The binary oxide adsorbent using Fe and Mn (Fe-Mn) has been prepared by precipitation method to enhance the removal of phosphate. Different amounts of chitosan, a natural organic polymer, were used during preparation of Fe-Mn as a stabilizer to protect an aggregation of Fe-Mn particles. The optimal amount of chitosan has been determined considering the separation of the Fe-Mn particles by gravity from solution and highest removal efficiency of phosphate (Fe-Mn10). The application of Fe-Mn10 increased removal efficiency at least 15% compared to bare Fe-Mn. According to the Langmuir isotherm model, the maximum uptake (qm) and affinity coefficient (b) were calculated to be 184 and 240 mg/g, and 4.28 and 7.30 L/mg for Fe-Mn and Fe-Mn10, respectively, indicating 30% and 70% increase. The effect of pH showed that the removal efficiency of phosphate was decrease with increase of pH regardless of type of adsorbent. The enhanced removal efficiency for Fe-Mn10 was maintained in entire range of pH. In the kinetics, both adsorbents obtained 70% removal efficiency within 5 min and 90% removal efficiency was achieved at 1 h. Pseudo second order (PSO) kinetic model showed higher correlation of determination (R2), suggesting chemisorption was the primary phosphate adsorption for both Fe-Mn and Fe-Mn10.

Bis (2-ethylhexyl)phosphoric acid (HDEHP) is a renowned extractant, favored for its affinity to selectively remove uranium via its P=O groups. We previously synthesized HDEHP-functionalized mesoporous silica microspheres for solid-phase uranium adsorption. Herein, we investigated the kinetic and isothermal behavior of uranyl ion adsorption in mesoporous silica microspheres functionalized with phosphate groups. Adsorption experiments were conducted by equilibrating 20 mg of silica samples with 50 mL of uranium solutions, with concentrations ranging from 10 to 100 mgU L−1 for isotherms and 100 mgU L−1 for kinetics. Three distinct samples were prepared with varying HDEHP to TEOS molar ratios (x = 0.16 and 0.24) and underwent hydrothermal treatment at different temperatures, resulting in distinct textural properties. Contact times spanned from 1 to 120 hours. For x = 0.16 samples, it took around 50 and 11 hours to reach equilibrium for the hydrothermally treated samples at 343 K and 373 K, respectively. Adsorbed quantities were similar (99 and 101 mg g-1, respectively), indicating consistent functional group content. This suggests that the key factor influencing uranium adsorption kinetics is pore size of the silica. The sample treated at 373 K, with a larger pore size (22.7 nm) compared to 343 K (11.5 nm), experienced less steric hindrance, allowing uranium species to diffuse more easily through the mesopores. The data confirmed the excellent fit of pseudo-second-order kinetic model (R2 > 0.999) and closely matched the experimental value, suggesting that chemisorption governs the rate-controlling step. To gain further insights into uranium adsorption behavior, we conducted an adsorption isotherm analysis at various initial concentrations under a constant pH of 4. Both the Langmuir and Freundlich isotherm models were applied, with the Langmuir model providing a superior fit. The relatively high R2 value indicated its effectiveness in describing the adsorption process, suggesting homogenous sorbate adsorption on an energetically uniform adsorbent surface via a monolayer adsorption and constant adsorption site density, without any interaction between adsorbates on adjacent sites. Remarkably, differences in surface area did not significantly impact uranium removal efficiency. This observation strongly suggests that the adsorption capacity is primarily governed by the loading amount of HDEHP and the inner-sphere complexation with the phosphoryl group (O=P). Our silica composite exhibited an impressive adsorption capacity of 133 mg g-1, surpassing the results reported in the majority of other silica literature.

