Hot Acid Solution Research Articles

DEVELOPMENT OF CONSTRUCTIVE DESIGN OF PICKLING UNITS FOR OPERATION IN HIGHLY AGGRESSIVE HOT SULPHURIC ACID SOLUTIONS

Problem statement. Technological process of metallurgical, pipe-rolling, chemical and other enterprises includes chemical treatment of metal products by pickling in hot (60–80 °C) sulphuric acid solutions with a concentration of 20–22 %. This treatment method is conducted in the pickling departments of enterprises in special containers (pickling units). Pickling solution of the specified concentration and temperature is a highly aggressive environment for all building structures made of traditional materials. Existing pickling units for chemical treatment of metal products do not ensure reliability and durability and are destroyed after 1-2 years of operation. Therefore, ferrous metallurgy enterprises that have pickling departments for chemical treatment of metal structures are classified as enterprises with a highly aggressive environment and their design should be developed with these conditions under consideration. The purpose of the work: Searching for and implementing mechanisms to improve the resistance of polymer concrete in aggressive environments in production. The object of research – is furan resins modified polymer concrete. The subject of the research – investigation of the particularities and improvement of constructive design for pickling baths made of materials based on polymer concrete in an aggressive environment and its implementation in production. Main part. Development of constructive design for technological pickling units made of structural corrosion-resistant material (furan resins modified polymer concrete). Conclusions. Pickling of metal products at ferrous metallurgy enterprises is conducted in highly aggressive hot sulphuric acid solutions of 20–25 % concentration at a temperature of 60–80 °C. Under the conditions of constant exposure to highly aggressive hot sulphuric acid solutions, even protection with chemically resistant materials does not ensure the required reliability and durability. To manufacture such structures, a new structural material is needed that combines chemical resistance with strength and durability. This material is a structurally chemical-resistant polymer concrete based on thermoset furan resins, which have high strength and universal chemical resistance, allowing us to solve the problem of reliability and durability of technological units for chemical treatment of metal structures at ferrous and non-ferrous metallurgy enterprises in a fundamentally new way. New constructive design for pickling units made of reinforced polymer concrete was developed in conjunction with shock-absorbing bars and an improved ventilation system, consisting of individual elements of full factory readiness weighing no more than 5 tonnes, which allows them to be transported and installed in operating pickling workshops using existing mechanisms.

Adhesive bond strength of monolithic zirconia ceramic finished with various surface treatments.

This study aimed to investigate different surface treatments thought to increase the bond strength between zirconia ceramic and adhesive resin cement. The samples were prepared in 15 × 10 × 2mm dimensions by cutting off monolithic zirconia ceramic blocks (Incoris TZI; Sirona, Germany). Surface roughness measurements were made with a profilometer, the average surface roughness (Ra1) was recorded, and five different surface treatments were applied. Group 1: Control group. No surface treatment was applied. Group 2: Sandblasted with Al2O3 under pressure of 50μm. Group 3: Sandblasted with 30μm Al2O3 - SiOx under pressure, then tribochemical silica coating, silane bonding agent, and ceramic primer were applied. Group 4: Samples were etched in a hot acid solution containing methanol, HCl, and chloride at 100°C. Group 5: Samples were coated in a solution containing Grade C Aluminum Nitrite at 75°C for 15 Sects.12,000 thermal aging was carried out to all samples. Then, samples were bonded to a composite surface (Filtek Z250) with two different types of adhesive cement (Panavia F 2.0, Rely X U200) (n = 10). A load was applied to the samples attached to the Universal Test Device for the SBS, and the SBS was recorded. The surface roughness measurements of all samples were made again, and the average surface roughness Ra2 was recorded. The data was analyzed with a two-way ANOVA test. Bonferroni correction was used for multiple comparisons of the groups. p = 0.005 was accepted as the statistically significant value. There was no statistically significant difference between the groups in the Ra1 measurements (p = 0.031). There was a statistically significant difference between the Ra2 values of Groups 4 and 5 and the Ra2 values of Groups 1,2 and 3 in the Ra2 measurements (p < 0.001). There was no statistically significant difference between the SBS values of the groups (p > 0.005). Also, there was no statistically significant difference in the SBS values of all groups for the two different cements tested (p > 0.005). None of the surface treatments applied to monolithic zirconia ceramic samples increased the SBS between ceramic and adhesive resin cement.

