HEDTA Research Articles

Separation of rare earth elements using chelating agent-assisted electrodialysis: Phenomenological modeling and comparison with experimental data

The study presented here focuses on the development of a phenomenological model based on the Nernst-Planck equation for the separation of neodymium (Nd) and praseodymium (Pr) from a mixture containing cerium (Ce) and lanthanum (La) using chelated-assisted electrodialysis with hydroxyethylethylenediaminetriacetic acid (HEDTA) tri disodium salt as the chelating agent. This model considers solution selectivity, membrane selectivity, and ion migration within the membrane. The model is then used to study the optimal concentration of the chelating agent and pH conditions. It is demonstrated that the efficiency of the separation process could be enhanced through a multistage approach where the chelating agent concentration is maintained below the stoichiometric ratio of the elements to be masked. The model's predictive capabilities were evaluated by comparing its results with experimental data obtained at a HEDTA/Nd molar ratio of 1 and pH 3. The model showed an error of less than 26% for removal efficiency for all rare earth elements (REEs), and error values of 3% for purity and 9% for yield. These results indicate that the model can reasonably predict experimental outcomes with an acceptable level of accuracy. The developed model has the potential to be expanded for investigating chelation chemistry and electrodialysis operations involving various combinations of REEs and concentrations. It can be used to design experimental setups to study the effect of chelating agent to REE ratios and pH on key performance factors such as purity, yield, and separation factor. The versatility of the model makes it a valuable tool in the field of electrodialysis for the separation of rare earth metal ions using chelating agents.

Effect of Chelating Agents on Tight Sandstone Formation Mineralogy During Sandstone Acidizing

Dissolution of the wellbore damage is the main target of sandstone acidizing. The presence of minerals like clays, feldspar, zeolites, and alumino-silicates makes acidizing a challenging task because they may form undesired products (precipitates) when reacted with mud acid. Secondary and tertiary reactions are responsible for the formation of these products. To avoid the formation of precipitates, which are formed due to the reaction of conventional acids with minerals, chelating agents were utilized in this research paper. The chelating agents provide the advantage of deep penetration and slow reaction rate. The chelating agents HEDTA (hydroxyethylethylenediaminetriacetic acid), GLDA (tetrasodium glutamate diacetate), and EDTA (ethylethylenediaminetriacetic acid) were allowed to react with Colton sandstone formation under 1,000 psi confining pressure and 180°F temperature. The reacted core samples were tested for different analyses to analyze the effect of chelates on the core sample properties. The analyses performed are elemental analysis, mineral analysis, grain-size analysis, and porosity, particle, and density analysis. In elemental analysis, due to the tight nature of the Colton sandstone, the chelates were not that effective. From mineral analysis, HEDTA proved to be effective in the dissolution of quartz, ankerite, orthoclase, and calcite compared to GLDA and EDTA. According to a porosity analysis investigation, HEDTA produced the most additional pore spaces when reacted with the Colton sandstone formation.

A Comparative Experimental Study of Alternative Iron Sulfide Scale Dissolvers in the Presence of Oilfield Conditions and Evaluation of New Synergists to Aminopolycarboxylic Acids

