Dingsheng Chen

Carbonaceous Adsorbents Prepared from Sewage Sludge and Its Application for Hg0 Adsorption in Simulated Flue Gas

Abstract The carbonaceous adsorbent was prepared from mixtures of dewatered sludge and sawdust with enhanced ZnCl 2 chemical activation. Characteristics of the adsorbent were studied using scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), and adsorption of nitrogen. The surface analysis showed that the carbonaceous adsorbent had good specific surface and porosity (394 m 2 ·g −1 of BET surface, 0.12 and 0.10 ml·g −1 of microporous and mesoporous volume, respectively). The oxygen functional groups such as OH, C O and C O were found on the surface by FTIR and XPS (X-ray photoelectron spectroscopy). The adsorption of elemental mercury (Hg 0 ) on the carbonaceous adsorbent was studied in a fixed bed reactor. The dynamic adsorption capacity of carbonaceous adsorbent increased with influent mercury concentration, from 23.6 μg·g −1 at 12.58 μg·m −3 to 87.9 μg·g −1 at 72.50 μg·m −3 , and decreased as the adsorption temperature increased, from 246 μg·g —1 at 25°C to 61.3 μg·g −1 at 140 °C, when dry nitrogen was used as the carrier gas. The carbonaceous adsorbent presented higher dynamic adsorption capacity than activated carbon, which was 81.2 μg·g —1 and 53.8 μg·g −1 respectively. The adsorption data were fitted to the Langmuir adsorption model. The physical and chemical adsorption were identified on the adsorbent.

The key role of ph value in the synthesis of titanate nanotubes-loaded manganese oxides as a superior catalyst for the selective catalytic reduction of NO with NH 3

Titanate nanotubes (TNTs) synthesized by hydrothermal method were increasingly used as the catalyst support for the selective catalytic reduction (SCR) of NO with ammonia. This paper reports the critical process of postwashing to prepare satisfactory TNTs for the uses of SCR catalysts. Herein, alkaline TNTs (TNTs-AL), acidic TNTs (TNTs-AC), and neutral TNTs (TNTs-NE) were synthesized by controlling washing pH value. When these TNTs were utilized as the catalyst supports for manganese oxides (Mn/TNTs-AL, Mn/TNTs-AC, and Mn/TNTs-NE), the key role of pH value was found. Titanate nanosheets, titanate nanorods and titanate nanotubes were dominated in Mn/TNTs-AL, Mn/TNTs-AC, and Mn/TNTs-NE, respectively. MnO2 crystal was observed when using TNTs-AC or TNTs-NE as the support. By contrast, Mn3O4 and NaNO3 were observed when using TNTs-AL as the support. Mn/TNTs-NE showed the best SCR activity, in line with the largest surface area, the best dispersion, and the most active redox property of manganese oxides. Mn/TNTs-AL showed negligible SCR activity, resulting from the minimum surface area, the Mn3O4-dominating crystal structure, and the bad dispersion of manganese oxides.

Synthesis of zeolite nanocrystals with intercrystal mesopores using an organosilane as the structure directing agent

Nanocrystalline ZSM-5 with mesoporosity was synthesized within a short reaction time using triethoxyphenylsilane as the mesopore structure directing agent via a direct one-step hydrothermal method. With the addition of the organosilane, the growth of the zeolite grain was restrained, which led to the formation of intercrystal mesoporosity. These zeolite nanocrystals are designed to enhance the adsorption properties by increasing porosity. Their adsorption performance was measured via the static adsorption method with toluene as a model gas on an intelligent gravimetric analyzer.

Modified fly ash from municipal solid waste incineration as catalyst support for Mn-Ce composite oxides

Fly ash from municipal solid waste incineration was modified by hydrothermal treatment and used as catalyst support for Mn-Ce composite oxides. The prepared catalyst showed good activity for the selective catalytic reduction (SCR) of NO by NH3. A NO conversion of 93% could be achieved at 300 °C under a GHSV of 32857 h-1. With the help of characterizations including XRD, BET, SEM, TEM, XPS and TPR, it was found that hydrothermal treatment brought a large surface area and abundant mesoporous to the modified fly ash, and Mn-Ce composite oxides were highly dispersed on the surface of the support. These physical and chemical properties were the intrinsic reasons for the good SCR activity. This work transformed fly ash into high value-added products, providing a new approach to the resource utilization and pollution control of fly ash.

Experimental Study on the Absorption of Toluene from Exhaust Gas by Paraffin/Surfactant/Water Emulsion

A new paraffin/surfactant/water emulsion (PSW) for volatile organic compounds (VOCs) controlling was prepared and its potential for VOCs removal was investigated. Results indicated that PSW-5 (5%, v/v) provided higher toluene absorption efficiency (90.77%) than the other absorbents used. The saturation pressure, Henry’s constant, and activity coefficient of toluene in PSW-5 were significantly lower than those in water, and toluene solubility (1.331 g·L−1) in the PSW-5 was more than 2.5 times higher than the value in water. Several factors potentially affecting the toluene absorption efficiency were systematically investigated. The results suggested that concentration and pH of PSW, absorption temperature, and gas flow rate all had a strong influence on the toluene absorption, but the inlet concentration of toluene had little effect on the toluene absorption. There were different absorbing performances of PSW-5 on different VOCs, and the ketones, esters, and aromatics were more easily removed by the PSW-5 than the alkanes. Regeneration and reuse of the PSW were possible; after 3 runs of regeneration the absorption efficiency of PSW-5 for toluene also could reach 82.42%. So, the PSW is an economic, efficient, and safe absorbent and has a great prospect in organic waste gas treatment.