Concentration Of Chelating Agent Research Articles

Production of colloidally stable calcium carbonate precipitates to enhance CO2 subsurface storage through mineralization

Around the world, a lot of conversations centre on the pursuit of carbon sequestration and storage. The goal is to create solutions that minimize atmospheric emissions while guaranteeing storage security. In light of this, mineral and solubility trapping are seen to be the safest among the numerous potential alternatives. Aquifers and depleted oil and gas reservoirs are just two of the many possible storage locations for solubility trapping that exist worldwide. However, all brines have a maximum solubility limit that once reached, no further CO2 can be dissolved, thus, its limitation. On the other hand, because CO2 is transformed into solids and stored in that state in the case of mineral trapping, it is deemed the safest long-term storage option. But according to recent research, it takes a long time—roughly two years—to complete. Thus, the mineralization of CO2 in a CaCl2-rich solution is shown for the first time to be accomplished in 24 h. This study's technique included using a chelating agent to achieve mineralization and looking at the effects of pressure, temperature, and chelating agent concentration on the process.The findings of this investigation demonstrated that, in the presence of a chelating agent, calcite precipitation can occur from the interaction of CO2 with a CaCl2-rich solution in less than a day. The chelating agent's dehydration of the cations (Ca2+) to speed up their interaction with the carbonate ion in the solution is the mechanism causing the notable improvement in the mineralization kinetic observed here. Mineralization, which is normally assumed to take a long time, can be accomplished in a day by following this easy procedure. Further investigation was conducted on the precipitates' bulk and mineralogical composition. Additionally, a scanning electron microscope was utilized to identify the five unique crystal forms that were created in the precipitated calcite. The results of this study are also regarded as revolutionary since they have far-reaching consequences for our efforts to store CO2 in the safest possible way. Furthermore, reject water from a water treatment procedure like reverse osmosis might be the feed stream for the process this study describes. Consequently, wastewater can be turned into wealth and help achieve sustainability objectives.

Dispersing Settled Barite: An Approach to Improve Performance and Safety of Cut and Pull in Plug and Abandonment Operations

Summary Settled barite is a known challenge in well construction and well control activities. This phenomenon creates operational and safety challenges during cut and pull operations in well abandonment activities. In this paper, we introduce a novel approach to mitigate these challenges by dispersing settled barite particles using chelating agents, specifically ethylenediaminetetraacetic acid (EDTA) and diethylenetriamine pentaacetic acid (DTPA), commonly utilized in the oil industry to dissolve barite scales. Laboratory tests were conducted to assess the impact of these two chelating agents across varying concentrations, weight-to-volume ratios, pH levels, and durations. Settled barite samples retrieved from a plug and abandonment (P&A) operation were used in this test. Initially, visual inspection suggested some action of chelating agents in fragmenting settled barite materials into smaller particles. Afterward, a sequence of sieves was used to assess the particle-size distribution (PSD) and quantify the dispersion, revealing an increase in particle dispersion correlating with higher concentrations of chelating agents and weight-to-volume ratios. Contrary to scale-dissolving experiments, the dispersion of settled barite manifests across a broad pH spectrum. Furthermore, an initial increase in dispersion was observed over time, while the introduction of an activator such as potassium chloride (KCl) displayed no discernible effect on the overall dispersion process. This work shows the potential resolution of settled barite issues through the application of conventional chelating agents, such as EDTA and DTPA, commonly used within the oil field. It suggests methodologies for optimizing their performance in addressing barite settlement concerns. In addition, the study proposes the broader applicability of chelators within the EDTA and DTPA family for dispersing settled barite, thereby enhancing performance and augmenting oilfield safety in chelator use.

