Impurities In Solution Research Articles

Extraction Technology for Manganese Sulfate Solution Purification

Manganese sulfate is an important base manganese salt; nearly 80% of the world's manganese products are produced using manganese sulfate or manganese sulfate solution. Furthermore, manganese sulfate has many applications in industry and agriculture; thus, manganese sulfate solution impurity removal technology is important. This study aims to remove impurities from manganese sulfate solution-using complex low-grade manganese ore and manganese-rich fumes after pressure acid leaching to obtain a manganese sulfate solution, which is then purified through iron removal by oxidation neutralization; finally, the purified liquid is treated using extraction-back-extraction. We investigated the effects of various extraction parameters on the extraction rate of manganese, as well as the effects of various back-extraction parameters on the manganese back-extraction rate and manganese ion concentration in the back-extraction solution, and studied the extraction-back-extraction process. We found that the extraction and back-extraction rates of manganese could reach 95% and 96.9%, respectively, under optimal conditions..

Real-Time Crystal Growth Monitoring of Boric Acid from Sodium or Lithium Sulfate Containing Aqueous Solutions by Atomic Force Microscopy.

The crystal growth of boric acid from an aqueous solution in the absence and presence of sodium and lithium sulfate was studied by real-time monitoring. For this purpose, atomic force microscopy in situ has been used. The results show that the growth mechanism of boric acid from its pure and impure solutions is spiral growth driven by screw dislocation and that the velocity of advancement of steps on the crystal surface, and the relative growth rate (ratio of the growth rate in presence and absence of a salt) is reduced in the presence of salts. The reduction of the relative growth rate could be explained by the inhibition of advancement of steps of the (001) face mainly in the growth direction [100] caused by the adsorption of salts on the actives sites and the inhibition of the formation of sources of steps such as dislocations. The adsorption of the salts on the crystal surface is anisotropic and independent of the supersaturation and preferentially on the active sites of the (100) edge. Moreover, this information is of significance for the improvement of the quality of boric acid recovered from brines and minerals and the synthesis of nanostructures and microstructures of boron-based materials.

Impurity-Resistant CO2 Reduction Using Reactive Carbon Solutions

Electrolyzers that electrochemically convert aqueous (bi)carbonate solutions (solutions containing captured CO2, or “reactive carbon solutions”) into commodity chemicals couple CO2 capture with CO2 conversion. Industrial exhaust streams contain nitrogen oxides (NOx) and sulfur oxides (SOx) that form redox-active anions in reactive carbon solutions that can interfere with downstream CO2 reduction. We therefore designed experiments to test how impurities produced from the dissolution of NOx (NO2– and NO3–) and SOx (SO32– and SO42–) impact the electrochemical conversion of (bi)carbonate to CO. We found that CO production was unaffected by SOx compounds in a 3.0 M KHCO3 feedstock, but 2000 ppm of NOx impurities decreased CO selectivity from ∼60% to <5%. This decrease was caused by the preferential reduction of NO2– and NO3– over CO2. Our study establishes tolerance limits for common flue gas impurities in reactive carbon solutions and provides strategies to mitigate toxification effects.

Separation and Characterization of the Components and Impurities in Policresulen Solution using LC-Q-TOF MS

Background: As an external medicine, policresulen solution didn't get much attention throughout the world. From the paper which had been published yet, there has been no report concerning other unknown impurities in the policresulen solution. Four known components have been identified as well as quantified, however, as long as people’s concern for drug safety increases rapidly, there still remain impurities to be studied. Objective: This paper focuses on the separation and characterization of the impurities in the policresulen solution, which is critical for controlling the production of this drug. Methods: The components and impurities in the policresulen solution were separated and characterized using HPLC coupled with Q-TOF mass spectrometry. An ACE EXCEL 5 C18-PFP column (4.6 mm×250 mm, 5 μm) was used, and the mobile phases were 0.01 M ammonium acetate solution and methanol. Results: 21 previously unknown impurities were separated and characterized in a policresulen solution, and the structures were proposed based on the MS/MS fragmentation data. Conclusions: Based on the characterization of impurities, this study showed that there remain lots of oligomers in the policresulen solution, apart from four known components. This study could be used for further analytical analysis of the policresulen solution, which could improve the quality control of the policresulen solution and other preparations recommended in pharmacopoeias.

