An efficient calcium-based sorbent for flue gas dry-desulfurization: promotion roles of nitrogen oxide and oxygen.

The development of sorbents for flue gas desulfurization in a dry mode is essential to control emission of sulfur dioxide. Based on the novel concept of "treating waste with waste", a low-cost and highly activated calcium-based sorbent (ACS) was prepared using coal fly ash, CaO and waste gypsum as the raw materials via the one-step incipient wetness impregnation method. Based on characterization using scanning electron microscopy and nitrogen adsorption-desorption, the ACS possessed a fibrous and netted structure with high porosity, which improved SO2 adsorption greatly. The SO2 adsorption capacity of ACS with coal fly ash/CaO/CaSO4 = 1/2/1 was high, up to 44.26 mg g-1, with 100% removal efficiency at 150 °C. In the absence of O2, SO2 was rapidly adsorbed on the sorbent to form CaSO3 according to in situ DRIFTS analysis, while when O2 was present in the flue gas, SO2/SO3 2- tended to be oxidized into SO4 2- species. Moreover, the presence of NO can further enhance the SO2 adsorption capacity of the ACS due to the formation of adsorbed NO2 or nitrate species with strong oxidizing properties. Therefore, the ACS can be considered as a sustainable sorbent with the advantage of employing fly ash for the removal of sulfur dioxide.

Hydrogenation of CO to olefins over a supported iron catalyst on MgAl2O4 spinel: effects of the spinel synthesis method.

In the process of CO hydrogenation to olefins by the Fischer-Tropsch synthesis (FTO), the support is a key factor in the activity, selectivity, and thermal and chemical stability of the catalysts, and magnesium aluminate spinel (MgAl2O4) has recently been reported to be very effective. In this work, three methods, namely, citric acid solution combustion (MAC), EDTA sol-gel (MAG) and NH3-coprecipitation (MAP) have been employed to prepare the spinel with detailed characterization of the structure, specific surface area, porosity, and alkalinity properties of both the as-synthesized spinel and the supported catalysts. The results showed that MAC and MAG possessed stronger basicity with more homogeneous particle sizes and narrower distribution of the pore size due to the formation of the metal-nitrate-chelate-complex. This led to a large quantity of gas being released during calcination, however, stronger interactions between the active phase and MAC resulted in lower CO conversion. The catalyst supported on MAP (CMAP) exhibited the highest CO conversion, the highest selectivity of lower olefins, the shortest induction period of reaction, and the lowest AFS chain growth probability; thus, MAP was suggested as an applicable synthetic method. Based on the CMAP catalyst, the effects of the operational conditions were investigated and a 200 hour stability test was carried out with satisfactory performance.

Deactivation kinetics of individual C6-C9 aromatics' generation from methanol over Zn and P co-modified HZSM-5.

A deactivation kinetic model has been determined for the methanol to aromatic process over a HZSM-5 zeolite catalyst (SiO2/Al2O3 = 30) modified by 1.0 wt% ZnO and 2.0 wt% P, in which the generation rates of C6-C9 aromatics are treated individually while olefins and paraffins are lumped as intermediate and byproduct, respectively. The time-dependent catalytic activity is described by a deactivation coefficient related to the concentration of both methanol and products. The established kinetic model is able to predict the product distribution along with on-stream time under various conditions and is identified to be valid by a model significance test. The effect of operating conditions on catalyst behavior was also investigated: deactivation rate increases dramatically with methanol partial pressure and temperature; higher feed methanol content leads to less aromatics and more paraffin; increasing temperature reduces paraffin generation and results in higher aromatic yield, especially benzene and toluene.

Repair of critical size bone defects with porous poly(D,L-lactide)/nacre nanocomposite hollow scaffold.

OBJECTIVE: To generate a novel porous poly(D,L-lactide)/nacre nanocomposite hollow scaffold. METHODS: This study was performed in the Department of Spine Surgery, Southern Medical University, Guangzhou, China from September 2010 to September 2011. Nacre nanoparticles were prepared using a physical process and identified by x-ray diffraction and transmission electron microscopy, to generate a novel scaffold though the salt leaching processing technique. The morphology and structure properties of this scaffold were further investigated under scanning electron microscope and mechanical property testing. Additionally, the biological characteristics were evaluated by cell culture experiments in vitro. Thirty-six rabbits were randomly divided into 3 groups. The defects were implanted with/without poly(D,L-lactide)/nacre scaffold or poly(D,L-lactide) scaffold. The results were assessed by radiographs and bone mineral density to monitor bone repairing. RESULTS: The nacre nanoparticles were spherical in shape, with a diameter range from 45-95 nm. The scaffolds possessed an interconnected porous structure with an average pore size of 322.5+/-50.8 µm, and exhibited a high porosity (82.5 +/-0.8%), as well as good compressive strength of 4.5+/-0.25 Mpa. Primary biocompatibility experiments in vitro showed that cells adhered and proliferated well on the scaffolds. The animal study further demonstrated that the scaffolds could repair the critical size segmental bone defects in 12 weeks. CONCLUSION: Newly established scaffolds may serve as a promising biomaterial for bone tissue engineering.

