Concentration Of Chelating Agent Research Articles

Effect of chelating agent concentration in alkaline Cu CMP process under the condition of different applied pressures

We propose the action mechanism of Cu chemical mechanical planarization (CMP) in an alkaline solution. Meanwhile, the effect of abrasive mass fraction on the copper removal rate and within wafer non-uniformity (WIWNU) have been researched. In addition, we have also investigated the synergistic effect between the applied pressure and the FA/O chelating agent on the copper removal rate and WIWNU in the CMP process. Based on the experimental results, we chose several concentrations of the FA/O chelating agent, which added in the slurry can obtain a relatively high removal rate and a low WIWNU after polishing, to investigate the planarization performance of the copper slurry under different applied pressure conditions. The results demonstrate that the copper removal rate can reach 6125 Å/min when the abrasive concentration is 3 wt.%. From the planarization experimental results, we can see that the residual step height is 562 Å after excessive copper of the wafer surface is eliminated. It denotes that a good polishing result is acquired when the FA/O chelating agent concentration and applied pressure are fixed at 3 vol% and 1 psi, respectively. All the results set forth here are very valuable for the research and development of alkaline slurry.

Effective removal of heavy metals from industrial sludge with the aid of a biodegradable chelating ligand GLDA

Tetrasodium of N,N-bis(carboxymethyl) glutamic acid (GLDA), a novel readily biodegradable chelating ligand, was employed for the first time to remove heavy metals from industrial sludge generated from a local battery company. The extraction of cadmium, nickel, copper, and zinc from battery sludge with the presence of GLDA was studied under different experimental conditions such as contact times, pH values, as well as GLDA concentrations. Species distribution of metals in the sludge sample before and after extraction with GLDA was also analyzed. Current investigation showed that (i) GLDA was effective for Cd extraction from sludge samples under various conditions. (ii) About 89% cadmium, 82% nickel and 84% copper content could be effectively extracted at the molar ratio of GLDA:M(II)=3:1 and at pH=4, whereas the removal efficiency of zinc was quite low throughout the experiment. (iii) A variety of parameters, such as contact time, pH values, the concentration of chelating agent, stability constant, as well as species distribution of metals could affect the chelating properties of GLDA.

Slurry components of TiO2 thin film in chemical mechanical polishing

A chemical mechanical polishing (CMP) process was selected to smooth TiO2 thin film surface and improve the removal rate. Meanwhile, the optimal process conditions were used in TiO2 thin film CMP. The effects of silica sols concentration, slurry pH, chelating agent and active agent concentration on surface roughness and material removal rate were investigated. Our experimental results indicated that we got lower surface roughness (1.26 Å, the scanned area was 10 × 10 μm2) and higher polishing rate (65.6 nm/min), the optimal parameters were: silica sols concentration 8.0%, pH value 9.0, active agent concentration 50 mL/L, chelating agent concentration 10 mL/L, respectively.

Effect of chelating agent on benzotriazole removal during post copper chemical mechanical polishing cleaning

During the chemical mechanical polishing (CMP) process of copper, benzotriazole (BTA) is the most commonly used inhibitor, especially in acidic slurry. The post CMP cleaning process is mainly removal of slurry particles and organic residues. The presence of BTA results in a hydrophobic surface of copper, which leads to difficulty in cleaning, and BTA is the main organic residue. The BTA on the copper surface should be removed by using an effective cleaning solution. In this paper, a novel alkaline chelating agent with functionalities of BTA removal was designed for advanced post CMP cleaning solution. The alkaline chelating agent was used as main composition of cleaning agent. When the chelating agent concentration is 100–150ppm, it can effectively remove Cu–BTA. The removal of BTA is characterized by contact angle measurement, electrochemical methods and static etching rate (SER) measurement. The corrosion protection ability of the cleaning solutions was quantified by potentiodynamic polarization studies. Atomic force microscopy (AFM) measurement was used to monitor the surface quality of copper after cleaning.

