Molybdenum Compounds Research Articles

Role of molybdenum compounds in enhancing denitrification: Structure-activity relationship and the regulatory mechanisms

The effect and regulatory mechanisms of molybdenum compounds (MoO2, MoS2, MoSe2 and MoSi2) on denitrification were investigated by structure-activity relationships, electrochemical characteristics, microbial metabolism analysis and bacterial community distribution. All the assessed molybdenum compounds exhibited the enhancement effect on denitrification, in the order of MoS2 > MoSi2 > MoSe2 > MoO2, with MoS2 increasing 7.08-fold in 12 h. Analysis of structure-activity relationships suggested that the molybdenum compounds with lower negative redox potential and higher redox reversibility were favorable for promoting denitrification. According to the morphology observation, the interactions between Mo compounds and denitrifying bacteria may be beneficial to extracellular electron transfer. Molybdenum compounds with electron transfer capability facilitated an increase in electron capacitance from 835.1 to 1011.3 μF, promoting the electron exchange rate during denitrification. In the denitrification electron transport chain, the molybdenum compounds upregulated nicotinamide adenine dinucleotide and denitrifying enzyme activity, as well as facilitated the abundance of quinone pools, ATP translocation, and cytochrome c related proteins. Moreover, Mo compounds enriched functional bacteria such as electroactive bacteria and denitrifying functional bacteria. Notably, Mo ions in molybdenum compounds may provide active sites for nitrate reductase, optimizing the electron distribution of the denitrification process and thus improved the partial denitrification efficiency. This work aimed to further understand the regulatory mechanisms of molybdenum on denitrification electron transfer in the compound state and to anticipate the catalytic role of Mo compounds for sustainable water treatment.

In-situ activated arsenic-molybdenum dual-prodrug nanocomplexes for glutathione-depletion enhanced photothermal/chemotherapy against triple-negative breast cancer

Arsenic trioxide, a traditional chemotherapeutic agent, has limitations in clinical application due to its nonspecific delivery and severe systemic toxicity. To address this challenge, we have capitalized on the promising potential of molybdenum-based materials for tumor diagnosis and treatment. We developed a novel multifunctional arsenic-molybdenum dual-prodrug nanocomposite delivery system (AsMo-NCM) by integrating arsenic compounds with molybdenum compounds. This system leverages elevated glutathione (GSH) levels within tumors for specific activation. Within the tumor microenvironment, the system converts Mo(VI) to the more active Mo(V), enabling combined photothermal therapy and photoacoustic imaging for comprehensive diagnosis and treatment. Furthermore, low-toxicity arsenic(V) is converted into highly toxic trivalent arsenic within the high-GSH tumor microenvironment, thereby enhancing tumor cell apoptosis, reducing toxicity to normal tissues, and synergistically improving treatment outcomes. In addition, AsMo-NCM can be biodegraded and rapidly excreted, reducing concerns about their long-term presence and possible toxic effects. The combination of these approaches maximizes GSH depletion, thereby enhancing the synergistic photothermal/chemotherapy effect of AsMo-NCM for precise and effective tumor treatment, thus offering promising prospects for cancer therapy.

Effect of mechanochemically modified MoO3–ZnO on Mo supply to plants when co-granulated with macronutrient fertilizers

Molybdenum (Mo) is an essential micronutrient required for plant growth but is prone to leaching from neutral and alkaline soils. The use of slow-release Mo sources could potentially reduce leaching losses from soils and increase crop yields. In this study, we assessed mechanochemistry as a green method to produce slow-release Mo sources. Molybdenum compounds (MoO3 or (NH4)6Mo7O24·4H2O) were mechanochemically (MC) treated with ZnO to synthesize compounds with a Mo content of 1–36%. Reduced Mo solubility after MC treatment, compared to the initial Mo source, was obtained with the MoO3 source and these composites were used for co-compaction with macronutrient fertilizers. Macronutrient pellets with 0.2% Mo were compacted using the 4% Mo and 36% Mo (characterized as ZnMoO4) compounds. A column dissolution test showed that the 4% Mo compound in a macronutrient carrier (DAP and MAP) only released around 40% of the total Mo compared to 80% for a non-MC treated control over 72 h. Column leaching using two soils revealed that the release behavior of Mo was strongly related to the pH of the leachate, which was affected by both the soil pH and the macronutrient carrier. More Mo was released when the MC-treated compound was co-compacted with diammonium phosphate (DAP) compared to monoammonium phosphate (MAP). The MC-treated compound with 4% Mo showed significantly less leaching than the control without ball milling when co-compacted with both MAP and DAP. In a pot trial with simulated leaching, the uptake of Mo was greater for the MC-treated 4% Mo compound co-compacted into DAP than for the other Mo sources. Overall, our results indicate that MC-treated MoO3–ZnO could be used as a slow-release Mo source in high-rainfall areas.Graphical

