Absorption of NO from simulated flue gas by using NaClO2/(NH4)2CO3 solutions in a stirred tank reactor

Experiments were performed in a stirred tank reactor to study the absorption kinetics of NO into aqueous solutions of NaClO₂/(NH₄)₂CO₃ solutions. The absorption process is a fast pseudo-reaction, and the reaction was found to be second-order with respect to NO and first-order with respect to NaClO₂, respectively. The frequency factor and the average activation energy of this reaction were 4.56×10¹¹ m⁶/(mol² s) and 33.01 kJ/mol respectively. The absorption rate of NO increased with increasing reaction temperature, but decreased with increasing (NH₄)₂CO₃ solution.     

Performance characteristics of NO removal by cobalt diethylenetriamine solution

The cobalt(II) diethylenetriamine ([Co(dien)₂]²⁺) complex is a newly developed metal thiochelate for the removal of NO from flue gas. The performance characteristics of NO absorption into [Co(dien)₂]²⁺ solution were studied in a stirred reactor. The experimental results showed that this absorption could be regarded as fast pseudo-mth-order reaction and the reaction rate could be expressed as second-order with respect to NO concentration and first-order with respect to [Co(dien)₂]²⁺ concentration. The enhancement factor was 1609.1 at the [Co(dien)₂]²⁺ concentration of 0.01 mol/L. Its optimal absorption conditions were temperature 50 °C, NO concentration 540 ppm, [Co(dien)₂]²⁺ concentration 0.02 mol/L and O₂ concentration 6%, which were determined by orthogonal experiment.     

Absorption of NO into NaClO3/NaOH solutions in a stirred tank reactor

The absorption kinetics of NO into aqueous solutions of NaClO₃/NaOH was investigated under different experimental conditions in a stirred tank reactor. It is proven that the absorption process is a fast pseudo-mth reaction. The reaction was found to be second-order with respect to NO and first-order with respect to NaClO₃. The frequency factor and average activation energy of this reaction were 2.696 × 10⁶ m³/(mol s) and 13.88 kJ/mol, respectively. The addition of NaOH to solutions of NaClO₃ decreased the absorption rate of NO. And the absorption rate of NO increased with increasing reaction temperature. In this study, the flue gas flow rate almost had little effect on the absorption of NO.     

Absorption of Carbon Dioxide into Aqueous Solution of Sodium Glycinate

Abstract

Carbon dioxide was absorbed into aqueous solution of sodium glycinate (SG) at different SG concentrations, CO₂ partial pressures, and temperatures in the range of 0.5–3.0 kmol/m³, 25–101.3 kPa, and 298–318 K, respectively, using a stirred semi-batch vessel with a planar gas-liquid interface. Both the reaction order and rate constant are determined from gas absorption rates under the fast reaction regime. The reaction was found to be first order with respect to both CO₂ and SG. The activation energy for the CO₂-SG reaction has been found to be 59.8 kJ/mol. The second-order reaction rate constants were used to obtain the theoretical values of absorption rate based on the film theory.     

A RIGOROUS MODEL FOR ABSORPTION OF CARBON DIOXIDE INTO AQUEOUS N-METHYLDIETHANOLAMINE SOLUTION

A rigorous model for absorption of carbon dioxide into aqueous N-methyldiethanolamine (MDEA) based on the assumption of reversible reactions and the simplified model with a pseudo-first order irreversible reaction hypothesis were employed to compare with experimental data. The experimental absorption rates were obtained from a characterized double stirred-cell absorber with a planar gas-liquid interface. It was demonstrated that the numerical solution of the rigorous model provides a better prediction for the absorption rate of carbon dioxide into aqueous MDEA solution than that of the simplified model. Only in the case of absorption experiments carried out at a low carbon dioxide partial pressure (p < 20 kpa) and low amine concentration (MDEA_total < 1000 mol/m³), the assumption of pseudo-first order irreversible reaction is reasonable.     

