Concentration Of Complexing Agent Research Articles

Experimental analysis and prediction of radionuclide solubility using machine learning models: Effects of organic complexing agents

Radioactive wastes contain organic complexing agents that can form complexes with radionuclides and enhance the solubility of these radionuclides, increasing the mobility of radionuclides over great distances from a radioactive waste repository. In this study, four radionuclides (cobalt, strontium, iodine, and uranium) and three organic complexing agents (ethylenediaminetetraacetic acid, nitrilotriacetic acid, and iso-saccharic acid) were selected, and the solubility of these radionuclides was assessed under realistic environmental conditions such as different pHs (7, 9, 11, and 13), temperatures (10 °C, 20 °C, and 40 °C), and organic complexing agent concentrations (10−5–10−2 M). A total of 720 datasets were generated from solubility batch experiments. Four supervised machine learning models such as the Gaussian process regression (GPR), ensemble-boosted trees, artificial neural networks, and support vector machine were developed for predicting the radionuclide solubility. Each ML model was optimized using Bayesian optimization algorithm. The GPR evolved as a robust model that provided accurate predictions within the underlying solubility patterns by capturing the intricate relationships of the independent parameters of the dataset. At an uncertainty level of 95%, both the experimental results and GPR simulated estimations were closely correlated, confirming the suitability of the GPR model for future explorations.

Efficacy and mechanism of copper removal from electroplating wastewater by schwertmannite-like mineral

To explore the key influencing factors of copper removal by schwertmannite-like mineral and its mechanism of action, a shake flask method was used to synthesize schwertmannite-like mineral by adding Na2SiO3 and CaCl2 in the synthesis process of schwertmannite. The results showed that increasing the initial pH value from 2.0 to 5.0 increased the copper removal rate by 30.18%, indicating that high pH value effectively promoted copper removal. However, increasing the complexing agent concentration from 0.7 to 1.5 mmol/L decreased the copper removal rate by 27.51%, implying that high complexing agent concentration significantly inhibited copper removal. At a temperature of 40 °C, pH of 5.0, coexisting ion concentration (Mg2+, K+, Na+) of 1.5 mmol/L, complexing agent concentration (EDTA-Na2) of 0.5 mmol/L, and copper content of 50 mg/L, the removal of copper was achieved with the addition of 0.5 g/L FeSO4·7 H2O, 1.01 mL/L H2O2, 0.58 g/L Na2SiO3, and 3.25 g/L CaCl2. Under these conditions, the removal of copper reached the highest level of 97.99%, which was 85.01% higher than that of schwertmannite. When the schwertmannite-like mineral was dissolved in 1 L of ultrapure water, the highest copper dissolving rate was 1.98%, which was 19.06% less than that of schwertmannite. Due to the synergy of several mechanisms, including adsorption and CaSiO3 co-precipitation, the schwertmannite-like mineral has better removal efficiency and stability than schwertmannite.

Optimization of Lithium Separation from NCA Leachate Solution: Investigating the Impact of Feed Concentration, Pressure, and Complexing Agent Concentration

Recycling lithium batteries (LIB) has emerged as an attractive solution in the global pursuit of environmentally friendly practices. The aim of achieving zero–waste hydrometallurgical technology is within reach. This research focuses on utilizing the low-pressure nanofiltration process to address this challenge by separating lithium ions from other ions and achieving a desirable permeate flux. The NCA battery leachate concentrate was obtained through a hydrometallurgical process involving sulfuric acid–peroxide. To ensure the prevention of potential nanofiltration membrane (TS80) fouling, the concentrate is initially filtered using an ultrafiltration membrane (UH004) to remove any particles. The research investigates the impact of pressure (4, 6, and 7 bar), solution concentration (concentrate, 10x, and 50x dilution), and the concentration of the complexing agent (EDTA) on the desired separation performance. The investigation reveals that pressure variations exhibit consistent rejection rates, remaining stable above 80%. A similar trend is observed with the addition of EDTA, which consistently yields rejection rates above 80%. However, when examining different feed concentrations, the rejection of lithium falls below 80% for leachate concentrates. In summary, satisfactory results are obtained by employing nanofiltration with a TS80 membrane at a pressure of 7 bar, a dilution factor of 10x, and using a 0.02M EDTA complexing agent. Meanwhile, it was found that the separation factors (Li⁺/Ni²⁺ = ~8.6, Li⁺/ Co²⁺ = ~7.3, Li⁺/Al³⁺ = ~4.9) and permeate flux ±46.58 L m⁻² h⁻¹. The findings demonstrate good selectivity along with relatively high flux.

