Spent Fluid Catalytic Cracking Catalyst Research Articles

Green biofuel production via cracking process of waste cooking oil using spent fluid catalytic cracking (SFCC) catalyst

Waste Cooking Oil (WCO) can be a alternative for petroleum-based fuel. In this work, green biofuel was produced via cracking process of high acid value (AV) waste cooking oils (WCOs) over spent fluid catalytic cracking (SFCC) catalyst collected from Binh Son Refireny. The influences of temperature (450 – 520°C), catalyst-to-WCO ratio (1.5 – 3.5), and acid value (6 - 22 mgKOH/g) have been examined. At 520°C, WCOs can be converted to liquid fuels with the near zero AV (AV < 0.5 mgKOH/g) which is independent of AV of WCOs. In all cases, the total yield of profitable products, gasoline-diesel-LPG, reaches 85 wt%, with only 5 - 7 wt% of coke yield. This study demonstrated the simultaneous utilization of multiple hazardous substances, SFCC catalyst and WCOs, as low-cost raw materials for biofuel production.

Catalytic pyrolysis of chicken manure over various catalysts

In this study, non-catalytic and catalytic pyrolysis of chicken manure (CM) were investigated to understand the pyrolysis kinetics and product distribution of CM by thermogravimetric analysis (TGA) and pyrolyzer-gas chromatography/mass spectrometry (Py-GC/MS). TGA and the apparent activation energy changes, calculated using the Ozawa method, indicated that the decomposition of CM was comprised of four reaction stages. The 1st decomposition of CM was likely the decomposition of carbohydrates and lipids, followed by the 2nd decomposition of lignin at high temperatures. The 3rd decomposition was likely involving the decomposition of proteins. At the final stage, metal carbonates in the ash of CM were likely decomposed. Py-GC/MS analysis indicated a decrease in oxygenates, such as furfural, phenol, and fatty acid, after applying acid catalysts. Among the various acid catalysts, HZSM-5(Silica/Alumina = 30), having the strongest acid sites, showed the highest efficiency for the production of aromatic hydrocarbons, followed by HBeta(Silica/Alumina = 25), HY(Silica/Alumina = 30), natural zeolite, spent fluid catalytic cracking catalyst (FCC), and bentonite. Although bentonite and spent FCC were ineffective, natural zeolite showed a catalytic effect on converting oxygenates to aromatic hydrocarbons. On the other hand, the content of a high molecular weight nitrile, hexadecanenitrile, was also increased. Commercial zeolites, HY(Silica/Alumina = 30), HBeta(Silica/Alumina = 25), and HZSM-5(Silica/Alumina = 30), led to higher aromatic formation efficiencies with less hexadecanenitrile formation than other catalysts. These efficiencies were increased significantly by varying the catalyst to CM ratio from 1/1 to 5/1, with a noticeable decrease in hexadecanenitrile.

Kinetics of Ni, V and Fe Leaching from a Spent Catalyst in Microwave-Assisted Acid Activation Process.

Ni, V and Fe are the main contaminant metals that lead to the deactivation of the spent fluid catalytic cracking (SFCC) catalyst. In this work, the properties and distribution of Ni, V and Fe in the SFCC catalyst are investigated by employing EPMA-EDX, SEM and XPS techniques. The kinetics of Ni, V, Fe and Al leaching in organic and inorganic acids are studied under microwave heating. The EPMA-EDX results show that Fe and Ni mainly accumulate near the particle surface, while V eventually distributes throughout the catalyst particle. The XPS result suggests that the phase speciations of Ni in the SFCC catalyst are Ni, Ni2SiO4 and NiAl2O4, while Fe is present in a mixture of Fe3O4, Fe2O3 and Fe2SiO4. V is in the forms of V2O5 and VO2. Compared with oxalic acid, sulfuric acid has a better removal effect of contaminant metals, especially for Ni. The leaching kinetics results indicate that using either sulfuric acid or oxalic acid, the apparent activation energy of V is obviously lower than that of Fe and Ni, and the priority of the three contaminant metals in the removal effect is V > Fe > Ni. In addition, the leaching kinetics of contaminant metals in the microwave-assisted acid activation process are controlled by the surface chemical reaction control model.

