[Spectral Analysis of Trace Fluorine Phase in Phosphogypsum].

Phosphogypsum, which contains more than 90% of the calcium sulfate dehydrate (CaSO4 · 2H2O), is a kind of important renewable gypsum resources. Unlike the natural gypsum, however, phosphorus, fluorine, organic matter and other harmful impurities in phosphogypsum limit its practical use. To ascertain the existence form, content and phase distribution of trace fluoride in phosphogypsum has important theoretical values in removing trace fluoride effectively. In this present paper, the main existence form and phase distribution of trace fluoride in phosphogypsum was investigated by the combination of X-ray photoelectron spectroscopy (XPS) and Electron microprobe analysis (EMPA). The results show that trace fluoride phase mainly includes NaF, KF, CaF2, K2SiF6, Na2SiF6, Na3AlF6, K3AlF6, AlF3 · 3H2O, AlF2.3(OH)0.7 · H2O, Ca5(PO4)3F, Ca10(PO4)6F2. Among them, 4.83% of fluorine exists in the form of fluoride (NaF, KF, CaF2); Accordingly, 8.43% in the form of fluoride phosphate (Ca5(PO4)3F, Ca10(PO4)6F2); 12.21% in the form of fluorine aluminate (Na3AlF6, K3AlF6); 41.52% in the form of fluorosilicate (K2SiF6, Na2SiF6); 33.02% in the form of aluminum fluoride with crystal water (AlF3 · 3H2O, AlF2.3(OH)0.7 · H2O). In the analysis of phase constitution for trace elements in solid samples, the method of combining XPS and EMPA has more advantages. This study also provides theoretical basis for the removal of trace fluorine impurity and the effective recovery of fluorine resources.

[FTIR analysis of oil shales from Huadian Jilin and their pyrolysates].

Thermochemical conversion is the key technology for the comprehensive utilization of Chinese oil shale resources. Oil shales from three mining areas of Huadian Jilin were pyrolyzed at 500 degrees C in a quartz tube reactor and their pyrolyzed cokes and shale oil were derived. One oil shale was also pyrolyzed at 600 degrees C and 700 degrees C to assess the influence of temperature on pyrolysates. FTIR analysis was carried out to study the raw shales and their products. The results showed that shale oil had similar functional groups as the organic matter of oil shale, mainly aliphatic hydrocarbon, and the shale oil contained more of it than the raw material. The shale with more aliphatic oil yielded more oil. That with less aliphatic and more aromatic one yields less oil, and its coke is rich in condensed aromatics. Pyrolysis was almost completed at 500 degrees C. Oil yield did not increase further with temperature, but secondary pyrolysis strengthened. At 700 degrees C carbonates began to decompose.

Emissions of SO2, NO and N2O in a circulating fluidized bed combustor during co-firing coal and biomass.

This paper presents the experimental investigations of the emissions of SO2, NO and N20 in a bench scale circulating fluidized bed combustor for coal combustion and co-firing coal and biomass. The thermal capacity of the combustor is 30 kW. The setup is electrically heated during startup. The influence of the excess air, the degree of the air staging, the biomass share and the feeding position of the fuels on the emissions of SO2, NO and N2O were studied. The results showed that an increase in the biomass shares resulted in an increase of the CO concentration in the flue gas, probably due to the high volatile content of the biomass. In co-firing, the emission of SO2 increased with increasing biomass share slightly, however, non-linear increase relationship between SO2 emission and fuel sulfur content was observed. Air staging significantly decreased the NO emission without raising the SO2 level. Although the change of the fuel feeding position from riser to downer resulted in a decrease in the NO emission level, no obvious change was observed for the SO2 level. Taking the coal feeding position R as a reference, the relative NO emission could significantly decrease during co-firing coal and biomass when feeding fuel at position D and keeping the first stage stoichiometry greater than 0.95. The possible mechanisms of the sulfur and nitrogen chemistry at these conditions were discussed and the ways of simultaneous reduction of SO2, NO and N20 were proposed.

Fabricating a sustained releaser of heparin using SBA-15 mesoporous silica.

The sustained release of heparin in sufficient amounts and over long time is a challenge to drive the development of functional materials. In this paper SBA-15 mesoporous silica is selected in the search for a favorable morphology and optimized surface state for the sustained release of heparin. In situ carbonization of the template in the as-synthesized sample enables SBA-15 to possess narrowed channels with rougher surfaces, while modification with (aminopropyl)triethoxysilane (APTES) through a one-pot synthesis offers SBA-15 with positive charges to attract heparin through electro-static interactions. The structure of modified SBA-15 samples is assessed with XRD (powder X-ray diffraction analysis), nitrogen adsorption-desorption and electron microscopy techniques, and their performance is evaluated in adsorption and release of heparin. These modifications improve the heparin adsorption in SBA-15 and thus promote its sustained release, prolonging the release-equilibrium time up to 60 days. Among them, the SBA-15 sample modified with APTES can trap three times as much heparin as the parent SBA-15, and the release ratio is elevated to 80% (that of SBA-15 is 38%), realizing the best performance of controlling heparin release to date.

