Ferric Ions In Solution Research Articles

Iron Control Provides Sustained Production Increase In Wells Containing Sour Gas

Abstract Acid stimulation of wells containing hydrogen sulphide has in some cases resulted in short-lived production increases. The rapid decline in production has been thought to be related to reprecipitation of sulphur-containing species which reduce the flow of hydrocarbons when the well is placed on production. By using agents which interact with both iron ions in solution and hydrogen sulphide, precipitation of iron sulphide and elemental sulphur can be controlled and damage to the formation permeability can be reduced. The result of proper control of these sulphur-containing species is to provide the operator with sustained production increases after acidizing. This paper will discuss the mechanisms of damage, current iron control methods, solutions to the deficiencies 0f the currently used methods, and case histories showing use of improved methods of iron control in hydrogen sulphide environments. Introduction The use of acid to improve the production of hydrocarbons from subterranean formations as an effective method of stimulation was introduced in 1896(1). In these processes, acid was injected into the formation to dissolve the rock matrix to improve the now of hydrocarbons from the formation to the wellbore area for removal. Hydrochloric acid (HCl), an aggressive fluid, has many advantages which have resulted in its common use as a stimulation fluid. However, as such, an aggressive fluid does have some disadvantages. The major disadvantage pertinent to this paper is the high solubility in HCl solutions of iron containing minerals, many of which will reprecipitate when the acid content of the fluid decreases(2). Several methods have been used with success in controlling the repredpitation of iron in sweet wells. Some more commonly used materials have included buffering agents, chelating agents, reducing agents, and combinations of the above systems, These systems are designed to control the reprecipitation of ferric ions as hydrated ferric oxides. 'This ion has great solubility in fluids with pH values lower than about 2.5, but rapidly becomes insoluble in fluids with pH values above 2.5(3). This problem occurs because the normal pH of a spent acid fluid is about 4.0. Buffering agents can maintain a high acid content of the spent acid fluid at pH values below 2.5 for some time, and when used with chelating agents, have allowed spent acid fluids to retain high concentrations of ferric ion in solution(4,5). Reducing agents chemically convert ferric ion to ferrous ion(6,7,8). Ferrous ion does not precipitate at the pH of spent acid fluid. These systems have been shown to be effective in sweet wells; however, the problem becomes severe when sulphides are present. 'This is due to the failure of buffering systems, reducing agents, and some chelating agents to prevent the reprecipitation and reaction of iron solution species with hydrogen sulphide. Scale Sources The major source of possible damage to sour gas wells after acidizing is the reprecipitation of iron sulphide in the formation from the spent acid fluid. The source of this compound is from the redissolution, by the stimulation acid, of existing iron-containing sulphides on the tubular(9).

Synsedimentary volcanic-ash-derived illite tonsteins in Late Permian coal-bearing formations of southwestern China

Illite claystones (tonsteins) of Late permian coal-bearing formations are well developed and extensively distributed in southwestern China. Over the past decades it has been recognized that they are synsedimentary volcanic ash-falls in origin (altered tuff beds), based on the data derived from the comprehensive investigations on their stratigraphic and geographic distribution, petrographic types, chemical composition, accessory-mineral assemblage, as well as on their morphological characteristics. Recently, mineralogical and petrological identifications and X-ray diffraction analyses on these peculiar tonsteins further suggest that they can be classified mainly into three categories based on their clay-mineral constitution: kaolinitic, kaolinitic-illitic (transitional type), and illitic. As coal partings in most cases, these different types of tonsteins show a distinct zonal distribution on a regional scale. Their mineral constitution is profoundly modified by the combined effects of many factors during deuterogenic diagenesis, as indicated by the variation in volatile-component percentage (VM) of the adjacent coal seams (VM is calculated on a combustible-component basis). Those tonsteins intercalated in coal with a VM > 10% are dominated by kaolinite. But they contain increasing amount of illite at the expense of kaolinite when VM of coal decreases from 10% to 8%. When VM declines to less than 8% the clay minerals in these tonsteins are almost entirely illite with some sort of accompanying chloritization. It is clear that, from a regional point of view, the variation in clay-mineral constitution of these tonsteins is in response to the continual and progressive change in geological processes. In addition to the temperature and pressure conditions, the existence of a certain amount of alkali-metal ions and ferrous ions in solution is one of the controlling factors.

