Ppm Of Molybdenum Research Articles

The effect of recycle stream on slurry-phase hydrocracking of vacuum residue: An experimental and modeling approach

The effect of the recycle stream on slurry-phase hydrocracking (HCK) of vacuum residue was examined using a continuous bench-scale unit with the aim of attaining process optimization. This was achieved through a model-based approach that links experimental investigations, kinetic modeling, and model-based optimization. The experiments were conducted at various reaction temperatures, liquid hourly space velocity of fresh feed (LHSVFF) and recycle ratios at a pressure of 160 bar, with the fresh feed containing 1000 wt. ppm of molybdenum. The HCK kinetic model was modified to incorporate the recycling effects and accurately predict the experimental data. The adapted model confirmed that the unconverted residue in recycle operating mode (ROM) became more refractory. By implementing the modified kinetic model in a dynamic Simulink model, the prediction accuracy of RES conversions and product yields can be improved by up to 25.1 wt.% in the case of the lowest conversion. A sensitivity analysis using the dynamic model showed that the temperature exerted a greater impact on the RES conversion and recycle ratio in ROM. An operational stability index was also proposed to prevent operation failure in ROM. Finally, an optimal operating condition from the parametric study was found to meet several process goals simultaneously.

ДО ПИТАННЯ ОНЛАЙНОВОГО МОНІТОРИНГУ ВМІСТУ МЕТАЛУ В РУДІ, ЯКА ВІДВАНТАЖУВАЮТЬСЯ КОПАЛЬНЯМИ НА ЗБАГАЧУВАЛЬНІ ФАБРИКИ ТОВ «КОМПАНІЯ КАЗАХМИС»

Purpose.Creating an effective system of online monitoring of ores sent to processing plants, focused not only on the profile element (copper), but also on related (silver, cadmium, molybdenum, arsenic) elements (the need to determine the content of silver and cadmium from 1+ ppm). Creating a procedure for the objective distribution of drain metal between mines. Methods. Study of the influence of numerous interfering factors on the test results of ores on the canvas of technological conveyors of concentrators of Kazakhmys Corporation LLC by X-ray fluorescence method (RFM) became EDXRF RKS RLP-21T determination of low content of silver and cadmium (1 + .ppm). The study was conducted in three stages. At the first stage, the following methods were developed: RKS calibration method, RKS measurement procedure, variable ore-RKS clearance method, RKS – Client ZhZF-1,2 system software for registration and display of RKS content data online. elements and the amount of metal in the railway warehouses of ore from mines and quarries and put into operation three RKS RLP-21T on ZHZF-1 2. In the second stage, four RKS RLP-21T were launched (BZF, KZF, NPR). At the third stage, RKS was launched at ZHZF-1.Аnd the basic principle was used in the research: the deposits are different – the RKS calibration method is the same for everyone. Results. The choice of X-ray fluorescent energy dispersion (EDXRF) ore control station (EDC) for online monitoring of metal content in ores on the canvases of technological conveyors of concentrators at ores size class -300 mm is substantiated. Scientific novelty. For the first time in Kazakhstan, on the scale of a huge mining enterprise Kazakhmys Corporation LLP, in practice, the task of online monitoring of the contents of the main (Cu, Pb, Zn) and accompanying (Ag, Cd, Mo) elements at low (1+ ppm) contents of silver, cadmium and 15+ ppm of molybdenum with an ore size of -300mm. For the first time in world practice, it has been proven that EDXRF RKS can provide online monitoring of complex composition copper-containing polymetallic ores for the content of not only basic, but also accompanying (silver, cadmium) components. For the first time in Kazakhstan on the scale of a huge mining enterprise LLC “Kazakhmys Corporation” in practice solved the problem of online monitoring of the content of basic (Cu, Pb, Zn) and related (Ag, Cd, Mo) elements at low contents of silver, cadmium (1+ ppm ) and molybdenum content (15+ ppm) at ore size -300mm. For the first time in world practice, it has been proven that EDXRF RKS can provide online monitoring of polymetallic ores containing copper for the content of not only basic but also related (silver, cadmium) components. Practical significance. Eight RKS RLP-21Ts were put into production. VTK wagon test points on cone crushers KKD 800/160 KD-1 ZHZF-1, KKD 1500/180 KD-2 ZHZF-1, KKD 1500/180 BZF were liquidated. The procedure of objective distribution of drain metal between mines has been established. Keywords: X-ray fluorescent energy dispersive method, ore control station, input process conveyors of concentration plants, online monitoring of the content of elements in ores.

