In water treatment practice, factors should be considered to select the appropriate oxidizing or red

Here are a few things you can do here:

1. The difficulty of the reaction directly determines the effect of water treatment.

2. The rate and time of the reaction are the costs that water treatment can not be ignored.

3. Interference, if there is interference, it will inevitably affect the effect of treatment.

4. Side reactions, rewater treatment often leads to a large increase in the dose of drugs because of side reactions, 5. Secondary pollution, in the selection of agents, if the secondary pollution is caused by the introduction of agents, this is obviously not good.

6. Emission standards and emission requirements determine the choice of our program, including the choice of chemicals.

7. Economic factors, under the same effect (there are many times when the same effect is often not required, as long as it can meet the standard), give priority to economic things, which is universal.

8. The ease of use should also include, storage, various restrictive conditions for the use of fortune, etc.

9. Finally, the question of personal preference has to be considered, which includes the customer's preferences when let's go.

Okay, that's all I have in mind for the time being, and there may be more, and I hope someone will add it.

It can be considered from the following aspects:

1) It has a good redox effect on specific impurities in water.

2) The product after the reaction should be harmless and does not need to be re-treated.

3)**Reasonable, easy to obtain.

4) Rapid response at room temperature, no need to heat.

5) The pH required for the reaction is not too high or too low.

in water treatment practices. I don't understand.

Only Bu Chakuan answer]: refers to ears a, b, d

2021 p185 / 2020 p184 / 2019 p185

The bio-oxidation pretreatment technology mainly adopts the biofilm method, and its form is mainly submerged biological filter, such as TOC biodegradation, nitrogen removal, iron and manganese removal, etc.

Answers]: b, c, e

This question examines water treatment. The purpose of water supply treatment is to remove or reduce the suspended or old substances, colloids, harmful bacteria and other harmful substances contained in the raw water, so that the treated water quality can meet the needs of users. Textbook p185.

Answers]: a, b, c, d

2021 p185 / 2020 p184 / 2019 p185

3) (1) According to the different removal pathways of pollutants, the pretreatment method can be divided into oxidation method and adsorption method, among which the oxidation method can be divided into chemical oxidation method and biological oxidation method. The chemical oxidation pretreatment technology mainly includes chlorine pre-oxidation, potassium permanganate oxidation, ultraviolet photooxidation, ozone oxidation and other pretreatments; The bio-oxidation pretreatment technology mainly adopts the biofilm method, and its form is mainly submerged biological filter, such as TOC biodegradation, nitrogen removal, iron and manganese removal, etc. Repentance is attached to pretreatment technology, such as using powdered activated carbon to absorb and balance the adsorption, clay adsorption, etc.

Answers]: a, b, c, d

This question examines water treatment. The pretreatment technology of chemical oxidation mainly includes chlorine pre-reed oxidation, potassium permanganate oxidation, ultraviolet light oxidation, ozone oxidation and other pretreatments; The biofilm method is mainly used in the biological oxidation pretreatment technology, and its form is mainly submerged biological filter, such as TOC biodegradation, removal of nitrogen deficiency in wild areas, and removal of iron and manganese.

Answers]: a, b, c, d

1) Pretreatment method 1) Oxidation method Chemical oxidation method: chlorine pre-oxidation, potassium permanganate oxidation, ultraviolet light oxidation, ozone oxidation Biological oxidation method - biofilm method: submerged biological filter TOC biodegradation, nitrogen removal, bright manganese removal next to iron 2) adsorption method, powder activated carbon adsorption, clay adsorption (2) advanced treatment method, activated carbon adsorption Yungekuan method, ozone oxidation method, ozone activated carbon method, biological activated carbon method, photocatalytic dust oxidation method, blowing method, etc.

Oxidants commonly used in wastewater treatment are:

After accepting electrons, it is reduced to neutral atoms with negatively charged ions, such as O2, Cl2, O3, etc.;

Positively charged atoms are reduced to negatively charged ions after receiving electrons, such as Cl+ in hypochlorite ocl- and Cl4+ in chlorine dioxide in bleaching powder, sodium hypochlorite and other agents under alkaline conditions.

Positively charged atoms are reduced to low-valent positively charged atoms after accepting electrons, such as Fe3+ in ferric chloride and Mn7+ in potassium permanganate reduced to Fe2+ and Mn2+ after accepting electrons.

The reducing agents commonly used in wastewater treatment are:

After giving electrons, they are oxidized into positively charged neutral atoms, such as iron filings, zinc powder, etc.;

Negatively charged atoms are oxidized to positively charged atoms after giving electrons, for example, the boron element in sodium borohydride is negative 5 valence, which can reduce mercury ions to metallic mercury under alkaline conditions, and at the same time oxidize itself to positive trivalent.

A positively charged atom of a metal or non-metal that is oxidized into an atom with a higher positive charge after giving an electron. For example, ferrous sulfate and ferrous chloride are oxidized to ferric ion Fe2+ after giving one electron; The tetravalent sulfur in sulfur dioxide SO2 and sulfite SO32- is oxidized to hexavalent sulfur after giving two electrons to form SO42-.

This is a lot, dozens of transition metal elements of the aqueous solution of the salt reduction reaction with methanol, formaldehyde, ethylene glycol, glucose, ascorbic acid, hydrazine, etc., all belong to this type.

For example, when determining the total iron content in iron ore, Fe3+ is pre-reduced to Fe2+, and then titrated with the oxidant potassium dichromate, and when determining manganese and chromium, the sample is dissolved first, if they exist in the form of Mn2+ or Cr3+, it is difficult to find a suitable strong oxidant for direct titration. Ammonium persulfate can be used to oxidize them into permanganate ions and dichromate ions, and then a suitable reducing agent can be selected for titration. The redox step prior to this assay is called redox pretreatment.

Conditions:1Oxidation or reduction must quantitatively oxidize or reduce the components to be measured to a certain valence.

2.Excess oxidizing or reducing agents must be easily and completely removed.

3.The selectivity of the oxidation or reduction reaction should be good to avoid interference from other components in the sample.

4.The reaction rate should be fast.