N-diacetic Acid Research Articles

The impact of chelating agent pH on the stability and viscosity of CO2 foam under harsh reservoir conditions

The injection of CO2 foam into the carbonate reservoir for enhanced oil recovery (EOR) has attracted special interest in the last decades; nevertheless, the understanding of the effect of liquid solution chemistry on foam stability at high temperatures and salinities is limited. Hence, this paper fully investigates the effect of chelating agents L-glutamic acid-N, N-diacetic acid (GLDA) pH, and hydrochloric acid (HCl) on the stability and viscosity of generated CO2 foam for heterogeneous carbonate formation under reservoir conditions. In this paper, Duomeen TTM and Armovis VES surfactants were utilized due to their capabilities to produce viscous CO2 foam under harsh conditions. The foamability, foam stability, and foam structure were studied at 100 °C and 1000 psi using a high-temperature and high-pressure (HPHT) foam analyzer. The measurement of CO2 foam viscosity was determined at 100 °C, 1000 psi, and 70 % foam quality using the HPHT foam rheometer. Rheology experiments and dynamic light scattering investigated the micelle’s size or aggregation behavior of surfactants. The obtained results showed that the Duomeen TTM generated unstable foam; however, foam stability and foamability improved with the decrease in GLDA pH. Armovis VES showed excellent CO2 foam performance, where the foam half-life time of Armovis VES systems was 240 min. The liquid drainage and bubble coarsening were delayed due to the formation of the viscoelastic liquid phase. The foamability of Armovis VES was improved as the GLDA pH decreased. Furthermore, the addition of HCl to Armovis VES solution presented the highest foamability. The outcomes of the HPHT foam analyzer and HPHT viscometer proved that as the pH of Armovis VES solution decreased, higher foamability was produced. The highest foam viscosity was obtained using the synergic effect of 0.5 wt% Duomeen TTM and 0.5 wt% Armovis VES (39 cp at 100/s). In comparison, 1 wt% Armovis VES presented the lowest foam viscosity (30 cp at 100/s). The outcomes of this research can provide insight into the effect of chemistry on CO2 foam and extend its application in oilfield development. This work broadens the design of novel CO2 foam formulation, leading to the improvement of sweep efficiency in CO2-EOR methods and enhance the gas trapping in carbon storage.

Glutamic-N,N-Diacetic Acid as an Innovative Chelating Agent in Microfertilizer Development: Biodegradability, Lettuce Growth Promotion, and Impact on Endospheric Bacterial Communities

The search for new biodegradable fertilizers to increase the productivity of agricultural plants is an urgent task. In this study, a complex microfertilizer was developed based on a chelating agent—glutamic-N,N-diacetic acid (GLDA). The evaluation encompassed assessments of biodegradability and effectiveness in fostering lettuce plant growth in hydroponic and conventional soil settings. The impact on endospheric bacteria, a sensitive indicator, was also examined. Results indicated a 59.8% degradation rate of the GLDA complex on the 28th day. The most notable positive effects were observed in above-ground plant biomass, with a 4.6-fold increase for hydroponics and 1.5 to 1.8-fold increases for root and foliar treatments in soil. In hydroponics, GLDA-treated plants showed 24 and 45 operational taxonomic units (OTUs) for leaves and 272 and 258 for roots (GLDA-treated and control plants). In soil, the OTU counts were 270 and 101, 221 and 111, and 198 and 116 in the leaves and roots of GLDA-treated and control plants (under root and foliar treatments), respectively. Non-metric multidimensional scaling (NMDS) and Indicator Species Analysis (ISA) demonstrated significant distinctions in endospheric communities between substrates (hydroponics and soil) in the presence of GLDA. Importantly, GLDA use simplified the composition of endospheric bacterial communities.

Multiscale Pore Structure Evolution of Different Rank Coals Induced by Chelating Agent Intrusion