PIXE Spectroscopy for Determination of Volatile Corrosion Inhibitor Concentration in Anticorrosion Polymer Films

Anti-corrosion polymer films used for 0 to 6 years were investigated to determine the type and content of volatile corrosion inhibitors (VCI) and how long the films emit it to protect the metal surface encased by the film. By FTIR and DSC low density polyethylene (LDPE) was identified as the polymer carrier. Particle induced X-ray emission (PIXE) spectroscopy of anti-corrosion polymer films revealed significant concentration of molybdenum implying that corrosion inhibitor was molybdate based. The films were divided into three groups according to different rate of the VCI concentration decrease with increasing age. The division of films into groups and diffusion of VCI was confirmed by significant decrease of Mo content determined by PIXE spectroscopy after accelerated ageing in vacuum at 50°C. It was concluded that films with initial concentration of Mo above 6000 ppm emit VCI for at least 6 years while the films with less than 4000 ppm of molybdenum do not emit the VCI in the ambient conditions.

Nitrogen metabolism in Nicotian a rustica L. grown with molybdenum. I. vegetative development

Abstract The effect of 1 ppm of molybdenum on nitrate reductase (EC 1.6.6.1.3) and nitrite reductase (EC 1.7.7.1) activity, and the nitrate, nitrite, ammonium, total nitrogen, total protein content on vegetative development of Nicotiana rustica L. was studied. This molybdenum supply increased the ammonium and nitrite content in leaves and the protein content in the root. Variations in enzymatic activity was not observed. The vegetative stage was shorter in the plants grown with this molybdenum supply.

Dithionite as a New Reductant in the Thiocyanate Method for the Spectrophotometric Determination of Molybdenum

Abstract Sodium dithionite has been recommended as a new reductant in the thiocyanate method for the spectrophotometric determination of molybdenum. The study is based on prior extraction of molybdenum(VI)–thiocyanate species in ethyl acetate from 0.8 mol dm−3 HCl medium followed by reduction of the complex with dithionite in the organic extract. The orange yellow color so obtained is measured at λmax 468 nm against a reagent blank. The 1 : 5 (Mo : SCN) complex is stable for 1 h in ethyl acetate and obeys Beer’s law over the concentration range 0—2.6 ppm of molybdenum (optimum range for accurate determination is 0.7—2.5 ppm). The molar absorptivity and Sandell sensitivity of the complex are 1.79 × 104 dm3 mol−1 cm−1 and 0.0053 μg Mo cm−2, respectively. The relative standard deviation for nine replicate determinations of 2 μg Mo cm−3 is ±1.1%. Of the tested 40 cations and 24 anions including complexing agents only thiourea interferes in the procedure. The method is sensitive and highly selective. It is applicable to the determination of molybdenum in steels and flue dust samples with satisfactory results.

Spectrophotometric Determination of Molybdenum in Some Alloys and Steels Using Quinalizarin and Cetylpyridinium Chloride

A new sensitive and rapid method is proposed for the spectrophotometric determination of molybdenum in some cobalt and nickel base alloys and steels. The procedure is based on the formation of a molybdenum(VI)-quinalizarin complex in an aqueous micellar solution of cetylpyridinium chloride (CPC) at pH 3.2-4.2. Beer′s law is obeyed over the range 0.05-0.60ppm of molybdenum. The apparent molar absorptivity of the complex is (1.27±0.01)×105l mol-1 cm-1 at 580nm and the sensitivity index is 0.0007μgcm-2 of molybdenum. The experimental factors which affect the color reaction were investigated throughly. The method is free of interference from most of the common metal ions.

