Release Of Vanadium Research Articles

Fe(III) reduction mediates vanadium release and reduction in vanadium contaminated paddy soil under different organic amendments

Vanadium(V) contaminated soil is abundant in iron(Fe) oxides due to co-occurrence of V and Fe bearing minerals. However, biogeochemical transformation of redox-active V and Fe in soil, and the bacteria involved, has remained less investigated. This study explored the extent to which microbial mediated organic decomposition coupled to Fe(III) reduction contributed to V(V) release/reduction in V-contaminated paddy soil under different organic amendments. Soil flooding decreased toxic reducible V while increased less toxic oxidizable V. Glucose and straw promoted V(V) release with temporarily increasing V(V) concentration by 73.59–106.34 mg/kg compared to the control treatment and subsequently promoted V(V) reduction with decreasing V(V) to concentrations eventually similar to the control treatment. Biochar incorporation under glucose and straw amendments moderately alleviated V(V) release. The significantly positive correlation between Fe(II) and V(V) concentrations during the V solubilization process indicated a temporal coupling of Fe(III) reduction and V(V) release. Clostridium, and Massilia mediated Fe(III) reductive dissolution and V(V) release, while Anaeromyxobacter, Sphingomonas, Bryobacter, Acidobacteriaceae and Anaerolineaceae contributed to V(V) reduction. This study provides a deeper understanding of V biotransformation coupled to Fe and C cycling and suggests a remediation strategy for V-contaminated soils via regulating Fe(III) reduction to weaken V(V) release or to promote V(V) reduction.

Nitrate-induced mobilization of trace elements in reduced groundwater environments

Groundwater is an essential source for drinking water production. Nitrate infiltration into groundwater due to over-fertilization can cause a potential risk for groundwater quality. Pyrite and other geogenic minerals can be oxidized and trace metals consequently released into water, e.g., nickel and uranium.To achieve a better understanding of the nitrate-induced mobilization of metals, this study investigated the release of antimony, arsenic, chromium, cobalt, molybdenum, uranium, and vanadium from three different reduced sediments after nitrate addition. The experiments were conducted as batch and soil column tests under oxygen-free conditions. In addition to the ORP, the pH value was a relevant driver for the metal mobilization due to pH dependent adsorption and ion exchange processes. Uranium concentrations in the water increased with increasing redox potential. Also, antimony and, to a lesser extent, molybdenum showed higher mobilization at higher ORP as well as at higher pH values. On the contrary, arsenic and cobalt was immobilized with increasing redox potential. Pourbaix diagrams demonstrated very complex species distributions even in synthetic water. The mobilization of trace metals is expected to be also influenced by the type of surrounding rocks and water quality parameters such as dissolved organic carbon.

Reactive media constructed wetland for phosphorus removal: assessing the opportunity and challenges

ABSTRACT Reactive media present an alternative to gravel in constructed wetlands and have the potential to sustainably and efficiently remove phosphorus from wastewater. In this study, a full-scale steel slag wetland has been operated for its whole lifecycle at which 1.39 mg P/g media were retained. During its lifecycle, this wetland met strict consents below 0.5 mg P/L for the first 6 months and was operated for 266 and 353 days before the effluent phosphorus concentration rose above the typical consents of 1 and 2 mg P/L, respectively. A detailed analysis of the system demonstrated that the performance was directly associated with the release of materials from the media into the water which in turn affected other critical parameters such as pH. Further analysis of the media suggested that greater understanding was needed concerning the role of carbonates and in particular calcite if steel slag is to be effectively managed for use on constructed wetlands. Importantly, controlled release of calcium oxide from the media surface is required by managing the concerns of pH and vanadium release.

