Recovery of Tetra-Methyl Ammonium Hydroxide from Waste Solution by Ion Exchange Resin

概要

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Tetra-methyl ammonium hydroxide is used in various electric and electronic parts production processes such as semiconductor, liquid crystal display and printed circuit board. The discharged amount of this chemical reaches about 2,500 ton/year from one factory in Japan. The waste liquor discharged from the liquid crystal display production contains 0.53wt% tetra-methyl ammonium hydroxide, 60 mg/dm3 phenol and ppb level of metal ions. In the cation exchange reaction, tetra-methyl ammonium ion is captured on the cation exchange resin. Other non-ionic organic matter like phenol goes through the resin without being captured on it, the separation being attained in this step. In the elution step, tetra-methyl ammonium ion captured on the resin is released as tetra-methyl ammonium chloride into aqueous solution by the action of dilute hydrochloric acid. Tetra-methyl ammonium chloride is converted to tetra-methyl ammonium hydroxide by the reaction between tetra-methyl ammonium chloride and OH− type anion exchange resin. The process is composed of three steps: cation exchange, elution and conversion. The experiments were carried out using ion exchange resin column of 20 mmφ and 735 mm height, in order to clarify the recovery and purity of tetra-methyl ammonium hydroxide at each step.
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