Hydrothermal Precipitation Research Articles

Semiconductor Quantum Dots (CdX, X = S, Te, Se) Modify Titanium Dioxide Nanoparticles for Photodynamic Inactivation of Leukemia HL60 Cancer Cells

Titanium dioxide nanoparticles (TiO2-NPs) are highly efficient photosensitizers in traditional photodynamic therapy (PDT). The particle size of TiO2-NPs is small, only about 20 nm. However, the demands of ultraviolet light (UV) excitation feature shallow tissue penetration depth and may lead to severe tissue photon damage. Thus, in this research, TiO2-NPs are modified with semiconductor quantum dots (QDs) CdX (X = S, Te, Se) in various methods, such as ultrasonic, hydrothermal, sol-gel, aqueous phase, and hydrolysis precipitation. The transmission electron microscopy (TEM) images show that the size of CdSe-TiO2 is ranging from 6 to 14 nm. The ultraviolet-visible (UV-Vis) spectrum demonstrates that the CdX (X = S, Te, Se) modification can successfully extend the absorption range of TiO2-NPs into a different visible light region. CdSe QDs have the narrowest band gap compared with CdX (X = S, Te, Se) QDs. Visible light-activated CdSe-TiO2 nanocomposite shows the highest PDT inactivation efficiency toward HL60 cells compared with CdX-TiO2. The photogenerated carrier separation efficiency of CdSe-TiO2 nanocomposite is the highest shown in a fluorescence spectrum (FS). Furthermore, when conjugated with folic acid (FA), the prepared FA-CdX-TiO2 (X = S, Se) exhibits excellent cancer-targeting ability during PDT treatment. Optimum PDT efficiency of FA-CdSe-TiO2 indicates that photocatalytic and targeting ability is much higher than pure TiO2 and CdSe-TiO2. Our results provided a detailed investigation on the PDT performance of CdX (X = S, Te, Se) modified TiO2 and may act as a guide for further design of highly targeted performance visible-light response TiO2-NPs.

Porphyry copper deposit formation in arcs: What are the odds?

AbstractArc magmas globally are H2O-Cl-S–rich and moderately oxidized (ΔFMQ = +1 to +2) relative to most other mantle-derived magmas (ΔFMQ ≤ 0). Their relatively high oxidation state limits the extent to which sulfide phases separate from the magma, which would otherwise tend to deplete the melt in chalcophile elements such as Cu (highly siderophile elements such as Au and especially platinum-group elements are depleted by even small amounts of sulfide segregation). As these magmas rise into the crust and begin to crystallize, they will reach volatile saturation, and a hydrous, saline, S-rich, moderately oxidized fluid is released, into which chalcophile and any remaining siderophile metals (as well as many other water-soluble elements) will strongly partition. This magmatic-hydrothermal fluid phase has the potential to form ore deposits (most commonly porphyry Cu ± Mo ± Au deposits) if its metal load is precipitated in economic concentrations, but there are many steps along the way that must be successfully negotiated before this can occur. This paper seeks to identify the main steps along the path from magma genesis to hydrothermal mineral precipitation that affect the chances of forming an ore deposit (defined as an economically mineable resource) and attempts to estimate the probability of achieving each step. The cumulative probability of forming a large porphyry Cu deposit at any given time in an arc magmatic system (i.e., a single batholith-linked volcanoplutonic complex) is estimated to be ~0.001%, and less than 1/10 of these deposits will be uplifted and exposed at shallow enough depths to mine economically (0.0001%). Continued uplift and erosion in active convergent tectonic regimes rapidly remove these upper-crustal deposits from the geological record, such that the probability of finding them in older arc systems decreases further with age, to the point that porphyry Cu deposits are almost nonexistent in Precambrian rocks.A key finding of this paper is that most volcanoplutonic arcs above subduction zones are prospective for porphyry ore formation, with probabilities only falling to low values at late stages of magmatic-hydrothermal fluid exsolution, focusing, and metal deposition. This is in part because of the high threshold required in terms of grade and tonnage for a deposit to be considered economic. Thus, the probability of forming a porphyry-type system in any given arc segment is relatively high, but the probability that it will be a large economic deposit is low, dictated to a large extent by mineral economics and metal prices.