Electrodeposition of Zn and Cu Nanoparticles into TiO2 Nanotubes on Ti6Al4V: Antimicrobial Effect against S. Epidermidis and Cytotoxicity Assessment

Surface modification of the Ti6Al4V alloy (ASTM grade 5), with the fabrication of vertically oriented TiO2 nanotubes, has been receiving increasing attention both as a way to provide advanced bioactive features and the ability to act as reservoirs for a localized, controlled drug release. In this work, TiO2 nanotubes were grown on the surface of a Ti6Al4V alloy through electrochemical anodization. An ethylene glycol-based electrolyte containing 0.5 wt.% NH4F and 2.5% (v/v) H2O was used. Post-anodizing heat treatments at 500 °C in air atmosphere were performed to achieve a crystalline oxide layer with a higher mechanical stability. Following these treatments, Zn or Cu nanoparticles were incorporated into the nanotubular structures through electrodeposition processes. Then, the antimicrobial performance of the obtained surfaces was assessed against Staphylococcus epidermidis, a Gram-positive bacterium common in implant-related infections. Lastly, the cytotoxicity of the produced surface was evaluated against MC3T3-E1 mouse pre-osteoblast cells. In general, Cu-doped TiO2 nanotubes presented an almost total antimicrobial action, while Zn doped samples had a lower, but still significant antibacterial effect. However, a highly cytotoxic effect against MC3T3-E1 cells was observed on all anodized samples due to the release of vanadium from the alloy. In spite of this, the surface modification reported in this work can be a valid solution for existing commercially available orthopedic implants, considering that similar solutions were already studied in in vivo assays.

A novel process of gradient oxidation roasting-acid leaching for vanadium extraction from stone coal

Efficient green vanadium extraction is a research direction of stone coal. This study focuses on efficient green vanadium extraction of stone coal. A gradient oxidation roasting-acid leaching (GORA) process was proposed, which is additive-free and effectively improves the leaching efficiency with preliminary oxidation and further high-temperature reoxidation. The results of this study showed that 95.59 % of −0.074 mm particles were the most appropriate. The suitable roasting temperature and time for preliminary oxidation roasting were 650 °C and 0.5 h, respectively. A porous structure was formed with a specific surface of 2.61 m2/g, and a total pore volume of 0.0164 cm3/g. Further, the optimal conditions of high-temperature reoxidation roasting were 850 °C, 3 h, 35 % O2, and 600 ml/min. The best V2O5 leaching rate of the GORA was 68.89 %, which was 36.23 % higher than that of the raw ore. It was discovered that stone coal could withstand high temperatures without sintering after preliminary roasting. High-temperature reoxidation is a prerequisite for destroying the lattice of vanadium-bearing minerals and promoting vanadium release. Meanwhile, the loose and porous honeycomb particle products promoted subsequent gas–solid and liquid–solid reactions. Therefore, this study provides a novel and effective method for extracting vanadium from stone coal.

ВЕРТИКАЛЬНЫЕ ТИТАНОВЫЕ ВИНТЫ С МОДИФИЦИРОВАННЫМ ПОКРЫТИЕМ ДЛЯ ПОВЫШЕНИЯ НАДЁЖНОСТИ ФИКСАЦИИ И СТАБИЛИЗАЦИИ АБАТМЕНТОВ К ПЛАТФОРМЕ ДЕНТАЛЬНЫХ ИМПЛАНТАТОВ

Vertical screws of abutments after dental implantation tend to loosen, unscrew and break, which is associated with low strength, tribological and corrosion properties of screw material under stress and aggressive environment in the oral cavity. The main causes of problems with dental screws are a decrease in their fatigue strength due to defects, residual tensile stresses and hydrogen pickup of surface layer, as well as the process of fretting corrosion that occurs under conditions of micro-displacement under cyclic loads of conditionally stationary tribocoupling. The design and operational characteristics of abutment screws, the main problematic properties of titanium materials are considered, the calculated dependences of torque, pre-tightening force, friction coefficients in thread and on support surface are given. The analysis of numerical values of these parameters is given. It is concluded that the use of vertical titanium screws with functional coatings is one of the ways of improving the reliability of the dental implantation system. The results of studies of the BioPateks diamond-like coating of the a-C:H/a-SiC-Ag system for vertical titanium abutment screws applied using cold atmospheric plasma are presented. The effectiveness of this coating has been demonstrated in metallographic analysis, static tensile tests, tribological studies, tests under microabrasive wear conditions, studies of barrier properties from the release of toxic vanadium and aluminum ions, studies of surface defects during fretting fatigue. The BioPateks coating and its application technology can be used both in industrial and in clinical and laboratory conditions. For these purposes, small-sized and low-energy equipment is used.

