Xiang-li Long

Adsorption of EDTA on activated carbon from aqueous solutions.

In this study, the adsorption of EDTA on activated carbon from aqueous solutions has been investigated in a batch stirred cell. Experiments have been carried out to investigate the effects of temperature, EDTA concentration, pH, activated carbon mass and particle size on EDTA adsorption. The experimental results manifest that the EDTA adsorption rate increases with its concentration in the aqueous solutions. EDTA adsorption also increases with temperature. The EDTA removal from the solution increases as activated carbon mass increases. The Langmuir and Freundlich equilibrium isotherm models are found to provide a good fitting of the adsorption data, with R(2) = 0.9920 and 0.9982, respectively. The kinetic study shows that EDTA adsorption on the activated carbon is in good compliance with the pseudo-second-order kinetic model. The thermodynamic parameters (E(a), ΔG(0), ΔH(0), ΔS(0)) obtained indicate the endothermic nature of EDTA adsorption on activated carbon.

Regeneration of hexamminecobalt(II) catalyzed by activated carbon treated with KOH solutions

The combined elimination of NO and SO(2) can be realized by hexamminecobalt(II) solution which is formed by adding soluble cobalt(II) salt into the aqueous ammonia solution. Activated carbon is used as a catalyst to regenerate hexamminecobalt(II), Co(NH(3))(6)(2+), so that NO removal efficiency can be maintained at a high level for a long time. In this study, KOH solution has been explored to modify coconut activated carbon to meliorate its catalytic performance in the reduction of hexamminecobalt(III), Co(NH(3))(6)(3+). The experiments have been performed in a batch stirred cell to investigate the effects of KOH concentration, impregnation duration, activation temperature and activation duration on the performance of activated carbon. The results show that the best KOH concentration for the improvement of activated carbon is 0.5 mol l(-1). The optimal impregnation duration is 9h. High temperature is favorable to ameliorating the catalytic performance of activated carbon. The optimum activation duration is 4h.

Experimental determination of equilibrium constant for the complexing reaction of nitric oxide with hexamminecobalt(II) in aqueous solution.

Ammonia solution can be used to scrub NO from the flue gases by adding soluble cobalt(II) salts into the aqueous ammonia solutions. The hexamminecobalt(II), Co(NH3)6(2+), formed by ammonia binding with Co2+ is the active constituent of eliminating NO from the flue gas streams. The hexamminecobalt(II) can combine with NO to form a complex. For the development of this process, the data of the equilibrium constants for the coordination between NO and Co(NH3)6(2+)over a range of temperature is very important. Therefore, a series of experiments were performed in a bubble column to investigate the chemical equilibrium. The equilibrium constant was determined in the temperature range of 30.0-80.0 degrees C under atmospheric pressure at pH 9.14. All experimental data fit the following equation well: [see text] where the enthalpy and entropy are DeltaH degrees = - (44.559 +/- 2.329)kJ mol(-1) and DeltaS degrees = - (109.50 +/- 7.126) J K(-1)mol(-1), respectively.

Removal of nitric oxide and sulfur dioxide from flue gases using a Fe II -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 FeIII-EDTA to FeII-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 FeII-EDTA solution coupled with the FeII-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.

Oxidative Catalytic Absorption of NO in Aqueous Ammonia Solution with Hexamminecobalt Complex

ABSTRACT The hexamine cobalt (II) complex is used as a coordinative catalyst, which can coordinate NO to form a nitrosyl ammine cobalt complex, and O 2 to form a μ -peroxo binuclear bridge complex with an oxidability equal to hydrogen peroxide, thus catalyze oxidation of NO by O 2 in ammoniac aqueous solution. Experimental results under typical coal combusted flue gas treatment conditions on a laboratory packed absorber- regenerator setup show a NO removal of more than 85% can be maitained constant.

A Study on the Production of Isophthalic Acid from M-xylene under the Catalysis of Cobalt and H3PW12O40/Carbon Modified by HNO3 Solution

Abstract The oxidation of m-xylene(MX) to isophthalic acid(IPA) catalyzed by phosphotungstic acid(HPW) supported on modified activated carbon was investigated. The activated carbon loading with HPW is modified by HNO3 solution to ameliorate its catalytic capability in the oxidation of MX to IPA. Experiments have been carried out to study the effects of modification conditions, such as HNO3 concentration, impregnation time, impregnation temperature, activation temperature and activation time, on the catalytic performance of activated carbon. The experimental results demonstrate that the carbon sample impregnated in 10%(vol) HNO3 solution at 45°C for 8 h followed by calcined at 700°C for 4 h has the best catalytic capability. The characterization results imply that the specific surface area and micropores of the carbon samples decrease after being treated with HNO3 solution. But the acidic functional groups on the activated carbon surface increase, which play a vital role in improving the catalytic ability of the HPW/C catalyst in the oxidization of m-xylene to IPA.

Effect of H2O2 modification of H3PW12O40@carbon for m-xylene oxidation to isophthalic acid

The production of isophthalic acid (IPA) from the oxidation of m-xylene (MX) by air is catalyzed by H3PW12O40 (HPW) loaded on carbon and cobalt. We used H2O2 solution to oxidize the carbon to improve the catalytic activity of HPW@C catalyst. Experiments reveal that the best carbon sample is obtained by calcining the carbon at 700 °C for 4 h after being impregnated in the 3.75% H2O2 solution at 40 °C for 7 h. The surface characterization displays that the H2O2 modification leads to an increase in the acidic groups and a reduction in the basic groups on the carbon surface. The catalytic capability of the HPW@C catalyst depends on its surface chemical characteristics and physical property. The acidic groups play a more important part than the physical property. The MX conversion after 180 min reaction acquired by the HPW@C catalysts prepared from the activated carbon modified in the best condition is 3.81% over that obtained by the HPW@C catalysts prepared from the original carbon. The IPA produced by the former is 46.2% over that produced by the latter.

Production of NMSBA from NMST Catalyzed by Co/Mn/Br and HPW@C Modified with ZnCl2 Solution

Abstract 2-nitro-4-methylsulfonylbenzoic acid (NMSBA) can be produced by oxidizing 2-nitro-4-methylsulfonyltoluene (NMST) with air catalyzed by Co/Mn/Br and phosphotungstic acid(HPW) loaded on activated carbon. This paper reports that the catalytic ability of the HPW@C catalyst in the oxidation of NMST to NMSBA can be improved by treating the activated carbon with ZnCl2 solution. The best modification condition with ZnCl2 solution is impregnating the carbon sample in 0.1 mol/L solution for 6 h followed by calcination at 600 °C for 4 h. The increase of the surface area and the acidic groups on the carbon surface enhances the catalytic ability of the HPW@C catalyst. The mesopores play an important role in the catalytic oxidation of NMST to NMSBA.