Influence of ultrasonic waves in the reduction of nitrate to nitrite by hydrazine–Cu(II)

Abstract

Colorimetric methods are still important for determining nitrate and nitrite. A critical step in the use of these methods to determine nitrate in low concentrations is the reaction time required to totally reduce nitrate to nitrite, i.e., 24h in the dark. This work involved a study of the influence of ultrasonic irradiation on the nitrate reduction reaction by hydrazine. Our findings indicated that ultrasonic irradiation, associated with copper(II) ion as a catalyst, increased the redox reaction rate, decreasing the reaction time to about 10min when the power of the ultrasonic irradiation was set in 14.0357W. The strong influence of the ultrasonic irradiation in the reduction reaction rates can be sustained by an excellent linear correlation (R(2)=0.9993) between the kinetic constants and ultrasonic powers. Nitrate conversion also increased from 68% to 98% at the latter conditions. It thus become clear that high intensity ultrasound is very beneficial for this reduction reaction to proceed in good yield and in short reaction time in comparison to its silent reaction.

Determining the effect of system parameters on ultrasonic water disinfection and enhancing its efficiency with a hybrid application

“…In addition, whether the energy, as a result of the attenuation of the cavitation of other media ions, reduces the effectiveness of this disinfection process using a variety of different mechanisms must be examined. Silva , 2007), reported maximum efficiency of reduction of nitrate ions to nitrite accompanied by various catalysts was 68%. Furthermore, et al, et al, et al, et al it was observed that the efficiency of nitrite formation was 92% if the reduction process took place in an ultrasonic process.…”

“…For this reason, media ions such as sulphate (Jiang , 2006), bicarbonate (Jiang , 2006) and nitrate (Tauber , 2000;Silva 2007) in ultrasonic disinfection must be considered. It is acknowledged that a high amount of cavitation is created by the effect of forming weak points for the cavitation initiator by ions associated with the system Gogate, 2008).…”

Nitrate removal from water using UV-M/S2O4 2− advanced reduction process

“…Organic compounds (e.g., methanol) were used to reduce NO 3 -through a photochemical process but NO 3 -removal was only achieved under very high temperatures and pressures (Sato et al 1996). Hydrazine and hydroxylamine are reducing agents that burn rapidly in the presence of a salt catalyst to reduce NO 3 -to nitrite (Silva et al 2007). This process is not attractive due to its safety hazards and catalyst consumption.…”

A Glimpse of Recent Developments in Brazilian Analytical Chemistry

“…The most usual application of ultrasound is in extraction procedures, as for example cadmium and lead in foods (Aleixo et al 2004). Ultrasound can also be employed for generation of reagents as demonstrated for chloride and hypochlorite (Korn et al 2005a) and can also influence chemical processes, such as the reduction of nitrate to nitrite (Silva et al 2007c).…”