Extraction of Lanthanum Oxide from Different Spent Fluid Catalytic Cracking Catalysts by Nitric Acid Leaching and Cyanex 923 Solvent Extraction Methods

A laboratory-scale procedure was developed to obtain lanthanum oxide from spent fluid catalytic cracking catalyst, commonly used in the heavy crude oil cracking process. Two different solids, consisting mainly of silica, alumina, and a certain amount of rare earth elements, were leached under several conditions to recover the rare earths. Nitric acid leaching lead to the highest recovery of lanthanum, reaching a recovery percentage greater than 95% when a 1.5 M concentration was used. Subsequently, liquid phases were subjected to a liquid–liquid extraction process using Cyanex 923 diluted in Solvesso 100, and the lanthanum was quantitatively extracted. Lanthanum was also quantitatively stripped using oxalic acid to obtain the corresponding lanthanum oxalates, as revealed by X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential thermal analysis (DTA), and Fourier transform infrared (FTIR) techniques. After thermal treatment at 1200 °C for 2 h, these solids yielded lanthanum oxide.

Structure and Properties of Phosphate-Based Geopolymer Synthesized with the Spent Fluid Catalytic-Cracking (SFCC) Catalyst.

As a common industrial by-product, the spend fluid catalytic-cracking (SFCC) catalyst was used to prepare phosphate-based geopolymer for the first time. The structure and property of geopolymer with phosphoric acid concentration ranging from 6 to 14 mol/L was characterized by compressive strength measurements, X-ray powder diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and 27Al and 29Si nuclear magnetic resonance (NMR). A stable binder was formed with the compressive strength in the range of 9.8 to 30.2 MPa when the acid concentration was between 6 and 12 mol/L. The higher concentration of acid can promote the dissolution of raw materials and formation of geopolymer gels. The coordination of silicon and aluminum in geopolymer gel synthesized with the SFCC catalyst and metakaolin is similar. Compared with the geopolymer with metakaolin, which forms more Si-O-Al bonds, in the networks of geopolymer with the SFCC catalyst, more Si(Al)-O-P bonds were formed. These results indicate that the SFCC catalyst can be an excellent raw material for the synthesis of phosphate-based geopolymer.

Synthesis and Hydration Of Ye’Elimite Containing Cement (Ycc) Produced with Spent Fluid Catalytic Cracking Catalyst

Synthesis and Hydration Of Ye’Elimite Containing Cement (Ycc) Produced with Spent Fluid Catalytic Cracking Catalyst

Immobilization of vanadium and nickel in spent fluid catalytic cracking (SFCC) catalysts-based geopolymer

In recent years, the use of spent fluid catalytic cracking (SFCC) catalysts to prepare geopolymers has received attention from academic and industrial circles. However, SFCC catalysts have been classified as hazardous waste in China due to their vanadium and nickel content. In this paper, the immobilization rates of vanadium and nickel in geopolymers prepared with SFCC catalysts were studied through a toxicity characteristic leaching procedure (TCLP). The immobilization mechanism of nickel and vanadium during geopolymerization was investigated by XPS, SEM, XRD, and compressive strength measurements. The nickel and vanadium TCLP concentrations of the SFCC catalyst-based geopolymer are 0.032 mg/L and 10.63 mg/L, respectively. Nickel in the SFCC catalyst is partly dissolved and adsorbed by the negatively charged tetrahedral aluminum in the geopolymer. However, because vanadates formed under alkaline conditions are negatively charged and readily soluble in water, vanadium in the SFCC catalyst is neither immobilized by the charge balance nor effectively immobilized by physical encapsulation. Therefore, the use of SFCC catalysts to prepare geopolymers will lead to vanadium contamination in the environment. In order to clarify the maximum vanadium content in SFCC catalysts for preparing geopolymers without environmental risk, SFCC catalysts with different vanadium levels were prepared by leaching. It was concluded that when the vanadium content in the SFCC catalyst is lower than 1861.4 mg/kg, the vanadium content in the leachate is lower than 2 mg/L and the geopolymer can be considered a non-hazardous material.