Hypertrophy of ligamentum flavum in lumbar spine stenosis associated with the increased expression of connective tissue growth factor.

Hypertrophy of the ligamentum flavum (LF) contributes to lumbar spinal stenosis (LSS), and results mainly from fibrosis. Connective tissue growth factor (CTGF) is a profibrotic factor involved in the fibrotic process. This study aimed to evaluate CTGF expression in hypertrophied lumbar LF and the involvement of CTGF in LF hypertrophy. Ten patients with LSS were enrolled in this study. The control group included 10 patients with lumbar disc herniation. LF thickness was measured on the preoperative axial T1-weighted MRI. LF samples were collected during surgery. LF fibrosis was scored by Masson's trichrome staining. CTGF expression was determined by enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry. Correlation between LF thickness and CTGF expression was analyzed. Human LF cells were cultured and treated with recombinant human (rh) CTGF. Expression of types I and III collagen was determined by real-time PCR and ELISA. The thickness and fibrosis scores of LF in the LSS group were higher than that in the control group (all P < 0.001). CTGF was expressed in the extracellular matrix of all ligament samples, and was significantly higher in the LSS group than that in the control group (P < 0.001). The increase of CTGF expression was positive correlation with the LF thickness (r = 0.969, P = 0.000). rhCTGF treatment increased the mRNA expression and protein synthesis of types I and III collagen of the LF cells (all P < 0.001). Our results suggest that the increased expression of CTGF is associated with hypertrophy of the LF in patients with LSS.

Amide-linkage formed between ammonia plasma treated poly(D,L-lactide acid) scaffolds and bio-peptides: enhancement of cell adhesion and osteogenic differentiation in vitro.

The surface characteristics of scaffolds for bone tissue engineering must support cell adhesion, migration, proliferation, and osteogenic differentiation. In the study, poly(D,L-lactide acid) (PDLLA) scaffolds were modified by combing ammonia (NH(3) ) plasma pretreatment with Gly-Arg-Gly-Asp-Ser (GRGDS)-peptides coupling technologies. The x-ray photoelectron spectroscopy (XPS) survey spectra showed the peak of N1s at the surface of NH(3) plasma pretreated PDLLA, which was further raised after GRGDS conjugation. Furthermore, N1s and C1s in the high-resolution XPS spectra revealed the presence of -C=N(imine), -C-NH-(amine), and -C=O-NH- (amide) groups. The GRGDS conjugation increased amide groups and decreased amine groups in the plasma-treated PDLLA. Confocal microscope and high performance liquid chromatography verified the anchored peptides after the conjugation process. Bone marrow mesenchymal stem cells were co-cultured with scaffolds. Fluorescent microscope and scanning electron microscope photographs revealed the best cell adhesion in NH(3) plasma pretreated and GRGDS conjugated scaffolds, and the least attachment in unmodified scaffolds. Real-time PCR demonstrated that expression of osteogenesis-related genes, such as osteocalcin, alkaline phosphatase, type I collagen, bone morphogenetic protein-2 and osteopontin, was upregulated in the single NH(3) plasma treated and NH(3) plasma pretreated scaffolds following GRGDS conjugation. The results show that NH(3) plasma treatment promotes the conjugation of GRGDS peptides to the PDLLA scaffolds via the formation of amide linkage, and combination of NH(3) plasma treatment and peptides conjugation may enhance the cell adhesion and osteogenic differentiation in the PDLLA scaffolds. © 2011 Wiley Periodicals, Inc. Biopolymers 95: 682-694, 2011.

[Effects of bioactive modification of poly-D,L-lactide acid scaffolds on the biological behaviors of the seed cells].