Efficient synthesis of graphene oxide-supported molybdenum compounds exhibiting excellent peroxidase-like activity

Two novel compounds involving molybdenum supported by graphene oxide and functionalized with 3-aminopropyltriethoxysilane (APTES) were designed as [(MoO2·H2O)2(L1)]@APTES@GO 3 and [(MoO2·H2O)2(L2)]@APTES-GO 4. These complexes were synthesized by reacting amino-functionalized graphene oxide (APTES@GO) with [(MoO2·H2O)2(L1)] 1, [(MoO2·H2O)2(L2)] 2 in a 1:1 ratio in an ethanolic solution. The structural characterization of the supported compounds was conducted using multiple analytical techniques including Fourier-transform infrared spectroscopy (FT-IR), ultraviolet–visible spectroscopy (UV–vis), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HR-TEM), powder X-ray diffraction (PXRD), Brunauer–Emmett–Teller (BET) surface area analysis, and X-ray photoelectron spectroscopy (XPS). The findings from these characterization methods collectively demonstrated the successful binding of the molybdenum complexes onto the surface of the functionalized graphene oxide. Furthermore, the catalytic performance of these supported compounds was assessed for their peroxidase-like action in the oxidation reactions of o-phenylenediamine (OPD) and 3,3′-diaminobenzidine (DAB). Recycling and reusability investigations indicated that the catalytic activity slightly changes over four consecutive catalytic cycles.

Strong Interaction between Molybdenum Compounds and Mesoporous CMK‐5 Supports Boosts Hydrogen Evolution Reaction

AbstractStrong metal‐support interaction (SMSI) between transition metal nanoparticles and carbon matrix offers significant structure advantages due to the ability to modulate the electronic structure of metal nanoparticles, increase the density of active sites, and improve the conductivity of catalysts. Here, ultrafine nanoparticles of metallic molybdenum compounds (MoP, Mo2C, and MoS2) strongly coupled with mesoporous carbon CMK‐5 are synthesized. The confinement growth of nanoparticles in the pores of CMK‐5 produces encapsulated nanoparticles, affording facilitated electron transfer, and enhancing the HER activity induced by the SMSI effect. The hierarchical nanostructure and strong electronic interactions between the carbon substrate and molybdenum‐based nanoparticles allow efficient mass/electron transport between the carbon substrate and molybdenum‐based nanoparticles, improving the catalytic hydrogen evolution reaction (HER) activity. The effective electron exchange between the Mo species and the CMK‐5 support is studied by X‐ray photoelectron spectroscopy (XPS) measurement, confirming the presence of the SMSI effect. The resulting MoP/CMK‐5 catalyst exhibits outstanding HER performance in alkaline (65 mV@10 mA cm−2), acidic (123 mV@10 mA cm−2), and simulated seawater electrolytes (103 mV@10 mA cm−2), making it one of the most promising catalysts reported for HER. This work provides guidance on designing high‐performance electrocatalysts with SMSI for the enhancement of the electrochemical reaction.

The synthesis and tribological behaviour of a phosphorus-free triazine organic molybdenum as friction modifier

A phosphorus-free triazine-based organic molybdenum compound (DCDM) was designed and synthesized by using the click chemistry approach, and its friction-reducing and anti-wear properties were evaluated in PAO10 base oil. The results indicated that DCDM exhibited excellent tribological performance, with a reduction of approximately 35% in friction coefficient and about 46% in wear scar diameter, due to the synergy effect between Mo and S. Surface analysis by EDS and XPS revealed the formation of MoO3, Fe2(SO4)3, FeS, and MoS2 in the friction film. And it was furhter confirmed that the presence of MoS2 in the friction film contributed most significantly to the enhancement of the friction-reducing and anti-wear properties of the developed triazine-based organic molybdenum compound in PAO10 base oil.

