Titration Of Sulfate Research Articles

EXPLORING CORROSION RESISTANCE AND MICROSTRUCTURE OF MANGANESE PHOSPHATE CONVERSION COATING ON 65Mn SPRING STEEL

Manganese phosphate conversion coatings were prepared on 65Mn spring steel. The surface morphologies and compositions of the coatings were examined through scanning electron microscopy (SEM) and X-ray diffraction (XRD). The corrosion resistance of the coatings was investigated using a copper sulfate titration experiment, salt spray test and electrochemical corrosion test. The results showed that a uniform and dense coating was obtained when the acid ratio was 10, the phosphating temperature was 85 °C, and the phosphating time was 5 min. There was no obvious rust on the manganese phosphate coating surface after 48 h of salt spray. Ultimately, the growth mechanism and corrosion behavior of the manganese phosphate conversion coating are explained.

Sulfate encapsulation by hydrogen bonding in organic clefts based on biphenyl-bridged oligourea ligands

Sulfate encapsulation faces great challenges due to the large hydration energy. Herein, a sulfate co-crystal [1, TBA4L(SO4)2, C104H174N16O20S2],was synthesized and characterized by 1H NMR, elemental analysis and Fourier transform infrared spectroscopy (FTIR). The X-ray single-crystal diffraction analysis showed that the sulfate anion was encapsulated by multiple hydrogen bonds in organic clefts containing biphenyl-bridged oligourea ligands. In the extended structure, a macrocycle including four ligands L and eight SO42- anions was constructed by N-H···O and C-H···O hydrogen bonds, which was further extended to two-dimensional hydrogen bonding network. DFT calculations showed that two sulfate anions were encapsulated by two clefts constructed by biphenyl bridged oligourea ligand, respectively, with the four corresponding tetrabutylammonium cations locating on both sides of the sulfate anions. This encapsulation mode is consistent with that of the crystal structure of the sulfate anion co-crystal 1. X-ray powder diffraction was used to study the phase purity of the bulk sample of co-crystal 1. In addition, the thermal stability of co-crystal 1 was explored by TG-DTG method, and the apparent activation energy Ea of co-crystal 1 was calculated during the main thermal decomposition process. Furthermore, the sulfate binding properties of L was investigated using UV/Vis spectroscopy method in CH3CN/DMSO solution. The binding ratio of ligand L to sulfate anion was derived as 1:2 by Job’s plot, with the binding constants K1 = 2.45 × 105 M−1 and K2 = 2.46 × 105 M−1, obtained by sulfate titration experiments. The study provides a new method for sulfate encapsulation and relative application.

Modified potassium titanate whiskers for preparation of enhanced corrosion-resistant phosphating conversion coatings with high NIR reflectivity on mild steel

In this paper, Potassium titanate whiskers (PTW), a kind of high NIR reflectional material, were modified with stearic acid (SA) and used as a green accelerator in phosphating bath to build super-hydrophobic phosphating conversion coatings (PCCs) with enhanced corrosion resistance and high NIR reflectivity on mild steel in one-step at low temperature. The scanning electron microscopes (SEM), water contact angle (WCA), X-ray diffraction (XRD), potentiodynamic polarization, copper sulfate titration, electrochemical impedance spectroscopy (EIS), long-term immersion test, NIR reflectivity, linear abrasion experiment as well as tape peeling experiment were investigated to explore the performance of PCCs. The PCCs with the optimal 0.8 g/L concentration of SA-PTW possesses the densest structure, the largest WCA of 153° and the highest NIR reflectivity of 48 %. The potentiodynamic polarization results show that the 0.8-SA-PTW occupies the lowest corrosion rate (7.531 ×10−4 mpy), and remains minimal (3.56 ×10−3 mpy) after soaking in 3.5 wt % NaCl solutions for 20 days, resulting in enhanced long-term corrosion protection of mild steel. These special properties of PCCs effectively prevent the invasion of corrosive medium and the heat accumulation which would have great potential applications in anti-corrosion “cool coatings” for exterior corrosion protection of body and hull.