A complementary eco-friendly approach to heavy metal removal from wastewater/produced water streams through mineralization

With the world's ever-increasing population, portable water needs have significantly increased. This has put enormous pressure on the limited supply of freshwater around the globe and has necessitated the development of water treatment technologies that would convert saline waters into potable water for domestic and industrial uses. As saline water is treated for usage, so is wastewater generated from domestic and industrial processes. More prominently, another wastewater source is produced water consequent to oil production. Wastewater and produced water are similar in that they are both high in pollutants (heavy metals), which in discharge streams need to be kept within a threshold. The fact that heavy and rare earth metals linked to the produced water cannot be completely removed by state-of-the-art technologies is even more concerning. Thus, a complementary technology must be developed for this reason. This study investigates the mineralization of water-polluting heavy metals. The approach adopted involves the exposure of contaminated water to atmospheric or captured CO2 and the use of additives to achieve the removal. To gain a deeper understanding of how these innovative efforts function, the study also looked into the mechanism used to eliminate the heavy metals. The findings show that heavy metals in produced water and industrial effluent can be precipitated and immobilized to remove them. More so, this is made possible by the infusion of heavy metals into the crystal structures of precipitates like aragonite, calcite, and halite. Furthermore, the mechanism of the heavy metal removal involves their dehydration, immobilization and precipitation. Additionally, DFT calculations were utilized to support the experimental results by shedding light on the heavy metal hydration's ground-state structures and how EDTA chelates the heavy metals and enhances the process kinetics. The study's findings show how this strategy complements the most advanced wastewater treatment method in terms of increasing its efficiency and water security and safety. More so, as this is a pioneering effort, the optimum concentration of chelating agent and route (atmospheric or captured CO2) must be determined on a case-to-case basis for field implementation. Furthermore, the limitation of this study is that the efficiency of heavy metal removal may differ based on the starting brine composition, thus, optimization must be conducted beforehand.

Class II (three-layer system) phenomenological model based on limiting current density and dynamic chelation chemistry for separation of rare earth elements using electrodialysis

This paper presents an in-depth investigation into the optimization of rare earth element (REE) separation through electrodialysis, leveraging a newly developed Class II phenomenological model. This study explores the pivotal roles of the HEDTA/Nd molar ratio and pH of feed solution on enhancing the separation efficiency of neodymium (Nd) and praseodymium (Pr) from lanthanum (La) and cerium (Ce). By integrating expanded Nernst-Planck equations and the concept of limiting current density, the model offers a sophisticated understanding of ion transport dynamics and the impacts of concentration polarization. Experimental validation confirms the model’s predictive accuracy, demonstrating its practical applicability for industrial-scale operations. The research delineates how operational parameters such as chelating agent concentration and pH critically influence the purity and yield of separated REEs. The dynamic nature of chelation chemistry is also examined, highlighting its evolution during the electrodialysis process and its effect on the system’s overall performance. Key findings illustrate that lower HEDTA/Nd molar ratios significantly enhance the purity of Nd + Pr by minimizing the chelation of La and Ce, thus facilitating their migration to the concentrate compartment. Conversely, higher ratios maximize yield by retaining more Nd + Pr in the feed compartment. This dual approach allows for optimized separation based on specific industrial requirements. The outcomes of this study not only advance the field of REE separation but also provide a framework for further research into more efficient and sustainable extraction methods. The developed model and its validation represent a step forward in the practical application of electrodialysis in REE processing, offering substantial benefits for the critical materials sector.

Hydrophobic deep eutectic solvent-based vortex-assisted dispersive liquid–liquid microextraction with UV–visible spectrophotometry for copper determination in waste printed circuit boards

ABSTRACT Nearly all electronic devices utilise Printed Circuit Boards (PCBs), which contribute significantly to the generation of electronic waste (e-waste). They are rich in metal content, with copper being present in higher percentages. In this work, a simple, efficient and environment-friendly pre-concentration technique was developed, using hydrophobic deep eutectic solvent as an extractant in vortex-assisted dispersive liquid–liquid microextraction. This pre-concentration technique is coupled with spectrophotometry for the determination of copper in PCBs. The complexing agent, sodium diethyl di-thiocarbamate (DDTC), and copper formed a complex in the 2–3 pH range. The Cu-DDTC complex was vortexed for 1 min at 2800 rpm to extract in hydrophobic DES. The sediment was analysed using a UV–Visible spectrophotometer at λ max 435 nm. The optimisation parameters, including pH, extraction solvent selection and its volume, concentration and volume of chelating agent, interference of forein ios, etc., have been assessed. Analytical figures of merit such as limit of detection (1.98 μg/L), limit of quantification (5.9 μg/L), relative standard deviation (3.4%) and enrichment factor (10) have been obtained under optimal experimental conditions. The method was validated by a certified copper solution and applied successfully to determine copper in waste PCBs of personal computers.

