Sulfuric Acid Solution Research Articles

Development and Validation of the HPLC Method for Simultaneous Quantification of Glucose and Xylose in Sugar Cane Bagasse Extract.

A validated rapid high-performance liquid chromatography (HPLC)-refractive index (RI) method was developed for the identification and quantification of glucose and xylose in hydrolyzed bagasse extract. The separation of compounds was achieved on Eurokat® H column (300 × 8mm, 10μm) at 75°C, using 0.01N sulfuric acid solution as mobile phase and 0.6mL/min as flow rate. The method was validated based on accuracy, precision, linearity, robustness, uncertainty, limit of detection (LOD) and limit of quantification (LOQ). Total chromatographic analysis time per sample was ~11min. Calibration plots were linear over the concentration ranges 11-100μg/100μL for glucose and xylose. The LOD was 0.8ppm and LOQ was 2.5ppm. The high recovery and low relative standard deviation confirm the suitability of the method for determination of glucose and xylose in bagasse extract. The proposed HPLC-RI method was accurate, fast and robust and required less run time due to less analytes retention times and allowed optimal energy consumption owing to lower column oven temperature.

Maximizing the Processing of Polymetallic Concentrates via Actinide Separation and Rare Earth Retrieval

During the last decades, the growing demand for rare earth elements (REEs) has led to numerous recent studies to recover these elements from various bearing ores and wastes. Therefore, the recovery of REEs from Ras Baroud polymetallic concentrate has been investigated in the current study. Physical beneficiation for the Ras Baroud pegmatite sample was carried out, yielding a concentrate for euxenite (Y), fergusonite (Y), xenotime (Y), monazite (Ce), allanite, thorite, uranothorite, and Hf-zircon, which resulted in raising the concentrations of rare earth elements, Th, Zr, U, and Ti in the sample. Fusion digestion processes with sodium hydroxide were studied using the Conceived Predictive Diagonal (CPD) technique. The three experimental digestion groups proved the dissolution of 99.9, 95.6, 99.9, 52.5, and 0.47% for REEs, Th, U, Ti, and Zr, respectively, under fusion conditions of 723 K, 120 min, 1/1.5 ore/alkali ratio, and − 100-μm particle sizes. Fusion kinetics, isotherms, and thermodynamics were investigated using several suggested models, namely, pseudo reversible first order, uptake general model, and shrinking core model which matched well with the experimental digestion results. Selective recovery of actinide content from REE content of the digested concentrate chloride solutions was accomplished using solvent extraction with di-2-ethyl hexyl phosphoric acid. About 99.9, 99.9, and 4.2% extraction efficiencies for Th, U, and REEs were performed, respectively, using 0.3 mol/L solvent concentration in kerosene as a diluent, 1/2 organic to aqueous ratio, an aqueous pH of 0.2, and 15-min contact time. Thorium and uranium ions were stripped with sulfuric acid solution 2.5 mol/L with 94 and 98% stripping efficiency, respectively. A highly purified REE precipitate was obtained from the raffinate solutions. Zircon mineralization tailings were obtained as a by-product through the alkaline digestion process.

A novel approach for the lifetime prediction and structural health monitoring of concrete sewer systems exposed to biogenic sulphide corrosion

A novel, combined experimental-modelling approach is presented for the estimation of the corrosion depth, load bearing capacity and lifetime of unreinforced concrete sewer pipes exposed to prolonged biogenic sulphide corrosion. The biogenic sulphide corrosion process is mimicked through two types of representative chemical experiments, namely: (i) long-term experiments performed under moderately controlled pH conditions, where dry-cast concrete cube samples are exposed to monthly refreshed sulphuric acid solutions with initial pH values of 3, 2 and 1 for a period of 12 months, and (ii) short-term experiments carried out under highly controlled pH conditions, in which dry-cast concrete disk samples are subjected to sulphuric acid solutions with almost constant pH values of 2, 1 and 0.5 for a period of two months. By applying X-ray diffraction, optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy analyses, insight into the micro-scale morphology and elemental composition of the corrosion profile is obtained. In addition, the corrosion front and depth characteristics are measured by conducting phenolphthalein tests and analyses of surface colour and texture of macro-scale samples. From the experimental results, the time course of the corrosion depth is calibrated with a model for sulphate attack under a constant pH level. The model formulation is combined with detailed finite element method results from the literature to predict the long-term load bearing capacity of a concrete sewer pipe. The model is subsequently generalised for sulphate corrosion under a varying pH level. When combined with the installation of pH measuring devices on the inside of sewer pipes, the current engineering model may serve as an excellent practical tool for continuously monitoring the structural health and predicting the lifetime of in-situ sewer systems subject to sulphate attack under random acidity fluctuations.