STUDY ON POLYMER CONCRETE DEFORMATIONS IN DIFFERENT ENVIRONMENTS AT HIGH TEMPERATURE

Problem statement. High stability composite materials, such as polymer concrete, play a significant role in modern practice. Due to a continuing demand for the use of building materials resistant to aggressive environments both in Ukraine and globally, as well as their prospective use in construction, metallurgy, and chemical industry, the investigation deals with deformations of polymer concrete in various types of environment at high temperature. The purpose of the research is to find mechanisms to increase the stability of polymer concrete in aggressive environment. The object of the study is polymer concrete based on modified furan resins. The subject of the study is deformation characteristics (namely creep) of polymer concrete in different environments (water, sulfuric acid) at different temperatures. Results. In the course of research of the deformation parameters of polymer concrete in various environments were identified. Conclusions. The deformation parameters of polymer concrete on modified furan resins in hot sulfuric acid solutions were determined. It has been proved that the decrease in strength and deformation properties also depends on the hygroscopicity of benzosulfonic acid. It is shown that under simultaneous influence of aggressive environment and temperature in a stressed state the phenomenon of creep is more intensive and the polymer concrete is destroyed in a short time.

Degradation behavior of multilayer packaging films in the presence of a highly acidic sauce

Highly acidic condiments such as hot sauce can deteriorate multilayer packaging films. To date, only a multilayer polymeric film (polyethylene terephthalate/ink/polyethylene/foil/polyethylene/SiO x coated polyethylene terephthalate/adhesives/Barex®) utilizing a proprietary resin, Barex® as one of its polymeric layers can preserve hot sauce for military rations. However, the production of Barex® stopped in 2016. To identify substitutes for Barex®, an immersion study of films in hot sauce was conducted with several commercially available multilayer films (Polyethylene terephthalate/ink/adhesive/polyamide/adhesive/polypropylene and polyethylene terephthalate/waste low-density polyethylene/aluminum foil/adhesive/polyester/low-density polyethylene) and a monolayer Barex® (acrylonitrile methyl acrylate copolymer) film. All films were immersed in hot sauce, acetic acid, and sodium chloride solutions at 50 °C for 12 weeks. The mass, thickness, morphology, and chemical compositions of each film were analyzed every three weeks. Hot sauce and acetic acid solution similarly deteriorated multilayer films, causing delamination and oxidative degradation, but not sodium chloride solutions. This indicates that the failure of the multilayer packaging of hot sauce was likely caused by the low pH environment, not heat or salt ions. The two primary innovations in this study are: 1) the finding that acidic components in hot sauce deteriorate multilayer packaging by transforming aluminum foil into a soluble salt and by oxidizing polyethylene, and 2) surface erosion plays a significant role in inducing polyethylene oxidation. This is the first study to describe how a highly acidic food deteriorates multilayer packaging used for military rations. Possible deterioration mechanism of the multilayered structure (Film 2) in presence of a highly acidic hot sauce. • Acetic acid in hot sauce reacts with aluminum foil used in multilayer films. • Acids in hot sauce oxidatively degrade polyethylene (PE) layers in multilayer films. • PE in multilayer films oxidizes more in hot sauce than in acetic acid solutions. • PE in multilayer films surface erodes when immersed in hot sauce and acetic acid. • Potential multilayer film is identified for replacing Barex® for military rations.

Effect of oxidizing ions on the corrosion behavior of SiN stainless steel in high-temperature nitric acid solution

The oxidizing ions, abundantly existing in spent fuel reprocessing process, play a vital role in the corrosion behavior of stainless steels due to the inherently high electrode potential. However, the systematic research on the effect of these ions on the corrosion mechanism of stainless steels in high-temperature nitric acid media is rarely reported. Herein, the electrochemical behavior and the passive film characteristics of SiN stainless steel in hot nitric acid solution containing different ions with various concentrations were investigated. The oxidizing Cr6+, V5+ and Ce4+ affected both the anodic and the cathodic reactions, while the non-oxidizing Fe3+ only changed the cathodic reactions. Meanwhile, the passive film characteristics of SiN stainless steel are partly altered with the change in ion concentration, and the passive film primarily consisted of Fe2O3, Cr2O3, Cr(OH)3 and silicate. The existence of silicate with high chemical stability improved the protection of passive film, displaying a high resistance to intergranular corrosion in the transpassive domain. In addition, a critical concentration phenomenon was observed in nitric acid with oxidizing ions, and the deposition theory was proposed to reveal the mechanism of critical concentration phenomenon.