SummaryIssues such as high corrosion rate, hydrogen sulfide (or H2S) generation, and scale reprecipitation have required the use of alternative dissolvers such as tetrakis(hydroxymethyl)phosphonium sulfate (THPS)–ammonium chloride (or NH4Cl) blend and chelating agents to dissolve iron sulfide (or FeS) scales. However, there are many aspects of these dissolvers that need investigation. This paper provides a guideline to select the best dissolver under various oilfield conditions by an extensive laboratory study. Furthermore, the iron sulfide scale removal is enhanced by the use of new synergists to the chelating agents.The application of THPS and diethylenetriaminepentaacetic acid (DTPA) in well tubulars or pipelines requires laboratory testing to determine the optimal conditions such as dissolver concentration, treatment time, and dissolver/scale (D/S) ratio (cm3/g) at 150°F. This evaluation considers oil-wet scales, mixed scales, presence of additives, and presence of salts during the treatment. Synergists such as potassium chloride (or KCl), potassium iodide (or KI), potassium formate (or HCOOK), sodium fluoride (or NaF), and potassium citrate (or K-Citrate) were added to ethylenediaminetetraacetic acid (EDTA), DTPA, and hydroxyethylethylenediaminetriacetic acid (HEDTA), and the scale solubility was evaluated at 150 and 300°F. Inductively coupled plasma–optical emission spectrometer analysis of the supernatant solution at various intervals of time up to 48 hours revealed the kinetics of the dissolution process. H2S generated from the scale dissolution process was measured using Draeger tubes. Corrosion tests helped in measuring the damage to the tubulars as a result of the dissolver’s contact with N-80 coupons.Solubility tests indicated the dissolver’s scale removal capacity at different concentrations. The work also accounted for the consumption of the dissolver for the scale removal. The optimal blend was chosen considering both the dissolution capacity and the dissolver consumption. For THPS–ammonium chloride blend, 0.75 mol/L THPS (30 wt%) and 2 mol/L NH4Cl (10 wt%) proved to be the optimum dissolver concentration at 150°F. Similarly, for DTPA, 0.4 mol/L K2-DTPA was evaluated to be the most effective dissolver concentration. The THPS–ammonium chloride blend was found to dissolve the iron sulfide slowly compared with K2-DTPA and 15% hydrochloric acid (HCl). The presence of crude oil on the scale hindered its solubility with K2-DTPA by 8%. The presence of calcium carbonate influenced higher selectivity of chelating the calcium ions by K2-DTPA. However, the overall fraction of scale removal was not affected. Adding corrosion inhibitors (CIs) did not affect the scale solubility significantly and also helped in maintaining an acceptable corrosion rate of N-80 coupons below 0.05 lb/ft2 at 150°F. The reaction of HCl and the iron sulfide scale generated 1,800 ppm of H2S in comparison with 0- and 10-ppm by THPS–ammonium chloride blend and K2-DTPA, respectively. Adding potassium iodide and potassium citrate to EDTA helped in improving the scale solubility at 150°F. Sodium fluoride improved the scale dissolution by EDTA and DTPA at 300°F.This paper addresses oilfield-like conditions on scale solubility by evaluating the role of mixed scale, scale mass, presence of hydrocarbons on the scale, and presence of monovalent/divalent ions in dissolver solution. A detailed and direct comparison of HCl, THPS–ammonium chloride blend, and DTPA in dissolving iron sulfide at various conditions enables easier selection of the dissolver for a field treatment. New synergists for iron sulfide scale dissolution are introduced in this paper. This work can help oilfield companies understand the nuances of applying different alternative iron sulfide dissolvers.

Masking Ability of Various Metal Complexing Ligands at 1.0 mM Concentrations on the Potentiometric Determination of Fluoride in Aqueous Samples.

Fluoride is a common anion present in natural waters. Among many analytical methods used for the quantification of fluoride in natural waters, potentiometric analysis is one of the most widely used methods because of minimum interferences from other ions commonly present in natural waters. The potentiometric analysis requires the use of ionic strength adjusting buffer abbreviated as TISAB to obtain accurate and reproducible data. In most of the reported literature, higher concentrations of strong metal chelating ligands are used as masking agents generally in the concentration range of 1.0 to 0.01 M. In the present study, effectiveness of the masking agents, phosphate, citrate, CDTA ((1,2-cyclohexylenedinitrilo)tetraacetic acid), EDTA (ethylenediaminetetraacetic acid) HE-EDTA ((hydroxyethyl)ethylenediaminetriacetic acid)), triethanolamine, and tartaric acid at 1.0 mM in TISAB solutions was investigated. The experimental data were compared with a commercially available WTW 140100 TISAB solution as the reference buffer. According to the experimental data, the reference buffer always produced the highest fluoride concentrations and the measured fluoride concentrations were in the range of 0.611 to 1.956 mg/L. Out of all the masking agents investigated, only CDTA performed marginally well and approximately a quarter of the samples produced statistically comparable data to the reference buffer. All the other masking agents produced significantly low concentrations compared to the reference buffer. The most probable reasons for the underestimation of fluoride concentrations could be shorter decomplexing time and lower masking agent concentrations.

