Impurities In Solution Research Articles

The effect of impurity in vanadium-rich solution on vanadium precipitation of VO2(B) by hydrothermal method

The effect of iron, aluminum, silicon and phosphorus in the vanadium-rich solution on the vanadium precipitation of VO2(B) by hydrothermal method were studied. Through the analysis of vanadium conversation efficiency, the content of V and impurity elements in precipitates and their existing form, product crystal structure and micromorphology, it is concluded that the effect following the order of P > Fe > Si > Al. As the impurity concentration increased, V content of the precipitates decreased to varying degrees, while impurity content increased. The exist of Al, Si, Fe and P could alter the diffraction peaks intensity of some crystal faces and the micromorphology of VO2(B). The high concentrations of Fe and P transformed the VO2(B) to Fe2.5V7.1O16 and Na0.45VOPO4·1.58 H2O, respectively. V and P are easily combined by covalent bonds, affecting the precipitation of VO2(B). Silicon is adsorbed on the surface of the precipitate as silica gel, thereby reducing the purity of the precipitate. The influence of impurity elements in vanadium-rich solution on the precipitation of VO2(B) by hydrothermal method is studied, which will provide a theoretical basis for the application of the new process of vanadium precipitation by hydrothermal method.

Study of polymer component migrated in medicinal product from transportation packaging component: A systematic assessment beyond regulatory expectations

Light Density Polyethylene (LDPE) bottles with a specific resin were chosen as container closure system (CCS) to fill “Latanoprost ophthalmic solution” (a generic drug product). As an alternative packaging component, additional manufacturer of LDPE bottles with the same characteristics as the previously selected LDPE bottles was chosen. The appropriateness of both packaging components was evaluated using an extractables and leachable (E&L) study and a formal stability programme that monitored quality of latanoprost ophthalmic solution. The results of relevant quality attributes in stability samples of latanoprost ophthalmic solution packed in both LDPE bottles were compared. It noticed that an unknown impurity in latanoprost ophthalmic solution packaged in LDPE bottles manufactured by an additional manufacturer. Further study revealed that this unknown impurity is Epsilon-caprolactam, a leachable of plastic used in the transportation of LDPE bottles. The leachability was validated through an extraction analysis of a plastic bag used for transportation. Thus, in certain cases, when the source of leachable is not identifiable by an E&L examination of primary, secondary, and tertiary packaging components, the assessment could be extended to include packaging components utilized throughout the supply chain.

Effect of inorganic anions on precipitation of desilication products based on low-temperature Bayer process

The effect of inorganic anion impurities in sodium aluminate solution on the composition, structure and micro-morphology of desilication products (DSPs) based on the low-temperature Bayer process was systematically investigated via XRD, FT-IR, SEM and PSD methods. The sodalites with chloride-type, carbonate-type and nosean-type precipitate in the presence of chloride, sulfate and carbonate in solution, and the aluminate ions in DSPs are partly replaced by the incorporation of anion impurities. The binding capability of sulfate to the DSPs cage is stronger than aluminate, chloride and carbonate. The particle size, agglomeration degree and thickness of the circular lamellar structure of DSPs are increased by rising the concentration of anion impurities. The anions enhance the dissolution of the zeolite framework and the formation of tetradentate rings in sodalite, which promotes the transformation of zeolite to sodalite.

Effects of NaOH Concentration and Plate Surface Texture on the Performance of the HHO Generator

The need for clean energy as an alternative is inevitable. HHO gas has received much attention lately. In addition to electrolyte concentration, the breakthrough with a diverse electrode surface texture approach has not been extensively performed. Therefore, this study aims to determine the effects of NaOH concentration and plate surface texture on the performance of the HHO generator. In general, the increase in electrolyte concentration combined with surface texture caused an increase in output current, HHO gas production, and output temperature. As for the applied voltage variation with various surface textures, the increase in output current, HHO gas production, and output temperature also took place, similar to the case of increasing NaOH concentration. Either an increase in electrolyte concentration or an increase in applied voltage triggers faster ion movement, leading to an increase in conductivity, thus effectively assisting the electrolysis of water. Regarding the output current and HHO gas production, the textured surface had a much higher value than the plain surface in terms of increasing NaOH concentration or applied voltage variations. However, according to the R2 results, the linear surface has a stronger relationship with the output current and HHO gas production than the cross surface. In the case of the output temperature, the linear surface was slightly lower than the cross surface. It is possibly due to impurities in the electrolyte solution that contaminate the electrode surface, resulting in a lower output temperature on the linear surface.