Kinetics study on cobalt leaching from cobalt-bearing ternary sulfide in sulfuric acid solution under atmospheric pressure

The leaching of cobalt from cobalt-bearing ternary sulfide with sulfuric acid solution under atmospheric pressure was investigated. The influence of stirring speed, leaching temperature, H2SO4 concentration, and particle size on the leaching efficiency of cobalt was studied, and the kinetics analysis of cobalt leaching from the cobalt-bearing ternary sulfide was performed. The results showed that cobalt and iron were selectively leached with high efficiency (>99%) under the optimal conditions, while molybdenum and copper were enriched in residues. According to the analysis of the experimental data, the leaching of cobalt conformed to the shrinking core model with a solid product layer and was controlled by internal diffusion. The activation energy of the leaching reaction was 49.86 kJ/mol, and the reaction orders of H2SO4 concentration and particle size were 0.57 and –1.4, respectively.

Study on the evolution patterns of concrete lining’s physical and mechanical properties under sulfuric acid corrosion conditions

During operation, deep water storage and drainage tunnels may face sulfuric acid corrosion resulting from microbiologically induced chemical reactions. In this study, sulfuric acid corrosion experiments were performed on C60 concrete specimens with steel fiber volume ratios of 0% (plain) and 1% using a sulfuric acid solution with an initial pH of 1. For one-face corrosion, five faces of cubic concrete samples were coated with exposed resin, leaving only one face exposed to sulfuric acid. For all-face corrosion, all faces were exposed to sulfuric acid. Concrete corrosion under different loading conditions was compared by adding weights on top of the concrete. Rate of mass change variations and uniaxial compressive strength at various corrosion time points were monitored. The results indicated that after sulfuric acid corrosion, there was an increase in the mass but an overall decrease in the strength of the specimens. Compared with all-face corrosion, one-face corrosion led to a smaller increase in the mass of the concrete specimens and a more substantial decrease in strength, primarily because of the slower corrosion rate and reduced gypsum formation. Compared to plain concrete, steel fiber-reinforced concrete experienced a lower increase in the mass of the concrete specimens because the steel fibers obstructed sulfuric acid infiltration. However, there was significant corrosion of the steel fibers and surrounding concrete owing to accumulation of sulfuric acid around the former, resulting in a more substantial decrease in the uniaxial compressive strength of the steel fiber-reinforced concrete. With increasing load, the rate of change in the concrete mass initially decreased and then increased; this could be because increased loads densify the concrete, hindering sulfuric acid infiltration and promoting the development of microcracks within the concrete, thereby enhancing the effects of sulfuric acid corrosion.

Probabilistic models applied to concrete corrosion depth prediction under sulfuric acid environment

Accurate prediction of corrosion depth degradation law can provide a basis for the determination of the sacrificial layer thickness and the cover thickness of the concrete structural members in a corrosive environment. This study aims to explore a more accurate and safe method to predict corrosion depth. Six sets of concrete cylinder concrete specimens were adopted to perform an accelerated corrosion test in sulfuric acid solution with pH ≈ 0.95 for six different scheduled durations. 3D coordinates of a large number of points on the corroded cylindrical surface were obtained with the help of the 3D laser scanning technology. Then, a comparative study was carried out for the corrosion depth measured with the laser scanning method and vernier caliper method. The results prove that concrete corrosion depth predicted by the Gaussian random process model established by the laser scanning method was considered to possess higher credibility and better security.