Study on the scale inhibition performance of organic chelating agent aided by surfactants on CaCO3 at high salinity condition

Abstract The salt blockage layer formed in the wellbore during the development of high salinity oil and gas fields has a serious impact on the safety of oil and gas production of the oil and gas fields. CaCO3 is the main component of scale in high salinity oil and gas fields. Herein, focusing on CaCO3 as an example, the precipitation and scaling process as well as the change of crystalline form of CaCO3 under different temperature and salinity conditions were studied. The effects of two addition methods of organic chelating agent on the solubilization and dislodgement of CaCO3 under high salinity conditions were also explored. The optimal concentration of organic chelating agent is determined to be 1 % and 5 % for solubilization and dislodgement, respectively. It was found that the solubilization is achieved by inhibiting the stable and difficult to treat calcite crystal phase to generate more irregular and more dispersed aragonite CaCO3. Organic chelating agent contains a large number of carboxyl groups in its molecules, which can be adsorbed onto the surface of CaCO3 crystals through electrostatic adsorption. By chelating Ca2+ in stable and difficult to treat calcite CaCO3, the further ordered growth of the crystals is prevented, causing lattice distortion or large crystal rupture, thereby achieving dislodgement. This study will provide theoretical and technical support for the solubilization and dislodgement of salt blockage layer in wellbore at high salinity conditions.

Preparation of landscape gardening soil using undersized fraction from aged MSW by EDTA or citric acid coupled with humic acid: Effect assessment, properties, and optimization

ABSTRACT Undersized fraction from aged municipal solid waste (UFAMSW), as a kind of soil-like material, has been proved effective in providing a large amount of organic matter and nutrients for soil and plants. The characteristics and effectiveness of heavy metal pollution removal in UFAMSW attracted tremendous research interest from scientists recently. In this study, the heavy metal removal efficiencies and bioavailability of washing on contaminated UFAMSW were evaluated with three washing reagents including ethylene diamine tetra acetic acid (EDTA), citric acid (CA), and humic acid (HA). The effects of chelating agent concentration, pH, and washing time on metal removal were investigated and response surface methodology (RSM) was employed to optimize the washing conditions. The results indicated that the removal efficiencies of Cu, Zn, and Mn could be 53.68%, 52.12%, and 30.63% by EDTA/HA washing and 42.36%, 39.67% and 28.49% by CA/HA washing, respectively. The European Community Bureau of Reference (BCR) sequential extraction was applied to analyze the fraction change of heavy metals in UFAMSW before and after washing, and it was found that chelating agent combined with HA could contribute to the removal of the exchangeable fraction. Physical and chemical properties of UFAMSW were improved to some extent after washing with mixed HA and chelating agent and could achieve the quality standard of landscape gardening soil. Accordingly, the mixture of HA and other chelating agents could be a promising washing process for preparation of landscape gardening soil using UFAMSW. Implications: Our manuscript studies the removal of heavy metals from the contaminated undersized fraction from aged municipal solid waste (UFAMSW). UFAMSW, as a kind of soil-like material, has been proved effective in providing a large amount of organic matter and nutrients for soil and plants however often limited by heavy metal pollution. The UFAMSW used in this experiment was collected after the excavation and screening-sorting of aged refuse from Changshankou Domestic Waste Sanitary Landfill in Wuhan City, Hubei Province, Southern China. This study investigated the effects of EDTA, CA, HA, mixed EDTA/HA, and mixed CA/HA washing on heavy metal removal (Cu, Zn, and Mn), bioavailability of residual heavy metal and properties. The effects of chelating agent concentration, pH, and washing time on metal removal were investigated and then response surface methodology was employed to optimize the washing conditions. The results showed that washing by CA/HA and EDTA/HA, had a higher removal efficiency of heavy metals (Cu, Zn, and Mn) in UFAMSW compared to single HA. Meanwhile, HA has a higher removal for exchangeable fraction of heavy metals, the exchangeable concentration of Cu, Zn, and Mn in CA/HA and EDTA/HA washed UFAMSW were lower compared with UFAMSW washed by single CA and EDTA. Thus, mixing HA with EDTA or CA makes a less risk to environmental and the removal efficiency is acceptable. Additionally, CA/HA and EDTA/HA washing tend to improve soil physicochemical properties and soil fertility. Thus, mixing HA with different washing agent are potential methods for preparation of landscape gardening soil using UFAMSW.

