Method for separating and recovering phosphoric acid from acetic acid-nitric acid-phosphoric acid series mixed acid waste liquor

Abstract

The invention relates to a method for separating and recovering phosphoric acid from acetic acid-nitric acid-phosphoric acid series mixed acid waste liquor. The method disclosed by the invention is characterized by comprising the following steps of: an acetic acid-nitric acid extracting step: mixing waste liquor containing acetic acid, nitric acid and phosphoric acid with an extracting agent solution of aliphatic series straight-chain saturated hydrocarbon which contains phosphoric trialkyl ester and 6-13 carbon atoms and selectively dissolving and extracting acetic acid and nitric acid from the extracting agent solution; a phosphoric acid recovering step: recovering the phosphoric acid from extracting waste liquor obtained in the extraction step; and an acetic acid-nitric acid stripping step: enabling the extracting agent solution containing the acetic acid and the nitric acid, obtained in the acetic acid-nitric acid extracting step, to be in contact with stripping water so that the acetic acid and the nitric acid are dissolved and transferred to the stripping water. The extracting agent solution is recycled by feeding the oil-phase extracting agent solution obtained in the acetic acid-nitric acid stripping step to the acetic acid-nitric acid extracting step. By means of the invention, the favorable separability of oil phase and aqueous phase in the stripping step can be maintained for a long time, and the phosphoric acid can be selectively and favorably separated and recovered from the acetic acid-nitric acid-phosphoric acid series mixed acid waste liquor for a long time with high efficiency.

Description

technical field [0001] The present invention relates to a method for separating and recovering phosphoric acid efficiently and selectively over a long period of time from acetic acid-nitric acid-phosphoric acid mixed acid waste liquid discharged from, for example, a liquid crystal manufacturing process or a semiconductor manufacturing process. A method in which the extractant liquid is supplied to the extraction step and the extractant liquid is recycled for a long period of time. Background technique [0002] In recent years, liquid crystal manufacturing industry and semiconductor manufacturing industry, which have developed rapidly, generate various waste water in the manufacturing process, and carry out appropriate treatment according to the type and nature of each waste water before discharging. For example, mixed acid waste liquid mixed with acetic acid, nitric acid, and phosphoric acid is generated from liquid crystal manufacturing steps or semiconductor manufacturing ...

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Problems solved by technology

[0006] However, in order to use 22 mixer-settlers for verification with a tank volume of about 200L (about 100 times that of a small machine), and carry out with the minimum level of circulation necessary for commercial operation and the supply of waste mixed acid, for example, the mixer-settler of the proof machine must be The shearing speed at the top of the machine is increased to about 100m / min compared to about 37-38m / min for small machines. Mixed acid supply), that is, if the shear velocity at the top of the mixer is increased, separation failure will occur in the above-mentioned peeling step, and there is a problem that phosphoric acid cannot be separated and recovered.

[0007] That is, due to the enlargement of the scale, an emulsified state that is difficult to break is formed when stirring in the mixing tank of the peeling step, so that the emulsification of the oil phase and the water phase cannot be released even in a standing state in the settling tank of the peeling step, so The separability of the oil phase and the water phase is reduced, so the stripping cannot be sufficiently performed. As a result, the content of acetic acid-nitric acid as impurities in the extractant liquid of the oil phase produced in the stripping step increases, so even if the extractant liquid produced in the stripping step The extractant liquid is supplied to the next acetic acid-nitric acid extraction step to be recycled, and it is difficult to fully extract the acetic acid and nitric acid in this step, so that a considerable amount is mixed in the raffinate (the phase obtained by separating phosphoric acid). Acetic acid-nitric acid, there is a problem that it is difficult to recover high-purity phosphoric acid

This problem does not exist on a small scale at the experimental level, but when the scale is scaled up to the commercial operation level of actual equipment, the separation of the oil phase and the water phase due to the above-mentioned emulsification of the oil phase and the water phase is significantly reduced.

That is, in the technical scheme of recycling the extractant liquid described in the above-mentioned Patent Document 1 (claim 6), when the scale is enlarged to the commercial operation level, the high-purity phosphoric acid aqueous solution cannot be recovered

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