Summary China’s coalbed methane (CBM) reservoirs are characterized by low permeability (<1 md). Stimulation with conventional acids is facing the problems of secondary precipitation, high corrosion rates, and fines migration. Chelating agent intrusion was proposed as a promising alternative for conventional acids, while the pore structure evolution induced by it needs to be further clarified. In this study, coal samples with three different ranks were selected and treated with L-glutamic acid N, N-diacetic acid (GLDA). Low-temperature Ar and N2 adsorption tests, mercury intrusion porosimetry (MIP), and scanning electron microscope (SEM) analyses were applied to investigate nanoscale to macroscale pore structure changes. X-ray fluorescence (XRF) spectroscopy tests were conducted to determine the mineralogical change of coal. The results show that chelating agent intrusion can widen fracture width, connect micropores, and create void space in macropores by dissolving carbonate minerals, while the nanoscale pore volumes (PVs) showed a slight decrease due to clay minerals collapse. The fractal dimensions Dm calculated by the MIP results of lignite, bituminous coal, and anthracite coal decreased by 0.2735, 0.1734, and 0.1444, respectively. It is indicated that a pore structure with a diameter of >100 nm of the coal became more unified, which favors the seepage of gas/water. The chelating agent intrusion shows a significant effect on lignite, followed by bituminous and anthracite coal. However, the metal element reduction rate of anthracite coal presents the highest, followed by bituminous coal and lignite. There can be a risk that a long intrusion time would loosen the skeleton of lignite, leading to further reservoir damage. Therefore, bituminous and anthracite coal samples are preferred, as the skeletons of higher-rank coals are more compact. These research findings introduced a potential stimulation method for enhancing CBM recovery and provided references for field application.

A new, green, highly effective procedure for manganese determination using alizarin-3-methylamino-N,N-diacetic acid immobilised on a polymer matrix

ABSTRACT The determination of Mn(II) ion in real objects is an important task in the medicine, pharmacology, biology, chemistry, and engineering sciences. The used methods are usually expensive, hazardous, low effective and time-consuming. In this investigation, a new, green, highly effective, selective, cost-effective and time-saving analytical regent was introduced for Mn(II) determination. The analytical properties of alizarin-3-methylamino-N,N-diacetic acid (AMADAA) immobilised onto polyethylene polyamine-modified polyacrylonitrile (PPP) matrix, AMADAA/PPP, in the determination of Mn(II) ion was studied by the spectrophotometric, potentiodynamic titration, spectroscopic analyses, and X-ray fluorescence and, besides comparing the results, selectivity was checked. It was found that (i) high selectivity, high accuracy, low detection limits, good repeatability, easy regeneration, and high speed are accessible for the proposed analytical procedure, using AMADAA/PPP matrix; (ii) spectroscopic signals of AMADAA-immobilised PPP matrix and its complex with Mn(II) ion were at 500 and 580 nm, respectively; (iii) determination limit of the analytical method for Mn(II) ion was 0.02 µg/mL; (iv) the selectivity of the used reagent, AMADAA/PPP, was very high for Mn(II) ion in the presence of Ca(II), Mg(II), Cd(II), Zn(II) and Fe(II) ions.

Corrosion inhibitor and chelating agent impact on foam stability for formation stimulation applications

Injection of foam into petroleum reservoirs has attracted special interest in the last years. Utilizing foam in well stimulation is promising as it consumes less water than water-based fracturing fluids. Nevertheless, the success of foam application mainly depends on its stability. Thus, it is essential to understand the role of gas type, water chemistry, and other additives such as acids (e.g., chelating agent) and corrosion inhibitors on the generation and stabilization of foam. Hence, a dynamic foam analyzer (DFA) and optical interfacial tensiometer were used to study foam stability under different conditions. Surfactant screening showed that Duomeen TTM and Armovis are superior foamers at low pH (3.5), and therefore were used in this study. The liquid phase typically contained high salinity water, 15 %wt. Chelating agent, L-glutamic acid-N, N-diacetic acid (GLDA), and 1 %wt. surfactant with and without a corrosion inhibitor (CI). First, we investigated the effect of gas types on the stability of the foam. The results revealed that N2-foam is more stable compared to CO2-foam. Also, the results showed that the corrosion inhibitor reduced the foam stability for both N2-foam and CO2-foam. Three types of water were examined; distilled water (DI), produced water (PW), and seawater (SW) for foam stabilization. The water chemistry had little effect on the stability of TTM compared to its impact on Armovis. Finally, we found that GLDA addition to Armovis increased the stability of foam by four times compared to no GLDA addition. Moreover, the stability GLDA/Armovis system was six times higher with CO2 and more than 20 times higher with N2 as compared to TTM stability. The foamability, foam volume, bubble count, and foam structure were studied to determine the foam behavior at given conditions. This study provides a broad understanding of additives’ impact on stimulating foam stability.