Prevention and control of struvite and calcium phosphate precipitation by chelating agents

The problems stemming from struvite precipitation on pipe walls, valves, faucets, and propellers in the anaerobic sludge digestion processes of wastewater treatment plants have been extensively reported. In addition to the diverse sources of the struvite-forming ions (Mg2+, NH4+, and PO43-) present in its wastewaters, Israel has hard water with characteristic high concentrations of Ca2+ that causes the formation of calcium phosphate on plant equipment. This study focuses on the use of chelating agents to control struvite and calcium phosphate precipitation. The reaction conditions required to prevent the precipitation of either salt by ethylenediaminetetraacetic acid or nitrilotriacetic acid and for the selective precipitation of struvite after calcium chelation are reported. Both chelating agents promoted the chelation in solution of Ca2+ over that of Mg2+. In contrast, for precipitated calcium phosphate and struvite, higher chelating agent concentrations were required to dissolve the former than the latter. The amounts of both chelating agents, added in proper concentrations, were sufficient to bind mainly the Ca2+ ions, thus preventing the precipitation of Ca3(PO4)2 and leaving more phosphate ions available to precipitate Mg2+ ions as struvite. Performed properly, this process will remove Ca2+ and Mg2+ ions from the supernatant. In addition, after separation, the struvite can be collected and used as fertilizer. The potential toxicity of both chelating agents to the biomass was also studied in this work.

Effect of chelating agent on oxidation rate of aniline in ferrous ion activated persulfate system at neutral pH

In the interest of accelerating aniline degradation, Fe2+ and chelated Fe2+ activated persulfate oxidations were investigated in neutral pH condition. Three kinds of chelating agents were selected including citric acid, oxalic acid and ethylenediamine tetraaceatate (EDTA) to maintain available Fe2+. The results indicate that the concentration of chelating agent and ferrous ion didn’t follow a linear relationship with the degradation rate of aniline. A 1/1 ratio of chelating agent/Fe2+ results in a higher degradation rate compared to the results by other ratios. The oxidation enhancement factor using oxalic acid was found to be relatively low. In contrast, citric acid is more suitable chelating agent in the ferrous iron activated persulfate system and aniline exhibits a highest degradation with a persulfate/Fe2+/citric acid/aniline molar ratio of 50/25/25/1 compared to other molar ratios.

An Investigation on Heavy Metals Bio-Sorption by Azolla filiculoides in the International Anzali Wetland

The ultrasound assisted emulsification microextraction (USAEME) method followed by inductively coupled plasma-atomic emission spectrometry (ICP-AES) was used for preconcentration and determination of bismuth (Bi), indium (In) and lead (Pb) in the plant Azolla filiculoides Lam. Calix (4) pyrrole was used as a chelating agent and tetrachloroethylene was selected as extraction solvent. The main parameters of the USAEME method were optimized by using response surface methodology (RSM). The optimal conditions were as follows: 130 µL for volume of extraction solvent, 4 min for sonication time, 6.75 (w/v %) for salt concentration, 890 mg/L for concentration of chelating agent and 7.5 for pH. The calibration graphs were linear in the range of 1-1500 µg/L for Bi and In, and 1-1000 µg/L for Pb with the determination coefficients (R 2 ) of 0.9983, 0.9974 and 0.9997, respectively. The limits of detection (LODs) for Bi, In and Pb were 0.57, 0.76 and 0.84 µg/L, respectively. Under the optimal conditions, the method was successfully applied to the determination of Bi, In and Pb in Azolla filiculoides Lam. tissues in Anzali wetland and satisfactory relative recoveries (94-97%) were achieved.

COMPARISON OF EDTA AND EDDS ENHANCTED PHYTOEXTRACTION OF Cr AND Pb FROM CONTAMINATED SOIL BY <i>ANANAS COMOSUS</i> (L.) MERR.

