Qun-Yan Li

Highly Hydrothermally Stable Microporous Silica Membranes for Hydrogen Separation

Fluorocarbon-modified silica membranes were deposited on gamma-Al2O3/alpha-Al2O3 supports by the sol-gel technique for hydrogen separation. The hydrophobic property, pore structure, gas transport and separation performance, and hydrothermal stability of the modified membranes were investigated. It is observed that the water contact angle increases from 27.2+/-1.5 degrees for the pure silica membranes to 115.0+/-1.2 degrees for the modified ones with a (trifluoropropyl)triethoxysilane (TFPTES)/tetraethyl orthosilicate (TEOS) molar ratio of 0.6. The modified membranes preserve a microporous structure with a micropore volume of 0.14 cm3/g and a pore size of approximately 0.5 nm. A single gas permeation of H2 and CO2 through the modified membranes presents small positive apparent thermal activation energies, indicating a dominant microporous membrane transport. At 200 degrees C, a single H2 permeance of 3.1x10(-6) mol m(-2) s(-1) Pa(-1) and a H2/CO2 permselectivity of 15.2 were obtained after proper correction for the support resistance and the contribution from the defects. In the gas mixture measurement, the H2 permeance and the H2/CO2 separation factor almost remain constant at 200 degrees C with a water vapor pressure of 1.2x10(4) Pa for at least 220 h, indicating that the modified membranes are hydrothermally stable, benefiting from the integrity of the microporous structure due to the fluorocarbon modification.

Preparation and characterization of nanostructured Ni(OH)2 and NiO thin films by a simple solution growth process

Nanostructured Ni(OH)2 thin films were prepared by a simple solution growth process with F(-) and NH3 used as Ni2+ coordination agents, and ammonia hydroxide solution used as OH(-) supplier to accelerate the hydrolyzation of nickel complex species. The results showed Ni(OH)2 thin films were constructed mainly with hexagonal beta-Ni(OH)2 nanorods; the F(-) and NH3 in reactive solutions played important roles in the film growth process; and solution pH had great influence on the morphologies of thin films, which was explained by the competition of Ni(OH)2 nucleation and growth in solutions. NiO crystallinity thin films were obtained by annealing Ni(OH)2 thin films at 400 degrees C for 2 h and the morphologies of the Ni(OH)2 thin films were sustained well during the annealed process.

A rapid and low solvent/silylation agent-consumed synthesis, pore structure and property of silica aerogels from dislodged sludge

Dislodged sludge, a kind of industrial waste, was used as raw material to prepare silica aerogels via ambient pressure drying. The effect of solvent exchange and surface silylation on the pore structure and property of the obtained materials was investigated in detail. If the ethanol and n-hexane exchange decreases to 8 h (two times, each time for 4 h) and 4 h (one time), respectively, and the volume ratio of ethanol/wet gel and n-hexane/wet gel reduces to 2 and 1, respectively, the obtained materials exhibit a desirable pore volume of 3.17 cm3/g, a water contact angle of 152.9° and a low thermal conductivity of 0.030 W/ (m·K). Further decreasing the mole ratio of silylation agent/SiO2 to 0.5 and the silylation time to 6 h results to silica aerogels with a pore volume of 3.44 cm3/g, a water contact angle of 144.5° and a low thermal conductivity of 0.032 W/ (m·K). A rapid synthesis (a total time of 50 h, from wet gel aging to ambient pressure drying) of silica aerogels has been realized and the consumption of solvent/silylation agents has been pronouncedly reduced without sacrificing the thermal insulation property of the obtained materials.Graphical Abstract

Mesoporous organosilicas with ultra-large pores: mesophase transformation and bioadsorption properties.

Large pore ordered mesoporous organosilicas (OMOs) with distinct mesophase structure was synthesized under low temperatures by the co-condensation of 1,2bis(triethoxysilyl)ethane (BTESE) and tetraethyl orthosilicate (TEOS) in acidic solution, using triblock copolymer F127 as a template and 1,3,5-trimethylbenzene (TMB) as a swelling agent. With the decrease of temperature, a mesophase transformation from 2D hexagonal structure (p6mm) via mesostructured cellular foam to a highly ordered 3D cubic structure (Fm3m) was evidenced by small angle X-ray diffraction (SAXS), transmission electron microscopy (TEM) and N(2) sorption. It reveals that the lower synthesis temperatures may influence the hydrolysis and condensation of silica species and the hydrophilic-hydrophobic property of F127, as well as the swelling capacity of F127 micelles with TMB, which resulting in a formation of large pores ordered mesoporous organosilicas with various mesostructures materials. Finally, the enzyme adsorption properties of the OMOs were investigated and the results showed that the OMOs with a 3D large pore structure and regular morphology is much more qualified for enzyme adsorption.