Enalapril maleate as a green accelerator for zinc phosphating coating on low-carbon steel

In this study, enalapril maleate (EM), a green ingredient of an antihypertensive drug, was selected as an accelerator for phosphate coating promoting on low-carbon steel. The scanning electron microscope (SEM), X-ray diffraction (XRD), 3D morphologies, coating weight, coating thickness and free acidity (FA) as well as total acidity (TA) were characterized to analyze the coating performance. Copper sulfate titration, potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) were performed to evaluate corrosion resistance of phosphate coatings. The DFT computations were applied to explore the phosphating promoting mechanism. The results show that the EM optimal concentration is 1.6 g/L which lowers the operating temperature (form 80 ℃ to 40 ℃), generates the smoothest (Ra = 2.85 μm), the heaviest (28.35 g/cm2) and the thinnest (21.6 μm) coating, and reduces the corrosion rate from 1.099 mpy of blank to 0.0246 mpy. The density functional theory (DFT) results confirm that EM adsorbs on low-carbon steel by electrophilic sites (N10) as well as nucleophilic sites (C10), forms nucleated particles preferentially and accelerates the growth of crystals. Therefore, EM is a green organic compound with high phosphating promotion efficiency which has potential application prospects in industrial phosphating.

Systemical investigation on the determination of sulfate in cement-based materials based on a promoted conductometric titrator

The concentration of sulfate ion in cement-based materials is the basic data for the design and evaluation of concrete structures exposed to sulfate lakes and saline soil areas. In this study, a conductivity titrator was developed and used to test the sulfate concentration in concrete corroded by sulfate attack based on the Internet of Things. The theories of conductivity measurement and conductivity titration were described; The main hardware composition and software design of conductometric titrator were introduced; Then, the effects of temperature, concentration, hydroxyl ion and hydrogen ion on the conductivity of solution of sodium sulfate and barium chloride were explored by the titrator; The titration parameters, the influence of hydroxyl and hydrogen ion on sodium sulfate titration were determined by test of sulfate ion titrated by barium chloride with known concentration; Finally, the titrator was used to test the sulfate concentration in cement-based materials after sulfate attack. The results show that the titrator can measure the conductivity of solution with 0.4% accuracy and the concentration of sulfate ion with 0.8% accuracy; During the titration of sulfate ion, the concentration of barium chloride should be twice that of sulfate ion, the titration rate should be less than 0.828 mL/s, and the titration volume should be at least 10 mL; It is found that the influence of hydroxyl ion can be effectively eliminated by adding nitric acid or hydrochloric acid, and the influence of hydrogen ion can be effectively eliminated by adding sodium carbonate. This conductivity meter can accurately test the sulfate concentration in the concrete after corrosion.

Magnesium sulfate titration reduces maternal complications following fetoscopic closure of spina bifida.

To evaluate if magnesium sulfate (MgSO4 ) titration following fetoscopic spina bifida closure is associated with fewer maternal complications than the Management of Myelomeningocele Study (MOMS) tocolytic regimen. This prospective cohort study included 73 consecutive patients undergoing fetoscopic closure of spina bifida between 2015 and 2020. A policy of using the MgSO4 regimen per the MOMS trial was changed to a flexible one in which MgSO4 was titrated according to the frequency of the uterine contractions following surgery. The frequency of maternal pulmonary edema, low maternal oxygen saturation requiring oxygen supplementation, atelectasis, hypocalcemia, and preterm delivery was compared before and after the policy was changed. A higher proportion of women in the group that used the MOMS MgSO4 regimen had pulmonary edema compared to those in the flexible one (26.1% [6/23] vs. 6% [3/50]; p=0.024). Multivariate analysis showed that the MOMS tocolytic regimen was independently associated with a higher risk of pulmonary edema (adjusted odds ratio: 8.57; 95% confidence interval: 1.54-47.7; p=0.014) than a flexible one. There was no difference in the rate of preterm delivery. Following fetoscopic closure of spina bifida, the MOMS MgSO4 regimen is associated with an increased risk of pulmonary edema than a more flexible regimen.

