electrochemical methods was used to assess the effect of ions on the passive film formation. Increasing chloride concentration in the presence of bicarbonate/carbonate ions increased the total charge passed (extent of oxidation) but decreased the passive film thickness. This indicates that a significant part of the Fe atoms oxidized do not contribute to passive film formation, suggesting a harmful synergy between bicarbonate/carbonate and chloride. However, when molybdate is present, the total charge passed decreased and the passive film thickened slightly, showing the beneficial effect of molybdate on the passive film growth process, which is most probably due to competitive adsorption against bicarbonate/carbonate and chloride.

Isolation and Characterisation of a Molybdenum-reducing and Metanil Yellow Dye-decolourising Bacillus sp. strain Neni-10 in Soils from West Sumatera, Indonesia.

A molybdenum reducing bacterium with the novel ability to decolorise the azo dye Metanil Yellow is reported. Optimal conditions for molybdenum reduction were pH 6.3 and at 34°C. Glucose was the best electron donor. Another requirement includes a narrow phosphate concentration between 2.5 and 7.5 mM. A time profile of Mo-blue production shows a lag period of approximately 12 hours, a maximum amount of Mo-blue produced at a molybdate concentration of 20 mM, and a peak production at 52 h of incubation. The heavy metals mercury, silver, copper and chromium inhibited reduction by 91.9, 82.7, 45.5 and 17.4%, respectively. A complete decolourisation of the dye Metanil Yellow at 100 and 150 mg/L occurred at day three and day six of incubations, respectively. Higher concentrations show partial degradation, with an approximately 20% decolourisation observed at 400 mg/L. The bacterium is partially identified based on biochemical analysis as Bacillus sp. strain Neni-10. The absorption spectrum of the Mo-blue suggested the compound is a reduced phosphomolybdate. The isolation of this bacterium, which shows heavy metal reduction and dye-decolorising ability, is sought after, particularly for bioremediation.

ISOLATION AND CHARACTERIZATION OF A MOLYBDENUM-REDUCING AND PHENOLIC- AND CATECHOL-DEGRADING Enterobacter sp. STRAIN SAW-2

Molybdenum is an emerging pollutant worldwide. The objective of this study is to isolate molybdenum-reducing bacterium with the ability to grow on phenolic compounds (phenol and catechol). The screening process was carried out on a microplate. The bacterium reduced molybdenum in the form of sodium molybdate to molybdenum blue (Mo-blue). The bacterium required a narrow pH range for optimal reduction of molybdenum, i.e. between  pH 6.3 and 6.8, with temperature between 34 and 37 oC. Molybdate reduction to Mo-blue was best supported by glucose as the carbon source. However, both phenol and catechol could not support molybdate reduction. Other requirements for molybdate reduction included sodium molybdate concentrations between 15 and 30 mM, and phosphate concentration of 5.0 mM. The bacterium exhibited a Mo-blue absorption spectrum with a shoulder at 700 nm and a maximum peak near the infrared region at 865 nm. The Mo-reducing bacterium was partially identified as Enterobacter sp. strain Saw-2. The capability of this bacterium to grow on toxic phenolic compounds and to detoxify molybdenum made it a significant agent for bioremediation.