Preparation of Silica Aerogels by Ambient Pressure Drying without Causing Equipment Corrosion

The silica aerogels were prepared via a sol-gel technique and ambient pressure drying by using industrial solid wastes, dislodged sludges, as raw materials. A strategy was put forward to reduce the corrosion of equipment during the drying procedure. The pore structure, hydrophobicity, and thermal insulation property of the obtained samples were investigated in detail. The results show that the corrosion can be effectively avoided by using an equimolar mixture of trimethylchlorosilane (TMCS) and hexamethyldisilazane (HMDS) as silylation agents. At a Si:TMCS:HMDS molar ratio of 1:0.375:0.375, the silica aerogels possess a desirable pore structure with a pore volume of 3.3 ± 0.1 cm3/g and a most probable pore size of 18.5 nm, a high hydrophobicity with a water contact angle of 144.2 ± 1.1°, and a low thermal conductivity of 0.031 ± 0.001 W/(m∙K).

Loading and release of Ibuprofen (IBU) in a novel network hollow magnetic mesoporous SiO2/Fe3O4 microspheres (HMMSs)

The hollow magnetic mesoporous SiO2/Fe3O4 microspheres with different pore sizes were prepared by adjusting the addition of swelling agent (1, 3, 5-trimethylbenzene). The hollow magnetic mesoporous SiO2/Fe3O4 microspheres were modificated with different degree of aminopropyl groups via co-condensation method. The specific surface area, pore size, pore volume and ibuprofen loading of obtained composite microspheres were investigated in detail. The results showed that ibuprofen loading was increased with the mesoporous size increasing, and addition of swelling agent can improve the mesoporous size. When the pore size was up to 3.79 nm, ibuprofen reached the highest loading amount (816 mg/g). After modification of the aminopropyl group, which was located in the mesoporous channel, the ibuprofen loading was slightly reduced but the release rate of IBU was significantly decreased. Optimal release properties were achieved when the modification amount of the aminopropyl group was 10%, the ibuprofen continued to be released even after 32 h and the total release quantity is 70%, while the IBU release amount was 93% in the non-functionalized composite microspheres in 12 h. Meanwhile, the Korsmeyer–Peppas equation Q = ktn was employed to analyze the drug release profile. The hollow magnetic mesoporous SiO2/Fe3O4 microspheres had a high magnetization saturation value of 39.4 emu/g, which demonstrated a good responsivity to magnetic fields.Graphical Abstract

Rapid Aqueous Synthesis of Mesoporous Carbon and Their HRP Immobilization Performance

Mesoporous carbons have been rapidly synthesized by an aqueous way using polymerization of phloroglucinol and formaldehyde in the presence of triblock copolymer F127 (PEO106PPO70PEO106) under different conditions of hydrochlo- ric acid. The micromorphology, pore structure of the obtained materials were characterized in detail by TEM, SEM and N2 adsorption-desorption. The obtained mesoporous carbons were utilized to adsorb the horseradish peroxidase (HRP) and the thermal stability, pH stability and storage stability of the immobilized HRP activity were also investigated. The results reveal the as-synthesized mesoporous carbon has a wormhole-like mesopore structure. The concentration of hydrochloric acid is a key factor influencing the polymerization rate of phenolic resins. With the concentrations of hydrochloric acid increasing from 0.5 mol/L to 2.5 mol/L, the pore size of mesoporous carbons decreased from 7.6 nm to 5.6 nm, the BET surface areas decreased from 787.8 m 2 /g to 691.1 m 2 /g, and pore volumes decreased from 0.64 cm 3 /g to 0.49 cm 3 /g. During the process of polymerization, the phase separation appeared in 20 min, while in the reported work, the polymerization of resorcinol and phenol with formaldehyde took much longer time. After incubation at 70 ℃ for 30 min, the activity of immobilized HRP decreased slowly than that of the free HRP. The free and immobilized HRP remained 12.33% and 56.22% of their initial activity, respectively. Compare to free HRP, the immobilized HRP exhibited higher retention activity with a wider pH range between 4.0 and 10.0. The activity of immobilized HRP was also tested for both operation and storage stability. The enzyme activity of immobilized HRP decreased with increasing amount of recycle times. After recycled for 10 d, the activity of im- mobilized HRP retains 29% of its initial activity. The activity of immobilized enzyme could retain as high as 62% of its ini- tial activity after 50 d of storage at 4 ℃, while the free HRP only retains 31%. The results have shown that the thermal sta- bility, pH stability and storage stability of immobilized enzyme were significantly improved in comparison with free HRP. Keywords rapid aqueous synthesis; mesoporous carbon; horseradish peroxidase; immobilization