One-pot synthesis of a hierarchical PMO monolith with superior performance in enzyme immobilization.

A novel hierarchical periodic mesoporous organosilica (PMO) monolith is synthesized by using N,S-bis[3-(triethoxysilyl)propyl]-carbamothioic acid for the first time, in order to fabricate a highly efficient enzyme immobilizer. The hierarchical monolith is spontaneously formed with mild shearing force without further additives, in which the primary particles can be selectively prepared to be inter-connected with each other end to end to form a net-like framework throughout the whole monolith, and the inorganic/organic composition is finely controlled by adjusting the initial composition of the silica precursors. As the result, an ordered net framework with micrometer sized macropores and large mesopores is simultaneously obtained together with a high organic content, favoring high enzyme immobilization, in which they demonstrate an enhanced adsorption capacity, superior immobilization stability and good reusability. Especially, the PMO monolith can adsorb 126 mg g-1 of horseradish peroxidase (HRP), higher than double that of the power-like analogue (38 mg g-1); and the bioactivity is three times higher than that of the free enzyme, indicating the strong advantages of morphology assistance in enzyme immobilization.

Multiple functionalization of SBA-15 mesoporous silica in one-pot: fabricating an aluminum-containing plugged composite for sustained heparin release.

To fabricate an efficient releaser of heparin, which is an extensively used anticoagulant, aluminum containing plugged mesoporous silica SBA-15 is prepared using a one-pot synthesis process. A suitable aluminum additive in the starting mixture enables plugs to be formed inside hexagonal channels and Al species to be incorporated into the mesostructure, evidence for which is provided by powder X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), N2 sorption measurements and 27Al MAS NMR tests. Incorporation of aluminum in SBA-15 reduces the negative charge (Zeta-potential) and tailors the surface roughness of the channel through forming plugs, and the former significantly improves heparin adsorption while the latter retards heparin release. As a result, these modified composites adsorb 2-4 times more heparin than parent SBA-15 and release 60-130% more of the drug over several weeks; the sample possessing both an Al-component and plug structure can sustain release of heparin for 6 weeks, demonstrating the increased efficiency of multiply functionalized SBA-15 in the controllable release of heparin and offering a valuable clue for design of novel drug releasers.

Promoting immobilization and catalytic activity of horseradish peroxidase on mesoporous silica through template micelles.

New concept on the promotion of immobilization and catalytic activity of enzyme on mesoporous silica through template micelles is proposed and realized in this paper. Proper P123 templates are controllable retained in the as-synthesized SBA-15, not only to anchor the horseradish peroxidase (HRP) guest, but also to establish the crowding-like microenvironment around the enzyme. The influence of retaining templates on the pore structure of SBA-15, immobilization, and catalytic activity of HRP is studied, and the possible process of template removal is proposed. Ethanol refluxing of 6 h is conformable to prepare the optimal mesoporous support characterized with the retained templates of about 8%. With the assistance of retained templates in SBA-15, up to 49 mg g(-1) of HRP can be immobilized, 100% more than that on calcined SBA-15. Furthermore, the thermal stability, the resistance of pH variation and denaturing agent urea, and the recycle usage of HRP immobilized are obviously elevated, paving a novel and low-cost route to develop enzyme catalysts.

Sustained release of heparin on enlarged-pore and functionalized MCM-41.

Mesoporous silica MCM-41 and SBA-15 were chosen to study the adsorption and release of bulky biomolecule heparin, in order to develop new heparin controlled delivery system and expand the application of mesoporous materials in life science. To explore how the structure of support such as pore size and surface state affects the accommodation and release of heparin, we used decane as swelling agent to enlarge pores of MCM-41, introduced amino groups for improving the biocompatibility of support, and controllably retained templates in the as-synthesized sample. The influence of modification on the structure of samples was investigated by XRD and N(2) adsorption-desorption, whereas their performance of adsorbing and releasing heparin was assessed with that of toluidine blue method. Both enlarged pore and organic modification significantly promoted the adsorption and prolonged the release of heparin in MCM-41, and the release was characterized with a three-stage release model. The mechanism of heparin release from mesoporous material was studied by fitting the release profiles to the theoretical equation. As expected, some mesoporous composites could release heparin in the long term with tuned dosage.

Controlling the primary particle evolution process towards silica monoliths with tunable hierarchical structure.

In order to establish the hierarchical structure in multiple levels on mesoporous silica, this article reports a new strategy to prepare the monolith with the pore configuration in nanometer scale, micro-morphology in micrometer level and macroscopic shape in millimeter or larger grade. These hierarchical monoliths are synthesized in a weak acidic condition by using triblock copolymer P123, hydroxyl carboxylic acid and tetramethyl orthosilicate (TMOS), and the textural properties of the mesostructure can be facilely adjusted by simply controlling the synthesis condition without any additive. During the synthesis, the primary particles can be selectively synthesized as monodispersed sphere, noodle, prism, straight rods with different size or irregular bars, and their connection plus arrangement in 3D directions can be also regulated. Therefore, various textural properties of mesopore are able to be altered including pore size (5.5-10.6 nm), total pore volume (0.48-1.2 cm(3) g(-1)), micropore surface area (47-334 m(2) g(-1)), and pore shape (from 2D or 3D straight channel to plugged channel). Moreover, these monoliths exhibit a considerable mechanical strength; they are also applied in eliminating particulate matters and tobacco special nitrosamines (TSNA) in tobacco smoke, exhibiting various morphology-assisted functions.

