Hydrothermal Vessel Research Articles

Preparation and photocatalytic degradation of methylene blue dye under LED light for porous and non-porous Cu balls

Porous and non-porous Cu (P-Cu and NP-Cu, respectively) balls were prepared using a Cu2+ precursor with N2H4∙H2O, a reducing agent, in a hydrothermal vessel and a three-necked flask, with mechanical stirring, respectively. The morphologies of the P-Cu and NP-Cu balls were investigated through scanning electron microscopic images. The photocatalytic activity of the P-Cu and NP-Cu balls and commercial Cu foils under a white light-emitting diode was evaluated by monitoring the photodecolorization of a dye, methylene blue, in aqueous solution.

Growth of specific geometries such as cubes of In2S3 for PEC water splitting by hydrothermal technique

Green fuel hydrogen generation by photoelectric water splitting is one of the best techniques. The chemical route is chosen for achieving good and sustained photocurrent values for distinct nanocubes of di-indium sulfide (In2S3). Nanocomposites with majority of nanocubes of In2S3 were synthesized on the ITO glass in a hydrothermal vessel with hydrated InCl3 and thiourea as initial precursors at 120 °C for 12 h. Raman and XRD analysis has shown the formation of the cubic phase of β-In2S3. FESEM and HRTEM analysis showed highly crystalline nanocubes with an average size of 1 μm. The photocurrent density reached value 0.28 mA/cm2 at 1 V Ag/AgCl under the irradiation of 100 mW/cm2 without specific agent.

Simultaneous growth of graphene/mesoporous silica composites using liquid precursor for HPLC separations

Silica intercalated graphene-silica composites (G/SiO2) were prepared by one-step hydrothermal method. In the previously reported one-step method for synthesizing G/SiO2 composites (eg. Bull. Mater. Sci., 37 (2014), 589–595; Applied Surface Science 259 (2012), 566–573), graphene needs to be synthesized first and then used to prepare G/SiO2 composites. In this work, neither the preparation of graphene nor the use of graphite as a carbon source is required for the preparation of G/SiO2 composites. Instead, organic solvent (such as toluene, xylene, mesitylene, n-hexane, n-heptane, and cyclohexane) was directly used as the carbon source, and the growth and recombination of graphene and SiO2 were achieved simultaneously through a one-step hydrothermal method. In a hydrothermal reaction vessel, the mixture consisting of organic solvent, TEOS, H2O, and surfactant was uniformly stirred, and then reacted at 160 °C for 4 h to prepare G/SiO2 composite. The influence of the type of organic solvent, hydrothermal reaction temperature, and calcination temperature on the structure of G/SiO2 composites were studied. The morphology and structure of G/SiO2 composites were characterized by FESEM, TEM, and Raman. The formation mechanism of G/SiO2 composite was proposed. G/SiO2 composite was then grown directly on the SiO2 spheres and used as stationary phase for high performance liquid chromatograph separation. Mixture of hydrocarbons was well separated under reversed phase condition.

Hydrothermal Synthesis of Copper (II) Oxide Microparticle

CuO microparticle was syntheszied by hydrothermal method. The starting precursors were used as copper (II) nitrate trihydrate (Cu (NO3)2·3H2O), nitric acid (HNO3) and sodium hydroxide (NaOH). The final pH value of the mixed solution was used 2M NaOH to adjust the pH was 8 and treated at 100-200 oC for 4-6 h in a hydrothermal vessel. The black fine powder was obtained after dried at 100 oC for 5 h. The phase and structure of CuO microparticle were characterized by X-ray diffraction (XRD). A single phase monoclinic structure synthezied by hydrothermal method at 200 oC for 4 and 6 h was obtained without calcination steps. The morphology CuO microparticle was investigated by scanning electron microscopy (SEM). It was likely grain in shape and the particle size in range of 2.94-4.06 μm. The element composition of CuO microparticle was indicated by energy dispersive X-ray spectrometry (EDX). The chemical compositions showed the characteristic X-ray energy of copper (Kα = 0.98 keV) and oxygen (Kα = 0.53 keV), respectively. The functional group of CuO microparticle was indentified by Fourier transform spectrophotometry (FTIR). The wavenumber at 690, 514 and 437 cm-1 was corresponded to vibration of Cu-O stretching.