Segregation of Lead on High Purity Aluminum Foil for Electrolytic Capacitors

The capacitance of aluminum foil used in electrolytic capacitors is determined by their surface area after etching. Many studies have assessed pit growth using high-purity aluminum foil during DC etching in hot hydrochloric acid solutions with respect to impurity effects. High-purity aluminum foil used for electrolytic capacitors containing small amounts of lead is known to exhibit severe rolling line effects after electrochemical etching. Apparently, the lead atoms distributed on the aluminum foil surface after annealing provide nucleation sites of pitting attacks during DC etching. For this study, lead segregation on aluminum foil surfaces containing 0.6 ppm, 5 ppm and 8.2 ppm Pb annealed at 813 K for 5 h was investigated using ultra-high resolution field emission scanning electron microscopy（FE-SEM）with selective detection of high-angle backscattered electrons （BSE） and transmission electron microscopy （TEM）. High-angle BSE images revealed the presence of Pb as brighter nanoparticles with size on the order of 10 nm at the surface oxidation layer along the rolling lines caused by pick up inclusion during hot rolling. The approximately 0.5-μm-thick surface oxidation layer microstructure resembled that of grain refined surface layer （GRSL） of alloy 8006 characterized by ultra-fine grains of nano-level size. Pitting attacks first occur at the oxidation layer because of the less noble potential for tunnel dissolution during initial DC etching.

Zea Mays Surfactant as Corrosion Inhibition of Copper and its Electrochemical Assessment in Hot Acidic Solution for Chemo-Mechanical Application

This study examines the corrosion propagation of copper at temperature of 298 K, 313 K and 323 K with the help of potentiodynamic polarization route and scanning electron microscopy analyses in 0.5 M HCl. The effect of zea mays surfactant at 0%, 5%, 10%, 15,%. 20% was considered and varied to estimate the inhibitive efficiency. From the results, increase in concentration of zea mays surfactant, practically reduce the corrosion rate and provides compact heteroatom thin film layer. Interestingly, metastable pitting evolution was absent until 313 K at 20 mL concentration, but at 323 K, passivation behavior tendency was absent and pits formation was seen. Undoubtedly, addition of surfactant up to 20mL into 50 mL 0.5M HCl acid shows a reduction in copper degradation which might have caused steel corrosion reaction to endothermic. The morphology study established that pit formation occur more at higher temperature of 323 K as against the 298 K. The inhibitor exhibited a physical type adsorption mechanism with inhibitive efficiency close to 90% at 20 mL admixed.

Cover Image

The cover image is based on the Full Paper The mechanism of sorbitol dehydration in hot acidic solutions by Tomomi Kondo, Takehiko Sasaki and Motoyuki Shiga., https://doi.org/10.1002/jcc.26710.

The mechanism of sorbitol dehydration in hot acidic solutions.

Sugar alcohol dehydration in hot water is an important reaction that allows for environmentally friendly biomass conversion without the use of organic solvents. Here, we report a free-energy analysis by metadynamics (MTD) simulations based on ab initio density functional theory and semiempirical density-functional tight-binding method to understand the mechanism of dehydration reactions of d-sorbitol (SBT) in hot acidic water. Comparing the results of ab initio and semiempirical MTD, it was found that the latter gives a reliable free energy surface of SBT dehydration reaction, although the results vary upon the inclusion of dispersion correction. It was found that the reaction proceeds consistently via an SN 2 mechanism, whereby the free energy of protonation of the hydroxyl group created as an intermediate is affected by the acidic species. This mechanism was further verified by real-time trajectories started from the transition state using ab initio molecular dynamics simulations. The free energy barriers of the reaction pathways leading to five-membered ether products are lower than those leading to six-membered ether products, in agreement with experiment. This outcome can be ascribed, in part, to our finding that the reaction barrier of the pathway is correlated to the stability of the SBT confined conformation at the initial stage of the reaction.

Influence of chemical etching on bond strength of translucent zirconia to resin cement