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.

Separation of rare earth elements using chelation-assisted electrodialysis

Rare earth elements (REE) find crucial applications in electronics, clean energy, aerospace, automotive, and defense sectors. However, the conventional solvent extraction (SX) technique currently dominates the process of isolating individual REE into pure elements, presenting challenges due to its extensive stage requirements and environmental footprint. To address these limitations, this study explores chelation-assisted electrodialysis (ED) as a promising alternative to SX for efficiently separating light and medium REE from binary and tertiary solutions. By incorporating chelating agents into the ED process, we aim to enhance separation efficiency while mitigating the drawbacks associated with SX. A laboratory-scale ED system with a microflow cell consisting of five pairs of Neosepta® cation and anion exchange membranes in an alternating configuration was utilized. Aminopolycarboxylic acids such as Ethylenediaminetetraacetic acid (EDTA), diaminocyclohexanetetraacetic acid (DCTA), N-(2-hydroxyethyl) ethylenediaminetriacetic acid (HEDTA) and diethylenetriamine-pentaacetic acid (DTPA) were employed as chelating agents to increase the selectivity of REE separation. The effects of operating voltage, operation mode, pH, type of electrolytes, and membrane configuration on the separation process were investigated. ED was conducted at varying concentrations of REE and chelating agents, and the system was optimized for the highest separation factors. It was observed that the separation factors increased by increasing the voltage due to the higher ionic mobility of non-chelated REE at higher voltages. Precipitation of REE in ED compartments was one of the main challenges in the tests. To prevent the precipitation, a modified membrane configuration and an optimized pH window of 3.0–4.5 were applied. At optimized operating conditions, the REE separation factors of up to 42 were achieved, which were up to 20 times greater than those reported for the conventional SX process. The final REE concentrations in the concentrate compartment were comparable with those calculated from the dissociation equilibrium equations and in most cases, less than 10 % error was observed between the experimental results and the calculations.

Use of in-situ surfactant-based solid phase extraction for determination of low concentrations of CrIII in infusions of medicinal plants

A new solid phase extraction procedure, known as in situ surfactant-based solid phase extraction, has been proposed to detect the presence of CrIII in infusions of medicinal plants. In this work, a small amount of cetyltrimethylammonium bromide was injected into a sample containing CrIII, which was complexed by 1-(2-pyridylazo)-2-naphthol. After shaking, a small volume of NaClO Was added to the solution as an ion-pairing agent. After preconcentration, the settled phase was dissolved in a specific volume of HCl and then analyzed by Flame Atomic Absorption Spectrometry. A Doehlert matrix was used to optimize the CrIII complex formation conditions, such as the chelating agent concentration (0.18 mmol L-1) and pH of 9.5 in the reaction medium. A 23 factorial design was used to screen the variables that influence the extraction of the complex. The concentration of ionic-pairing agent (0.26 mol L-1) and the vortex mixer agitation time (7.51 minutes) were significant and optimized using response surface methodology. The limit of detection, limit of quantification, and preconcentration factor were 1.66 μg L-1, 5.5 μg L-1 and 12, respectively. The linear range was 5.5-5000 μg L-1. The method proved accuracy by the comparison with certified reference material APS-1071 (p>0.05), and the optimized conditions were successfully applied for the determination of CrIII in samples of medicinal plant infusions.