INVESTIGATION OF VARIATION OF SPRAYING CONDITIONS ON VARIATION OF STRENGTH CHARACTERISTICS OF MoCrN COATINGS

Interest in thin-film protective coatings based on nitride compounds of molybdenum and chromium is due to the great prospects for their use as wear-resistant anti-corrosion coatings with high resistance to both external effects in the form of mechanical friction, pressure, and corrosion processes, when exposed to aggressive media, hydrogenation or high temperatures. However, the stability of nitride coatings are primarily determined by the conditions of their obtaining, which not least depend on the power of magnetron sputtering, the variation of which allows you to change the ratio of elements in the composition of coatings. The key objective of this research is to measure the strength characteristics measured by indentation method depending on the conditions of obtaining coatings under variation of sputtering power, as well as to establish the influence of variation of conditions of obtaining thin film coatings on the change of hardness and hardening factors. According to the presented data, changing the conditions of magnetron sputtering by varying the power leads to the formation of stronger stable coatings with high resistance to cracking under changing external load. In the course of research it was determined that changing the conditions of magnetron sputtering coatings, leading to an increase in the concentration of molybdenum in the composition of coatings leads to more than 60–80% hardening, as well as an increase in resistance to cracking under external influences.

A hydrometallurgical process flowsheet for recovering MoO3 from Molybdenite

In this study, a comprehensive hydrometallurgical processing of molybdenite (MoS2) concentrate was investigated. This investigation involved a novel approach combining mechanical activation, leaching, and polyelectrolyte extraction methods. The integrated method effectively addressed the challenge of low leaching rate of molybdenite, resulting in the successful production of high-purity molybdenum trioxide. Milled molybdenite samples were analyzed by different methods of X-ray diffraction, atomic force and electron microscopy, and BET. The increasing trend of the specific surface area during milling was determined by a model fitting which was useful for optimization of milling time. Several leaching reagents were studied to achieve high molybdenum dissolution. The most promising results were achieved through a two-hour process, yielding an impressive leaching efficiency of 80% and a resulting Mo concentration of 6700 mg/L. Molybdenum recovery was efficiently carried out through polyelectrolyte extraction, as confirmed by ICP and CHNS analyses, demonstrating selective precipitation of molybdenum from the solution. The subsequent calcination of the precipitated molybdenum(VI) compound resulted in the production of high-purity molybdenum trioxide. Furthermore, a conceptual hydrometallurgical treatment process for molybdenite concentrate was proposed, aiming to recover molybdenum, sulfuric acid, and copper. This proposed process presents a promising avenue for further exploration in pilot plant studies within the molybdenum industry.

In situ preparation of Cu-Mo-S nanoparticle additive with multi-functional tribological properties

Complex operating conditions pose greater challenges for lubricants, making the development of multi-functional additives a trend. This research introduces a multifunctional Cu-Mo-S nanoparticle (CMS) additive, synthesized using a unique one-pot in situ method. The CMS significantly improved the tribological performance and oxidation stability of base oils. Specifically, 0.5 wt% CMS manifested a remarkable reduction in the friction coefficient and wear volume of ester-based oils by 74.75% and 95.91%, accompanied by a noteworthy increase in the extreme pressure capabilities exceeding 50%, outperforming the individual copper nanoparticles, organic molybdenum, and their mixtures. The remarkable results are attributed to the distinctive structure of CMS, which decomposed during the friction process, forming a continuous friction film containing copper, molybdenum, and iron compounds.

Radiation-Assisted Assembly of a Highly Dispersed Nanomolybdenum-Functionalized Covalent Organic Framework.

Two-dimensional covalent organic frameworks (2D COFs), featuring a large surface area and 1D pore structure, serve as promising scaffolds for anchoring functional guest compounds, which can significantly enhance their performance and thus expand their potential applications. Postsynthetic strategy for COFs functionalization is versatile but challenging because of their tedious procedure with high time and energy consumption, generation of excess reaction waste, and damage to COF crystallinity. We report in this work a general strategy for the synthesis of inorganic nanocompound-functionalized COF composites in a one-pot way. Specifically, a high-crystallinity nanoscale molybdenum compound is successfully introduced into a COF skeleton with high dispersion in situ during the crystallization process of the COF induced by gamma ray radiation under ambient conditions. The obtained COF@Mo composites exhibit remarkable sorption performance for methylene blue and many other organic dyes in aqueous solution with the advantages of ultrarapid uptake dynamics and high removal efficiency.

