Views: 0 Author: Site Editor Publish Time: 2021-12-30 Origin: Site
Persulfate has the advantages of good stability, good water solubility, strong oxidation and friendly reaction products, which can make up for the shortcomings of other oxidants. The excessive decomposition of persulfate can produce a new active substance, sulfate free radical. There is a pair of lone pair electrons in SO4, whose oxidation ability is higher than that of persulfate itself, which is close to the half-life of hydroxyl radical SO4 (4s, 40 C), so that it can be more fully exposed to pollutants. Persulfate activation also produces OH, which oxidizes more refractory substances, such as polychlorinated biphenyls. Sodium persulfate usually exists in the form of ammonium salt, potassium salt and sodium salt, while sodium persulfate is often used in in-situ chemical oxidation technology.
Sodium persulfate (Na2S2O8 is also called sodium persulfate). White crystalline or crystalline powder. Tasteless. Tasteless. Molecular weight 238.13. It decomposes gradually at room temperature, decomposes rapidly in heating or ethanol, and decomposes oxygen to form sodium pyrosulfate. Water and platinum black, silver, lead, iron, copper, magnesium, nickel, manganese and other metal ions or their alloys can promote decomposition, rapid decomposition at high temperature (about 200 C), release hydrogen peroxide. It is soluble in water (20 70.4). Long time contact with skin can cause allergy. Attention should be paid to the operation. LD50895 mg/kg via oral cavity in rats.
Sodium persulfate is a stable strong oxidant. The production of free radicals by persulfate activation is of great significance to the removal of petroleum pollutants. Persulfuric acid can produce free radicals under the conditions of alkali, metal ions, metal minerals, heat and organic compounds, and its activation mechanism is also different.
Radical chemistry of persulfate
It has a pair of isolated electrons and has a strong ability of electron generation and oxidation. In theory, most organic pollutants can be oxidized to small molecular organic acids, and eventually mineralized to CO2 and H2. Many scholars have studied the products and mechanism of the reaction of SO with organic compounds. At present, three basic viewpoints, namely, electron transfer, hydrogen extraction and addition, have been gradually formed around the study of specific pollutants.
Reactions with aromatic compounds are mainly carried out by electron transfer. The same is true for electrophilic groups, which steal electrons from organic molecules during oxidation. The results show that the rate of oxidation is accelerated when the organic molecule contains amino (-nh2), hydroxyl (-oh) or alkoxy (-or) donor groups. On the contrary, there are electron capture groups nitro (-no2) and carbonyl (C=O) in the organic molecule, which will slow down the rate of oxidation.
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