Hydrothermal Precipitation Research Articles

Hydrothermal precipitation of copper from leaching solutions of metallurgical dusts

In this work, we aim to establish the main regularities of hydrothermal precipitation of copper from the previously unstudied sulfuric-nitric acid and sulfate solutions of atmospheric and autoclave processing of metallurgical dusts. Pyrite was used as a sulfidizer. The elemental composition of the products was determined by X-ray fluorescence, inductively coupled plasma atomic emission spectrometry, and atomic absorption analysis. It was found that copper precipitation by the proposed technology enables its recovery at a level of more than 95%. For sulfate solutions with a high arsenic concentration, a two-stage scheme of oxidation-hydrothermal treatment with the following parameters was proposed: temperature 180°С, duration 2 h, oxygen consumption 0.026 dm3/g pyrite (for the 1st stage), and 200°С and 2 h (for the 2nd stage). Extraction in the cake amounted to 95.4% of copper (in the form of Cu2S) and 91.4% of arsenic (in the form of FeAsO4), which allowed further separation of these metals by flotation. An autoclave treatment of a Cu–Zn–Fe–As–NO3 solution in the presence of pyrite at 180–220°С produced the activation energy values (kJ/mol) corresponding to the kinetic regime calculated by the two methods: 64.6 by the conventional method and 60.5 by the shrinking core model. The kinetic parameters of CuSO4–H2SO4–FeS2–H2O and CuNO3–H2SO4–FeS2–H2O systems were also determined. Flotation enrichment of copper autoclave precipitation cake was shown to result in a high degree of Cu and As separation, with the recovery amounting to Cu ˃ 95% and As ˂ 5%. Precious metals contained in pyrite are transferred to a flotation concentrate by 92.7% (Au) and 96.5% (Ag). The composition of the resulting flotation concentrate comprised (%): 12 Cu; 37 Fe; 38 S; 13 other elements. It is shown that, in order to obtain a product with the required content of copper, flotation concentrate should be separated into pyrite and copper concentrates followed by an additional flotation of primary copper concentrate in an alkaline medium in the presence of lime. Hence, our study has established the main regularities of hydrothermal precipitation of copper from the sulfuric-nitric acid and sulfate solutions of atmospheric and autoclave processing of metallurgical dusts.

Low-temperature fabrication of zirconia transparent ceramics via hydrothermal nanopowder

Highly sinterable nanopowder of 8 mol% yttria-stabilized cubic zirconia (8YSZ) was synthesized via a hydrothermal homogeneous precipitation (HHP) method. The nanopowder with an average particle size of 26 nm, exhibits good dispersibility, narrow particle size distribution and high purity, making it ideal raw material for preparing transparent ceramics. Utilizing spark plasma sintering (SPS) under mild conditions (1200–1350 °C, 80 MPa, 10 min) in contrast to hot isostatic pressing (HIP), cubic zirconia ceramics with favorable optical and mechanical properties were produced. The sample sintered at 1250 °C achieved the highest transmittance of 74 %@850 nm, significantly surpassing the performance of samples prepared from two other commercial 8YSZ powders. Furthermore, the specimen sintered at 1200 °C with a dense fine microstructure (relative density: 99.51 %, grain size: 460 nm), demonstrated the highest hardness and fracture toughness, reaching 15.72 GPa and 1.28 MPa m1/2, respectively.

Experimental study and DFT+U calculations on the impact of Rare-Earth ion (La3+, Sm3+, Y3+, Yb3+) doped CeO2 Core-Shell abrasives on polishing performance

A series of carbon spheres coated with Rare-Earth ion-doped (La3+, Sm3+, Y3+, Yb3+) CeO2 (CS@CeO2) were synthesized using eco-friendly hydrothermal and chemical precipitation methods. The structural characteristics of the abrasives were thoroughly analyzed using XRD, SEM, TEM, and FT-IR techniques. A detailed analysis of Ce3+ and Vo concentrations on the CeO2 layer surface was conducted using XPS and Raman spectroscopy. The analysis results indicated that CS@Ce0.9Y0.1O2 abrasives exhibited the highest Ce3+ (46.23 %) and Vo (25.39 %) concentrations. Additionally, the polishing performance of the abrasives was evaluated using atomic force microscopy (AFM). The CS@Ce0.9Y0.1O2 abrasive exhibited superior polishing performance, achieving the lowest surface roughness (Ra = 0.26 nm) compared to commercial abrasives (Ra = 0.77 nm), reducing Ra by 66.23 %. Moreover, density functional theory with the Hubbard U method (DFT+U) was used to systematically investigate the oxygen vacancy formation energy, structural stability, and electronic properties of CeO2 doped with Rare-Earth ions. These findings demonstrate that doping with Rare-Earth ions possessing ionic radii close to that of Ce4+ effectively enhances the concentration of oxygen vacancies and Ce3+ ions, which is crucial for improving polishing performance. This work provides valuable reference data on the doping of Rare-Earth ions in CeO2-based polishing abrasives.