Enhancing Trace Metal Extraction from Wastewater: Magnetic Activated Carbon as a High-Performance Sorbent for Inductively Coupled Plasma Optical Emission Spectrometry Analysis

A new fast, sensitive, and environmentally friendly analytical method has been developed for the simultaneous determination of Ba, Be, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, and Zn in wastewater samples using inductively coupled plasma optical emission spectroscopy (ICP OES). A preconcentration step using a magnetic dispersive solid-phase extraction (MDSPE) technique with a new magnetic sorbent was performed. The new sorbent material was a carbon containing magnetic cobalt and nitrogen groups. This material was synthetized using controlled pyrolysis of a zeolitic imidazolate framework (i.e., ZIF-67). In order to optimize the experimental parameters that affect the MDSPE procedure, a multivariate optimization strategy, using Plackett–Burman and circumscribed central composite designs (CCD), was used. The method has been evaluated employing optimized experimental conditions (i.e., sample weight, 10 g; sample pH, 7.6; amount of sorbent, 10 mg; dispersive agent, vortex; complexing agent concentration, 0.5%; ionic concentration, 0%; eluent, HCl; eluent concentration, 0.5 M; eluent volume, 300 μL; elution time, 3 min and extraction time, 3 min) using external calibration. Limits of detection (LODs) in a range from 0.073 to 1.3 μg L−1 were obtained, and the repeatability was evaluated at two different levels, resulting in relative standard deviations below 8% for both levels (n = 5). An increase in the sensitivity was observed due to the high enrichment factors (i.e., 3.2 to 13) obtained compared with direct ICP OES analysis. The method was also validated through carrying out recovery studies that employed a real wastewater sample and through the analysis of a certified reference material (ERM®-CA713). The recovery values obtained with the real wastewater were between 94 and 108% and between 90 and 109% for the analysis of ERM®-CA713, showing negligible matrix effects.

A thermochemical understanding of the factors that govern the growth of chemical bath deposition of Cu2O thin films

A simple room-temperature chemical bath deposition technique, inspired by the Felhling method, was used to deposit nanocrystalline cuprous oxide (Cu2O) thin films. The process involved a mixture of copper sulfate, sodium potassium tartrate, and sodium hydroxide. A thermochemical analysis explored how pH and complexing agent concentration affected Cu(OH)2 solubility and subsequent Cu2O growth using species repartition diagrams. The study is conducted by fixing the [tartrate]/[Cu] ratio at 10, while varying pH, deposition time, and temperatures from room temperature to 80 °C. While oxide nucleation and growth began at pH = 9, denser and more uniform films formed at pH = 10 and 11, corresponding to the co-existing domain of copper hydroxo and copper tartrate complexes. Notably, regardless of pH, temperature, or reducing agent, the Cu2O (111) facets appear to be selectively stabilized. The introduction of an aldehyde reducing agent such as glucose had little effect on the growth of Cu2O layers at room temperature but promoted the formation of Cu0 at 80 °C.

Electrochemical recycling of diamond and precious metals from used diamond tools

The recycling of used diamond tools, which contain a large amount of unused diamond particles and precious metals, can not only realize the reuse of resources, but also reduce the pressure of environmental protection. In this paper, diamond particles were recovered by acid dissolution of aqua regia, and the current density, complexing agent concentration and pH value of the acid dissolution system were adjusted to recover Cu and Co by electrodeposition. Scanning electron microscope and energy spectrometer were used to study the changes of the composition and morphology of the plated layers, and the effects of the parameters such as current density, complexing agent concentration and pH on the organization and composition of the alloy plated layers were analyzed. The results showed that at the current density of 40 mA/cm², pH 4.5 and complexing agent concentration of 10 g/L, uniformly distributed, dense and moderately thick Cu-Co alloy plating was obtained, and the weight percentages of Cu and Co reached the peak respectively. The Cu and Co in the waste diamond tools can be recovered under this condition with good recovery effect.