Effects of perioperative magnesium sulfate with controlled hypotension on intraoperative bleeding and postoperative ecchymosis and edema in open rhinoplasty.

This randomized, double-blind study was planned to evaluate the effect of perioperative magnesium sulfate with controlled hypotension on intraoperative bleeding, postoperative ecchymosis and edema, and side-effects. Forty-nine patients undergoing open rhinoplasty were divided into two groups - magnesium sulfate and control. The magnesium sulfate group received 30-50mg·kg-1 intravenously as a bolus before induction of anesthesia, followed by 10-20mg·kg-1h-1 by continuous intravenous infusion during surgery. Anesthesia was induced with propofol 3mg·kg-1, fentanyl 15μg·kg-1 and cisatracurium 0.6mg·kg-1. Mean arterial pressure was maintained at 50 to 60mmHg under controlled hypotensive anesthesia with magnesium sulfate titration. Hemodynamic variables, operational bleeding, early postoperative side-effects and postoperative first-, third- and seventh-day ecchymosis and edema were compared between the groups. Ecchymosis and edema were evaluated using a graded scale from 0 to 4. In the magnesium sulfate group, mean arterial pressure decreased during most of the perioperative period. Intraoperative bleeding also decreased. A distinct reduction in ecchymosis and edema was observed in both the upper and lower eyelids on the first, third and seventh days. Patients in the magnesium sulfate group also had a more peaceful postoperative course with less postoperative nausea vomiting, and shivering. Magnesium sulfate with controlled hypotension can lower ecchymosis and edema of the upper and lower eyelids in rhinoplasty surgery by reducing bleeding.

Study on the relationship between crosslinking degree and properties of TPP crosslinked chitosan nanoparticles

In order to reveal the relationship between the degree of crosslinking and the properties of chitosan nanoparticles, a potassium polyvinyl sulfate (PVSK) titration method was established for the determination of free amino group in chitosan, which showed that there was a window effect in the crosslinking degree and particle size of three kinds of molecular weight chitosan cross-linked by different content of tripolyphosphate (TPP), and the nanoparticles with moderate crosslinking degree were smaller. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) showed the moderate degree of cross-linking nanoparticles had strong antibacterial properties. IR analysis showed that the interaction between chitosan nanoparticles with different crosslinking degree and TPP were different. X-ray diffraction analysis showed that the cross-linked chitosan nanoparticles were amorphous. Above all, the crosslinking degree of TPP cross-linked chitosan nanoparticles was related to the particle size and antibacterial properties.

Determination of ferromanganese and ferrosilicon by ammonium ferrous sulfate titration and ICP

ferromanganese alloy; ferrosilicon alloy; chemical analysis

(Invited) Electrochemical Measurement Approaches for Planetary Exploration

2018 marks the 10-year anniversary of the landing of the NASA Phoenix spacecraft on the ice-rich northern plains of Mars. The Phoenix Lander carried the Wet Chemistry Laboratory (WCL), a component instrument of the Microscopy, Electrochemistry, and Conductivity Analyzer (MECA) and was used to perform a comprehensive electrochemical characterization of martian soil in an aqueous solution. Designed to characterize the habitability of the martian surface, WCL contained an array of ion selective electrodes, a conductivity cell, a platinum electrode to measure redox potential, electrodes to perform perform cyclic voltammetry, chronopotentiometry and anodic stripping voltammetry, as well as a set of chemical reagents used to perform a sulfate titration and sample acidification. The measurements made with WCL resulted in a number of major discoveries, including the detection of percent levels of perchlorate on the martian surface, and represent the first, and to date, the only time electrochemical methods have been used for planetary exploration beyond Earth. NASA is now embarking on a new era of astrobiology exploration as plans are being formulated for missions to Ocean Worlds of the outer solar system, including Europa, an ice covered Jovian moon. Based on lessons learned during the development of WCL and its operation on the surface of Mars, we will discuss new design approaches and strategies that will enable the implementation of autonomous microfluidic electrochemical sensor arrays during upcoming missions to these yet to be explored solar system environments.