Mineralization of sulfide mound at Wocan-1 hydrothermal field based on geological mapping, mineralogy and sulfur isotope studies, Carlsberg Ridge, Northwest Indian Ocean

The Wocan-1 hydrothermal field is distinct on the occurrence of an active sulfide mound, discovered on an axial volcanic ridge of the slow-spreading Carlsberg Ridge. The size of the mound is comparable to TAG active mound located in off-axis of Mid-Atlantic Ridge. In order to understand its formation and controlling factors, we did field geological mapping, mineralogical and geochemical analysis on the hydrothermal precipitates. Our results show the sulfide mound is ∼ 260 m in diameter and ∼ 50 m in height. The southern area of the mound is enriched in high-temperature Cu-rich sulfides, while the northern area is characterized by moderate-temperature Fe-rich sulfides and a talus of pyrite-anhydrite breccias and sands extending for > 200 m. The pyrite here exhibits recrystallization textures characterized by heavier δ34S compositions when compared to that in the southern area. It is considered that the normal faults extending into the northern area of the mound and the associated mass wasting facilitated the infiltration of seawater, which is responsible for the regional difference in mineralization of the mound. This study contributes to the understanding of the formation and controls of large sulfide mounds on the AVRs at the slow-spreading ridges.

Efficient reclamation of phosphorus from wetland biomass waste via liquid-recirculated hydrothermal carbonization and precipitation

Hydrothermal carbonization (HTC) for the recovery of phosphorus (P) from biomass wastes has attracted considerable attention, while migration of P to the liquid phase greatly weakened P recovery efficiency and elevated the environmental risk. Therefore, a systematic scheme was proposed in this work to accomplish the complete reclamation of P from wetland plant (Ceratophyllum demersum) through coupling liquid-recirculated HTC mediated by H2O or H2SO4 with precipitation, and the migration and speciation of P during this process was determined by P K-edge X-ray absorption near edge structure, 31P nuclear magnetic resonance, and the modified sequential extraction. The P concentration in the liquid phase increased with the recirculation of HTC process water, and reached up to 550.6 mg L-1. >98.1 % of P in the recirculated liquid products was recovered in the forms of hydroxyapatite and struvite with the HTC mediums of H2O and H2SO4, respectively, without the addition of exogenous metals. In addition to the production of P compounds, P-enriched hydrochar was simultaneously obtained during this process. The HTC medium and liquid recirculation had profound impact on the hydrochar characteristics and the transformation of P. Hydroxyapatite and magnesium phosphate were the dominant P species in the hydrochars derived from H2O-mediated HTC, while FePO4 and other Ca-P species [Ca3(PO4)2 and Ca(H2PO4)2] dominated the P compounds in the H2SO4-mediated hydrochar. These results suggest that coupling liquid-recirculated HTC and precipitation could be a promising strategy for P reclamation, which could provide new insights into the P recovery from biomass waste.

Hydrothermal calcite formation in Campi Flegrei caldera, Italy: unraveling carbon sink processes in alkaline volcanic systems

Understanding carbon dioxide emissions variability in volcanic regions is vital for detecting instabilities in the subvolcanic plumbing system, crucial for managing both volcanic and environmental risks. While changes in magmatic sources drive these variations, non-magmatic processes can complicate signal interpretation, especially in caldera environments. Here, geothermal systems can sequester CO2 within the bedrock through hydrothermal calcite precipitation, significantly impacting surface-level CO2 emissions. Unfortunately, few studies have explored this phenomenon, examining hydrothermal calcite origins and their effects on carbon balances and temporal gaseous patterns in active volcanic settings. Our study developed a specialized methodology for quantifying CO2 sequestered in hydrothermal calcites within alkaline caldera systems. We focused on analyzing hydrothermal calcite in lithics from volcanic deposits of eruptions of varying ages, Volcanic Explosivity Index (VEI), and eruptive vent locations to enhance the representativeness of the entire caldera bedrock. Unlike core samples from geothermal wells, which are infrequent and limited to specific depths, lithics can be easily collected, offering a comprehensive understanding of CO2 sequestration. Through extensive 3D textural characterization and isotopic investigations on hydrothermal calcite within lithic fragments from selected alkaline volcanic deposits in the Campi Flegrei caldera, our findings emphasized the significant influence of calcite sinks on the overall CO2 budget released by volcanoes throughout their evolution.

