Desulfurization of natural gas is achieved commercially by absorption with liquid amine solutions. Adsorption technology could potentially replace the solvent extraction process, particularly for the emerging shale gas wells with production rates that are generally lower than that from the large conventional reservoirs, if a superior adsorbent (sorbent) is developed. In this review, we focus our discussion on three types of sorbents: metal-oxide based sorbents, Cu/Ag-based and other commercial sorbents, and amine-grafted silicas. The advantages and disadvantages of each type are analyzed. Possible approaches for future developments to further improve these sorbents are suggested, particularly for the most promising amine-grafted silicas.
Bacterial adhesion to surfaces and subsequent biofilm formation are a leading cause of chronic infections and biofouling. These processes are highly sensitive to environmental factors and present a challenge to research using traditional approaches with uncontrolled surfaces. Recent advances in materials research and surface engineering have brought exciting opportunities to pattern bacterial cell clusters and to obtain synthetic biofilms with well-controlled cell density and morphology of cell clusters. In this article, we will review the recent achievements in this field and comment on the future directions.
A major limitation associated with fermentative hydrogen production is the low substrate conversion efficiency. This limitation can be overcome by integrating the process with a microbial fuel cell (MFC) which converts the residual energy of the substrate to electricity. Studies were carried out to check the feasibility of this integration. Biohydrogen was produced from the fermentation of cane molasses in both batch and continuous modes. A maximum yield of about 8.23 mol H2/kg CODremoved was observed in the batch process compared to 11.6 mol H2/kg CODremoved in the continuous process. The spent fermentation media was then used as a substrate in an MFC for electricity generation. The MFC parameters such as the initial anolyte pH, the substrate concentration and the effect of pre-treatment were studied and optimized to maximize coulombic efficiency. Reductions in COD and total carbohydrates were about 85% and 88% respectively. A power output of 3.02 W/m3 was obtained with an anolyte pH of 7.5 using alkali pre-treated spent media. The results show that integrating a MFC with dark fermentation is a promising way to utilize the substrate energy.
Powders of donepezil hydrochloride monohydrate (Form I) underwent isomorphic dehydration, losing 3% w/w water between 90% and 10% relative humidity (RH) without changing its powder X-ray pattern. Below 10% RH, additional dehydration occurred in conjunction with a reversible phase transition between the monohydrate state and a dehydrated state, with a 4.0% w/w loss to 0% RH. A combination of methods was used to understand the structural changes occurring during the desolvation process, including dynamic vapor sorption measurements, thermal analysis and powder X-ray diffraction. Form I showed the characteristics of the channel hydrate, whose non-isothermal dehydration behavior proceeds in two steps: (1) the loss of non-crystalline water adsorbed on the surface, and (2) the loss of one crystalline water in the channel. Dehydrated Form I is structurally similar to the monohydrate Form I. According to the heat of fusion and the crystal density criteria, the two crystal forms belonged to the univariant system, and the anhydrate (Form III) is stable. The dehydration kinetics was achieved from the TG-DTG curves by both the Achar method and the Coats-Redfern method with 15 frequently cited basic kinetic models. The dynamic dehydration processes for steps 1 and 2 were best expressed by the Zhuralev-Lesokin-Tempelman equation, suggesting a three-dimensional diffusion-controlled mechanism.
In this paper, α-MnO2 micronests composed of nanowires were fabricated via a hydrothermal reaction of MnSO4·H2O and K2S2O8 solutions. The α-MnO2 micronests were demonstrated to have a higher adsorption capacity than γ-MnO2 microspheres due to their large specific surface area. The amount of Congo red adsorbed per unit weight of α-MnO2 micronests increased significantly from 114 to 282 mg·g-1 with concentration of Congo red solution increasing from 50 to 200 mg·L-1, but it had a little change with temperature. Kinetics, isotherms and thermodynamics for the adsorption of Congo red on α-MnO2 micronests were examined. The adsorption process followed the pseudo-second-order kinetics with good correlation. The experimental data were analyzed by Langmuir and Freundlich models, and equilibrium data fitted the Langmuir isotherm very well with maximum monolayer adsorption capacity of 625 mg·g–1 at 22 °C. The adsorption was spontaneous and endothermic according to thermodynamic studies. The experimental results indicate that α-MnO2 micronests possess a high adsorption capacity and could be employed as a replacement of traditional sorbents.
