Effect Of Hydrothermal Treatment Research Articles

Effect of hydrothermal treatment on Cr-SiO2 mesoporous materials

Cr/SiO2 (MCM-41) materials were prepared by the sol–gel method by hydrolysis of tetraethylortosilicate (TEOS) using cetyltrimethylammonium bromide (CTAB) as a template. The effect of hydrothermal treatment between 120–220°C on the structural properties was studied. Well ordered Cr/MCM-41 with a very narrow pore size distribution was obtained after hydrothermal treatment from RT to 150°C.Materials synthesized at higher temperatures (200 or 220°C) showed the collapse of the ordered mesoestructure to give mesoporous Cr/SiO2 with an open surface. Superficial Cr3+/Cr6+ ratio was determined by XPS over materials hydrothermically synthesized at different temperatures, and calcined in air at 300°C. The hydrothermal treatment improved the chromium to silica interaction, promoting a higher resistance to form Chromium (VI) sites. The chromium (III) ions incorporated to the silica structure developed acid sites responsible for the 2-PrOH dehydration.

Effect of Hydrothermal Treatment on the Piezoelectric Response of Oriented Barium Titanate Ceramics

The piezoelectric response of [11-oriented, fine-grained BaTiO3 ceramics was investigated. It was found that an exposure of the BaTiO3 compacts to high-pressure, high-temperature steam in an autoclave promoted the orientation of the sintered ceramics. As temperature in the autoclave increased, the orientation increased. A large small-field piezoelectric constant of d33 = 517 pC/N was observed for the oriented BaTiO3 ceramics with the grain size of 1.76 μm and the Lotgering factor of 85.3 %.

Sol-gel synthesis of titanum dioxide by hydrolysis of titanium glycerolates and peroxides

The sol-gel synthesis of titanium dioxide from titanium glycerolate (TG) and titanyl sulfate was studied. The effect of hydrothermal treatment in an autoclave at 130°C and refluxing TG with the peroxo titanium acid gel on the product properties, i.e., morphology of the nanoparticles and their aggregates, as well as their ability to adsorption and photocatalytic degradation of methylene blue in aqueous solutions was discussed.

Effect of hydrothermal treatment on the antioxidant activity of Sambaekcho (Saururus chinensis) leaves

Sambaekcho (Chinese lizard’s tail; Saururus chinensis) is one of widely used plants in oriental traditional medicine. Hydrothermal treatment of sambaekcho leaves was carried out at 3 different temperatures (100, 110, and 120°C) for 3 different times (15, 30, and 60 min), and antioxidant activities of the extracts were evaluated by determining total phenol content (TPC) and DPPH radical scavenging activity. The highest TPC and DPPH radical scavenging activity of the extracts were observed at 120°C for 30 min with the values of 61.25 mg gallic acid equivalents/g sambaekcho powder and 59.41%, respectively. The highest amount of quercetin, a well-known polyphenolic compound of sambaekcho, in the extracts was detected at 110oC for 60 min with the value of 3.13 μg/mL. These results indicated that appropriate temperature and time might be important for extraction with high antioxidant activity and physiologically important compounds from sambaekcho leaves.

Mechanochemical approach for synthesis of layered double hydroxides

In this paper, a mechanochemical approach is used to prepare layered double hydroxides (LDHs). This approach involves manually grinding the precursor, nitrates and then the hydrothermal treatment. The study indicates that grinding leads to the incomplete formation of LDHs phase, LDHs-M. The reaction degree of precursor salts to LDHs after grinding depends on the melting points of the precursors. As expected, hydrothermal treatment is beneficial for the good crystallization and regularity of LDHs. Especially, the effect of hydrothermal treatment has been emphatically explored. The hydration of LDHs-M, increment of zeta potentials and the complete exchange of NO3− by CO32− anions occur successively or in parallel during the hydrothermal treatment. It can be found that combination of grinding and hydrothermal treatment gives rise to the formation of uniform and monodispersed particles of LDHs.

