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Abstract

The invention is a method of processing a waste liquid containing at least an organic quaternary ammonium hydroxide. The waste liquid is brought into contact with a cation-exchanging material so as to make the organic quaternary ammonium ions adsorbed by the material to thereby remove the ions from the liquid (adsorbing step), and optionally the cation-exchanged water obtained by the contact is again processed to separate and remove resist peelings and surfactants therefrom. The invention is also a method of processing the organic quaternary ammonium hydroxide-containing waste liquid for recovering a valuable substance of the organic quaternary ammonium hydroxide therefrom. The method comprises the adsorbing step and an eluting step of bringing an eluent into contact with the cation-exchanging material that has adsorbed the organic quaternary ammonium ions so as to elute the ions from the material followed by an electrolyzing step of electrolyzing the eluate obtained in the eluting step to recover an aqueous solution of the organic quaternary ammonium hydroxide. The anodic liquid drawn from the electrolytic cell in the electrolyzing step may be re-circulated to the eluting step to be used as an eluent therein. By the invention, an organic quaternary ammonium hydroxide-containing waste liquid may be processed efficiently and inexpensively to give a low-COD, clean processed water, which may be directly discharged into rivers and others. If desired, the valuable substance of the organic quaternary ammonium hydroxide may be recovered efficiently and inexpensively at a high purity level.

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First Claim