Purpose: To assess the effect of chemical pre-treatments (piranha, hot acid, and heteropolyacid) on the bond strength (μTBS) to zirconia. Materials and Methods: A total of 8 sintered zirconia blocks were randomly assigned into 4 groups; Group I: Air abrasion, Group II: Air abrasion and etching using piranha solution (3H2SO4: 1H2O2), Group III: Air abrasion and etching using hot acid solution (1HNO3: 1HF), and Group IV: Air abrasion and etching using heteropolyacid solution (2gm/50 mL). Zirconia blocks were bonded to their corresponding pre-constructed composite blocks using adhesive resin cement. For each group, each assembly was sectioned to obtain 20 microbars. All microbars were thermocyled (10,000), then the μTBS test was done with the aid of a Universal Testing machine. To determine the mode of failure, each specimen was examined under stereomicroscope (x40). One-way ANOVA and Post Hoc Tukey tests were used. Results: The piranha pre-treatment displayed the lowest bond strength (16.82 ±5.97 MPa), while heteropolyacid pre-treatment had higher bond strength (26.22 ±4.05 MPa). One-way ANOVA test indicated statistical significant difference between the studied groups (P<.001). No significant difference was observed between control and piranha groups, also between hot acid and heteropolyacid groups. However, there were statistical significant difference between the control and heteropolyacid groups, and between piranha and heteropolyacid groups. Conclusions: According to the current findings; The novel surface pre-treatment with heteropolyacid (2gm/50 mL) performed well to improve bonding to air-abraded zirconia-based ceramics. The hot acids etching pre-treatment enhanced the bonding to zirconia.

Investigation of deactivation effect of Au addition to Ce/TiO2 catalyst for selective catalytic reduction using real diesel engine exhaust samples at low temperature conditions

AbstractBACKGROUNDNOx emissions are very toxic and cause serious adverse environmental effects. NOx reduction technologies have been developed due to the harmful effects of NOx and increasingly stringent emission standards which apply in many countries. Selective catalytic reduction (SCR) is the most effective method of removing NOx from engine exhaust. The suitable active catalysts are important for providing higher NOx conversion efficiencies in the SCR system. Catalyst production methods affect catalytic activity due to change in elemental composition, morphology, dispersion of catalytic elements, and total surface area. In this study, de‐NOx performance of Ce/TiO2 and Au‐Ce/TiO2 catalysts were investigated with real exhaust gases. Tests were carried out within 200–300 °C temperature range to evaluate low temperature performance of the catalysts. Cordierite material was used as the support material and pre‐treated with hot acid solution to enhance surface area. Ce content of synthesized catalysts with impregnation method was adjusted as 4 wt% and Au content as 0.4, 0.8, and 1.6 wt%. The catalysts were characterized with Scanning Electron Microscope (SEM), Brunauer–Emmett–Teller (BET), X‐Ray Diffractometer (XRD), and Fourier transform infrared spectroscopy (FT‐IR) analysis.RESULTSMaximum NOx conversion ratios obtained at 300 °C with the Ce/TiO2, 0.4 Au‐Ce/TiO2, 0.8 Au‐Ce/TiO2, and 1.6 Au‐Ce/TiO2 catalysts were 95.1%, 92%, 92.6%, and 90.2%, respectively.CONCLUSIONSThe results showed that in general, de‐NOx effect of the Ce/TiO2 catalyst was greater than the Au doped Ce/TiO2 catalysts. Au addition adversely affected surface properties of the catalyst and therefore activity of the Au‐Ce/TiO2 catalysts decreased. © 2021 Society of Chemical Industry (SCI).

Refined metadynamics through canonical sampling using time-invariant bias potential: A study of polyalcohol dehydration in hot acidic solutions.

We propose a canonical sampling method to refine metadynamics simulations a posteriori, where the hills obtained from metadynamics are used as a time-invariant bias potential. In this way, the statistical error in the computed reaction barriers is reduced by an efficient sampling of the collective variable space at the free energy level of interest. This simple approach could be useful particularly when two or more free energy barriers are to be compared among chemical reactions in different or competing conditions. The method was then applied to study the acid dependence of polyalcohol dehydration reactions in high-temperature aqueous solutions. It was found that the reaction proceeds consistently via an SN 2 mechanism, whereby the free energy of protonation of the hydroxyl group created as an intermediate is affected significantly by the acidic species. Although demonstration is shown for a specific problem, the computational method suggested herein could be generally used for simulations of complex reactions in the condensed phase.