The Impact of Green Chelating Agent and Corrosion Inhibitor on Foam Rheology and Stability at High Temperature, Pressure, and Salinity

Summary This research fills the gap in understanding the impact of corrosion inhibitors (CIs) and a chelating agent on the rheology and stability of foam under harsh conditions. In this regard, a modified high-pressure, high-temperature (HPHT) foam rheometer and HPHT foam analyzer were used to investigate foam rheology and stability at 1,000 psi and 120 to 150°C with carbon dioxide (CO2) in the gas phase. Surfactant screening showed that Duomeen TTM and Armovis are thermally stable at high temperature and high water salinity and thus were used in this study. The liquid phase generally contained produced water (PW) (total dissolved solids ~ 24,611 ppm), 15 wt% chelating agent [L-glutamic acid-N, N-diacetic acid (GLDA)], and 1 wt% surfactant with and without a CI. First, we screened the viscosity and stability of Duomeen TTM and Armovis; the results showed that Duomeen TTM has a higher viscosity (at least by 82%) at a low shear rate, but both have similar viscosity at a higher shear rate. However, Armovis produced more stable foam. Once the GLDA was added to the Duomeen TTM solution, the viscosity increased significantly by 135% at a high shear rate (1,000–1,500). For the Armovis system, the viscosity improved by 77% and 68% at the low and high shear rates by adding GLDA. Additionally, foam stability was improved remarkably in both systems; half-life time almost doubled. Finally, we reported the effect of CI on the fluid systems, showing it considerably reduced the foam viscosity and stability. It reduced the half-life of the Armovis system by 79.4% and hindered the generation of foam for the Duomeen TTM system. A detailed discussion of foam properties, such as foamability, bubble count, and bubble radius, is provided. This study provides a wide-ranging understanding of additives’ impact on stimulating foam stability at HPHT.

Effects of Simultaneous Application of Double Chelating Agents to Pb-Contaminated Soil on the Phytoremediation Efficiency of Indocalamus decorus Q. H. Dai and the Soil Environment.

Recent studies have shown that the combined application of ethylenediaminetetraacetic acid (EDTA) and degradable chelating agents can enhance EDTA's affinity for heavy metals and reduce its toxicity, but the effect of this combination on the phytoremediation remains largely unknown. This study evaluated and compared the effects of EDTA, nitrilotriacetic acid (NTA), and glutamic acid-N,N-diacetic acid (GLDA) alone (E, N, G treatment), and in combination (EN and EG treatment), on the growth of dwarf bamboo (Indocalamus decorus Q. H. Dai), their phytoremediation efficiency, and the soil environment in Pb-contaminated soil. The results showed that treatment E significantly reduced the biomass, while treatments N and EN were more conducive to the distribution of aerial plant biomass. Except for treatment E, the total Pb accumulation in all treatments increased significantly, with the highest increase in treatment EN. For double chelating agents, the acid-soluble Pb concentrations in rhizosphere and non-rhizosphere soils of treatments EN and EG were lower than those of treatment E, and the soil water-soluble Pb content after 20 days of treatment EN was significantly lower than that of treatment EG. Furthermore, chelating agents generally increased soil-enzyme activity in rhizosphere soil, indicating that chelating agents may promote plant heavy-metal uptake by changing the rhizosphere environment. In conclusion, treatment EN had the highest phytoremediation efficiency and significantly lower environmental risk than treatments E and EG, highlighting its massive potential for application in phytoremediation of Pb-contaminated soil when combined with I. decorus.

Synthesis, radiolabeling and evaluation of [99mTc][Tc-HYNIC/EDDA]-Met(O) as a early agent for amino acid metabolic imaging in C6 glioblastoma tumor

Amino acid metabolism is recognized as a target for medical imaging due to its increase in malignant cells. Several radiotracers with primary achievement and possible subsequent chances have been designed and tested to image amino acid metabolism. Here, we report a new amino acid conjugate, with the purpose of extending [99mTc][Tc-HYNIC/EDDA]-Met(O) for single photon emission tomography (SPECT) imaging.The S-oxo-l-methionine (Met(O)) amino acid hydrazinonicotinamide (HYNIC) chelator conjugate (HYNIC-Met(O)) was prepared, using Fmoc solid-phase synthesis, and was radiolabeled with [99mTc]technetium pertechnetate, using tricine and ethylenediamine-N,N-diacetic acid (EDDA) as co-ligands. In vitro cellular uptake profile and saturation binding of radiotracer were determined on C6 glioma cells. Biodistribution and imaging studies were carried out on rat bearing C6 tumor tissue grafts.[99mTc][Tc-HYNIC/EDDA]-Met(O) was prepared in high yield and radiochemical purity (>98 %). The partition coefficient result showed that radioconjugate was very hydrophilic. The radioconjugate indicated both high cell uptake and in vitro internalization. Low nanomolar dissociation constant (66.02 nM) in C6 glioma cells was obtained for it as well. [99mTc][Tc-HYNIC/EDDA]-Met(O) revealed magnificent tumor uptake at early time points, with 1.98 ± 0.33 % injected activity per gram tumor (% IA/g) at 30 min post injection. The tumor uptake continued for 1 and 2 h and was 0.45 ± 0.33 % IA/g at 4 h. The uptake in other organs decreased much more rapidly causing high tumor to normal organ ratios so that the highest ratio of 13.25 of tumor-to-muscle at 60 min after injection was obtained with high contrast in gamma imaging.These results point out a very favorable [99mTc]Tc-labeled amino acid for targeting amino acid metabolism through target system L amino acid transporter (LAT1) in malignant cells especially C6 glioma cells. [99mTc][Tc-HYNIC/EDDA]-Met(O) manifests extremely good distribution, excretion and imaging attributes. So it seems to be an appropriate nominate for clinical imaging.