Removal of Ferrous using Citric Acid in Patchouli Oil Purification by Complexometry

This study is aimed to examine citric acids as a potential chelating agent to decrease colloidal impurities in patchouli oil to improve its quality. It covers colour, specific density, refractive index, acid value, iron content, oleoresin oil content, and patchouli alcohol. Complete Randomized Design with factorial design is used with two factors and repeated 3 times. Factors are (1) citric acid concentration consists of 0.25%, 0.5%, 1.0% and 1.50% (w/v), (2) stirring time of 30, 60 and 90 minutes. Further, purified oil by citric acid was compared to purified oil by Ethylene Diamine Tetra Acetate (EDTA). Findings show that the concentration of chelating agents and the time of stirring have an effect on the quality of patchouli oil. The higher the chelating concentration and the more the stirring time, the better the quality of purified patchouli oil in terms of colour, specific density, refractive index, acid value, and iron content. Findings also show that citric acid has almost the same performance as EDTA. The main components in patchouli oil (patchouli alcohol and oleoresin oil) are not affected by treatment. Purified patchouli oil by using citric acid meets Indonesian National Standard (SNI) requirements so citric acid is one of the potential chelating agents.

Experimental Investigation and Modeling of Fluid and Carbonated Rock Interactions with EDTA Chelating Agent during EOR Process

The injection of chemical fluids into oil reservoirs is gaining widespread attention in light of the declining conventional oil resources by recovering more hydrocarbons. This study is focused on using a chemical called ethylenediaminetetraacetic acid (EDTA) chelating agent in a carbonate reservoir to shed light on contact angle differences of 625 aged thin sections and rock dissolution under the influence of different pHs, temperatures, chelating times, and various chelating agent concentrations in seawater. According to a rock dissolution test, at least 5 wt % of EDTA chemical is needed to obtain oil recovery. A ζ potential test and scanning electron microscopy (SEM) images revealed that the mechanism of adsorption at low pH values and the expansion of the electrical double layer (EDL) at high pH values were responsible for wettability alteration, and an increase in EDTA concentration intensified each mechanism. Interfacial tension (IFT) measurements also showed that adding 1 and 10 wt % of the EDTA to the seawater solution reduced the IFT by 67.75% and 76.08%, respectively. The contact angle experiments demonstrated an increase in the mechanism that leads rock to behave more hydrophilically as pH, solution temperature, and chelating agent concentration in saltwater increased. Artificial neural network (ANN) methods also led to the introduction of a model to predict the contact angle employing multilayer perceptron neural networks (MPNN) and cascade feedforward neural networks (CFFNN). The CFFNN with two hidden neurons and trained by the Levenberg–Marquardt backpropagation algorithm is the most accurate model when comparing the accuracy of models for predicting contact angle values. The CFFNN model indicated that the weight percentage of the chelating chemical, which has a share of about 90%, had the greatest influence on the contact angle, and chelating time, with a share of less than 10%, had the least.

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.

Factorial design optimization of dispersive liquid–liquid microextraction for analysis of metals in natural and drinking waters

In this work, a dispersive liquid–liquid microextraction method combined with inductively coupled plasma optical emission spectrometry was developed to extract and pre-concentrate the trace metals cadmium and lead. Variables such as extracting solvent, dispersive solvent and chelating agent were studied using a univariate design. On the other hand, parameters such as pH, volume of the extracting solvent, volume of the dispersive solvent and concentration of the chelating agent were optimized using a factorial design 24. Doehlert design was used to improve the conditions established in the factorial design. The optimized method consisted of chelating agent concentration of 0.05 % (w/v), 8000 µL of dispersive solvent (ethanol), 600 µL of extracting solvent (chlorobenzene) and a pH of 7.0. Using these conditions, it was obtained a limit of detection of 0.85 and 0.55 µg L-1, enrichment factors of 13.4 and 10 and relative standard deviation of 0.8 and 3.7 % (5 µg L-1, n = 3) for the metals Cd and Pb, respectively. The developed methodology was applied for the analysis of cadmium and lead in natural and drinking water samples.

Rheological Study of Seawater-Based Fracturing Fluid Containing Polymer, Crosslinker, and Chelating Agent.