Performance of sunlight responsive WO3/AgBr heterojunction photocatalyst toward degradation of Rhodamine B dye and ofloxacin antibiotic

A sunlight responsive WO3/AgBr heterojunction photocatalyst was prepared using hydrothermal and chemical precipitation methods. The photocatalyst with band gap of 2.93 eV exhibited high efficiency of 86% toward degradation Rhodamine B (RhB) dye under visible light. Interestingly, nearly complete degradation of RhB dye and ofloxacin (OFL) antibiotic under natural sunlight was achieved. Creation of the WO3/AgBr heterojunction is a promising strategy for enhancement of the photoactivity. This may be due to a decrease of charge carrier recombination rate at the interface and an increase in visible light absorption range of the resultant photocatalyst in comparison to those obtained from the pristine photocatalysts. Photogenerated hole plays the major role in photodegradation of the pollutant. The photocatalyst remains stable and still shows high efficiency after five consecutive cycles confirming its excellent cycling ability. This research demonstrates a promising performance of the sunlight active WO3/AgBr heterojunction photocatalyst for detoxification of dye and antibiotic in wastewater by utilization of an economical solar energy.

Enhanced degradation toward Levofloxacin under visible light with S-scheme heterojunction In2O3/Ag2CO3: Internal electric field, DFT calculation and degradation mechanism

• A novel S-scheme heterojunction In 2 O 3 /Ag 2 CO 3 composite was successfully synthesized. • The degradation rate reaches 86.1% of Levofloxacin during 90 min under visible light. • Heterojunction In 2 O 3 /Ag 2 CO 3 accelerates the separation of photogenerated carriers. • Reaction mechanism, intermediate product and electron transfer pathway are discussed. As we know, constructing a heterojunction with two semiconductors by matching energy bands can greatly promote photocatalytic performance. For this reason, a novel S-scheme heterojunction of In 2 O 3 /Ag 2 CO 3 was synthesized with in-situ hydrothermal precipitation methods. The characteristics and DFT calculation prove that the transfer of photogenerated electrons in the In 2 O 3 /Ag 2 CO 3 system follows the mechanism of S-scheme heterojunction. And the internal electric field (IEF) resulted from the S-scheme heterojunction of In 2 O 3 /Ag 2 CO 3 drives the direct transferring of photogenerated electrons from the conduction band of Ag 2 CO 3 to valence band of In 2 O 3 , resulting in an efficient separation of photogenerated electron-hole pairs and great accumulation of e – and h + on the CB of In 2 O 3 and VB of Ag 2 CO 3 , respectively. The photoluminescence lifetime of In 2 O 3 /Ag 2 CO 3 is greatly extended to 8.42 ns, and holes and hydroxyl radicals are the most important active radicals. As-prepared S-scheme heterojunction of In 2 O 3 /Ag 2 CO 3 shows the highest photodegradation rate (86.1%) and mineralization ability (46.2%) toward Levofloxacin under visible light. Finally, both probable degradation pathway and mechanism were presented. This work suggests a feasible method to construct a S-scheme heterojunction to optimize the redox ability of photocatalyst and promote the photocatalytic degradation capability toward harmful pollutants under visible light.

Hollow Fe/Ni–CoTe@NCFs nanoarchitecture derived from MOF@MOF as high-efficiency electrocatalysts for boosting oxygen evolution reaction

To improve the oxygen evolution reaction (OER) catalytic efficiency of non-noble-metal-based catalysts, researchers have made great endeavors to adjust the compositions, morphologies and configuration of material. In this work, a dual-metal-organic frameworks (MOFs)-assisted fabrication hierarchical and hollow N-doped carbon nanoframes (NCFs) decorated with Fe/Ni-codoped CoTe nanocomposite catalyst (Fe/Ni–CoTe@NCFs) is reported. Starting from MOF-in-MOF composite precursors, the design and fabrication of Fe/Ni–CoTe by the strategies: i.e, hydrothermal precipitation, chemical etching and low-temperature tellurization, and high-temperature pyrolysis steps. Newly designed catalyst (Fe/Ni–CoTe@NCFs) performs superior OER catalytic activity to afford 10 mA cm−2 at the overpotential of 287 mV with a small Tafel slope of 52.3 mV dec−1. The frame-like hollow core-shell nanostructures with ample channels into the internal volume and high double-layer capacitance provide the large catalytic active surface area and increase more actives sites. The cooperative effects between alloy and metal telluride, as well as hollow carbon shell promote the activity of OER. Therefore, this study offers a catalyst with great potential for OER and provides the possibility for the application of transition metal tellurides in electrocatalysis.