The effects of chelating agents on Chromium (Cr) and lead (Pb) absorption were studied by planting pineapple, Ananas comosus (L.) Merr. in contaminated soil. All plant samples were grown in a nursery for 30 days and then separated into seven sets: Set (1) had nothing added (Blank); (2) had Pb added as Pb(II) Nitrate (Pb(NO3)2) at 500 mg kg-1 soil; (3) added Pb(II) nitrate and EDTA, a chelating agent; (4) contained both Pb(II) nitrate and EDDS, a second chelating agent; (5) only added Cr as potassium dichromate (K2Cr2O7), at 400 mg kg-1 soil; (6) was treated with Cr (potassium dichromate) plus EDTA; and (7) contained both Cr (potassium dichromate) and EDDS. The chelating agent concentrations were 2 millimoles per kilogram soil. Soil and plant contamination levels were measured by analyzing the Cr, Cr(VI) and total Pb after growing for 30, 60, 90 and 120 days. The analysis divided the plant samples into two parts: Aboveground and underground. Plant growth was also analyzed by dry weight, root length and expression of toxicity through withered leaves and yellow leaf symptoms. The results of this study indicate that after 60 days, the EDTA agent had the highest Pb absorption efficiency, with the plant sample absorbing 288.14 mg Pb per kg soil in the aboveground part and 796.66 mg kg-1 soil in the underground part. The EDTA agent had high Cr absorption efficiency, with the plant sample absorbing Cr at 545.72 mg kg-1 soil in the aboveground part and 2267.99 mg kg-1 soil in the underground part after 90 days. The EDTA and EDDS agents did not affect pineapple growth and expression of toxicity symptoms were statistically significant (p≤0.05) compared with the control sets.

Evaluation of dispersive liquid-liquid microextraction for the determination of cobalt and cadmium by flame atomic absorption spectrometry: application in water and food samples

AbstractDispersive liquid-liquid microextraction (DLLME) was applied to the separation and preconcentration of Cd(II) and Co(II) from water and food samples. The influence of the following analytical parameters on the quantitative recoveries of cadmium and cobalt were investigated: pH, extraction solvent volume, dispersing solvent volume and type, and concentration of chelating agent. Under the optimized conditions, the detection limits were 2 μg L

Preconcentration and Determination of Cadmium in Water and Food Samples byin situSurfactant-Based Solid-Phase Extraction and Flame Atomic Absorption Spectrometry

In situ surfactant-based solid-phase extraction (ISS-SPE) is proposed as a preconcentration procedure for the determination of cadmium in water and food samples by flame atomic absorption spectrometry. In the present work, cetyltrimethylammonium bromide was used as a cationic surfactant, hexafluorophosphate ion as an ion-pairing agent and 4-benzylpiperidinedithiocarbamate potassium salt (K-4-BPDC) as a chelating agent. Several variables that affect the extraction efficiencies such as pH, type and amount of surfactant, concentration of ion-pairing agent, concentration of chelating agent, ionic strength and extraction time were investigated and optimized. After optimization of the complexation and extraction conditions, an enrichment factor of 40 was obtained. The calibration curve was linear in the range of 1-50 µg L-1 and the limit of detection was 0.3 µg L-1. The relative standard deviation for 20 µg L-1 of cadmium was lower than 2.2%. Validation of the methodology was performed by standard addition method and analysis of certified reference materials. The method was successfully applied to the determination of cadmium in various food and water samples.

Efficiency of non-ionic surfactants - EDTA for treating TPH and heavy metals from contaminated soil

Introduction of fuel hydrocarbons and inorganic compounds (heavy metals) into the soil, resulting in a change of the soil quality, which is likely to affect use of the soil or endangering public health and ground water. This study aimed to determine a series of parameters to remediation of TPH and heavy metals contaminated soil by non-ionic surfactants- chelating agents washing process. In this experimental study, the effects of soil washing time, agitation speed, concentration of surfactant, chelating agent and pH on the removal efficiency were studied. The results showed that TPH removal by nonionic surfactants (Tween 80, Brij 35) in optimal condition were 70–80% and 60–65%, respectively. Addition of chelating agent (EDTA) significantly increases Cd and Pb removal. The washing of soil by non- ionic surfactants and EDTA was effective in remediation of TPH and heavy metals from contaminated soil, thus it can be recommended for remediation of contaminated soil.