Hot Water and Sulfuric Acid Solution for Increasing The Viability and Vigor of Indigofera (Indigofera zollingeriana)

Indigofera (Indigofera zollingeriana) is a multi-benefit plant, two of them are for natural dyes and livestock feed supplement. Indigofera seeds are hard and thick-coated so that the germination percentage is low and not grow in simultaneously. This study aimed to obtain an effective and practical method of increasing seed viability and vigor was carried out from March to May 2019 at the BBTP Central Java. The research used a completely randomized design, consisted 9 treatments(control, soaked in hot water by 80 and 100°C then leave it for 24 hours, and soaked in a solution of H2SO4 95% for 10, 20, 30, 40, 50 and 60 minutes) and 4 replications. The germination method used the top of paper with filter paper media. The results showed that soaking the seeds in hot water and sulfuric acid solutions significantly increased germination, maximum growth potential, vigor index, and growth rate. Soaking seeds in a 95% H2SO4 solution for 10 minutes increased the germination of the seeds (84%), maximum growth potential (91%), vigor index (69%), and growth rate by (13.81% etmal−1). The finding concludes that the best treatment was soaking seed in H2SO4 solution for 10 minutes, and longer soaking time (> 50 minutes) will decrease all parameters.

Impact of sodium caseinate, soy lecithin and carrageenan on functionality of oil-in-water emulsions

Oil-in-water emulsions are the main component of creamers, which are used to cream cold or hot coffee. These emulsions must provide the required lightening power and remain physically stable when introduced into hot acidic coffee solutions. In this study, model oil-in-water emulsions stabilized with mixed emulsifiers of sodium caseinate (0.5%) and soy lecithin (0.5%) were fabricated and their physical properties were examined over a range of pH values (pH 3.5 to 7). These model oil-in-water emulsions had strong lightening power (L* ≈ 87) and good physical stability from pH 5.5 to 7 but were unstable to gravitational separation below pH 5 due to caseinate aggregation around its isoelectric point. Addition of λ-carrageenan (0.05 to 0.175%) to the formulations prior to homogenization effectively improved their pH stability, while addition of κ-carrageenan was ineffective. The significantly higher level of sulfated ester groups in λ-carrageenan may have created a strong electrostatic repulsion between the oil particles, inhibiting their association. Our study suggests that some of the caseinate in coffee creamers can be replaced with plant-based lecithins, but that a plant-based polysaccharide is also needed to ensure their stability when added to hot acidic coffees.

Near unity ideality factor for sidewall Schottky contacts on un-intentionally doped β-Ga2O3

We report a plasma damage removal method for β-Ga2O3 devices using hot phosphoric acid solution. Sidewall Schottky diodes were fabricated on MOCVD-grown un-intentionally doped β-Ga2O3 films grown on (010)-oriented semi-insulating substrates. Removal of the plasma damaged layers using wet etching resulted in near unity ideality factor and reduced hysteresis. The anisotropic etching behavior on the electrical characteristics of the devices was further evaluated, and the [001] direction was found to be a favorable direction for vertical device fabrications. The demonstrated damage removal method could enable a range of novel device architectures, including high power vertical diodes, vertical transistors and ultra-scaled devices.

A Metal‐Free N and P‐Codoped Carbon Nanosphere as Bifunctional Electrocatalyst for Rechargeable Zinc‐Air Batteries

AbstractDeveloping metal‐free electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are crucial for the large‐scale application of fuel cells and metal‐air batteries, which have attracted extensive attention. Herein, a facile and scalable route is developed to prepare N, P‐codoped carbon nanospheres (NPCs) with the assistance of cesium chloride (NPC‐“Cs”). After treatment with hot acid solution, no trace metals are left in the electrocatalyst, as determined by inductively coupled plasma atom emission spectrometry (ICP‐AES). The obtained metal‐free electrocatalyst exhibits outstanding bifunctional catalytic activity for ORR and OER. The half‐wave potential is 0.85 V for ORR in 0.1 M KOH, and an overpotential of 0.34 V for OER in 1 M KOH is required to reach a current density of 10 mA cm−2. Furthermore, zinc‐air primary and rechargeable batteries assembled with the metal‐free electrocatalyst show similar, or even better performance compared to precious metal‐based devices containing Pt/C or IrO2 as catalysts. A facile strategy is developed to synthesize the metal free bifunctional electrocatalyst for ORR and OER that is beneficial for the development of new‐energy technologies.

Nitrogen-doped carbon nanosheets containing Fe3C nanoparticles encapsulated in nitrogen-doped graphene shells for high-performance electromagnetic wave absorbing materials

Nitrogen-doped carbon sheets containing Fe3C nanoparticles encapsulated in nitrogen-doped graphene shells are fabricated through heating the mixture of urea and ferric acetylacetonate and the subsequent treatment in hot acid solution. The nitrogen-doped carbon sheets have a lateral length ranging from hundred nanometers to several micrometers, while the Fe3C nanoparticles encapsulated in nitrogen-doped graphene have a diameter of approximately 60 nm. The nitrogen-doped carbon sheets exhibit excellent electromagnetic wave absorption property. Typically, the optimal sample has the effective absorption bandwidth of 6.0 GHz at the absorber thicknesses of only 2.0 mm, favorably comparable to those of the magnetic absorbers reported previously. The excellent electromagnetic wave absorption property of nitrogen-doped carbon sheets containing Fe3C nanocapsules encapsulated in the nitrogen-doped graphene shells can be explained by their better impedance matching character and enhanced dielectric loss.