Optimization of the Mechanical Properties and the Cytocompatibility for the PMMA Nanocomposites Reinforced with the Hydroxyapatite Nanofibers and the Magnesium Phosphate Nanosheets.

Commercial poly methyl methacrylate (PMMA)-based cement is currently used in the field of orthopedics. However, it suffers from lack of bioactivity, mechanical weakness, and monomer toxicity. In this study, a PMMA-based cement nanocomposite reinforced with hydroxyapatite (HA) nanofibers and two-dimensional (2D) magnesium phosphate MgP nanosheets was synthesized and optimized in terms of mechanical property and cytocompatibility. The HA nanofibers and the MgP nanosheets were synthesized using a hydrothermal homogeneous precipitation method and tuning the crystallization of the sodium-magnesium-phosphate ternary system, respectively. Compressive strength and MTT assay tests were conducted to evaluate the mechanical property and the cytocompatibility of the PMMA-HA-MgP nanocomposites prepared at different ratios of HA and MgP. To optimize the developed nanocomposites, the standard response surface methodology (RSM) design known as the central composite design (CCD) was employed. Two regression models generated by CCD were analyzed and compared with the experimental results, and good agreement was observed. Statistical analysis revealed the significance of both factors, namely, the HA nanofibers and the MgP nanosheets, in improving the compressive strength and cell viability of the PMMA-MgP-HA nanocomposite. Finally, it was demonstrated that the HA nanofibers of 7.5% wt and the MgP nanosheets of 6.12% wt result in the PMMA-HA-MgP nanocomposite with the optimum compressive strength and cell viability.

Multi-stage carbonate veins at IODP Site U1504 document Early Cretaceous to early Cenozoic extensional events on the South China Sea margin

Recognition of the pre-spreading tectonic characteristics of the South China Sea (SCS) continental margin is key to understanding how the SCS opened. However, information on this subject is extremely scarce because of the lack of direct chronological constraints on deformation events. The International Ocean Discovery Program sampled greenschist-facies mylonite from the basement of the Outer Margin High at site U1504 in the SCS, which could provide information on the pre-spreading history. The microstructure analysis revealed that two episodes of extension had affected the mylonites, namely early ductile and late brittle deformation. Pre-mylonite, syn-mylonite and post-mylonite carbonate veins were identified on the basis of the intersecting relationships with the mylonite foliation. The pre-mylonite carbonate veins yielded U–Pb ages of 210 ± 20 and 195 ± 32 Ma, which might represent the age of the protolith. The age of the syn-mylonite carbonate vein is 135 ± 12 Ma. No effective ages were obtained for the post-mylonite carbonate veins using U–Pb dating. The δ13C, δ18O and 87Sr/86Sr compositions of the post-mylonite carbonate veins suggest that they were formed by hydrothermal fluid precipitation dominated by seawater. Considering the extensively developed marine environment in the northern continental margin after the late Eocene, the post-mylonite carbonate veins at site U1504 likely formed in the Eocene or later. Combining the microstructure, geochemistry and seismic profile, we hypothesize that post-mylonite carbonate veins were formed during early Cenozoic rifting. In reference to the geological background, we conclude that the basement of the SCS margin experienced at least two stages of extension before spreading: the first stage occurred during the Early Cretaceous and was caused by rollback of the Paleo-Pacific plate; the second occurred in the early Cenozoic because of passive rifting. These multiple extensional events of the active continental margin and of the passive margin collectively resulted in thinning the SCS continental margin.