Influence of clay minerals on pH and major cation concentrations in acid-leached sands: Column experiments and reactive-transport modeling

A series of laboratory experiments are conducted to simulate the acidification and subsequent recovery of a sand aquifer exploited by in situ recovery (ISR) mining. A sulfuric acid solution (pH 2) is first injected into a column packed with sand from the Zoovch Ovoo uranium roll front deposit (Mongolia). Solutions representative of local groundwater or enriched in cations (Na+, Mg2+) are then circulated through the column to simulate the inflow of aquifer water. pH and major ion concentrations (Na+, Cl−, SO42−, Ca2+, Mg2+, K+) measured at the column outlet reproduce the overall evolution of porewater chemistry observed in the field. The presence of minor quantities of swelling clay minerals (≈6 wt% smectite) is shown to exert an important influence on the behavior of inorganic cations, particularly H+, via ion-exchange reactions. Numerical models that consider ion-exchange on smectite as the sole solid-solution interaction are able to reproduce variations in pH and cation concentrations in the column experiments. This highlights the importance of clay minerals in controlling H+ mobility and demonstrates that sand from the studied aquifer can be described to a first order as an ion-exchanger. The present study confirms the key role of clay minerals in controlling water chemistry in acidic environments through ion-exchange processes. In a context of managing the long-term environmental footprint of industrial and mining activities (ISR, acid mine drainage…), this work will bring insights for modeling choices and identification of key parameters to help operators to define their production and/or remediation strategies.

Acid leaching technology for post-consumer gypsum purification

Background Contaminants and water-soluble salts present in mechanically recycled gypsum from refurbishment and demolition (post-consumer) plasterboard waste limit its use as a secondary raw material in plasterboard manufacturing. This research addresses this limitation, developing a novel acid leaching purification technology combined with an improved mechanical pre-treatment for post-consumer gypsum valorization. Methods Laboratory-scale acid leaching purification was performed with a borosilicate beaker, hot plate, and overhead stirrer. Stuccos were produced after calcination of gypsum at 150 °C for 3 hours. Samples were characterized through X-ray fluorescence, X-ray diffraction, thermal gravimetric analysis, scanning electron microscopy and particle size analysis. Results Acid leaching at 90 °C for 1 h using a 5 wt% sulfuric acid solution was revealed to be the optimum purification conditions. Stuccos produced from purified gypsum under optimum conditions had similar initial setting times to that of a commercial stucco but with higher water demand, which could be reduced by optimizing the calcination conditions. A magnesium-rich gypsum was precipitated from the wastewater. Conclusions Purified post-consumer gypsum with > 96 wt% chemical purity and calcium sulfate dihydrate content was produced. The research recommends acid neutralization prior filtration, use of gypsum particles < 2 mm in size, and stirring speed of 50 rpm to reduce the economic and environmental impacts of the acid leaching purification process at industrial scale. The magnesium-rich gypsum could potentially be marketed as soil fertilizer.

Design and Implementation of PID Controller for the Cooling Tower's pH Regulation Based on Particle Swarm Optimization PSO Algorithm

The PH regulation of cooling tower plant in southern fertilizers company (SCF) in Iraq is important for industry pipes protection and process continuity. According to the Mitsubishi standard, the PH of cooling water must be around (7.1 to 7.8). The deviation in PH parameter affects the pipes, such as corrosion and scale. Acidic water causes pipes to corrode, and alkaline water causes pipes to scale. The sulfuric acid solution is used for PH neutralization. The problem is that the sulfuric acid is pumped manually in the cooling tower plant every two or three hours for PH regulation. The manual operation of the sulfuric acid pump makes deviations in the PH parameter. It is very difficult to control the PH manually. To solve this problem, a PID controller for PH regulation was used. The reason for using the PID controller is that the PH response is irregular through the neutralization process. The methodology is to calculate the transfer function of the PH loop using the system identification toolbox of MATLAB, to design and implement a PID controller, to optimize the PID controller response using particle swarm optimization PSO algorithm, and to make a comparison among several tuning methods such as Ziegler Nichols (ZN) tuning method, MATLAB tuner method, and PSO algorithm tuning method. The results showed that the PSO-based PID controller tuning gives a better overshoot, less rise time, and an endurable settling time than the other tuning methods. Hence, the PH response became according to the target range. The experimental results showed that the PH regulation improved using the PSO-based PID controller tuning.