Separation of nickel and iron from ferronickel via sulfuric acid leaching and hydrothermal precipitation

ABSTRACT Here, a hydrometallurgical process was proposed to separate nickel (Ni) and iron (Fe) from ferronickel. The effects of different factors, namely hydrothermal temperature, initial Fe2+ concentration, and Ni2+ concentration, on the hematite precipitation process, were detail investigated. Ferronickel powders were leached using a 120 g/L H2SO4 solution at 85 °C for 8 h. The final pH of the leaching solution was controlled at 3.0−4.5, and the Fe2+ concentration was maintained at 50−60 g/L. Copper from the ferronickel powder was first leached in the early stage of the leaching process, and then it was reduced by an excess of ferronickel powder, leading to its enrichment in the leaching residue. Approximately 50 g/L of Fe ions was successfully removed and precipitated as hematite containing 60% Fe, 0.3% Ni, and 1.5% S during hydrothermal precipitation at 200 °C for 3 h. Through evaporation crystallization at 90 °C for 8 h, large particles of nickel sulfate hexahydrate (NiSO4·6H2O) containing 19.4% Ni, 0.074% Fe, and 10.69% S were obtained. Moreover, through freezing crystallization at −8 °C for 1 h, smaller particles of NiSO4·6H2O product containing 20.3% Ni, 0.014% Fe, and 11.13% S were synthesised.

The Three-Dimensional Hierarchical Structure of Bi x -Sn1-x O2 Used for Ultrasensitive Detection of Butanone under UV Irradiation.

Recent studies have identified butanone as a promising biomarker in the breath of lung cancer patients, yet the understanding of its gas-sensing properties remains limited. A key challenge has been to enhance the gas-sensing performance of materials toward butanone, particularly under ultraviolet light exposure. Herein, we report the synthesis of a novel three-dimensional composite material composed of SnO2 incorporated with Bi2O3 using facile hydrothermal and impregnation precipitation methods. Detailed physical and chemical characterizations were performed to assess the properties of the developed material. Upon activation with ultraviolet light, our composite exhibited exceptionally high sensitivity to butanone. Remarkably, the butanone response was nearly 3 times greater for the Bi2O3-loaded SnO2 composite than for pristine SnO2, achieving a response value of 70. This substantial improvement is due to the synergistic effect of the material's distinctive three-dimensional architecture and the presence of Bi2O3, which significantly augmented the gas-sensing capability of butanone. To elucidate the underlying gas-sensing mechanism, we conducted first-principles calculations using density functional theory (DFT). The computational analysis revealed that the Bi2O3-containing system possesses superior adsorption energy for butanone. Ultimately, our findings suggest that the Bi-SnO2 composite holds great promise as an optimal sensing material for the detection of butanone under ultraviolet illumination.

