Jiun Horng Tsai

Adsorption characteristics of acetone, chloroform and acetonitrile on sludge-derived adsorbent, commercial granular activated carbon and activated carbon fibers

The adsorption characteristics of chloroform, acetone, and acetonitrile on commercial activated carbon (C1), two types of activated carbon fibers (F1 and F2), and sludge adsorbent (S1) was investigated. The chloroform influent concentration ranged from 90 to 7800 ppm and the acetone concentration from 80 to 6900 ppm; the sequence of the adsorption capacity of chloroform and acetone on adsorbents was F2>F1 approximately C1 approximately S1. The adsorption capacity of acetonitrile ranged from 4 to 100 mg/g, corresponding to the influent range from 43 to 2700 ppm for C1, S1, and F1. The acetonitrile adsorption capacity of F2 was approximately 20% higher than that of the other adsorbents at temperatures<30 degrees C. The Freundlich equation fit the data better than the Langmuir and Dubinin-Radushkevich (D-R) equations. The adsorption rate of carbon fibers is higher than that of the other adsorbents due to their smaller fiber diameter and higher surface area. The micropore diffusion coefficient of VOC on activated carbon and sludge adsorbent was approximately 10(-4) cm2 s(-1). The diffusion coefficient of VOC on carbon fibers ranged from 10(-8) to 10(-7) cm2 s(-1). The small carbon fiber pore size corresponds to a smaller diffusion coefficient.

VOC concentration characteristics in Southern Taiwan.

The field investigations were conducted at four air quality monitoring sites in Southern Taiwan during northeasterly prevailing monsoon to collect 160 data sets on volatile organic compounds (VOCs) to evaluate the ozone formation potential (OFP) of the air mass. The gas chromatograph and high performance liquid chromatography analyzed 58 VOCs and two aldehydes, respectively. Among the four sampling sites, the order of the five VOC classes based on the reactivity approach was different from the concentration-based method. Alkenes as well as aromatics provided a major contribution for the OFP. The relative ranking of the species at the four sites were quite dissimilar. Toluene was the most in abundance at each site. The most abundant species at the windward and leeward sites was different. The reactivity of the air mass at the leeward sites showed a similar pattern and had higher reactivity than the windward sites. Comparisons of the two ratios, xylene/benzene and toluene/benzene were used to assess the relative age of the air parcels and provide evidence of transport.

The speciation of volatile organic compounds (VOCs) from motorcycle engine exhaust at different driving modes

Abstract This study investigated the emissions of volatile organic compound (VOC) from motorcycle engine exhaust at different driving modes on a dynamometer. The speciations and the ozone formation potential of VOC samples also had been investigated by GC/MS and maximum increment reactivity (MIR), respectively. Both brand new and in-use motorcycles were tested in this study. The tested motorcycles include 2-stroke and 4-stroke engines. There are totally 48 VOC compounds identified in this study. Only the VOC species with C 3 –C 9 were identified successfully. Experimental results indicated that isopentane, toluene, m , p -xylene, n -pentane, 2-methylpentane, 3-methylpentane, benzene, n -heptane and methylheptane were the major VOC speciations in the motorcycle engine exhaust. The amount of VOC emissions of the in-use 2-stroke motorcycles was 5 times that of the new 2-stroke motorcycles and the in-use 4-stroke motorcycles was 15 times that of the new 4-stroke motorcycles during the whole cycle. The amount of VOC speciation concentration during idle and deceleration stages was higher than those during the acceleration and cruising modes. However, the emission rate of VOCs at various driving modes tested on a dynamometer had not been precised enough due to the inconsistent variation of volume efficiency of motorcycle engine. These data shows a clear distinct emission rate of VOC at various driving modes. Besides, alkanes and aromatics were the major VOC speciation groups in the motorcycle engine exhaust. The amount of VOCs contributed from 23% to 76% THC for the four types motorcycle. Great variation of VOC/THC were found among new and in-use motorcycle. The ozone formation potential of a 2-strokes engine was higher than that of a 4-stroke engine. The ozone formation potential of in-use motorcycles were also clear higher than those of new motorcycles.