Freshwater is usually used in hydraulic fracturing as it is less damaging to the formation and is compatible with the chemical additives. In recent years, seawater has been the subject of extensive research to reduce freshwater consumption. The study aims to optimize the rheology of seawater-based fracturing fluid with chemical additives that reduce the formation damage. The studied formulation consists of a polymer, a crosslinker, and a chelating agent to reduce seawater hardness. We used a standard industry rheometer to perform the rheology tests. By comparing five distinct grades [hydroxypropyl guar (HPG) and carboxymethyl hydroxypropyl guar (CMHPG)], we selected the guar derivative with the best rheological performance in seawater. Five different polymers (0.6 wt %) were hydrated with seawater and freshwater to select the suitable one. Then, the best performing polymer was chosen to be tested with (1.6, 4, and 8 wt %) N, N-dicarboxymethyl glutamic acid GLDA chelating agent and 1 wt % zirconium crosslinker. In the first part, the testing parameters were 120 °C temperature, 500 psi pressure, and 100 1/s shear rate. Then, the same formulations were tested at a ramped temperature between 25 and 120 °C. We observed that higher and more stable viscosity levels can be achieved by adding the GLDA after polymer hydration. In seawater, an instantaneous crosslinking occurs once the crosslinker is added even at room temperature, while in freshwater, the crosslinker is activated by ramping the temperature. We noted that, in the presence of a crosslinker, small changes in the chelating agent concentration have a considerable impact on the fluid rheology, as demonstrated in ramped temperature results. It is observed that the viscosities are higher and more persistent at lower concentrations of GLDA than at higher concentrations. The study shows the rheological response when different chemical additives are mixed in saline water for hydraulic fracturing applications.

Iron Sulfide Scale Inhibition in Carbonate Reservoirs.

Hydrocarbon production operations include water injection, varying stimulation approaches, and enhanced oil recovery techniques. These treatments often affect reservoir formation, production, and injection facilities. Such sorts of well operations cause the formation of organic and inorganic scales in the near-wellbore region and various production and injection structures. Downhole squeeze treatment is commonly used as a control measure to prevent scale precipitation. A scale inhibitor solution is introduced into a formation by applying a squeeze treatment. The method allows scale inhibitors to adsorb on the internal rock surface to avoid settling down the scale precipitates. Thus, the study of adsorption of different types of inhibitors to prevent scale formation on the reservoir rock through the execution of downhole squeeze treatment is becoming necessary. This study incorporated different experimental techniques, including dynamic adsorption experiments of chelating agents employing a coreflooding setup, inductively coupled plasma-optical emission spectrometry (ICP-OES) to inhibit the formation of iron-containing scales in limestone rocks, and ζ-potential measurements targeting determination of iron precipitation in varying pH environments on calcite minerals. The influence of the inhibitor soaking time and salt existence in the system on chelating agent adsorption was also evaluated in the coreflooding experiments. The findings based on the coreflooding tests reveal that the concentration of chelating agents plays a significant role in their adsorption on carbonate rocks. The treatments with 20 wt % ethylenediaminetetraacetic acid (EDTA) and 20 wt % diethylenetriaminepentaacetic acid produced the highest adsorption capacity in limestone rock samples by inhibiting 84 and 85% of iron(III) ions, respectively. Moreover, the presence of the salts (CaCl2 and MgCl2) considerably decreased the adsorption of 10 wt % EDTA to 56% (CaCl2) and 52% (MgCl2) and caused nearly 20% more permeability reduction, while more inhibitor soaking time resulted in comparably higher adsorption and lesser permeability diminution. The results of ζ-potential measurements showed that the pH environment controls iron(II) and (III) precipitation, and iron(III) starts to deposit from a low pH region, whereas iron(II) precipitates in increased pH environments in calcite minerals.

Efficiently combined technology of precipitation, bipolar membrane electrodialysis, and adsorption for salt-containing soil washing wastewater treatment

