CS263327B1 - A method of purifying waste water containing anionic surfactants - Google Patents

Abstract

The procedure concerns the treatment of wastewater containing anionic surfactants based on sulfates, alkyl sulfonates, alkene sulfonates, alkyl aryl sulfonates or sulfonic fatty acids with a concentration higher than 200 mg.l~l. If the mass ratio of surfactants reacting with barium salt to the content of other surfactants is higher than 2.5, after adding a water-soluble barium salt in an amount of 2 to 7 g.l"1, preferably 3 to 4 g.l”·1·, demulsification of oil substances or fats occurs. This process can be accelerated by mechanical mixing and the demulsified oil substances or fats can be separated by gravity mainly in the form of a free phase.

Description

The process relates to the purification of waste waters containing amphipathic emulsifiers based on sulfonates, alkylsulfonates, alkylarylsulfonates or sulfonated fatty acids, by precipitating them with a water-soluble barium salt.

Presently, solutions of strong acids, clarifiers, sorbents, etc. are used for the purification of waste waters containing emulsified petroleum substances or fats stabilized by anionic surfactants. For anionic surfactants produced today, the biodegradability must be at least 80% (depending on the reaction with methylene blue). Nevertheless, the demands on the purity of the discharged water into the watercourse are high. In waterways, the concentration of anionic surfactants should not exceed 0.1 mg.l -1 (sodium dodecyl sulphate standard). In other streams, a maximum concentration of 3 mg of anionic and nonionic surfactants is permitted. AND"'*·.

The essence of the proposed solution is the precipitation of amphipathic emulsifiers based on sulphates, alkylsulphonates, alkenesulphonates, alkyl arylsulphonates or sulphonated fatty acids with a water-soluble barium salt. Advantageously, waste from the heat treatment of materials, in particular salts, can be used for the preparation of heating, annealing and quenching baths, as well as for cementing. They contain mostly barium chloride, sodium chloride, potassium chloride, sodium carbonate, event. borax and calcium chloride.

To the effluent was added to the water-soluble barium salt in an amount gl "\ preferably 3« ^ - gl ^- ^ · sulfated or sulfonated surfactants inactivate and reduce the stability of the emulsified oil or fat and results in the formation of aggregates of droplets with there subsequent coalescence. This process can be accelerated by mechanical stirring. De-emulsified petroleum substances and here

- 2 263 327 ky are separated by gravity mainly in the form of the free phase. The alkyl sulfates form an insoluble barium sulfate with the barium salt, and the sulfonated surfactants precipitate as barium salts. A condition for the successful separation of the dispersed phase, the content of other surfactants that do not react with the barium salt (soluble in H ₂ 0) was too high. The weight ratio of sulphates, alkylsulphonates, alkenesulphonates and alkylarylsulphonates and sulphonated fatty acids to the content of other surfactants present in the waste water must be higher than 2.5.

The process is suitable for pre-treatment of waste waters with a high content of emulsified petroleum substances and fats, since some of the unreacted barium salts remains in the purified water, which must be removed in the next treatment stage. E.g. clarification of all waste water from the plant with aluminum sulphate.

The process for the purification of waste water containing anionic surfactants is further described in two exemplary embodiments.

Example 1.

The waste water contained 10.25 g ^{-1 of} emulsified petroleum substances. The content of alkylarylsulfonates in the wastewater was 510 mg.l ^-1 and the weight ratio of alkylarylsulfonates to other surfactants was 2.55. Crystalline barium chloride was added to the wastewater in an amount of 3 gl ^-1 . After 15 minutes of stirring and 1 hour separation, the residual oil content in the pre-treated water was 50 mg.l ^-1 and the anionic surfactant content was 51.5 mg.l ^-1 (as sodium dodecyl sulphate), the cleaning effect in the case of oil removal was 98.5 %.

Example 2.

The waste water contained 12.6 g / ^{l of} emulsified petroleum substances. The sulphonated castor oil concentration was 1030 mg.l ^-1 and the weight ratio of the sulphonated castor oil to the other surfactants was 5.0 · After addition of 3 g / ^l BaCl ₂ .2H ₂ 0 and stirring for 15 minutes the deemulsified petroleum substances were separated by for 1 hour. The residual oil content was 210 mg.l ^-1 and the anionic surfactant content was 19.6 mg.l ^-1 (as sodium dodecyl sulphate).

Claims (1)

SUBJECT OF THE INVENTION 263 327 A method for the purification of waste waters containing anionic surfactants based on sulphates, alkylsulphonates, alkenesulphonates, alkyl arylsulphonates and sulphated fatty acids at a concentration of more than 200mg.I ' ^1, characterized in that if the weight ratio greater than 2.5 »is added to the waste water soluble barium salt in an amount gl" ^1, preferably 3 · ^ * gl ^"1 ·