Cyanobacterial blooms increase the release of vanadium through iron reduction and dissolved organic matter complexation in the sediment of eutrophic lakes.

Vanadium (V), a hazardous environmental contaminant, can be highly toxic to aquatic or even human life. Nonetheless, knowledge of its redox geochemistry and mobility in sediments, especially those of eutrophic lakes, remains limited. In this study, we combined in situ high-resolution sampling and laboratory simulation experiments for monitoring soluble and labile V to reveal the mobilization mechanism of V in the sediment of Lake Taihu. The results showed that the concentration of soluble V (1.18-5.22µg L-1) exceeded the long-term ecotoxicology limitation proposed by the government of the Netherlands. The highest value appeared in summer (July to September), with an average concentration of 3.87µg L-1, which exceeded the short-term exposure limit. The remobilization of V in summer was caused by the combined effect of the reduction of Fe(hydr)oxides and dissolved organic matter (DOM) complexation, which accelerated the release of associated Fe-bound V and increased the solubility of DOM-V. Additionally, V showed high mobility in winter, owing to the species of V(Ⅲ)/V(Ⅳ) being oxidized to V(Ⅴ) with higher solubility. It is noteworthy that the elevated remobilization of V in sediments increases the risk of V release from sediments, which poses the threat of water V pollution in Lake Taihu.

Constraining the major pathways of vanadium incorporation into sediments underlying natural sulfidic waters

Vanadium (V) is a redox-sensitive trace metal. Interconversion between different vanadium species (e.g., VIII, VIV, VV) occurs rapidly in association with changes in redox conditions in natural environments. Different vanadium species exhibit variable geochemical behavior that impacts if and how they are sequestered into sediments, which makes vanadium a useful proxy for ancient ocean redox conditions. However, we still lack constraints on how different dissolved vanadium sink pathways impact distributions of vanadium in water column, pore waters, and sediments, especially in natural sulfidic settings. In the present study, we combined field and experimental data to constrain the major scavenging processes that influence the partitioning of vanadium between aqueous and solid phases to provide an improved picture of vanadium geochemical cycling under anoxic-sulfidic conditions. We find that in the sulfidic bottom waters and sediment pore waters of the Chesapeake Bay, vanadium concentrations are correlated with manganese (Mn) concentrations in both aqueous and solid phases. Our experimental results support our interpretation that elevated concentrations of vanadium in anoxic-sulfidic waters result from the release of vanadium due to desorption from and/or dissolution of Mn oxides in anoxic/sulfidic waters. While sorption of vanadium results in strongly adsorbed complexes on both Mn oxides and pyrite surfaces, vanadium preferentially sorbs to Mn oxides rather than to pyrite. Thus, the impact of Mn oxides on vanadium geochemistry is greater than that imposed by scavenging via sorption on pyrite, although both processes should be considered. Mn oxides also have a greater impact on vanadium geochemistry than reductive formation of solid V(OH)3 by H2S. Sorption of vanadium is sensitive to pH conditions (especially in anoxic waters), moderately sensitive to ionic strength, and weakly sensitive to phosphate concentrations. In addition, our results show that as waters become more sulfidic, dissolved V/Mn molar ratios increase, whereas solid phase V/Mn molar ratios decrease, indicating that the V/Mn molar ratio can be used to trace redox changes. Finally, we investigate the V/Mn record of black shales that span the Proterozoic and Phanerozoic to show a framework of utilizing this proxy with applicability to identify changes in redox conditions associated with both oxygenation and anoxic events in ancient oceans.

