Chungsying Lu

Capture of CO2 from flue gas via multiwalled carbon nanotubes

Carbon nanotubes (CNTs) were modified by 3-aminopropyl-triethoxysilane (APTS) solution and were tested for its CO2 adsorption potential at multiple temperatures (20-100 degrees C). The physicochemical properties of CNTs were changed after the modification, which makes CNTs adsorb more CO2 gases. The adsorption capacities of CO2 via CNTs and CNTs(APTS) decreased with temperature indicating the exothermic nature of adsorption process and increased with water content in air at 0-7%. The mechanism of CO2 adsorption on CNTs and CNTs(APTS) appears mainly attributable to physical force regardless of temperature change, which makes regeneration of spent CNTs at a relatively low temperature become feasible. The CNTs(APTS) have good adsorption performance of CO2 at 20 degrees C as compared to many types of modified carbon or silica adsorbents documented in the literature. This suggests that the CNTs(APTS) are promising low-temperature adsorbents for CO2 capture from flue gas.

A model for chlorine concentration decay in pipes

Abstract A model that accounts for transport in the axial direction by convection and in the radial direction by diffusion and that incorporates first order decay kinetics has been developed to predict the chlorine concentration in a pipe in a distribution system. A generalized expression for chlorine consumption at the pipe wall is used to solve the governing equation and to determine the average chlorine concentration at any location in the pipe. Three non-dimensional parameters are used to determine the concentration and a methodology to determine them in pipe networks is proposed. The range of values of these dimensionless parameters where wall consumption is significant are determined. The methodology is applied to field measurements of chlorine concentration in a distribution network.

Effects of pH, moisture, and flow pattern on trickle-bed air biofilter performance for BTEX removal

Abstract Effects of pH, moisture and flow pattern on the performance of a trickle-bed air biofilter (TBAB) treating benzene, toluene, ethylbenzene and o -xylene (BTEX) waste gas were investigated to establish the optimum operating conditions and design criteria. In the pH range of 7.5–8 and NFR range of 6.02–8.6 l/m 3 /h, removal efficiencies of each compound were greater than 80% with a loading of 143 g BTEX/m 3 /h. The TBAB appears to be an effective process for controlling BTEX emission with a high loading. Counter-current flow TBAB has the advantages of more uniform BTEX removal and biomass growth in each section than co-current flow TBAB, but suffers from a higher pressure drop across the bed.

Adsorption, desorption, and thermodynamic studies of CO2 with high-amine-loaded multiwalled carbon nanotubes.

Commercially available multiwalled carbon nanotubes (CNTs) were functionalized with a high mass load of 3-aminopropyltriethoxysilane (APTS) to study their behaviors in the cyclic CO(2) adsorption as well as the associated thermodynamic properties. The breakthrough curve showed a fast kinetics of CO(2) adsorption resulting in percentage ratios of working capacity to equilibrium capacity greater than 80%. The adsorption capacity of CNT(APTS) was significantly influenced by the presence of water vapor and reached a maximum of 2.45 mmol/g at a water vapor of 2.2%. The adsorption capacities and the physicochemical properties of CNT(APTS) were preserved through 100 adsorption-desorption cycles displaying the stability of CNT(APTS) during a prolonged cyclic operation. The heat input required to regenerate spent CNT(APTS) was determined, and the result suggests that adsorption process with solid CNT(APTS) is possibly a promising CO(2) capture technology.

Removal of BTEX vapor from waste gases by a trickle bed biofilter.

ABSTRACT The system performance of a trickle bed biofilter for treating single and mixed benzene, toluene, ethylbenzene, and o-xylene (BTEX) vapors from waste gases was investigated under different gas flow rates and influent BTEX concentrations. When a single substrate was fed, removal efficiencies of greater than 90% could be achieved for the loads below 64 g benzene/m3/hr, 110 g toluene/mVhr, 53 g ethylbenzene/m3/hr, and 55 g o-xylene/m3/hr. When a mixed substrate was fed, removal efficiencies of each compound could be above 90% at BTEX loads below 96 g/m3/hr. The trickle bed biofilter appears to be an effective treatment process for removing both single and mixed BTEX vapors with low to high loads. Under similar substrate loads, BTEX vapors were preferentially bio-degraded in the order of toluene, benzene, o-xylene, and ethylbenzene. The volumetric removal rates (elimination capacities) of BTEX vapors for a single-substrate feed were higher than those for a mixed-substrate feed under similar substrate loads; these differences were enhanced at higher substrate loads and less significant for a preferred substrate.