Preparation and Corrosion Resistance of Trivalent Chromium-Zirconium Composite Coating

Aluminum alloys are widely used in the various industries because of its superior advantages. However there will be a thin oxide layer on the surface of the pure aluminum to inhibit corrosion, when adding some other elements, the obtained aluminum alloy is easy to be corroded. Surface protection is an important means to improve the corrosion resistance of aluminum alloys. The formal research had already confirmed that the trivalent chromium conversion coating can significantly improve the corrosion resistance, and the usage of the zirconium solution can also protect the aluminum alloy from corrosion. In this study, we constructed the binary conversion coating with the Cr2(SO4)3 and the K2ZrF6. The optimum reaction conditions are as follows: 10g/L H3PO4, 2g/L K2ZrF6, 28g/L Cr2(SO4)3, pH=2.5∼3.5, temperature 40°C, and reaction time 10 min. Copper sulfate titration experiment confirmed that the corrosion resistance was significantly improved.

A titration method for determining individual oxidant concentration in the dual sodium persulfate and hydrogen peroxide oxidation system

The use of a dual oxidation system, which combines sodium persulfate (Na2S2O8, SPS) and hydrogen peroxide (H2O2, HP) is increasing as an in-situ chemical oxidation (ISCO) process for soil and groundwater remediation. An analytical method was assessed in this study for determining individual oxidant concentration in order to understand the interactions, and variations in the concentrations, of SPS and HP in aqueous systems containing both SPS and HP. The iodometric titration method was demonstrated to be capable of measuring total oxidant (SPS + HP) concentration; while the ceric sulfate titration method can be used specifically for measuring HP in the dual oxidation system without interfering with the iodometric titration. Therefore, SPS concentration can be deduced by subtraction of the HP concentration from the total oxidant concentration. Direct iodometric titration for determination of total oxidant at concentration above 20 mM exhibited <8% concentration. Based on the results of indirect determination of SPS in the dual oxidation system, an approximate 10% concentration variation was expected. This research may serve as a reference for measuring oxidant variations in this ISCO dual oxidant application.

PVC-zeolite nanoparticle-surfactant anion exchanger membrane: preparation, characterization, and its application in development of ion-selective electrode for detection of sulfate

A modified PVC electrode with tetradecyltrimethyl ammonium surfactant-clinoptilolite nanoparticles exhibited Nernstian response (29.9 ± 0.9 mV per decade) for sulfate ions in a working concentration range of 1.0 × 10− 7 − 1.0 × 10− 1 mol × L− 1 sulfate (detection limit of 7.0 × 10− 8 mol L− 1 sulfate). The sensor had a fast response time of 7–10 s and can be used for at least 8 weeks without any divergence in potential. The electrode can be used in the pH range of 4–10. The proposed electrode successfully used for determination of sulfate in zinc sulfate pharmaceutical capsule and as indicator electrode in titration of sulfate with barium chloride.

Development of a highly selective and sensitive sulfate—polymeric membrane sensor based on Nickel(II)–dioxime complex as neutral carrier

A novel sulfate–poly(vinyl chloride) (PVC) membrane based on nickel complex of 3,8-dimethyl-5,6-benzo-4,7-diazadece-3,7-diene-2,9-dione (dioxime) was prepared and used as a sensor for sulfate ions in solution. The proposed sensor revealed an excellent linear response towards SO42- ion in the concentration range of 5.0 × 10–7 to 1.0 × 10–2 M with an anionic slope of −30 ± 0.2 mV per decade. The potentiometric behavior of the sensor was independent of the pH of the solution in the range of 4.5–7.5. The fabricated sensor showed an outstanding reproducibility, fast response time, and with a low detection limit as 3 × 10–7 M. The interference of hydrophobic inorganic anions was very low in comparison with the conventional ion-exchanger-based electrodes, as shown by the selectivity coefficients determined by the separate solution method. The sensor also was used successfully as an indicator electrode in the potentiometric titration of sulfate with barium ions and in quantification and quality assessment of sulfate in some pharmaceutical formulations.

