Acid Hydrothermal Method Research Articles

Synthesis of spherical amine-functionalized silica molecular sieve and application as selective adsorbents for aromatic hydrocarbons analysis

In this work, spherical amine-functionalized mesoporous silica (Sp-Amino-Si) molecular sieve was fabricated by an acid hydrothermal method using 3-aminopropyltriethoxysilane as a modifier and toluene as the solvent. The results of scanning electron microscopy, Barrett-Joyner-Halenda pore size distribution, Fourier transform-infrared spectroscopy, and low-angle X-ray diffraction patterns revealed that the Sp-Amino-Si was monodispersed microspheres with uniform and controllable pore sizes sharing two-dimensional hexagonal P6mm symmetry and a large number of amino groups. The Sp-Amino-Si molecular sieve was verified to be suitable for the selective separation of aromatic hydrocarbons (AMHs) containing two fused benzene rings among other compounds from environmental water matrix. Under the optimized conditions, the Sp-Amino-Si exhibited much higher adsorption efficiency for AMHs (above 88.19%), comparing to the original SBA-15 (below 44.52%). The maximum adsorption capacities for naphthalene, methyl naphthalene, 2-methyl naphthalene, and acenaphthene were 477.1, 1006.5, 893.3, and 1253.2 µg·g−1, respectively. The high selectivity of Sp-Amino-Si for the four AMHs attributed to the size sieving and p-π interactions between the lone pair electrons of amine groups and the π-electrons in AMHs molecules. The Sp-Amino-Si based solid-phase extraction coupled with high performance liquid chromatography detection method was constructed for the analysis of the four AMHs, and the recoveries of spiked AMHs ranged from 89.67% to 112.74% with a relative standard deviation lower than 5.75%. This study provides some inspiration and a reliable method for AMHs separation, removal, and analysis.

Improvement in energy recovery from Chlorella sp. biomass by integrated dark-photo biohydrogen production and dark fermentation-anaerobic digestion processes

Chlorella sp. biomass was used as the sole substrate for the production of hydrogen and methane through integrated dark fermentation (DF) and photo-fermentation (PF), and DF and anaerobic digestion (AD) processes. Prior to use in fermentations, the biomass was pretreated by acid-hydrothermal method, which yielded a maximum reducing sugar yield of 162.9 ± 4.2 mg g-biomass−1. The use of the microalgal hydrolysate to produce hydrogen by DF gave a hydrogen yield (HY) of 47.2 ± 1.1 mL g-volatile-solids−1 (VS). The subsequent use of the hydrogenic effluent in PF gave a HY of 125.0 ± 1.5 mL g-VS−1, while AD of the hydrogenic effluent gave a methane yield of 152.8 ± 1.3 mL g-VS−1. The total energy yield attained by the use of DF alone, the integrated DF-PF, and DF-AD processes were 0.51, 1.86 and 5.98 kJ g-VS−1, respectively. These results indicate that the integrated DF-AD process was effective in recovering energy from Chlorella sp. biomass. However, an energy balance analysis indicated that the process was not energetically feasible due to the high energy demand for the acid-hydrothermal pretreatment.

One-Step Acidic Hydrothermal Preparation of Dendritic Rutile TiO₂ Nanorods for Photocatalytic Performance.

Three-dimensional and dendritic rutile TiO2 nanorods were successfully fabricated on a Ti foil surface using a one-step acidic hydrothermal method. The TiO2 nanorods were characterized using X-ray diffraction (XRD), energy dispersive X-ray spectrometry (EDX), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and optical contact angle testing. The results showed that the nanorods with diameters of 100–500 nm and lengths of 100 nm to 1 μm were obtained on the Ti foil surface. The length and density of the TiO2 nanorods were perfect at the conditions of HCl concentration 0.5 mol/L, temperature 220 °C, and reaction time 12 h. The TiO2 nanorods formed parallel to the consumption of Ti and grew along the (110) direction having a tetragonal rutile crystal. The morphology of the nanorods possessed a three-dimensional structure. The contact angle of the nanorods was only 13 ± 3.1°. Meanwhile, the photocatalytic activities of the TiO2 nanorods were carried out using ultraviolet fluorescence spectrophotometry for the methyl orange detection, and the degradation was found to be about 71.00% ± 2.43%. Thus, TiO2 nanorods can be developed by a one-step acidic hydrothermal method using Ti foil simultaneously as the substrate with a TiO2 source; the TiO2 nanorods exhibited photocatalytic performance while being environment-friendly.