GLDA and EDTA assisted phytoremediation potential of Sedum hybridum ‘Immergrunchen’ for Cd and Pb contaminated soil

Exogenous application of chelants is a common way to enhance the phytoextraction of heavy metals. A pot experiment was conducted to investigate the influences of cadmium (Cd), lead (Pb), Cd and Pb, L-glutamic acid N, N-diacetic acid (GLDA) and ethylene diamine tetraacetate (EDTA) on the growth, Cd and Pb accumulation of Sedum hybridum ‘Immergrunchen’. The results showed that Sedum hybridum ‘Immergrunchen’ had a high tolerance to Pb treatment, followed by Cd-Pb treatment. The plant was sensitive to Cd stress. EDTA treatment was more harmful to plant growth than that of GLDA treatment. The optimal Cd concentration of shoot and root reached 27.6 mg·kg−1 and 32.6 mg·kg−1, 757 mg·kg−1 and 1,025 mg·kg−1for Pb accumulation at 100–1,500 mg·kg−1. The maximum Cd and Pb phytoextraction from 3 mmol·kg−1 GLDA treatment were 1.40 and 1.73 times as much as that of the control, 1.21 and 1.02 times under 6 mmol·kg−1 EDTA treatment. Therefore, the enhanced phytoremediation of GLDA to Cd and Pb co-contaminated soil was better than that of EDTA. GLDA-assisted phytoextraction of Cd and Pb by Sedum hybridum ‘Immergrunchen’ can be considered as a promising way to phytoremediate Cd and Pb co-contaminated soil.

Rheological study of CO2 foamed chelating stimulation fluids under harsh reservoir conditions

Foamed acid is usually an HCl acid-based stimulation fluid applied to carbonate reservoirs. However, this study investigates the rheology of a CO2 foamed chelating agent, L-glutamic acid-N, N-diacetic acid (GLDA), that acts as less corrosive, environmentally friendly, and more stable foamed acid. Foam rheometer and analyzer were used to study the foam rheology, quality, size and structure, and half-life. Five different commercial surfactants with different chemical structures were investigated. The study was conducted at 100 °C, 1000 psi, 3.5 pH level, and various water salinity, resembling harsh reservoir conditions. The general trend showed that the higher the water salinity, the higher the effective viscosity. It also showed that the chelating agent improved the effective viscosity of the high total dissolved solids (TDS) water samples. The highest viscosity (76 mPa⋅s) was attained by mixing GLDA with a cationic alkyl diamine derivative surfactant in formation water at a 100 1/s shear rate. The prolonged constant shear rate experiments revealed that some formulations are stable for more than 8 h. The study revealed that higher surfactant concentrations did not result in improved performance. For the first time, the study reveals that chelating agents could be used as a stable stimulation foamed fluid at harsh reservoir conditions.

Thermodynamic Solution Properties of a Biodegradable Chelant (L-glutamic-N,N-diacetic Acid, L-GLDA) and Its Sequestering Ability toward Cd2.

The thermodynamics of the interaction of L-glutamic-N,N-diacetic acid (GLDA) with protons was studied potentiometrically at different temperatures, ionic strengths and ionic media. Four protonation constants and corresponding enthalpy changes occurred at infinite dilution together with temperature and ionic strength coefficients. The medium effect was also interpreted in terms of the formation of weak complexes between the ligand and the cations of supporting electrolytes, resulting in a greater tendency of GLDA to chemically interact with Na+ rather than K+ and, in turn, (CH3)4N+. Formation constants of GLDA with Cd2+ were determined in NaCl(aq) at different ionic strength values. Five complex species were found, namely CdL2−, CdHL−, CdH2L0(aq), Cd2L0(aq), and Cd(OH)L3−, whose formation constant values at infinite dilution were log β = 12.68, 17.61, 20.76, 17.52, and 1.77, respectively. All the species results were relevant in the pH range of natural waters, although the Cd2L0(aq) was observed only for CCd ≥ CGLDA and concentrations of >0.1 mmol dm−3. The sequestering ability of GLDA toward Cd2+, evaluated by means of pL0.5, was maximum at pH~10, whereas the presence of a chloride containing a supporting electrolyte exerted a negative effect. Among new generation biodegradable ligands, GLDA was the most efficient in Cd2+ sequestration.