In KAERI’s previous phosphate precipitation tests, the dispersed powder of lithium phosphate (Li3PO4) as a precipitation agent reacted with various metal chlorides in a simulated LiCl-KCl molten salt. The reaction of metal chlorides composed of actinides such as uranium and three rare earths (Nd, Ce and La) with lithium phosphate is a solid-liquid reaction. A phosphorylation reaction rate is very fast and the metal phosphates as a reaction product precipitated on the bottom of the molten salt crucible. One of the recovery methods of the metal phosphate precipitates is segregation the lower part (precipitates) of the salt ingot using the various cutting tools. Recently, a new phosphorylation experiment using lithium phosphate ingots carried out in order to collect the metal phosphate precipitates into a small recovering vessel, and the test result of this new method was feasible. However, the reaction rate of test using lithium phosphate ingot is extremely slower than that of test using lithium phosphate powder. In this study, the precipitation reactor design (a tapered crucible with polished inner surface) used for phosphorylation reaction showed that the salt ingot with metal phosphate precipitates could be detached from a tapered stainless steel crucible. We propose that the recovery of precipitates from a salt ingot is possible by introducing a dividing plate structure into a molten salt and by positioning it at the interface between salt and precipitated metal phosphate.

The phosphate industry is classified by IAEA as one of the Naturally Occurring Radioactive Materials (NORM) industry sectors most likely to require regulatory consideration. The production of phosphorous fertilizers constitutes the major activity in the industry, which can give rise to exposures of workers and the public through the handling and usage of phosphate rock and residues associated with processing. During the production process, when phosphate rock is digested with acid to produce phosphoric acid, some radionuclides, particularly Radium, become concentrated in residues, such as the scale that tends to form inside pipes and vessels. The registered radioactivity of phosphate rock in South Korea is less than 1.7 Bq/g for U-238, but according to the IAEA SRS No. 49, the radioactivity of phosphate scale can be up to 1,000 times higher than the raw mineral. Therefore, this study evaluated the potential for worker exposure during maintenance related to the removal of scales at a fertilizer manufacturing facility producing phosphoric acid in Korea.

In this study, we evaluated the performance of phosphate-functionalized silica in adsorbing uranium and provided insights into optimizing the initial conditions of the uranium solution (concentration and pH), which are often overlooked in uranium adsorption studies. While most studies take into account the effect of pH on both the surface charge of the adsorbents and the dissolved speciation of uranium in solution, they often overlook the formation of solid phases such as β-UO2(OH)2 (cr) and UO3· 2H2O(cr), leading to an overestimation of the adsorption capacity. To address this issue, we considered the speciation of U(VI) calculated using thermodynamic data. Our findings suggest that it is reasonable to evaluate the adsorption performance at pH 4 and concentration below 1.35 mM. The formation of β-UO2(OH)2 (cr) starts at 23 μM (pH 5) and 1 μM (pH 6) and increases sharply with increasing concentration. To avoid interference from the formation of solid phases, experiments should be conducted at lower concentrations, which in turn require very small msorbent/Vsolution ratios. However, controlling small amounts of sorbent can be challenging, and increasing the volume of the solution can generate significant amounts of radioactive waste. We also used UV-vis spectra analysis to investigate the formation of solid phases. We found that a 100 mg L-1 uranium solution resulted in the formation of colloidal particles in the solid phase after 2.5 hours at pH 6, while at pH 4, no significant changes in absorbance were observed over 120 hours, indicating a stable ion phase. Based on these conditions, we obtained an excellent adsorption capacity of 110 mg g-1.

