RU2135419C1 - Method of removing organic impurities from sewage - Google Patents

Abstract

FIELD: oxidative destruction of organic contaminations of natural and circulating water and sewage. SUBSTANCE: sewage is passed from mixture of iron chip and carbon- containing material in the presence of atmospheric air and hydrogen peroxide. Oxidative destruction catalyst includes iron compounds generated directly during purification process. In this case, organic impurities are oxidized with molecular oxygen and oxidation is activated by using H₂O₂/Fe²⁺, and hydrogen peroxide is used in amount of 30-40% of stoichiometric amount desired. EFFECT: greater efficiency of water purification process and reduced cost for carrying it into effect. 2 cl, 4 ex

Description

 The invention relates to methods for the oxidative destruction of organic pollutants of natural, circulating and wastewater and can be used in the purification of natural and wastewater from oil products, pesticides, organochlorine, nitroaromatic compounds, dyes and other substances hazardous to human health and the environment.

A known method of treating wastewater from organic pollution with Fenton's reagent using a catalyst - iron (II) sulfate [1]. The specific consumption of hydrogen peroxide for the destruction of phenolic compounds was 39.0 mol / mol with an Fe content of ⁺² 400 mg / L, initial concentrations of phenolic compounds 30-40 mg / L, reaction time 60 minutes, pH 3.0.

 The disadvantages of the method are the increased consumption of oxidizing agent and catalyst, as well as the duration of the destruction process.

 A known method of oxidative destruction of organic pollutants with oxygen and hydrogen peroxide using coals having catalytically active metal ions bound to surface complexes (Fe (II), Fe (III) [2]. The degree of purification by phenol reaches 88% at the initial concentration 10-50 mg / l and contact time - more than 60 minutes.

 The disadvantages of the method are the need for preliminary preparation of heterogeneous catalysts, insufficient degree of purification by organic contaminants and the duration of the destruction process.

 The closest to the proposed in essence and the achieved result is a method of treating wastewater from organic impurities by treatment with hydrogen peroxide in the presence of an iron-containing catalyst - siderite [3]. The degree of purification of wastewater from phenol 1 hour after the introduction of the reagents reaches 99.8% at an initial concentration of 0.05 mol / L and a specific consumption of hydrogen peroxide of 30 mol / mol.

 The disadvantages of this method are the increased consumption of the oxidizing agent and the duration of the destruction process.

 The purpose of the invention is to reduce the duration, reduce the specific consumption of the oxidizing agent and simplify the process while maintaining a high degree of purification of water from organic compounds due to catalytic destruction in the process of galvanocoagulation in the presence of hydrogen peroxide.

This goal is achieved by the fact that in the method of purification of wastewater from organic impurities, including passing it with pre-introduced oxygen and hydrogen peroxide through a charge from a mixture of iron chips and carbon-containing material, iron compounds generated directly during the purification process are used as an oxidation degradation catalyst, while organic impurities are oxidized with molecular oxygen, activated by a pair of H ₂ O ₂ / Fe ^+2, and the hydrogen peroxide taken in koliches ve 20-40% of the stoichiometric requirement.

 The essence of the invention lies in the liquid-phase oxidative destruction of organic pollutants present in water by galvanocoagulation in the presence of hydrogen peroxide.

As a result of the operation of the short-circuited Fe-C galvanic cell, iron is dissolved and intensively oxidized to Fe (II, III). When hydrogen peroxide is added to the treated water during galvanic coagulation, the conditions for the existence of the Fenton system Fe ^{+ 2} -H ₂ O ₂ are realized in flow mode:
Fe ⁰ - 2e ---> Fe ²⁺
Fe ²⁺ + H ₂ O ₂ ---> Fe ³⁺ + HO ^. + OH ^-
Fe ²⁺ + ^. OH ---> Fe ³⁺ + OH ^-
. OH + H ₂ O ₂ ---> HO ₂ ^. + H ₂ O
Moreover, the influence of O _{2 is} carried out not through the initial components, but through the intermediate products formed in the Fe ²⁺ -H ₂ O ₂ -S system (S is an organic substrate). The primary product of the oxidation of organic substances by Fenton's reagent is the substrate radical R $\genfrac{}{}{0ex}{}{\text{•}}{\text{α}}$ , which has reducing properties and, therefore, effectively reacts with O ₂ :
R $\genfrac{}{}{0ex}{}{\text{•}}{\text{α}}$ + O ₂ → RO $\genfrac{}{}{0ex}{}{\text{•}}{\text{2}}$
As experiments have shown, for the efficient process of destruction of organic impurities to occur, it is enough to introduce only 20-30% of the amount of hydrogen peroxide required by stoichiometry into the solution, which indicates that hydrogen peroxide is used only to activate oxidizable substrates with the formation of intermediate radicals, which are then oxidized by oxygen air. The amount of oxide radicals necessary for the oxidation of organic substrates is formed during the interaction of Fe (II) ions, continuously generated during the oxidation of iron scrap, with molecular oxygen. In addition, oxidative processes are intensified by the catalytic interaction of oxidizing radicals and oxygen with oxidizable substrates on the surface of a carbon-containing material modified with iron ions.