Application of Anhydrous Calcium Sulfate as a Weighting Agent in Oil-Based Drilling Fluids.

The hydrostatic pressure exerted during the drilling operation is controlled by adding a weighting agent into drilling fluids. Various weighting materials such as barite, calcium carbonate, hematite, and ilmenite are used to increase the density of drilling fluids. Some weighting additives can cause serious drilling problems, including particle settling, formation damage, erosion, and insoluble filters. In this study, anhydrite (calcium sulfate) is used as a weighting additive in the oil-based drilling fluid (OBDF). Anhydrite is an abundantly available resource used in the preparation of desiccant, plaster of Paris, and Stucco. Anhydrite application in drilling fluids is discouraged because of its filter cake removal issue. This study investigated anhydrite (anhydrous CaSO4) as a weighting agent and its filter cake removal procedure for OBDFs. The anhydrite performance as a weighting agent in OBDFs was evaluated by conducting several laboratory experiments such as density, rheology, fluid loss, and electrical stability and compared with that of commonly used weighting materials (barite, calcium carbonate, and hematite). The anhydrite was mixed in three different concentrations (62, 124, and 175 ppb) in a base-drilling fluid. The results showed that calcium sulfate enhanced rheological parameters such as plastic viscosity, yield point, apparent viscosity, and gel strength. CaSO4 reduced the fluid loss and provided better control over the fluid loss than other tested weighting materials tested at the same concentration of 124 ppb. Similarly, the emulsion stability was decreased with the increase in the amount of calcium sulfate in the OBDF. The calcium sulfate filter cake can be removed easily from the wellbore with an efficiency of 83 to 91% in single-stage and multistage removal processes, respectively using the newly developed formulation consisting of 20 wt % potassium salt of glutamic acid-N,N-diacetic acid (K4GLDA) as a chelating agent, 6 wt % potassium carbonate, and 10% ethylene glycol monobutyl ether. The introduction of anhydrite as a weighting agent can be more beneficial for both academia and industry.

Electrochemical removal of pyrite scale using green formulations

Pyrite scale formation is a critical problem in the hydrocarbon production industry; it affects the flow of hydrocarbon within the reservoir and the surface facilities. Treatments with inorganic acids, such as HCl, results in generation toxic hydrogen sulfide, high corrosion rates, and low dissolving power. In this work, the dissolution of pyrite scale is enhanced by the introduction of electrical current to aid the chemical dissolution. The electrolytes used in this study are chemical formulations mainly composed of diethylenetriamine-pentaacetic acid–potassium (DTPAK5) with potassium carbonate; diethylenetriamine pentaacetic acid sodium-based (DTPANa5), and l-glutamic acid-N, N-diacetic acid (GLDA). DTPA and GLDA have shown some ability to dissolve iron sulfide without generating hydrogen sulfide. The effect of these chemical formulations, disc rotational rate and current density on the electro-assisted dissolution of pyrite are investigated using Galvanostatic experiments at room temperature. The total iron dissolved of pyrite using the electrochemical process is more than 400 times higher than the chemical dissolution using the same chelating agent-based formulation and under the same conditions. The dissolution rate increased by 12-folds with the increase of current density from 5 to 50 mA/cm2. Acid and neutral formulations had better dissolution capacities than basic ones. In addition, doubling the rotational rate did not yield a significant increase in electro-assisted pyrite scale dissolution. XPS analysis confirmed the electrochemical dissolution is mainly due to oxidation of Fe2+ on pyrite surface lattice to Fe3+. The results obtained in this study suggest that electro-assisted dissolution is a promising technique for scale removal.

Pyrite-Scale Removal Using Glutamic Diacetic Acid: A Theoretical and Experimental Investigation