State and role of water confined in cement and composites modified with metakaolin and additives

Cement as a porous material contains pores and cracks on the whole nanoscale forming an interconnected pore structure. Its interaction with water during the rehydration of cement plays a key role in every application, such as in nuclear waste treatment, where cement binders are commonly used for conditioning liquid radioactive waste. In the prediction of the long-term disposal the knowledge of water mobility and distribution in the formed porous cement matrix is essential.In this study we systematically investigate the effects of metakaolin and several components of the liquid phase (complexing agents, model ions, boric acid, etc.) on the hydrated solid structure by various nuclear magnetic resonance (NMR) methods. The novelty lies in the complex use of such non-conventional techniques that separately provide only partial information of the cement structure; however, the gained results complete each other to offer a new approach in the structural study under several conditions. Water mobility is deduced from NMR T2 relaxation distributions and D2O-H2O exchange diffusion measurements, and the conclusion on structural properties is supported by the macropore structure revealed from NMR cryoporometry and SEM (scanning electron microscopy) images, as well as by following the formation of pores and water domains in the curing process with NMR relaxometry. The results confirm that metakaolin was built into the CSH (calcium silicate hydrate) gel region without altering its mesoporous structure, however, it significantly decreased the capillary pore size and the diffusion coefficient of water. Complexing agent concentration between 2 and 20 g/l and the presence of model ions did not cause significant structural changes, while the rehydration decreased the size of capillary pores due to swelling.

Extraction and preconcentration of vanadium from food samples using aqueous two-phase systems by a multivariate study

Vanadium plays essential and toxic roles in humans and in nature, depending on its concentration. Therefore, monitoring its concentration in food samples is important, as this analyte is usually found in trace amounts in these samples. In this context, this work proposes a new methodology for the determination of vanadium in food samples using an aqueous two-phase system formed by (NH4)2SO4 + PEG400 + H2O with the complexing agent Br-PADAP to extract and pre-concentrate the analyte in the top-phase with detection by atomic absorption spectrometry. Multivariate analysis using fractional factorial design was applied to define the significant variables and a Box-Behnken matrix was used to find the critical points for these variables, which defined as pH 3.60, an ultra-thermostatted bath time of 2.12 h and complexing agent concentration of 0.00810 100w. Under optimised extraction conditions, the method presented limits of detection and quantification of 0.0220 μg⸳kg-1 and 0.665 μg.kg-1, respectively; accuracy of 2.51% and enrichment factor of 19.1. The methodology was applied to certified reference samples of apple leaves (NIST1515) and food samples with recovery percentages values of 94.1% and 93.8-108%, respectively. Therefore, a novel, efficient and organic solvent-free methodology was developed for the determination of vanadium in food samples.

Effect of complexing agent concentration on properties of CdZnS thin films in ammonia-thiourea system

Effect of complexing agent concentration on properties of CdZnS thin films in ammonia-thiourea system

Microstructure and electrical conductivity of electroless copper plating layer on magnesium alloy micro-arc oxidation coating

In order to impart electrical conductivity to the magnesium alloy micro-arc oxidation (MAO) coating, the electroless copper plating was performed. Effects of plating temperature and complexing agent concentration on the properties of the electroless copper plating layers were studied by measuring their microstructure, corrosion resistance and electrical conductivity. It was found that the optimized plating temperature was 60 °C, and the most suitable value of the complexing agent concentration was 30 g/L. Under this condition, a complete and dense plating layer could be obtained. The formation mechanism of the plating layer on magnesium alloy MAO coating was analyzed. A three-stage model of the plating process was proposed. The square resistance of the plated specimen was finally reduced to 0.03 Ω/□ after the third stage. Through electroless copper plating, the MAO coated sample obtained excellent electrical conductivity without significantly reducing its corrosion resistance.