Determining rational parameters for the treatment of concentrated wastewater from etching site by using combined systems producing sediments of predefined composition

The object of this study is model solutions, spent sulfuric acid and chloride acid etching solutions, degreasing of metal products at enterprises. The paper reports results of research on the possibility of obtaining sediments of predefined composition and reducing the consumption of chemical reagents in comparison with conventional cleaning schemes. The systematization of the elements of the technological scheme has been shown, which provides for the treatment of concentrated wastewater of the etching area in combined systems with obtaining sediments of predefined composition and is the basis for the implementation of resource-saving technology. Rational parameters were established for the state (рН=3‒4, Eh=+0.3‒+0.33 V, and rH2=16.3–19.38 V) and technological parameters (degree of iron extraction ψ=0.8, reagent consumption from the stoichiometric norm of B=0.8). Such parameters provide the proper conditions for the oxidation of organic compounds and their co-precipitation with insoluble iron hydroxy compounds (the maximum degree of extraction of organic impurities is 86 %). The formed precipitate corresponds to the FeOOH.nH2O composition, contains 2‒3 % of organic impurities, and is subject to burial. As a result of studies on the treatment of concentrated iron-containing wastewater, the obtained sediment is ready for further utilization by processing. The composition of this sediment corresponds to the natural mineral limonite FeOOH (Fe2O3.nH2O) and is formed at pH values from 3.5 to 7.5 with rH2 values from 26 V to 21 V and at technological regeneration parameters of pH=4.0–4.6; rH2 =23.34–32.25 V. As a result of research into the deep purification of wastewater using a magnetic device, a suspension of sediment of ferromagnetic impurities (hydroxo compounds of iron) is obtained, which could be the basis for extraction or production of magnetically favorable dispersed material.

Analisis Metode Anodizing Aluminium dengan Variasi Kuat Arus sebagai Material Velg Kendaraan

Aluminum Alloy 6061 is widely used in various engineering applications, including automotive vehicle wheels. The selection of aluminum alloy wheels involves aspects such as corrosion resistance. To enhance corrosion resistance, there are several methods, one of which is anodizing. Anodizing is a process that involves an electrolytic coating process that transforms the surface of aluminum into aluminum oxide (Al2O3), which the main process of aluminum anodizing requires a solution of sulfuric acid, chromic acid, or a mixture of sulfuric acid and oxalic acid. The sulfuric acid used must be concentrated acid, and acid is an oxidizing substance. The thickness of the oxide is approximately twice the thickness of the lost aluminum. The purpose of this research is to determine the characteristic such as surface roughness values, corrosion rates, and changes in morphology in Aluminum 6061 after undergoing anodizing. In this study, various current strengths were used, namely 0.75 Amperes, 1.5 Amperes, 2.25 Amperes, and 3 Amperes. The highest surface roughness value was obtained at 0.447 μm in the third specimen of the 0.75 Ampere variation, while the lowest was 0.075 μm in the first specimen of the 3 Ampere variation. The highest corrosion rate was observed in the 0.75 Ampere variation, with a rate of 17.724004 mpy, and the lowest was 0.0731653 mpy in the 3 Ampere variation. SEM results show that, in general, Aluminum 6061 tends to have a bright gray color, which is a surface that has been coated by cathode.

