Qing Ye

Carbon Dioxide Capture by Functionalized Solid Amine Sorbents with Simulated Flue Gas Conditions

A novel solid amine sorbent was prepared using KIT-6-type mesoporous silica modified with tetraethylenepentamine (TEPA). Its adsorption behavior toward CO(2) from simulated flue gases is investigated using an adsorption column. The adsorption capacities at temperatures of 303, 313, 333, 343, and 353 K are 2.10, 2.29, 2.58, 2.85, and 2.71 mmol g(-1), respectively. Experimental adsorption isotherms were obtained, and the average isosteric heat of adsorption was 43.8 kJ/mol. The adsorption capacity increases to 3.2 mmol g(-1) when the relative humidity (RH) of the simulated flue gas reaches 37%. The adsorption capacity is inhibited slightly by the presence of SO(2) at concentrations lower than 300 ppm but is not significantly influenced by NO at concentrations up to 400 ppm. The adsorbent is completely regenerated in 10 min at 393 K and a pressure of 5 KPa, with expected consumption energy of about 1.41 MJ kg(-1) CO(2). The adsorption capacity remains almost the same after 10 cycles of adsorption/regeneration with adsorption conditions of 10 vol % CO(2), 100 ppm SO(2), 200 ppm NO, 100% relative humidity, and a temperature of 393 K. The solid amine sorbent, KIT-6(TEPA), performs excellently for CO(2) capture and its separation from flue gas.

Amine-functionalized low-cost industrial grade multi-walled carbon nanotubes for the capture of carbon dioxide

Abstract Industrial grade multi-walled carbon nanotubes (IG-MWCNTs) are a low-cost substitute for commercially purified multi-walled carbon nanotubes (P-MWCNTs). In this work, IG-MWCNTs were functionalized with tetraethylenepentamine (TEPA) for CO2 capture. The TEPA impregnated IG-MWCNTs were characterized with various experimental methods including N2 adsorption/desorption isotherms, elemental analysis, X-ray diffraction, Fourier transform infrared spectroscopy and thermogravimetric analysis. Both the adsorption isotherms of IG-MWCNTs-n and the isosteric heats of different adsorption capacities were obtained from experiments. TEPA impregnated IG-MWCNTs were also shown to have high CO2 adsorption capacity comparable to that of TEPA impregnated P-MWCNTs. The adsorption capacity of IG-MWCNTs based adsorbents was in the range of 2.145 to 3.088 mmol/g, depending on adsorption temperatures. Having the advantages of low-cost and high adsorption capacity, TEPA impregnated IG-MWCNTs seem to be a promising adsorbent for CO2 capture from flue gas.

Promotion of Ag/H-BEA by Mn for Lean NO Reduction with Propane at Low Temperature

Effects of adding manganese to Ag/H-BEA for selective catalytic reduction of NO(x) with propane (C(3)H(8)-SCR) were investigated under a lean-burn condition. Mn addition significantly promotes the catalytic performance of Ag/H-BEA below 673 K. A Ag-Mn/H-BEA catalyst with equal metal weight of 3 wt % has the highest activity for C(3)H(8)-SCR among samples with a different bimetal loading. Manganese is mainly present in the 3+ and 4+ oxidation states in Ag-Mn/H-BEA catalysts. The major contributions of manganese suggested by the data presented in this paper are to catalyze the NO oxidation and stabilize silver in a dispersed Ag(+) state. The presence of silver enforces the transformation of a certain amount of Mn(3+) ions to Mn(4+) ions. The activity of Ag-Mn/H-BEA decreases slightly at low SO(2) concentrations (0-200 ppm) but decreases significantly at high SO(2) concentrations (400-800 ppm). In the presence of 10% H(2)O and 200 ppm SO(2), the inhibition of C(3)H(8)-SCR below 673 K is more significant than that at high temperature above 673 K. Ag-Mn/H-BEA is a promising catalyst for the removal of NO(x) from diesel engine exhaust.

