ABSTRACT
To reveal the nature of CO2 reduction to formate with high efficiency by in situ hydrogen produced from hydrothermal reactions with iron, DFT calculations were used. A reaction pathway was proposed in which the formate was produced through the key intermediate species, namely iron hydride, produced in situ in the process of hydrogen gas production. In the in situ hydrogenation of CO2, the charge of H in the iron hydride was -0.135, and the Fe-H bond distance was approximately 1.537 Å. A C-H bond was formed as a transition state during the attack of Hδ- on Cδ+. Finally, a HCOO species was formed. The distance of the C-H bond was 1.107 Å. The calculated free energy barrier was 16.43 kcal/mol. This study may provide new insight into CO2 reduction to formate in hydrothermal reactions with metal.
Subject(s)
Hydrogen , Iron , Hydrogen/chemistry , Iron/chemistry , Carbon Dioxide/chemistry , Formates/chemistryABSTRACT
Al2 (SO4), FeCl3, PAC and PAFC were used to coagulate the effluent of MSW incineration leachate after biochemical treatment, and mathematical models for COD removal were set up as well. The results show that COD removal rates are 20%, 17%, 30% and 40% respectively with addition of 500 mg x L(-1) Al2 (SO4)3, FeCl3, PAC and PAFC alone at pH 6. The < 2 000 fraction contains mainly dissolved organics from the leachate after biochemical treatment. Moreover, according to the analysis of Zeta potential and transmission electron microscope (TEM), the main mechanisms of the leachate coagulation can be explained as electrical neutralization, netting and bridging. As a matter of fact, compared to inorganic coagulants, the poly coagulants show higher capacity on these three functions.
Subject(s)
Carbon/chemistry , Refuse Disposal , Waste Disposal, Fluid/methods , Water Pollutants, Chemical/chemistry , Flocculation , Incineration , Models, Theoretical , Organic Chemicals/chemistryABSTRACT
SPR electrode was used in Electrio-Fenton treatment on the effluent from biological and coagulative treatments of solid waste incinerator leachate, at the same time, the kinetics model for the COD effluent concentration were set up. The result indicated that the disposal curve of COD confirm to the pseudo third order kinetics, and the formula is c(t) = (2kt + c(0)(-2))(-0.5), in which the c(t) is the COD concentration of treatment effluent. With the statistical analysis to the disposal curve of COD from Electro-Fenton treatment in different conditions, the experience mathematics model of k value was set up, in which the current density, pH value and COD concentration of influent are effective factors. Moreover, with the comparison between the simulative COD of effluent and the experimental results, it was showed that this kinetic model could be used to investigate the COD disposal efficiency of Electro-Fenton treatment on the effluent from biological and coagulative treatments of solid waste incinerator leachate preferably.
Subject(s)
Incineration , Refuse Disposal/methods , Waste Disposal, Fluid/methods , Water Pollutants, Chemical/isolation & purification , Catalysis , Chlorides , Electrochemistry , Ferric Compounds/chemistry , Hydrogen Peroxide/chemistry , Iron/chemistry , Kinetics , Models, Theoretical , Organic Chemicals/chemistry , Water Pollutants, Chemical/chemistryABSTRACT
By using a trickle bed reactor which was designed by the authors, the catalytic wet air oxidation reaction of phenol on CuO/gamma-Al2O3 catalyst was studied. The results showed that in mild operation conditions (at temperature of 180 degrees C, pressure of 3 MPa, liquid feed rate of 1.668 L x h(-1) and oxygen feed rate of 160 L x h(-1)), the removal of phenol can be over 90%. The curve of phenol conversion is similar to "S" like autocatalytic reaction, and is accordance with chain reaction of free radical. The kinetic model of pseudo homogenous reactor fits the catalytic wet air oxidation reaction of phenol. The effects of initial concentration of phenol, liquid feed rate and temperature for reaction also were investigated.