Numerical Simulation Study of Gas-Liquid Two-Phase Flow in a Pressurized Leaching Stirred Tank

The gas-liquid flow and oxygen content in a pressurized leaching stirred tank significantly influence the chemical reaction rates, while the specific dynamics of gas-liquid flow in the sulfuric acid system remain largely unexplored. In this study, a mathematical model of gas-liquid flow within a stirred tank is developed using the Euler-Euler approach, with the turbulence and drag force models being validated against experimental data. Utilizing this validated and reliable model, this study investigates the impacts of the sulfuric acid concentration, baffles, air inlet velocity, and bubble diameter on the flow field and gas holdup in a two-phase system consisting of a sulfuric acid solution and oxygen. The findings indicate that introducing a specific concentration of sulfuric acid decreases the solution velocity and increases the gas holdup within the tank. However, once the sulfuric acid concentration reaches a certain threshold, further increases have a diminished effect on the gas-liquid phases. The installation of baffles enhances the turbulent kinetic energy and increases the gas holdup while only resulting in a minimal 1.2% increase in power consumption. Additionally, the inlet velocity and bubble diameter have a relatively minor impact on the tank’s flow field. However, increasing the inlet velocity significantly boosts the gas holdup, whereas an increase in the bubble diameter marginally reduces it. Furthermore, introducing a sulfuric acid solution into the tank can enhance the gas holdup when the gas inlet velocity is low. Conversely, when the gas inlet velocity is high, the addition of sulfuric acid results in a decrease in the gas holdup. The conclusions from this study contribute to enhancing the mixing effectiveness and oxygen content within the tank, providing a substantial theoretical basis for optimizing the design and operating conditions of pressurized leaching stirred tanks.

Protein-derived carbon dots as green corrosion inhibitors for carbon steel in sulfuric acid solution

At present, the development of eco-friendly corrosion inhibitors (CIs) is considered an important and attractive method for controlling the corrosion of metals in acidic media. In this study, protein-derived carbon dots (P-CDs) were prepared via hydrothermal reaction using protein as the raw material, and the corrosion inhibition performances of P-CDs for carbon steel (CS) were investigated systematically. The electrochemical test results showed that the corrosion inhibition efficiency of 500 mg/L P-CDs on CS reached 95.1 % in 0.5 M H2SO4, and the corrosion inhibition efficiency was enhanced to 98.1 % after 8 h of immersion time. The composition and characterization of P-CDs was analysed using Fourier Transform Infrared Spectroscopy (FTIR), Ultraviolet Spectroscopy (UV), X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). Atomic force microscopy (AFM) and scanning electron microscopy (SEM) characterization showed that the surface of CS with P-CDs was smoother than that without P-CDs, and that P-CDs was able to adsorb on the surface of CS to form a protective layer, thereby inhibiting corrosion. Adsorption studies indicate that P-CDs form a protective layer on the surface of CS through both physisorption and chemisorption. Overall, these findings demonstrate that P-CDs exhibit superior protective effects against the corrosion of CS in 0.5 M H2SO4.

Moisture Sorption Studies using the GAB Model of a Beef Based Dambun Nama (A Ground Meat Product) Stored over a Period of Six Months

Water adsorption isotherms of Dambun Nama, a ground beef product, were determined over a storage period of six months, at an average ambient temperature of 33.8oC and an accelerated temperature of 50oC, using the static gravimetric method. The study was aimed at establishing the moisture sorption profile of a traditional meat product Dambun Nama common in Northern Nigeria, produced from beef and stored over a period of six months. The sample was produced using a standardized method; it was sterilized, packaged in six airtight glass containers and stored at ambient temperature as the sample stock for the analyses over a period of six months. Data was generated from the sorption studies based on the isopiestic transfer method using concentrated sulphuric acid solutions. The isotherms are generally shaped like the type 4 isotherms for food products. Between 33.8oC and 50oC adsorption, the monolayer moisture content ranged from 0.036 to 0.048 gH2O/g solids, and between 0.037 to 0.049 gH2O/g solids for desorption. There was a general increase in the GAB constants K and C. The correlation coefficient (R) values obtained for adsorption ranged from 0.941 to 0.959, and for desorption, the values ranged from 0.940 to 0.957, indicating that the GAB model was suitable in describing the moisture sorption profile of Dambun Nama within the prescribed water activity ranges and storage period.

