Glutamic Diacetic Acid Research Articles

Experimental Investigations of Acid Fracturing in Layered Carbonate Rocks Utilizing Chelating Agents

One of the methods to improve carbonate formation productivity is acid fracturing. The acid injection creates dissolution along the fracture, which improves fracture conductivity. This study investigated chelating agents such as glutamic diacetic acid and ethylene diamine triacetic acid on acid fracturing treatments to sustain the conductivity of layered minerals of carbonate formations. Chelating agents are less reactive than HCl and do not need large quantities of corrosion inhibitors, especially in high-temperature environments. Three cylindrical samples of 1.5 in. × 6 in. were cored from casted layered calcite and dolomite. The roughness and hardness of the fracture surface before and after the stimulation have been examined. The fracture conductivity was also evaluated before and after acid etching using a core flooding setup at different flow rates under four closure stress values. Inductively coupled plasma analysis has been carried out to estimate rock dissolution based on quantifying calcium and magnesium ions. Results showed that chelating agents have improved fracture conductivity and resulted in a sufficiently rougher fracture surface compared to HCl. The rock samples’ surface hardness has been reduced relatively post-treatment, with chelating agents being gentler on the rock. The novelty of this study is that for the first time, chelating agents have been tested as acid fracturing fluids on carbonate reservoirs for generating sustainable conductivity.

Investigating Effects of Chelating Agents on Viscoelastic Surfactant Flooding at the Pore Scale Using Micromodels

Viscoelastic surfactants (VES) have proven their suitability for enhanced oil recovery (EOR) because they increase the viscosity and decrease the interfacial tension (IFT). In this work, we are proposing chelating agents to suppress the effect of salinity and maintain the required value to build the viscosity to optimize the amount of VES needed for a successful EOR job. Two different VES concentrations were investigated, 0.5 and 1.25 wt %. The chelating agents were diethylenetriaminepentaacetic acid (DTPA) and glutamic acid diacetic acid (GLDA), with different chelating agent concentrations ranging from 2 to 8% for each VES concentration. Rheology results showed that, for DTPA, the highest viscosity at the working shear rate of 1 s–1 is 717 cP achieved by 6% DTPA with 1.25% VES. While for GLDA, the highest viscosity at the working shear rate is 738 cP achieved by 8% GLDA with 1.25% VES. On the other hand, the IFT results for GLDA showed the lowest value of 0.0022 mN/m at 4% GLDA with 1.25% VES, and for DTPA, the lowest value was 0.0068 mN/m at 8% DTPA with 1.25% VES. The microfluidic recovery test was done for the selected best performance in IFT and rheology for each chelating agent with the pure VES. The ultimate recovery from 4% GLDA with 1.25% VES is 56% out of the original oil in place, while 43% using 8% DTPA with 1.25% VES. The pure VES at 1.25% gave 48% ultimate recovery. The chelating agent proved to be successful in suppressing the effect of salinity in reducing the IFT. Therefore, normal seawater without sweetening can be used with VES and GLDA and achieve promising recovery.

Impact of Chelating Agent Salt Type on the Enhanced Oil Recovery from Carbonate and Sandstone Reservoirs

In this paper, chelating agents were introduced as standalone fluids for enhancing the oil recovery from carbonate and sandstone reservoirs. Chelating agents such as glutamic acid di-acetic acid (GLDA), ethylene-diamine-tetra acetic acid (EDTA), and hydroxyl-ethylethylene-diamine-tri-acetic acid (HEDTA) were used. Chelating agents can be found in different forms such as sodium, potassium, or calcium salts. There is a significant gap in the literature about the influence of salt type on the hydrocarbon recovery from carbonate and sandstone reservoirs. In this study, the impact of the salt type of GLDA chelating agent on the oil recovery was investigated. Potassium-, sodium-, and calcium-based high-pH GLDA solutions were used. Coreflooding experiments were conducted at high-pressure high-temperature (HPHT) conditions using carbonate and sandstone cores. The used samples had porosity values of 15–18%, and permeability values were between 10 and 75 mD. Seawater was injected as a secondary recovery process. Thereafter, a GLDA solution was injected in tertiary mode, until no more oil was recovered. In addition to the recovery experiments, the collected effluent was analyzed for cations concentrations such as calcium, magnesium, and iron. Moreover, dynamic adsorption, interfacial tension, and contact angle measurements were conducted for the different forms of GLDA chelating agent solutions. The results of this study showed that incremental oil recovery between 19% and 32% of the Original Oil in Place (OOIP) can be achieved, based on the salt type and the rock lithology. Flooding carbonate rocks with the calcium-based GLDA chelating agent yielded the highest oil recovery (32% of OOIP), followed by that with potassium-based GLDA chelating agent, and the sodium-based GLDA chelating agent yielded the lowest oil recovery. The reason behind that was the adsorption of the calcium-based GLDA on the rock surface was the highest without reducing the rock permeability, which was indicated by the contact angle, dynamic adsorption, and flooding experiments. The outcome of this study will help in maximizing the oil recovery from carbonate and sandstone reservoirs by suggesting the most suitable salt type of chelating agents.