Acidizing of conventional and tight sandstone formation using chelating agents: mineralogical prospect

Stimulation of the sandstone reservoir requires a mixture of acids such as mud acid, which assist in enlarging the microscopic paths by dissolving the siliceous fines or clays near the well-bore region. As a result, the formation permeability and porosity can be enhanced. In deeper wells, the temperature exceeds 200 °F, at these temperature ranges, problems can arise. For example, the use of mud acid mixtures can lead to issues like precipitations, corrosion, early consumption of acids, leading to lesser acid efficiency. In this study, the core flooding apparatus was used for acidizing experiments, designed to dissolve minerals and to analyze the changes in petrophysical parameters such as porosity, permeability, and mineralogy. Conventional and tight sandstone core samples were acidized using different chelating acids such as Hydroxyethylethylenediaminetriacetic acid (HEDTA), Ethylenediaminetetraacetic acid (EDTA) and Glutamic acid (GLDA) at high-temperature conditions. Analytical studies (mineral mass, pore size distribution, topology, grain size distribution, and density distribution were conducted using Tescan Integrated Mineral Analysis (TIMA). The obtained results showed that chelating agent HEDTA created more pore spaces in the core samples and is effective in dissolving positive ions. Also, the permeability was observed to be doubled by its application which could be effective in alteration of pore topology of the sandstone cores.

Evaluation of using HEDTA chelating agent to clean up long horizontal heterogeneous sandstone wells without divergent

The removal of the calcium carbonate water-based filter cake and the associated formation damage after drilling is a very difficult task, especially in horizontal and extended reach wells. The horizontal section length could be 20,000 ft or more with different permeability distributions, which makes the damage caused by the drilling fluid vary from one section to another. The filter cake removal in heterogeneous long horizontal lateral needs diverters to distribute the cleanup fluid through the entire section. In this paper, a smart fluid (HEDTA of 20 wt% and pH 4, hydroxyethyl ethylenediamine triacetic acid trisodium salt) was evaluated to remove the damage caused by calcium carbonate weighted drilling fluid for the horizontal and extended reach wells without adding gelling agents. This fluid will react with the calcium carbonate in the filter cake and the calcium carbonate in the formation to produce high viscosity fluid that will divert the fresh flow through the less permeable sections in the horizontal well. Parallel coreflooding experiments were used to confirm the diversion ability of this chemical through two sandstone cores with different permeability. The results obtained showed that the viscosity of the stimulation fluid increased at least 3 times after the treatment of the sandstone cores and the parallel coreflooding showed good ability of diversion for the fluid. The experimental results were used to describe the process of diversion using this fluid mathematically. HEDTA chelating agent showed good ability to remove the damage caused by drilling fluid from different sandstone cores with different permeabilities.

Corrosion Rates of Cr- and Ni-Based Alloys With Organic Acids and Chelating Agents Used in Stimulation of Deep Wells

SummaryAcid treatments of deep wells completed by use of chromium (Cr) -based tubulars represent a real challenge to the oil industry. On one hand, Cr-based tubulars are used to protect against carbon dioxide (CO2) corrosion, but on the other hand, the protective layer [chromium(III) oxide (Cr2O3)] dissolves in hydrochloric acid (HCl). This makes protection of Cr tubulars during acidizing very challenging, especially at high temperatures. At temperatures greater than 200°F, there is a need to add corrosion-inhibitor intensifiers, most of which depend on heavy metals [copper (Cu) or antimony (Sb)] or are not effective at temperatures greater than 300°F [e.g., potassium iodide (KI)].Over the last decade, a new chelant was developed, glutamic acid N, N-diacetic acid (GLDA), which can dissolve carbonate minerals from both carbonate and sandstone formations. This chelant can form wormholes in carbonates (both calcite and dolomite) and does not destabilize clay particles present in sandstone formations. In the present paper, the corrosion rate of GLDA solutions is compared with that of other chelants and simple organic acids that are used for carbonate dissolution, such as hydroxyethylethylenediaminetriacetic acid (HEDTA), acetic acid, and formic acid. All corrosion tests were conducted at high temperatures and pressures and extended for up to 6 hours at temperature and pressure. The Cr and nickel (Ni) -based coupons representing tubular metallurgy were examined thoroughly after the tests, and the spent fluids were analyzed for key cations [Cr, Ni, molybdenum (Mo), iron (Fe), and manganese (Mn)].Compared with formic acid, acetic acid, and even HEDTA, GLDA is much less corrosive to Cr-13 alloys. The results of this work show that GLDA at 20 wt% causes almost no corrosion with Cr-13 up to 300°F. Unlike GLDA, HEDTA was found to be corrosive at a pH = 3.8, and requires attention when used in wells completed with Cr-13-based tubulars. On more-corrosion-resistant Cr- or Cr-Ni-based alloys, such as super Cr-13, Duplex-2205, Inconel-625, and Incoloy-925, the corrosion rate of GLDA is still far below the acceptable limit of 0.02 to 0.05 lbm/ft2 up to 350°F. In wells with corrosive sweet and sour gases, tubulars consisting of low-carbon steel, Cr-based steel, or corrosion-resistant Cr-Ni alloys can be effectively protected by a combination of GLDA with a minimal amount of a suitable corrosion inhibitor. Because of its favorable environmental profile, this mixture meets all the Oslo-Paris Convention for the Protection of the Marine Environment of the Northeast Atlantic (OSPAR) requirements for use in the North Sea. On the basis of these results, GLDA solutions can be used to stimulate carbonate and sandstone wells completed with Cr- and Ni-based tubulars, while maintaining the integrity of the tubulars.

