Introduction to Oxidative Technologies for Water Treatment

Mechanisms of Sonochemical Transformation of Nitrate and Nitrite under Different Conditions: Influence of Additives and pH

“…Periodate is an oxidizing agent ( E 0 (IO 3 – /IO 4 – ) = 1.6 V) that has been used in AOPs . The effect of the addition of potassium periodate on the present sonochemical experiments is shown in Figure and Table , indicating a k and a final percentage of NO 2 – removal at 240 min in the same range as those obtained in the absence of the additive.…”

“…Periodate is an oxidizing agent (E 0 (IO 3 49 that has been used in AOPs. 15 The effect of the addition of potassium periodate on the present sonochemical experiments is shown in Figure 1 and Table 2, indicating a k and a final percentage of NO 2 − removal at 240 min in the same range as those obtained in the absence of the additive. However, the evolution of NO 3 − was higher and that of NINP was lower ([NO 3 − ]/[NINP] ratio of ∼1.7 vs 0.4), implying that a new oxidation pathway, highly favoring the oxidation to NO 3 − over the NINP evolution, can be proposed.…”

“…In the final stage of the collapse, the temperature inside the residual bubble or in the surrounding liquid is above 2000 K. In this situation, entrapped molecules of dissolved gases, vaporized water, and solutes can be brought to an excited state and dissociate. Sonolytic mechanisms are complicated processes, strongly dependent on the atmosphere of the system, i.e., Ar, O 2 , etc. − According to Merouani et al, up to 25 reactions can take place inside the O 2 and H 2 gas bubbles. Here, the main reactions are presented in a simplified set of equations.…”

Synergistic Removal of Cr(VI) with Stable Nanozerovalent Iron Particles and Ultrasound Assistance in the Presence of Organic Additives

“…Regarding the participation of Fenton-like reactions (involving surface or dissolved iron species and H 2 O 2 ) in pathway (IV), the mechanism is still under intense and controversial discussion in the literature and can be found elsewhere. ,,− There is consensus around iron cycling between Fe(II) and Fe(III) with HO • generation. A similar mechanism occurs when dissolved iron is replaced by iron nanoparticles, ,, as Fe 0 is oxidized to Fe(II) leading to Fenton reactions.…”

“…Equations (S1–S11) in the Supporting Information (SI) show a simplified set of reactions taking place in sonochemical aqueous systems under argon and in air, where the main species produced are HO • , H • , HO 2 • , and H 2 O 2 . Since these species can participate in the transformation of pollutants, this system is considered an AOP/ARP as well as a green technology because it does not require additional chemicals . In previous papers, , our group analyzed the reduction of Cr(VI) (0.3 mM, pH 2) using 850 kHz ultrasound in the presence of carboxylic acids (CAs), such as citric acid (Cit) and ethylenediaminetetraacetic acid (EDTA), under different atmospheres.…”