PURPOSES : In this study, a method to use magnesium phosphate ceramic (MPC) concrete for the surface maintenance of airport pavements with jointed concrete is developed. METHODS : To investigate the application of a material incorporated with MPC for the surface maintenance of airport pavements with jointed concrete, structures with various cross-sections and thicknesses were constructed. The cross-section of the structure was modeled for the surface maintenance of four types of pavements and typical pavement construction processes, such as cutting, cleaning, production and casting, finishing, hardening, and joint reinstallation. Subsequently, the hours required for each process was determined. RESULTS : The MPC concrete used for the surface maintenance of airport pavements with jointed concrete demonstrate excellent performance. The MPC concrete indicates a compressive strength exceeding 25 MPa for 2 h, and its hydration heat is 52.9 ℃~61.2 ℃. Meanwhile, the crushing and cleaning performed during the production and casting of the MPC require a significant amount of time. Specifically, for a partial repair process, a total of 6 h is sufficient under traffic control, although this duration is inadequate for a complete repair process. CONCLUSIONS : MPC concrete is advantageous for the surface maintenance of airport pavements with jointed concrete. In fact, MPC concrete can be sufficiently constructed using existing concrete maintenance equipment, and partial repair works spanning a cross-sectional area of 11 m2 can be completed in 1 d. In addition, if the crushing and cleaning are performed separately from production and construction, then repair work using MPC concrete can be performed at a larger scale.

The oxygen evolution reaction (OER) is very sluggish compared to the hydrogen evolution reaction (HER). Considering this difference is essential when designing and developing a cost-effective and facile synthesis method for a catalyst that can effectively perform OER activity. The material should possess a high surface area and more active sites. Considering these points, in this work we successfully synthesized sheets of cobalt phosphate hydrate (CP) and sulphurated cobalt phosphate hydrate (CPS) material, using simple successive ionic layered adsorption and reaction (SILAR) methods followed by sulfurization. The CP and CPS electrodes exhibited overpotentials of 279 mV with a Tafel slope of 212 mV dec1 and 381 mV with a Tafel slope of 212 mV dec1, respectively. The superior performance after sulfurization is attributed to the intrinsic activity of the deposited well-aligned nanosheet structures, which provided a substantial number of electrochemically active surface sites, speeded electron transfer, and at the same time improved the diffusion of the electrolyte.

Spent nuclear fuels are temporarily stored in nuclear power plant site. When a problem such as cracking of spent nuclear fuel assembly or cladding occurs or uranium that has not been separated during the reprocessing remains, it is necessary to treat it. The borosilicate glasses have been considered to vitrify whole spent nuclear fuel assembly. However, a large amount of Pb addition was necessary to oxidize metals in assembly to make them suitable for oxide glass vitrifcation. Furthermore, these borosilicate glasses need to be melted at high temperatures (> 1,400°C) when UO2 content is more than 20wt%. Iron phosphate glasses can be melted at a relatively low temperature (< 1,300°C) even with a similar UO2 addition. A composition of iron phosphate glass for immobilization of uranium oxide has been developed. The glasses have glass transition temperatures of ~555°C that are high enough to maintain its phase stability in geological repositories. The waste loading of UO2 in the glass is ~33.73wt%. Normalized elemental releases from the product consistency test were well below the US regulation of 2 g/m2. Nuclear criticality safety and heat generation in deep geological repositories were calculated using MCNP and computational fluid dynamics simulation, respectively. The glass had effective neutron multiplication factor (keff) of 0.755, which is smaller than the nuclear- criticality safety regulation of 0.95. Surface temperature of the disposal canister is expected to lower than the limit temperature (< 100°C). Most of the U in the glass is in the 4+state, which is more chemically durable than the 6+state. As a result of long-term dissolution experiment, chemically-durable uranium pyrophosphate (UP2O7) crystals were formed.

High-temperature friction performances of graphite blocks (GBs) and zinc phosphate impregnated graphite blocks (IGBs) were evaluated under various friction temperatures. The surface of IGB exhibited extremely lower average friction coefficient values, that was 0.007 at 400 °C and 0.008 at 450 °C, in comparison to that of GB (0.13 at 400 °C and 0.16 at 450 °C, respectively). The worn surface of IGB in the high-temperature friction test was smoother and more complete than that of GB. The wear under high temperature and load caused the transformation of zinc pyrophosphate to zinc metaphosphate and the formation of a continuous large-area boundary lubrication layer combined with graphite and metallic element on the wear surface. The superior tribology property of IGB could be attributed to the digestion of iron oxides by tribo-chemical reactions and passivation of the exposed dangling covalent bonds. Specifically, the layered structure generated on the IGB wear interface effectively decreased the adhesive forces and prevented the surface from serious damage.