Anhydrite (Calcium Sulfate) Mineral as a Novel Weighting Material in Drilling Fluids

AbstractDifferent additives such as barite, calcium carbonate, hematite, and ilmenite having high-density and fine solid materials are used to increase the density of drilling fluids. However, some of the weighting additives can cause some serious drilling problems such as barite (particle settling, formation damage, erosion, and insoluble filter cake). In this study and for the first time, anhydrite (calcium sulfate) is used as a weighting additive in the drilling fluids. Several laboratory experiments such as density, rheology, fluid loss, resistivity, and pH were carried out to assess the performance of calcium sulfate as a weighting additive in the drilling fluids. The performance of calcium sulfate as a weighting additive was compared with the commonly used weight enhancing additive calcium carbonate. The results showed that calcium sulfate has higher solubility than calcium carbonate. The fluid loss test showed that both additives lost the same volume of fluid and created the same thickness of filter cake; however, the solubility of calcium sulfate-based filter cake with organic and inorganic acids was higher compared with other weighting materials. Calcium sulfate-based filter cake was completely dissolved using a new formulation that consists of glutamic-diacetic acid (GLDA) chelating agent and potassium carbonate as a convertor. The removal efficiency after 10 h reached 100% in 20 wt% GLDA and 10 wt% potassium carbonate solution at 100 °C.

Wire Electrochemical Micromachining of Aluminum Rings for the Fabrication of Short-Millimeter Corrugated Horns.

With the increase of working frequency, the feature size of a corrugated horn will be greatly reduced, causing challenges for fabrication. This paper investigated wire electrochemical micromachining (WECMM) of aluminum rings for assembly of a mandrel for electroforming, which has been a primary method for producing corrugated horns. By utilizing a rotary helical electrode and green additives, the removal efficiency of electrolytic products in WECMM was improved. It was found that the machined slits had good unilateral consistency on the left side of the electrode feeding direction when the electrode rotated clockwise. Complexing agent glutamic diacetic acid (GLDA) can compete with OH− for Al3+ and has an obvious effect in reducing insoluble electrolytic products. From experimental investigations on typical parameters, an optimal parameter combination considering slit homogeneity and machining efficiency was obtained. In an electrolyte solution containing 15 g/L sodium nitrate solution and 15 g/L GLDA, 100 μm-thick aluminum rings with good edge and surface qualities were fabricated at a rate of 1.2 μm/s using a helical electrode with a diameter of 0.3 mm. Finally, these aluminum rings were successfully applied to make an internal corrugated sample with a rib width of 100 μm and a groove depth of 500 μm.

Development of Chelating Agent-Based Polymeric Gel System for Hydraulic Fracturing