Wastewater of that washing of soil that results in concentrations of inorganic salts, toxic metals, chelating agents, and refractory dissolved organic matter may threaten the surrounding environment. Simultaneously, the removal of contaminants and the recovery of resources from this wastewater remain challenging. This study investigated the probability of a novel combined treatment (chemical precipitation + bipolar membrane electrodialysis (BMED) + activated carbon (AC) adsorption) on salt-containing soil washing wastewater treatment. The results showed that the proposed combined treatment could achieve proficient removal of heavy metals, inorganic salts, and total organic carbon (TOC) with low energy consumption (removal efficiency of heavy metals and inorganic salts > 94%; TOC removal > 58%). Meanwhile, the efficient recovery of acid and alkali could also be realized in the proposed treatment (acid-production rate = 7.76 ± 0.38 mmol/h and base-production rate = 5.47 ± 0.42 mmol/h at 50 mA/cm2). The mechanism result indicated that the chemical precipitation process could achieve high removal of heavy metals. Then, the BMED process induced an efficient separation of organic matter and inorganic salts. Accordingly, the AC adsorption process could efficiently remove organics. Preliminary economic evaluation results revealed that the combined process could proficiently treat the soil washing wastewater with economic viability. Together, these findings provide meaningful information for soil washing wastewater treatment with resource recovery.

Magnetic solid-phase extraction based on the Carbonized cotton fabric/zeolite imidazolate framework-71/Fe3O4/polythionine followed by atomic absorption spectrometry for cadmium monitoring in water, tomato and cabbage samples

Carbonized cotton fabric/zeolite imidazolate framework-71/Fe3O4/polythionine (CCF/ZIF-71/Fe3O4/PTh) was fabricated, characterized, and applied as efficient magnetic sorbent in magnetic solid-phase extraction (MSPE) of cadmium from water and food samples before determination by flame atomic absorption spectrometry (FAAS). This modification of carbonized cotton fabric led to making a great surface area and porosity, increase extraction efficiency, and acceptable selectivity. The characterization of this proposed sorbent was performed by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and Fourier transform-infrared (FT-IR) spectroscopy analysis techniques. The impact of several analytical parameters including pH, sorbent dosage, time of extraction, desorption condition, chelating agent concentration, the amount of salt and effect of potentially interfering ions on the selectivity and extraction recoveries of cadmium, were evaluated and optimized. In this proposed methodology, the limit of detection (LOD), the limit of quantification (LOQ), and relative standard deviation (RSD, n = 3) were found to be 0.21 ng mL−1, 0.6 ng mL−1 and lower than 3.0%, respectively. The validation and accuracy of the new advanced procedure were confirmed by applying the proposed procedure for certified reference materials (SRM1570A). Eventually, CCF/ZIF-71/Fe3O4/PTh can be utilized as a selective sorbent, for the rapid, accurate and sensitive determination of Cd (II) in the samples.

Enhanced Electroremediation of Metals from Dredged Marine Sediment under Periodic Voltage Using EDDS and Citric Acid

The electrokinetic remediation (EKR) method has been extensively considered for the removal of inorganic pollutants from contaminated dredged sediment. In addition, the use of chelating agents as electrolyte solutions has been beneficial in increasing the mobility of metals. This study investigated the metals’ (Cd, Cr, Cu, Pb, and Zn) mobilities by assessing the effect of two environmentally friendly chelating agents, ethylenediaminedisuccinic acid (EDDS) and citric acid (CA), in enhancing the EKR efficiency under a periodic voltage gradient. The results showed that, for the same concentration (0.1 mol L−1), CA is more suitable for enhancing the removal of Cr (67.83%), Cu (59.77%), and Pb (32.05%) by chelating and desorbing them from the sediment matrix and concentrating them in the electrode compartments. EDDS provided efficiency to improve the Cd extraction percentage (45.87%), whereas CA and EDDS had comparable improvement removal impacts on Zn EKR (39.32% and 41.37%, respectively). From the comparison with previous results obtained with a continuous voltage, applying a periodic voltage gradient associated with a low concentration of chelating agents led to a promising result.

Some metal binding properties of recombinant human lactoferrin from the milk of transgenic goats

In this research, the ability of pure recombinant human lactoferrin (rhLF), originated from the milk of transgenic goats, to bind ferric and europium ions has been shown by the methods of spectrophotometry, fluorescent spectroscopy, and inductively coupled plasma mass spectrometry. The apo-form of rhLF and its complexes with Fe3+ or Eu3+ saturated in 76 or 22 %, respectively, were obtained. A method for detection of total or released (“free”) lanthanide at acidic or neutral pH and high or low concentrations of chelating agents by time-resolved fluorescence was proposed.