Novel phenol capturer derived from the as-synthesized MCM-41.

Novel phenol-capturer was prepared by modifying the as-synthesized mesoporous silica MCM-41 with tetraethylenepentamine (TEPA), not only saving the energy and time for removal of template, but also opening the way to utilize the micelles for adsorption. Once the organic modifier was distributed in the template micelle of MCM-41 to form a web within the mesoporous channel, the composite could adsorb more phenols in gas stream than activated carbon for the first time. With an unwanted high adsorption capacity, this mesoporous silica-amine composite represented potential application for trapping phenols, especially in tobacco smoke to protect environment.

Low-cost and effective phenol and basic dyes trapper derived from the porous silica coated with hydrotalcite gel.

Novel low-cost and effective adsorbents of phenol and basic dyes were made by coating amorphous silica with hydrotalcite (HT) gel followed by soaking in alkaline solution, and the surface basic-acidic properties of resulting composites were evaluated by CO(2)-TPD, Hammett indicator method and NH(3)-TPD, respectively. Both BET surface area and microporous surface area of the composites were increased after they were soaked with alkaline solution; meanwhile the center of pore size distribution was changed from 9 to 3-4 nm. These composites efficiently captured phenol in gaseous and liquid phases, superior to mesoporous silica such as MCM-48 or SBA-15 and zeolite NaY, and the equilibrium data of gaseous adsorption could be well fitted to Freundlich model. These modified silicas also exhibited high adsorption capacity forward basic dyes such as crystal violet (CV) and leuco-crystal violet (LCV), reaching the adsorption equilibrium within 1 h and offering a new material for environment protection.

Hierarchical functionalized MCM-22 zeolite for trapping tobacco specific nitrosamines (TSNAs) in solution.

To enable zeolite to trap bulky environment pollutants such as tobacco specific nitrosamines (TSNAs), we tailored the porous structure of MCM-22 zeolite by desilication to obtain a sample with mesopores centered 3.5 nm, in order to promote the mass transport. The meso-MCM-22 was further functionalized with -SO(3)H group to enhance the efficiency in adsorption of TSNAs. The composites were characterized by XRD and BET methods, and their adsorptive function was assessed in both liquid adsorption of N'-nitrosonornicotine (NNN) and the adsorption of TSNAs in aqueous tobacco-extract solution. Grafting -SO(3)H group on alkaline-treated MCM-22 significantly elevated the adsorption toward nitrosamines, and the resulting composite could reduce above 70% of NNN in dichloromethane solution or 54% of TSNAs in tobacco-extract solution.

Effective nitrosamines trap derived from the in situ carbonized mesoporous silica MCM-41.

A new route to modify the mesoporous silica MCM-41 with carbon, using the inherent surfactant template in the as-synthesized sample as the carbon precursor, is reported in this article. Apart from the advantage of omitting energy and time required for removal of template, the resulting silica-carbon composites exhibit a high efficiency in adsorption and catalytic decomposition of N-nitrosopyrrolidine (NPYR), the typical carcinogenic pollutant in environment. The influence of carbonization temperature on the structure and performance of the resulting carbon-silica composite was investigated by use of XRD, N(2) adsorption-desorption, FTIR and TG-DSC techniques, and the instantaneous adsorption and the temperature-programmed surface reaction (TPSR) of NPYR as well as the reduction of nitrosamines level of cigarette smoke were also utilized to assess the actual function of these composites. The carbonization performed in the range of 773-973 K enabled the resulting composites to possess a higher activity than parent MCM-41 in eliminating volatile nitrosamines, which is beneficial for controlling carcinogenic pollutants in environment.

Adsorption of nitrosamines by mesoporous zeolite.

On the basis of a study of the adsorption of zeolite and mesoporous silica, we attempted to create a hierarchical structure in the new nitrosamines trapper. Thus, mesoporous HZSM-5 zeolite was fabricated through impregnating a structure-directing agent into the as-synthesized MCM-41 followed by dry-gel conversion to transform amorphous silica to zeolite crystal. The texture of mesoporous ZSM-5 was tailored by adjusting the Si/Al ratio in the MCM-41 source and the thermal treatment time. The resulting samples were characterized by N(2) adsorption to evaluate their textural properties. One volatile nitrosamine, N-nitrosopyrrolidine (NPYR), was used as probe molecule in instantaneous adsorption to survey the function of the resulting composites. Adsorptions of N'-nitrosonornicotine (NNN) in dichloromethane solution and tobacco-specific nitrosamines (TSNA) in tobacco-extract solution were also utilized for the same purpose. As expected, mesoporous zeolite exhibits a good adsorption capacity in laboratory tests, superior to either microporous zeolite or mesoporous silica, providing a valuable candidate for controlling nitrosamines in the environment.