SummaryIron sulfide scale causes major losses in both upstream and downstream sectors of the hydrocarbon industry. Pyrite is one of the most-difficult forms of iron sulfide scale from a removal point of view. Inorganic acids such as hydrochloric acid (HCl) are not recommended for removing pyrite scales because they have many drawbacks, including low pyrite solubility, high corrosivity to the tubular system, and generation of toxic hydrogen sulfide (H2S). In this work, pyrite-scale dissolution is studied using an ecofriendly formulation of glutamic diacetic acid [L-glutamic acid, N, N-diacetic acid (GLDA)] as an alternative to HCl. Although GLDA has shown potential for removing iron sulfide in general and pyrite scale in particular, still GLDA/pyrite kinetics have not been well-understood. Both experimental and theoretical techniques have been used. The reaction kinetics has been investigated in a rotating-disk apparatus (RDA) at typical reservoir conditions of 150°C and 1,000 psi (Conway et al. 1999). Characterization techniques, including X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM), have been used to study the surface chemistry before and after treatment with GLDA, and the results support pyrite removal. Furthermore, density-functional-theory (DFT) calculations have been performed to understand the ability of GLDA to dissolve iron sulfide scale at the atomistic level. From the laboratory results, the reaction rate using 20-wt% GLDA (pH of 3.8) was 5.378×10−8 mol/cm2·s. The measured rate outperformed other proposed formulations according to the tetrakis(hydroxymethyl)phosphonium sulfate (THPS) formulation by 15 times. In addition, GLDA surpassed the most recent results on diethylenetriamine penta-acetic acid (DTPA) by nearly an order of magnitude. Moreover, pyrite dissolution in GLDA increases as the disk rotational speed increased, which indicates mass-transfer control with a diffusion coefficient of 1.338×10−7 cm2/s. Furthermore, from molecular modeling using DFT, the binding energy between GLDA and Fe2+ is calculated as –105.97 kcal/mol. The negative value observed correlates with the stability constant and indicates the strong binding affinity to Fe2+. Finally, GLDA could be recommended for pyrite-scale removal because it is biodegradable, less corrosive, free of H2S, and achieved solubility that outperformed THPS- and DTPA-basedformulations.

Effects of L-glutamic acid, N, N-diacetic acid as chelating agent on acidification of carbonate reservoirs in acidic environments

For matrix acidification in carbonate reservoirs, the use of chelating agents can avoid the problems associated with conventional acids, such as excessive acid-rock reaction and extreme corrosion on a well tubular. L-glutamic acid, N, N-diacetic acid (GLDA) has been used as a chelating agent for carbonate reservoir stimulation owing to its high water solubility, effective dissolution effect on carbonate, lower corrosion to metals than conventional acid, and high biodegradability. In this study, the dissolution and acidification effect of GLDA on Baota limestone, as well as its corrosion effect on a well tubular and iron control capabilities, were evaluated. Meanwhile, the mechanism of GLDA on Baota limestone was studied by inductively coupled plasma optical emission spectrometer (ICP-OES), zeta potential, and core flooding experiments at low pH, which was adjusted using a conventional acid. The results indicated that 5% GLDA with the pH adjusted by acetic acid (pH = 4, HAC) exhibited the most significant acidification effect on the Baota limestone. Its dissolution rates were 75.2 and 94.4% at 25 and 80 °C, respectively, after 16 h. The surface of the Baota limestone was mainly positively charged in the aqueous solution; thus, the negatively charged GLDA was easily absorbed and chelated. In terms of iron control and corrosion inhibition, 5% GLDA (pH = 4, HAC) performed better than 5% GLDA, 5% HAC, and 5% HCl. The corrosion rate of 5% GLDA (pH = 4, HAC) on P110 metal test pieces were only 0.74 and 14.43 g/(m2·h) at 25 and 80 °C, respectively, for 24 h, which showed more noticeable corrosion inhibition effects than 5% HCl (2.08 and 56.10 g/(m2·h) at 25 and 80 °C, respectively). Based on the core flooding experiment and computed tomography (CT) scanning, it was determined that 3% GLDA (pH = 4, HAC) had the most significant acidification effect on the Baota limestone at an injection rate of 1 mL/min. The permeability and porosity of the Baota limestone increased from 0.12 to 5.8 mD (approximately 48x) and from 0.44 to 2.22%, respectively. The findings of this study may provide an effective reference guide for matrix acidification design of carbonate reservoirs.

Enhanced Phytoextraction of Cadmium Contaminated Soil by Trifolium Repens with Biodegradable Chelate GLDA

Chelating agents can increase the bioavailability of heavy metals and enhance their enrichment in plants. The effects of different concentrations of biodegradable chelating agent L-glutamic acid N, N-diacetic acid (GLDA) on the remediation of heavy metal-contaminated soil by super-enriched plant Trifolium repens were investigated by pot experiments with Cd-contaminated soil. Results show that low-dose GLDA could significantly promote the growth of Trifolium repens, and the biomass of Trifolium repens was the highest at 2.5 mmol·kg-1-GLDA, which was 1.30 times that of the control group. Different concentrations of GLDA can increase Cd content of various parts of Trifolium repens. In general, the treatment effect of 5 mmol·kg-1 GLDA was ideal. In this scenario, the root, aerial parts, and whole Cd content were 3.57, 4.69, and 4.67 times of the control group, respectively. GLDA can significantly increase the available Cd content in soil, promote direct absorption at the Trifolium repens roots, and provide better transport to the aerial parts. The prediction model obtained by fitting the linear relationship between physical and chemical properties of soil indicates that GLDA and Trifolium repens Cd content can provide references for the future research of soil-Trifolium repens enrichment. Studies have shown that the biodegradable chelating agent GLDA has potential applications for enhancing phytoremediation of heavy metal Cd contaminated soil.