Supramolecular solvent-based extraction coupled with vortex-mixing for determination of palladium and silver in water samples by flame atomic absorption spectrometry

A simple and practical extraction method of supramolecular solvents (SUPRAS) was developed for separation and enrichment of trace amounts of palladium (Pd) and silver (Ag) in water samples prior to flame atomic absorption spectrometry (FAAS) analysis. The SUPRAS selected was made up of an aqueous solution containing tetrahydrofuran and nonanoic acid. Pd and Ag reacted with diethyldithiocarbamate to form hydrophobic chelates, which were extracted into the vesicles of SUPRAS. Different parameters such as the concentration of chelating agent, sample pH, supramolecular solvent and the effect of foreign ions were studied. Under the optimal conditions, the linear ranges of Pd and Ag were from 10 to 1,000 μg/L. The relative recoveries of Pd and Ag in tap and river water samples at the spiking level of 10 ug/mL ranged from 90.8 to 116%. The relative standard deviations were 3.6-4.0% (n = 9), the limits of detection were 2.8 and 1.9 μg/L and the enrichment factors were 36 and 18 for Pd and Ag, respectively. The quantification limits were 3.2 and 2.4 μg/L. The method was successfully applied to the determination of Pd and Ag in water samples.

Optimized Ultrasound‐Assisted Emulsification‐Microextraction Followed by ICP‐OES for Simultaneous Determination of Ytterbium and Holmium in Natural Water

In this study, the optimized ultrasound‐assisted emulsification‐microextraction followed by inductively coupled plasma‐optical emission spectrometry was applied to simultaneous extraction and determination of holmium (Ho3+) and ytterbium (Yb3+) in water samples. 1‐(2‐Pyridylazo)‐2‐naphthol was used as chelating agent to form extractable complexes. Volume of extraction solvent, concentration of chelating agent, pH, ultrasonic time, temperature, and concentration of salt were considered as the variables of the method. To evaluate the results, extraction recovery was selected as the response. Significance of the variables was investigated by using a half‐fraction factorial design (2f−1) and the optimization was performed by applying a central composite design. The calibration graphs were linear in the range of 4–200 µg L−1 for Ho3+ and 3–500 µg L−1 for Yb3+ with determination coefficients (R2) of 0.988 and 0.997 for Ho3+ and Yb3+, respectively. Limit of detection was 0.364 µg L−1 for Ho3+ and 0.252 µg L−1 for Yb3+. The relative standard deviations (C = 200 µg L−1, n = 6) were in the range of 4.2–4.5%. The method was successfully applied to the analysis of real water samples with the recoveries in the range of 80–95%.

Study on New Tea Soap Based Chelating Agent Synthetic Materials and the Repairing Effect of Heavy Metal Pollution in Environment

By water extraction, precipitation method we can extract tea saponin from tea seed cake and design and synthesize the new green tea soap based chelating agent in the synthesis design (tea saponin sodium sulfate). Study on the surface properties, the surface tension is lower than the tea saponin, and the value of HLB, foaming ability and foam stability are better than that of tea saponin. At the same time, considering the effects of heavy metal rate oscillation time, chelating agent concentration, pH and ionic strength on the chelating agent to remove, the results show that with the increase of oscillation, the removal rate and time of heavy metal concentration increase, and decrease with the increase of ionic strength and pH, thus concluding the optimum process of the removal of pb2+, cd2+ ions: the oscillation time is 12h, the mass fraction is 7%,the concentration of Ca (NO3)2 is 5.0, 0.01mol/L. Under this condition, ion removal rate of pb2+, cd2+ ions is the highest. The removal rate of tea saponin sodium sulfate ion on Cd2 is higher than Pb2 + ions, and these two kinds of tea saponin sodium sulfate ion removal rate are higher than that of tea saponin, improvement effect is obvious especially for Pb2 + ion removal rate.