Using Synthetic Chelating Agents to Decrease Phosphorus Binding in Soils

Most acid soils have a high capacity to bind phosphorus (P) strongly on iron (Fe) and aluminum (Al) hydroxides, resulting in low P fertilizer use efficiency. Organic chelating agents form strong bonds with metals in soil and may reduce P binding with Fe and Al and increase fertilizer P use efficiency. Ethylenediamine tetraacetic acid (EDTA), hydroxyethyl ethylenediamine triacetic acid (HEEDTA), gluconic acid, and citric acid were tested to determine their influence on water-soluble P (WSP), Mehlich-1 P, and Mehlich-3 P in a loam and sand fertilized with P and incubated for 49 days. Soil P sorption capacity (PSC) was estimated from an oxalate extraction of Fe and Al, and chelates were applied at rates of 90% of the PSC. EDTA and HEEDTA were also applied at 0, 30, 60, 90, 120, and 150% PSC to produce a rate response curve for WSP in a second soil incubation. The EDTA, HEEDTA, and citric acid significantly (P < 0.05) reduced P sorption in the loam and sand when measured by WSP. In soils without P fertilizer added, EDTA and HEEDTA resulted in a significant increase in WSP concentrations, as well as increased concentrations of Mehlich-1 P and Mehlich-3 P. With increasing chelation rates of EDTA and HEEDTA, there was a linear increase in WSP for both soils, indicating higher rates were most effective at decreasing P sorption. The application of chelating agents, with and without P fertilizer, could potentially increase plant availability of P, therefore reducing P fertilizer.

Thermal Stability of Oilfield Aminopolycarboxylic Acids/Salts

Summary Chelating agents are used to remove various inorganic scales, including sulfates and carbonates. They are also used as standalone stimulation fluids and as iron-control agents during acidizing treatments. The main chelating agents used in the oil field include ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), N-(hydroxyethyl)-ethylenediaminetriacetic acid (HEDTA), and glutamic acid diacetic acid (GLDA). (Note that the abbreviations for these chelating agents will be used throughout the rest of the paper.) One of the concerns with these chelants is their thermal stability at elevated temperatures. Chelant solutions (0.7 to 0.8 M) of HEDTA, GLDA, NTA, EDTA, and their mono-/disalts were prepared. The aqueous solutions of these chelants were heated at various temperatures (300 to 400°F) and times (2 to 12 hours). The concentration of chelant was measured with a titration method that uses FeCl3 solutions. The products of thermal decomposition of chelants were determined with mass spectrometry (MS) and gas-chromatography/MS techniques. Most chelants decomposed at temperatures greater than 350°F. At 400°F and after 12 hours of heating, diammonium salt of GLDA degraded more quickly than diammonium salt of EDTA chelant. Analyses of NH4H3GLDA with MS techniques after heating highlighted that the decomposition products included iminodiacetic acid, hydroxyacetic acid, and α-hydroxyglutaric acid. Studying the kinetics of aqueous solutions of NaH3GLDA, NaH2HEDTA, and (NH4)2H2EDTA showed that their thermal-degradation kinetics followed a pseudofirst-order reaction. The Arrhenius equation can be used to predict the activation energy that is necessary for the degradation mechanisms of chelants.