Sulfate-selective electrode based on a bis-thiourea ionophore

A new coated graphite sulfate-selective electrode based on the use of the anion receptor N-[4-[4-[(anilinocarbothioyl)amino]benzyl]phenyl]-N-phenylthiourea in poly(vinyl chloride) matrix is reported. Addition of cetyltrimethylammonium bromide and various plasticizers (2-nitrophenyl octyl ether, dibutyl phthalate, dioctyl phthalate, and chloronaphthalene) was found to substantially improve the performance of the sensor. The electrode showed a Nernstian response for SO 4 2− ions over a wide activity range (3.0 × 10−7–1.0 × 10−1 M) with a limit of detection of 1.9 × 10−7 M. The response time of the sensor was ~15 s, and the membrane could be used for more than 2 months without observing any deviation. The electrode revealed acceptable selectivity towards sulfate with respect to many common anions and also was used as an indicator electrode in potentiometric titration of sulfate and barium ions and in determination of sulfate in a pharmaceutical zinc sulfate capsule.

Assay of Abacavir Sulfate

A modified volumetric method for assay of abacavir sulfate in substance is described; this is an intermediate salt [(C14H18N6O)2 ⋅ H2SO4)] containing trace quantities of the acid salt. Methods for abacavir sulfate assay in substance using volumetric methods are known, as are HPLC assays. We present here a modified method for the alkalimetric titration of abacavir sulfate with a correction for the initial pH of the substance solution being titrated. This excludes increases in results obtained by titration due to the presence of traces of the acid sulfate of abacavir in the test substance. The proposed method is shown to have advantages over known methods, including the standard alkalimetric titration without correction for the initial pH of the titration solution. The method is rapid, gives accurate results, is highly reproducible, and does not require the use of expensive reference samples. A relative metrological comparison of HPLC and alkalimetric titration methods is presented. The metrological characteristics of the HPLC method using reference samples indicate that it is unlikely to provide results to an accuracy of ± 2% with a confidence limit of 95% for assay in substance. The realistic accuracy range for normalization in this case is ± 3%.

2-(3-Pyridyl)imidazole-4,5-dicarboxylic acid based lanthanide luminescent anion sensor

A novel terbium 2-(3-pyridyl)imidazole-4,5-dicarboxylic acid complex was incorporated into inorganic host (tetrethoxysilane, TEOS) and we developed a green luminescent hybrid material via a sol–gel reaction. The sensing abilities of this material were studied by addition of HSO 4 − , F −, Cl −, Br −, I − and CH 3COO − to aqueous suspension of the assayed bulk material. The titration of hydrogen sulfate (detection limit 10 −5 M) resulted in the reduction of the green luminescence, whereas fluoride ions (detection limit 10 −4 M) caused the luminescence changing from green to blue. We recognized that fluoride ion forms hydrogen bonding interactions with ligand. But hydrogen sulfate anion changed the green emission mainly because of its acidity.

Application of surfactant modified zeolite carbon paste electrode (SMZ-CPE) towards potentiometric determination of sulfate

A sulfate-selective electrode based on surfactant modified zeolite (SMZ) particles into carbon paste has been proposed (SMZ-CPE). The electrode was fully characterized in terms of composition, response time, ionic strength range, thermal stability and usable pH range. The electrode containing 10% of the SMZ was exhibited linear response range to sulfate species in the range of 2.0 × 10 −6–3.1 × 10 −3 M with detection limit of 2.0 × 10 −6 M and Nernstian slope of 29.8 ± 0.8 mV per decade of sulfate concentration. The electrode response remains constant in the pH range of 4–10 and in the presence of 1 × 10 −4–2 × 10 −3 M NaNO 3. The response of the electrode reaches equilibrium within several second after immersing the electrode in sulfate solution. A successful application of sulfate determination sulfate in real sample of a pharmaceutical zinc sulfate capsule, using direct potentiometry, is presented. The electrode was also used for potentiometric titration of sulfate. The validation of the obtained results in each case was proved by statistical methods.