Extraction and spectrophotometric determination of molybdenum(VI) with N-phenylbenzohydroxamic acid and phenylfluorone

N-Phenylbenzohydroxamic acid reacts with molybdenum(VI) in 3.5–6.0 M hydrochloric acid to give a complex that is extractable into chloroform. The chloroform extract of the molybdenum complex, on second extraction from a dilute hydrochloric acid medium (0.2–0.3 M) in the presence of phenylfluorone and ethanol, forms an intensely coloured complex possessing an absorption maximum at 518 nm. Job's method of continuous variation reveals that the complex is Mo(VI)—2NPBHA—PF. The molar absorptivity under optimum conditions is 7.4 × 104 cm3 mol−1 cm−1. The system obeys Beer's law up to 0.6 ppm of molybdenum(VI). Considerable amounts of many cations and anions can be tolerated. The interference from vanadium(IV) and vanadium(V) can be eliminated by the addition of sodium metabisulphite, whereas the interference from titanium(IV) is mitigated by oxalate ions. The method has been successfully applied for the determination of molybdenum in a standard steel sample.

Extraction spectrophotometric investigation of mixed ligand complex of molybdenum(V) with thiocyanate and 4-acetyl-2-(acetylamino)-5-dimethyl-?2-1,3,4-thiadiazole

A sensitive spectrophotometric method is developed for the determination of small amounts of molybdenum based on the extraction of molybdenum-thiocyanate-4-acetyl-2-(acetylamino)-5-dimethyl-Δ2-1,3,4-thiadiazole complex into chloroform from hydrochloric acid medium which is orange red in colour. The complex has an absorption maximum at 470 nm with a molar absorptivity of 2.01×104l·mole−1·cm−1. Beer's law is valid over the concentration range 0.06–2.5 ppm of molybdenum with an optimum concentration range of 0.15–2.2 ppm. The ternary complex is stable for over one week at room temperature. Equilibrium shift method indicates 1∶4∶2 composition for molybdenum-thio-cyanate-4-acetyl-2-(acetylamino)-5-dimethyl-Δ2-1,3,4-thiadiazole complex. The effects of acidity, reagent concentrations, time, temperature and diverse ions upon the absorbance of the complex are critically assessed. This method has been used successfully for the determination of molybdenum in molybdenum steels.

Extractive spectrophotometric determination of molybdenum(V) in molybdenum steels

An extraction spectrophotometric method has been developed for the determination of traces of molybdenum present in molybdenum steels which is based on the extraction of the orange-red molybdenum-thiocyanate-acetonethiosemicarbazone complex into chloroform from hydrochloric acid medium. The complex has an absorption maximum at 472 nm with a molar absorptivity of 1.9 × 10 4 liters mol −1 cm −1. Beer's law is valid over the concentration range 0.1–9.5 ppm of molybdenum with an optimum concentration range of 0.4–9 ppm. The equilibrium shift method indicates 1:4:2 composition for molybdenumthiocyanate-acetonethiosemicarbazone complex. The effect of acidity, reagent concentrations, temperature, and interferences from various ions are reported.

Extractive spectrophotometric determination of molybdenum as a thiocyanate-2-acetylpyridinethiosemicarbazone complex

A new spectrophotometric method for the determination of molybdenum is based on the extraction of the orange red molybdenum thiocyanate-2-acetylpyridinethiosemicarbazone complex into chloroform from hydrochloric acid. The complex has an absorption maximum at 470 nm with a molar absorptivity of 1.7 × 10 4 liters mol −1 cm −1. Beer's law is valid from 0.1 to 6.5 ppm of molybdenum. The equilibrium shift method indicated a 1:4:2 complex. The method has been used successfully for the determination of molybdenum in molybdenum steels.

Concentration and Spectrophotometric Determination of Molybdenum with Thiocyanate and Rhodamine 6G

Abstract A method is described for the determination of molybdenum based on reaction with potassium thiocyanate and Rhodamine 6G in 0.55–0.8 mol dm−3 hydrochloric acid medium. The method is sensitive (ε=2.63×105 l mol−1 cm−1) and obeys Beer’s law over the range 0.04–0.24 ppm of molybdenum. Selectivity can be considerably improved by collecting molybdenum on iron (III) hydroxide. In conjunction with the collection procedure, the method is useful to determine as low as 5 ppb of molybdenum present in 100 cm3 of aqueous samples.