Identification of Two Novel Hydroperoxide Impurities in Fluocinolone Acetonide Topical Solution by Liquid Chromatography Mass Spectrometry.

Fluocinolone acetonide topical is used to treat skin discomforts such as swelling, itching and redness by activating the natural substances in the skin. Several process-related impurities and degradation products are identified and reported. But hydroperoxide impurities in Fluocinolone acetonide topical solution are not reported anywhere. In this study, we identify two potential genotoxic isomeric hydroperoxide impurities in Fluocinolone acetonide topical solution by Liquid Chromatography Mass Spectrometry analysis. A possible mechanism for the formation of these two novel hydroperoxide impurities is based on the neighboring group participation effect of adjacent hydroxyl group (Internal SN2) which results in the loss of fluorine atom and formation of epoxide intermediate followed by the addition of the HOOH group. Since most of the hydroperoxide impurities are genotoxic in nature, one should eliminate these impurities from Active Pharmaceutical Ingredient (API) or protect the formulation product from these oxidative impurities.

Nonclassical crystal growth and growth rate hysteresis observed during the growth of curcumin in impure solutions

Partially dissolved crystals of curcumin grow faster and exhibit an accelerated growth rate hysteresis.

CARBON NANOTUBE IRIDIUM-CUPRIC OXIDE SUPPORTED CATALYSTS FOR DECOMPOSITION OF AMMONIUM DINITRAMIDE IN THE LIQUID PHASE

Cupric oxide (CuO)/iridium (Ir) (1/5 wt&amp;#37;) catalysts deposited on carbon nanotubes (CNTs) are considered to be adequate active catalysts for ammonium dinitramide (ADN) decomposition. In this study, the decomposition of ADN ionic liquid was performed over CuO crystallites deposited on Ir CNTs, which were highly distributed due to their high surface area. The catalyst activity was evaluated by calculating the turnover frequency (TOF) of CuO crystallites with different content amounts into the catalyst surface. The highest activity for ADN decomposition was demonstrated over CuO at 1 wt&amp;#37; due to its highest calculated TOF. The TOF was influenced by the presence of ammonium nitrate as an impurity in the ADN solution.

Изучение возможности количественного определения металлсодержащего лекарственного вещества в присутствии металлических примесей на примере фармацевтической субстанции висмута субсалицилат

Introduction. The analysis of metals in pharmaceutical practice uses both for the quantification of an active ingredient and for assessment of elemental impurities. For metal-containing drugs, the analytical methods must be specific and free from the interference of elemental impurities. Aim. To study the influence of elemental impurities on the quantification of the pharmaceutical substance bismuth subsalicylate. Materials and methods. As a test sample the active pharmaceutical substance bismuth subsalicylate was used obtained by two different ways. Standard samples of elemental impurities of copper, lead and silver were prepared in concentrations with the maximum impurity content according to the European Pharmacopoeia. The analysis was carried out by stripping voltammetry. Results. The addition of solutions of elemental impurities of copper, lead and silver, either separately or as a mixture of all three solutions, does not cause the appearance of a signal on the voltammogram corresponding to the bismuth peak. When quantifying the pharmaceutical substance bismuth subsalicylate and comparing the peak height values, the ratio of the indicators turns out to be equal or close to 100%. Conclusion. The presence of elemental impurities of copper, lead and silver does not interfere with the quantification of the pharmaceutical substance bismuth subsalicylate by stripping voltammetry.