Effect of hydrothermal treatment on physicochemical and digestibility properties of oat starch

The oat grain is often subjected to different hydrothermal treatments to inactivate hydrolytic enzymes that can have undesirable effects on the end-product quality. Hydrothermal treatments may affect the functional properties of oat starch. The objective of this work was to evaluate the effect of eight different hydrothermal treatments on the physicochemical and digestibility properties of oat starch. Hydrothermal treatments were selected based on heat treatment applications in oat industry and listed as HT-1) Ethanol boil HT-2) Ethanol boil and toasted HT-3) Steamed at 106°C HT-4) Steamed at 106°C and toasted HT-5) Covered autoclaved at 120°C HT-6) Uncovered autoclaved at 120°C HT-7) Covered autoclaved at 130°C and HT-8) Uncovered autoclaved at 130°C. The morphology of the oat starch was altered as a result of various heat treatments. HT-5 and HT-7 treatments had more large starch granules than the other samples, however the apparent molecular weight of the starch from these samples was unaffected by the treatment. HT-6 and HT-8 resulted in the most significant changes to the gelatinization properties of the oat starch. HT-6 oat sample had significantly (P<0.05) lower paste viscosity than starches from the oat samples with other treatments. The in vitro starch digestibility increased significantly (P<0.05) for the HT-6 and HT-8 oat samples. This study demonstrated that thermal treatments can cause reorganization of the amylose and amylopectin chains that can result in changes in their physicochemical and digestibility properties.

Effect of Hydrothermal Treatment of Activated Carbon by Nitric Acid on Activ-ity of Ba-Ru-K/AC Catalyst for Ammonia Synthesis

Effect of Hydrothermal Treatment of Activated Carbon by Nitric Acid on Activ-ity of Ba-Ru-K/AC Catalyst for Ammonia Synthesis

Effect of preparation conditions on the structural and acid catalytic properties of protonated titanate nanotubes

The effect of hydrothermal treatment on the morphological and acid catalytic properties of titanate nanomaterials was examined. Anatase nanoparticles were converted into titanate nanotubes and layered titanate nanorods according to the heating temperature used during the hydrothermal treatment. Fourier transform infrared (FT-IR) spectroscopy measurements and acid-base titrations revealed that all titanate nanomaterials possess Lewis acid sites, whereas Bronsted acid sites are formed after the hydrothermal treatment at temperatures higher than 323 K. At 423 K, titanate nanotubes with an inner diameter of 5 nm were formed, which exhibited the highest catalytic activity for the liquid phase Friedel–Crafts alkylation of aromatics with benzyl chloride or benzyl alcohol. The titanate nanorods prepared at 473 K exhibited Lewis acidity, but had no effective Bronsted acid sites regardless of the high ion-exchange capacity. The high catalytic performance of the titanate nanotubes can be attributed to the presence of a large number of both Lewis and Bronsted acid sites located on the surfaces of the nanotubes.

Effects of Hydrothermal Treatment on the Major Heavy Metals in Fly Ash from Municipal Solid Waste Incineration

Circulating fluidized bed (CFB) and stoker grate are the two major municipal solid waste incineration (MSWI) technologies currently being used in China. In this work, the hydrothermal stabilization...

Effects of Hydrothermal Treatment on the Structure and Properties of Aviation Polysulfide Sealant

An aviation polysulfide sealant has been soaked in a water bath at 85 °C to study the effects of hydrothermal treatment on this material. The morphology, Shore A hardness, and mechanical properties of the sealant were measured before and after soaking. The glass transition temperature (Tg) and room temperature storage modulus (E') were measured by means of a dynamic mechanical analyzer (DMA). The results showed that the surface glossiness of the polysulfide disappeared, some bubble defects appeared on its surface, the Shore A hardness and the tensile strength increased, while the elongation at break fluctuated with aging. The Tg and E' of the sealant changed only slightly. The chemical structure of the sealant was not obviously changed, and its aggregation state was changed only slightly, thus indicating that this sealant is characterized by good hydrothermal resistance.