Solvent-assisted dispersive solid phase extraction

In this research, a novel extraction technique termed solvent-assisted dispersive solid phase extraction (SADSPE) was developed for the first time. The new method was based on the dispersion of the sorbent into the sample to maximize the contact surface. In this method, the dispersion of the sorbent at a very low milligram level was achieved by injecting a solution of the sorbent into the aqueous sample. Thereby, a cloudy solution formed. The cloudy state resulted from the dispersion of the fine particles of the sorbent in the bulk aqueous sample. After extraction, phase separation was performed by centrifugation and the enriched analyte in the sedimented phase could be determined by instrumental methods. The performance of SADSPE was illustrated with the determination of the trace amounts of cobalt(II) as a test analyte in food and environmental water samples by using flame atomic absorption spectrometry detection. Some key parameters for SADSPE, such as sorbent selection and amount, type and volume of dispersive solvent, pH, chelating agent concentration, and salt concentration, were investigated. Under the most favorable conditions, good limit of detection (as low as 0.2µgL−1) and repeatability of extraction (RSD below 2.2%, n=10) was obtained. The accuracy of the method was tested with standard reference material (SRM-1643e and SRM-1640a) and spiked addition. The advantages of SADSPE method are simplicity of operation, rapidity, low cost, high recovery, and enrichment factor.

Speciation of platinum in blood plasma and urine by micelle-mediated extraction and graphite furnace atomic absorption spectrometry

A highly sensitive and selective technique for the speciation of platinum by cloud point extraction prior to determination by graphite furnace atomic absorption spectrometry (GFAAS) was described. The separation of Pt(II) from Pt(IV) was performed in the presence of 4-(p-chlorophenyl)-1-(pyridin-2-yl)thiosemicarbazide (HCPTS) as chelating agent and Triton X-114 as a non-ionic surfactant. The extraction of Pt(II)–HCPTS complex needs temperature higher than the cloud point temperature of Triton X-114 and pH=7, while Pt(IV) remains in the aqueous phase. The Pt(II) in the surfactant phase was analyzed by GFAAS, and the concentration of Pt(IV) was calculated by subtraction of Pt(II) from total platinum which was directly determined by GFAAS. The effect of pH, concentration of chelating agent, surfactant, and equilibration temperature were investigated. An enrichment factor of 42 was obtained for the preconcentration of Pt(II) with 50mL solution. Under the optimum experimental conditions, the calibration curve was linear up to 30μgL−1 with detection limit of 0.08μgL−1 and the relative standard deviation was 1.8%. No considerable interference was observed due to the presence of coexisting anions and cations. The accuracy of the results was verified by analyzing different spiked samples (tap water, blood plasma and urine). The proposed method was applied to the speciation analysis of Pt in blood plasma and urine with satisfactory results.

Role of messenger RNA–ribosome complex in complementary DNA display

In vitro display technologies such as ribosome display and messenger RNA (mRNA)/complementary DNA (cDNA) display are powerful methods that can generate library diversities on the order of 1010–14. However, in mRNA and cDNA display methods, the end use diversity is two orders of magnitude lower than initial diversity and is dependent on the downstream processes that act as limiting factors. We found that in our previous cDNA display protocol, the purification of protein fusions by the use of streptavidin matrices from cell-free translation mixtures had poor efficiency (∼10–15%) that seriously affected the diversity of the purified library. Here, we have investigated and optimized the protocols that provided remarkable purification efficiencies. The stalled ribosome in the mRNA–ribosome complex was found to impede this purification efficiency. Among the various conditions tested, destabilization of ribosomes by appropriate concentration of metal chelating agents in combination with an optimal temperature of 30°C were found to be crucial and effective for nearly complete isolation of protein fusions from the cell-free translation system. Thus, this protocol provided 8- to 10-fold increased efficiency of purification over the previous method and results in retaining the diversity of the library by approximately an order of magnitude—important for directed evolution. We also discuss the possible effects in the fabrication of protein chips.