Molecular Basis of the Biological Function of Molybdenum: EFFECT OF TUNGSTEN ON XANTHINE OXIDASE AND SULFITE OXIDASE IN THE RAT

Administration of tungsten to rats at levels of 1 to 100 ppm in the drinking water resulted in proportionate decreases in xanthine oxidase and sulfite oxidase activities and the native molybdenum electron paramagnetic resonance signal of the latter as well as total liver molybdenum. The time course of loss of the two enzyme activities fitted first order kinetics in all tissues studied. The t1/2 for sulfite oxidase activity was longer than that for xanthine oxidase in both liver and kidney, while both activities disappeared rapidly from intestinal tissue. The quantitative aspects of the biphasic loss of hepatic molybdenum revealed the existence of an unidentified and relatively unstable pool of molybdenum. This pool appeared to be replaced by tungsten early in the course of administration of the metal at 100 ppm. The simultaneous presence of 1 ppm of molybdenum almost completely superseded the effect of 100 ppm of tungsten. The results have been interpreted to indicate inhibition of molybdenum utilization by dietary tungsten. The tungsten effect was also observed when the metal was administered intraperitoneally. Injection of molybdenum into rats depleted of hepatic sulfite oxidase and xanthine oxidase activities by tungsten treatment resulted in significant restoration of both activities in 5½ hours. The use of cycloheximide and puromycin showed that the reactivation was independent of new protein synthesis. The inability to effect such reactivation in vitro points to the requirement for activation or modification of molybdate as a prerequisite for prosthetic attachment to the enzymes. Unlike tungsten, vanadium was incapable of generating experimental molybdenum deficiency in the rat.

Spectrophotometric determination of molybdenum(V) with oxine in aqueous pyridine solution

Molybdenum(V) and oxine formed a yellowish red colored complex having 1 : 1 molar ratio soluble 40 vol% pyridine solution. At its maximum absorption, 405 nm, the molar absorptivity was 4.4 × 103. The recommended procedure was as follows.Take the sample solution containing 0.020.6 mg of molybdenum and neutralize with 6 N sulfuric acid. Add 1 ml of 6 N sulfuric acid and 4 ml of 3% hydrazinesulfate solution, and heat the solution to ca. 1 ml. The reduction of molybdenum(VI) to molybdenum(V) occurred at this stage. Cool the solution, add 2 ml of 0.6% oxine solution and 10 ml of pyridine, and dilute to 25 ml with water. Measure the absorbance at 405nm against the reagent blank. Beer's law held for 0.824 ppm of molybdenum. Interference from tungsten was removed by measuring the absorbance at 405 nmand 450 nm. Since iron and copper etc. interfered with the determination of an extent of 0.7% molybdenum ion ores, molybdenum(V) was subjected to the spectrophotometric procedure by treatment with oxine and pyridine after the separation of precipitate as α-benzoinoximate from iron and copper etc. in sulfuric acidic solution.

The spectrophotometric determination of molybdenum and phosphorus by carminic acid method

A spectrophotometric method for the determination of molybdenum based on the use of carminic acid is proposed. Conformity to Beer's law was observed with an optimum concentration range of 1.5 to 8 ppm of molybdenum when absorbance measurements are made at 565 nm. The molar absorptivities for the determination of molybdenum are 1.4 × 10 4 mol l −1 cm −1 at 565 nm and 5.1 × 10 3 mol l −1 cm −1 at 336 nm. An indirect spectrophotometric procedure for the determination of orthophosphate based on the determination of the equivalent molybdenum in 12-molybdophosphoric acid was developed suitable for the determination of 0.03 to 0.18 ppm of phosphorus.