A novel method for extraction of platinum from spent automotive catalyst: utilization of spent fluid catalytic cracking catalyst as flux

ABSTRACT A novel method of smelting of mixture of spent automotive catalyst (SAC) and spent fluid catalytic cracking catalyst (SFCC) to recover platinum and prepare glass slag was investigated. Compared to other metals collection processes for single hazardous waste solid, this method reduced the amount of fluxing materials addition and increased the processing types of hazardous solid waste simultaneously. The optimum SFCC addition, iron collector addition, Na2B2O4•10H2O addition, CaO/SiO2 mass ratio, temperature, and holding time for platinum recovery were 20, 11, 16 wt%, 0.6, 1550–1600°C, and 60 min, respectively. In this proposed combined process, more than 98% of platinum is efficiently recovered from SAC. Meanwhile, the concentration of platinum in glass slag was less than 7 g/t. The leaching characteristics of heavy metals in slag confirmed the obtained glass slag is a non-hazardous slag due to the low leaching rate of heavy metal ions. This article proposed an effective and environmentally friendly method for the recovery of platinum from SAC via a combined smelting process.

A "Wastes-Treat-Wastes" Technology: Role and Potential of Spent Fluid Catalytic Cracking Catalysts Assisted Pyrolysis of Discarded Car Tires.

Spent fluid catalytic cracking catalysts (FCC catalysts) produced by the petrochemical industry are considered to be environmentally hazardous waste, and precious metals and heavy metals deposited on the surface make them difficult to treat. Even so, these catalysts retain some of their activity. The pyrolysis of waste tires is considered to be one of the most effective ways to solve the fossil fuel resource crisis, and this study attempts to catalyze the pyrolysis of waste tires using spent catalysts to increase the value of both types of waste. FCC catalysts reduced the activation energy (E) of waste tire pyrolysis. When the catalyst dosage was 30 wt.%, the E of tread rubber decreased from 238.87 kJ/mol to 181.24 kJ/mol, which was a 19.94% reduction. The E of the inner liner decreased from 288.03 kJ/mol to 209.12 kJ/mol, a 27.4% reduction. The spent catalyst was more effective in reducing the E and solid yield of the inner liner made of synthetic rubber. It should be emphasized that an appropriate increase in the heating rate can fully exert the selectivity of the catalyst. The catalyst could also be effectively used twice, and the optimum ratio of catalyst/waste tires was about 1/4.5. Compared with specially prepared catalysts, it is more cost-effective to use such wastes as a catalyst for waste tire pyrolysis.

The effect of nano SiO2 and spent fluid catalytic cracking catalyst on cement hydration and physical mechanical properties

This paper describes research on the synergistic effect of nano–SiO2 (NS) and spent fluid catalytic cracking catalyst (FCCCw) in cement pastes’ pozzolanicity. Binary and ternary blended cement pastes containing 0.02% of NS and 5–20% of FCCCw were investigated. Hydration at early age followed using semi-adiabatic calorimetry. The macroscale properties were assessed by measuring density, ultrasonic pulse velocity and compressive strength. The microstructures were analysed by scanning electron microscopy, X-ray diffraction and thermogravimetric analysis. The results are consistent among the different techniques and materials’ levels and show that a small NS content promotes a marked synergistic enhancement of the pozzolanic reaction.

Conversion of HDPE into Value Products by Fast Pyrolysis Using FCC Spent Catalysts in a Fountain Confined Conical Spouted Bed Reactor.

Continuous catalytic cracking of polyethylene over a spent fluid catalytic cracking (FCC) catalyst was studied in a conical spouted bed reactor (CSBR) with fountain confiner and draft tube. The effect of temperature (475–600 °C) and space‐time (7–45 gcat min gHDPE −1) on product distribution was analyzed. The CSBR allows operating with continuous plastic feed without defluidization problems and is especially suitable for catalytic pyrolysis with high catalyst efficiency. Thus, high catalyst activity was observed, with waxes yield being negligible above 550 °C. The main product fraction obtained in the catalytic cracking was made up of C5−C11 hydrocarbons, with olefins being the main components. However, its yield decreased as temperature and residence time were increased, which was due to reactions involving cracking, hydrogen transfer, cyclization, and aromatization, leading to light hydrocarbons, paraffins, and aromatics. The proposed strategy is of great environmental relevance, as plastics are recycled using an industrial waste (spent FCC catalyst).