Absorption of NO in Aqueous NaClO2/Na2CO3 Solutions

The absorption rates of NO into aqueous solutions of NaClO₂ blended with Na₂CO₃ were investigated in a stirred reactor. The experimental results showed that the reaction rate could be expressed as . An equation for a second‐order reaction rate constant between NO and NaClO₂, k_mn = 5.79 · 10¹⁵ exp(–5557.26/T), was obtained. The addition of Na₂CO₃ into the solution of NaClO₂ decreased the reaction rate constant. The optimal absorption conditions involved a NO concentration of 540 ppm, NaClO₂ concentration of 50 mol m^–3, Na₂CO₃ concentration of 10 mol m^–3, temperature of 333 K and O₂ concentration of 4 %, which were determined by an orthogonal experiment. Under these optimal conditions, it was possible for the absorption rate to reach up to 1.9271 · 10^–5 mol/(s m²).     

Chemical Absorption of Carbon Dioxide into Aqueous Solution of Potassium Threonate

Carbon dioxide was absorbed into aqueous solution of potassium threonate (PT) at different concentrations of PT and CO₂, and temperatures in the range of 0.1–1.0 kmol/m³, 10.1–101.3 kPa, and 293-313 K, respectively, using a stirred semi-batch vessel with a planar gas-liquid interface. Both the reaction order and rate constant were determined from gas absorption rates under the fast pseudo-first-reaction regime. The reaction was found to be first order with respect to both CO₂ and PT, and its activation energy has been found to be 40.6 kJ/mol. From a comparison of the reaction kinetics by the overall reaction scheme with those by the elementary reaction scheme based on the zwitterions mechanism, the overall reaction between CO₂ and PT has been found to be equivalent to the formation of zwitterions.     

Removal of nitric oxide and sulfur dioxide from flue gases using a FeII-ethylenediamineteraacetate solution

The combined absorption of NO and SO₂ into the Fe(II)-ethylenediamineteraacetate(EDTA) solution has been realized. Activated carbon is used to catalyze the reduction of Fe^III-EDTA to Fe^II-EDTA to maintain the ability to remove NO with the Fe-EDTA solution. The reductant is the sulfite/bisulfite ions produced by SO₂ dissolved into the aqueous solution. Experiments have been performed to determine the effects of activated carbon of coconut shell, pH value, temperature of absorption and regeneration, O₂ partial pressure, sulfite/bisulfite and chloride concentration on the combined elimination of NO and SO₂ with Fe^II-EDTA solution coupled with the Fe^II-EDTA regeneration catalyzed by activated carbon. The experimental results indicate that NO removal efficiency increases with activated carbon mass. There is an optimum pH of 7.5 for this process. The NO removal efficiency increases with the liquid flow rate but it is not necessary to increase the liquid flow rate beyond 25 ml min^?1. The NO removal efficiency decreases with the absorption temperature as the temperature is over 35 °C. The Fe²⁺ regeneration rate may be speeded up with temperature. The NO removal efficiency decreases with O₂ partial pressure in the gas streams. The NO removal efficiency is enhanced with the sulfite/bisulfite concentration. Chloride does not affect the NO removal. Ca(OH)₂ and MgO slurries have little influence on NO removal. High NO and SO₂ removal efficiencies can be maintained at a high level for a long period of time with this heterogeneous catalytic process.     

EXPERIMENTAL STUDIES AND PARAMETER OPTIMIZATION OF SEPARATION OF COPPER USING HOLLOW FIBER–SUPPORTED LIQUID MEMBRANE

The separation of copper from a leach liquor bearing 204.59 mol/m³ Cu, 40.83 mol/m³ Zn, 33.94 mol/m³ Co, 255.58 mol/m³ Ni, and 75.72 mol/m³ (NH₄)₂SO₄ has been carried out with a hollow fiber membrane using LIX 84-I as the mobile carrier. Central composite inscribed (CCI) design was used to design the experiments. The factors considered for the CCI design were pH, LIX 84-I concentration in the membrane phase, flow rate, and acid concentration in the strip solution. A reduced quadratic model was found to fit the experimental data. Detailed analysis of the effect of different factors as well as their interaction on the extraction of copper has been done. The optimized condition for maximum copper flux was found to be pH 4.5, 39.88% LIX 84-I, 360 mL/min flow rate, and 7% H₂SO₄ in strip solution. The highest copper flux of 7.46 × 10^?5 mol/m² · s was obtained experimentally at the above conditions, which is in good agreement with the predicted value of 7.57 × 10^?5 mol/m² · s.     