Synthesis of Lix[Ni0.225Co0.125Mn0.65]O2 as a positive electrode for lithium-ion batteries by optimizing its synthesis conditions via a hydroxide co-precipitation method

Lix[Ni0.225Co0.125Mn0.65]O2 cathode material for a lithium-ion battery was synthesized from metal hydroxide Ni0.225Co0.125Mn0.65(OH)2. The co-precipitated metal hydroxide was greatly influenced by synthesis conditions of pH, concentration of chelating agent, stirring speed, and co-precipitation temperature. The conditions were optimized by observing the spherical and uniform particles, as examined by scanning electron microscopy. The optimized pH, ammonia concentration stirring speed and co-precipitation temperature were determined to be 11–12, 0.36M, 1000rpm and 50°C, respectively. The final products, Lix[Ni0.225Co0.125Mn0.65]O2 had a well-ordered hexagonal super lattice layered structure as established by Rietveld refinement of X-ray diffraction pattern. As a result, the Lix[Ni0.225Co0.125Mn0.65]O2 compound may be considered as a excellent candidate for cathode material of Lithium secondary battery in terms of cycle life, both safety and energy density, lower cost and low environmental impact.

Principles of multiparametric optimization for phospholipidomics by 31P NMR spectroscopy.

Phospholipids have long been known to be the principal constituents of the bilayer matrix of cell membranes. While the main function of cell membranes is to provide physical separation between intracellular and extracellular compartments, further biological and biochemical functions for phospholipids have been identified more recently, notably in cell signaling, cell recognition and cell-cell interaction, but also in cell growth, electrical insulation of neurons and many other processes. Therefore, accurate and efficient determination of tissue phospholipid composition is essential for our understanding of biological tissue function. 31P NMR spectroscopy is a quantitative and fast method for analyzing phospholipid extracts from biological samples without prior separation. However, the number of phospholipid classes and subclasses that can be quantified separately and reliably in 31P NMR spectra of tissue extracts is critically dependent on a variety of experimental conditions. Until recently, little attention has been paid to the optimization of phospholipid 31P NMR spectra. This review surveys the basic physicochemical properties that determine the quality of phospholipid spectra, and describes an optimization strategy based on this assessment. Notably, the following experimental parameters need to be controlled for systematic optimization: (1) extract concentration, (2) concentration of chelating agent, (3) pH value of the aqueous component of the solvent system, and (4) temperature of the NMR measurement. We conclude that a multiparametric optimization approach is crucial to obtaining highly predictable and reproducible 31P NMR spectra of phospholipids.

Enhancing radium solubilization in soils by citrate, EDTA, and EDDS chelating amendments

The effect of three chelating agents (citrate, EDTA, and EDDS) on the solubilization of radium from a granitic soil was studied systematically, considering different soil pH values, chelating agent concentrations, and leaching times. For all the chelating agents tested, the amount of radium leached proved to be strongly dependent on the pH of the substrate: only for acidic conditions did the amount of radium released increase significantly relative to the controls. Under the best conditions, the radium released from the amended soil was greater by factors of 20 in the case of citrate, 18 for EDTA, and 14 for EDDS. The greatest improvement in the release of radium was obtained for the citrate amendment at the highest concentration tested (50mmolkg−1). A slightly lower amount of radium was leached with EDTA at 5mmolkg−1 soil, but the solubilization over time was very different from that observed with citrate or EDDS. With EDTA, a maximum in radium leaching was reached on the first day after amendment, while with citrate, the maximum was attained on the fourth day. With EDDS, radium leaching increased slightly but steadily with time (until the sixth day), but the net effect for the period tested was the lowest of the three reagents.