Micro Determination of Molybdenum (VI) with Phenylazoxine S Dye

Micro determination of molybdenum (VI) with 7-phenylazo-8-hydroxyquinoline-5-sulphonic acid is described. Molybdenum (VI) forms yellow, water souble complex in the pH range 2.5 — 5.5. 1:1 (M:L) stoichiometry has been established by (i) JOB’s and (ii) molar ratio methods. The colour reaction is instantaneous and the colour intensity remains unchanged for about 24 hours. The Beer's law is obeyed from 0.2 to 8.0 ppm of molybdenum per ml. The molecular extinction coefficient of the complex has been found to be E400 mµ =1.38 × 104, giving Sandell's sensitivity coefficient 0.0069 μg of molybdenum per cm2. The values of formation constant (log K) and free energy of formation (JF°) obtained by three methods are 5.40 ± 0.3. 5.20 ± 0.15, 5.62 ± 0.03 and (-7.50 ± 0.40, —7.22 ± 0.20, —7.80 ± 0.04 K.cals) respectively. The interference due to a number of anions and cations in the determination of molybdenum (VI) has also been studied. Azoxine S dyes having the general formula: (where R represents substituted benzene ring) have been found to form yellow, water soluble complexes with a number of metal ions. The dyes have been mainly used as metal ion indicators in recent years 1—5. However, a few physico-chemical studies on the complexation reactions of these dyes have also been reported 7—9. In the present investigations, a detailed study of molybdenum (VI) complex of the 7-phenylazo-8-hydroxy-quinoline-5-sulphonic acid has been carried out and it has been shown to form 1:1 complex in the pH range 2.5 to 5.5. The reaction is quite sensitive and can be used for the micro determination of molybdenum (VI).

Determination of Molybdenum in Fertilizers by Atomic Absorption Spectrophotometry

Abstract A procedure for determining low levels of molybdenum in fertilizers by atomic absorption is proposed. With potassium thiocyanate as complexing agent, molybdenum is extracted in an isoamyl alcohol fraction to separate the fraction containing molybdenum from the water-soluble fraction containing materials that would interfere in the atomic absorption procedure. However, the procedure cannot be used with samples that have high concentrations of iron. Tests on the recovery of molybdenum in four fertilizers indicate that the procedure is reliable to levels as low as 2.5 ppm of molybdenum

Copper, Sulfate and Molybdenum Interrelationships in Sheep

The experiment was designed to study the interrelationship of copper, molybdenum and sulfur in ruminant nutrition. Eighty lambs were used in the replicated, factorially arranged experiment, which involved 2 levels of copper (10 and 40 ppm), molybdenum (2 and 8 ppm), and sulfate-sulfur (0.10 and 0.40%). Response criteria were growth rate, hematology, and blood and liver mineral levels. Gain and efficiency were reduced by increasing the sulfur level in diets containing 2 ppm of molybdenum; however, this was not true when the diet contained 8 ppm of molybdenum, indicating that molybdenum alleviated the detrimental effects of sulfate. Hemoglobin concentration, erythrocyte counts and plasma protein, copper and calcium were not affected by treatments. Three-way interactions existed for hematocrit, plasma phosphorus and liver molybdenum. Hematocrit was lowered when sulfate-sulfur was increased from 0.10 to 0.40% except in the diet containing 10 ppm of copper and 8 ppm of molybdenum. Plasma phosphorus was also lowered by feeding 0.40% sulfate-sulfur except when 40 ppm of copper and 8 ppm of molybdenum were included in the diet. The three-way interaction for liver molybdenum was caused by decreases in liver molybdenum when 2 ppm of molybdenum and 10 or 40 ppm of copper were fed; feeding of 0.40% sulfate-sulfur, 8 ppm of molybdenum and 40 ppm of copper resulted in slightly higher final liver values, whereas high values were obtained for sheep fed 0.40% sulfur, 8 ppm of molybdenum and 10 ppm of copper. Liver copper was decreased by feeding 0.40% sulfate-sulfur or 8 ppm of molybdenum and increased by feeding 40 ppm of copper. Liver iron was increased as the sulfate-sulfur level was increased from 0.10 to 0.40%. Correlations among the plasma and liver values were also discussed.