Plant-Available Phosphorus after Application of Synthetic Chelating Agents

ABSTRACTFertilizer phosphorus (P) can become immobilized in acidic soils through bonds with iron (Fe) and aluminum (Al). Two chelating agents, ethylenediamine tetraacetic acid disodium salt (EDTA) and hydroxyethyl ethylenediamine triacetic acid (HEEDTA), were tested in a greenhouse study for efficiency at increasing plant-available P to corn (Zea mays L.). Fertilizer P was added with or without chelate to the center of pots, simulating a starter band of P. Without the presence of chelates, biomass above and below ground increased linearly as P fertilizer rates increased at 0, 9.6, 19.3, 28.9, and 38.5 kg P ha−1. Applications of EDTA and HEEDTA did not significantly increase water-soluble P (WSP), Mehlich 1 P, and Mehlich 3 P compared to soils without chelates. Applications of EDTA increased P uptake in the belowground biomass. Despite previous research showing that chelates increased WSP in soils, a decrease in P sorption was not observed with the additions of chelating agents to soils.

Chelating-Agent Enhanced Oil Recovery for Sandstone and Carbonate Reservoirs

Summary Recently low-salinity waterflooding was introduced as an effective enhanced-oil-recovery (EOR) method in sandstone and carbonate reservoirs. The recovery mechanisms that use low-salinity-water injection are still debatable. The suggested possible mechanisms are: wettability alteration, interfacial-tension (IFT) reduction, multi-ion exchange, and rock dissolution. In this paper, we introduce a new chemical EOR method for sandstone and carbonate reservoirs that will give better recovery than the low-salinity-water injection without treating or diluting seawater. In this study, we introduce a new chemical EOR method that uses chelating agents such as ethylenediaminetetraacetic acid (EDTA), hydroxyethylethylenediaminetriacetic acid (HEDTA), and diethylenetriaminepentaacetic acid (DTPA) at high pH values. This is the first time for use of chelating agents as standalone EOR fluids. Coreflood experiments, interfacial and surface tensions, and zeta-potential measurements are performed with DTPA, EDTA, and HEDTA chelating agents. The chelating-agent concentrations used in the study were prepared by diluting the initial concentration of 40 wt% with seawater and injecting it into Berea-sandstone and Indiana-limestone cores of a 6-in. length and a 1.5-in. diameter saturated with crude oil. The coreflooding experiments were performed at 100°C and a 1,000-psi backpressure. Low-salinity-water and seawater injections caused damage to the reservoir because of the calcium sulfate scale deposition during the flooding process. The newly introduced EOR method did not cause calcium sulfate precipitation, and the core permeability was not affected. The core permeability was measured after the flooding process, and the final permeability was higher than the initial permeability in the case of chelating-agent injection. The coreflooding effluent was analyzed for cations with the inductively coupled plasma (ICP) spectroscopy to explain the dissolution-recovery mechanism. The effect of iron minerals on the rock-surface charge was investigated through the measurements of zeta potential for different rocks containing different iron minerals. HEDTA and EDTA chelating agents at 5 wt% concentration prepared in seawater were able to recover more than 20% oil from the initial oil in place from sandstone and carbonate cores. ICP measurements supported the rock-dissolution mechanism because the calcium, magnesium, and iron concentrations in the effluent samples were more than those in the injected fluids. The IFT-reduction mechanism was confirmed by the low IFT values obtained in the case of chelating agents. The type and concentration of chelating agents affected the IFT value. Higher concentrations yielded lower IFT values because of the increase in carboxylic-group concentration. We found that the high-pH chelating agents increased the negative value of zeta potential, which will change the rock toward more water-wet.

Advanced TALSPEAK Separations Using a Malonate Buffer System

The extraction behavior of lanthanides and americium has been evaluated under Advanced TALSPEAK (Trivalent Actinide Lanthanide Separation by Phosphorus-reagent Extraction from Aqueous Komplexes) conditions using malonic acid as the aqueous buffering agent. The extractant 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) was used as an organic phase liquid cation exchanger in n-dodecane diluent, while N-(hydroxyethyl)-ethylenediaminetriacetic acid (HEDTA) served as a selective aqueous holdback reagent. Extractions conducted from malonate media exhibit a pH profile that flattens as the concentration of malonate is increased up to 1.0 M malonate. This relatively flat extraction behavior from pH 2.5–4.0 is reminiscent of previous studies on Advanced TALSPEAK in lactate media. The extraction kinetics with other carboxylic acid buffers as well as the effects of varying HEDTA, HEH[EHP], and malonate concentration are compared.