High-efficiency recovery of valuable metals from spent lithium-ion batteries: Optimization of SO2 pressure leaching and selective extraction of trace impurities

The recovery of valuable metals from spent lithium-ion batteries (LIBs) is crucial for environmental protection and resource optimization. In the traditional recovery process of spent LIBs, the leaching of high-valence metals has the problems of high cost and limited reagent utilization, and some valuable metals are lost in the subsequent purification process of the leaching solution. To reduce the cost of reagents, this study proposes the use of low-cost SO2 as a reagent combined with pressure leaching to efficiently recover high-valence metals from delithiated materials of spent LIBs, while selective solvent extraction is used to remove trace impurities in the leaching solution to avoid the loss of valuable metals. Experimental results demonstrated that by optimizing the conditions to 0.25 MPa SO2 partial pressure and 60 min reaction time at 70 °C, the leaching efficiencies for Ni, Co, and Mn reached 99.6%, 99.3%, and 99.6%, respectively. The kinetic study indicated that the leaching process was diffusion-controlled. Furthermore, the delithiated materials were used to completely utilize the residual SO2 in the solution to obtain a high concentration Ni–Co–Mn rich solution. Subsequently, Fe and Al impurities were deeply removed through a synergistic extraction of Di-2-ethylhexyl phosphoric acid (D2EHPA) and tributyl phosphate (TBP) without loss of valuable metals, achieving a high-purity Ni–Co–Mn solution. The process developed based on this work has the characteristics of environmental friendliness, high valuable metal recovery, and high product purity, providing a reference technical method for the synergistic treatment of waste SO2 flue gas with spent LIBs and the deep purification of impurities in spent LIBs.

Rapid detection of trace refrigerant impurities in low-temperature ethanol: A “background silence” method based on near-infrared spectroscopy

Low-temperature ethanol method is the main process for the preparation of blood products. Ethanol is cooled using plate heat exchangers with refrigerant fluid, and the ethylene glycol in the refrigerant is a toxic reagent, so the problem of refrigerant fluid leakage has become a concern for blood product companies. The lack of detection methods of refrigerant impurities in ethanol at this process stage can lead to serious safety issues and losses in the event of a refrigerant leak. In this study, a pattern recognition method based on near-infrared spectroscopy (NIRS), the “background silence” method, was developed for the detection of refrigerant impurities in ethanol. The method considered normal impurity-free ethanol solution samples as the background and impurity samples as the interference, made the background “silent” through linear regression, highlighted the changes brought by the interference factor, and then established a “background silence” pattern recognition system by calculating the RSD value at the characteristic data points, which realised the detection of trace refrigerant impurities in ethanol solution. The specificity and sensitivity of the method reached 100 %, and the detection limit can reach 0.25 ‰. The NIRS “background silence” method enables the detection of trace refrigerant impurities in ethanol solutions with reduced computational complexity compared with the widely used PLS-DA discrimination method. This study provides new methodological guidance for the detection of impurities in low content components, and lays the foundation for the application of the “background silence” method in practical production.

Simultaneous extraction of metals from nickel concentrate via NH4HSO4 roasting−water leaching process and transformation of mineral phase

Low-temperature NH4HSO4 roasting−water leaching process was proposed to extract Ni, Cu and Co from Jinchuan nickel concentrate simultaneously. The effects of some factors on the metal extraction in the process of sulfation roasting and water leaching were systematically investigated. The results showed that 95.7% Ni, 98.9% Cu and 96.8% Co were extracted under optimized roasting and water leaching conditions. The transformation evolution of mineral phases was determined through the means of DTA−TG, XRD, SEM and EDS. The valuable metals were effectively extracted by being transformed to water-soluble metal−ammonium complexes under the sulfation reaction of NH4HSO4 and decomposed SO3 and NH3. Iron impurities in the leach solution can be removed by elevating leaching temperature to combine iron ions with ammonium ions to form NH4[Fe3(SO4)2(OH)6] precipitate. The volatiles collected in the roasting process were determined to be (NH4)2SO4 and (NH4)2SO3, which can be used as reagents for sulfation roasting.

Aqueous synthesis of perovskite precursors for highly efficient perovskite solar cells.