Albemarle catalysts reports 1Q 2021 sales growth

The speciation of Ni in spent Fluid Catalytic Cracking catalysts is studied. Carefully performed XRD analyses with NiO/SiO2 samples used as calibration standards, demonstrate that the presence of NiO as a separate phase is reliably detected also for NiO concentration close to 0.1 wt% (1000 ppmw). Actually, both on real spent FCC catalysts (ECAT's) and on artificially contaminated industrial FCC catalysts, NiO is not detectable as a separate phase, even after contamination of the order of 15,000 ppmw of Ni. SEM–EDS experiments provide evidence of a largely preferential location of Ni on alumina particles present in the FCC catalyst mixture, thus acting as “nickel traps”. XRD, UV–vis and TPR data confirm that Ni deposits on alumina particles forming a hardly reducible surface and subsurface layer, giving rise to a solid whose composition is NixAl2O3+x with x << 0.25. As a result of this, the formation of extended Ni metal particles in the raiser reactor is avoided, being their unwanted dehydrogenation activity essentially eliminated. The absence of bulk NiO in the spent FCC catalysts (at least when Ni content is in the range 2000–10,000 ppmw) allows the classification of this material as a non-hazardous waste.

Utilization of Spent FCC Catalyst as Fine Aggregate in Non-sintered Brick: Alkali Activation and Environmental Risk Assessment.

This study focuses on the recycling of a spent fluid catalytic cracking (FCC) catalyst to produce catalyst-based non-sintered bricks (CN-bricks) for the recovery of its aluminosilicate components and the solidification of heavy metals. The effects of the content of cement (10–20%), the proportion of FCC (10–40%), and the type of an activator (NaOH/Na2SiO3/Na2SO4) on the performance of a CN-brick were investigated in terms of the mechanical strength and leaching behavior. The results show that an optimal binder system of 20% cement + Na2SO4 could promote the compressive strength up to 42.3 MPa; the proportion of an optimal spent FCC catalyst of 20% could achieve the lowest porosity and water absorption. The microscopic mechanism of a cementitious process was analyzed by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM), proving that C-S-H and ettringite (AFt) are the two main hydration products of a CN-brick. Na2SO4 is superior to NaOH or Na2SiO3 as an activator since Na2SO4 takes advantage of the aluminum-rich property of a spent FCC catalyst and specifically promote the formation of a needle-like AFt. Quantitative environmental risk assessment for the utilization of a CN-brick on roads was carried out based on the leaching test of a toxicity characteristic leaching procedure (TCLP), NEN 7371 maximum availability test, and the hazard Index (HI) identification, and a final HI 0.0045 (<1.0) indicates an acceptable risk for environment and nearby residents as CN-bricks are utilized on roads for 30 years.

Leaching of metals from spent fluid catalytic cracking catalyst using Acidothiobacillus ferrooxidans and comparing its leaching efficiency with organic and inorganic acids

Bioleaching is an eco-friendly alternative for the extraction of metals from the spent fluid catalytic cracking catalyst (SFCCC). Acidothiobacillus ferrooxidans (A. ferrooxidans) are the most widely reported bacteria in leaching but remained unexplored for SFCCC till date. The present study proposes a cleaner, environmentally friendly process to leach metals from SFCCC by A. ferrooxidans. Batch bioleaching of metals was carried out with unadapted and adapted A. ferrooxidans. Experiments were performed by varying the pulp density (PD) (1–20%) at two different initial Fe(II) concentrations i.e. 2 g/L [M2Fe(II)] and 8.84 g/L [M8.84Fe(II)]. The results showed that adapted A. ferrooxidans leached out metals better than unadapted ones. Even though the loss of Iron to Jarosite formation was higher in M8.84Fe(II) than in M2Fe(II), leaching remained higher in M8.84Fe(II). Jarosite formation was minimized by maintaining the pH of the medium to 2 ± 0.1. Maximum leaching efficiency was observed at 1% PD. At this concentration. A. ferrooxidans growth was triggered which increased the production of Fe(III), thereby increasing leaching efficiency. Increase in PD led to a decrease in metal leaching efficiency. The maximum leaching observed by A. ferrooxidans is Al (35%), Ti (14%), Ni (27%) and V (56.5%). The amount of Al leached (70 mg/gm of SFCCC) suggests SFCCC be the potential secondary source of Al compared to popular secondary sources such as red mud and other spent catalysts. Al and V were better leached by A. ferrooxidans while organic acids were more suitable to extract Ti and Ni from SFCCC.

Research on Hazardous Waste Removal Management: Identification of the Hazardous Characteristics of Fluid Catalytic Cracking Spent Catalysts.