Effect of mechano-chemical activation with NaF on improved acid leaching of vanadium-bearing shale

Vanadium extraction from vanadium-bearing shale by direct acid leaching is currently restricted owing to the inefficient release of vanadium from mica, which consumes a large amount of acid. To overcome this limitation, this study developed a mechano-chemical activation-assisted acid-leaching process. Further, the effects of the mechano-chemical activation parameters on the vanadium-bearing shale and vanadium dissolution in an acid system were examined using the following conditions: ball-to-pulp ratio: 50 to 1, pulp density: 50%, NaF activator: 5 wt%, activation time: 30 min, sulfuric acid concentration: 12 vol%, leaching time: 6 h, leaching temperature: 95 °C. These conditions increased the vanadium leaching efficiency from 82.3% to 90.3%. The mechano-chemical activation treatment exposed the fresh muscovite surface, promoting the preferential adsorption of fluoride to form stable SiF and AlF bonds. This behavior induced a beneficial reaction surface on muscovite with a low energy barrier for subsequent leaching. During the leaching process, the weakened SiO and AlO bonds could be more easily broken by H+ attack, thus accelerating muscovite dissolution and boosting the vanadium leaching efficiency.

Vanadium mobilization and redistribution during mineral transformation of vanadium-titanium magnetite tailings with different weathering degrees

Due to the long-term open stockpile, the release of vanadium (V) from V-containing tailings will cause continuous V pollution in the mining area. Previous studies on the concentration and speciation of V primarily focused on surface tailings at a regional scale. However, the mobilization and redistribution of V within the tailing profile during the mineral transformation of tailings remain unclear. Herein, a series of concentrations of V(V) (0–200 mg L−1) solutions were added to the vanadium‑titanium magnetite tailings at different depths separately to simulate the redistribution of dissolved V released from tailings in the solid phase of tailings. During the 56-day incubation, the concentrations of aqueous V in the surface tailings were significantly lower than those in the deep tailings under the same level of V(V) treatment, indicating that the shallow tailings had a stronger immobilization capacity for V than the deep tailings. Morphological analysis and color overlays of the elements demonstrated that most of V was immobilized into the tailings and adsorbed or precipitated by the Fe (hydr)oxides in the tailings in 200 mg L−1 V(V) treatment. This portion of V mainly occurred in acid-soluble and reducible fractions in the tailings after a 7-day incubation, accounting for >71.7 % of the total V. However, these two factions of V with high bioavailability were gradually mineralized over time and transferred to residual V, which is difficult to move and has low bioavailability. Mineral phase analysis revealed that additional V(V) favored the formation of melanovanadite (Ca2V8O20·10H2O) and chromium vanadium oxide (Cr2V4O13) in the tailings. This study reveals that the dissolved V influenced the fractionation and redistribution of solid-phase V during tailing weathering, improving the understanding of the geochemical processes of V in tailing profiles and providing important guidance for the management of V-containing tailings.

Vanadium(V) reduction by using a by-product of the yellow phosphorus industry

Release of vanadium(V) from industry has threatened the environment and human health. In this paper, a removal method of vanadium(V) is proposed using a by-product of the yellow phosphorus industry (phosphorus-iron) as a reducing agent. The thermodynamics analysis shows that the Gibbs free energy is always negative from 0 to 100 °C, indicating a spontaneous process. Effect of the phosphorus-iron slag/sulfuric acid dosage and temperature on the removal efficiency is comprehensively studied, and the kinetics parameters are calculated based on a quasi-first order reaction kinetics model. Results indicate that vanadium(V) can be entirely reduced by using phosphorus-iron slag, the frequency factor and apparent activation energy are 3.23 × 109 min−1 and 64.50 kJ·mol−1 for vanadium(V) reduction. Based on above results, a lab-scale reactor is constructed and achieves a removal efficiency of ∼100% and a treatment capacity of 200 ml vanadium(V) solution (2 g·L–1) within 3 h. This work demonstrates the feasibility of vanadium(V) reduction using phosphorus-iron slag as a reducing agent in applications.