High-purity precursor materials are vital for high-efficiency perovskite solar cells (PSCs) to reduce defect density caused by impurities in perovskite. In this study, we present aqueous synthesized perovskite microcrystals as precursor materials for PSCs. Our approach enables kilogram-scale mass production and synthesizes formamidinium lead iodide (FAPbI3) microcrystals with up to 99.996% purity, with an average value of 99.994 ± 0.0015%, from inexpensive, low-purity raw materials. The reduction in calcium ions, which made up the largest impurity in the aqueous solution, led to the greatest reduction in carrier trap states, and its deliberate introduction was shown to decrease device performance. With these purified precursors, we achieved a power conversion efficiency (PCE) of 25.6% (25.3% certified) in inverted PSCs and retained 94% of the initial PCE after 1000 hours of continuous simulated solar illumination at 50°C.

Bromide Ion Impurity-Induced Reaction between Selenium(IV) and Acidic Bromate: Prototype of a Cycle with Autocatalytic Behavior.

The selenium(IV)-bromate reaction in an acidic medium using phosphoric acid/phosphate buffer was investigated by UV-vis spectroscopy monitoring the formation of bromine. In an excess of bromate, the absorbance-time curves measured at 450 nm display a characteristic sigmoidal shape having a fairly long induction period, while in the opposite case, when selenium(IV) species is used in excess, the measured data follow the rise and fall behavior. Depending on the excess of Se(IV) the final bromine-containing product is either an elementary bromine or bromide ion. Simultaneous evaluation of the measured kinetic traces clearly indicated that, surprisingly, no direct reaction takes place between the reactants. Instead of that, a trace amount of bromide ion impurity in the stock bromate solution is sufficient to drive the system via the oxidation of the bromide ion by bromate producing elementary bromine followed by the subsequent selenite-bromine reaction reestablishing the bromide ion to open a new cycle. As a result, the concentration of bromide ions increases in a sigmoidal fashion during the course of the reaction unless enough selenium(IV) species is present; hence, the overall synergetic effect observed is the autocatalytic rise of bromide ions. Therefore, the cycle mentioned above may be considered as a prototype of autocatalytic cycles. This observation prompted us to clarify the explicit difference between an autocatalytic cycle and an autocatalytic reaction.

Pseudo second order kinetic expression to predict the kinetics of the anomalous crystal growth of curcumin in impure solution

Pseudo second order kinetics can accurately predict the crystal growth kinetics.

Facile manufacture of high-purity CuSO4 from waste Cu-containing paint residue using combined processes of H2SO4 leaching and extraction stripping

Abstract Waste copper-containing paint residue (WCPR) represents a typical hazardous waste containing both toxic organic substances and toxic heavy metals, but there are few reports on the recycling of heavy metals. The recovery of Cu from WCPR by H2SO4 leaching–extraction–stripping has the advantages of eco-friendliness, simplicity of operation, and high value-added product. The results show that under the optimal conditions, the leaching rate of Cu in WCPR is 94.31% (18.02 g/L), while the extraction and stripping rates of Cu in the leaching solution are 99.46 and 95.32%, respectively. Due to the high concentration of Cu2+ with fewer impurities in the stripping solution, the stripping solution is heated, evaporated, cooled, and crystallized to successfully produce high-purity dark blue CuSO4 crystal, accomplishing the high-value recycling of Cu in WCPR. In addition, the leach residue of WCPR contains acrylic resin and SiO2, which can be used in cement kilns for incineration, thus realizing the overall recycling and utilization of WCPR.

Cross-validation of standardisation techniques at ANSTO using cobalt-60 and learnings from the presence and identification of non-gamma-ray emitting impurities

To fulfil the technical requirements for accreditation to ISO/IEC 17025, the end-to-end validation of all processes associated with standardising 60Co, including gravimetric source dispensing, primary standardisation by the 4π(LS)β-γ coincidence and live-timed anti-coincidence extrapolation techniques, and impurity determination were performed and documented. Pure-beta-emitting impurities in a 60Co stock solution were identified. The impact of such impurities on measurement by liquid scintillation counting and comparison in the ESIR are discussed. A fresh 60Co source was produced, standardised, and compared using the SIR.