Tailings Management and Leaching Kinetics in Iron Removal from Kaolin Washing Plants Tailings

A study has been made of the leaching process to remove iron oxides from quartz presented in kaolin washing plant tailings. The tailings mineralogical constituents were quartz, clay minerals, hematite, and calcite. The leaching rate of Fe₂O₃ increased with increasing acid concentration, temperature, reaction time, and decreasing pulp solid percent. Shrinking core first-order kinetics model was presented to analyse the data. The activation energy was 23.51 kJ/mol and process was reaction-controlled process (1?(1 ? α)^1/3 = 46.52e^?23.51/RTt). Using this method, the Fe₂O₃ amount decreased to 0.03% with a recovery of 89.06%. The results showed that the leaching approach was the best method for the management of these tailings.     

TEMPORAL POST-DISCHARGE REACTIONS IN PLASMA-CHEMICAL DEGRADATION OF SLAUGHTERHOUSE EFFLUENTS

The plasma-chemical degradation of bovine blood effluents provided by a slaughterhouse plant is achieved by exposing the dilute blood target to a gliding discharge in humid air. The several steps of the degradation were ascribed to the oxidizing and acidifying properties of the parent species formed in the discharge (e.g., mainly °OH and °NO and their derivatives). The oxidation reactions go on after the discharge is switched off and evidence Temporal Post-Discharge Reactions (TPDR). This demonstrates that less reactive moieties than °OH and °NO – tentatively H₂O₂ and ONO₂H – are concerned in TPDR and probably also involved in the main degradation process performed under plasma conditions. Industrial effluents involve large quantities of sodium citrate additive (10^?2 mol L^?1), which is first degraded according to zero order kinetics, folllowed by a 1st order kinetic step (k₁ = 0.2 min^?1) ascribed to the diffusion controlled degradation of hemoglobin (Hb).     

Cobalt-exchanged mordenites: preparation,characterization and catalytic activity for the abatement of NO with CH<Subscript>4</Subscript> in the presence of excess O<Subscript>2</Subscript>

The abatement of NO with methane in the presence of oxygen was studied on various commercial MOR in the Na-form (Na-MOR) and H-form (H-MOR), or exchanged to various extents with cobalt (Co-MOR). The sodium and cobalt contents were determined by atomic absorption. Samples were characterized by FTIR and volumetric measurements of CO adsorption. Chemical analysis indicated that one cobalt species replaced two Brønsted acid sites in H-MOR and two Na⁺ ions in Na-MOR. The IR analysis of the OH stretching region, evidencing an unexpected presence of Brønsted acid sites (band at 3610 cm^?1) in Co-MOR, indicated that the exchange process had a more complex stoichiometry. The adsorption of CO at RT on Co-MOR, in addition to the bands of the corresponding H-MOR and Na-MOR matrices, yielded two types of Co^II-carbonyls, the first type occupied the?mordenite main channels, and the second one the mordenite smaller channels. Brønsted acid sites in mordenites were active for the selective catalytic reduction of NO with CH₄. Co-MOR samples were far more active than Na-MOR and H-MOR samples, showing that acid protons play a negligible role when Co is present. Co-MOR catalysts showing the highest activity had the largest amount of Co^II-carbonyls in the main channels. This result strongly suggests that Co^II in the main channels of MOR are the active sites for the CH₄ + NO + O₂ reaction.     