Improving vanadium extraction from refractory stone coal by suspension roasting

AbstractAn innovative suspension roasting−leaching technology in the atmosphere was proposed to improve the vanadium extraction from refractory stone coal. The leaching rate of vanadium was enhanced from 20% previously to 47.14% by present technology at a roasting temperature of 800 °C, a roasting time of 20 min, and a gas flow rate of 400 mL/min. Throughout the suspension roasting process, the surface of the stone coal gradually became rough and irregular. The specific surface area of the particles increased and the lamellar structure of the silicate minerals was destroyed, contributing to the release of vanadium. Meanwhile, the vanadium in the stone coal was oxidized to V(V) or V(IV). The results indicated that the leaching rate was improved owing to the release and transformation of vanadium in the suspension roasting.

Effects of secondary release of chromium and vanadium on soil properties, nutrient cycling and bacterial communities in contaminated acidic paddy soil

Although the contamination situation of chromium (Cr) and vanadium (V) have been revealed, the effects of their re-release on ecological risk in contaminated acidic paddy soil are unclear. To evaluate the effects, we assigned soil microcosms across three different concentration (100, 200, 300 mg/L) and introduced Cr and V alone or combination into an already slightly contaminated acidic soil. We found that Cr and V alone or interacted to increased soil bioavailable-metals, changed soil properties and nutrients to varying degrees. Meanwhile, soil ammoniacal nitrogen (NH4+-N) and nitrate nitrogen (NO3−-N) contents, nitrogen (N) -cycling enzyme activities, microbial mass N were significantly influenced by Cr addition. Which demonstrated that Cr re-release may disturb soil N cycle. However, V alone significantly improved soil NO3−-N contents, cellulase and dehydrogenase activities, soil respiration intensity and microbial mass carbon: nitrogen. Meanwhile, V addition also decreased bacterial diversity while Cr addition increased bacterial diversity and shaped new bacterial community, some V(V) and Cr (VI) reducing bacteria were identified. Heatmap of Pearson correlation and Redundancy analysis showed that NH4+-N, NO3−-N, Potassium, Phosphorus, and Cr played an important role in bacterial community structure. These findings suggested that re-release of Cr and V disturbed soil function and raised ecological risks, and the power to destroy the ecosystem stability originated from Cr was much stronger than V. This study was contributed to understand the effects of Cr and V re-release on microecology in contaminated acidic agricultural soil.

Improvement on bioleaching interfacial behavior between Bacillus mucilaginosus and vanadium-bearing shale by surfactant additive

Effects of surfactant SDS (Sodium Dodecyl Sulfate) on bacterial metabolism and vanadium leaching effect by Bacillus mucilaginosus (B. mucilaginosus) were explored. The results indicated that the bacteria adsorption dissolution effect and the organic acid dissolution effect could extract 29.12% and 35.21% of vanadium, respectively, which were 9.70% and 6.27% higher than those without SDS. SDS significantly enhanced the bacteria adsorption dissolution effect and the organic acid dissolution effect of B. mucilaginosus on vanadium-bearing shale, and the bacteria adsorption dissolution effect to improve the vanadium leaching efficiency was more remarkable. When the bioleaching time began to enter the bacteria stable growth phase and the stable pH phase, the EPS (Extracellular Polymeric Substances) concentration decreased by 73.1 mg/L and 68.2 mg/L under the action of SDS, respectively. However, the bacteria’s adsorbance on the mineral surface increased by 0.07 × 109 cells/mL and 0.13 × 109 cells/mL, respectively. The improvement on the bacteria adsorption dissolution effect with SDS was then revealed. SDS decreased the secretion of EPS, reduced the bacterial agglomeration, increased the adsorption capacity of bacteria, and thereby strengthened the dissolution effect. Furthermore, it was found that the H+ concentration in the leachate increased by 1.36 × 10−5 mol/L and 4.33 × 10−5 mol/L, respectively. The enhancement on the organic acid dissolution effect with SDS was also achieved. The increase of the organic carboxylic acid metabolites was beneficial to further remove the hydroxyl groups in the vanadium-bearing muscovite crystal lattice, and strengthen the destruction of the basic structure of silicon-oxygen tetrahedron and aluminum-oxygen octahedron, resulting in the release of vanadium.