Investigation of Effects of Sulfuric Acid in Single Wafer Cleaning Process Using Isopropyl Alcohol

Isopropyl alcohol (IPA) was used in the drying process to remove the contamination after the wet cleaning process. Regardless of the types of chemical solutions, the IPA is more strictly controlled because it is used. However, when the IPA was exposed to low acid concentration, the IPA polymers were generated to the di-isopropyl ether, isopropyl acetate, and di-isopropoxy methane. And the pH of IPA rapidly changed by about 1.99 in ppm level concentration. Generated IPA polymers were adsorbed on the wafer surface. These polymers can occur defects, and the probability increases as the concentration increases. Scanning mobility particle sizer (SMPS) measurement system can be measured the impurity in IPA solution. The total impurity concentration was increased by the concentration of H2SO4 with the same results in both gas chromatography mass spectrometry (GCMS) and time of flight secondary ion mass spectrometry (ToF-SIMS). SMPS results can be correlated with the concentration of impurities. In this paper, IPA polymers were defined by acid contamination, and these polymers have affected the Si wafer surface. In addition, the SMPS measurement system was introduced for the detection of impurities in IPA solutions.

MODELING OF NONLINEAR MASS FLOWS DURING WATER SOFTENING IN A MECHANICAL FILTER

A mathematical model of water softening in a mechanical filter based on the balance relations for the mass components of the thermodynamical system is constructed. The initial-boundary value problem of convective diffusion accompanied by a chemical reaction is formulated for one-dimensional case of spatial coordinates and reduced to the equivalent system of integro-differential equations. The solution of this system is constructed by the method of successive iterations by decomposing the functions of the mass concentrations of impurity in water solution and in the body skeleton into series around the solutions of the homogeneous linear initial-boundary value problem. Based on the expression for the impurity concentration in the aqueous solution the mass flows of impurity are obtained and investigated. The nonlinearity of steady-state regime, which is caused by the transfer of mass simultaneously by diffusion and convection mechanisms, is shown.

Nonaqueous Capillary Electrophoretic Separation of Analogs of (24R)-1,24-Dihydroxyvitamin D3 Derivative as Predicted by Quantum Chemical Calculations.

Nonaqueous capillary electrophoretic (NACE) separation was obtained of analogs of (24R)-1,24-dihydroxyvitamin D3 derivative (calcipotriol) as predicted by quantum chemical calculations supported by the density functional theory (DFT). Among the key electronic properties investigated, absolute values of the dipole polarizability and energy gap between HOMO and LUMO molecular orbitals of the analog molecules differ significantly for particular analogs, and there is a direct relationship with their electrophoretic migration time. These differences and relationships suggest that the structurally related analogs should be separable in the electrostatic field. Indeed, the robust, sensitive, and rapid NACE method was first developed for the identification and determination of the anticancer analog of calcipotriol (coded PRI-2205) and its process-related impurities (coded PRI-2201, PRI-2203, and PRI-2204) in organic and aqueous biological solutions. The direct relation between the calculated electronic properties of the analogs and the experimental electrophoretic migration time could be a promising prospect for theoretically predicting the electrophoretic separations.

Amorphous nickel hydroxide shell tailors local chemical environment on platinum surface for alkaline hydrogen evolution reaction.

In analogy to natural enzymes, an elaborated design of catalytic systems with a specifically tailored local chemical environment could substantially improve reaction kinetics, effectively combat catalyst poisoning effect and boost catalyst lifetime under unfavourable reaction conditions. Here we report a unique design of 'Ni(OH)2-clothed Pt-tetrapods' with an amorphous Ni(OH)2 shell as a water dissociation catalyst and a proton conductive encapsulation layer to isolate the Pt core from bulk alkaline electrolyte while ensuring efficient proton supply to the active Pt sites. This design creates a favourable local chemical environment to result in acidic-like hydrogen evolution reaction kinetics with a lowest Tafel slope of 27 mV per decade and a record-high specific activity and mass activity in alkaline electrolyte. The proton conductive Ni(OH)2 shell can also effectively reject impurity ions and retard the Oswald ripening, endowing a high tolerance to solution impurities and exceptional long-term durability that is difficult to achieve in the naked Pt catalysts. The markedly improved hydrogen evolution reaction activity and durability in an alkaline medium promise an attractive catalyst material for alkaline water electrolysers and renewable chemical fuel generation.

Study of lactose crystallization in vibrated bed using high and specific seeding

Lactose crystallization is an operation addressed in several scientific studies and used in dairy industries to obtain a final product with high purity, even from impure solutions. Vibration agitation becomes a relevant factor in promoting mass transfer solution-crystalline surface and minimizing breakages and ruptures in the latter. The crystallization step can be triggered by the seeding of particles (fines) of the same substance to be crystallized, promoting greater control and uniform particle size. The objective of this work was to study the operation of crystallization of lactose in a vibrated bed, using high seeding with controlled structure and size (specific). A central composite design with subsequent optimization was used as a statistical tool. Optimum operating levels were obtained, which returned responses of average productivity of 119.0 ± 2.1% and average diameter of 8.06 ± 0.22×10-6 m, also promoting an increase in the average size of crystallization products (growth of 43.6%), which was not observed in the previous study such as seeding with milled commercial lactose.