Modeling Impurity-Mediated Crystal Growth and Morphologies of Centrosymmetric Molecules

Foreign molecules in solution often disrupt crystal growth mechanisms and alter the crystal morphology. In this article, we predict crystal morphologies for molecules of interest by combining step velocity model theory, kinetic Monte Carlo simulations, and existing visualization frameworks. We first validate the methodology by comparing simulation results to verified step velocity models for crystal growth systems without impurities present. We then introduce impurities (both thermoneutral and energetically attractive/repulsive) to the system and examine the change in step behavior to inform impurity-mediated crystal growth models. We demonstrate the approach with a visualization of morphology for the centrosymmetric molecule naphthalene grown under a variety of growth conditions, including from impure solutions. We comment on the applicability of this approach for more complex structures, including noncentrosymmetric molecular growth units.

Ammoniacal leaching behavior and regularity of zinc ash

AbstractIn this work, a new hydrometallurgical process was developed to treat zinc ash produced from the hot galvanizing industry. The theoretical analysis shows the feasibility of dissolving zinc ash in the NH3–NH4Cl–H2O system, and the dissolution products are predominantly composed of Zn (NH3)42+. The impacts of different experimental conditions were examined, and the leaching ratio of zinc was as high as 96.4% under the conditions of NH3/NH4+ratio of 1:1, liquid/solid of 9:1, total ammonia concentration of 8 mol/L and the stirring speed of 250 rpm at 313 K for 120 min. The kinetics of the leaching process were investigated and the calculated apparent activation energy was approximately 4.69 kJ/mol, which indicated that the zinc ash leaching process was controlled by diffusion-controlled. As revealed by the determination of impurity ions, on one hand, there were fewer impurities in the leaching solution, and the concentrations of Fe2+and Pb2+in solution are less than 0.02 mg/L and 0.05 mg/L respectively; on the other hand, there was no need for further impurity removal in this process. The proposed process has a certain application value in treating zinc ash.

Membrane electrolysis for recovering Sb and Bi from elution solutions of ion-exchange resins used in copper electrorefining: A cyclic voltammetric study

• A membrane electrolysis system was proposed to recover Sb-Bi from HCl solution. • The effects of several parameters on the process were studied by cyclic voltammetry. • The reactions of electrodeposition of Sb-Bi are not electrochemically reversible. • The diffusion control for Bi is greater than for Sb. • The use of thiourea as a complexing agent must be avoided. Antimony (Sb) and bismuth (Bi), which have been considered critical raw materials by the European Commission, cause inconveniences to copper production when they are present as impurities in copper electrorefining solutions. Therefore, ion-exchange resins to extract Sb and Bi from copper-containing electrolytes have typically been applied; after the adsorption of the metals, the elution step is conducted with an HCl solution to desorb them. In the present study, a novel membrane electrolysis system with a cation-exchange membrane was proposed to extract Sb and Bi ions from the elution solution, and a cyclic voltammetric study was carried out to evaluate the influence of the most important operating parameters on the process performance, such as Sb, Bi and HCl concentration, dilution factor of the solution, the presence of thiourea as a complexing agent, the presence of iron as an impurity, and temperature. The obtained voltammograms indicated that the simultaneous presence of the metals in solution alters considerably their electrodeposition and oxidation pattern when compared to the solutions with pure metals. The reactions of electrodeposition of both metals are not electrochemically reversible and the diffusion control for bismuth is greater than that for antimony. The increase in the concentration of Sb affects its electrodeposition kinetically, whereas that of Bi is affected both kinetically and thermodynamically. The increase in HCl concentration disfavors the electrodeposition of both metals. Diluting the solution reduces the energy consumption and prolongs the membrane lifespan. Increasing the temperature reduces the cathodic potential to deposit the metals but favors the hydrogen evolution reaction. The presence of iron as an impurity does not affect the electrodeposition of both metals, whereas the use of thiourea as a complexing agent must be avoided because it impairs their electrodeposition.