A phenomenological model of the bioleaching of complex sulfide ores

The leaching kinetics of a complex copper sulfide ore has been studied in laboratory-scale airlift percolators. Experiments were carried out to study the effect of a pure strain of Thiobacillus ferrooxidans on the dissolution rate of the different copper sulfide species contained in the ore. Comparison with the dissolution rate observed under sterile ferric ion solution conditions indicated that the catalytic role of bacteria was mainly related to the oxidation of ferrous to ferric ions in the leaching solution by bacteria, both adsorbed on the surface of the mineral particles and free in the leachingssolution. A phenomenological model was developed to account for the kinetics of the leaching process of complex ores in the percolator experiments. The model reproduces well the evolution in time of measured copper recovery, total iron concentration and bacteria in solution. A sensitivity study of the model parameters was performed to extend the results to the simulation of the overall kinetics of the process.

The dissolution of silver in ferric sulphate-sulphuric acid media

The dissolution of silver metal in ferric sulphate-sulphuric acid media was studied using the rotating disk technique. The effects of ferric ion, ferrous ion, acid, trace chloride ion, and total sulphate concentration as well as temperature, ionic strength and disk rotation speed on the silver dissolution rate were determined. The reaction rate is fast although its analysis is complicated by an apparent non-stoichiometric dissolution. Temperature studies at various ferric concentrations gave an activation energy of 28 kJ mol −1 and this value is typical of a reaction whose kinetics are fully or partially mass transport controlled. At ferric ion concentrations below 0.5 M, the rate depended upon the 0.65 power of the ferric ion concentrations whereas at higher concentrations, the rate was independent of ferric concentration but still was a function of the disk rotation speed. The reaction rate was simulated well at the lower ferric ion concentrations by the simple Levichtype laminar flow model and ferric ion diffusion rate control. Ferrous sulphate additions to the ferric ion solutions gave rate behaviour consistent with thermodynamic arguments based on the oxidative buffering effect of the ferric-ferrous couple. Sulphate added as sodium sulphate greatly reduced the silver dissolution rate but the slow reaction is nearly stoichiometric. Added perchlorate at equivalent ionic strength had no significant effect on the rate.

Prediction of redox potential in concentrated iron sulphate solutions

The technique involves the calculation of the concentrations of uncomplexed ferric and ferrous ions in solution, and of the concentrations of various iron-sulphate complex species. Thermodynamic stability constants of the various complex species are converted to concentration quotients at the actual ionic strength of the solution by means of activity coefficients for each species, which are calculated from the Debye-Hückel equation. The ratio of the activity of uncomplexed ferrous ions to that of uncomplexed ferric ions is then calculated from the ionic concentrations and activity coefficients, and this ratio is used in the Nernst equation for prediction of the redox potential of the solution. The results show that this technique gives reasonable predictions over a wide range of concentrations (up to ionic strengths of about 4) and temperatures (20 to 90°C).