Effects of Hydrothermal Treatment on Properties of Titanium Nitride Coating for Dental Implants

To improve surface hardness of dental implant made of pure titanium (Ti), titanium nitride (TiN) coating was introduced. However, studies revealed that TiN only showed osseointegration similar or inferior to that of Ti. Therefore it is necessary to improve the biocompatibility of TiN for dental implant coating. In the present study, TiN coating was prepared on pure Ti substrates and hydrothermal treatment was conducted to modify its surface properties. It was found that, TiN surface was partially oxidized after treatment and calcium (Ca) was successfully combined onto its surface. Surface morphology, roughness and hardness were not affected after treatments below 140°C and wettability was obviously improved.

Effect of Hydrothermal Treatment with Different Aqueous Solutions on the Mold Resistance of Moso Bamboo with Chemical and FTIR Analysis

Bamboo has received increased attention as a biomass material because it is fast growing and has good mechanical properties. But bamboo is very vulnerable to mold fungi, which greatly limits its applications. In this paper, bamboo was firstly hydrothermally treated at 140°C by three different treatments: with water only, NaOH, and NaAc aqueous solution, then heat treated at relatively mild conditions (180°C). Subsequently, the mold resistance of bamboo before and after the two-step heat treatment was investigated. The mechanism of mold resistance was analyzed by a bamboo chemical component analysis, FTIR spectroscopy. The results showed that strong degradation of hemicelluloses by heat treatment could inhibit mold growth to some extent. Moreover, the modification of lignin and the creation of phenolic compounds in the bamboo could prevent or slow down fungal growth.

Response Surface Modeling of Hydrothermal Treatment Conditions on Color Changes, Strength, and Durability Properties of Rubberwood

The effect of hydrothermal treatment at various temperatures (100 to 160 °C) and treatment times (30 to 720 minutes) on color changes (ΔE*), equilibrium moisture content (EMC), tensile strength (TS), shear strength (SS), brown-rot fungal decay mass loss (FML), and termite attack score (TAS) of rubberwood was examined. Response surface methodology (RSM) with a two-factor, four level (42) full factorial was employed. The mathematical models describing those properties as functions of treatment temperature and logarithm of treatment time were obtained. Hydrothermal treatment adversely and positively influenced mechanical properties (TS and SS) and durability (FML and TAS), respectively, of rubberwood. Strong correlations between ΔE*, TS, SS, and FML of hydrothermally treated rubberwood, proposed to be a consequence of degradation of hemicelluloses, were observed. Finally, ΔE* proved to be a good indicator of TS, SS, and FML but not that of EMC and TAS of hydrothermally treated rubberwood.

Functional and antioxidant properties of ready-to-eat flakes from various cereals including sorghum and millets

Introduction Nowadays, ready to eat snacks are gaining much importance, as they are convenient to use, easy to handle compared with ready-to-cook snacks. ObjectivesTo study the effects of cereal flaking and blistering process on the properties of the starch and nutraceutical content. Methods Ready-to-eat flakes from cereals such as maize grits, pearled barley, hulled oats, wheat, pearl millet and sorghum were prepared by hydration, hydrothermal treatment, flaking and blistering in a fluidized bed roaster. Commercial rice flakes were also considered. Results Grains hydrated slowly but flakes hydrated rapidly, indicating the effect of hydrothermal treatment where parboiling was imparted. Equilibrium moisture content on soaking was very high in barley (46%, wet basis) and lowest in maize grits and sorghum (approximately 30%). Swelling power in grains was 11‐17% and solubility was 8‐29%. On flaking, the swelling power of different flakes remained almost the same. However, the solubility increased significantly. Maize showed the highest amylose content (~29%) and wheat had the lowest. Soluble amylose was lowest in wheat and highest in oats. Gelatinization temperature was highest in pearl millet (77.4 °C) and lowest in barley (59.5 °C). Peak viscosity was high in all the grains, except pearl millet. On flaking and blistering, the gelatinization temperature values and peak viscosity reduced to different extents. Conclusion These blistered cereal flakes are excellent ready-to-eat snacks, as they are rich in total polyphenols (16-58 mg gallic acid equivalents/100 g) and exhibit high anti-oxidant activity and possess good functional properties.