Influence of chelating therapy against aluminum chloride-induced immune suppression and hematological disorders in rabbits

This study aimed to evaluate the capability of chelating therapy in reducing the immunotoxic and hematotoxic effects induced by aluminum chloride (AlCl3). For this purpose, 40 male, adult, New Zealand white rabbits were divided into four groups with 10 animals each [control, AlCl3, and hydroxyethyl-ethylene diaminetriacetic acid (HEDTA) or Tiron plus AlCl3 groups]. Aluminum chloride administered via drinking water in a dose of 20 mg/l for 3 months. After that HEDTA or Tiron was administered i.p. at a dose of 50 and 471 mg/kg b.w., respectively, for 21 days, three times/week. Aluminum chloride-exposed rabbits showed a significant decrease in the number of red blood cells, blood hemoglobin concentration, and hematocrit value. Blood δ-aminolevulinic acid dehydratase activity and heme concentration showed a significant decrease than the control group. Serum IgA, IgG, and IgM levels were also significantly lower in AlCl3-exposed group than control. A prominent exhaustion of lymphoid elements of all investigated lymphoid organs was obtained. Histochemical enzymatic detection revealed weak positive nonspecific esterase or alkaline phosphatase staining reaction in macrophages, T and B lymphocytes, respectively, in AlCl3-exposed group in comparison of strong staining reaction in the control group. The present results indicated that long-term oral exposure to low doses of AlCl3 promotes alterations on hematological indices and some immune parameters in rabbits. In addition, most of the above parameters responded positively with Tiron or HEDTA chelating therapy but the effectiveness of Tiron therapy is more pronounced.

Evaluation of a New Environmentally Friendly Chelating Agent for High-Temperature Applications

Summary Matrix acidizing is used in carbonate formations to create wormholes that connect the formation to the wellbore. Hydrochloric acid (HCl), organic acids, or mixtures of these acids are typically used in matrix-acidizing treatments of carbonate reservoirs. However, the use of these acids in deep wells has some major drawbacks, including high and uncontrolled reaction rates and corrosion to well tubulars, especially those made of chromium-based tubulars (Cr-13 and duplex steel); and these problems become severe at high temperatures. To overcome problems associated with strong acids, chelating agents were introduced and used in the field. However, major concerns with most of these chemicals are their limited dissolving power and negative environmental impact. L-glutamic acid diacetic acid (GLDA), a newly developed environmentally friendly chelate, was examined as a replacement for acid treatments in deep oil and gas wells. The solubility of calcium carbonate (CaCO3) in the new chelate was measured over a wide range of parameters. Coreflood tests were conducted using long Indiana limestone cores 1.5 in. in diameter and 20 in. in length, which allowed better understanding of the propagation of this chemical in carbonate rocks. The cores were X-ray scanned before and after the injection of chelate solutions into the cores. The concentration of calcium (Ca) and chelate was measured in the core effluent samples. To the best of our knowledge, this is the first study to examine the fate and propagation of chelating agents in coreflood studies. GLDA has a very good ability to dissolve Ca from carbonate rocks over a wide pH range by a combination of acid dissolution and chelation. The addition of 5 wt% sodium chloride (NaCl) did not affect the GLDA performance at pH = 13 but significantly accelerated the reaction at pH = 1.7. Compared with other chelating agents, GLDA dissolved more Ca than ethanoldiglycinic acid (EDG) but less than hydroxyethyl ethylenediamine triacetic acid (HEDTA) at high pH values. GLDA of pH = 1.7 was able to form wormholes at 2 and 3 cm3/min. GLDA was found to be thermally stable at temperatures up to 350°F.