Pseudomorphic replacement of manganese oxides by iron oxide minerals

Manganese oxide minerals containing structural Mn 4+ ions can act as oxidizing agents towards ferrous ions in solution. This oxidation causes the precipitation of Fe(III)-oxides in association with manganese oxide minerals, a probable mechanism for the natural formation of iron oxides in concretions and nodules in the subsurface horizons of soil, where transport of reduced iron takes place. The synthetic manganese oxide minerals todorokite and birnessite when exposed to ferrous ions caused a pseudomorphic precipitation of iron oxide minerals. The pseudomorphism was observed to be a macroscopic phenomenon; the iron oxide precipitate consisted of fine crystallites of feroxyhyte, lepidocrocite, or akaganeite in a loose mesh having the form of the original manganese oxide mineral. The anions present and the original structure of the manganese oxide mineral influenced the nature of the iron oxide formed. Reactions of ferrous sulfate (0.05 M) with Na-birnessite, todorokite or soil minerals containing birnessite and lithiophorite yielded sulfate-adsorbed-feroxyhyte as the major product. Reactions of ferrous perchlorate (0.05 M) with Na-birnessite yielded lepidocrocite and with todorokite yielded lepidocrocite and akaganeite. Reactions of ferrous chloride with birnessite or todorokite yielded akaganeite as the major phase. All iron oxides formed were poorly crystalline and contained adsorbed water.

Iron Control In Fracturing And Acidizing Operations

Abstract Investigative results from laboratory tests and field jobs show that iron presents a significant and complex problem in stimulation operations. Non-acidic or weakly acidic fracturing fluids are not detrimental from the aspect of dissolving and reprecipitating iron compounds. However, fracturing fluids usually contain a significant cancentration of dissolved and entrained oxygen which makes the fluid incompatible with formation water that contains ferrous ions in solution. The problem presented by an acidizing fluid differs from that presented by non-acidic or weakly acidic fracturing fluid. Acid dissolves iron compounds from equipment and flow lines as it is mixed and pumped to the formation. Acid may dissolve additional iron as it reacts with the formation. If acid does not contain an effective iron control system, dissolved iron precipitates. This precipitate may then accumulate as it is carried toward the wellbore during flowback. This accumulation of solids may plug natural and created permeability and have a detrimental effect on the recovery of the treating fluid and production. Chemicals and techniques that help ensure the compatibility of fracturing fluids and formation water are described. Iron control systems used in acidizing have properties that influence their effectiveness. The properties and effectiveness of the various systems are described so that a judicial selection of the most effective system can be made. Introduction Iron control problems are sometimes encountered when stimulating operations are conducted with weakly acidic or nonacidic fracturing fluids. The fracturing fluid ordinarily does not contain enough acid to dissolve iron and iron compounds from the well equipment or formation. Fracturing fluids, because of blending operations and viscosity of gelled fracturing fluids, will contain dissolved and entrained oxygen, which makes the fracturing fluid incompatible with formation waters that contain ferrous iron, Fe(2). The fracturing fluid mixes with the formation water. Oxygen in the fracturing fluid immediately oxidizes the ferrous iron, Fe (2), to ferric iron, Fe(3). The Fe(2) will remain in solution at pH levels up to about 7.5. The oxidation product, Fe(3), starts to precipitate at a pH of 2.5 and has completely precipitated when the pH reaches 3.5. The pH of the natural environment is usually greater than 3.5 and precipitation of Fe(3) occurs as the Fe(3) is formed by oxidation. Acidizing operations are usually conducted with highly acidic solutions. Acid corrosion inhibitors inhibit the reaction of acid on the metal contacted; however, they do not inhibit the reaction of the acid with iron compounds (rust, mill scale, siderite, and other iron compounds) to an appreciable extent. Acid dissolves these iron compounds as it is mixed and pumped through tubular goods to the formation. Iron content of the acid may possibly exceed 100 000 mg/I by the time it reaches the formation. This will depend on the condition of the pipe, the amount of pipe surface area contacted, concentration of acid used, and the temperature. Conditions may dictate a pre-clean job prior to the formation stimulation operation. This acid, containing iron in solution, flows into the formation, and dissolves additional iron before it is spent.

GTRC process for removing inorganic impurities from spent hydrodesulfurization catalysts

A method for removing nickel and vanadium contaminants from spent HDS catalysts involves pretreating the catalyst with H2S followed by extracting the metals with an acidic solution of ferric ion. The ferric ion solution alone removes significant amounts of active ingredients, cobalt and molybdenum; however, by pretreating with H2S, the extraction becomes more selective for removal of Ni and V.