Enhanced photoelectrochemical water splitting performance of vertically aligned Bi2O3 nanosheet arrays derived from chemical bath deposition method by controlling chemical bath temperature and complexing agent concentration

Introduction of nanotechnology to the issue of photoelectrode fabrication is promising enough to overcome the difficulties of developing photoelectrochemical water splitting. In the recent past, photoelectrodes based on two-dimensional materials, particularly those with nanosheets less than 100 nm thick, received considerable attention. In this study, the Chemical Bath Deposition (CBD) method was employed to prepare vertically aligned Bi2O3 nanosheet arrays on FTO-coated glass substarate. Experiments were carried out to determine the impact of changing the parameters of the CBD method, i.e., bath temperature and complexing agent concentration, on the physical and photoelectrochemical properties of Bi2O3 nanosheet coatings. The samples were characterized by X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), UV-visible spectroscopy, Photoluminescence spectroscopy (PL), Raman spectroscopy, Linear Sweep Voltammetry (LSV) under light-chopped illumination, and Electrochemical Impedance Spectroscopy (EIS). Experimental results demonstrated that the bath temperature was effective in the physical properties of Bi2O3 coatings so that upon increasing the bath temperature from 45 °C to 60 °C, the size of nanosheets and the thickness of coating increased and the electrochemically active surface area dramatically decreased and the bandgap of coatings changed from 2.63 eV to 2.31 eV. However, further increase in the bath temperature up to 75 °C led to a reduction of electrochemically active surface area and an increase in the size of nanosheets, in the thickness of the coating, and in the bandgap to 2.49 eV. The photoelectrode obtained from the chemical bath at a temperature of 60 °C exhibited the highest photocurrent density of 470 μA/cm2 at 1.2 VRHE, which is mainly attributed to its lowest charge transfer resistance and the narrowest bandgap. Using low concentrations of complexing agent, triethanolamine (TEA) in a chemical bath did not provide coating on a substrate. Less compact and intertwined Bi2O3 nanosheet arrays and a more crystallized and porous coating were formed with an increment in TEA. The density of photocurrents varied at the molar ratio of TEA to bismuth ion in the order of 4 > 6 > 3, which is ascribed to their physical properties, charge generation, and transfer abilities. Among the Bi2O3 nanosheet photoelectrodes, the sample that was prepared in the chemical bath at 60 °C at a TEA to bismuth ions molar ratio of 4 had the highest photocurrent density of 750 μA/cm2 at 1.2 VRHE.

Determination of Metal Ions in Pinellia ternata by High Performance Liquid Chromatography-Ultraviolet Detector

In this study, trace amounts of heavy metal ions copper, lead, mercury and cobalt in Pinellia ternata samples were detected by ionic liquid ultrasonic assisted dispersion liquid–liquid microextraction, combined with high performance liquid chromatography-ultraviolet detector. The method used sodium diethyldithiocarbamate as complexing agent and phosphoric acid ionic liquid Trihexyl(tetradecyl) phosphine bis[(2,4,4-trimethyl)] amyl phosphonate (cyclophosphate IL104) as extractant. Methanol: 0.2% phosphoric acid (60:40) was used as mobile phase for separation and UV detector was used for detection, the flow rate was 1 mL/min and the injection volume was 10 μL. In this paper, the effects of sample pH, complexing agent concentration, ultrasonic time, centrifugation time and speed and ionic strength were optimized. Under the optimal conditions (50 μL ionic liquid cyclic phosphine IL104, pH = 5, 0.5% sodium diethyldithiocarbamate, ultrasonic time of 30 min, centrifugation speed of 4000 r/min, 0.1 g NaCl), the recovery of spiked standard was 89.0~98.2%. High performance liquid chromatography had the characteristics of low detection limit, accurate and reliable determination results, high sensitivity, strong specificity and good reproducibility.

