Hydrazine degradation by ultrasonic irradiation.

The influence of pH on the degradation of hydrazine with a concentration of 0.1mmol/L was investigated under the stirring (300rpm) and ultrasonic irradiation conditions (200kHz, 200W) in the pH range of 1-9. It was found that the hydrazine degradation depended greatly upon pH under the ultrasonic irradiation condition, while it did not take place over the whole pH range under the stirring condition. Although it has been known that OH radicals and hydrogen peroxide are sonochemically formed from water, it was considered that the OH radicals played an important role of the hydrazine degradation, but not hydrogen peroxide. The pH dependence of the hydrazine degradation was discussed in terms of the relationship between the chemical structure and the basic dissociation constants of hydrazine.

Online measurements of low-volatile organic chlorine for dioxin monitoring at municipal waste incinerators.

In this study, an automatic sampling device and an analysis device have been developed for the measurement of low-volatile organic chlorine (LVOCl) in flue gas. The concentrations of dioxins (polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and dioxin-like polychlorinated biphenyls) have been estimated by online measurements of LVOCl at a municipal solid waste incinerator (MSWI) using these devices. The LVOCl concentration at the outlet of the selective catalyst reactor (SCR) of the MSWI increased momentarily up to 95 µg Cl m(-3) during the startup period of the MSWI; subsequently, it gradually decreased to less than 1.0 µg Cl m(-3) after 50h from the start of waste feeding. The concentration of toxic equivalent quantity (TEQ)-Dioxins at the SCR outlet had a linear positive relationship with the LVOCl concentrations. Moreover, the level of TEQ-Dioxins concentration can be estimated by using this relationship with LVOCl. From our results, since the LVOCl concentrations in a flue gas can thus be automatically analyzed every hour by online measurements, the operators of an MSWI would be able to monitor approximate TEQ-Dioxin emissions on a daily basis.

Sonochemical decomposition of hydrazine in water: effects of coal ash and pH on the decomposition and adsorption behavior.

Sonochemical decomposition of hydrazine in aqueous suspension of coal ash particles was investigated in the different pH solutions. It was clearly found that the initial rate of hydrazine decomposition and adsorption is strongly dependent on the amount of coal ash and pH. At pH1, the amount of the hydrazine adsorption on coal ash was very small and hydrazine was mainly decomposed by ultrasonic irradiation. At pH4, hydrazine was mainly adsorbed on coal ash and not decomposed by ultrasonic irradiation. At pH8, the sonochemical decomposition and the adsorption on coal ash proceeded simultaneously. These results were due to the interactions between the degree of the protonation of hydrazine, the electric charge of coal ash and the amount of OH radicals formed in the sonolysis of water.

Formation of formic acid, acetic acid and lactic acid from decomposition of citric acid by coal ash particles at room temperature.

It was found for the first time that citric acid was decomposed to formic acid, acetic acid and lactic acid in the presence of coal ash particles at pH 3 at 20 degrees C, while it was not decomposed at more than pH 5. The yield of organic acid at stirring time of 60 min is in the order of formic acid>acetic acid>lactic acid. Since citric acid dissociates to citric anion at more than pH 5, it was suggested that citric anion and negatively charged coal ash particles repelled electrically each other at more than pH 5, resulting in that citric acid could not be adsorbed and not be decomposed on coal ash. Based on the obtained results, the decomposition of citric acid at pH 3 was suggested to be due to catalytic effects of coal ash. Since formic acid and acetic acid can be used as a material of hydrogen fermentation, coal ash could be used as a catalyst to synthesize the important material for hydrogen fermentation from wastewater of citric acid.