PERFORMANCE CHARACTERISTICS OF NOx REMOVAL BY AQUEOUS EMULSIONS OF YELLOW PHOSPHORUS

The absorption oflean NO_x (200?1000 ppm) gases in aqueous /% emulsions was investigated in a mechanically stirred vessel. The chemical reaction rate between NO, and P₄ in an alkaline solution was shown zero order with respect to NO_x concentration and three-seconds order to P₄ concentration. In the presence of S0_x=2, the chemical reaction rate between NO_x, and P₄ in alkaline solution was again zero order with respect to NO_x concentration, but changed to second order to P₄ concentration.

In addition, a robust design method was also used to evaluate the relative importance of various processing variables on the performance of this deNO_x process by P₄$ solution. S/N analysis of the results indicated that the P₄ concentration, liquor temperature and NO_x, concentration were the major factors in affecting NO_x absorption efficiencies.     

Absorption of lean NO in aqueous slurries of Ca(OH)2 with NaClO2 or Mg(OH)2 with NaClO2

The absorption of lean NO in an aqueous slurry of Ca(OH)₂ or Mg(OH)₂ with NaClO₂ was carried out using a stirred tank absorber with a plane gas-liquid interface at 25°C and 1 atm. The rates of absorption of NO and the accompanying desorption of NO₂ for the Ca(OH)₂ slurry were in close agreement with those for the aqueous mixed solution of NaClO₂ and NAOH with higher OH^? concentration, whereas for the Mg(OH)₂ slurry, the absorption rate of NO noticeably exceeded that for the former systems. Furthermore, the ratio of the NO₂ desorption rate to the NO absorption rate considerably exceeded the theoretical prediction for gas absorption with the consecutive reaction (maximum deviation attained 117%). Also, chlorine dioxide was detected in the gas phase. It was deduced from this experimental evidence that there occurs both desorption of the decomposition product ClO ₂ and gas-phase oxidation of No with ClO₂ to produce NO₂.     

CO2 absorption into a phase change absorbent: Water-lean potassium prolinate/ethanol solution

Phase change solvents are attractive energy-efficient absorbents for carbon dioxide (CO₂) capture due to CO₂-rich phase formation. Potassium prolinate + water + ethanol (ProK/W/Eth) solution has shown good capture characteristics as a promising one in our previous work. In this work, absorption rate of CO₂, solubility of N₂O, and heat of absorption for ProK/W/Eth solution were investigated using a stirred cell reactor and a CPA201 reaction calorimeter and these results were also compared with the aqueous ProK and 30 mass% MEA solutions. Using ethanol as a solvent can substantially increase the CO₂ physical solubility and the absorption rate of CO₂ in ProK/W/Eth solutions is far higher than that in aqueous 30 mass% MEA solutions especially at a low CO₂ loading range. Solid precipitation, obtained from the liquid-to-solid phase change absorption, was analyzed by ¹³C NMR and DSC-TGA. The enthalpy change for ProK/W/Eth solutions at various CO₂ loading was also discussed.     

Microwave-assisted green synthesis of hybrid nanocomposite: removal of Malachite green from waste water

Gum xanthan/psyllium-based nanocomposite was prepared by microwave-assisted synthetic method for the removal of toxic Malachite green (MG) dye from aqueous solutions. The nanocomposite was prepared by in situ incorporation of the K₂Zn₃[Fe(CN)₆]·9H₂O nanoparticles into the semi-IPN matrix in the presence of ammonium persulphate and glutaraldehyde as initiator-crosslinker system. Liquid uptake efficacy of the hybrid superabsorbent was enhanced through the optimization of different reaction conditions, including APS = 0.027 mol L^?1; glutaraldehyde = 0.053 × 10^?3 mol L^?1; solvent = 8.0 mL; acrylic acid = 10.928 mol L^?1; pH 7.0; reaction time = 60 s and microwave power = 100 % and its thermal behavior was evaluated using TGA-DTG-DTA technique. Candidate nanocomposite was characterized by FTIR, SEM, XRD and UV–visible spectroscopic methods. Various optimized parameters for the efficient removal (83 %) of the Malachite green were adsorbent dose of 800 mg, 14 mg L^?1 initial dye concentration and contact time of 28 h. Further, Langmuir and Freundlich adsorption isotherms showed good applicability in adsorption process of MG onto the nanocomposite with maximum adsorption efficiency of 3.21 mg g^?1. However, for Freundlich isotherm, R ² was around 0.9947 and value of 1/n was less than 1 for the synthesized nanocomposite which indicated that the Freundlich isotherm was more favorable than Langmuir isotherm model along with its usability for wide range of dye concentrations. The nanocomposite was found to be a potential product for dye removal from waste water and could prove to be a boon for textile sector.     