Nitrogen gas interaction on silica aerogel – Effects on hydrophobicity, surface area, porosity, and lithium-ion battery performance

The present study evaluates in-situ pressurized nitrogen gas (N2) purging effect on tuning hydrophobicity of silica aerogel, and the effect on lithium-ion battery applications. The mesoporous silica aerogels are prepared using sol-gel process, followed by supercritical drying with ethanol solvent extraction, and dry nitrogen gas is pressurized and purged to remove the condensed ethanol vapor from the hydrothermal vessel. The pressurized nitrogen gas molecules interact with silica aerogel at 255 °C and remove surface reactive OH groups and increase the surface roughness and hydrophobicity, which is evident from the reduction of Si-OH infrared vibration bands, porous electron microscopic images and increased contact angle. It also increases the surface area, compresses the pores, and carbonizes the organics, which is confirmed from surface area measurements and quantitative X-ray photoelectron spectroscopy analysis. Also, the powder X-ray diffraction patterns confirm the amorphous nature of silica aerogel. The Li-ion battery performance of the obtained amorphous silica aerogel is examined using cyclic voltammogram and charge-discharge studies. The present study enumerates that apart from surface area and in-situ carbon, the pore size is also an important criterion in maintaining better battery performance.

Gold partitioning between 1-dodecanethiol and brine at elevated temperatures: Implications of Au transport in hydrocarbons for oil-brine ore systems

Gold can be associated with hydrocarbons in hydrothermal gold deposits, but the near-absence of experimental data on gold-hydrocarbon interactions at hydrothermal conditions prevents a quantitative interpretation of this relationship. In this study, we investigate the ability of liquid hydrocarbons to act as gold-transporting ore fluids using experiments on the partitioning of gold between brine (10 wt% NaCl) and 1-dodecanethiol (DDT). Experiments were conducted at 105 °C and 150 °C and <5 bar in a hydrothermal flow-through vessel. Partition coefficients (DAuorg/aq) obtained from the 105 °C and 150 °C experiments range from 10 ± 3.0 to 91 ± 30 at 105 °C and from 4.9 ± 0.9 to 33 ± 6.9 at 150 °C, with averages of 37 ± 33 and 21 ± 12, respectively. Gold concentrations in both the brine (<1 ppm) and DDT (up to 10 ppm) are dependent on the initial bulk concentration of gold (up to 4 ppm) and on the Au loss to the vessel walls during the experiment, as the Au concentrations correlate linearly with Au loss, while DAuorg/aq appears independent of bulk composition and Au loss. This linear dependency results in a stronger Au loss from the oil that bears more Au (DDT), and enables the calculation of DAuorg/aq for zero Au loss, which is 19 ± 21. These findings indicate that DAuorg/aq is a constant at the P-T-X conditions investigated. While these experiments did not directly assess Au solubility in DDT, no indication of Au saturation was observed, suggesting that higher concentrations are possible. The pH of the brine decreases during the experiments, indicating that the DDT underwent deprotonation and possibly decomposition during the partitioning reaction, but the pH does not have an observable effect on the gold concentrations in the brine and DDT. Preferential partitioning of gold into DDT is attributed to bonding with the thiol group, and as thiols compose up to 7 wt% of the total organic sulfur content of crude oils, liquid hydrocarbons have the potential to transport significant amounts of gold in ore formation processes. This is of importance for ore systems forming at relatively low temperatures and ore deposits known to be associated with organic matter such as Carlin type Au deposits.

One-step hydrothermal synthesis of yttria-stabilized tetragonal zirconia polycrystalline nanopowders for blue-colored zirconia-cobalt aluminate spinel composite ceramics

A novel approach for the preparation of blue-color giving zirconia nanopowders by doping of 3 mol% Y2O3 through simple one-step hydrothermal process is proposed. A blue-color giving yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) powders were prepared by urea-based solution, zirconium acetate, CoCl2·6H2O and AlCl3 precursors in hydrothermal vessel at 24 h, 150 °C and 20 bars. Based on the results, the synthesized blue-color giving Y-TZP nanopowders have entirely tetragonal structure as mono phase with 3.8 ± 0.2 nm average grain size and (Y, Co, Al)xZrO2; x ≤ 0.03 at. with chemical composition. Thermal treatment was also applied to synthesized Y-TZP powders at 1200 °C and 1450 °C to observe the color evolution. Only sharp blue was obtained in Y-TZP powders resulting the development of zirconia-cobalt aluminate spinel (ZrO2-CoAl2O4) composite ceramic structure for both temperatures after heat-treatment. Herein, not only formation of CoAl2O4 but also incorporation of cobalt (Co) and aluminum (Al) into the Y-TZP grains plays a critical role on evolving of blue color. This synthesized Y-TZP nanopowders can be a good candidate for one-step production of blue-color sintered ZrO2-CoAl2O4 spinel composite ceramics in numerous ceramic applications due to their superior structural and functional properties.