Generation of Ultra-Clean Coal from Victorian Brown Coal: Effect of Hydrothermal Treatment and Particle Size on Coal Demineralization and the Extraction Kinetic of Individual Metals

This paper addressed the influences of hydrothermal treatment and particle size on the demineralization extent of Victorian brown coal for the generation of ultra-clean coal to burn directly in a gas turbine combined cycle. Extraction kinetics of individual metals have been investigated. The results for four different sizes of two Victorian brown coal samples showed that, for brown coal that is rich in the aluminum-/silicon-bearing mineral grains, its demineralization extent was dependent on coal particle size, showing the best result for the coal size of 150–300 μm. In contrast, the ash removal efficiency of brown coal rich in organically bound metals remained unaffected by particle size, substantiating a uniform distribution of ash-forming metals on the coal surface as a weak association with the oxygen-containing functional groups. The elution of most metals followed a pseudo-second-order with a confidence interval ≥90%. The activation energy and pre-exponential factor varied significantly with element...

Effect of hydrothermal treatment on the levels of selected indigenous microbes in food waste

The ability of hydrothermal treatment to reduce or eliminate selected indicator organisms in food waste was assessed in this study. Raw food waste collected from student canteens at Tsinghua University was heat-treated under hydrothermal conditions at 90-140 °C for 10-40 min. Hydrothermal inactivation analyses were carried out on four types of indigenous microbes used as indicators of hygiene: molds and yeasts (MY), total coliforms (TC), total aerobic counts (TAC) and Staphylococcus aureus (SA). Significant reductions in the levels of indigenous microbes in food waste were achieved during the ramping and holding periods of the hydrothermal treatment, and the microbial inactivation effect increased with increasing temperature, increasing time and increasing pressure. Due to the typical properties of food waste, hydrothermal treatment at 120 °C-0.3 MPa for at least 40 min was sufficient to achieve complete sterilization of the food waste. The results showed that hydrothermal treatment could significantly reduce the levels of indigenous microbes and is a potential advanced technique for the sterilization of food waste with a high moisture content in China.

Sol–gel titania coating on unmodified and surface-modified polyimide films

Sol–gel coating of metal oxides on polymer substrates is a useful process to fabricate various organic–inorganic hybrid materials under mild conditions. However, this process is hardly applicable to pristine polyimide (PI) films because their surfaces do not display effective functional groups for metal oxide coatings. In this study, we firstly examined direct sol–gel coating of titania thin layers on unmodified PI film surfaces. The results confirmed homogeneous, ultrathin titania layer coating and showed that the thickness and microscopic morphology of the titania layers were affected by titanium alkoxide concentrations in the spin coating solutions. We next investigated titania layer coating on surface-modified PI films that prepared using alkaline hydrolysis, which generated carboxylic acid groups on the film surfaces. Optimal hydrolysis time was determined using FT-IR spectroscopy and contact angle measurements. After sol–gel titania coating on the hydrolyzed PI film surfaces, the Scotch tape test was conducted to evaluate adhesion strength between the titania layers and PI film surfaces. Morphological observations of the sample surfaces after the tests clearly showed that surface modification of PI films increased titania layer adhesions. Effect of hydrothermal treatments on film formability and adhesion strength between titania-PI film interfaces was also evaluated.