An Environmentally Friendly Stimulation Fluid for High-Temperature Applications

SummaryMatrix acidizing is used in carbonate formations to create flow channels from the formation to the wellbore; in sandstone formations, however, the goal is to dissolve materials that impair well performance. However, the use of acids in deep wells has some major drawbacks, including high reaction rate and corrosion to well tubulars.We have discovered a new stimulation chemical that can be used as a replacement for or in combination with acid treatments in deep wells. A polyacid whose structure allows for acidification is described. The polyacidic chelate L-glutamic acid, N, N-diacetic acid (GLDA) is manufactured from L-glutamic acid (MSG). The chelate-based fluid very effectively dissolves CaCO3, and it is less corrosive to the equipment and easy to handle.This paper discusses the reaction of the new chelate, GLDA, with calcite and compares its performance with other available chelates, including ethylenediaminetetraacetic acid (EDTA), hydroxy-ethylethylenediaminetriacetic acid (HEDTA), nitrilotriacetic acid (NTA), and ethanoldiglycine (EDG). GLDA dissolves calcite over a wide pH interval, although it is less effective than HEDTA at pH &amp;gt; 5. A unique property of GLDA is its high solubility; solutions exceeding 40 wt% can be achieved at a pH of approximately 2, whereas HEDTA solubility is limited to approximately 10 wt%. A mole of GLDA with a natural pH of approximately 1.5 is capable of dissolving up to two moles of CaCO3. Throughout the pH range, GLDA appears to be as thermally stable as HEDTA.As an additive to hydrochloric acid (HCl), GLDA is as effective as HEDTA in preventing precipitation of moderate levels of Fe3+ in spent acids. At high Fe3+ concentrations, GLDA is slightly less effective than HEDTA on a molar basis; but, to deal with high Fe3+ levels, GLDA may be better because significantly higher concentrations of it are possible in various acids. In 28 wt% HCl, HEDTA has limited solubility while GLDA's solubility exceeds 40 wt%.From an environmental standpoint, GLDA is readily biodegradable and is made from a renewable raw material, monosodium glutamate. GLDA has low toxicity and aquatic toxicity characteristics. As a replacement for HCl, GLDA is significantly safer and less corrosive.

High stability ferric chelates result in decreased iron uptake by the green alga Chlorella kessleri owing to decreased ferric reductase activity and chelation of ferrous iron

Cells of the green alga Chlorella kessleri Fott et Nováková use a reductive mechanism for iron acquisition. Iron-limited cells acquired iron more rapidly from a chelator with a lower stability constant for Fe3+ (hydroxyethylethylenediaminetriacetic acid (HEDTA)) than from a chelator with a higher stability constant (N,N′-di[2-hydroxybenzyl)ethylenediamine-N,N′-diacetic acid (HBED)). Furthermore, iron uptake rates decreased with increasing chelator concentrations at constant iron concentration. The negative effects of elevated HBED levels on iron uptake could be partly alleviated by the addition of Ga3+, which suggests that iron-free chelator has a negative effect on iron acquisition by competing for Fe2+ with the ferrous transport system. Furthermore, ferric reductase activity progressively decreased with increasing concentrations of both chelators (in the iron-free form). This effect was not alleviated by Ga3+ addition and was apparently caused by the direct inhibition of the reductase. Overall, we conclude that chelators with high stability constants for Fe3+ decrease iron acquisition rates by Strategy I organisms via three separate mechanisms.

The determination of the degree of zinc complexation by chelating agents with differential pulse voltammetry

The degree of zinc complexation was related to the type of the chelating agent and to the pH, whereas the stability of the zinc complexes was examined according to the chelating agents chosen from the group of aminopolycarboxylates. The degree of zinc complexation by the chelating compounds of the aminopolycarboxylates [ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), N-(hydroxyethyl)ethylenediaminetriacetic acid (HEEDTA), nitrilotriacetic acid (NTA), S,S-ethylenediaminedisuccinic acid (S,S-EDDS), methylglycinediacetic acid (MGDA), glutamic acid diacetic acid (GLDA)] in the environment of the supporting electrolyte was determined by differential pulse voltammetry using a mercury electrode operating in the SMDE mode. Reference electrode was silver-chloride electrode and auxiliary electrode was glassy carbon electrode. Voltammetric researches were carried out on the AUTOLAB PGSTAT 12 (Eco Chemie – The Netherlands) with GPES software with the use of mercury electrode 663 VA Stand (Metrohm – Swiss). The degree of zinc complexation increased with the increase in the concentration of the chelating agent and with the rise in the pH. Zinc complexes with EDTA, HEEDTA, DTPA and S,S-EDDS preserved their stability with time elapsed.