Fluid catalytic cracking (FCC) spent catalysts are the most common catalysts produced by the petroleum refining industry in China. The National Hazardous Waste List (2016 edition) lists FCC spent catalysts as hazardous waste, but this listing is very controversial in the petroleum refining industry. This study collects samples of waste catalysts from seven domestic catalytic cracking units without antimony-based passivation agents and identifies their hazardous characteristics. FCC spent catalysts do not have the characteristics of flammability, corrosiveness, reactivity, or infectivity. Based on our analysis of the components and production process of the FCC spent catalysts, we focused on the hazardous characteristic of toxicity. Our results show that the leaching toxicity of the heavy metal pollutants nickel, copper, lead, and zinc in the FCC spent catalyst samples did not exceed the hazardous waste identification standards. Assuming that the standards for antimony and vanadium leachate are 100 times higher than that of the surface water and groundwater environmental quality standards, the leaching concentration of antimony and vanadium in the FCC spent catalyst of the G set of installations exceeds the standard, which may affect the environmental quality of surface water or groundwater. The quantities of toxic substances in all spent FCC catalysts, except those from G2, does not exceed the standard. The acute toxicity of FCC spent catalysts in all installations does not exceed the standard. Therefore, we exclude “waste catalysts from catalytic cracking units without antimony-based passivating agent passivation nickel agent” from the “National Hazardous Waste List.”

Coupling effect of steel slag in preparation of calcium-containing geopolymers with spent fluid catalytic cracking (FCC) catalyst

Spent FCC catalyst coupling with steel slag has been used to synthesize a new calcium-containing geopolymer binding material with excellent performance. The effect of the composition of the raw materials on the performance of the obtained samples has been investigated systematically. The results indicate that the compressive strength of the prepared geopolymers was increased with the addition of steel slag. This is due to the calcium-containing components in the steel slag, which possess higher reactivity compared to the pure chemical reagent in the alkaline activation environment, which is beneficial for the generation of N(C)-A-S-H amorphous gel (where N = Na2O, A = Al2O3, C = CaO, S = SiO2, and H = H2O) in the obtained samples. Meanwhile, the other components of steel slag would embed in the cementitious material as skeleton materials, which are conducive for the improvement of the compressive strength performance. In addition, the role steel slag plays in the geopolymerization reaction has been studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectrometry (FT-IR). Results indicated that the catalyst-derived geopolymer gel (N-A-S-H) coexisted with slag activated gel (C-S-H/C-A-S-H) in the binding matrix, which are the main phases in the geopolymer, and the development of better compressive strength is attributed to the formation of Ca-rich gel phases. These results highlight the feasibility of using spent FCC catalyst and steel slag as raw materials for the production of geopolymer binding material with enhanced compressive strength.

Thermal and catalytic pyrolysis of waste polypropylene plastic using spent FCC catalyst

Waste polypropylene plastic (WPP) is an enormous volume of plastics in the landfill in Nigeria. It causes serious environmental problems, such as reduced landfill space and pollution. We made WPP plastic undergo pyrolysis using a batch reactor subjected to temperatures variation of 300 °C, 350 °C, 375 °C, 400 °C, and the spent fluid catalytic cracking (FCC) catalyst used were 5, 7.5, and 10 wt% catalyst. We heated the reactor at a rate of 15 °C/min. until it reaches the pyrolysis temperature of 400 °C at atmospheric pressure. We investigated the influence of the FCC catalyst, reaction temperatures, and catalyst to plastic ratio. We characterized the pyrolysis liquid oil using density, pour point, API gravity, flash point, viscosity, calorific value, carbon residue, ATSM distillation, and GC–MS. The thermal pyrolysis produced maximum liquid oil (83.3 wt%) with gases (13.2 wt%), and char (3.0 wt%), while the catalytic pyrolysis using 0.1 catalyst to plastic ratio decreased the liquid oil yield (77.6 wt%), and char (2.7 wt%), with an increase in gases (19.7 wt%). The GC–MS results of the catalytic pyrolysis of liquid oil showed that the liquid fractions comprised a wide range of hydrocarbon, mainly distributed within C4 to > C17. The paraffin, olefins, naphthalene, and aromatics yield were 30.83%, 44.6%. 19.44%, and 5.13%, respectively. The liquid oil’s fuel properties were like that of gasoline and diesel. • The liquid oil yield from thermal (83.3 wt%) and that of catalytic (77.6 wt%) pyrolysis. • The liquid fractions comprises a wide range of hydrocarbons from C 4 -C 17 . • The liquid oils fuel properties were comparable to that of gasoline and diesel.