Effects of hydrothermal aging on NH3-SCR reaction over Cu/zeolites

The effects of hydrothermal treatment on model Cu/zeolite catalysts were investigated to better understand the nature of Cu species for the selective catalytic reduction of NOx by NH3. After hydrothermal aging at 800°C for 16h, the NOx reduction performance of Cu-ZSM-5 and Cu-beta was significantly reduced at low temperatures, while that of Cu-SSZ-13 was not affected. When the zeolite framework aluminum species were probed using solid state 27Al MASNMR, significant reduction in the intensities of the tetrahedral aluminum peak intensity was observed for Cu-ZSM-5 and Cu-beta, although no increase in the intensities of the octahedral aluminum peak was detected. When the redox behavior of Cu species was examined using H2-TPR, it was found that Cu2+ could be reduced to Cu+ and to Cu0 for Cu-ZSM-5 and Cu-beta catalysts, while Cu2+ could be reduced only to Cu+ in Cu-SSZ-13. After hydrothermal aging, CuO and Cu-aluminate species were found to form in Cu-ZSM-5 and Cu-beta, while little changes were observed for Cu-SSZ-13.

Effects of hydrothermal treatment on the properties of nanoapatite crystals

We report the synthesis of nanoapatite crystals via a hydrothermal reaction of hydroxyapatite precipitates. The impact of the reaction conditions on the properties of the crystals obtained were evaluated. The hydrothermal reaction that takes place markedly affected the crystallinity, morphology, and size of the nanoapatite crystals formed. High crystallinity and large crystal size were obtained at higher hydrothermal temperatures and longer hydrothermal reaction times. The nanoapatite crystals were needle-like when prepared under ambient pressure conditions and rod-like when prepared under increased pressure. The crystals prepared at ambient pressure had a larger aspect ratio compared with those prepared under increased pressure. The aging time of the initial hydroxyapatite precipitate significantly affected growth of the nanoapatite crystals. With other hydrothermal reaction conditions being equal, the fresh hydroxyapatite precipitate produced notably larger crystals than the aged hydroxyapatite precipitate. The influence of apatite morphology on osteoblast viability was studied by MTT assay. The results indicate that the rod-like apatite showed a better biological response than needle-like apatite in promoting cell growth. Transmission electron microscopy showed that large quantities of needle apatite entered into cells and damaged their morphology.

Hydrothermal Carbon from Biomass: Structural Differences between Hydrothermal and Pyrolyzed Carbons via 13C Solid State NMR

The objective of this paper is to better describe the structure of the hydrothermal carbon (HTC) process and put it in relationship with the more classical pyrolytic carbons. Indeed, despite the low energetic impact and the number of applications described so far for HTC, very little is known about the structure, reaction mechanism, and the way these materials relate to coals. Are HTC and calcination processes equivalent? Are the structures of the processed materials related to each other in any way? Which is the extent of polyaromatic hydrocarbons (PAH) inside HTC? In this work, the effect of hydrothermal treatment and pyrolysis are compared on glucose, a good model carbohydrate; a detailed single-quantum double-quantum (SQ-DQ) solid state (13)C NMR study of the HTC and calcined HTC is used to interpret the spectral region corresponding to the signal of furanic and arene groups. These data are compared to the spectroscopic signatures of calcined glucose, starch, and xylose. A semiquantitative analysis of the (13)C NMR spectra provides an estimation of the furanic-to-arene ratio which varies from 1:1 to 4:1 according to the processing conditions and carbohydrate employed. In addition, we formulate some hypothesis, validated by DFT (density functional theory) modeling associated with (13)C NMR chemical shifts calculations, about the possible furan-rich structural intermediates that occur in the coalification process leading to condensed polyaromatic structures. In combination with a broad parallel study on the HTC processing conditions effect on glucose, cellulose, and raw biomass (Falco, C.; Baccile, N.; Titirici, M.-M. Green Chem., 2011, DOI: 10.1039/C1GC15742F), we propose a broad reaction scheme and in which we show that, through HTC, it is possible to tune the furan-to-arene ratio composing the aromatic core of the produced HTC carbons, which is not possible if calcination is used alone, in the temperature range below 350 °C.