A novel dielectric barrier discharge reactor with photocatalytic electrode based on sintered metal fibers for abatement of xylene

A novel dielectric barrier discharge (DBD) reactor was made for the abatement of xylene. This reactor has a photocatalytic electrode prepared by a modified anodic oxidation method which was proposed in this work. The photocatalytic electrode has nano-TiO(2) deposited on sintered metal fiber (SMF). The reactor using the nano-TiO(2)/SMF electrode shows much better performance in abating xylene compared with reactors using other electrodes such as resistance wire or SMF. The conversion ratio of xylene reaches 92.7% in the novel reactor at a relatively voltage (23.6 kV). This ratio is much higher than the conversion ratios of xylene in the traditional reactors with resistance wire or SMF electrodes, which are ~64.7%. The selectivity of CO(2) of the reactor using the nano-TiO(2)/SMF electrode (300 pps, 23.6 kV) was observed to be 86.6%, which is about twice as large as that of a traditional reactor using a resistance wire electrode. If a traditional DBD reactor is replaced by the novel reactor, at the same specific input energy, the energy yield can increase from 0.391 to 0.556 mg/kJ. Finally, the xylene decomposition mechanism with the nano-TiO(2)/SMF electrode was also briefly discussed.

Microstructure and antioxidative capacity of the microalgae mutant Chlorella PY-ZU1 during tilmicosin removal from wastewater under 15% CO2

The response mechanisms of microalgal mutant Chlorella PY-ZU1 cells were investigated in their removal of antibiotic tilmicosin from wastewater under 15% CO2. Low concentrations (0.01-2mgL-1) of tilmicosin in wastewater stimulated the growth of microalgal cells, whereas high concentrations (5-50mgL-1) of tilmicosin significantly inhibited cell growth. When initial tilmicosin concentration increased from 0 to 50mgL-1, fractal dimension of microalgal cells monotonically increased from 1.36 to 1.62 and cell size monotonically decreased from 4.86 to 3.75μm. In parallel, malondialdehyde content, which represented the degree of cellular oxidative damage, monotonically increased from 1.92×10-7 to 7.07×10-7 nmol cell-1. Superoxide dismutase activity that represented cellular antioxidant capacity first increased from 2.59×10-4 to the peak of 6.60×10-4U cell-1, then gradually decreased to 2.39×10-4U cell-1. The maximum tilmicosin removal efficiency of 99.8% by Chlorella PY-ZU1 was obtained at the initial tilmicosin concentration of 50mgL-1.

In vivo kinetics of lipids and astaxanthin evolution in Haematococcus pluvialis mutant under 15% CO2 using Raman microspectroscopy

In vivo spatiotemporal dynamics of lipids and astaxanthin evolution in Haematococcus pluvialis mutant induced with 15% CO2 and high light intensity were monitored with high spatial resolution in a non-destructive and label-free manner using single-cell Raman imaging. Astaxanthin intensity increased by 3.5 times within 12h under 15% CO2, and the accumulation rate was 5.8 times higher than that under air. Lipids intensity under 15% CO2 was 27% higher than that under air. The lipids initially concentrated in chloroplast under 15% CO2 due to an increase of directly photosynthetic fatty acid, which was different from the whole-cell dispersed lipids under air. Astaxanthin produced in chloroplast first accumulated around nucleus and then spread in cytoplasmic lipids under both air and 15% CO2. The calculation results of kinetic models for lipids and astaxanthin evolutions showed that accumulation rate of lipids was much higher than that of astaxanthin in cells.