The Chain of Processes Forming Porphyry Copper Deposits—An Invited Paper

Abstract Porphyry-related mineral deposits are giant geochemical anomalies in the Earth’s crust with orders-of-magnitude differences in the content and proportion of the three main ore metals Cu, Au, and Mo. Deposit formation a few kilometers below surface is the product of a chain of geologic processes operating at different scales in space and time. This paper explores each process in this chain with regard to optimizing the chances of forming these rare anomalies. On the lithosphere scale, deposits with distinct metal ratios occur in provinces that formed during brief times of change in plate motions. Similar metal ratios of several deposits in such provinces compared with global rock reservoirs suggest preceding enrichment of Au or Mo in lithospheric regions giving rise to distinct ore provinces. The largest Cu-dominated deposits and provinces are traditionally explained by selective removal of Au during generation or subsequent evolution of mantle magmas, but the possibility of selective Cu pre-enrichment of lithosphere regions by long-term subduction cannot be dismissed, even though its mechanism remains speculative. Evolution of hydrous basaltic melts to fertile magmas forming porphyry Cu deposits requires fractionation toward more H2O-rich magmas in the lower crust, as shown by their adakite-like trace element composition. The prevailing interpretation that this fractionation leads to significant loss of chalcophile ore metals by saturation and removal of magmatic sulfide might be inverted to a metal enrichment step, if the saturating sulfides are physically entrained with the melt fraction of rapidly ascending magmas. Ascent of fertile magma delivers a large mass of H2O-rich ore fluid to the upper crust, along points of weakness in an overall compressive stress regime, within a limited duration as required by mass and heat balance constraints. Two mechanisms of rapid magma ascent are in debate: (1) wholesale emplacement of highly fractionated and volatile-rich granitic melt into a massive transcrustal channelway, from which fluids are exsolved by decompression starting in the lower crust, or (2) partly fractionated magmas filling a large upper crustal magma chamber, from which fluids are expelled by cooling and crystallization. Transfer of ore-forming components to a hydrothermal ore fluid is optimized if the first saturating fluid is dense and Cl rich. This can be achieved by fluid saturation at high pressure, or after a moderately H2O rich intermediate-composition melt further crystallizes in an upper crustal reservoir before reaching fluid saturation. In either case, metals and S (needed for later hydrothermal sulfide precipitation) are transferred to the fluid together, no matter whether ore components are extracted from the silicate melt or liberated to the ore fluid by decomposition of magmatic sulfides. Production and physical focusing of fluids in a crystallizing upper crustal magma chamber are controlled by the rate of heat loss to surrounding rocks. Fluid focusing, requiring large-scale lateral flow, spontaneously occurs in mushy magma because high water content and intermediate melt/crystal ratio support a network of interconnected tubes at the scale of mineral grains. Calculated cooling times of such fluid-producing magma reservoirs agree with the duration of hydrothermal ore formation measured by high-precision zircon geochronology, and both relate to the size of ore deposits. Ore mineral precipitation requires controlled flow of S- and metal-rich fluids through a vein network, as shown by fluid inclusion studies. The degree of hydrothermal metal enrichment is optimized by the balance between fluid advection and the efficiency of cooling of the magmatic fluid plume by heat loss to convecting meteoric water. The depth of fluid production below surface controls the pressure-temperature (P-T) evolution along the upflow path of magmatic fluids. Different evolution paths controlling density, salinity, and phase state of fluids contribute to selective metal precipitation: porphyry Au deposits can form at shallow subvolcanic levels from extremely saline brine or salt melt; high-grade Au-Cu coprecipitation from coexisting and possibly rehomogenizing brine and vapor is most efficient at a depth of a few kilometers; whereas fluids cooling at greater depth tend to precipitate Cu ± Mo but transport Au selectively to shallower epithermal levels. Exhumation and secondary oxidation and enrichment by groundwater finally determine the economics of a deposit, as well as the global potential of undiscovered metal resources available for future mining.

An efficient approach for preparation of battery-grade Li2CO3 from intermediate product Li2SiO3

The continuous development of lithium-ion batteries (LIBs) manufacturing industry calls for the mass production of Li2CO3, which serves as a pivotal raw material for LIBs. In our previous study, Li was successfully precipitated as intermediate product Li2SiO3 from an alkaline solution containing Si by the hydrothermal precipitation method, realizing the preliminary separation of Li and impurities. In this research, H2SO4 digestion-water leaching-Na2CO3 precipitation process was proposed to manufacture Li2CO3 from the intermediate product Li2SiO3. Firstly, the reaction feasibility of H2SO4 digestion-water leaching and direct H2SO4 leaching for Li2SiO3 were comparatively evaluated through thermodynamic calculation and experimental research. Compared to direct H2SO4 leaching, H2SO4 digestion-water leaching process is preferred in view of its excellent filtration properties. Subsequently, systematic digestion and leaching experiments showed that up to 97.1 % of Li was extracted under the optimized conditions, and the concentration of Li in the leach liquor is as high as 29.33 g/L. After pH adjustment and Al removal, Na2CO3 precipitation were adopted for Li2CO3 production. The equilibrium relationship in Li2SO4-Na2CO3-H2O system was analyzed to predict the precipitation behavior of Li and select appropriate operation window for Li2CO3 preparation. Finally, with an additional carbonation-decomposition process, a Li2CO3 product with a purity of 99.51 % is produced. This process realizes efficient synthesis of battery-grade Li2CO3 from the intermediate product Li2SiO3.