Hydraulic Fracturing is considered to be one of the most important stimulation methods. Hydraulic Fracturing is carried out by inducing fractures in the formation to create conductive pathways for the flow of hydrocarbon. The pathways are kept open either by using proppant or by etching the fracture surface using acids. A typical fracturing fluid usually consists of a gelling agent (polymers), cross-linkers, buffers, clay stabilizers, gel stabilizers, biocide, surfactants, and breakers mixed with fresh water. The numerous additives are used to prevent damage resulting from such operations, or better yet, enhancing it beyond just the aim of a fracturing operation. This study introduces a new smart fracturing fluid system that can be either used for proppant fracturing (high pH) or acid fracturing (low pH) operations in sandstone formations. The fluid system consists of glutamic acid diacetic acid (GLDA) that can replace several additives, such as cross-linker, breaker, biocide, and clay stabilizer. GLDA is also a surface-active fluid that will reduce the interfacial tension eliminating the water-blockage effect. GLDA is compatible and stable with sea water, which is advantageous over the typical fracturing fluid. It is also stable in high temperature reservoirs (up to 300 °F) and it is also environmentally friendly and readily biodegradable. The new fracturing fluid formulation can withstand up to 300 °F of formation temperature and is stable for about 6 h under high shearing rates (511 s−1). The new fracturing fluid formulation breaks on its own and the delay time or the breaking time can be controlled with the concentrations of the constituents of the fluid (GLDA or polymer). Coreflooding experiments were conducted using Scioto and Berea sandstone cores to evaluate the effectiveness of the developed fluid. The flooding experiments were in reasonable conformance with the rheological properties of the developed fluid regarding the thickening and breaking time, as well as yielding high return permeability.

Greener Chelators for Recovery of Metals and Other Applications

Classical chelating agents (especially aminopolycarboxylates, APCs and phosphonates) are till date the commonly used in industrial and home processes. This is due to their ability to strongly bind metals, and perhaps their being available in the market over a long time now. Abundant evidences proved that they are not environmentally benign. This has spurred the quest of industrialists and academia, as prompted by environmental policies, towards low toxicological profile and environmentally friendly chelating agents. The desire has resulted into annual rise in formulations and proposals of Greener alternative chelators such as glutamic diacetic acid (L-GLDA), ethylenediamine disuccinic acid [S, S]- EDDS, polyaspartic acid, citrate, gluconic acid, amino acids, lipophilic I²-diketone (14,16)-hentriacontanedione, plant extracts etc. to be used in place of the classical chelating agents. For reasons of environmental compatibility, low toxic profile and sustainability, these Greener alternative chelants are better employed for industrial uses (such as metals extraction and recovery etc.) and home applications.

Reaction of Chelating Agents with Guar Gum Polymer for Completion Fluid

Guar gum polymer is used extensively in the upstream applications such as hydraulic fracturing and gravel pack operations in unconsolidated sandstones. Guar gum will form a filter cake either on the fracture face or on the gravel, and this will affect the well productivity. There is an essential need to remove the filter cake formed by guar gum to enhance the well performance and enhance the oil and gas production rate. The reaction of guar gum with different chelating agents was assessed in this paper. Chelating agents like diethylenetriaminepentaacetic acid (DTPA), ethylenediaminetetraacetic acid (EDTA), and glutamic acid diacetic acid (GLDA) were used at different concentrations, temperature, time, and pH. An optimum formulation was developed to remove guar gum filter cake formed after gravel packing and hydraulic fracturing operations. Fourier transform infrared was used to explain the mechanism of the reaction between guar gum and chelating agents. It is the first time to assess the reaction between chelating agents and guar gum. The results obtained showed that the DTPA, EDTA, and GLDA highly affect the apparent viscosity of the guar gum solution (GG solution). Based on the experimental work, 20 wt% GLDA at pH 7 decreased the apparent viscosity of GG solution from 51 to 9 cP at a shear rate of 170.3 S\(^{-1 }\) after mixing for 24 h at \(200\,^{\circ }\hbox {F}\). The apparent viscosity of the GG solution decreased by 27% after mixing with 20 wt % EDTA (pH 12) at a shear rate of 170.3 S\(^{-1 }\) for 24 h at \(200\,^{\circ }\hbox {F}\). On the other hand, 20% DTPA at pH 4 and 7 at 170.3 S\(^{-1 }\)and \(200\,^{\circ }\hbox {F}\) did not reduce the GG solution apparent viscosity and based on that DTPA is not recommended for GG filter cake removal. The results of this research are very important for hydraulic fracturing operations to restore the fracture face permeability after filter cake removal. It will also open a research trend in the oil industry, especially in the fracturing and gravel packing operations.