Crystal Transformation of Sericite during Fluidized Roasting: A Study Combining Experiment and Simulation

Fluidized roasting is an efficient method to promote vanadium extraction from V-bearing mica in shale. In this study, the transformation behavior of V-bearing sericite during fluidized roasting was explored by combining experimental detections and density functional theory (DFT) calculations. TG-MS, XRD, FTIR, and SEM-EDS were used to investigate the characteristics of the roasted sericite samples. The crystal parameters of V-bearing sericite were calculated with Materials Studio. The results showed that dehydroxylation was the main reaction during roasting, which occurred between 650 °C and 960 °C. After being roasted at 900 °C for 2 h, hydroxyls were completely removed. The calculation results show that −OH was removed between the metal ions in the sericite O-layer, which turned the hexa-coordinate of V3+, Al3+, and Fe3+ into pentacoordinate. Through electronic rearrangement, the bond lengths between two ions connected by −OH were shortened from 0.18~0.20 nm to 0.17 nm. However, some chemical bonds were grown, which indicates that they are weaker and easier to transform. In addition, twisted six-membered rings were formed with obvious angle changes on the (0 0 1) surface. Furthermore, Mulliken’s overlap populations of some V-O, Al-O, and Fe-O were decreased. Therefore, dehydroxylation is a determining factor in the destruction of sericite crystals during fluidized roasting, which also promotes vanadium release from shale.

Characteristics of vanadium release from layered steel pipe scales to bulk, steady, and occluded water in drinking water distribution systems

The release of vanadium (V) from drinking water distribution systems (DWDS) can endanger water quality and human health. Therefore, in this study, the physicochemical characteristics of old steel pipe scales were analyzed, and dynamic pipeline devices were constructed. Subsequently, static release experiments were conducted to find an optimum scale-water ratio and investigate the release behaviors of V in lumpy pipe scales. Besides, the release behaviors of V from layered pipe scales to bulk, steady, and occluded water under the combined effect of multiple water quality conditions were studied for the first time. Computational fluid dynamics (CFD) was adopted to explain the release behaviors of V in the dynamic pipeline. Results revealed that the adsorption performance of the layered scales decreased in the order of surface layer > porous core layer > hard shell-like layer. The release behaviors of V in the lumpy pipe scales were mainly divided into rapid desorption and colloidal agglomeration stages. The Double constant and Weber–Morris models can suitably describe release stage I (R2 > 0.919) and release stage II (R2 > 0.948), respectively. Notably, the release of V was aggravated by low pH, high temperature, and high SO42− concentration, and the release amount of V in the pipeline was more significant than the layered pipe scales. Steady water in the gaps of scales contained more V than bulk water, and the malignant occluded water encased in scales contained relatively low V concentrations. In short, the main mechanism of V release was competitive adsorption in the early stage, and pH was the main influencing factor in the later stage. The above results are of great significance for revealing the release behaviors of V and reducing its release in DWDS.

Multistage suspension roasting of refractory stone coal: Enhanced extraction based on decarburization and vanadium oxidation

An innovative multistage suspension roasting technology for vanadium leaching from stone coal is proposed. The results reveal that 53.13% of the carbon is removed during the first-stage of roasting. At the same time, the vanadium-bearing mica lattice is disrupted, and the release of hydroxyl groups and vanadium leads to the production of dehydrogenated mica. In the second-stage of roasting, the carbon is almost completely removed, and the structure of mica is further destroyed and partially converted to feldspar under high-temperature roasting. The results show that under optimal conditions, i.e., first-stage roasting temperature of 800 °C, roasting time of 20 min, gas flow rate of 400 mL·min−1, the oxygen concentration of 20% and second-stage roasting temperature of 700 °C, roasting time of 1 h, and oxygen concentration of 20%, the vanadium leaching rate increases from 20% using conventional technology to 51.42% by using the presented technology.