Ultrasound‒induced facile synthesis of spinel CoFe2O4‒PAC magnetic nanocatalyst for remediation of hypersaline petrochemical wastewater: Degradation mechanism, biodegradability enhancement and phytotoxicity mitigation

In this study, magnetic CoFe2O4−PAC nanocatalysts were synthesized through facile hydrothermal and co‒precipitation approaches with ultrasonic irradiation, which were used for the treatment of hypersaline petrochemical wastewater (HPCW). When an ultrasound‒induced synthesis process (US@CoFe2O4‒PAC) was used, a more efficient and stable magnetic spinel CoFe2O4‒PAC nanocatalyst was developed. The application of this nanocatalyst as a PMS activator, not only caused eradication of 90.4% of chemical oxygen demand (COD) of a HPCW after 90 min reaction time under the optimum conditions (pH 5−6, catalyst dose 1.0 g/L and 1.0 mM PMS), but also led to marginal leaching of iron (314 μg/L) and cobalt (95 μg/L) from the nanocatalyst. Recycling experiments over five consecutive runs showed a negligible decrease (7.2%) in COD removal efficiency which proved the stability and reusability of magnetic US@CoFe2O4−PAC. Two main mechanisms of adsorption and catalytic oxidation processes (homogeneous and heterogeneous PMS) are involved simultaneously in the PMS/US@CoFe2O4−PAC system, which are responsible for the destruction of refractory contaminants of HPCW through the generation of SO4•‒ and OH• radicals. COD of HPCW was mainly removed through SO4•− radical attack (73.6%) and the biodegradability of HPCW was enhanced dramatically after 90 min reaction time. The germination index (GI) of raw HPCW was increased 17.1 ± 4.2% and 24.3 ± 8.8% after 15 and 90 min reaction time, respectively, even PMS/US@CoFe2O4−PAC system showed less impact on phytotoxicity mitigation. Hence, it can be recommended to dilute the effluent before using for irrigational purpose. The findings of this study present practical significance of spinel US@CoFe2O4−PAC, which is an environment‒friendly catalyst, easy to handle and can sustain long‒term operation for the treatment of recalcitrant hypersaline wastewater and the other potential practical applications.

Separation of Iron from ZnSO4 solution by oxygen pressure-enhanced hydrothermal precipitation

ABSTRACT This study presented a method for removing iron (Fe) from zinc (Zn) sulfate solution utilising an oxygen (O2) pressure-enhanced goethite process. The study investigated the effects of O2 pressure, reaction temperature (T), pH value, and reaction time (t) on the Fe removal process. The results indicated that the oxidation rate increased with increasing T and O2 pressure. The goethite obtained at an O2 partial pressure of 0.2 MPa exhibited higher Fe content and a distinct acicular morphology, containing 55.7% Fe, 5.4% Zn, and 1.9% Sulphur (S). The increase in temperature from 90°C to 110°C accelerated the Fe hydrothermal precipitation, enhancing the Fe content in the goethite from 55.7% to 57.1%. The goethite products with 56.4% Fe content exhibited 95.0% crystallinity at a pH of 3.2, with a tendency for particle aggregation at lower crystallinity levels. The goethite precipitation occurred within the pH range of 2.2−3.5. Furthermore, as the reaction time increased, the hydrothermal precipitation particles increased in size and exhibited higher Fe content. The proposed method modified the O2 mass transfer process, increasing its solubility to enhance the Fe2+ oxidation rate, facilitating the controlled acicular α-FeOOH production with excellent crystallization performance.

Synergistic effect of ZnO/Ag2O@g-C3N4 based nanocomposites embedded in carrageenan matrix for dye degradation in water