Efficient photocatalytic degradation of ammonia nitrogen by Z-scheme NH2-MIL-101(Fe)/BiVO4 heterostructures

A promising Z-scheme NH2-MIL-101(Fe)/BiVO4 heterostructure was fabricated by in-situ growth of monoclinic BiVO4 onto the surface of NH2-MIL-101(Fe) nanoparticles and employed for ammonia nitrogen removal in water for the first time. Experiments demonstrated that NH2-MIL-101(Fe)/BiVO4 composites displayed boosted performance for ammonia nitrogen removal. And 10%-MBVO exhibited optimal removal rate of ammonia nitrogen as 95.7% and N2 selectivity as 92.3% in 90 min at pH of 9.0 with initial concentration as 30 mgN/L. Moreover, effects of initial solution pH, stirring speed and impurity ions (k+, Ca2+, SO42− and CO32−) were investigated. The end products and net contributions of stripping, adsorption, photolysis, photocatalysis in ammonia nitrogen removal were revealed. The functions of ·OH, ·O2− and h+ in photocatalytic degradation of ammonia were explored by scavenging experiments. The proposed mechanism indicated that the enhancement may be primarily owing to the improved light harvesting capacity and stronger redox ability of photogenerated carriers provided by Z-scheme heterostructures.

In-situ synthesis of ZnSe nanoparticles onto monoclinic BiVO4 for boosted photocatalytic decomposition of ammonia nitrogen in water

As excessive ammonia nitrogen in water will result in water eutrophication and damage human health ultimately, efficient approaches to eliminate ammonia nitrogen pollutants in water were in urgent need. Photocatalysis exhibited great advantages in ammonia nitrogen removal such as flexible application, small footprint and no secondary pollution. Herein, one kind of promising ZnSe/BiVO4 composite was prepared by depositing ZnSe nanoparticles onto monoclinic BiVO4 and applied in eliminating ammonia nitrogen pollutants. ZnSe/BiVO4 composites displayed boosted performance in ammonia nitrogen removal than raw BiVO4 and ZnSe due to improved light absorption capability and better charge separation ability. Optimally, 97.6 % of the initial ammonia nitrogen was removed and 95.46 % of the removed ammonia nitrogen was converted to harmless N2 at pH of 10.0 in 120 min over 40 %-ZBVO with initial ammonia nitrogen as 30 mgN/L. Moreover, effects of photocatalyst composition, initial solution pH and impurity ions were investigated. Contributions of stripping, adsorption, photolysis and photocatalysis were clarified. The transfer paths of photogenerated carriers and mechanism of ammonia nitrogen removal were proposed and validated.

Preferential extraction of rubidium from high concentration impurity solution by solvent extraction and preparation of high-purity rubidium salts

Rubidium has a wide range of application prospects in high-tech fields, which makes the extraction of rubidium resources of great significance. However, the similar properties among alkali metals render their separation from each other a considerable challenge. This study aims to recover rubidium from high concentration impurity solution via solvent extraction, and further purify and refine rubidium salt products. The organic phase consisted of the acidic extractant [4-tert-butyl-2-(α-methylbenzyl) phenol (t-BAMBP)] and xylene. The affecting parameters, such as contact time, extractant concentration, alkalinity, and phase ratio (O/A) were thoroughly investigated during the separation process. Rubidium could be completely extracted after the four-stage countercurrent extraction, accompanied by 18.84 % of K+ also entered the organic phase. Furthermore, deionized water was employed to remove impurity elements, such as contaminant potassium in the loaded organic phase. The scrubbing findings revealed that the scrubbing rate of K+ reached 99.03 % after five-stage countercurrent scrubbing at a phase ratio of 5:1. Most importantly, rubidium chloride solution was obtained after HCl stripping, which was further used to prepare high-purity rubidium chloride and rubidium carbonate products with a purity of 99.5 %. Eventually, this work provides a complete process for rubidium extraction and product preparation.

Study on the Adsorption Mechanism of Cobalt and Nickel in Manganese Sulfate by δ-MnO2.