Effect of pH on the In Vitro Biocompatibility of Surfactant-Assisted Synthesis and Hydrothermal Precipitation of Rod-Shaped Nano-Hydroxyapatite.

Given their wide range of biomedical applications, hydroxyapatite (HA) nanoparticles are an attractive material widely used in many fields. Therefore, a simple, inexpensive, and stable process for the synthesis of HA nanoparticles is necessary to meet current needs. Herein, we studied HA synthesis assisted by four surfactants, namely cation, anion, non-ionic, and zwitterion templates, to verify the synthesis phase, aspect ratio, morphology, and biocompatibility under different environments (i.e., pH 4 and 9) before and after calcination. Results showed that before calcination, the surfactant-free groups could not produce HA but showed an abundant dicalcium phosphate anhydrous (DCPA) phase at pH 4. Except for the anionic group containing a small amount of DCPA, all surfactant-assistant groups presented single-phase HA in acidic and alkaline environments. The diameter of HA synthesized at pH 4 was significantly larger than that of HA synthesized at pH 9, and the effect of aspect ratio changes after calcination was more significant than that before calcination. The uncalcined rod-shaped HA synthesized with a non-ionic template at pH 4 demonstrated excellent cell viability, whereas anionic, cationic, and non-ionic surfactants exhibited biocompatibility only after calcination. At pH 9, non-ionic and uncalcined zwitterion-assisted rod-shaped HA showed excellent biocompatibility. In conclusion, the uncalcined HA rod-shaped nanoparticles synthesized from the non-ionic template at pH 4 and 9 and the zwitterion template at pH 9, as well as all surfactant-assisted HA after calcination, had no cytotoxicity. These tailor-made non-toxic HA types can meet the different requirements of apatite composite materials in biomedical applications.

Hydrothermal precipitation of V3+ ions in V-bearing oxalic acid leachate to prepare V2O3

In our previous study, a novel method of direct leaching of V3+ ions in iron vanadate spinel minerals by oxalic acid synergized with Fe powder under hydrothermal conditions was developed. In the present study, we attempted to prepare V2O3 from this V-bearing oxalic acid leachate. First,the dissolution and precipitation behavior of V3+ ions in the V2O3-H2C2O4-H2O system were investigated at various mass ratios of V2O3 to H2C2O4 and temperatures. Then, according to the hydrothermal features of this system, two routes of preparing V2O3 were designed. In Route A, a certain amount of pure V2O3 reagent was added into the pregnant leachate as a nucleating agent and to adjust the ratio of V3+ to C2O42− ions in solution, and V2O3 was prepared from the V-bearing oxalic acid leachate by a one-step hydrothermal process. In Route B, a precursor composed of hybrid vanadium oxides was initially obtained from the V-bearing oxalic acid leachate by hydrothermal precipitation, and then the precursor was reduced in a 95% Ar + 5% H2 atmosphere at 700 °C to prepare the V2O3 product. Whether by route A or B, a V2O3 product with high crystallinity was obtained from the V-bearing oxalic acid leachate, and a higher extent of vanadium precipitation was achieved.

Controlled Hydrothermal Precipitation of Alunite and Natroalunite in High-Aluminum Vanadium-Bearing Aqueous System

During the acid leaching process of black shale, with the destruction of the aluminosilicate mineral structure, a large amount of aluminum (Al) is leached, accompanied by the release of vanadium (V). To separate aluminum from the vanadium-containing solution, the precipitation behavior of aluminum ions (Al3+) was investigated under hydrothermal conditions with the formation of alunite and natroalunite. In the solution environment, alunite and natroalunite are able to form stably by the Al3+ hydrolysis precipitation process at a temperature of 200 °C, a pH value of 0.4 and a reaction time of 5 h. When Al3+ was precipitated at a K/Al molar ratio of 1, the aluminum precipitation efficiency and the vanadium precipitation efficiency were 64.77% and 1.72%, respectively. However, when Al3+ was precipitated at a Na/Al molar ratio of 1, the precipitation efficiency of the aluminum decreased to 48.71% and the vanadium precipitation efficiency increased to 4.36%. The thermodynamics and kinetics results showed that alunite forms more easily than natroalunite, and the reaction rate increases with increasing temperature, and the precipitation is controlled by the chemical reaction. Vanadium loss increases as the pH value increases. It can be deduced that the ion state of tetravalent vanadium (VO2+) was transformed into the ion state of pentavalent vanadium (VO2+) in the hydrothermal environment. The VO2+ can be adsorbed on the alunite or natroalunite as a result of their negative surface charges, ultimately leading to vanadium loss.

