Promotional effect of spherical alumina loading with manganese-based bimetallic oxides on nitric-oxide deep oxidation by ozone

Nitric oxide （NO） deep oxidation to dinitrogen pentoxide （N2O5） by ozone together with wet scrub-bing has become a promising technology for nitrogen-oxide （NOx） removal in industrial boilers. Catalysts were introduced to enhance the N2O5 formation rate with less ozone injection and leakage. A series of monometallic catalysts （manganese, cobalt, cerium, iron, copper, and chromium） as pre-pared by the sol-gel method were tested. The manganese oxides achieved an almost 80% conver-sion efficiency at an ozone （O3）/NO molar ratio of 2.0 in 0.12 s. The crystalline structure and porous parameters were determined. The thermodynamic reaction threshold of NO conversion to N2O5 is oxidation with an O3/NO molar ratio of 1.5. Spherical alumina was selected as the support to achieve the threshold, which was believed to improve the catalytic activity by increasing the surface area and the gas-solid contact time. Based on the manganese oxides, cerium, iron, chromium, cop-per, and cobalt were introduced as promoters. Cerium and iron improved the deep-oxidation effi-ciency compared with manganese/spherical alumina, with less than 50 mg/m3 of outlet NO ＋ nitro-gen oxide, and less than 25 mg/m3 of residual ozone at an O3/NO molar ratio of 1.5. The other three metal oxides inhibited catalytic activity. X-ray diffraction, nitrogen adsorption, hydrogen tempera-ture-programmed reduction, and X-ray photoelectron spectroscopy results indicate that the cata-lytic activity is affected by the synergistic action of NOx oxidation and ozone decomposition.

UV-Catalytic Treatment of Municipal Solid-Waste Landfill Leachate with Hydrogen Peroxide and Ozone Oxidation

The performance of UV/H_2O_2, UV/O_3, and UV/H_2O_2/O_3 oxidationsystems for the treatment of municipal solid-waste landfill leachatewas investigated. Main objective of the experiment was to removetotal organic carbon (TOC), non-biodegradable organic compounds(NBDOC) and color. In UV/H_2O_2 oxidation experiment, with theincrease of H_2O_2 dosage, removal efficiencies of TOC and coloralong with the ratio of biochemical oxygen demand (BOD) to chemicaloxygen demand (COD) of the effluent were increased and a betterperformance was obtained than the system H_2O_2 alone.

Degradation of Organic Pollutants by the Advanced Oxidation Processes

A kinetic model has been developed for the degradation of organic pollutants concerning with hydroperoxide ion as the initial step for generation of hydroxyl radical and its subsequent reaction mechanisms. Rate equations were derived for depletion of ozone and pollutants in the peroxone oxidation process using ozone and hydrogen peroxide as combined oxidants. Kinetic data obtained experimentally from the hydrogen peroxide-ozone reaction and peroxone oxidation of nitrobenzene were analyzed by using the proposed rate equations.

Efficiency and mechanism of degradation of alachlor in water by O_3/H_2O_2 catalyst system

Alachlor is used widely as a herbicide,but is an environmental endocrine disruptor. O 3/H 2O 2 system is used as catalyst to delve on the degradation efficiency of alachlor. The amount of the catalyst H 2O 2,the pH value of the soluble, the temperature and quality of water sample are changed to investigate the effect of these factors on the degradation of alachlor. The degradation of alachlor is qualitatively analyzed through their GS MS spectra and the possible mechanism of the degradation of alachlor is discussed as well.

Experimental study on zero excess sludge production process with ozonation unit in MBR process

In order to investigate the influence factors of zero excess activated sludge (EAS) process by ozonation, a 100 L membrane bioreactor coupled with a sludge ozonation unit (MBR-SO) was performed for 80 d without EAS wasting. Some mathematical models were developed to elucidate the relationship between process parameters and the operating effects. It is considered that the sludge lysing ratio (ξ), produced COD per unit mass lysed MLSS (η), observed sludge yield coefficient (Yobs) and intrinsic yield coefficient for COD produced by lysed sludge (Y2) significantly affect the flowrate to ozonation unit (q). When q is 0.0067 times of influent flowrate (Q) and ξ is about 0.72 for each batch ozonation, a relatively stable MLSS concentration of 8168 mg/L and zero Yobs are achieved in the MBR-SO system. The calculation of sludge disintegration number indicates that the high ξ can apparently decrease the sludge amount needed for ozonation. At the same ozone dose, the low input ozone concentration and high flowrate can enhance the sludge lysing effects and a low energy consumption of 0.041 Yuan/m3 wastewater is obtained.

A quantum chemistry study on reaction mechanisms of SO_2 with O_3 and H_2O_2

Reaction mechanisms of SO2 with O3 and H2O2 were investigated using quantum chemistry ab initio methods. Structures of all reactants, products, and transition states were optimized at the B3LYP/6-311G＋（3df,2p） level, and energy calculations were made at the G2M level. SO2 reactions with O3 and H2O2 occurred by O-abstraction and OH-abstraction by SO2, respectively, at length forming SO3＋O2 （3Eg） and H2SO4. For SO2＋O3 reactions the barrier height was predicted to be 9.68 kcal/mol with a rate constant of 3.61 × 10^-23 cm^3/（molecule.s） at 300 K, which is below the experimental upper limit. The rate constant predicted for this reaction accords well with the one provided by National Institute for Standards and Technology （NIST） in 250-500 K. For SO2＋H2O2 reactions the barrier height was predicted to be 62.39 kcal/mol with a rate constant of 2.48× 10^-61 cm^3/（molecule.s） at 300 K.