The effect of crosslinker structure upon the rate of hydroperoxide formation in dried, crosslinked poly(vinylpyrrolidone)

AbstractThe hydroperoxide levels of two commercial types of crosslinked poly(vinylpolypyrrolidinone) (or crospovidone) disintegrants were studied as a function of time and temperature using the titanyl sulfate titration method. It was noted that the two crospovidone types exhibited significantly different rates of hydroperoxide buildup and that this difference increases with increasing temperature. While the chemical and physical structures of these commercial types are essentially the same, they are known to be different with respect to their crosslinkers which represent nominally 2% of the total mass. These crosslinkers are 3‐ethylidene‐N‐vinyl‐2‐pyrrolidinone and N,N′‐divinylimidazolidinone. While both contain lactam type rings, the latter possesses two nitrogen atoms versus one in the former. It was hypothesized that this difference in the number of heteroatoms results in a greater susceptibility to oxidative attack at carbon positions vicinal to these nitrogen atoms. To test this hypothesis, model compounds representing the two crosslinker ring structures were subjected to oxidative attack and analyzed for hydroperoxide buildup over time and at several temperatures. The results of the model compound study were consistent with the observations made for hydroperoxide buildup in the corresponding crospovidone types thereby supporting this hypothesis. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

The relative stabilities of the copper hydroxyl sulphates

AbstractThe literature contains considerable disagreements on the relative stabilities of the members of the copper hydroxyl sulphate family. Titration of copper sulphate with sodium hydroxide is claimed by some to produce only brochantite, while other reports indicate that antlerite and a dihydrate of antlerite are produced in the titration. Most stability field diagrams show that antlerite is the more stable stoichiomer at pH 4 and sulphate activity of 0.05–1. We have reexamined this stoichiometric family by titration of aqueous copper sulphate with sodiumhydroxide and sodium carbonate, reverse titration of sodiumhydroxide with copper sulphate and simultaneous addition of copper sulphate and sodium hydroxide at a variety of mole ratios, concentrations, temperatures and reaction times. We have also explored the reaction of copper hydroxide with copper sulphate and the reaction of weak bases, such as sodiumacetate, sodiumcarbonate and urea, with copper sulphate. Our work indicates that: (1) antlerite is not formed in reactions of 0.05 to 1.2 M CuSO4 with 0.05–1.0 M NaOH or Na2CO3 at room temperature; (2) antlerite is formed in the addition of small concentrations of base (≤0.01 M) to 1 M CuSO4 at 80°C, but not at roomtem perature or with 0.01 M CuSO4 at 80°C; (3) the formation of Cu5(SO4)2(OH)6·4H2O occurs at large Cu2+ to base mole ratios; (4) the compound described in the literature as antlerite dihydrate is actually Cu5(SO4)2(OH)6.4H2O; (5) at mole ratios of Cu2+ to OH– ranging from 2:1 to 1:2 the predominant product is brochantite; and (6) brochantite and Cu5(SO4)2(OH)6.4H2O are converted to antlerite in the presence of 1 M CuSO4 (the latter requires temperatures of 80°C or greater).The Ksp (ion activity product) values of antlerite and brochantite were determined to be 2.53 (0.01)⨯10−48 and 1.01 (0.01)⨯10−69, respectively, using atomic absorption spectroscopy and Visual MINTEQ after equilibration in solutions of varying ionic strength and pH for six days. These values are in good agreement with those from the literature. However, after 6 months, antlerite in contact with solution is partially converted to brochantite and hence is metastable with a relatively low conversion rate. The Ksp value for antlerite must therefore be considered approximate. The relative stabilities of the copper hydroxyl sulphates are rationalized using appropriate equations and Gibbs energy calculations. A Gibbs free energy of formation for Cu5(SO4)2(OH)6.4H2O of –3442 kJ/mol was obtained from the simple salt approximation.