The effect of anodic polarization parameters of 316L steel in a propylene glycol: Choline chloride eutectic solvent on surface finishing, chemistry and corrosion resistance

AISI 316 alloy steel was polarized anodically in a deep eutectic solvent based on choline chloride and propylene glycol (1:2 M ratio) at the temperature range of 35–75 °C and the current density range of 10–60 mA cm−2. At certain parameters (i.e., 65 °C, 40 mA cm−2), a significant increase in corrosion resistance and surface gloss were found compared to the “raw” steel, but without a spectacular reduction in the roughness of the samples after the polarization process. The SEM analysis carried out allowed us to determine that despite the increase in roughness, micro-irregularities on the steel surface were reduced. Thanks to the ICP-AES tests, it was found that the increase in the overall roughness of the samples could be caused by the excessive leaching of iron from the surface in selected variable process parameters. XPS showed that the anodic polarization process increased the content of chromium and molybdenum compounds on the steel surface. In conclusion, this liquid may be a future replacement for the standard acid baths used for the AISI 316L electrochemical polishing process, but the optimal process conditions (as well as the use of appropriate bath additives) have yet to be determined.

Towards outstanding lubricity performance of proton-type ionic liquids or synergistic effects with friction modifiers used as oil additives at the steel/steel interface.

Anti-wear (AW) additives and friction modifiers (FMs) and their interactions in lubricants are critical to tribological performance. This research investigates the compatibility and synergism of three oil-soluble alkylamine-phosphate ionic liquids with friction modifiers, organomolybdenum compounds. Three proton-based ionic liquids (PILs) were synthesized using a simple, low-cost, and unadulterated procedure as well as the chain lengths of the PILs affected the effectiveness of friction reduction and anti-wear. For example, the effect of a short-chain PIL alone as an additive on friction and wear behavior was not significant, whereas a long-chain PIL was more effective. In addition, PILs appeared to be able to coexist with organic molybdenum compounds and worked synergistically with dialkyl dithiophosphate oxygen molybdenum (MoDDP) to produce a sustained low coefficient of boundary friction (the coefficient of friction approaching 0.042). We proposed a three-stage tribochemical process to explain this interaction of PILs + MoDDP with contact surfaces to form physically adsorbed friction-reducing films and chemically reactive wear-protective films. This study reveals the compatibility and synergistic effects of two common lubricant components, which can be used to guide lubricant development in the future.

Phase formation and hydration of alumina cements on the basis of cobalt‐molybdenum‐containing waste

AbstractThe subject of the research is features of synthesis of alumina cements on the basis of compositions of system CaO – CoO – Al2O3 – MoO3 with use of cobalt‐molybdenum‐containing waste for reception of refractory materials with a complex of the set properties. The processes of phase formation in raw mixtures have been investigated. X‐ray phase studies of clinkers fired at different temperatures and holding times proved that as a result of the interaction of the raw materials of the mixture in the material synthesizes a mixture of hydraulically active calcium mono‐ and di‐aluminate and refractory cobalt spinel, which provides the resulting complex high strength, accelerated curing time, fire resistance. The absence of phases corresponding to molybdenum compounds is explained by the fact that they are part of hydraulically active aluminates as limited solid solutions, deforming the crystal lattice and increasing hydraulic activity. Thus, it was found that the high strength of cement is due to the presence of calcium hydroaluminates such as C2AH8, aluminum hydroxide, as well as unhydrated grains of calcium aluminates, which will contribute to further long‐term strength. It is this coexistence of phases in both the crystalline and colloidal states provide high strength cement stone.

2D Nano-Channeled Molybdenum Compounds for Accelerating Interfacial Polysulfides Catalysis in Li-S Battery.

The shuttle effect, which causes the loss of active sulfur, passivation of lithium anode, and leads to severe capacity attenuation, is currently the main bottleneck for lithium-sulfur batteries. Recent studies have disclosed that molybdenum compounds possess exceptional advantages as a polar substrate to immobilize and catalyze lithium polysulfide such as high conductivity and strong sulfiphilicity. However, these materials show incomplete contact with sulfur/polysulfides, which causes uneven redox conversion of sulfur and results in poor rate performance. Herein, a new type of 2D nano-channeled molybdenum compounds (2D-MoNx) via the 2D organic-polyoxometalate superstructure for accelerating interfacial polysulfide catalysis toward high-performance lithium-sulfurbatteries is reported. The 2D-MoNx shows well-interlinked nano-channels, which increase the reactive interface and contact surface with polysulfides. Therefore, the battery equipped with 2D-MoNx displays a high discharge capacity of 912.7 mAh g-1 at 1 C and the highest capacity retention of 523.7 mAh g-1 after 300 cycles. Even at the rate of 2 C, the capacity retention can be maintained at 526.6 mAh g-1 after 300 cycles. This innovative nano-channel and interfacial design of 2D-MoNx provides new nanostructures to optimize the sulfur redox chemistry and eliminate the shuttle effect of polysulfides.