Soil indigenous microorganisms alleviate soluble vanadium release from industrial dusts

Vanadium-bearing dusts from industrial processes release abundant toxic vanadium, posing imminent ecological and human health concerns. Although the precipitation of these dusts has been recognized as the main source of soil vanadium pollution, little is known regarding the interrelationships between industrial dusts and soil inherent compositions. In this study, the interactions between dusts from vanadium smelting and soil indigenous microorganisms were investigated. Soluble vanadium (V) [V(V)] released from industrial dusts was reduced by 41.5 ± 0.39% with soil addition, compared to water leaching. Reducible fraction accounted for the highest proportion (55.1 ± 1.73%) of vanadium speciation in the resultant soils, while residual vanadium fraction increased to 83.7 ± 3.22% in the leached dusts. Functional genera (e.g., Aliihoeflea, Actinotalea) that transformed V(V) to insoluble vanadium (IV) alleviated dissolved vanadium release. Nitrate/nitrite reduction and glutathione metabolisms contributed to V(V) immobilization primarily. Structural equation model analysis indicated that V(V) reducers had significant negative impacts on soluble V(V) in the leachate. This first-attempt study highlights the importance of soil microorganisms in immobilizing vanadium from industrial dusts, which is helpful to develop novel strategies to reduce their environmental risks associated to vanadium smelting process.

Transformation behaviors of vanadium and nickel during petroleum coke and coal co-gasification

The transformation behaviors of vanadium and nickel during petroleum coke co-gasification with coal may cause ash-related fouling, slagging, and corrosion problems. In this work, we investigated the evolution of occurrence modes, volatilization behaviors, and speciation of vanadium and nickel in the process of steam co-gasification of petroleum coke and coal over the temperature range of 1100–1500 °C. The results showed that the main chemical states of vanadium and nickel in raw petroleum coke were organic matter and “stable forms”, of which vanadium and nickel associated with organic matter were thoroughly converted into other chemical states. The volatilities of vanadium and nickel in petroleum coke increased slightly from 1100 °C to 1500 °C, however the addition of coal inhibited their volatilization behaviors. Moreover, residence time had little effect on the release of vanadium and nickel. The crystalline phases of vanadium-bearing species, i.e., vanadium trioxide and coulsonite, as well as those of nickel-bearing species, i.e., nickel sulfide and elemental nickel, were formed in high-temperature ash. In addition, the diffraction peaks corresponding to another vanadium species, calcium orthovanadate, were found in the high-temperature ash of SX40%/HB60% with a coal content of 60 wt.%.

Bio-Tribology and Corrosion Behaviors of a Si- and N-Incorporated Diamond-like Carbon Film: A New Class of Protective Film for Ti6Al4V Artificial Implants.

Ti6Al4V artificial implants are increasingly demanded for addressing human dysfunction caused by an aging population and major diseases. However, they are restricted due to the release of vanadium and aluminum ions in the process of corrosion and wear. This work is aimed to provide a protective film for Ti6Al4V artificial implants, and then, a Si-incorporated diamond-like carbon (Si-DLC) film and Si- and N-incorporated DLC (SiN-DLC) film were deposited on the surface of Ti6Al4V by plasma-enhanced chemical vapor deposition. Results suggest that the thickness of the as-deposited DLC film is approximately 2 μm, and the SiN-DLC film shows the lowest surface roughness (53.0 ± 3.6 nm) compared with the Ti6Al4V and DLC films. The above DLC film possesses high mechanical properties compared with Ti6Al4V, and the SiN-DLC film shows the best resistance to plastic deformation. In addition, the DLC film exhibits high adhesive strength (>13 N) with Ti6Al4V, which is a prerequisite for service in liquid environments. Whether in SBF solution or SBF + BSA solution, the friction coefficient and wear rate of the above DLC film are much lower than those of Ti6Al4V, and the SiN-DLC film displays the optimal tribological properties (0.072 and 1.82 × 10-7 mm3·N-1·m-1, respectively). Moreover, Si-DLC and SiN-DLC films possess similar corrosion resistance but are far better than Ti6Al4V. Cytotoxicity test results show that the SiN-DLC film can significantly improve cell viability and promote cell proliferation to a certain extent. Consequently, the SiN-DLC film is a protective film with more potential for artificial implants.