Rapid Marcasite to Pyrite Transformation in Acidic Low-Temperature Hydrothermal Fluids and Saturation Index Control on FeS2 Precipitation Dynamics and Phase Selection

Pyrite is the most abundant metal sulfide in the Earth’s crust and is also found on Mars. It can form by direct hydrothermal precipitation or by polymorphic phase transformation from marcasite. However, the control on the dynamics of hydrothermal pyrite precipitation is poorly understood, and the kinetics of the hydrothermal transformation from marcasite to pyrite is unknown. To address these issues, we quantified pyrite and marcasite formation in hydrothermal fluids at pH 1, using pyrrhotite as a precursor mineral to produce supersaturated solutions. In situ powder X-ray diffraction experiments at 190 °C showed that hydrothermal fluids rich in ΣS(-II) (0.2 molal) favored the precipitation of nanocrystal pyrite (∼20 nm) due to a high saturation index (>105), while ΣS(-II)-free fluids produced a mixture of marcasite and pyrite nanocrystals (21–46 nm) due to a low saturation index (<104). The fluid/rock ratio (70 and 120 g/g at 210 °C) can also affect the saturation indices of these fluids, influencing nucleation and crystal growth dynamics of pyrite and marcasite and resulting in complex evolution of crystallite size, phase abundance, and the pyrite/marcasite ratio. Ex situ hydrothermal experiments at 210 °C showed rapid transformation from marcasite to pyrite, with around 95% marcasite being transformed to pyrite in 20 weeks, compared to more than 6.3 million years at 210 °C under dry conditions based on extrapolation from previous kinetic studies. These results suggest that saturation index influences hydrothermal precipitation dynamics and controls phase selection between pyrite and marcasite and that marcasite may not survive over geological time in low-temperature (<200 °C), water-saturated environments.

Synthesis of Cerium Dioxide Nanoparticles by Gas/Liquid Pulsed Discharge Plasma in a Slug Flow Reactor

Cerium dioxide (CeO2) nanoparticles have gained immense attention owing to their use in various applications. Current synthesis methods for CeO2 nanoparticles including hydrothermal and chemical precipitation are time-consuming and require chemical reagents. In order to shorten the reaction time and avoid the use of organic reagents, a new method for CeO2 nanoparticles synthesis in a slug flow system by atmospheric-pressure pulsed discharge plasma was proposed, which provided an easy, efficient, and continuous reaction at room temperature. Cerium nitrate was used as a feed solution, and starch was added as a stabilizer to separate the nucleation and growth processes of the nanoparticles to prevent their aggregation. The system was powered by a high voltage of 10.0 kV (peak-to-peak) from an ac power supply. The products were characterized by transmission electron microscopy (TEM), high-resolution TEM, energy-dispersive X-ray spectroscopy, and UV–vis spectroscopy. The results showed that when a circular capillary glass tube coil was used as the slug flow reactor, the amount of the CeO2 nanoparticles increased compared to the case when a straight glass tube was used. The size also increased from 3.4 to 6.3 nm. The synthesis mechanism of the CeO2 nanoparticles by gas/liquid plasma was finally elucidated.

Vancomycin Hydrochloride Loaded Hydroxyapatite Mesoporous Microspheres with Micro/Nano Surface Structure to Increase Osteogenic Differentiation and Antibacterial Ability.

