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Butadiene is marketed containing p-tertbutylcatechol (p-TBC), a polymerization inhibitor that should be removed before butadiene utilization in synthetic rubber production. p-TBC can be removed from butadiene by washing with sodium hydroxide (NaOH) solution, producing a wastewater with pH 14, which contains high amounts of p-TBC, a toxic chemical compound, The aim of this work was to develop a treatment process that could reduce the content of p-TBC from the wastewater. Since p-TBC is very soluble in basic, but not in neutral and acid solutions, acidification tests were performed with phosphoric acid (H3PO4) to precipitate p-TBC. Reaction between NaOH and H3PO4 can result in crystallization of large amounts of salt without p-TBC precipitation. Under selected acidifyfng conditions p-TBC precipitates and the wastewater COD is highly reduced (> 90%). Chromatographic determinations showed that the precipitated p-TBC could be recovered with 99% purity. [ABSTRACT FROM AUTHOR]