The effect of phosphate modification on the photocatalytic H2O2 production ability of g-C3N4 catalyst prepared via acid-hydrothermal post-treatment

Protonation of graphitic carbon nitride (g-C3N4) based catalyst by acid treatment is proved to benefit for its photocatalytic performance. However, acid-hydrothermal method to synthesize g-C3N4 was seldom reported. In this work, phosphate-modified g-C3N4 as efficient photocatalyst for H2O2 production was prepared via acid-hydrothermal method. XRD, N2 adsorption, UV–Vis, FT-IR, SEM, XPS, TPD, EIS, and PL were used to characterize the obtained catalysts. Phosphate modification not only influences the morphology, structure property and optical property, but also promotes the O2 adsorption ability, leading to the improved separation rate of electrons-holes. Phosphate modified g-C3N4 catalyst shows the H2O2 concentration of 5.4 mmol L−1, more than 13.5 times higher than that of neat g-C3N4. The possible reaction mechanism is proposed.

Carbonized polydopamine wrapping layered KNb3O8 nanoflakes based on alkaline hydrothermal for enhanced and discrepant lithium storage

Although the photochemical and ion exchange properties of layered KNb3O8 (KN) have been extensively studied, its potential lithium storage applications were ignored. Unlike typical acid hydrothermal method, this work demonstrate that interlayer-controlled KN nanoflakes can be prepared based on alkaline hydrothermal conditions. Pristine KN performs a high first-discharge capacity and superior cyclic stability. Moreover, polydopamine derived carbon as a conductive coating shell was firstly applied to modify KN for enhancing its lithium insertion ability. It performs outstanding rate character (310, 255, 110 mA h g−1 at the current density of 0.2, 1, 10 A g−1, respectively), as compared with pristine KN (96, 51, 13 mA h g−1). It also shows excellent long-term cycling feature (209 mA h g−1 after 3000 cycles, corresponds to 95% capacity retention). In addition, relevant energy storage mechanisms have been expounded. The present work could be helpful in developing potential multifunctional applications of KN-based and other similar niobates.

Acidic hydrothermal treatment: Characteristics of organic, nitrogen and phosphorus releasing and process optimization on lincomycin removal from lincomycin mycelial residues

Lincomycin mycelial residues (LMRs), one kind of bio-wastes with a high biomass organic content, are limited to use due to residual lincomycin. Recycling of LMRs is not only benefit to economy but also to environment. This study developed an acidic hydrothermal method for LMRs treatment. Effects of reaction temperature (100, 130 and 160 °C), residence time (60, 120 and 180 min), and H2SO4 concentration (0.2, 0.4 and 0.6 M) on the amount and distributions of organics, nitrogen and phosphorus were investigated. In addition, these three crucial parameters for maximum removal of lincomycin were optimized using response surface methodology (RSM). Meanwhile, intermediates of lincomycin treated by acidic hydrothermal treatment (AHT) were identified by liquid chromatography – mass spectrometry (LC/MS). Antibacterial assessments of them were conducted via disk diffusion tests. Results showed that the treatments led to 34.7%–251% and 30.9%–214% in the concentrations of TN and TP, respectively, and 1.44–3.89 times higher of SCOD in the soluble phase of LMRs. Lincomycin removal rates increased with the increasing of reaction temperature, residence time and H2SO4 concentration in a certain range. The optimal conditions were obtained at activation temperature of 160 °C, residence time of 157.2 min and a H2SO4 concentration of 0.53 M, where 98.3% of lincomycin was removed. Moreover, inhibition of lincomycin after AHT on Staphyococcus aureus, with respect to untreated solutions containing this compound reduced significantly. Therefore, recycling of LMRs is promising after removal residual lincomycin via AHT.