Simultaneous transport of substrates, disinfectants and microorganisms in water pipes

Abstract A mathematical model that accounts for simultaneous transport of substrates, disinfectants and microorganisms has been developed to predict substantial changes in quality of distributed water. The model consists of a set of mass balance equations for organic substances, ammonium nitrogen, oxidized nitrogen, dissolved oxygen, alkalinity, biomass, and disinfectants in the bulk liquid phase and within the biofilm under laminar and turbulent flow conditions. This model is validated by comparing its solutions with the numerical solutions in the literature and then is applied for predicting the behavior of a typical water treatment plant effluent through a distribution pipe. The flow properties and disinfectant consumption rate at the pipe wall play a significant role in the determination of potable water quality in the distribution system.

Removal of styrene vapor from waste gases by a trickle-bed air biofilter

The trickle-bed air biofilter (TBAB) performance for the removal of high-strength styrene was evaluated under different gas flow rates and influent concentrations. Under pseudo-steady-state conditions, the elimination capacity increased but the removal efficiency decreased with the increase of styrene loading. More than 90 and 80% removal efficiencies were achieved for influent styrene loadings below 32 and 55g/m(3)/h, respectively. The TBAB appears to be an effective treatment process for controlling high-strength styrene emission under low-to-medium loading conditions, and the effectiveness could be maintained over 140 days of laboratory operation.

Biofiltration of isopropyl alcohol and acetone mixtures by a trickle-bed air biofilter

Abstract The performance of a trickle-bed air biofilter (TBAB) treating isopropyl alcohol (IPA) and acetone (ACE) mixtures was investigated under different gas flow rates and influent concentrations. In pseudo-steady-state conditions, the elimination capacities of IPA and ACE increased but the removal efficiencies decreased with increased influent carbon loading. The removal efficiencies of IPA were higher than those of ACE, indicating that IPA is a preferred substrate in the IPA and ACE mixtures. More than 90% removal efficiencies were achieved with influent carbon loadings of IPA and ACE below 80 and 53 g/m 3 ·h, respectively. The TBAB appears efficient for controlling mixed IPA and ACE emission with low to medium carbon loadings. Applicable operating conditions of TBAB for treating mixed IPA and ACE emission were suggested.

Solubility of heavy metals added to MSW.

This paper aims to investigate the six heavy metal levels (Cd, Cr, Cu, Pb, Ni and Zn) in municipal solid waste (MSW) at different pHs. It intends to provide the baseline information of metals solubility in MSW co-disposed or co-digested with MSW incinerator ashes in landfill or anaerobic bioreactors or heavy metals contaminated in anaerobic digesters. One milliliter (equal to 1mg) of each metal was added to the 100ml MSW and the batch reactor test was carried out. The results showed that higher HNO3 and NaOH were consumed at extreme pH of 1 and 13 compared to those from pH 2 to 11 due to the comparably higher buffer capacity. Pb was found to have the least soluble level, highest metal adsorption (%) and highest partitioning Kd (lg(-1)) between pH 3 and 12. In contrast, Ni showed the highest soluble level, lowest metal adsorption (%) and lowest Kd (lg(-1)) between pH 4 and 12. Except Ni and Cr, other four metals seemed to show the amphibious properties as comparative higher solubility was found in the acidic and basic conditions.

Adsorption of carbon dioxide from gas streams via mesoporous spherical-silica particles.

Abstract A relatively new mesoporous silica sorbent for environmental protection applications (i.e., mesoporous spherical-silica particles [MSPs]), was modified by N-[3-(trimethoxysilyl)propyl]ethylenediamine (EDA) solution and was tested for its potential in the separation of carbon dioxide (CO2) from flue gas. The CO2 adsorption capacity of MSP and MSP(EDA) increased with temperature from 20 to 60 °C but decreased with temperature from 60 to 100 °C. The mechanism of CO2 adsorption on both samples is mainly attributed to physical interaction regardless of temperature change. The MSP(EDA) have good adsorption performance as compared with EDA-modified zeolite or granular activated carbon conducted in this study and many types of silica sorbents reported in the literature. The cyclic CO2 adsorption showed that spent MSP(EDA) could be effectively regenerated at 120 °C for 25 min and CO2 adsorption capacity of MSP(EDA) was preserved during 16 cycles of adsorption and thermal regeneration. These results suggests that MSP(EDA) are efficient CO2 sorbents and can be stably used in the prolonged cyclic operation.