Effects of GLDA, MGDA, and EDTA chelating ligands on Pb sorption by montmorillonite

In this study, the effects of the new biodegradable chelating ligands, i.e., methylglycinediacetic acid (MGDA) and L-glutamic acid-N,N-diacetic acid (GLDA), were compared with that of ethylenediaminetetraacetic acid (EDTA) on lead (Pb) sorption by montmorillonite (MMT) at equimolar Pb:ligand ratios. The results of PHREEQC simulations indicated that Pb was predominantly present in the form of negatively-charged chelates with significantly different sorption behaviors compared to that of the Pb2+ cations. The time-dependent sorption of the Pb species on MMT was biphasic, with an initial fast phase occurring within 3 h followed by a slower one reaching equilibrium after approximately 12 h. The analysis of equilibrium data revealed that both capacity and affinity of MMT for Pb sorption were decreased in the presence of the chelating ligands. The moderating potential of ligands on Pb sorption decreased in the order of EDTA ≫ MGDA > GLDA in accordance with complex stability constants. The FE-SEM/EDX, ATR-FTIR, and XRD evidence indicated that Pb and Pb complexes were adsorbed, most likely through physical forces, on both external planar and edge surfaces of the MMT. In conclusion, GLDA and MGDA represented lower ability than EDTA to depress Pb2+ adsorption on MMT, and hence, lower potential to mobilize Pb in soils and sediments where MMT is an important mineral sorbent.

Reaction Kinetics and Coreflooding Study of High-Temperature Carbonate Reservoir Stimulation Using GLDA in Seawater

Well stimulation using hydrochloric acid (HCl) is a common practice in carbonate reservoirs to overcome formation damage in the near wellbore area. Using HCl for matrix acidizing has many limitations at high-temperature (HT) conditions, such as tubulars corrosion and face dissolution due to the fast reaction rate. Chelating agents, such as L-glutamic acid-N,N-diacetic acid (GLDA), are alternatives to HCl to overcome these problems. We studied the effect of diluting GLDA in seawater on the reaction kinetics with carbonate rocks under HT conditions at low pH (3.8). Results of the reaction of carbonate at 1000 psi and 150, 200, and 250 °F with GLDA prepared in both fresh and seawater, GLDA/DI and GLDA/SW, respectively, are presented. The reaction kinetics experiments were carried out in HT rotating disk apparatus (RDA) at rotational speeds ranging from 500 to 2000 revolutions per minute (RPM) at a fixed temperature. Indiana limestone and Austin chalk were used to studying the effect of rock facies on the reaction of GLDA with rock samples. In both GLDA/DI and GLDA/SW, the reaction regime of 20 wt% GLDA (3.8 pH) with Indiana limestone was mass transfer limited. The reaction rate and diffusion coefficient were highly dependent on the temperature. For Austin chalk, at 200 °F and 1000 psi the diffusion coefficient of GLDA/SW is an order of magnitude of its value with Indiana limestone using the same fluid. Diffusion coefficients were used to estimate the optimum injection rate for stimulating HT carbonate formation and compared with coreflooding results. The data presented in this paper will support the numerical simulation of the acid flow in carbonate reservoirs.

Location and magnitude of formation damage due to iron precipitation during acidizing carbonate rocks