OBJECTIVE: To study the changes in the biological behavior of bone marrow mesenchymal stem cells (BMSCs) transfected with red fluorescent protein by lentivirus (RFP-BMSCs) seeded on in poly-D, L-lactide acid (PDLLA) scaffolds with bioactive modification by ammonia plasma and Gly-Arg-Gly-Asp-Ser (GRGDS) in vitro. METHODS: Circular sheets of PDLLA scaffolds (8 mm in diameter and 1 mm in thickness) were prepared and aminated with PDLLA (group A) or modified with the peptide conjugate A/PDLLA (group PA), with untreated PDLLA as the control (group P). The RFP-BMSCs were seeded on the scaffold materials and their proliferation and metabolic activity were detected using CyQuant NF and Alamar blue staining. The mineralization on the scaffolds was observed using calcein fluorescent dye under a fluorescent microscope. The adhesion and proliferation of RFP-BMSCs were observed by fluorescent microscope, and scanning electron microscope (SEM) was used to confirm the observed adhesion of the seed cells. RESULTS: The RFP-BMSCs seeded on the 3 scaffolds all showed proliferative activity at different time points after cell seeding, and the cell numbers decreased significantly in the order of PA>A>P (P<0.001). The cell number was significantly greater in group PA than in group A at all the time points except for days 10 (P=0.077) and 12 (P=0.491), and gradually became similar with the passage of time. The metabolic changes of the cells follow a similar pattern of cell proliferation. RFP-BMSCs showed more active proliferation in group A and group PA than in group P. On days 14 and 21, the intensity of green fluorescence decreased in the order of group PA, A and P. The RFP-BMSCs showed better adhesion in group PA than in group A, and the cells in group P appeared more scattered under scanning electron microscope. CONCLUSION: Bioactive modification of PDLLA by ammonia treatment and conjugation with GRGDS peptides may promotes the adhesion, proliferation, metabolism and mineralization of RFP-BMSCs seeded on PDLLA scaffolds.

[Histology and proliferative capability of thoracic vertebral body growth plates of rats at different ages].

OBJECTIVE: To compare the histological features of the thoracic vertebral body growth plates (VBGPs) of rats at different ages and assess their proliferative capability. METHODS: The thoracic VBGPs obtained from rats aged 1 day and 1, 4, 8, 16 and 28 weeks were identified using safranin O-fast green staining, and the height of the hypertrophic zone, proliferative zone, and resting zone were measured. The chondrocytes were isolated from these VBGPs with a modified trypsin-collagenase type II digestion method for primary culture in vitro. The expressions of proliferating cell nuclear antigen (PCNA) mRNA and protein was detected by real time-PCR and Western blotting, respectively. RESULTS: The 1-day- and 1-week-old rats showed significantly greater hypertrophic zone and proliferative zone in the VBGPs than older rats (P<0.01); the proliferative zone was significantly greater in rats aged 4 weeks than in those aged 28 weeks (P<0.05). The resting zone was obviously greater in rats aged 1 day and 1 week than in older rats (P<0.05), and also greater in rats aged 4 weeks than in those aged 16 and 28 weeks (P<0.05). Obvious ossification in the resting zone occurred at 16 weeks, and most of the resting zone became ossified at 28 weeks. The expression of PCNA decreased at both the mRNA and protein levels as the rats grew. CONCLUSION: The 3 zones of VBGPs are greater in rats aged 1 day and 1 week than in older ones. Ossification in the resting zone begins at 16 weeks, and till 28 weeks, most of the resting zone is ossified. The proliferation ability of VBGP chondrocytes decreases with the increase of age of the rats.

Experimental determination of equilibrium constant for the complexing reaction of nitric oxide with hexamminecobalt(II) in aqueous solution.

Ammonia solution can be used to scrub NO from the flue gases by adding soluble cobalt(II) salts into the aqueous ammonia solutions. The hexamminecobalt(II), Co(NH3)6(2+), formed by ammonia binding with Co2+ is the active constituent of eliminating NO from the flue gas streams. The hexamminecobalt(II) can combine with NO to form a complex. For the development of this process, the data of the equilibrium constants for the coordination between NO and Co(NH3)6(2+)over a range of temperature is very important. Therefore, a series of experiments were performed in a bubble column to investigate the chemical equilibrium. The equilibrium constant was determined in the temperature range of 30.0-80.0 degrees C under atmospheric pressure at pH 9.14. All experimental data fit the following equation well: [see text] where the enthalpy and entropy are DeltaH degrees = - (44.559 +/- 2.329)kJ mol(-1) and DeltaS degrees = - (109.50 +/- 7.126) J K(-1)mol(-1), respectively.

Novel homogeneous catalyst system for the oxidation of concentrated ammonium sulfite.