Investigating the Compatibility of Enzyme with Chelating Agents for Calcium Carbonate Filter Cake Removal

Removal of water-based filter cake formed during drilling and hydraulic fracturing operations is a difficult task. Conventional acids, such as hydrochloric acid, organic acid, or a mixture of these acids, can be used to remove the filter cake. The common issues of these acids are rapid and uncontrolled reaction rate and corrosion to well tubulars, especially in horizontal and deep wells. Chelating agents were introduced in the oil industry to solve the problems associated with the conventional acids. Up to the authors’ knowledge, the reaction of chelating agents with starch, which is a major component of the filter cake, was not investigated in the literature. The objectives of this study are to (1) assess the reaction of starch with different chelating agents, namely ethylenediaminetetraacetic acid (EDTA), glutamic acid diacetic acid (GLDA), and diethylene triamine penta-acetic acid (DTPA), at different conditions of pH and temperature, (2) evaluate the compatibility of chelating agents with enzyme [high thermally stable $$\upalpha $$ -amylase enzymes (HTA)], (3) assess the reaction of enzyme with starch and xanthan gum, and (4) design the best scenario for calcium carbonate filter cake removal. The obtained results showed that EDTA (20 wt%, pH 7, and 12), DTPA (20 wt%, pH 7, and 12), and GLDA (20 wt%, pH 4, 7, and 12) were not able to break the starch after hot rolling for different time periods at $$200\,{^{\circ }}\hbox {F}$$ . Different chelating agents were found to be incompatible with $$\upalpha $$ -amylase enzyme (HTA enzyme that should be used to remove the starch). The two-stage scenario was found to be the best practice to remove the calcium carbonate filter cake in 22 h with 100% removal efficiency and 100% retained permeability. Computer tomography confirmed that external and internal filter cake was completely removed, and no formation damage was existing.

Evaluating the Chemical Reaction of Chelating Agents with Xanthan Gum

Xanthan gum is a polysaccharide natural polymer that is used heavily as a viscosifier in oil and gas industry especially with fracturing and gravel pack fluids. Numerous additives are required to control the properties of the fracturing and gravel pack fluids such as biocides, clay stabilizers, and some other additives to maintain the viscosity at high temperature during the fracturing operations. These additives have their limitations, and they will increase the cost of the operation. The objective of this research is to evaluate the chemical reaction of xanthan gum with different chelating agents [ethylenediaminetetraacetic acid (EDTA), glutamic acid diacetic acid (GLDA), and diethylenetriaminepentaacetic acid (DTPA)] at different conditions of pH, concentrations, temperature, and time to determine the optimum conditions for removing the polymer filter cake after fracturing and gravel pack operations . The results obtained showed that mixing chelating agents (DTPA, EDTA, and GLDA) with xanthan gum had a big effect of increasing the viscosity of the solution. DTPA and EDTA at different pH and shear rates over long time (36 h) did not break the XC-polymer solution at \(200~^{\circ }\hbox {F}\). GLDA (20 wt%, pH 12) increased the viscosity of the xanthan gum solution from 33 to 45 cP for 11 h at \(200~^{\circ }\hbox {F}\) and a shear rate of \(170.3\, \hbox {S}^{-1}\). Under the same conditions, GLDA worked as a breaker after 11 h as the apparent viscosity of the GLDA-XC solution was decreased from 45 cP to 11 and 3 cP after 24 and 36 h, respectively. The optimum concentration of GLDA was found to be 20 wt%, and the optimum pH was found to be 12.

Stimulation of Seawater Injectors by GLDA (Glutamic-Di Acetic Acid)

Summary Seawater is injected to maintain the reservoir pressure that supports the oil production from carbonate and sandstone reservoirs. In certain regions, the seawater contains more than 4,000 ppm sulfate, and the formation contains more than 19,000 ppm calcium; this will cause calcium sulfate precipitation at the reservoir conditions. The precipitate at the reservoir conditions will be anhydrite, and it will cause formation damage that will reduce the well injectivity. Stimulation treatments are required to recover the well injectivity; this requires stopping water injection to perform the stimulation treatments, and also it requires flowing back the well after stimulation treatment. In this study, we are proposing a new method that we can use to stimulate water injectors without stopping the water injection. The new method includes adding a chelating agent to the injected seawater at the wellhead at 15 wt% concentration. The fluid will be injected at the surface with the seawater with a specific dose to achieve the required concentration. Several solubility and coreflooding tests were performed with actual carbonate cores and GLDA (glutamic-di acetic acid) chelating agent at different temperatures. The chemical injection does not need coiled tubing and can be injected at the surface with the seawater. The chelating agents will sequester all calcium in solution and will prevent the calcium sulfate precipitation. GLDA chelating agent will be used with seawater, with no need to use treated or fresh water. Also, flowing back the well is not required because the fate of GLDA in the aquifer is soluble. Solubility tests up to 250°F at high pressure showed that the GLDA is stable with seawater. Coreflood experiments and computed-tomography scans showed the ability of GLDA in the creation of dominant wormholes through 6- and 1.5-in. carbonate cores at 212 and 150°F, respectively. GLDA chelating agent can be used to stimulate seawater injectors without additives because this chemical is stable and mild with the well tubulars. Previous corrosion studies on GLDA showed that its corrosion rate is in the allowable range without adding corrosion inhibitors.