Metasomatic Replacement of Albite in Nature and Experiments

Replacement of albite by sodium-rich, secondary phases is a common phenomenon, observed in different geological settings and commonly attributed to alkaline metasomatism. We investigated growth of nepheline and sodalite on albite in time series experiments between two and 14 days. A total of 42 hydrothermal experiments were performed in cold-seal hydrothermal vessels at a constant pressure of 4 kbar and 200–800 °C in the system SiO2–Al2O3–NaCl–H2O. To allow for fluid flow and material transport, a double-capsule technique was used; hereby, a perforated inner Pt capsule was filled with cleavage fragments of natural albite, whereas the shut outer Au capsule was filled with γ-Al2O3 and the NaCl–H2O solution. Complete overgrowth of albite by sodalite and nepheline occurred after just two days of experiments. At high salinity (≥17 wt % NaCl) sodalite is the stable reaction product over the whole temperature range whereas nepheline occurs at a lower relative bulk salinity than sodalite and is restricted to a high temperature of ≥700 °C. The transformation of albite starts along its grain margins, cracks or twin lamellae. Along the reaction front sodalite crystallizes as small euhedral and highly porous grains forming polycrystalline aggregates. Coarse sodalite dominates in the outermost domains of the reaction zones, suggesting recrystallization. Sodalite may contain fluid inclusions with trapped NaCl-rich brine, demonstrating that the interconnected microporosity provides excellent pathways for fluid-assisted material transport. Highly porous nepheline forms large, euhedral crystals with rectangular outline. Sodalite and nepheline in natural rock samples display only minor porosity but fluid and secondary mineral inclusions, pointing to coarsening of a previously present microporosity. The reaction interface between sodalite and albite in natural rock samples is marked by open channels in transmission electron microscopy. In many of the experiments, a zone of Si–H-rich, amorphous material is developed at the reaction front, which occurs at a temperature of up to of 750 °C as nanometer to 350 µm wide reaction zone around albite. This change in composition corresponds with the abrupt termination of the crystalline feldspar structure. The presence of sodalite as micro- to nanometer-sized, euhedral crystals within the amorphous zone demonstrates, that both the sodalite reaction rim and the amorphous material allow for fluid-assisted material transport between the crystalline albite (release of Si, Al) and the bulk fluid (H2O, Na, Cl). This texture, moreover, suggests that the amorphous phase represents a metastable interstage reaction product, which is progressively replaced by sodalite and nepheline. Remarkably, product sodalite, nepheline, and the amorphous material largely inherit the trace element budget of the respective ancestor albite, indicating that at least part of the trace elements remained fixed during the reaction process. The observed reaction textures in both natural and experimental samples indicate an interfacial dissolution–reprecipitation mechanism. Results of our study bear important implications with respect to mineral replacement in the presence of a fluid phase, especially regarding the interpretation of trace element patterns of the product phases.

Investigation of Polymorphism and Vibrational Properties of MnMoO4Microcrystals Prepared by a Hydrothermal Process

MnMoO4 microcrystals were synthesized by hydrothermal methods, and their structural, morphological, and vibrational properties were investigated. Conventional reactors and microwave-heated hydrothermal vessels were used to synthesize micrometer-sized MnMoO4 polymorphs at different temperature and time conditions. MnMoO4·H2O crystals were obtained in both reactors at temperatures below 200 °C, for times up to 24 h. These microcrystals belong to the triclinic P1 space group, and their 26 characteristic Raman bands were identified. A monoclinic MnMoO4 polymorph belonging to the P2/c structure was synthesized at temperatures higher than 200 °C only into conventional hydrothermal reactors. Polarized micro-Raman analyses have evidenced and allowed the assignment of 18 phonon modes predicted by group-theory calculations for this polymorph. Another MnMoO4 polymorph, within the monoclinic C2/m space group, was obtained by two processing routes: (i) heating the P2/c microcrystals at 600 °C; or (ii) heating the MnM...