Iron precipitation during matrix acidizing treatments continues to thwart production from carbonate reservoirs. However, an extensive literature review highlighted that no systematic study to date has been conducted to determine where this iron precipitates, the factors that affect this precipitation and the magnitude of the resulting damage. Successful iron control can be critical to the outcome of the treatment. Iron (III) precipitation occurs when acids are spent and the pH rises above 1, which can cause severe formation damage. Chelating agents are used during acidizing treatments to minimize iron precipitation, but some of the chelating agents can combine with Ca and Mg.In this work, the effect of iron precipitation during acidizing operations is studied. Hydrochloric acid (HCl) solutions (5–10 wt%) containing 5,000 to 10,000 ppm of Fe3+ served as the main fluid for the experiments described in this paper. Biodegradable GLDA (L-glutamic acid, N, N-diacetic acid) was studied in conjunction with HCl. The effect of varying acid concentration, initial core permeability, core length, temperature, flow rate, and chelant-to-iron mole ratio (CIMR) was studied. Coreflood experiments were conducted on 6 and 20 in. long Indiana limestone cores over a wide range of permeabilities at temperatures up to 300 °F. In these experiments, 0.5 PV of acid solution was injected. The cores were scanned after acid treatments using a computed tomography (CT) scanner and cut to better determine the location of iron deposition. The core effluent samples were analyzed for iron and calcium concentrations using inductively coupled plasma optical emission spectrometry (ICP-OES). A calcium ion-selective electrode measured the concentration of free calcium ions, i.e. calcium ions not complexed by the chelant, in the core effluent samples.Results showed that a significant amount of iron precipitated (up to 89%), especially, on the injection face of the cores and the inner surfaces of wormholes, i.e. where the contact occurs between the acid and the rock. The damage increased as the amount of iron increased in live acid. At higher temperatures and flow rates, the damage was significant. An inverse relation is observed between the wormhole length and extent of recoverable iron in the cases with no breakthrough. The amount of iron recovered depended on both CIMR and the initial permeability of the cores. Calcium is chelated, along with iron, which limits the effectiveness of chelating agents to control iron (III) precipitation. Chelating agents are intended to control iron now that calcium is also chelated; this amount should be accounted for. Acid solutions should be designed considering this important finding for successful treatments.

68Ga-PSMA-HBED-CC Uptake in Cervical, Celiac, and Sacral Ganglia as an Important Pitfall in Prostate Cancer PET Imaging.

The study aims to investigate the presence of physiologic prostate-specific membrane antigen (68Ga-PSMA)-ligand uptake on PET in cervical, celiac, and sacral ganglia of the sympathetic trunk as a pitfall for lymph node metastases in prostate cancer imaging. Methods: Four hundred seven patients who underwent Glu-NH-CO-NH-Lys radiolabeled with 68Ga-gallium N,N-bis[2-hydroxy-5-(carboxyethyl)benzyl]ethylenediamine-N,N-diacetic acid (68Ga-PSMA-HBED-CC) PET (combined with a diagnostic CT) were retrospectively analyzed. The number of 68Ga-PSMA PET-positive cervical, celiac, and sacral ganglia was determined, and the configuration and SUVmax of each ganglion were measured. In addition, the configuration and SUVmax of adjacent lymph node metastases in the respective region (cervical, celiac, or sacral) were determined. Results:68Ga-PSMA-ligand uptake above background was detected in 401 (98.5%) patients in any peripheral ganglia, in 369 (92%) patients in cervical ganglia, in 363 (89%) patients in celiac ganglia, and in 183 (46%) patients in sacral ganglia. The 68Ga-PSMA-ligand uptake was highest in celiac (mean SUVmax, 2.9 ± 0.8 vs. cervical mean SUVmax, 2.4 ± 0.6) and sacral (mean SUVmax 1.7 ± 0.5; both P < 0.0001) ganglia. Intraindividually there was a statistically significant but weak to moderate correlation between the 68Ga-PSMA-ligand uptake in cervical versus celiac ganglia (R = 0.34, P < 0.0001), cervical versus sacral (R = 0.52, P < 0.0001), and celiac versus sacral (R = 0.16, P < 0.05). The 68Ga-PSMA-ligand uptake was significantly more intense in adjacent lymph node metastases than the respective ganglia (cervical: 18.0 ± 16.2 vs. 2.4 ± 0.6, P < 0.0001; celiac: 13.5 ± 12.3 vs. 2.9 ± 0.8, P < 0.0001; sacral: 13.4 ± 11.6 vs. 1.7 ± 0.5, P < 0.0001). Furthermore, ganglia predominantly exhibit a band-shaped configuration (71.2%), followed by a teardrop (26.8%) and only rarely a nodular configuration (2.0%). Conversely, lymph node metastases are only rarely band-shaped (1.1%), but more often show teardrop (40.3%) or nodular appearance (58.6%) (P < 0.00001). Conclusion:68Ga-PSMA-ligand uptake in ganglia along the sympathetic trunk as assessed by 68Ga-PSMA-HBED-CC PET represents an important pitfall in prostate cancer PET imaging. The 68Ga-PSMA-ligand uptake is higher in celiac ganglia than cervical or sacral ganglia, and the level of 68Ga-PSMA-ligand uptake seems to be patient-related. For the differentiation between lymph node metastases and sympathetic ganglia, both intensity of 68Ga-PSMA-ligand uptake and exact localization and configuration of the respective lesion should be examined carefully.