This research achieved success by synthesizing innovative nanocomposite composed of zinc oxide (ZnO), graphitic carbon nitride (g-C3N4) and silver oxide (Ag2O) nanomaterials incorporated into a carrageenan matrix, thus creating an environmentally friendly and stable support structure. The synthesis process involved hydrothermal and chemical precipitation methods to create photocatalytic g-C3N4, ZnO, and Ag2O nanocomposites. The success is evident through the characterization results, which unveiled distinctive peaks corresponding to Zn–O (590-404 cm−1) and Ag–O (2072 cm−1) stretching in the Fourier transform infrared (FTIR) and X-ray diffraction (XRD) analyses, conclusively confirming the successful synthesis of g-C3N4, ZnO, Ag2O, and their respective nanocomposites. Further validation through a scanning electron microscope coupled with an energy dispersive spectrometer (SEM-EDX) and elemental mapping affirmed the presence of Zn, O, Ag, C, and N. Additionally, transmission electron microscope (TEM) imaging unveiled the nanosheet morphology of g-C3N4, the nanorod structure of ZnO, and the spherical form of Ag2O nanomaterials. ZnO and Ag2O nanomaterials demonstrated a consistent 10–20 nm size range. To underscore their ability to harness visible light, the nanomaterials were excited at 380 nm, emitting visible light emission within the 400–450 nm range. The synthesized nanocomposites showcased outstanding adsorption and photocatalytic properties, achieving efficiency ranging from 80 % to 98 %, attributed to the synergistic interactions between the various components. These findings culminate in a confirmation of the research's success, validating the exceptional potential of these nanocomposites for various applications.

Discovery of the first hydrothermal field along the 500-km-long Knipovich Ridge offshore Svalbard (the Jøtul field)

Oceanic spreading centers north of Iceland are characterized by ultraslow spreading rates, and related hydrothermal activity has been detected in the water column and at the seafloor along nearly all ridge segments. An exception is the 500-km-long Knipovich Ridge, from where, until now, no hydrothermal vents were known. Here we report the investigation of the first hydrothermal vent field of the Knipovich Ridge, which was discovered in July 2022 during expedition MSM109. The newly discovered hydrothermal field, named Jøtul hydrothermal field, is associated with the eastern bounding fault of the rift valley rather than with an axial volcanic ridge. Guided by physico-chemical anomalies in the water column, ROV investigations on the seafloor showed a wide variety of fluid escape sites, inactive and active mounds with abundant hydrothermal precipitates, and chemosynthetic organisms. Fluids with temperatures between 8 and 316 °C as well as precipitates were sampled at four vent sites. High methane, carbon dioxide, and ammonium concentrations, as well as high 87Sr/86Sr isotope ratios of the vent fluids indicate strong interaction between magma and sediments from the Svalbard continental margin. Such interactions are important for carbon mobilization at the seafloor and the carbon cycle in the ocean.

RGO modified α-Fe2O3–ZnFe2O4 heterojunction for improving sensing performance of α-Fe2O3 to triethylamine

In order to develop a sensitive, stable and cheap gas sensor for detection of triethylamine (TEA), the bimetal oxide of ZnFe2O4 with α-Fe2O3 heterojunctions with different proportions were synthesized and reduced graphene oxide (rGO) modified on heterojunctions by hydrothermal and chemical precipitation methods. The gas-sensing tests to TEA showed that the 6α-Fe2O3/ZnFe2O4-rGO (0.8 wt%) composite has highest response reaches 10.48–20 ppm TEA with a rapid response time of 29 s, an impressively low detection limit of 0.145 ppm and reliable stability within 32 days at operating temperature of 143 °C. Compared with reported before, it has higher response at lower operating temperature and lower concentration of test gas. The enhancing mechanism is attributed to the formation of semiconductor heterojunction, which makes the resistance of composite in air further increase and further decrease in TEA compared with α-Fe2O3 due to generating an additional electron depletion layer in the heterojunction interface, while rGO accelerates the electron transfer and provides more active sites for gas adsorption.

Synergistic effect of CuBi2O4/Bi2S3 dispersed over rGO layers for removal of toxic effluents photocatalytically

Water pollution is the major issue to be resolved nowadays. To overcome water pollution, the use of nanotechnology proved to be an emerging field. In this project, CuBi2O4 (CB-1) and Bi2S3 (CB-2) were prepared by simple hydrothermal and chemical precipitation routes respectively. To enhance the effectiveness of the photocatalyst, the synthesis of CuBi2O4/Bi2S3 (CB-3) and CuBi2O4/Bi2S3/rGO (CB-4) nanocomposite were carried out by ultrasonication method. Different physiochemical techniques were used to characterize the as prepared catalysts. The photocatalytic activity of fabricated catalysts was then checked for methylene blue degradation. Among all the samples, CB-4 showed the best photocatalytic performance (90.47 %) as it has low band gap energy than other fabricated materials. Therefore, the fabricated nanocomposite can be employed as a promising photocatalytic material for future use.

Efficient fluoride removal using nano MgO: mechanisms and performance evaluation.