Source impacts by volatile organic compounds in an industrial city of southern Taiwan

This study investigates source impacts by airborne volatile organic compounds (VOC) at two sites designated for traffic and industry, in the largest industrial area Kaohsiung, southern Taiwan. The samples were collected at the two sites simultaneously during rush and non-rush hours in summer and autumn seasons. Same pattern of VOC groups were found at both sites: most abundant aromatics (78-95%) followed by alkanes (2-16%) and alkenes (0-6%). The BTEX concentration measured at the two sites ranged from 69 to 301 ppbC. Toluene, isopentane, ethylbenzene, and benzene were found to be the most abundant species. Speciation of VOCs was characterized with several skills including principal component factor analysis and BTEX characteristic ratios. Each of the resulted principal factors at the two sites explained over 80% of the VOCs data variance, and indicated that both of the sampling sites were influenced by both traffic and industrial sources with separately different levels. The remarkable patterns of the first two factors described not only the similarity but also the discrepancy at the two sampling sites, in terms of the source impacts. The high T/B ratios (7.56-14.25) observed at the industrial site implied the important impact from mobile emissions. The indicators, m,p-xylene/benzene and o-xylene/benzene, also confirmed the potential source of motor vehicles at both of the sampling sites. Air age assessment showed that more than half of the total observations located in the domain of fresh air. Low X/E ratios implied somewhat aged air mass transported to the sampling sites. The industrial site might not only encounter emissions from the industry sources, but also under unavoidable impact from the traffic sources.

Removal of H2S from Exhaust Gas by Use of Alkaline Activated Carbon

The purpose of this research was to select an activated carbon and alkaline solution blend that generated the best H2S adsorption on alkaline-activated carbon. RB2 (activated carbon) impregnated with NaOH solution was shown to have the optimum H2S removal efficiency. The optimum NaOH concentration was 50 mg per gram of carbon. H2S adsorption via RB2-NaOH50 was five times that of a corresponding fresh-activated carbon. The adsorption equivalent of H2S is nearly 1 (mol-H2S/mol-AOH), therefore, H2S + AOH → AHS + H2O was the major reaction. The H2S adsorption isotherm corresponded to the Freundlich isotherm.

Adsorption Characteristics of Alkaline Activated Carbon Exemplified by Water Vapor, H2S, and CH3SH Gas

Activated carbon adsorption is an widely used process in environmental engineering. Alkaline impregnated activated carbon has been used to enhance the adsorption capacity for odorous compounds from gas streams. This study investigated the physicochemical and adsorption characteristics of one virgin and four alkaline-impregnated activated carbon samples. The four alkaline additives were NaOH, Na2CO3, KOH, and K2CO3 and the impregnated activated carbons were referred to as NaOH-IAC, Na2CO3-IAC, and KOH-IAC, K2CO3-IAC. The specific surface area, micropore area, and micropore volumes were reduced in the impregnated activated carbon systems. The adsorption capacity of H2S and CH3SH increased. This indicated that the physical properties were not the predominant influence on adsorption behavior. The impregnated activated carbons were ranked NaOH Na2CO3 KOH K2CO3 for H2S adsorption. The NaOH-IAC demonstrated 3.2 and 2.2 times the adsorption capacity for H2S and CH3SH, respectively, compared to the virgin AC sample. Increasing the vacuum and immersion duration increased the alkaline quantity of NaOH impregnated on activated carbon. The NaOH-IAC50 (50 mg NaOH/g carbon) sample performed the best. It had 6.9 times the adsorption capacity of the virgin AC. The humidity that coexisted in the H2S and CH3SH gas streams enhanced the H2S and CH3SH adsorption capacity of NaOH-IAC. At 50% relative humidity and 50 ppm H2S, the NaOH-IAC sample exhibited the maximum adsorption capacity for H2S. This carbon attained 30.3 times more capacity than the virgin AC.