As infection induced by the implant will lead to operation failure, the implant material must be endowed with certain antibacterial properties. Hydroxyapatite (HA) mesoporous microspheres have been widely used in bone repair due to their advantages, including simple synthesis, good osteogenic properties and drug loading capacity. In this study, vancomycin hydrochloride-loaded mesoporous hydroxyapatite microspheres with micro/nanosurface structures were synthesized to increase osteogenic differentiation and antibacterial ability. Phytic acid (IP6) was used as a template to prepare mesoporous hydroxyapatite microspheres composed of fibres, flakes and smooth surfaces by the hydrothermal homogeneous precipitation method, and the corresponding specific surface areas were 65.20 m²/g, 75.13 m²/g and 71.27 m²/g, respectively. Vancomycin hydrochloride (Van) was used as the drug model to study the drug loading and release characteristics of the microspheres, as well as the in vitro antibacterial properties after treatment. In addition, during cocultivation with MC3T3-E1 preosteoblasts, HA microspheres assembled via flakes exhibited better cell compatibility, which promoted cell proliferation, alkaline phosphatase (ALP) activity, and the formation of calcium nodules and increased the expression of osteogenic differentiation-related proteins such as Runx-2, osteopontin (OPN) and collagen I (COL I). These results indicated that the HA microspheres prepared in this experiment have broad application prospects in drug delivery systems and bone repair.

Combinatorial Performance Mapping of Near-NMC111 Li-ion Cathodes

A combinatorial library of twenty-three, phase pure, near-NMC111 (LiNi0·33Mn0·33Co0·33O2) compositions were synthesised and their electrochemical performance, was mapped (in lithium ion half-cells). Each of the 23 compositions was made in series, using a two-step process of 1) a rapid initial continuous hydrothermal precipitation, followed by 2) solid state lithiation. The 23 lithiated NMC samples were then subjected to analytical methods including electron microscopy (selected samples), Powder X-ray Diffraction and electrochemical tests in half cell Li-ion configurations versus Li metal. A sample with a Ni:Mn:Co (NMC) ratio of 39:28:33, revealed a specific capacity of 150 mA h g−1 at a C/20 rate, which was 63 and 43% greater capacity than NMC111 and NMC433 samples produced in this work, respectively. The sample with NMC ratio 47:25:28, showed the best capacity retention characteristics, retaining 70% of its C/20 capacity at 1C, after 40 cycles. Further analysis of all the samples by cyclic voltammetry and electrochemical impedance spectroscopy, allowed compositional mapping of diffusion coefficients. Overall, the mapping data revealed a gradual change of properties across compositional space, which has validated our combinatorial approach and allowed identification of the optimum performing near-NMC111 cathode materials.

Effect of Ru3+ ions on the formation, structural, magnetic and optical properties of hematite (α-Fe2O3) nanorods

Nanosized hematite (α-Fe2O3) is a widely investigated material due to its favourable properties (chemically stable, environmentally safe, inexpensive) and very good performance in several advanced applications. Properties and performance of hematite nanoparticles can be adjusted and improved by modification of particle size and shape, as well as by substitution of Fe3+ ions in the crystal structure of hematite with other metal ions. Ru3+ ions are potentially suitable metal ions for the substitution of Fe3+ ions in hematite because of the same charge and similar ionic radii. In the present work, the effects of Ru3+ ions on the formation and properties of hematite nanorods prepared by combination of hydrothermal precipitation and calcination were investigated. The influence of the molar fraction of Ru3+ ions in the hydrothermal precipitation system on the formation and properties of iron oxide phases was studied. Single-phase goethite (α-FeOOH) nanorods containing incorporated Ru3+ ions were formed in the presence of low levels of Ru3+ ions (<3 mol%), while at higher levels (4 and 5 mol% Ru) hematite nanocylinders, consisting of self-assembled and fused nanoparticles, were obtained. The mechanism of the formation of these iron oxide nanostructures in the presence of Ru3+ ions was explained and compared with the effect of other metal cations reported in the literature. Ru-doped hematite nanorods were formed after calcination of Ru-doped goethite nanorods at 500 °C. A gradual elongation of hematite nanorods with increased Ru doping to highly elongated Ru-doped hematite nanoneedles at 2 mol% Ru was observed and explained. The influence of the Ru doping level on the magnetic properties of hematite nanorods was investigated using Mössbauer spectroscopy and magnetic measurements. Temperature of the transition between antiferromagnetic (AFM) and weakly ferromagnetic (WFM) spin ordering state (Morin transition) gradually rose with increasing Ru3+-for-Fe3+ substitution in hematite. Besides, magnetization of the WFM hematite gradually decreased with Ru doping which was attributed to the reduced canting of two almost antiparallel spin sublattices in this phase. The optical band gap in hematite nanorods was found to get gradually narrower with increased Ru doping due to the modified electronic structure.