Controlling the Morphology and Size of GdF3:RE3+ (RE = Dy, Tb, and Sm) by pH Value: Growth Mechanism, Energy Transfer, and Luminescent Properties

In this paper, the synthesis of rare earth fluoride GdF3 multiform morphologies via a glutamic acid hydrothermal method has been fulfilled. The size and shape of the products could be tuned just by adjusting the pH values of the initial reaction solutions. The morphologies for the products include spindle-like, peanut-like, submicrometer flowers, and nanoflowers. Additionally, the possible formation mechanism of multiform morphologies was proposed. Furthermore, we systematically investigate the luminescence properties of different lanthanide ions (Dy3+, Tb3+, and Sm3+) in GdF3 host. In the GdF3:Tb3+,Sm3+system, the energy transfer process fromTb3+ to Sm3+ was demonstrated to be resonant type via a dipole–dipole mechanism. Most interestingly, white light and multicolor light have been obtained in Tb3+ and Sm3+ coactivated or Dy3+,Tb3+,Sm3+ tridoped GdF3 phosphors. The results show that the obtained nanophosphors have a promising application in display and lighting fields.

Diamine Functionalized Cubic Mesoporous Silica for Ibuprofen Controlled Delivery.

A diamine functionalized cubic mesostructured KIT-6 (N-KIT-6) has been prepared by post-synthetic method using calcined mesoporous KIT-6 with a diamine source, i.e., N-'[3-(tri methoxysilyl)- propyl]'ethylenediamine. The KIT-6 mesoporous silica used for N-KIT-6 was synthesized under weak acidic hydrothermal method using bitemplates, viz., Pluronic P123 and 1-butanol. The synthesized mesoporous materials, KIT-6 and N-KIT-6, have been characterized by the relevant instrumental techniques such as SAXS, N2 sorption isotherm, FT-IR, SEM, TEM and TGA to prove the standard mesoporous materials with the identification of diamine groups. The characterized mesoporous materials, KIT-6 and N-KIT-6, have been extensively used in the potential application of controlled drug delivery, where ibuprofen (IBU) employed as a model drug. The rate of IBU adsorption and release was monitored by UV vis-spectrometer. On the basis of the experimental results of controlled drug delivery system, the results of IBU adsorption and releasing rate in N-KIT-6 are higher than those of KIT-6 because of the higher hydrophobic nature as well as rich basic sites on the surface of inner pore wall silica.

Process intensification effect of ball milling on the hydrothermal pretreatment for corn straw enzymolysis

Enhancement of the cellulose accessibility is significant for biomass enzymatic hydrolysis. Here, we reported an efficient combined pretreatment for corn straw enzymolysis using ball milling and dilute acid hydrothermal method (a mixture solvent of H2O/ethanol/sulfuric acid/hydrogen peroxide liquid). The process intensification effect of ball milling on the pretreatment of the corn straw was studied through the comparative characterization of the physical–chemical properties of the raw and pretreated corn straw using FT-IR, BET, XRD, SEM, and HPLC analysis. The effect of the pretreatment temperature was also investigated. Furthermore, various pretreatment methods were compared as well. Moreover, the pretreatment performance was measured by enzymolysis. The results showed that ball milling had a significant process intensification effect on the corn straw enzymolysis. The glucose concentration was dramatically increased from 0.41 to 13.86mgmL−1 after the combined treatment of ball milling and hydrothermal. The efficient removal of lignin and hemicellulose and the enlargement of the surface area were considered to be responsible for this significant increase based on the intensive analysis on the main components and the physical–chemical properties of the raw and pretreated corn straw.