Molecular dynamics study of raman scattering and infrared absorption of ferrous and ferric ions in aqueous solution

AbstractUsing a molecular dynamics computer model of water and ion water potentials we have used earlier to study electrolyte structure, we have calculated the infrared absorption and Raman scattering rates of ferrous and ferric ions in aqueous solution. Results for the Raman scattering from the ferric ion in solution are compared with experiments on molten Fe(NO3)3 · 28 H2O. The comparison suggests some new interpretations of the experiments.

Acidic rate- and flow-controlled dissolution of uraninite ores

A mathematical model is developed to calculate rates of uranium leaching as a function of flow rate and oxidant concentration for acidic solutions. The model is based on a simple plug-flow formulation for the conservation of mass and on experimental rate expressions for the aqueous oxidation of uraninite and pyrite by either ferric ion or hydrogen peroxide. Model calculations of oxidant and dissolved uranium concentrations are generally in good agreement with those measured in column experiments in which synthetic ores consisting of mixtures of uraninite, pyrite, and quartz sand were leached by dilute sulfuric acid solutions (pH = 1.7) that contained ferric ion or hydrogen peroxide as the oxidant. The experimental and modeling results show that uraninite is preferentially leached from pyritic ores by ferric ion solutions, but is less selectively leached by hydrogen peroxide. The calculated and measured rates of uranium leaching for pyritic ores indicate that it is most efficient to use high oxidant concentrations and high flow rates to take advantage of the more rapid reaction rates of uraninite with oxidant compared to reaction rates of pyrite with oxidant. At high flow rates, uranium extraction is maximized throughout a proportionately greater amount of ore before other competing reactions deplete the oxidant concentrations in the leaching solution.

Effects of pH and phosphate on the oxidation of iron in aqueous solution

Studies have been initiated to evaluate the catalytic effect of monohydrogen phosphate ions on the oxidation of ferrous (Fe 2+) to ferric (Fe 3+) ions in an aqueous solution under atmospheric oxygen conditions. The reactions were performed with an initial concentration of 1 × 10 −4 M ferrous sulfate in solutions containing varying concentrations of phosphate buffer (0.005–0.0175 M) over the pH range of 6.6–7.1. The final ionic strength of the solutions were adjusted to 0.1 M with sodium chloride and the temperature was kept constant at 25 ± 0.5 °C. The rates of oxidation reactions were measured by following the increase in UV absorbance due to the formation of ferric ion in solution. The reactions appeared to follow pseudo-first-order kinetics and were very prone to catalysis by monohydrogen phosphate at any given pH. H 2PO 4 − seemed to have no effect on the reaction. HPO s 2− was the sole catalytic species with a second-order rate constant of 116.74 M −1 · min −1. The buffer independent pH-rate profile showed a sigmoidal behavior with the pseudo-first-order rate constant increasing with increasing pH. The sigmoidal nature of the experimental pH-rate profile could possibly suggest a change in the reactivity of the oxidizing species which might follow complex kinetics. The effects of ionic strength and temperature on the reaction rates were also evaluated.

Application of optically transparent electrodes: Part III. A double-illumination-step chronoamperometric study of the kinetics of the dark back reaction of photochemically generated leucothionine with iron(III) in the iron-thionine system

Experimental transient photocurrent-time curves caused by a step-functional illumination through an optically transparent electrode (OTE) are compared with theoretical ones for the iron-thionine system. where not only can photochemically generated leucothionine be oxidized and consequently be monitored electrochemically at the OTE, but it can also be oxidized homogeneously with ferric ion in solution. It is also described how the rate constants of this dark back reaction in solution can be determined by double-illumination-step chronoamperometry. The second order rate constant for the reaction was determined to be 190±30 M −1 s −1 at 15±1°C