Direct hydrothermal synthesis of hydroxyapatite/alumina nanocomposite

Hydrothermal synthesis offers numerous advantages such as: control over product homogeneity, nucleation, growth and aging. This leads to the control of particle aggregation, size uniformity and morphology over conventional and non-conventional ceramic synthesis methods. In the present work, a novel procedure for the direct synthesis of Hydroxyapatite (HAp)/alumina nanocomposite in a hydrothermal vessel with continuous stirring was investigated, where the effects of different concentration of aluminium nitrate were also studied. The optimized concentration of starting material for the characteristic formation of HAp/alumina composite (hexagonal HAp and monoclinic alumina phases) was determined by X-ray diffraction (XRD) study. The size distribution of HAp/alumina composite was found as 100nm by electron microscopy and EDAX revealed that the concentration of alumina in the HA4 was ~10%, which is more suitable for biomedical implant. Further, the cytotoxicity study against MG 63 cells showed that HA4 was biocompatible even at higher concentration (200μg/ml). Hence, the direct synthesis of HAp/alumina composite without the formation of any intermediate like calcium aluminate could be used as a novel approach to prepare HAp based biomedical implants.

Nucleation and Growth Mechanism of Barium Titanate Nanoblocks in Hydrothermal Process Using Aqueous Titanium Compound

Barium titanate (BT) nanoblocks were synthesized by using aqueous sources of barium and titanium. To analyze the growth mechanism of nanoblocks, a kind of sampling hydrothermal vessel was employed to timely observe the reaction of precursor solution. During the nucleation and ripening process, intermediate of nanoblocks were taken out directly from reacting solution to analyze. BT nuclei grew directly in the Ti-based gel through an in situ growth mechanism. An oriented attachment phenomenon could be observed among neighboring nuclei. The Ostwald ripening process played a role in the growth of monodispersed BT nanoblocks. Diversified surface morphology of intermediate nanocrystals indicates that the chelating effect of oleate anions is unequal for all of the {100} crystal facets. After 24 h, agglomeration of nanoblocks occurred in Ti gel and formed BT meso-clusters with highly crystalline structure. The kinetics of the BT cluster was related with the oriented attachment mechanism. Nanoblocks overlapped wit...

Domestic pressure cooker as inexpensive hydrothermal vessel: Demonstrated utility for eco-friendly synthesis of non-toxic carbon dots

We report on a simple and eco-friendly approach that employs a domestic pressure cooker as an inexpensive hydrothermal reactor for the batch synthesis of water-soluble, photoluminescent nanoscale carbon dots derived from benign and cheap commercial starting materials. The resulting carbon nanodots, which consist primarily of hydrophile-decorated amorphous carbon and boast bright, stable, excitation wavelength-dependent fluorescence, were shown to be viable cellular imaging agents for mice embryonic fibroblast cells, displaying little or no cytotoxicity for carbon dot concentrations up to 0.667 mg/mL. In addition, the carbon dots proved useful as nanoprobes for the fluorescence-based detection of environmentally-relevant heavy metal ions such as Cu2+, displaying detection limits below 6μM, sufficient to determine potable water safety (20μM is the limit for safe drinking water set by the U.S. Environmental Protection Agency). More generally, these results highlight the utility of a household pressure cooker as a cost-effective hydrothermal vessel relevant to nanocarbon synthesis, opening up other possibilities for nanosynthesis, particularly in resource-limited settings, educational venues, and the classroom itself.

Hydrothermally Synthesized Strontium Peroxyapatite

The current research focuses on peroxide ion incorporation in the structure of strontium hydroxyapatite (SrHAp) by exposure to H2O2 ina closed hydrothermal vessel under mild conditions at 130 to 170 °C. Peroxide enriched strontium apatite (SrPerAp) was characterized for structure by X-Ray diffraction, for peroxide content- by permanganometric titration and then viewed by SEM. This study continued from previous work that used 30%H2O2 and showed a higher included peroxide content after processing with 50% H2O2 at 130 °C 70% of the theoretical peroxide content in apatitic channels of strontium apatite. This is the highest peroxide content incorporated to date and employs a lower temperature than heating at 1300 °C.