Separate Crystallization of Lanthanide Oxalates and Calcium Oxalates from Nitric Acid Solutions

The separation of lanthanides from calcium compounds in the form of oxalates from hot nitric acid solutions of Ln(NO3)3 and Ca(NO3)2 with the insertion of oxalic acid and a Ln2(C2O4)3 · nH2O crystal seed was studied by mass-spectrometric, atomic emission, microscopic, X-ray diffraction, and fluorescence analyses. The produced single-phase precipitate was found to contain an isomorphic impurity of La–Sm oxalates, while calcium oxalate remained in the hot nitric acid solution (95°С) saturated with oxalic acid. This facile and efficient method provides Ln2(C2O4)3 · nH2O (n = 9.5 mol) in one step in a 80.1 rel. % yield, with the major phase being at least 99.4 wt %. The unit cell parameters were determined for the crystals of the isomorphic lanthanide oxalate mixture: a = 11.243(2) A, b = 9.591(2) A, c = 10.306(2) A; α = γ = 90°, β = 114.12(1)°; Z = 2; V = 1013.7(5) A3.

Effect of Hot Calcium Chloride and Acetic Acid Solutions or Hot Water Treatments on Inhibition of Total Microbial Counts and Browning in Lettuce Stem Cut During Cold Storage

Heads of iceberg lettuce (Lactuca sativa L. cv. Iceberg) were harvested at the proper stage of maturity from Kaha Experimental Farm, Qalubia Governorate, Egypt, during two successive seasons in 2015 and 2016. Good heads were transported immediately to the laboratory of Handling of Vegetable Crops Department Horticulture Research Institute at Giza. Egypt. All leaves were removed and stems were cut by a sharp knife into round slices (1 cm thickness × 2.5 diameter) then dipped for 1 min in the following solutions, hot CaCl23% or 5% at 50oC, hot acetic acid 1% or 3% at 50oC, CaCl23% or 5% at 20oC, acetic acid 1% or 3% at 20oC, hot water at 50oC and distilled water (control) to study the effect of these treatments on inhibition butt discoloration and microbial count of the stem cut lettuce during storage at 2±1 °C and 95 % relative humidity (RH) for 10 days. Results indicated that all studied treatments reduced browning index, Polyphenol oxidase (PPO) activity, Phenylalanine ammonia-lyase (PAL) activity, had lower level of microbial load and maintaining total phenolic contents of the stem cut lettuce during cold storage comparing with untreated control. Stem cut lettuce dipped in hot Calcium Chloride 5% solution showed a positive effect on enzymes related to color maintenance. It reduced the activity of the browning related enzymes polyphenol oxidase (PPO) and Phenylalanine ammonia-lyase (PAL), maintained of total phenolic content, had the lowest total bacterial counts and inhibited browning on the cut surface of lettuce stem during storage at 2±1 °C and 95 % relative humidity for 10 days.

Synthesis, characterization and solubility of mixed zirconium-cerium molybdate precipitates

ABSTRACT The reaction between fission products Mo(VI) and Zr(IV) in hot nitric acid solution during the spent fuel dissolution process leads to the formation of hydrated zirconium molybdate precipitate. This solid can include other metallic cations at the 4th oxidation state (+ IV) inside the crystal such as Pu(IV). Precipitations in the inactive surrogate system of mixed zirconium-cerium molybdates Mo-Zr(IV)-Ce(IV) were performed all over the cerium molar percentage scale from 0 to 100%, Ce(IV) being used as a surrogate of Pu(IV). The crystal structures were identified from powder X-ray diffraction patterns and complementary investigations by SEM and elemental analyses were carried out. The solid composition pointed out two phases that are ZrMo2O7(OH)2(H2O)2 and Ce3Mo6O24(H2O)4. Each of these compounds was proved being a solid solution within which the ZrIV and CeIV atoms can substitute each other. Moreover, the influence of the cerium molar fraction on the precipitate solubility was investigated and showed a strong evolution of solubility not only with the nature of the precipitate and the Ce content, but also with the nitric acid concentration.