Single-step electrodeposition of CZTS thin film: Influence of complexing agent concentration

Single-step electrodeposition of CZTS thin film: Influence of complexing agent concentration

Effect of complex agent concentration on the structural and morphological properties of CuAlS2 thin films prepared by chemical bath deposition technique

CuAlS2 thin films have been prepared on glass substrates by chemical bath deposition (CBD) technique at a substrate temperature (Ts) 75C, pH value 10.5, and fixed deposition time 40 minutes. In this study effect of molar concentrations (0.03, 0.05, and 0.06 M) of complex agent Na2EDTA on structural, morphological, and topological properties of deposit thin films were studied by using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) with cross section, and atomic force microscopy (AFM), respectively. The result showed that all prepared films were amorphous structures. The cross section analysis showed a good adhesion between prepared films and glass substrates, average thickness of films was affected by concentration of complex agent, where was low at 0.03 and 0.06 M, while was high at 0.05 M. The prepared films showed homogenous and uniform spherical nanoparticles with average grain size (64 to 79 nm) increased with increasing complex agent concentration. AFM images showed that the prepared films at 0.05 and 0.06 M had the same structures as conical and spherical shapes with the homogenous distribution on the surface of the films compared with that at 0.03 M. Also, the surface roughness, and root mean square (rms) roughness were varied in the range (0.33 to 1.74 nm) and (0.44 to 2.34 nm), respectively, where the less roughness were found at 0.05 M complex agent. The prepared films at 0.05 M complex agent showed the best properties which can be useful for many applications in optoelectronics devices.

Hydrometallurgical Processing of Gold-Containing Ore and its Enrichment Products

This research focuses on the hydrometallurgical processing of auriferous ores and their processing products, namely, flotation and gravity concentrates. The main valuable component of an ore sample of any deposit is gold. The gold content should be in the range of 11.11–12.87 g/ton. The main rock-forming minerals of the original ore are quartz (60.1%), quartz–chlorite–micaceous aggregates (3.8%), and carbonates (7.1%). In this study, original ores of various sizes were treated by direct and sorption cyanidation under various leaching modes, and the results obtained were presented. The original ore was leached with various concentrations of sodium cyanide (NaCN) in solution to study the effect of the complexing agent concentration on gold recovery. Data on the dynamics of leaching revealed that a decrease in the concentration of NaCN in solution from 0.2% to 0.03% leads to a decrease in gold recovery in solution by 26.81%. Original ores could easily be processed using hydrometallurgical methods. The recovery of gold with a coarseness of 95% − 0.045 mm from the original ore averaged 97.77%. This work features a full range of studies on the hydrometallurgical processing of concentrates and gravity tailings, as well as the effects of flotation concentration of gold recovery. The gravity concentrate is resistant to intensive cyanidation (i.e., only 67.07% gold recovery into the solution). The use of 1% lead nitrate (PbNO3) during intensive cyanidation could reduce the refractoriness of the concentrate and increase the recovery of gold into the solution by up to 94.35%. The total gold recovery from gravity concentrate is 98.71%, and the recovery of gold by cyanidation of gravity tailings with a cyanide concentration of 0.2% averages 96.57%. The recovery of gold during leaching of the flotation concentrate at the original size (95.5% − 0.074 mm) and a cyanide concentration of 0.2% is 96.64%. A decrease in the size of the flotation concentrate from 95.5% − 0.074 mm to 95% − 0.02 mm leads to a decrease in gold recovery by 35.43% because of the strong chemical activation of the material during grinding.

Full Optimization of an Electroless Nickel Solution: Boosting the Performance of Low-Phosphorous Coatings.

Univariate and multivariate optimizations of a novel electroless nickel formulation have been carried out by means of the Taguchi method. From the compositional point of view, adjustment of the complexing agent concentration in solution is crucial for fine-tuning free Ni2+ ions concentration and, in turn, the mechanical properties of the resulting coatings. The Ni (II) concentration and the pH are the main parameters which help restrict the incorporation of phosphorous into the Ni layers. On the other hand, the stirring rate, the pH and the reducing agent concentration are the most influential parameters for the corrosion resistance of the coatings. Multivariate optimization of the electrolyte leads to a set of optimized parameters in which the mechanical properties (hardness and worn volume) of the layers are similar to the optimal values achieved in the univariate optimization, but the corrosion rate is decreased by one order of magnitude.

Application of Various Iron-Based Plated Electrodes Under Different Plating Conditions As Air Electrodes for Metal-Air Batteries

The purpose of this study was to investigate the difference in oxygen evolution and reduction reaction activity by changing the preparation conditions of Fe-Ni-W alloy plating. We produced Fe-Ni-W alloy plating that changed the concentration of Fe and W ions in the bath. It was described that the activity for oxygen evolution reaction (OER) depended on the containing W amount in the film, and also depended on the concentration of complex agent, Na3Cit･2H2O in the bath. When the concentration of Na3Cit･2H2O in the bath increased, the content of Fe-W in the film increased, and the Ni content decreased. It was found that the plated electrode with morphological large surface area showed good performance. In the case of oxygen reduction reaction (ORR), it was described that the activity depended on the contents of W in the film.