Spinach (Spinacia oleracea L.), a green leafy vegetable, is well known as a functional food due to its biological activities. Vascular calcification is associated with several disease conditions including atherosclerosis, diabetes, and chronic kidney disease (CKD), and is known to raise the risk of cardiovascular diseases related morbidity and mortality. However, there are no previous studies that have investigated the effects of fermented spinach exract (FSE) against aortic and its underlying mechanisms. Therefore, this study investigated the effects and action of possible mechanisms of FSE on inorganic phosphate (PI)-induced vascular calcification in ex vivo mouse aortic rings. PI increased vascular calcification through calcium deposition in ex vivo aortic rings. FSE inhibited calcium accumulation and osteogenic key marker, runt-related transcription factor 2 (Runx2), and bone Morphogenetic Protein 2 (BMP-2) protein expression in ex vivo aortic rings. And, FSE inhibited PI-induced extracellular signal-regulated kinase (ERK) and p38 phosphorylation in ex vivo aortic rings. These results show that FSE can prevent vascular calcification which may be a crucial way for the prevention and treatment of vascular disease association with vascular calcification.

Magnesium potassium phosphate cements (MKPCs) are prepared by the acid-base reaction of dead burned magnesia (MgO) and monopotassium phosphate (KH2PO4). Low-pH cementitious materials such as MKPCs are currently of interest for the geological disposal of nuclear waste. MKPCs have advantages such as high early strength, high bonding strength, small drying shrinkage, low permeability, and high sulfate resistance. According to the results of previous studies, it is known that cesium, strontium, and cobalt are immobilized in the form of MgCsxK1−xPO4·6H2O, MgxSr1−xKPO4·6H2O, and Co3(PO4)2, respectively, in MKPCs. However, these results were predicted based on thermodynamic data, not directly observed precipitates to clearly show the evidence. Therefore, in this study, we directly analyzed the immobilized forms of Cs, Sr, and Co, respectively. CsNO3, Sr(NO3)2, and Co(NO3)2·6H2O powders (0.3 mol each) were mixed individually in each of the MKPC suspensions. The suspensions in which KH2PO4 was dissolved were pH 4.3 and the dissolution of MgO decreased the H+ concentration, raising the pH close to 11. The hydration products according to pH evolution in the MKPC suspensions were analyzed, and the change in the concentration of ions in the aqueous solution was also measured. An aqueous solution was obtained using a syringe filter (0.45 μm) to analyze the ion concentrations in the solution of the suspension. The collected solutions were diluted with nitric acid and analyzed using inductively coupled plasma mass spectrometry. To characterize the solid phases, the suspensions were obtained with a pipette at specific times and filtered under a vacuum in a Buchner funnel. Because the amounts of hydration products including Cs, Sr, and Co were small, it was not observed by XRD and TGA analysis, but their components could be analyzed by SEM-EDS. The final precipitate forms of Cs, Sr, and Co in the MKPC matrix are MgCsPO4·6H2O, SrHPO4, and Co3(PO4)2·8H2O, respectively.