Recovery of bismuth and other metals from blast furnace dust by leaching with oxalic acid-based deep eutectic solvent and precipitation

Eutectic solvents, with the advantages of easy synthesis, high chloride content, non-aqueous environment, and low costs are the most promising alternatives to ionic liquids for leaching and recovery of metals from waste resources. The leaching of bismuth has been mainly conducted using chlorinated salts and strong acids in previous studies. The use of conventional ionic liquids can be costly. In addition, there has only been limited research into developing strategies for the recovery of bismuth from blast furnace (BF) dust using a deep eutectic solvent (DES) made of choline chloride and oxalic acid. In this work, an oxalic acid-based deep eutectic solvent was used for selective recovery of bismuth from blast furnace dust. A leaching efficiency of 94.9% Bi was achieved at the most suitable conditions (stirring speed: 300 rpm, liquid-solid ratio: 5 mL/g, temperature: 70°C, time: 20 h). The zinc and iron which are impurities in the leach solution were removed by hydrolysis and photoinduced reduction process, and the by-products of ZnC2O4·2H2O and FeC2O4·2H2O had purities of 86.6% and 96.8%, respectively. Another hydrolysis was employed to recover Bi(III) from the leach solution and the product of BiOCl was obtained with a total Bi recovery efficiency of 89.1%. The proposed process in this work is resource-saving and friendly to the environment.

Исследование влияния примесей различного характера на пенообразование аминовых абсорбентов установок очистки высокосернистых газов

The article focuses on studying the foaming process in the amine solutions (diethanolamine (DEA) and methyldiethanolamine (MDEA)) on an example of the model mixtures containing different organic and inorganic impurities and their combinations: oxalic acid, formic acid, corrosion inhibitor, hydrocarbons, amine decomposition products, mechanical impurities. It has been found that the greatest influence on foaming in the DEA solution is exerted by its decomposition products containing the formic acid, and at a concentration of 3% by weight the foam height increased by more than 3 times, and the foam stability - by 20 times. Oxalic acid also has a significant effect on foaming: at a concentration of 1 g/l the foam height increased by 3 times, and the foam stability - by more than 5 times. The decomposition products of DEA containing oxalic acid have a rather noticeable effect - the height and stability of the foam increased by 2.8 and 6.8 times, respectively. The foam grew least in the presence of formic acid - by 2 times, at the same time the stability was enhanced by more than 4 times. It has been stated that hydrocarbons have the greatest influence on foaming of the MDEA solution - at a concentration of 0.5% vol. the foam height increased by more than 1.7 times, and the stability of the foam - by 5 times. Similarly, the decomposition products of MDEA made a significant impact – the foam height increased by more than 1.7 times, and the foam stability - by 11 times. Mechanical impurities caused an increase in the foam height by more than 1.6 times and in stability by 1.4 times. Introducing a corrosion inhibitor foaming gave the least result - the foam height decreased by 2.8 times, and the stability increased by 2 times. There has been found the mutual influence of impurities in the MDEA solution, which could be seen in the mutual suppression of foaming in the double and triple mixtures compared with the single-component solutions.

Synergistic structure of LiFeO2 and Fe2O3 layers with electrostatic shielding effect to suppress surface lattice oxygen release of Ni-rich cathode

The Ni-rich cathodes used for lithium-ion batteries (LIBs) suffer from severe surface side reactions, slow kinetics, and microcracks during long-term cycling. To address these problems, a dual-modified protective coating consisting of LiFeO2&Fe2O3 layers (denoted as LFO) was fabricated on the surface of the cathode material LiNi0.8Co0.1Mn0.1O2 (NCM811) by capturing the lithium impurities in the electrolyte solution using an electric field. The LiFeO2 layer acts as an ionic conductor, accelerating interfacial Li+ transport, and exhibits a synergistic effect with the bulk material during the charging/discharging process. The Fe2O3 layer, which contains abundant oxygen vacancies, acts as an electrostatic shielding layer and effectively inhibits the outward migration of Oα− (α < 2), thus improving the structural stability. Hence, the interface-protected NCM@LFO3 cathode showed excellent cycling stability (capacity retention of 82.4% after 600 cycles at 1 C) and even at a high cut-off voltage of 4.5 V (capacity retention of 88.9 % after 200 cycles at 1 C).