Selective Dehydrogenation of Formic Acid Catalyzed by Air‐Stable Cuboidal PN Molybdenum Sulfide Clusters

AbstractFormic acid is considered as a promising hydrogen storage material in the context of a green hydrogen economy. In this work, we present a series of aminophosphino and imidazolylamino Mo3S4 cuboidal clusters which are active and selective for formic acid dehydrogenation (FAD). Best results are obtained with the new [Mo3S4Cl3(ediprp)3](BPh4) (4(BPh4)) (ediprp=(2‐(diisopropylphosphino)ethylamine)) cluster, which is prepared through a simple ligand exchange process from the Mo3S4Cl4(PPh3)3(H2O)2 precursor. Under the conditions investigated, complex 4+ showed significantly improved performance (TOF=4048 h−1 and 3743 h−1 at 120 °C in propylene carbonate using N,N‐dimethyloctylamine as base after 10 min and 15 min, respectively) compared to the other reported molybdenum compounds. Mechanistic investigations based on stoichiometric and catalytic experiments show that cluster 4+ reacts with formic acid in the presence of a base to form formate substituted species [Mo3S4Cl3‐x(OCOH)x(ediprp)3]+ (x=1–3) from which the catalytic cycle starts. Subsequently, formate decarboxylation of the partially substituted [Mo3S4Cl3‐x(OCOH)x(ediprp)3]+ (x=1, 2, 3) catalyst through a β‐hydride transfer to the metal generates the trinuclear Mo3S4 cluster hydride. Dehydrogenation takes place through protonation by HCOOH to form Mo−H⋅⋅⋅HCOOH dihydrogen adducts, with regeneration of the Mo3S4 formate cluster. This proposal has been validated by DFT calculations.

Crystal structures and luminescence properties of Li6 MN4:Ce3+ (M = Mo, W)

Abstract The compounds Li6MoN4 and Li6WN4 were prepared from the reactants M (M = Mo, W) and Li3N in a radiofrequency furnace at 1000 °C. The lithonitridometallates crystallize in the tetragonal system with the lattice parameters: a = 6.6844(1), c = 4.9294(1) Å for Li6WN4 based on single-crystal X-ray diffraction data and a = 6.6611(3), c = 4.9338(3) Å for Li6MoN4 taken from powder X-ray diffraction data. Colorless to slightly reddish single-crystals of the tungsten compound were isolated and the crystal structure was refined in the space group P42/nmc (no. 137) with Z = 2 and the powder X-ray data of the molybdenum compound were analyzed by a Rietveld refinement. Both structures belong to the Li6[ZnO4] type published by Hoppe et al. in 1987 (Untenecker H., Hoppe R. Z. Anorg. Allg. Chem. 1987, 551, 147–150) and could be doped with Ce3+ for the first time. The investigated compounds show a reddish color impression upon UV to blue irradiation and exhibit a broad emission band with a maximum at λ max = 693 nm (fwhm 97 nm) for Li6MoN4 and at λ max = 653 nm (fwhm 133 nm) for Li6WN4.

Cyclopentadienyl Molybdenum(II) Compounds Bearing Ether and Thioether Functions in the Side Chain: Synthesis, Characterization, and Cytotoxic/Cytostatic Studies.

A series of molybdenum(II) compounds [(η5-Cp')Mo(CO)2(L2)][BF4] (Cp' = C5H4(CH2)2SPh, C9H6(CH2)2OMe, L2 = N,N-chelating ligand) have been synthesized and characterized by spectroscopic and analytical methods including X-ray crystallography. The in vitro assay on human leukemia cells MOLT-4 has shown that the substitution in the π-ligand in combination with suitable N,N-chelating ligand can lead to species with cytotoxicity considerably higher than reported to cisplatin. Unusually high activity was observed for compounds bearing phenanthroline ligands [{η5-C9H6(CH2)2OMe}Mo(CO)2(3,4,7,8-Me4phen)][BF4] (IC50 = 0.7 ± 0.3 μM) and [{η5-C9H6(CH2)2OMe}Mo(CO)2(4,7-Ph2phen)][BF4] (IC50 values 0.8 ± 0.4 μM).