Processing-structure-microscale properties of silicon nitride

This paper presents an overview of recent works on microscale mechanical and other properties of silicon nitride (Si3N4) determined by microcantilever bending tests and their relationships with the processing and microstructures. We first focus on deformation behaviors and fracture strength of Si3N4 single crystals. β-Si3N4 single crystals are plastically deformed at room temperature under high bending stress, and the yield stress depends on the crystal orientation. The critical resolved share stress of the primary slip system is determined to be below 1.5 GPa from the yield stress. Next, we address microscale mechanical properties of Si3N4 polycrystalline ceramics. Emphasis is placed on their grain-boundary strength or toughness in conjunction with intergranular glassy film (IGF) which is determined by processing parameters such as sintering additives. Assessment is made on two cases of fractures at the IGF-grain interface and that within the IGF, and in each of the cases, effects of rare earth oxide additives are discussed. In Si3N4 ceramics doped with Al2O3, β-SiAlON layer forming on β-Si3N4 grains enhances the microscale grain-boundary strength. Finally, we shed light on microscale property-degradation behaviors of Si3N4 ceramics, including the deterioration due to the contact with molten Al and the corrosion in sulfuric acid solution. The variation of the microscale properties appears in very short periods compared to the macroscale approaches, demonstrating the advantage in terms of rapid assessment of time-dependent degradation behaviors.

STUDY ON THE PERFORMANCE OF ANODIZED COATING PREPARED ON 2024 ALUMINUM ALLOY VIA PULSE ANODIZING

Different anodized coatings are prepared on the surface of 2024 aluminum alloy from different solutions by pulse anodizing to improve corrosion resistance and hardness. The thickness, roughness, structure, hardness, surface morphology, and corrosion resistance of different anodized coatings are studied. It is found that the anodized coating is composed of a porous layer on the surface and a nonporous barrier layer inside, showing the structure of [Formula: see text]-Al2O3 and [Formula: see text]-Al2O3. The anodized coating prepared from sulfuric acid solution mixed with oxalic acid and glycerol has a larger thickness and higher hardness. The surface morphology of the anodized coatings is porous. The thickness of the anodized coating prepared from oxalic acid solution is small and the pore distribution is not uniform. However, the anodized coating obtained from sulfuric acid solution mixed with oxalic acid and glycerol has the smallest average pore size of 6.38[Formula: see text]nm and ordered pore distribution, resulting in the best corrosion resistance.

Recovery of high-grade cobalt oxide from zinc plant residue (ZPR) generated at zinc processing plants

In the present study, a method for cobalt recovery from Zinc Plant Residue (ZPR) has been developed. First, the residue was leached in a dilute sulfuric acid solution. >90% cobalt and 95% zinc were leached in two hours at room temperature. Then, leach liquor was purified before cobalt precipitation. First, copper and cadmium were removed using zinc dust. >99% copper and 80% cadmium were removed in 30 min at room temperature with slow agitation. Then, dissolved iron was removed using sodium persulfate as an oxidizing agent, and lime was used to maintain pH. Iron was precipitated (∼99%) in 1 h at 60 °C temperature by maintaining pH at 3.5 and Eh at 700 mV. After iron removal, cobalt was precipitated by using sodium persulfate as an oxidizing agent, and sodium hydroxide was used to maintain pH. The cobalt precipitate was calcined and then the final product was obtained with 58% Co. The filtrate, obtained after cobalt precipitation, had a zinc concentration of approximately 69 g/L. About 82% cobalt and 90% zinc were recovered in the entire process.

Life cycle assessment of bioproducts from bamboo residues with biphasic phenoxyethanol-acid based biorefinery technology