Confirmation of vanadium complex formation using electrospray mass spectrometry and determination of vanadium speciation by sample stacking capillary electrophoresis

Capillary zone electrophoresis (CZE) with UV detection was used to determine vanadium species. Nitrilotriacetic acid (NTA), hydroxyethylethylenediaminetriacetic acid (HEDTA), ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), ethylene glycol-bis(2-aminoethylether)-tetraacetic acid (EGTA) and 2,6-pyridinedicarboxylic acid (PDCA) were investigated to determine whether these ligands formed stable anionic complexes with vanadium. Of all the ligands studied HEDTA was the most suitable ligand because it gave the largest UV response with reasonable migration time. Electrospray mass spectrometry (ES-MS) was used to confirm the formation of [VO 2(HEDTA)] 2− and [VO(HEDTA)] 1− in solution. An electrolyte containing 25 mM phosphate, 0.25 mM tetradecyltrimethylammonium bromide (TTAB) at pH 5.5 was optimum for the separation of these anionic vanadium complexes. Sample stacking techniques, including large-volume sample stacking (LVSS) and field-amplified sample injection (FASI), were tested to improve the sensitivity. Best sensitivity was obtained using FASI, with detection limits of 0.001 μM, equivalent to 0.4 μg L −1, for [VO 2(HEDTA)] 2− and 0.01 μM, equivalent to 3.4 μg L −1 for [VO(HEDTA)] 1−. The utility of the method for the speciation of V(IV) and V(V) was demonstrated using ground water samples.

Differences between two green algae in biological availability of iron bound to strong chelators

N,N′-di(2-hydroxybenzoyl)-ethylenediamine-N,N′-diacetic acid (HBED) is a very strong Fe3+ chelator. Strategy I vascular plants, which use a reductive system for iron acquisition, similar to many green algae, are able to access iron from HBED (R.L. Chaney. 1988. J. Plant Nutr. 11: 1033–1050). However, iron-limited cells of the Strategy I green alga Chlamydomonas reinhardtii Dangeard were unable to access iron present as Fe3+–HBED. In contrast, Fe3+ chelated with hydroxyethylethylenediaminetriacetic acid (HEDTA; a weaker chelator) was rapidly taken up by iron-limited Chlamydomonas cells. Chlamydomonas ferric reduction rates with Fe3+–HBED were approximately 15% of the rate observed with Fe3+–HEDTA, suggesting that low reduction rates with Fe3+–HBED might be one factor in the low rate of iron acquisition. By contrast, iron-limited cells of the Strategy I green alga Chlorella kessleri Fott et Nováková were able to rapidly assimilate Fe3+ chelated by HBED, although ferric reduction rates with Fe3+–HBED were approximately 38% the rate of activity with Fe3+–HEDTA. Similar differential iron uptake rates for the two algal species were obtained using the strong Fe3+ chelator (and siderophore analogue) desferrioxamine B mesylate and the cyanobacterial siderophore schizokinen. These results suggest that there are differences among Strategy I green algae in their abilities to acquire Fe3+ from various ferric chelates: not all Strategy I algae can equally access tightly complexed Fe3+. Chlamydomonas appears to be the first documented Strategy I organism that is unable to acquire iron from Fe3+–HBED. These results also suggest that green algal iron acquisition from siderophores is species dependent. Finally, we suggest that iron acquisition from Fe3+–HBED might serve as an assay for an organisms’ ability to access tightly complexed iron.

Physiological responses of tomato roots grown in organ culture to iron-deficiency stress

Roots of the Fe-efficient tomato (Lycopersicon esculentum Mill., cultivar Floradel) were cultured in an inorganic medium supplemented with glycine, thiamine, pyridoxine, and nicotinic acid, with sucrose as an energy and carbon source. Iron was supplied as ferric hydroxyethylethylenediaminetriacetic acid (FeHEDTA) and the initial PH was 5.5. Root growth was limited when less than 40 μm FeHEDTA was supplied. Roots grown at lower Fe concentrations decreased the pH of the FCR assay medium to a greater extent than did roots grown at higher Fe concentrations. Cultured roots grown with 10 μm FeHEDTA had increased levels of ferric chelate reductase (FCR) activity compared to roots grown with either lower or higher concentrations of FeHEDTA. Low FCR activity of roots grown at 2.5 or 5 μm FeHEDTA was attributed either to impaired metabolism due to Fe-deficiency or the lack of sufficient Fe for enhanced FCR formation. Roots of hydroponically grown tomato plants exhibited typical increases in FCR activity with Fe-deficiency. Based on these preliminary results, cultured roots were found to exhibit similar Physiological responses to Fe-deficiency stress as intact root systems. Cultured roots should provide a useful system for the investigation of the role of the root in plant Fe-deficiency stress responses as previously suggested by Bienfait et al.(Plant Physiol., 83, 244–247, 1987).