1-氨丙基-3-甲基咪唑溴功能型离子液体对CO2的吸收性能

1-氨丙基-3-甲基咪唑溴盐([APMIm])对CO₂等酸性气体具有较强的选择性吸收性能,在能源及环保领域有较好应用前景。运用等容饱和吸收法在高压不锈钢反应釜中测得CO₂在3种不同含水量的1-氨丙基-3-甲基咪唑溴盐水溶液中的溶解度数据,实验的温度范围为278.15~348.15 K,实验压力由低于大气压到最高6.5 MPa。实验结果表明,当水的质量分数达到60.84%以上,离子液体水溶液吸收CO₂的能力和速率才会得到显著提升。尤其值得注意的是,在278.15 K、120 kPa达到吸收平衡时,CO₂在含水质量分数为60.84%的1-氨丙基-3-甲基咪唑溴盐水溶液中的溶解度达到0.459 mol CO₂ ·(mol IL)^-1,接近理论最大吸收值0.5 mol CO₂·(mol IL)^-1。在较高压力下(3.9 MPa)最大CO₂吸收量为1.894 mol CO₂·(mol IL)^-1。     

Effect of gas-liquid phase compositions on NO2 and NO absorption into ammonium-sulfite and bisulfite solutions

The effect of gas-liquid phase compositions on NO and NO₂ absorption into ammonium-sulfite and bisulfite solutions is investigated. Preliminary experiment results indicate that the concentrations of (NH₄)₂SO₃ or NH₄HSO₃ solution and the molar ratio for HSO₃⁻ to the total solution concentrations all have significant impact on NO₂ and NO absorption rates. While the solution concentration is constant, the absorption of NO_x mixture is strongly related to the ratio NO₂/NO_x. The absorption rate of NO is primarily affected by NO₂ inlet concentration, and the NO absorption rate reaches the maximum value in (NH₄)₂SO₃ solution with the increase of NO₂ inlet concentration, which is determined by the reaction of NO and NO₂ with SO₃²⁻ as well as NO formation. Moreover, when the solution is NH₄HSO₃ the best ratio of NO₂/NO for the maximum value of the NO absorption rate becomes less or smaller. Meanwhile, the presence of NO in the gas phase is also favorable to the absorption rate of NO₂ in ammonium-sulfite or bisulfite solutions. The total results suggest that the coexistence of NO and NO₂ in the flue gas could enhance the absorption of each other to some extent.     

Reactive extraction of succinic acid using supercritical carbon dioxide

Reactive extraction using supercritical carbon dioxide (scCO₂) and tri-n-octylamine (TOA) was evaluated as a separation method of succinic acid from an aqueous solution. The reactive extraction of succinic acid was performed at varying initial acid concentrations in aqueous solution (0.07–0.45 mol?dm^?3), temperature (35–65°C) and pressure (8–16 MPa). The succinic acid separation was conducted in both batch mode and semi-continuous mode. The highest reactive extraction efficiency of approx. 62% was obtained for the process conducted in semi-continuous mode at 35°C and 16 MPa for the initial acid concentrations in aqueous phase of 0.39 mol?dm^?3.