Tributyl phosphate (TBP) is a well-known and important compound in the nuclear industry for the nuclear fuel reprocessing, and it is also used in a various field such as plastic industry as antifoaming agent. Untreated organic pollutants in TBP can remain in the soil water and cause serious environmental pollution, thus it should be degraded through environmentally friendly methods. The non-thermal plasma-based advanced oxidation process (AOP) is one of the most widely studied and best developed processes owing to its simple structure and ease of operation. In this study, a plasma-based AOP was stably generated using submerged multi-hole dielectric barrier discharge (DBD) and applied to relatively high concentration of TBP solution. A submerged DBD plasma system was designed to directly interact with water, thereby producing reactive oxygen species (ROS) and functioning as a powerful oxidizer. Additionally, UV, O3, and H2O2 are generated by the developed plasma system without using any other additives to produce OH radicals for degrading organic pollutants; therefore, this system circumvents the use of complex and advanced oxidation processes. The electrical properties and concentrations of the active species were analyzed to establish optimal plasma operating conditions for degrading TBP solution. The results were analyzed by measuring the total organic carbon (TOC) and changes in solution properties. Based on these results, a degradation mechanism of TBP solution is proposed. After 50 min of plasma treatment, the concentration of TOC was gradually decreased. Consequently, we found that plasma-based AOP using submerged multi-hole DBD has advantages as an alternative technology for degrading organic pollutants such as TBP solution.

The decommissioning of a nuclear power plant generates large amounts of radioactive waste, which is of several types. Radioactive concrete powder is classified as low-level waste, which can be disposed of in a landfill. However, its safe disposal in a landfill requires that it be immobilized by solidification using cement. Herein, a safety assessment on the disposal of solidified radioactive concrete powder waste in a conceptual landfill site is performed using RESRAD. Furthermore, sensitivity analyses of certain selected input parameters are conducted to investigate their impact on exposure doses. The exposure doses are estimated, and the relative impact of each pathway on them during the disposal of this waste is assessed. The results of this study can be used to obtain information for designing a landfill site for the safe disposal of low-level radioactive waste generated from the decommissioning of a nuclear power plant.

A wire rod, a material for multistage cold forging, is subjected to spheroidization and low annealing heat treatment to secure formability, and a phosphate coating treatment on the material surface to secure lubricity. The film layer produced by the phosphate treatment process is involved in adhesion to the material surface, adhesion to the forging die surface, and lubricity. This results in the increase or decrease of the forming load and the increase or decrease of the die life in the cold forging process. In particular, as the cold forging process progresses, the phosphate film is damaged and the original performance is deteriorated, so there is a high possibility of process defects. In case of excessive damage, the film is completely lost and die soldering occurs. Therefore, in this study, quantitative criteria for phosphate film damage are presented and the effect on the cold forging process is analyzed based on this to improve process analysis prediction accuracy. Therefore, in this study, quantitative criteria for phosphate film damage are presented, and based on this, the friction coefficient in the multi-stage cold forging process is to be derived.

The adsorption process using GAC is one of the most secured methods to remove of phosphate from solution. This study was conducted by impregnating Cu(II) to GAC(GAC-Cu) to enhance phosphate adsorption for GAC. In the preparation of GAC-Cu, increasing the concentration of Cu(II) increased the phosphate uptake, confirming the effect of Cu(II) on phosphate uptake. A pH experiment was conducted at pH 4-8 to investigate the effect of the solution pH. Decrease of phosphate removal efficiency was found with increase of pH for both adsorbents, but the reduction rate of GAC-Cu slowed, indicating electrostatic interaction and coordinating bonding were simultaneously involved in phosphate removal. The adsorption was analyzed by Langmuir and Freundlich isotherm to determine the maximum phosphate uptake(qm) and adsorption mechanism. According to correlation of determination(R2), Freundlich isotherm model showed a better fit than Langmuir isotherm model. Based on the negative values of qm, Langmuir adsorption constant(b), and the value of 1/n, phosphate adsorption was shown to be unfavorable and favorable for GAC and GAC-Cu, respectively. The attempt of the linearization of each isotherm obtained very poor R2. Batch kinetic tests verified that ~30% and ~90 phosphate adsorptions were completed within 1 h and 24 h, respectively. Pseudo second order(PSO) model showed more suitable than pseudo first order(PFO) because of higher R2. Regardless of type of kinetic model, GAC-Cu obtained higher constant of reaction(K) than GAC.