Determination of Oxydation Activity of Rice Root to Ferrous Solution

It is the purpose of this paper to establish a new method for the measurement of oxydation activity of rice root. After rice root was soaked in ferrous sulfate solution, the oxydation-reduction potential changed quickly. This change may be related to the increases of ferric ion in solution caused by oxydation activity of rice root. Eh-raising process was recorded continuously as shown in Fig. 1. Ageing process of rice root was expressed by the decreases of Eh-raising activity of rice root. Eh-raising activity of rice root of heavy nitrogen application plot decreased as shown in Fig. 4 in this studies. The drainage effect was shown in Fig. 5. Eh-raising activity of continuous paddy plot decreased remarkably at late maturing stage. The effect of pH control of ferrous solution on Eh-raising activity of rice root was shown in Fig. 3. At the unfavourable condition for rice growth as pH 4.4, Eh-raising activity of rice root decreased. From these results, the features of this method were in quick response and continuous recording of oxydation process by root. And the problems on the measuring were errors caused by the contamination of platinum electrode and reference electrode.

Effect of ferric ions on drag reduction effectiveness of polyacrylamide

AbstractThe drag reduction performance of polyaerylarnide polymers is severely degraded by the presence of ferric ions in solution. This effect has been noticed during the course of earlier experimental work and may have contributed greatly to poor reproducibility of results. The present work provides a more quantitative basis for estimating the effect of ferric ions on the drag reduction performance of polyacrylamide. Tests i a capillary‐tube rheometer and in a one‐in. pipe‐flow facility provide data for estimating the possible degradation effect o several different commercial polyacrylamides. In some case the degradation products deposit on the pipe wall, causing a increased roughness effect.

Determination of thiosulphate in urine.

A method is described for the determination of thiosulphate in urine. After removal of interfering compounds, including endogenous thiocyanate by ion exchange, thiosulphate is converted to thiocyanate in the presence of cyanide and cupric ions. The thiocyanate formed is concentrated by ion exchange, eluted with an acid solution of ferric ions and the ferric thiocyanate complex determined colorimetrically. Healthy human subjects excreted 31.7 +/- 12.8 mumol/24 h (mean +/- SD) thiosulphate.

Determination of thiosulphate in urine

A method is described for the determination of thiosulphate in urine. After removal of interfering compounds, including endogenous thiocyanate by ion exchange, thiosulphate is converted to thiocyanate in the presence of cyanide and cupric ions. The thiocyanate formed is concentrated by ion exchange, eluted with an acid solution of ferric ions and the ferric thiocyanate complex determined colorimetrically. Healthy human subjects excreted 31.7 ±12.8 μmol/24 h (mean ± SD) thiosulphate.

Effect of Dioxane Content and Resin Cross Linking on Uranium Isotope Separation by Inverse Break-Through Process

The effect of dioxane content and resin cross linking for uranium isotope separation by chemical and ion exchange has been studied, using an inverse break-through experiment, where the tetravalent uranium is oxidized and eluted with ferric ion solution. The separation factors decrease in presence of dioxane, since the change of the chemical processes predominates on the increase of ion association due to the lower polarity of the dioxane molecules. The low degree of the cross linking increases the equilibrium constants since the diffusion of the uranium species in the solid phase is faster, compared with the resin of higher cross linking.