In this study, highly efficient fluoride removal of nano MgO was successfully synthesized using a simple hydrothermal precipitation method. Hexadecyl trimethyl ammonium bromide (CTMAB) was utilized as a surfactant. Its long-chain structure tightly wrapped around the precursor crystal of basic magnesium chloride, inhibiting the growth of precursor crystals, reducing their size, and improving crystal dispersion. This process enhanced the adsorption capacity of nano MgO for fluoride. The adsorption performance of nano MgO on fluoride was investigated. The results indicate that pseudo-second-order kinetics and the Langmuir isotherm model can describe the adsorption behavior for fluoride, with a maximum adsorption capacity of 122.47mg/g. Methods such as XRD, SEM, XPS, and FTIR were employed to study the adsorption mechanisms of the adsorbent. Additionally, factors potentially affecting adsorption performance in practical applications, such as pH and competing ions, were examined. This study enhances our profound understanding of the defluorination effectiveness and mechanisms of nano MgO.

Catalytic mechanism of Co-containing layered double hydroxide (Co-LDH) as a precursor in carbon nanotube (CNT) synthesis

Abstract The synthesis of carbon nanotubes (CNTs) by water-assisted chemical vapor deposition using Co-containing layered double hydroxides (Co-LDH) as catalyst precursors and the catalytic mechanism of Co-LDH catalyst precursors during CNT synthesis were investigated. Co-Al and Co-Mg-Al LDH were prepared by the hydrothermal or homogeneous precipitation method using urea. XPS analysis indicated an increase in Co0 content after a reduction process during CNT synthesis, and the TEM images show that metallic Co nanoparticles were formed while maintaining the LDH platelet-like crystal form. Consequently, these metal particles were found to act as the catalyst for the formation of CNTs. Finally, through control of the flow rate of C2H4 gas during CNT synthesis, the formation of single-walled CNTs with diameters of 4 nm or less was demonstrated.

Research on Hydrothermal Iron Removal From Wet Zinc Refining Solutions and Iron Residue Reduces Emissions

For the conventional wet zinc refining processes of the jarosite method and goethite method of iron removal, the process that existed was iron residue low iron, high zinc, large amount of residue, and high cost of harmless treatment, this paper carried out a study on hydrothermal iron removal from wet zinc refining solutions and an iron residue that reduces emissions. The results show that the reaction temperature is a prerequisite for the precipitation of Fe3+ to precipitate hematite (Fe2O3). Prolonging the reaction time can induce the conversion of jarosite (KFe3(SO4)2(OH)6) to hematite. Increasing the partial pressure of oxygen will accelerate the oxidation of Fe2+ to Fe3+ and promote the formation of the hematite phase. Under the optimized technical parameters of reaction temperature 180 °C, oxygen partial pressure 0.6 MPa, reaction time 3 h, and controlled alkali metal ion concentration, 92.49% of the iron in the solution was precipitated into the residue in the form of hematite(Fe2O3), and the precipitated iron residue contained 57.75% iron and 0.82% zinc; compared with the jarosite process, the amount of iron residue was reduced by about 65%, and the zinc content of iron residue was reduced by 5.86%. The use of hydrothermal mineralization iron precipitation processes can realize the mineralization precipitation of iron in solution under low-acid conditions and obtain hematite iron precipitation residue with iron content up to the industry standard of iron oxide. And can be realized for resource utilization, helping the wet process zinc industry to develop in a green and low-carbon direction.

Superior photocatalytic performance of ZnMoO4/Ag2WO4 for degradation of trimethoprim and methylene blue

ABSTRACT In the present work, ZnMoO4/Ag2WO4 nanocomposite was synthesized via facile hydrothermal and chemical precipitation method for determination of photocatalytic performance on organic contaminants such as methylene blue and trimethoprim. The synthesized nano-photocatalyst was characterized using various instrumental techniques. Photocatalytic degradation of methylene blue and trimethoprim by the samples was realized under UV light irradiation. The obtained results demonstrated that photocatalytic degradation of methylene blue by ZnMoO4/Ag2WO4 was 99.6% in 30 min. The bare ZnMoO4 produced 57.8% and Ag2WO4 produced 76.7% photocatalytic degradation of methylene blue in 60 min. The synthesized ZnMoO4/Ag2WO4 nanocomposite, about which there is little information on remediation of organic pollutants, had possessed the outstanding photocatalytic degradation performance on methylene blue and trimethoprim due to pseudo first order kinetic.