•
Ethylene spent caustic comes from the caustic scrubbing of cracked gas from an
ethylene cracker. This liquor is produced by a caustic scrubbing tower. Ethylene product gas is contaminated with (g) and (g), and those contaminants are removed by absorption in the caustic scrubbing tower to produce (aq) and (aq). The sodium hydroxide is consumed and the resulting wastewater (ethylene spent caustic) is contaminated with the sulfides and carbonates and a small fraction of organic compounds. •
Refinery spent caustic comes from multiple sources: the
Merox processing of
gasoline; the Merox processing of
kerosene/
jet fuel; and the caustic scrubbing/Merox processing of
LPG. In these streams sulfides and organic acids are removed from the product streams into the caustic phase. The sodium hydroxide is consumed and the resulting wastewaters (cresylic for gasoline; naphthenic for kerosene/jet fuel; sulfidic for LPG -spent caustics) are often mixed and called
refinery spent caustic. This spent caustic is contaminated with sulfides, carbonates, and in many cases a high fraction of
organic acids. ==Treatment technologies==