Manganese has excellent performance in removing metal ions from aqueous solutions, but there are few studies on the adsorption and removal of heavy metal impurities in metal salt solutions. In this paper, the adsorption of cobalt and nickel ions in MnSO4 solution by δ-MnO2 prepared from two different manganese sources was studied. The optimum adsorption conditions were as follows: When the concentration of Mn2+ was 20 g/L, δ-MnO2 addition was 10 g/L, Co2+ concentration was 80 mg/L, Ni2+ concentration was 80 mg/L, reaction time was 60 min, reaction temperature was 80 °C, and pH value was 7, the adsorption rate of Co2+ and Ni2+ reached more than 80%. The manganese dioxide adsorbed by heavy metals was analyzed and detected. The results showed that MnOOH appeared in the phases of both kinds of δ-MnO2, and their morphologies were dense rod-like structures with different lengths and flake-like structures of fine particles. Co and Ni were distributed on the surface and gap of MnO2 particles, and the atomic percentage of Co was slightly higher than that of Ni. The new vibration peaks appeared near wave numbers of 2668.32, 1401.00, and 2052.19 cm–1, which were caused by the complexation of cations such as Co2 + and Ni2 + with hydroxyl groups. Some cobalt and nickel appeared on the surface of δ-MnO2, and the surface oxygen increased after adsorption. The above characterization revealed that the adsorption of cobalt and nickel in manganese sulfate by δ-MnO2 was realized by the reaction of its surface hydroxyl with metal ions (M) to form ≡SOMOH.

Phase stability and enhanced mechanical properties of ferro-titanium slag to aluminum titanate ceramics

• The addition of ferro-titanium slag improves the strength of the material. • Impurities in ferrotitanium slag form solid solution with aluminum titanate. • The formation of solid solution inhibits the decomposition of aluminum titanate. • Recycling and harmless utilization of metallurgical waste slag. Ferro-titanium slag is a waste slag from ferro-titanium alloy smelting. It has high strength and has been observed to act as a reinforcing phase in multiphase materials, of which ferro-titanium slag powders were chosen to inhibit the thermal decomposition of AT ceramic in 800–1300 °C temperature range and improve its mechanical strength. It was shown that Si 4 + , Fe 3 + and Ti 4 + ions in ferro-titanium slag can partially replace Al 3 + ion in AT to form an ATFS (the AT ceramic doped with SiO 2 and Fe 2 O 3 ) solid solution, which inhibited the decomposition of AT. In addition, the formation of CA 6 phase contained from phase reconstruction of ferro-titanium slag further reinforced the mechanical properties of the AT ceramic. When 50 wt% ferro-titanium slag was added, the CA 6 enhanced AT multiphase ceramic improved phase stability and reaches mechanical properties (≈14 MPa).

FUZZY ESTIMATION PROCEDURE OF THE CONCENTRATION OF THE COMPONENTS OF A SULFURIC ACID PICKLING SOLUTION

The article is devoted to the issue of determining the level of concentration of individual components of working solutions. The relevance of the topic lies in the fact that some impurities in solutions (for example, when pickling steel) cannot be measured automatically, which reduces the efficiency of the process and increases the load on the solution regeneration section. Also, impurities are hazardous waste for the environment and humans.&#x0D; The development of a method for the operational control of the composition of the pickling solution components in pickling baths is the main task of the work. A detailed substantiation of the choice of the mathematical apparatus of the method is given. The process of fuzzy identification of the composition of the components is carried out by the number of pixels with certain digital color RGB codes from digital images of the control doses of the solution. A set of technical means for providing the method for practical implementation in the technological process is described. A prototype of a graphical user interface (GUI) for the proposed method for identifying the composition of technological liquid solutions, developed in the Processing 3.0 integrated environment using applications from the Open Source Computer Vision Library, is presented.&#x0D; A technique for extracting experimental data for filling the base of a fuzzy classifier with model reference points is proposed. Its essence lies in simultaneous measurements of the concentration of the components of the pickling solution by classical methods of titration and dry residues and the proposed method with a step equal to the regulated accuracy. The results of approbation of the proposed method are presented.&#x0D; The presented technique for obtaining a fuzzy classifier can be used to develop IT tools for the operational control of the composition of various liquid solutions with opaque colored components and color identification of defects in various flat surfaces, provided that they are color distinguishable and determine the boundaries of RGB - intervals for assessing the color of individual component (defects).

