methylene chloride, with the molecular formula CH2Cl2, is a colorless and transparent liquid with the advantages of strong solubility and low toxicity. It is slightly soluble in water and is a non-flammable low-boiling solvent.
methylene chloride is widely used in chemical production. As a raw material, it is widely used in the manufacture of polycarbonate; as a reaction medium, it is used in the preparation of ampicillin, oxypicillin and cephalosporin in chemical industries such as pharmaceuticals; as an organic solvent , can be used as organic synthesis extractant and so on.
The environmental data for dichloromethane are as follows:
Boiling point: 40.1 ℃
Solubility in water: 13.2 mg/L
Relative density (water=1): 1.33
Animal LD50: 1600~2136 mg/kg
COD value: 0.38 g/g
Odor threshold: 0.912 mg/L
From the above data, it can be seen that dichloromethane has a low boiling point, very low solubility in water and relatively high density with water. Therefore, for dichloromethane in wastewater, the following two methods can be used:
1) The dichloromethane is naturally separated from the aqueous phase by the method of standing;
2) Stripping method: methylene chloride escapes from waste water by heating;
3) Precipitation method: Dialkylamine (such as diethylamine, dibutylamine, etc.), sodium hydroxide and carbon disulfide can be added to the wastewater to generate dialkylamine sodium xanthate, and then in the presence of oxygen, it can be mixed with methylene chloride forms a solid precipitate;