Feasibility of Dispersive Liquid–Liquid Microextraction for Molybdenum Determination in Lamb Meat by MIP OES

The dispersive liquid–liquid microextraction (DLLME) was evaluated as a strategy to improve the MIP OES sensitivity for molybdenum determination in lamb meat. Initially, the dispersive (methanol) and extracting (tetrachloromethane) solvents were selected based on a mixture design. The best results were achieved with methanol and carbon tetrachloride as dispersive and extracting solvent, respectively. The operational parameters, such as pH, volume of dispersive and extractant solvents, and complexing agent concentration (8-hydroxyquinoline) were optimized using a Box-Behnken design. The optimal conditions were established as pH 3.8, 90 μL of carbon tetrachloride, 480 μL of methanol, and 1.09 mmol L-1 of 8-hydroxyquinoline. Besides, the use of external gas module control (EGCM) was explored to minimize the matrix effects caused by the organic solvent introduction. The accuracy of the proposed method was estimated employing a certificate reference material (bovine liver, NIST 1577c) and the obtained recovery was 92%. The limit of detection was found to be 0.20 μg g-1, and the enrichment factor was 4.5. The DLLME-MIP OES was applied for six samples of lamb meat, and the results compared to ICP-MS presented no statistical difference. Therefore, the proposed method showed satisfactory accuracy and suitable sensitivity.

PH-dependent antioxidant stability of black rice anthocyanin complexed with cycloamylose

This study investigated the effects of cycloamylose (CA) as a complexing agent on the antioxidant activity and stability of anthocyanin extracted from black rice (BRA) at various pHs (2, 4, 6, and 8) and compared the results with those of β-cyclodextrin (βCD). The CA (DP 6–31) produced from Dodamssal rice starch had an anti-copigmentation effect for BRA and the discoloration effect increased with the complexing agent concentration, which supported the intramolecular interaction between them. With heat treatment, the CA-BRA complex had a greater antioxidant stability than did free BRA at pHs 4, 6, and 8 in a concentration-dependent manner. In particular, BRA complexed with 1% CA at pH 4 had an approximately 2.0-fold lower degradation rate (kd) than that of free BRA. This improvement in the thermal stability was comparable to or slightly better than that of 5% βCD. CA significantly improved the photostability of BRA at all pHs tested, similarly to βCD. CA might protect the moiety of BRA functional groups that are involved in antioxidant activity and susceptible to heat and light. The results demonstrated that CA could be an effective complexing agent for BRA and the stable CA-BRA complex could be used as a promising functional material for the various industries.

Application of a solid lead microelectrode as a new voltammetric sensor for adsorptive stripping voltammetry of U(VI)

For the first time solid lead microelectrode was utilized for analytical purposes: the article reports on its application for adsorptive stripping voltammetric determination of U(VI) ions. The proposed solid metal microelectrode of a diameter of 25 μm contains about 30 μg of metallic lead that significantly restricts amount of toxic lead introduced into the environment in comparison to lead film equivalents. The potential window of the proposed sensor was checked by means of cyclic voltammetry. The optimization of the analytical procedure of determination of U(VI) ions complexed with cupferron was performed. The experimental parameters (potential of microelectrode activation, pH of supporting electrolyte, complexing agent concentration, potential and time of accumulation and effects of possible interferences) were studied. A linear calibration graph for U(VI) determination was linear in the range from 2 × 10−9 to 1 × 10−7 mol L−1 (accumulation time of 120 s). The obtained detection limit for uranium ions determination following accumulation time of 120 s was 5.5 × 10−10 mol L−1. Repeatability of the method calculated as RSD % for U(VI) concentration of 2 × 10−8 mol L−1 was 4.7% (n = 5). The proposed procedure was successfully applied for U(VI) ions determination in lake water certified reference material that confirms analytical application.