Utilizing bamboo residues to produce decarbonization energy products or materials diverts wastes from low-value treatment and supports the circular bioeconomy at the same time. This study develops a cradle-to-grave life-cycle assessment (LCA) for a biorefinery converting bamboo residues into bioproducts (ethanol, polylactic acid (PLA), and bio-based wood adhesive) in China. To combat the low enzymatic hydrolysis performance of bamboo residues and valorize the lignin, this study adopts a biphasic pretreatment by coupling phenoxyethanol and sulfuric acid solution (1%) to achieve high fermentable sugar production. The LCA study is coupled with a process simulation for an industrial-scale biorefinery based on the experimental data. Our results show that the life-cycle Global Warming Potential (GWP) is 17.0–32.1 gCO2e/MJ for ethanol cases and 3.2–3.7 kgCO2e/kg for PLA cases, when biphasic pretreatment is adopted. The lower GWP values are achieved by using 1:1 phenoxyethanol: acid solution, though it has a lower product yield than 4:1 phenoxyethanol: acid solution cases. Without biphasic pretreatment, the GWP is 135.8 gCO2e/MJ ethanol and 4.4 kgCO2e/kg PLA. For the perspective of treating 1 dry t bamboo residues, with biphasic pretreatment, the GWP is −174 to −66 kgCO2e for ethanol cases and −542 to −432 kgCO2e for PLA cases. The lower GWP is also from using 1:1 phenoxyethanol: acid solution (1%). These GWP ranges are lower than conventional landfilling (2969 kgCO2e) and landfilling with landfill gas recovery (−28 kgCO2e).

Separation of Osmium and Ruthenium Metals by Selective Dissolution with Two Phase System Consisted of Sulfuric Acid, Sodium Chlorate, and Tributyl Phosphate

ABSTRACT In general, separating osmium and ruthenium metals via hydrometallurgical methods poses significant challenges. This study presents a novel approach to separate osmium from a metallic mixture with ruthenium through selective dissolution using a two phase system. The system comprises an aqueous phase containing sulfuric acid solution with sodium chlorate and an organic phase consisting of pure tributyl phosphate. Among the several variables investigated in this work, sulfuric acid concentration and stirring speed showed most significant effect on the dissolution of osmium metal. Based on the potential-pH diagram of osmium metal, an oxidation reaction of osmium metal by the sulfuric acid and sodium chlorate mixture was proposed. The role of tributyl phosphate was to prevent the evaporation of the dissolved osmium tetroxide species by extracting into organic phase. The separation of the two metals was accomplished by selective dissolution of osmium at the following conditions: 3 M sulfuric acid, 0.7 M sodium chlorate, pure tributyl phosphate, pulp density of 2 g/L, 20°C, 60 minutes and stirring speed of 200 rpm. Use of a mixture of thiourea and hydrochloric acid solution containing ascorbic acid completely stripped the osmium from the loaded tributyl phosphate. Comparison of dissolution efficiency of osmium metal between two phase system and one phase system of sulfuric acid-sodium chlorate-water indicated that the employment of tributyl phosphate in two phase system was of importance in the recovery of the dissolved osmium species. Our results demonstrated that osmium can be separated from ruthenium by selective dissolution with the two phase system.

The metal anti-corrosion performance of light cured epoxy resin modified by zeolitic imidazolate frameworks (ZIF-8) with a core of polyaniline

In this paper, polyaniline (PANI) material was prepared by in-situ polymerization and mixed with zeolitic imidazolate frameworks (ZIF-8) to prepare PANI/ZIF-8 by surface modification. The light cured epoxy resin (RJ313) was modified by PANI/ZIF-8, and the PANI/ZIF-8/RJ313 anticorrosive coating was prepared. The chemical cross-linking of ZIF-8 with the epoxy resin can improve the cross-linking density and barrier property of the epoxy coating, thus improving the corrosion resistance of the coating. The encapsulation of PANI in ZIF-8 not only maintains the corrosion resistance of PANI, but also strengthens the dispersion of PANI under the action of ZIF-8 and improves the mechanical strength of the coating. A series of tests, such as the polarization test and electrochemical impedance test, proved that PANI/ZIF-8/RJ313 coating strongly affects 304SS acid corrosion resistance compared with RJ313, ZIF-8/RJ313 and PANI/RJ313. In 0.5 mol L−1 sulfuric acid solution, the corrosion current Icorr of this coating attached to 304SS was as low as 0.0308 μA·cm−2, and the impedance value can reach 37971.00 Ω·cm2. This provides a new idea for improving the dispersibility and corrosion resistance of other anti-corrosion materials.