Fabrication of Ag/Ag2O incorporated graphitic carbon nitride based ZnO nanocomposite for enhanced Z-scheme photocatalytic performance of various organic pollutants and bacterial disinfection

In this work, the development of a novel Ag/Ag2O combined g-C3N4/ZnO (g-C3N4/ZnO-Ag2O) ternary photocatalyst was successfully prepared by facile calcination and hydrothermal precipitation method. The crystalline phase structure, surface morphology, chemical compositions, and optical properties of the as-obtained g-C3N4/ZnO-Ag2O photocatalysts (PCs) samples were also characterized by XRD, FT-IR, FE-SEM with mapping, HR-TEM, XPS, UV-Vis DRS and PL spectra exclusively. The photocatalytic enhanced performance of as-obtained g-C3N4/ZnO-Ag2O heterostructured PCs was exploited to aqueous methylene blue (MB) dye and 4-chlorophenol than that of pristine g-C3N4 PCs within 120 mins under visible-light irradiation. The g-C3N4/ZnO-Ag2O composite exhibits a high photo-degradation rate constant and good recycling stability towards the MB dye photo-decomposition. The photocatalytic upgrading performance might be recognized to the synergistic effect at SPR interface of Ag/Ag2O NPs, which superior visible light fascination and separation/transfer of photo-excited charges over the g-C3N4/ZnO heterojunction interface. Besides, the possible Z-Scheme photo-degradation pathway and charge separation mechanism were discussed. Hence, the existing work could probably deliver a novel way to develop highly capable composite PCs for environmental wastewater remediation.

Hierarchically Nanostructured ZnO with Enhanced Photocatalytic Activity

Hierarchical nanostructures of ZnO are integrated architectures comprising well-ordered nanoscale subunits and excellent photocatalytic properties. In this study, synthesis of ZnO nanoparticles using methods such as co-precipitation, hydrothermal, thermal decomposition, and electrochemical precipitation yielded microsphere, nanorod, pyramid, and nanopetal-like morphologies, respectively. The catalysts obtained were characterized using XRD, IR, SEM-EDX, UVDRS, TGA, PL, and Zeta potential analysis. The XRD spectra confirmed that all the different morphologies of ZnO have hexagonal wurtzite structures The photocatalytic activity of these nanostructures was determined using a dye degradation study on a model pollutant Methylene Blue (MB) under simulated visible light. The kinetic study of the dye degradation reveals that it obeys pseudo-first-order kinetics with a maximum rate constant of 0.01503 min−1. The nanorod structured ZnO particles prepared by the hydrothermal method showed the best catalytic activity.

The Application of Geostatistical Analysis on Radiometric Mapping Data to Recognized the Uranium and Thorium Anomaly in West Sulawesi, Indonesia.

Mamuju Region in West Sulawesi, Indonesia is one of prospect area of uranium/thorium in Indonesia. High radiometric concentrations were located in Adang Volcanic Rocks. This formation is grouped as basaltic to intermediate rock and composed by lava, pyroclastic rocks, and tuff. Regional field radiometric mapping, including radiation dose rates, potassium, uranium, and thorium contents of soil and rock was conducted to identify the existence of radioactive minerals and prospect zones. Some radiometric anomalies are detected and probably related to hydrothermal alteration, leaching, and precipitation processes. Uranium anomaly (97,261 ppm) located in Mamuju River upstream, Botteng, Takandeang and Ahu area. The anomaly related to uranium leaching and precipitation processes in leucite basalt lava. Thorium anomaly (369,461 ppm) located in Pangasaan, Takandeang, Ahu, and Taan area. To expand this radiometric mapping, we characterized the reflectance of Landsat-8 imagery based on field measurement data. Based on circular structures identification, uranium/thorium anomaly are related to the existence of volcano vents on Adang Volcanic. Based on band rationing, high uranium contents distributed in the area with less ferromagnesian mineral, while thorium did not affect. These field based and remote sensing characterization results could be used as preliminary parameters to identify wide and detail prospects.