A homogeneous catalyst system made up of [Co(NH3)6]2+/I- has been put forward to catalyze the oxidation of concentrated ammonium sulfite. The experiments were performed in a packed column with sulfite concentrations above 2.5 mol l(-1), temperature range 20-65 degrees C, and oxygen partial pressure 0.052-0.21 atm. The experimental results indicate that the Co(NH3)6(2+)/I- homogeneous catalyst system can obviously accelerate the concentrated ammonium sulfite oxidation rate. After 2h reaction, the sulfite conversion is only 12.5% with no catalysts while 72.1% sulfite conversion can be obtained with 0.02 mol l(-1) Co(NH3)6(2+) and 0.005 mol l(-1) I- in the ammonium sulfite solution. The sulfite oxidation rate increases 284% as Co(NH3)6(2+) concentration increases from 0.01 to 0.02 mol l(-1). But there is little use increasing the Co(NH3)6(2+) concentration above 0.04 mol l(-1). The sulfite oxidation rate may increase 229% as the temperature increases from 20 to 65 degrees C. Sulfite oxidation rate is independent of the initial sulfite concentration. Increasing the oxygen partial pressure can increase the sulfite conversion. The reaction order with respect to oxygen is 1.2 and sulfite is zero. The apparent activation energy determined is 23.5 kJ mol(-1).

Kinetics of gas-liquid reaction between NO and Co(NH3)6(2+).

Wet ammonia desulphurization process can be retrofitted for combined removal of SO2 and NO from the flue gas by adding soluble cobalt(II) salts into the aqueous ammonia solutions. The Co(NH3)6(2+) formed by ammonia binding with Co2+ is the active constituent of scrubbing NO from the flue gas streams. A stirred vessel with a plane gas-liquid interface was used to measure the chemical absorption rates of nitric oxide into the Co(NH3)6(2+) solution under anaerobic and aerobic conditions separately. The experiments manifest that the nitric oxide absorption reaction can be regarded as instantaneous when nitric oxide concentration levels are parts per million ranges. The gas-liquid reaction becomes gas film controlling as Co(NH3)6(2+) concentration exceeds 0.02 mol/l. The NO absorption rate is proportional to the nitric oxide inlet concentration. Oxygen in the gas phase is favorable to the absorption of nitric oxide. But it is of little significance to increase the oxygen concentration above 5.2%. The NO absorption rate decreases with temperature. The kinetic equation of NO absorption into the Co(NH3)6(2+) solution under aerobic condition can be written as.

Simultaneous absorption of NO and SO2 into hexamminecobalt(II)/iodide solution.

An innovative catalyst system has been developed to simultaneously remove NO and SO2 from combustion flue gas. Such catalyst system may be introduced to the scrubbing solution using ammonia solution to accomplish sequential absorption and catalytic oxidation of both NO and SO2 in the same reactor. When the catalyst system is utilized for removing NO and SO2 from the flue gas, Co(NH3)(6)2+ ions act as the catalyst and I- as the co-catalyst. Dissolved oxygen, in equilibrium with the residual oxygen in the flue gas, is the oxidant. The overall removal process is further enhanced by UV irradiation at 365 nm. More than 95% of NO is removed at a feed concentration of 250-900 ppm, and nearly 100% of SO2 is removed at a feed concentration of 800-2500 ppm. The sulfur dioxide co-existing in the flue gas is beneficial to NO absorption into hexamminecobalt(II)/iodide solution. NO and SO2 can be converted to ammonium sulfate and ammonium nitrate that can be used as fertilizer materials. The process described here demonstrates the feasibility of removing SO2 and NO simultaneously only by retrofitting the existing wet ammonia flue-gas-desulfurization (FGD) scrubbers.

[Removal of nitric oxide from waste gas streams with hexamminecobalt solution].

Aqueous ammonia solution can be used to remove NO from waste gas streams by adding soluble cobalt(II) salt into aqueous ammonia solution. The hexamminecobalt(II) cations can not only bind nitric oxide but also activate oxygen molecules in aqueous solutions. Nitric oxide is absorbed and oxidized simultaneously in the same reactor. Nitric oxide can be turned into nitrite and nitrate. Activated carbon is used to catalyze the reduction of hexamminecobalt (III) to hexamminecobalt (II) to maintain the capability of removing NO with the hexamminecobalt solution. The influences of temperature and activated carbon particle size on the conversion of hexamminecobalt (III) are investigated. According to the experimental results, the catalytic reduction reaction rate increased with temperature. The influence of particle size of AC on the reduction of hexamminecobalt (III) in fixed bed reactor was very little. Oxygen in the gas phase was beneficial to the absorption of NO into the hexamminecobalt solution. The experiments performe manifestly that the hexamminecobalt solution coupled with catalytic regeneration of hexamminecobalt (II) was able to maintain a high nitric oxide removal efficiency for a long time. This method may have a bright promise in application.