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.

Effect of Sand Content on the Filter Cake Properties and Removal During Drilling Maximum Reservoir Contact Wells in Sandstone Reservoir

The drilling mud program contains many tests such as filtration rate and filter cake properties to select the proper drilling fluid additives that yield the standard ranges of the viscosity, filtration rate, etc. However, the physical and chemical changes in the mud composition during the mud circulating will cause changes to the filter cake properties. The changes in the filter cake properties should be considered in the mud design program to prevent the problems associated with the change in the drilling fluid properties. For long horizontal wellbores penetrating plastic formations, the two sources of solids in filter cake are drilling chemical additives and formation cuttings (sand particles in the case of sandstone reservoir). This study focuses on the effect of introducing sand particles from the drilled—formations on the filter cake properties. Real drilling fluid samples from the field were collected at different location during drilling a 3600 ft of the horizontal section of a sandstone formation. Calcium Carbonate (CaCO3) was used as weighting material in this filed. The drilling fluid samples were collected at two different points: the flow line coming from the well after shale shaker and the flow line going to the well to verify the effect of separation stages on filter cake properties. The primary drilling fluid properties of the collected samples were measured such as density and rheological parameters. High pressure high temperature (HPHT) filter press was used to perform the filtration and filter cake experiments at 300 psi differential pressure and room temperature (25 °C). The mineralogy of the external filter cake formed by fluid loss cell is determined using SEM (scanning electron microscopy) and XRD (X-ray diffraction). Finally, solubility test was conducted to evaluate the effect of sand particles on filter cake removal (containing Calcium Carbonate as weighting material) using chelating agent: glutamic diacetic acid (GLDA) at pH 4. The results showed that for long horizontal sections, the effect of introducing sand particles to the composition of the filter cake can cause significant change to the properties of filter cake such as mineralogy, thickness, porosity, and permeability. For instant the thickness of filter cake increased about 40% of its original thickness when drilling sandstone formation in horizontal well due to fine sand particle settling. The filter cake porosity and permeability increment in the first 2000 ft part of the horizontal section was observed clearly due to the irregular shape of the drilling particles. However for the points after the first 2000 ft of horizontal lateral, the porosity and permeability almost remained constant. Increasing the sand content up to 20% degrade the dissolution rate of calcium carbonate in the GLDA (pH = 3.8) to 80% instead of 100%.

Field Treatment To Stimulate a Deep, Sour, Tight-Gas Well Using a New, Low-Corrosion and Environmentally Friendly Fluid

Summary Matrix acidizing of high-temperature gas wells is a difficult task, especially if these wells are sour or if they are completed with high-chrome-content tubulars. These harsh conditions require high loadings of corrosion inhibitors and intensifiers in addition to hydrogen sulfide scavengers and iron control agents. Selection of these chemicals to meet the strict environmental regulations adds to the difficulty in dealing with such wells. Recently, a new environmentally friendly chelating agent, glutamic acid-diacetic acid (GLDA), has been developed and extensively tested for carbonate and sandstone formations. Significant permeability improvements have been shown in previous papers over a wide range of conditions. In this paper, we evaluate the results of the first field application of this chelating agent to acidize a sour, high-temperature, tight gas well completed with high-chrome-content tubulars. Extensive laboratory studies were conducted before the treatment, including corrosion tests, coreflood experiments, compatibility tests with reservoir fluids, and reaction-rate measurements using a rotating disk apparatus. The treatment started by pumping a preflush of mutual solvent and water-wetting surfactant, followed by the main stage consisting of 20 wt% GLDA with a low concentration of a proper corrosion inhibitor. Following the treatment, the well was put on production, and samples of flowback fluids were collected. The concentrations of various ions were determined using ICP. Various analytical techniques were used to determine the concentration of GLDA and other organic compounds in the flowback samples. The treatment was applied in the field without encountering any operational problems. A significant increase in gas production that exceeded operator expectations was achieved. Unlike previous treatments where hydrochloric acid (HCl) or other chelates were used, the concentrations of iron, chrome, nickel, and molybdenum in the flowback samples were negligible, confirming low corrosion of well tubulars. Improved productivity and longer-term performance results confirm the effectiveness of the new chelate as a versatile stimulation fluid.