Removing ethinylestradiol from wastewater by microalgae mutant Chlorella PY-ZU1 with CO2 fixation

Removal of endocrine-disrupting chemical ethinylestradiol (EE2) from wastewater by microalgal mutant Chlorella PY-ZU1 under 15% CO2 were investigated. Moreover, the effects of EE2 on microscopic structure and antioxidation ability of microalgal cells were determined. EE2 concentrations in range of 0.01-5u202fmgu202fL-1 stimulated microalgal growth. Increasing the original EE2 concentration from 0 to 5u202fmgu202fL-1 increased the cell fractal dimension from 1.38 to 1.59 and reduced the cell size from 5.18 to 3.41u202fμm. Meanwhile, superoxide dismutase and catalase activities, which represented cellular antioxidant capacity, first increased from 44.59 and 0.54u202fUu202fmL-1 to peak values of 65.57 and 1.49u202fUu202fmL-1, respectively, and then correspondingly decreased to 34.36 and 0.36u202fUu202fmL-1. Malondialdehyde content that indicated the cell oxidation damage degree first decreased from 2.57 to 2.03u202fnmolu202fmL-1, then increased to 2.59u202fnmolu202fmL-1. The highest EE2 removal efficiency of 94% by Chlorella PY-ZU1 was achieved at the original EE2 concentration of 5u202fmgu202fL-1.

Alternatively permutated conic baffles generate vortex flow field to improve microalgal productivity in a raceway pond

Alternatively permutated conic (APC) baffles were proposed to generate vertical and horizontal vortex flow to intensify mixing and mass transfer in a raceway pond. Both clockwise vortexes were generated before and after conic baffles in the main stream to increase perpendicular velocity by 40.3% and vorticity magnitude by 1.7 times on vertical cross section. Self-rotary flow around conic baffles and vortex flow among conic baffles were generated to increase perpendicular velocity by 80.4% and vorticity magnitude by 4.2 times on horizontal cross section. The bubble generation time and diameter decreased by 25.5% and 38.7%, respectively, while bubble residence time increased by 84.3%. The solution mixing time decreased by 48.1% and mass transfer coefficient increased by 34.0% with optimized relative spacing (ε) and height (ω) of conic baffles. The biomass productivity of Spirulina increased by 39.6% under pure CO2 with APC baffles in a raceway pond.

Serial lantern-shaped draft tube enhanced flashing light effect for improving CO 2 fixation with microalgae in a gas-lift circumflux column photobioreactor

A novel serial lantern-shaped draft tube (LDT) that generates vortices is proposed to increase radial velocity between dark and light regions for improving CO2 fixation with microalgae in a gas-lift circumflux column (GCC) photobioreactor. Clockwise vortices are generated in the downflow outerloop of the GCC photobioreactor with LDT. Radial velocity was improved from 1.50 to 4.35u202f×u202f10-2u202fm/s, thereby decreased liquid cycle period between dark and light regions by 1.9 times. Mixing time decreased by 21%, and mass transfer coefficient increased by 26% with LDT. Liquid radial velocity in the downflow outerloop and mass transfer coefficient in the GCC photobioreactor both first increased and then decreased when single-lantern height was increased. Peak CO2 fixation rate increased from 0.62 to 0.87u202fg/L/d, microalgal biomass yield increased by 50%. Removal efficiencies of pollutants (chemical oxygen demand, ammonium, tilmicosin, and ethinylestradiol) in wastewater were 62-90% with microalgae growth in GCC photobioreactor with LDT.

Improving microalgal growth by strengthening the flashing light effect simulated with computational fluid dynamics in a panel bioreactor with horizontal baffles

Biological CO2 elimination by photosynthetic microalgae is a sustainable way to mitigate CO2 from flue gas and other sources. Computational fluid dynamics was used to simulate algal cell movement with an enhanced flashing light effect in a novel panel bioreactor with horizontal baffles. Calculation results showed that the light/dark (L/D) cycle period decreased by 17.5% from 17.1 s to 14.1 s and that the horizontal fluid velocity increased by 95% while horizontal baffles were used under a 0.02 vvm air aeration rate and a microalgal concentration of 0.85 g L−1. The probability of the L/D cycle period within 5–10 s increased from 27.9% to 43.6%, indicating a 56% increase when horizontal baffles existed. It was proved by experiments that the mass-transfer coefficient increased by 31% and the mixing time decreased by 13% under a 0.06 vvm air aeration rate when horizontal baffles were used, and the algal biomass yield increased by ∼51% along with the decrease in the L/D cycle period when horizontal baffles were used.