In situ synthesis of TiH2 layer on metallic titanium foil through gaseous hydrogen free acid-hydrothermal method

A novel strategy for synthesis of TiH2 layer on surface of metallic titanium by using an acid-hydrothermal method was proposed. During the synthesis process, no any elemental hydrogen was involved. X-ray powder diffraction, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy results confirmed that a TiH2 layer of 20μm thickness on a Ti foil surface can be formed in situ by an interface reaction of metallic titanium with sulfuric acid solution, hydrochloric acid, or phosphoric acid, which is a hydrogen self-storage process. By tuning reaction parameters, for example, concentration of acid, composition and morphology of TiH2-Ti hybrid materials can be adjusted. The TiH2 layer on a metallic titanium surface can be decompounded completely heated below 400°C. This convenient, safe and low-cost method is a promising gaseous hydrogen free approach for the synthesis of hydride-based hydrogen storage materials.

Nanoheterostructures on TiO2 nanobelts achieved by acid hydrothermal method with enhanced photocatalytic and gas sensitive performance

Nanoheterostructures of TiO2 nanoparticles/TiO2 nanobelts and Ag/TiO2 nanoparticles/TiO2 nanobelts are prepared by the acid-assisted hydrothermal method followed by an in situ photo-reduction process. The experimental parameters, including acid corrosion time and calcination temperature, are investigated in detail. Compared with TiO2 nanobelts, the single nanoheterostructure TiO2 nanoparticles/TiO2 nanobelts have a better photocatalytic activity. The double nanoheterostructure Ag/TiO2 nanoparticles/TiO2 nanobelts can further dramatically enhance photocatalytic properties of TiO2 nanobelts. The mechanisms for formation of the heterostructure and the enhanced photocatalytic effect of the heterostructure are discussed. The liquid continuous-flow photocatalysis based on TiO2 nanobelt nanopaper with different heterostructures is carried out, which has an efficient photocatalytic ability. At the same time, the obtained TiO2 nanobelt heterostructures have a good gas sensitive performance for ethanol.

Control synthesis of rutile TiO2 microspheres, nanoflowers, nanotrees and nanobelts via acid-hydrothermal method and their optical properties

Semiconductor rutileTiO2 nanostructures with a diversity of well-defined morphologies, such as microspheres, nanoflowers, nanotrees and nanobelts, are synthesized via an acid-hydrothermal process without any structure-directing agents. Their morphologies, crystal structures and orientation relationship were characterized by X-ray diffraction, scanning electron microscopy and high-resolution transmission electron microscopy. By controlling hydrochloric acid concentration, anisotropic growth of the rutile TiO2 leads to various morphologies. The synthesis mechanism of rich TiO2 nanostructures was also studied. Finally, the relationship between optical properties and the structural complexity of the rutileTiO2 nanocrystals was characterized.

Bifunctional single-crystalline rutile nanorod decorated heterostructural photoanodes for efficient dye-sensitized solar cells

A novel heterostructural TiO(2) nanocomposite, which consists of single-crystalline rutile TiO(2) nanorod decorated Degussa P25 nanoparticles, has been fabricated through a facile acidic hydrothermal method and successfully applied as the photoanodes for efficient dye-sensitized solar cells. The morphology, crystal structure, specific surface area and pore size distribution of the obtained nanocomposite were systematically investigated by X-ray diffraction (XRD), field-emission scanning electron microscope (FESEM), high resolution transmission electron microscope (HRTEM), selected-area electron diffraction patterns (SAED) and nitrogen adsorption-desorption measurements. Under standard illumination conditions (AM 1.5, 100 mW cm(-2)), devices with these hybrid anodes exhibited considerably enhanced photocurrent density and overall conversion efficiency in comparison with that of the commercial Degussa P25 electrodes, which can be partially attributed to the light scattering effect in the long-wavelength region as evidenced from the incident photon-to-current conversion efficiency (IPCE) response and the diffuse reflectance spectroscopy. More importantly, devices employing these hybrid anodes have demonstrated extended electron lifetimes and larger electron diffusion coefficient as validated by the intensity-modulated photocurrent/photovoltage spectroscopy measurements, which can be mainly ascribed to the fast electron transport and collection superiority of the single-crystalline nanorods.