Geopolymer synthesized from spent fluid catalytic cracking catalyst and its heavy metal immobilization behavior

Porous geopolymers (GP) are energy saving, environment-friendly and simple in preparation, which has attracted increasing attention from both academia and industry. In this paper, geopolymer with excellent immobilization capability of heavy metals was prepared by chemical forming method. The spent fluid catalytic cracking (sFCC) catalyst, a hazardous solid waste in China, was exploited as aluminosilicate precursor. The influences of particle size of sFCC catalyst, type of activator agent solutions, mass ratios of SiO2/Na2O and (SiO2 + Na2O)/sFCC catalyst on the compressive strength of GP and the leaching toxicity of Ni were investigated in detail. Under the optimum conditions, the leaching toxicity of Ni is reduced to below 0.01 ppm, much lower than the national standard 5 ppm. The as-obtained GP was also examined by SEM, XRD and FTIR with the aim to understand the synthesis and immobilization mechanism using the sFCC catalyst as the raw material. The results show a new aluminosilicate zoisite phase with three-dimensional network structure forms. Ni element enters the grid of GP, involved in the formation of three-dimensional network structure. Besides, partial Ni element replaces the position of alkaline metal and chemical bonds AlO4.

Spent fluid catalytic cracking (FCC) catalyst enhances pyrolysis of refinery waste activated sludge

Catalytic pyrolysis is an effective innocuity, volume reduction and resource recovery technology for petroleum refinery waste activated sludge (rWAS). However, the high cost of catalysts hinders its application. In the present study, the spent fluid catalytic cracking catalyst (sFCCc) was reused to catalytically pyrolyze rWAS for the first time. The pyrolytic kinetics, yields and characteristics of pyrolytic products were investigated. sFCCc reduced the low-temperature (139–390 °C) and high-temperature (390–540 °C) average activation energy by 12.9% and 6.6% compared to rWAS alone. sFCCc and metallic oxides in rWAS jointly catalyzed the decomposition of rWAS and primary vapor via a series of thermochemical reactions. sFCCc promoted the conversion of rWAS into bio-oil and non-condensable gases. The lowest yield of biochar was 40.6 wt % and the highest content of H2 in non-condensable gases was up to 38.4 vol %. sFCCc significantly improved the quality of bio-oil. The content of saturated hydrocarbons increased from 37.3 wt % to 45.7 wt % and H/C molar ratios increased from 1.4 to 1.6. The O mobility from rWAS to bio-oil decreased from 22.1 wt % to 14.9 wt %. The pyrolytic residue presented a low environmental risk and showed a catalytic potential in ozonation treatment of refractory refinery wastewater. This study provides a new “wastes-treat-wastes” method for petroleum refinery waste management with the advantages of value-added energy recovery and resources reuse.

Stabilization/Solidification of Toxic Elements in Cement Pastes Containing a Spent FCC Catalyst

Huge amounts of spent fluid catalytic cracking (FCC) catalysts, also called Ecat, are produced worldwide, every year. Alternatives to the traditional landfill disposal are imperative to reduce the environmental contamination and the production of hazardous solid wastes. The leaching of iron, nickel, antimony, and vanadium from Ecat was investigated using the toxicity characteristic leaching procedure (TCLP) to assess the risk of contamination of the aquatic environment. The concentrations of these elements in the leachate of a cement paste containing 15% Ecat were much reduced as compared to those leached from the Ecat sample and were below the limits established in the water quality criteria of the United States Environmental Protection Agency (USEPA 2004). The solidification/stabilization (S/S) of Fe, Ni, V, and Sb in the cement paste containing Ecat was influenced by the chemical properties and stability of the products formed with cement-hydrated phases and by the erosion of the cement paste exposed to the leaching environments. The S/S mechanisms were less effective in seawater and this was related to reactions of cement-hydrated phases with the salts usually present in seawater. The results indicated that the solidification/stabilization (S/S) process was efficient enough to prevent the excessive leaching of these toxic elements.