Effect of the particle size on the reactivity of MgO-Al2O3 hydrating mixtures: A long-term kinetic investigation of hydrotalcite synthesis

Hydrotalcite-like compounds (HTlc) are commonly known anionic clay that may potentially be used as hydraulic binder component for refractory materials, ion exchangers, catalyst or carrier of bioactive molecules. According to current state of knowledge LDH (Layered Double Hydroxides) can be synthesized using various methods including mechanochemical synthesis, hydrothermal precipitation, sol–gel syntheses and coprecipitation method. Research on the synthesis of hydrotalcite in the mixture of oxide powders of Al2O3 and MgO cured under specific conditions is particularly important in case of the determination of the relationship between the type (susceptibility to hydration, grain size and specific surface area) of initial powders and reaction kinetics. As a result, the hydration of an equimolar mixture of magnesium and alumina oxides nano- or micro-powders has been proven to be an effective low temperature method of synthesis well crystallized MgAl LDH with highly ordered structures. This investigations clearly show that the kinetics of hydration is influenced only by properties of aluminium oxide as initial powder. The synthesis of Mg6Al2CO3(OH)16∙4H2O as a result of hydration is associated with composite matrix formation which firstly consist of partly reacted initial powders bonded by hydration products. The synthesis of Mg6Al2CO3(OH)16∙4H2O was discussed in terms of molar Gibbs free energy change of reactions within the MgO-Al2O3-CO2-H2O system. The calculated formation Gibbs energy was negative, when Mg(OH)2 was formed as an intermediate product. The standard Gibbs free energies of hydrotalcite formation was estimated based on the simple mechanical mixture model that treats Mg6Al2CO3(OH)16∙4H2O as mixtures of simple oxides. Thermodynamic calculations were performed assuming an equilibrium state between aqueous solutions and corresponding precipitates after synthesis.

Pressure Oxidation of Arsenic (III) Ions in the H3AsO3-Fe2+-Cu2+-H2SO4 System

The processing of low-grade polymetallic materials, such as copper–zinc, copper–lead–zinc, and poor arsenic-containing copper concentrates using hydrometallurgical methods is becoming increasingly important due to the depletion of rich and easily extracted mineral resources, as well as due to the need to reduce harmful emissions from metallurgy, especially given the high content of arsenic in ores. Ferric arsenates obtained through hydrothermal precipitation are the least soluble and most stable form of arsenic, which is essential for its disposal. This paper describes the investigation of the oxidation kinetics of As (III) ions to As (V) which is required for efficient purification of the resulting solutions and precipitation of low-solubility ferric arsenates. The effect of temperature (160–200 °C), the initial concentration of Fe (II) (3.6–89.5 mmol/dm3), Cu (II) (6.3–62.9 of mmol/dm3) and the oxygen pressure (0.2–0.5 MPa) on the oxidation efficiency of As (III) to As (V) was studied. As (III) oxidation in H3AsO-Fe2+-Cu2+-H2SO4 and H3AsO-Fe2+-H2SO4 systems was controlled by a chemical reaction with the apparent activation energy (Ea (≈84.3–86.3 kJ/mol)). The increase in the concentration of Fe (II) ions and addition of an external catalyst (Cu (II) ions) both have a positive effect on the process. When Cu (II) ions are introduced into the solution, their catalytic effect is confirmed by a decrease in the partial orders, Fe (II) ions concentration from 0.43 to 0.20, and the oxygen pressure from 0.95 to 0.69. The revealed catalytic effect is associated with a positive effect of Cu (II) ions on the oxidation of Fe (II) to Fe (III) ions, which further participate in As (III) oxidation. The semi-empirical equations describing the reaction rate under the studied conditions are written.