Microstructure Characteristics and Tribological Properties of Gradient Cu-MoS2 Self-Lubricating Coating Fabricated by Selective Laser Melting of Ink-Printed Metal Nanoparticles

Abstract Self-lubricating coating has been used in industrial applications with severe conditions, such as high temperatures, vacuum, radiation, etc. In this paper, a selective laser melting of ink-printed metal nanoparticles (SLM-IP metal NPs) rapid manufacturing method was applied to fabricate Cu-MoS2 self-lubricating coating. A tailored ink consisting of metal NPs, reductant, and dispersant was deposited on a stainless steel substrate, forming the laminated gradient Cu-MoS2 coating. The microstructure and mechanical properties of the composite coating were characterized. The friction and wear behavior were experimentally investigated by dry sliding wear test at room and higher temperatures (>200 °C). The results indicated that the upper copper sulfur molybdenum compound layer with homogeneously distributed MoS2 provided a significant friction reduction and wear resistance. The SLM-IP Cu-MoS2 coatings showed a reduced friction coefficient by 54% compared to the pure Cu coating. The transitional Cu layer mitigated the abrupt changes in physical properties and enhanced the bonding strength between the coating and substrate. Especially, under the test condition of 200 °C, the Cu-40 vol% MoS2 coating also presented an excellent resistance to oxidation and had a lower friction coefficient of 0.24. This research provides the feasibility of fabricating self-lubricating coatings by the SLM-IP metal NPs method for surface engineering technologies.

Molybdenum(VI) complexes with ligands derived from 5-(2-pyridyl)-2H-tetrazole as catalysts for the epoxidation of olefins

The development of effective catalytic epoxidation processes that are an alternative to stoichiometric non-selective oxidation routes is important to meet environmental sustainability goals. In this work, molybdenum(VI) compounds bearing 5-(2-pyridyl)−2H-tetrazole derivatives as organic components, namely the ionic and neutral mononuclear complexes (H2ptz)[MoO2Cl2(ptz)] (1) and [MoO2Cl2(tBu-ptz)] (2), and the new Lindqvist-type polyoxometalate (POM) [tBu-Hptz]2[Mo6O19] (3), where Hptz = 5-(2-pyridyl)tetrazole and tBu-ptz = 2-tert-butyl-5-(2-pyridyl)−2H-tetrazole, were studied as epoxidation catalysts using readily available and relatively ecofriendly hydroperoxide oxidants, namely hydrogen peroxide and tert-butyl hydroperoxide (TBHP). The prepared catalysts were very active. For example, 100% cis-cyclooctene conversion and 100% epoxide selectivity were reached at 1 h for 1 and 3, and 10 min for 2 (with TBHP). Catalytic and characterization studies indicated that the mononuclear complexes suffered chemical transformations under the reaction conditions, whereas 3 was structurally stable. This POM acted as a homogeneous catalyst and could be recycled by employing an ionic liquid solvent. The POM can be synthesized from 2 under different conditions, including those used in the catalytic process. Moreover, 3 was an effective epoxidation catalyst for a biobased substrate scope that included fatty acid methyl esters and the terpene dl-limonene.

Combined Adsorptive and Ultrasonic Treatment to Remove Metals from Fuel Oil

The study investigated removal of metals (Ni, V, Cr, Fe, Ti, and Mo) from fuel oil using ultrasonic treatment (UST) and adsorbents such as carbon black, carbon nanotubes, aluminum oxyhydroxide (AlO(OH)), iron oxyhydroxide (FeO(OH)), and titanium dioxide (TiO2). Combined adsorption/UST provided a somewhat higher demetallization degree than the use of adsorbents alone. Compounds of iron, chromium, and molybdenum, which presumably complex with petroleum feedstock components due to intermolecular bonding, were removed almost completely (95%). The removal of titanium compounds reached 60%. For these metals, no correlation between the removal degree and the physicochemical properties of the adsorbents was found. For vanadium and nickel, the highest removal degrees (37 and 23%, respectively) were achieved when an iron oxyhydroxide adsorbent was used in combination with UST. This can likely be associated with the superiority of the FeO(OH) adsorbent in negative surface charge and specific surface area compared to the other samples.