Chemical solvent DMF wastewater pretreatment process overview
DMF is a kind of transparent liquid, with water and most organic solvents miscibility, it is the commonly used solvents, the chemical reaction of the pure DMF is odorless, but industrial-grade or metamorphic DMF has fishy, DMF is the polarity of the high boiling point (
DMF light colorless, liquid ammonia smell, the molecular weight of 73.
10 and relative density of 0.
Melting point -
62 ℃, boiling point of 152.
8 ℃, flash point, 57.
78 ℃, vapor density. 2.
51, vapor and air mixture explosion limit 2.
2%, with water and organic solvents miscibility usually, and petroleum ether mixed layer.
In open flame, high heat can cause burning explosion.
With concentrated sulfuric acid, fuming nitric acid reaction or even an explosion.
Danger tags 7 (
DMF wastewater in pesticide, medicine, petrochemical and synthetic leather and other industrial production of the wastewater contains a large number of DMF, each year only tanning industry emissions about 100 million tons of wastewater containing DMF.
the maximum allowable ground water quality concentration recommended value is 25 mg/l, because the DMF as an organic solvent and not only produces chemical reaction, almost no loss in quantity, all into production wastewater, such as do not add processing, will be caused great pollution to the environment.
common DMF wastewater treatment technology with biological method, chemical method,
The chemical method (
Catalytic oxidation, supercritical water oxidation, alkaline hydrolysis)
The above all kinds of methods to adapt to the different concentrations of DMF wastewater treatment respectively.
DMF solvent extraction wastewater is incompatible with water and certain organic density less than water and treated water contact, through physical or chemical effect, make original dissolved in water of some components of water phase transfer to the process of the organic phase, the relatively high concentrations of DMF wastewater (
Especially with aqueous solution of calcium chloride)
, usable CH2CL2, dichlorobenzene, chloroform, benzene, cyclohexanone or benzene methyl ether as extraction agent for recovery of DMF.
A tannery mass concentration is as high as 93.
4 g/l of DMF wastewater, using chloroform after five counter-current extraction, extraction residue DMF concentration to 1.
33 g/l, the extraction rate was 98.
6%, extract decodes distillation separation recycling CHCL3 and DMF, extraction residue after activated carbon adsorption of COD can be dropped to 100 mg/l, waste water containing high concentration of pesticide DMF concentration is about 10%, the recovery DMF with solvent extraction method is effective, the law also have the effect that avoid DMF decomposition at high temperature.
extraction temperature on the DMF from aqueous phase separation effect: the influence of temperature is an important factor in extraction operation.
When choosing extraction temperature, temperature should be as close as possible to deal with the waste water, this would not have to increase the heat exchange process, can reduce energy consumption, considering the industrial application, in 293.
Of DMF - water
Chloroform system to determine the equilibrium data,
salt content on the DMF from the effects of the water phase separation in 293.
DMF - 15 k under different salt content
Liquid-liquid equilibrium data of chloroform system.
Na2so4 in DMF wastewater is a kind of common salt, the existence of salt increases the selectivity of chloroform in DMF, with the increase of salt content, salt effect strengthen, DMF selective coefficient increased.
System, therefore, salt is good for extraction treatment of low concentration DMF wastewater.
centrifugal extraction solvent extraction method is simple, suitable for processing recovery value of organic matter, but can only be used for non-polar organic compounds, by extraction of organic compounds and waste water after extracting needs further processing, organic matter also may cause secondary pollution.