銅‐亜鉛鉱の分離に対する問題点とその対策について

It is well known that the separation of copper and zinc minerals in the complex sulphide ores flotation is very difficult. On the other hand, it is also important to recover sphalerite entrained in the copper concentrate which is produced from the concentrators treating Cu-Pyrite ores and to recover chalcopyrite entrained in the zinc concentrate which is produced from the concentrators treating the Pb-Zn ores. Thus, the separation technique of Cu-Zn ores includes many difficult problems which have to improve.In this paper, the authors considered on many problems for the separation of Cu-Zn ores and discussed on how to separate the above minerals from the research works of the previous papers of the authors and others. There are many reasons why the separation of Cu-Zn ores is very difficult. One of them is the copper ions existing in the flotation pulp. Accordingly, the prevention and deactivation of the copper-activated sphalerite were discussed in order to separate the Cu-Zn ores.Among the previous research works which were carried out by the authors, the prevention and deactivation of copper activation for sphalerite were most effective by the use of sodium sulphide and ferric ion solution containing sulphuric acid. The effect of sodium sulphide on the prevention of copper activation for sphalerite was studied in the presence of sulphurous acid or sodium cyanide used as a depressant of sphalerite. From the results obtained, it may be considered that the copper activation of sphalerite is prevented perfectly by the use of sodium sulphide. Then the deactivation of the copper-activated sphalerite was investigated in a series of the laboratory experiments by the use of ferric ion solution containing sulphuric acid. From the results obtained, it was recognized that the deactivation of copper-activated sphalerite could be attained remarkably by the treatment of 980 mg/l Fe+++ solution containing over 4 vol. % of H2SO4. O2 gas accelerates the deactivation of the copper-activated sphalerite by the treatment of the above both solution. The temperature is one of the important factors for the deactivation. Using the flotation machine, the differential flotation test of Cu-Zn ore were carried out. The separation of Cu-Zn ore was successful by the deactivation treatment for Cu-Zn ore.From the recent paper by R. M. Manser and P. R. A. Andrews, a new reagent, Kr6D, as a depressant for sphalerite in a differential sulphide flotation stage was introduced in this paper. Small-scale laboratory flotation tests on such pure sulphide minerals as sphalerite and chacopyrite indicated that the Kr6D is capable of depressing sphalerite when used in small doses. At higher concentrations, chalcopyrite is also depressed. Single-stage batch-scale flotation tests were carried out on bulk concentrates containing the sulphide minerals. The Kr6D was compared with starch as a depressant both in the presence and in the absence of sulphur dioxide. In each case the new modifier was shown to be more effective.In addition to the above methods for the separation of Cu-Zn ores, the authors considered the possibility of improving selective flotation of bulk flotation concentrates from the previous papers of some other authors, including the abrasive action of high temperature and electric current for the adsorption collector layer on sphalerite and chalcopyrite. The desorption of collector layer on the Cu-Zn bulk concentrate by the use of sodium sulphide was discussed.

Characterization of hydrolyzed ferric ion solutions a comparison of the effects of various anions on the solutions

The spherical ferric-hydroxy polycations were isolated from a ferric nitrate solution. By adding nitrate or chloride ion to the isolated species, the subsequent aging processes could be modified. This provided evidence that the spherical polycations had a structure independent of the anion present during their formation, but subsequent aging processes were modified by the anion. The results of this study of the polycations was compared with earlier studies. Some disagreements were found and reasons advanced for them. Also the earlier results of this study involving ferric nitrate, perchlorate and chloride solutions have been compared and contrasted.

A study of chalcopyrite dissolution in acidic ferric nitrate by potentiometric titration

A pure chalcopyrite sample was studied using a potentiometric titration technique, which measures the oxidant consumption in the dissolution of sulphide mineral slurries in acidic ferric ion solutions. Rate measurements were made over a period of days at constant solution pH and oxidation potential at 25 and 40°C. Long term leaching followed the parabolic kinetics and dissolution stoichiometry previously described in the literature, but there was an initial reaction in which more iron than copper dissolved from the lattice and a metal-deficient “chalcopyrite-like” surface phase was rapidly formed. The subsequent dissolution reaction (observed specific reaction rate, s 0 = 1.4 × 10 −11 mol cm −2 s − 1 2 at 25°C; activation energy, E a = 14 kcal mol −1) was far more sensitive to temperature change and much slower than the rate of pore diffusion of oxidant ( s 0 ≈ 10 −7 mol cm −2 s − 1 2 , E a ≈ 2 kcal mol −1) and was interpreted in terms of a solid state diffusion step within the crystal lattice.