Wet Etching of Silicon in Planar Nanochannels.

Silicon (Si) alkaline etching constitutes a fundamental process in the semiconductor industry. Although its etching kinetics on plain substrates have been thoroughly investigated, the kinetics of Si wet etching in nanoconfinements have yet to be fully explored despite its practical importance in three-dimensional (3-D) semiconductor manufacturing. Herein, we report the systematic study of potassium hydroxide (KOH) wet etching kinetics of amorphous silicon (a-Si)-filled two-dimensional (2-D) planar nanochannels. Our findings reveal that the etching rate would increase with the increase in nanochannel height before reaching a plateau, indicating a strong nonlinear confinement effect. Through investigation using etching solutions with different ionic strengths and/or different temperatures, we further find that both electrostatic interactions and the hydration layer inside the nanoconfinement contribute to the confinement-dependent etching kinetics. Our results offer fresh perspectives into the kinetic study of reactions in nanoconfinements and will shed light on the optimization of etching processes in the semiconductor industry.

Metagenomic analysis of microbial community structure and function in a improved biofilter with odorous gases.

Biofilters have been broadly applied to degrade the odorous gases from industrial emissions. A industrial scale biofilter was set up to treat the odorous gases. To explore biofilter potentials, the microbial community structure and function must be well defined. Using of improved biofilter, the differences in microbial community structures and functions in biofilters before and after treatment were investigated by metagenomic analysis. Odorous gases have the potential to alter the microbial community structure in the sludge of biofilter. A total of 90,016 genes assigned into various functional metabolic pathways were identified. In the improved biofilter, the dominant phyla were Proteobacteria, Planctomycetes, and Chloroflexi, and the dominant genera were Thioalkalivibrio, Thauera, and Pseudomonas. Several xenobiotic biodegradation-related pathways showed significant changes during the treatment process. Compared with the original biofilter, Thermotogae and Crenarchaeota phyla were significantly enriched in the improved biofilter, suggesting their important role in nitrogen-fixing. Furthermore, several nitrogen metabolic pathway-related genes, such as nirA and nifA, and sulfur metabolic pathway-related genes, such as fccB and phsA, were considered to be efficient genes that were involved in removing odorous gases. Our findings can be used for improving the efficiency of biofilter and helping the industrial enterprises to reduce the emission of waste gases.

[Removal of toluene from waste gas by honeycomb adsorption rotor with modified 13X molecular sieves].

The removal of toluene from waste gas by Honeycomb Adsorption Rotor with modified 13X molecular sieves was systematically investigated. The effects of the rotor operating parameters and the feed gas parameters on the adsorption efficiency were clarified. The experimental results indicated that the honeycomb adsorption rotor had a good humidity resistance. The removal efficiency of honeycomb adsorption rotor achieved the maximal value with optimal rotor speed and optimal generation air temperature. Moreover, for an appropriate flow rate ratio the removal efficiency and energy consumption should be taken into account. When the recommended operating parameters were regeneration air temperature of 180 degrees C, rotor speed of 2.8-5 r x h(-1), flow rate ratio of 8-12, the removal efficiency kept over 90% for the toluene gas with concentration of 100 mg x m(-3) and inlet velocity of 2 m x s(-1). The research provided design experience and operating parameters for industrial application of honeycomb adsorption rotor. It showed that lower empty bed velocity, faster rotor speed and higher temperature were necessary to purify organic waste gases of higher concentrations.

[Treatment of organic waste gas by adsorption rotor].

The adsorption rotor is applicable to treating organic waste gases with low concentration and high air volume. The performance of adsorption rotor for purifying organic waste gases was investigated in this paper. Toluene was selected as the simulative gaseous pollutant and the adsorption rotor was packed with honeycomb modified 13X molecular sieves (M-13X). Experimental results of the fixed adsorption and the rotor adsorption were analyzed and compared. The results indicated that some information on the fixed adsorption was useful for the rotor adsorption. Integrating the characteristics of the adsorbents, waste gases and the structures of the rotor adsorption, the formulas on optimal rotor speed and cycle removal efficiency of the adsorption rotor were deduced, based on the mass and heat balances of the adsorbing process. The numerical results were in good agreement with the experimental data, which meant that the formulas on optimal rotor speed and cycle removal efficiency could be effectively applied in design and operation of the adsorption rotor.

Adsorption behavior of toluene on modified 1X molecular sieves.

UNLABELLED: In this paper, the toluene adsorption/desorption properties of modified 13X molecular sieves (M-13X) are discussed. M-13X molecular sieves were prepared by acidic and steam treatments of 13X molecular sieves. The structural parameters of M-13X were evaluated and compared with those of other molecular sieves (HY, HZSM-5, Cs7NaMOR, and a commercial 13X). The results show that the specific surface area, average pore diameter and pore volume of M-13X were 414.17 m2/g, 2.98 nm, and 0.31 mL/g, respectively. The pore size distribution of M-13X was 1.8-3.0 nm. Because of its larger Si/Al ratio (Si/Al = 6.77), the hydrophobicity of M-13X is much higher than that of 13X (Si/Al = 1.28), indicating that it is particularly well suited to toluene control applications. The saturation adsorption capacity of M-13X was 0.045 g/g for simulated toluene at a temperature of 293 K and a relative humidity of 50%. The optimal regeneration temperature of M-13X was 473 K for 120 min with a hot air flow rate of 140 L/min. IMPLICATIONS: The modified 13X molecular sieves (M-13X) are adsorbents with a high adsorption capacity and great hydrophobicity, suitable for the treatment of VOCs. The purpose of the present investigation is to provide a practical guide for their design.