A jacketed stirred-cell reactor, operated semi-continuously, was used to assess the kinetics of fast ozonation reactions by reactive absorption. The method was applied to the direct ozone reaction with resorcinol. A high resorcinol concentration was used to reach a steady state and to neglect the byproducts accumulation. Thus, the mass-transfer rate, and consecutively the reaction rate, were deduced from the ozone mass balance in the gas phase. The gas-phase and liquid-phase mass-transfer coefficients were previously measured directly through the ozone absorption in appropriated conditions. The results emphasized the high sensitivity of the reaction rate constant to the ozone physicochemical properties, especially its solubility, which is controversial in the literature. Therefore, several correlations used to calculate the ozone solubility in water were considered to calculate the second-order reaction rate constant, which varied from 3.57-4.68 10 5 L mol -1 s -1 at 20°C to 9.50-12.2 10 5 L mol -1 s -1 at 35°C. The activation energy was in the range 35-59 kJ mol -1 depending on the considered ozone solubility correlation. A sensitivity analysis is provided to assess the influence of the experimental conditions and ozone physicochemical properties on the model. Finally, the applicability of this method is thoroughly discussed.2

An innovative implementation of the O 3 /H 2 O 2 advanced oxidation process was proposed to intensify the hydroxyl radical generation. Natural or drinking waters, containing atrazine as a probe compound, were spiked with H 2 O 2 and further continuously mixed to a pre-ozonated solution in a homogeneous tubular reactor filled with static mixers. Hydraulic residence times in the range 10 s-140 s were set at different sampling ports. The experimental results confirmed a very high ozone decomposition rate, concomitant with a high hydroxyl radical exposure (R ct in the range from 10-7 to 10-6), especially during the initial ozone decomposition phase (between 10 and 20 s). Equimolar initial concentrations of hydrogen peroxide and ozone were optimal to maximize the hydroxyl radical generation and to minimize their relative consumptions. The influence of the water matrix on the ozone decomposition and the hydroxyl radical generation was limited. This study is a proof of concept that using a homogeneous tubular reactor would be more effective than a gas-liquid reactor to apply the peroxone process.

No abstract

International audienceThe reaction rate constant between the hydroperoxide anion (HO2−) and molecular ozone was evaluated from the reactive absorption method in the range of temperature from 20 to 35 °C. This reaction is crucial in the initiation step of the ozone decomposition, especially using the peroxone process which combines ozone and hydrogen peroxide in solution. A stirred-cell operated semi-continuously was used for this purpose. A high initial concentration of tert-butanol (0.05 mol L−1) was applied to efficiently scavenge all radicals and to avoid any parasite reaction. Based on the dissolved H2O2 concentration decreasing and the outlet ozone concentration time-course, the stoichiometry of the initiation reaction was determined, with one mol of H2O2 consumed per mol of ozone transferred. The chemical conditions were thoroughly selected to reach a fast pseudo-first order absorption regime. The reaction rate constant increased from 1.91 × 106–2.40 × 106 L mol−1 s−1 at 20 °C to 5.68 × 106–7.31 × 106 L mol−1 s−1 at 35 °C

In order to evaluate the effect of seaweeds in bio-filtration for removing nitrogen from marine aquaculture and in bioenergy production, Ulva sp. was used in this study. Experiments were triplicated and run in 3-day incubation at salinities with 30 psu, 10 psu and 5 psu in different initial ammonium nitrogen concentrations from 100 µM to 10,000 µM, equivalently to marine aquaculture conditions. The highest concentrations of ammonium removed were about 690 µmol (12.42 mg) NH4+ at 30 psu, 410 µmol (7.38 mg) NH4+ at 10 psu and 350 µmol NH4+(6.3 mg NH4+) at 5 psu in three days of incubation, while highest growth rates of Ulva sp. were 49% and 150% per day at 500 µM of initial ammonium concentration, similarly to the growth rate reported in microalgae. Moreover, after  these experiments, biomass of Ulva sp. has been tested for bioenergy producing goals, because the carbohydrate concentration of this alga was very high, reaching 60-70% of DW. Thus, Ulva sp. can be cultured to remove nitrogen concentration in eutrophication conditions at aquaculture systems in combination with the purpose of bioenergy production after harvesting. Để đánh giá hiệu quả của tảo biển trong việc lọc sinh học loại bỏ hợp chất ni tơ từ việc nuôi trồng thủy sản và trong việc sản xuất năng lượng sinh học, Ulva sp. đã được sử dụng trong nghiên cứu này. Các thí nghiệm được lặp lại 3 lần và chạy trong 3 ngày trong tủ ổn nhiệt tại các điều kiện độ mặn 30psu, 10psu, 5psuở các nồng độ NH4+-N từ 100μM đến 10.000μM, tương đương với điều kiện nuôi trồng thủy sản nước mặn. Nồng độ cao nhất của NH4+-N được loại bỏ khoảng 690 μmol NH4+ (12,42mg NH4+) tại 30psu, 410μmol NH4+ (7,38mg NH4+) tại 10psu và 350 μmol NH4+ (6.3mg NH4+) tại 5psu, trong đó tỉ lệ sinh trưởng của Ulva sp. là rất cao, sinh trưởng từ 49 đến 150% mỗi ngày tại nồng độ ammonium ban đầu 500 μM tương đương với sinh trưởng của vi tảo. Hơn nữa, sau các thí nghiệm trên, sinh khối của Ulva sp. được thử nghiệm sản xuất năng lượng sinh học vì hàm lượng carbohydrate trong tảo rất cao, chiếm khoảng 60-70% trọng lượng khô của tảo. Như vậy, Ulva sp. có thể đượcnuôi trồng để loại bỏ hợp chất ni tơ trong điều kiện phú dưỡng của các hệ thống nuôi trồng thủy sản, kết hợp với mục tiêusản xuất năng lượng sinh học sau thu hoạch.

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