Micro-combustion initiated by dielectric barrier discharge plasma has been applied for the removal of carbon template to prepare urchin-like ZnO particles. The combustion is operated at atmospheric pressure and low gas temperature (less than 150 °C), and the template is fully decomposed and rapidly removed. The obtained urchin-like ZnO possesses two distinct morphologies: nanosheets and sub-micro rods. The unique morphologies form on ZnO hexagonal nuclei with the template effect of activated carbon.
Ni(II) ions were removed from aqueous waste using micellar enhanced ultrafiltration (MEUF) with a mixture of surfactants. The surfactant mixture was the nonionic surfactant Tween 80 (TW80) mixed with the anionic surfactant sodium dodecyl sulfate (SDS) in different molar ratios ranging from 0.1–1.5. The operational variables of the MEUF process such as pH, applied pressure, surfactant to metal ion ratio and nonionic to ionic surfactant molar ratio (α) were evaluated. Rejection of Ni and TW80 was 99% and 98% respectively whereas that for SDS was 65%. The flux and all resistances (fouling resistance, resistance due to concentration polarization) were measured and calculated for entire range of α respectively. A calculated flux was found to be declined with time, which was mainly attributed to concentration polarization rather than resistance from membrane fouling.
To improve their thermal stability, La0.8Sr0.2MnO3 cordierite monoliths are washcoated with mayenite, which is a novel Al-based material with the crystal structure of 12MO·7Al2O3 (M= Ca, Sr). The monoliths are characterized by means of nitrogen adsorption/desorption, scanning electron microscopy, and X-ray diffraction. Catalytic performances of the monoliths are tested for methyl methacrylate combustion. The results show that mayenite obviously improves both the physic-chemical properties and the catalytic performance of the monoliths. Because mayenite improves the dispersity of La0.8Sr0.2MnO3 and also prevents the interaction between La0.8Sr0.2MnO3 and cordierite or
Titanium-containing mesoporous materials (Ti-MCM-41) were obtained by hydrothermal synthesis. Such materials are active catalysts for the transesterification of dimethyl oxalate and phenol to produce diphenyl oxalate. To understand the role of the Ti in the catalytic process, Ti-MCM-41 samples with different Si/Ti ratios (from 5 to 100) were prepared and the samples were analyzed by Fourier transform infrared spectroscopy, UV-visible spectroscopy, and ammonia temperature programmed desorption. It was concluded that the Ti is incorporated into the framework of the MCM-41 and formed weak Lewis acid sites. In addition, the number of Ti(IV) sites increased as the amount of titanium increased. X-ray powder diffraction, N2 adsorption-desorption and transmission electron microscopy results showed that the Ti-MCM-41 samples have a hexagonal arrangement of mono-dimensional pores. A large number of Ti(IV) sites coupled with the mesoporous structure and large pore diameters are favorable for the transesterification catalytic properties of Ti-MCM-41.
The particle formation mechanism of hydroxyapatite precursor containing two components, Ca(OOCCH3)2 and (NH4)2HPO4 with a ratio of Ca/P= 1.67, in a spray pyrolysis process has been studied by computational fluid dynamics (CFD) simulation on the transfer of heat and mass from droplets to the surrounding media. The focus included the evaporation of the solvent in the droplets, a second evaporation due to crust formation, the decomposition reaction of each component of the precursor, and a solid-state reaction that included the kinetic parameters of the precursor regarding its two components that formed the hydroxyapatite product. The rate of evaporation and the reacted fraction of the precursor both increased with temperature. The predicted average size of the hydroxyapatite particles agreed well with the experimental results. Therefore, the selected models were also suitable for predicting the average size of particles that contain two components in the precursor solution.
Magnetic Fe3O4 and mesoporous silica core-shell nanospheres with tunable size from 110–800 nm were synthesized via a one step self-assembly method. The morphological, structural, textural, and magnetic properties were well-characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, N2 adsorption-desorption and magnetometer. These nanocomposites, which possess high surface area, large pore volume and well-defined pore size, exhibit two dimensional hexagonal (
This paper focuses on modeling and simulation of a post-combustion carbon dioxide capture in a coal-fired power plant by chemical absorption using monoethanolamine. The aim is to obtain a reliable tool for process simulation: a customized rate-based model has been developed and implemented in the ASPEN Plus® software, along with regressed parameters for the Electrolyte-NRTL model worked out in a previous research. The model is validated by comparison with experimental data of a pilot plant and can provide simulation results very close to experimental data.