Effects of ethanol-blended gasoline on air pollutant emissions from motorcycle

The effect of ethanol-gasoline blends on criteria air pollutant emissions was investigated in a four-stroke motorcycle. The ethanol was blended with unleaded gasoline in four percentages (3, 10, 15, and 20% v/v) and controlled at a constant research octane number, RON (95), to accurately represent commercial gasoline. CO, THC, and NOx emissions were evaluated using the Economic Commission for Europe cycle on the chassis dynamometers. The results of the ethanol-gasoline blends were compared to those of commercial unleaded gasoline with methyl tert-butyl ether as the oxygenated additive. In general, the exhaust CO and NOx emissions decreased with increasing oxygen content in fuels. In contrast, ethanol added in the gasoline did not reduce the THC emissions for a constant RON gasoline. The 15% ethanol blend had the highest emission reductions relative to the reference fuel. The high ethanol-gasoline blend ratio (20%) resulted in a less emission reduction than those of low ratio blends (<15%). This may be attributed to the changes in the combustion conditions in the carburetor engine with 20% ethanol addition. Furthermore, the influence of ethanol-gasoline blends on the reduction of exhaust emissions was observed at different driving modes, especially at 15km/h cruising speed for CO and THC and acceleration stages for NOx.

Diffusion of hydrogen sulfide and methyl mercaptan onto microporous alkaline activated carbon

Activated carbon kinetic studies show that both H2S and CH3SH yielded pore diffusion coefficients from 10(-6) to 10(-8) cm2/s. Results indicated that pore structures could influence effective diffusivity. Under the same adsorbate concentration, CH3SH exhibited a greater effective pore diffusion coefficient than H2S. This may be attributed to the fact that CH3SH has both polar (-SH) and non-polar (-CH3) functional groups and dissolves into water easier, thus providing more attraction for the activated carbon surface. In addition, the saturation vapor pressure of CH3SH is lower than that of H2S. Therefore, CH3SH is easier to adsorb onto activated carbon than H2S.

Tunnel study of on-road vehicle emissions and the photochemical potential in Taiwan.

Motor vehicle emission factors of carbon monoxide (CO) and non-methane volatile organic compounds (NMVOCs) were calculated inside the Chung-Cheng Tunnel of Kaohsiung in Taiwan. The results were compared with those model predictions from the Mobile Taiwan 2.0 model. Individual concentrations of 21 species of NMVOCs were also determined. Photochemical potential of NMVOCs was evaluated by using the maximum incremental reactivity (MIR). Field data showed that the integrated emission factors of CO and NMVOCs for actual fleet were 6.3 and 1.5 g/veh km, respectively. The error range of these factors may be up to 45%. The predicted values by the Mobile Taiwan 2.0 model closely matched the observed data. Concentrations of isopentane, 2-methylpentane, toluene and m,p-xylene were the dominant species of NMVOCs. The ratio of maximum incremental reactivity to NMVOCs concentration was 3.9, similar to those of the studies in the US Fort McHenry and Tuscarora Tunnel.

Volatile organic compound constituents from an integrated iron and steel facility

This study measured the volatile organic compound (VOC) constituents of four processes in an integrated iron and steel industry; cokemaking, sintering, hot forming, and cold forming. Toluene, 1,2,4-trimethylbenzene, isopentane, m,p-xylene, 1-butene, ethylbenzene, and benzene were the predominant VOC species in these processes. However, some of the chlorinated compounds were high (hundreds ppbv), i.e., trichloroethylene in all four processes, carbon tetrachloride in the hot forming process, chlorobenzene in the cold forming process, and bromomethane in the sintering process. In the sintering process, the emission factors of toluene, benzene, xylene, isopentane, 1,2,4-trimethylbenzene, and ethylbenzene were over 9 g/tonne-product. In the vicinity of the manufacturing plant, toluene, isopentane, 1,2,4-trimethylbenzene, xylene and ethylbenzene were high. Toluene, 1,2,4-trimethylbenzene, xylene, 1-butene and isopentane were the major ozone formation species. Aromatic compounds were the predominant VOC groups, constituting 45-70% of the VOC concentration and contributing >70% to the high ozone formation potential in the stack exhaust and workplace air. The sequence of VOC concentration and ozone formation potential was as follows: cold forming>sintering>hot forming>cokemaking. For the workplace air, cokemaking was the highest producer, which was attributed to the fugitive emissions of the coke oven and working process release.