HT Stimulation Fluid Based On GLDA Meets Productivity, Environmental Need

Technology Update Industry operations are shifting toward high-temperature (HT) downhole set-tings, expensive tubular metallurgy, and extended reach wells, while health, safety, and environmental requirements become stricter. Consequently, conventional stimulation treatments, such as applications using hydrochloric acid-based fluids, will no longer meet the industry’s needs as operational environments evolve. A new stimulation fluid developed by AkzoNobel, Dissolvine StimWell, is based on glutamic acid diacetic acid (GLDA) and has been successfully applied in the field. GLDA has high thermal stability and low corrosion potential, and is an effective stimulation fluid without adverse environmental impact. A vertical gas well in a deep, sour carbonate reservoir was successfully stimulated using GLDA. Previous matrix stimulation treatments with conventional acids in this HT gas well did not sustain the performance, and a fracture treatment was considered for the well. However, the case proved that matrix acidizing with the GLDA-based fluid was the best stimulation method for the well in terms of cost-effectiveness and regulatory issues. Stimulation Purpose The object of stimulation is to remove the production zone damage caused by the drilling and completion processes in sandstone reservoirs, and to create channels or wormholes in carbonate reservoirs. Although an industry workhorse for decades, hydrochloric acid (HCl) often produces subpar stimulation results, especially at high temperatures, because of its fast reaction near the wellbore, low acid penetration, and high corrosivity. Many problems may occur during sandstone acidizing with HCl/hydrofluoric mud acid, such as decomposition of clays in HCl acids, precipitation caused by the presence of fluoride, silica gel filming, and colloidal silica gel precipitation. As a result, mud acid may cause significant damage to sandstone reservoirs, especially for those with a high content of calcite or clays such as illite. The desirable alternative stimulation fluid would be suitable for all of these conditions, be globally applicable, and have an acceptable environmental profile. Fluids based on GLDA meet those requirements. The fluids are effective in improving permeability in carbonate and sandstone formations. Many additives such as iron control agents that are required in other fluids are not needed in GLDA-based stimulation fluids.

The biodegradable complexing agents as an alternative to chelators in sorption of heavy metal ions

The aim of this study was to explain the influence of chemical conditions on the ion exchange capacity and the kinetics of heavy metal ions i.e. copper(II), zinc(II), cobalt(II) nickel(II), cadmium(II), lead(II) and iron(III) in the presence of complexing agents of a new generation. For investigations the following complexing agents were selected: sodium salt of N-(1,2-dicarboxyethyl)-D,L-aspartic acid, which has the commercial name Baypure CX 100 (IDS), glutamic diacetic acid (GLDA) also known as Dissolvine GL-38 and N,N'-ethylenediaminedisuccinic acid (EDDS) known as EnviometTM C140. In the studies an anion exchange was applied which is a method used in water treatment and wastewater purification. This method is suitable for removal of all contaminants in the ionic form including heavy metal ions in the presence of complexing agents from different systems. The results obtained under different experimental conditions will be presented and discussed in this paper.

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.

Biodegradation of selected substances used in liquid fertilizers as an element of Life Cycle Assessment

Biodegradation of selected substances used in liquid fertilizers as an element of Life Cycle Assessment The results of laboratory investigations into the aerobic biodegradation of chelating compounds in water medium under static test conditions are presented. It was found that nitrilotriacetic acid (NTA) and glutamic acid diacetic acid (GLDA) are more readily biodegradable than ethylenediaminetetraacetic acid (EDTA) commonly used in the production of liquid fertilizers. Biodegradation was evaluated on the basis of compound decay and changes in COD.