Isolation and Characterization of An Allergic Dimer Impurity in Cefmenoxime Hydrochloride by NMR and HR-MS Method

Background: We systematically characterized an allergic dimer impurity in cefmenoxime hydrochloride raw material by UV, IR, HR-MS, 1D, and 2D NMR for the first time. Methods: The dimer stock solution of cefmenoxime hydrochloride was obtained by the degradation method. The target dimer impurity in the stock solution was separated by preparative RP-HPLC and purified by the freeze-drying method. By comparing the dimer to cefmenoxime hydrochloride, the functional groups corresponding to the characteristic peaks of UV and IR spectra were identified, and the molecular formula and mass fragmentation pattern were determined using HR-MS. Results: Then, based on the full assignment of 1H and 13C NMR signals， the dimerized position was confirmed and its absolute configuration was identified by 1D and 2D NMR. Conclusion: This study provided a structural basis for the allergic study of dimer impurities in cephalosporin drugs.

Small, smaller, smallest: Miniaturization of chromatographic process development

Biopharmaceuticals are becoming increasingly important in modern healthcare. Monoclonal antibodies (mAb) are one of the most widely used therapeutic proteins and are important for the treatment of cancer and autoimmune diseases, among others. After cell culture there are still large amounts of other impurities (e.g. host cell proteins) in solution. Chromatography is usually the first purification step, allowing to increase purity and reduce volume. This comes associated with high costs and chromatography accounts for a significant portion of total production costs for therapeutic proteins. Chromatographic process development may be time consuming and use large amounts of resins. Therefore, there is increased interest in finding cheaper techniques for chromatographic process development without compromising accuracy. This paper presents a highly sophisticated microfluidic chip approach for efficient adsorption isotherm determinations compared to current chromatographic process development. Implementation of an image analysis software ensures that chromatographic resin volume is accurately determined. The adsorption isotherm performance of microfluidics was compared to the robotic Liquid-handling Station (LHS) and labor intensive Eppendorf tubes. The microfluidic chip allows a 15-fold volume reduction and resin consumptions as low as 100/200 nl (200/100-fold reduction). The microfluidic chip performed comparably to the other miniaturized techniques, using less liquid and resin volume. For process development of expensive products (e.g. monoclonal antibodies), miniaturization (provided by the microfluidic chip) proved to be the most cost effective alternative whereas for less valuable products (e.g. lysozyme) automation (provided by the LHS) was the most cost effective alternative.

Circular indirect carbonation of coal fly ash for carbon dioxide capture and utilization

Mineral carbonation of alkaline wastes is a promising route for carbon dioxide (CO2) capture and utilization. An exploration of the carbonation potential of relatively inert alkaline wastes is important to develop mineral carbonation. Large amounts of coal fly ash are generated from coal-fired power plants and must be treated. A fundamental study of the circular indirect carbonation of coal fly ash was proposed and fly-ash leaching, calcium carbonate (CaCO3) precipitation, and solution regeneration with bipolar membrane electrodialysis (BPED) stages were investigated. In the leaching stage, the nitric acid/calcium ratio affected the solution pH and impurity concentration. The leaching behavior of impurities was related mainly to colloidal precipitation. Approximately 97.3% calcium in solution reacted to form precipitated CaCO3, and a higher-purity CaCO3 precipitate was obtained when a lower nitric acid/calcium ratio was used in the leaching stage. The CO2 conversion was 92.9% and the CO2 uptake efficiency was ~0.011 g-CO2/g-fly ash, which can be improved by optimizing the liquor purification process. Fundamental liquor purification was performed. Solution regeneration by BPED was evaluated by investigating the effect of electric potential and current density on the regeneration yield, current efficiency, and power consumption. A comprehensive assessment, including cost and CO2 balance, was conducted, and future interesting research on circular indirect carbonation was suggested.