An experimental investigation of the role of microfracture surfaces in controlling quartz precipitation rate: Applications to fault zone diagenesis

We present the results of quartz growth experiments, which were designed to assess the role of microfracture surfaces in controlling quartz-precipitation rates during fault-zone diagenesis. Experiments were run in hydrothermal cold-seal vessels at 300–450 °C and 150 MPa confining pressure for up to 1344 h. Microfractures routinely form at grain contacts during these experiments. Microfracture kinematic-aperture distributions indicate that microfractures form within the first 48 h of each experiment. Regardless of experimental temperature or duration, microfracture-sealing cements account for approximately the same amount of new quartz cement in each experiment. With increasing experimental duration, sealed microfractures were progressively overgrown by grain-boundary overgrowth cements. Spatial and temporal trends in the distribution of overgrowth- and microfracture-sealing cements indicate that precipitation rates on newly formed microfractures greatly exceed those on detrital-grain boundaries. This effect persists regardless of natural iron-oxide grain coatings present in a subset of our experiments. While our results agree with previous research that demonstrated increased growth rates on fracture surfaces in faults in fully lithified rock, fundamental differences in the nature of deformation in our experiments provide insight into quartz cementation in cataclastic deformation bands in faults offsetting high-porosity sandstones.

Experimental Constraints on Dacite Pre-eruptive Magma Storage Conditions beneath Uturuncu Volcano

Cerro Uturuncu is a long-dormant, compositionally monotonous, effusive dacitic volcano in the Altiplano–Puna Volcanic Complex (APVC) of SW Bolivia. The volcano recently gained attention following the discovery of an ∼70 km diameter Interferometric Synthetic Aperture Radar (InSAR) anomaly roughly centred on its edifice. Uturuncu dacites, erupted over the past ∼1 Myr, invariably have a phase assemblage of plagioclase–orthopyroxene–biotite–ilmenite–magnetite–apatite–zircon and rhyolite glass. To better constrain storage conditions of the dacite magmas and to help understand their relationship with the observed deformation, petrological experiments were performed in cold-seal hydrothermal vessels. Volatile-saturated (PH2O = PTOTAL and PH2O + PCO2 = PTOTAL) phase equilibria experiments were run between 50 and 250 MPa and 760 and 900°C at fO2 ∼ Ni–NiO. Two synthetic starting compositions were investigated based on a typical Uturuncu dacite whole-rock and its rhyolitic groundmass glass. Pre-eruptive magma storage conditions have been estimated by comparing results from the experiments with natural phase assemblages, modes, and mineral and glass compositions. H2O-saturated experiments constrain storage pressures to 100 ± 50 MPa, equivalent to 1·9–5·7 km below surface. In the dacite, natural phase assemblages are reproduced at 870°C, 100 MPa with both orthopyroxene and biotite stabilized concurrently. Natural glass chemistries are most closely replicated at 50 MPa at 870°C, reflecting the role of decompression crystallization prior to eruption. In H2O-saturated rhyolite experiments the natural phase assemblage is most closely replicated at 870°C, 50 MPa. Isothermal, mixed volatile dacite experiments at 870°C further constrain storage pressures to 110 ± 10 MPa. Assuming that there has been no dramatic change in the eruptive behaviour of Uturuncu in the last 270 kyr, pre-eruptive storage of dacite magmas at ∼100 MPa precludes their role in producing the large diameter deformation anomaly. If deformation is a result of magmatic intrusion, then intrusion of less evolved magmas into deeper, mid-crustal storage regions is a more probable explanation. Intrusion within the Altiplano–Puna Magma Body (APMB), the extent of which is roughly coincident with the APVC, is most likely. It is proposed that dacite magmas form from andesitic parents, via fractionation and/or assimilation, within the APMB. Dacites then rise buoyantly to shallow storage levels where they stall and crystallize prior to eruption. Microlites form during subsequent ascent from the storage region to the surface.

H$_{\bm 2}$O $_{\bm 2}$-Aided One-Pot Hydrothermal Synthesis of Nanocrystalline LiMn$_{\bm 2}$O$_{\bm 4}$ Cathode for Lithium Batteries

A simple and H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -aided hydrothermal (HDT) method has been deployed to synthesize nanocrystalline LiMn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> at 140°C using an in-house-made hydrothermal reaction vessel. Phase pure, highly crystalline, and uniformly distributed nanorods of 100 nm length are obtained from the H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> aided exothermic oxidation of precursor mix, especially when an excess amount of lithium (Li: Mn as 2:1) is used. The crystalline nature of LiMn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> and the growth of nanorods along (111) crystallographic direction are understood from powder x-ray diffraction (PXRD) and selective area electron diffraction (SAED) analysis, respectively. The synthesized cathode exhibited an initial capacity of 118 mAh g <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> with a slightly higher initial capacity fade (9%) and a progressively stabilized (<; 3% capacity fade) specific capacity behavior upon cycling. An equivalent circuit model is proposed to fit with the observed impedance behavior of LiMn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> cathode. The exploitation of low temperature assisted one-pot hydrothermal synthesis to prepare nanocrystalline LiMn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> compound and the suitability of the same to exhibit better lithium intercalation behavior are demonstrated in this communication.