The method is confirmed by the following examples:
Example 1. Model solutions with an initial concentration of n-phenylenediamine 20 mg / l are subjected to galvanocoagulation without the addition of hydrogen peroxide and in its presence, taken in the amount required by stoichiometry. The duration of contact of the download with the solution is 5 minutes The cleaning effect without the addition of an oxidizing agent is 20%. After galvanic coagulation in the presence of hydrogen peroxide, n-phenylenediamine was not detected.

 Example 2. Model solutions containing pyrocatechol in concentrations of 20 mg / l are subjected to galvanic coagulation treatment without the addition of hydrogen peroxide and in its presence. The stoichiometry consumption of hydrogen peroxide is 14 mol / mol. Processing time 5 min. The cleaning effect in the absence of hydrogen peroxide is 50%; in the case of treatment with the addition of hydrogen peroxide, pyrocatechol was not found.

 Example 3. Model solutions of phenol with an initial concentration of 20 mg / l are subjected to galvanic coagulation treatment in the presence of hydrogen peroxide. Contact duration 5 min. After galvanic coagulation treatment with the addition of hydrogen peroxide in an amount of 30-100% of the stoichiometrically necessary phenol was not detected.

 Example 4. Conduct galvanic coagulation treatment of washing water of oxidative dyeing of sheepskin black, containing 19 mg / l of oxidative dyes, without the addition of hydrogen peroxide and in its presence. Processing time 30 minutes The degree of purification without the addition of hydrogen peroxide is 44%, while the purification efficiency in its presence is 83%.

 Fields of practical application: purification of natural, circulating, and wastewater from oil products, pesticides, organochlorine, nitroaromatic compounds, dyes, and other difficultly oxidized toxic pollutants.

 The proposed method has the following advantages: high efficiency of galvanic coagulation purification of water from organic contaminants in the oxidative degradation mode in the presence of hydrogen peroxide, namely, increasing the productivity and efficiency of the water purification process while reducing its costs. The proposed method does not cause secondary pollution, increase salinity.

Literature
1. Oxidative treatment of phenol-containing wastewater for thermal processing of oil shale / Preys SV, Kamenev SB, Kallas Yu.I. // Chemistry and water technology, 1994, 16, N 1, p. 83-91.

 2. The use of coal catalysts for oxidatively destructive wastewater treatment / Tarkovskaya IA, Stavitskaya SS, Lukyanchuk VM, Tarkovskaya GV. // Water chemistry and technology, 1993, 15, N 7- 8, p. 578-583.

3. A. p. 1386585 USSR, MKI ⁴ C 02 F 1/72. The method of wastewater treatment / I.I. Vasilenko, A.N. Fedosova, N.M. Shevel - Publ. 07.07.88, bull. N 13.

Claims (2)

 1. The method of purification of wastewater from organic impurities by treatment with hydrogen peroxide in the presence of an iron-containing catalyst, characterized in that the iron compounds used as a catalyst are obtained directly in the purification process by passing wastewater through a charge from a mixture of iron chips and carbon-containing material in the presence of atmospheric oxygen. 2. The method according to claim 1, characterized in that the oxidation of organic impurities by molecular oxygen is activated using a pair of H ₂ O ₂ / Fe ²⁺ , and hydrogen peroxide is taken in an amount of 30-40% of the stoichiometrically necessary.