Effect of alkalis on the Fe oxidation state and local environment in peralkaline rhyolitic glasses

Iron oxidation state and coordination geometry have been determined by Fe K-edge X-ray absorption near edge spectroscopy (XANES) for three sets of silicate glasses of peralkaline rhyolitic composition with different peralkalinity values. These compositions were chosen to investigate the effect of alkali content (and oxygen fugacity) on the Fe oxidation state. The samples were produced by means of hydrothermal vessels at 800 °C with oxygen fugacity conditions ranging from NNO-1.61 to NNO+2.96 log units.

Fluid Flows in an Industry Hydrothermal Autoclave with Seed Crystals and Raw Lascas

The fluid flows in hydrothermal growth vessels have significant effects on growth quality. This article presents a numerical investigation on the fluid flow and heat transfer in an industry hydrothermal autoclave. The focus is on the modeling of the seed crystals in the growth chamber, the raw lascas in the dissolving chamber, and their effects on the turbulent flows. The fluid and heat transport processes in the autoclave at representative stages of a growth run are simulated. Results show that the growth chamber has one flow cell at the beginning and another flow cell is developed later in a growth run. The dissolving chamber has a cell flow in the fluid region. A wall layer and core flow structure is established in the raw material region which carries significant heat transfer resistance. The transport through the baffle opening is between two flow cells. The fluid transport processes varies, and the thermal environment in the growth chamber changes significantly as the raw material bed is dissolved and the seed crystals grow.

Photocatalytic Degradation of Geosmin by Titanium Dioxide Powder Synthesized by the Hydrothermal Route

Titanium dioxide powder was synthesized by the hydrothermal route with the starting precursors as titanium isopropoxide, ammonium hydroxide and nitric acid. The final of pH value of mixed solution was 1 and treated in the hydrothermal PTFE vessel at 80-100 °C for 3h. The phase of titanium dioxide was characterized by X-ray diffractometer (XRD). The morphology of titanium dioxide was investigated by scanning electron microscope (SEM). The chemical composition of titanium dioxide was examined by energy dispersive X-ray spectrophotometer (EDXS). The photocatalytic degradation of geosmin by titanium dioxide was determined by gas chromatograph coupled with flame ionization detector (GC-FID).

Catalytic hydrolysis of waste nylon 6 to produce ɛ-caprolactam in sub-critical water

The wide use of nylon 6 (PA 6) resulting in the resource recovery of waste PA 6 is urgent and its hydrolysis in sub-critical water to produce ɛ-caprolactam is a very important method. Hydrothermal diamond anvil cell (HDAC) was used to in situ observe transformation of PA 6 in water up to 513 K. The result shows that PA 6 melts at 488 K, and then hydrolyzes to produce low molecular dissoluble compounds such as 6-aminocaproic acid and ɛ-caprolactam from cleavage of acyl–amido bond. Different from the microreactor (about 0.075 μl) of HDAC, degradation of PA 6 in hydrothermal vessel of 18 ml is far slow, so the higher temperatures of 553, 573, 583, and 603 K are tried. As for hydrothermal vessel runs, liquid products after degradation are mainly composed of ɛ-caprolactam. Phosphotungstic heteropoly acid (HPA) as catalyst can improve hydrolysis rate and yield of ɛ-caprolactam, and 3% HPA can attain preferable effect. The optimum hydrolysis conditions for ɛ-caprolactam are as follows: HPA amount is 3%, reaction temperature is 573 K and reaction time is 85 min, and the yield of ɛ-caprolactam is 77.96%. In the temperature range of 553–603 K, the non-catalytic and catalytic degradation kinetics are studied as pseudo-first-order reaction and apparent activation energy is 86.64 and 77.38 kJ/mol for no catalyst and 3% HPA, respectively.