廢酸化鐵觸媒에 의한 鍍金廢水中 크롬이온 回收에 관한 基礎硏究
A study on the recovery of chromium from metal-plating wastewater with spent catalyst
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초록
석유화학공정으로부터 폐기되는 폐산화철촉매를 이용하여 도금합성폐수중 크롬회수에 관한 연구를 회분식과 연속식으로 실시하였다. 도금합성폐수 중 CrO4-2 형태의 음이온으로 존재하는 6가 크롬은 폐산화철촉매의 등전점(pH 3.0)이하에서 폐촉매와 물리적 흡착을 한다. 한편, 6가 크롬은 pH 3.0이상에서도 폐촉매의 수산화철과 산화환원반응에 의해 일부 환원되어 Cr(OH)3로 침전한다. 컬럼을 이용한 크롬 연속회수실험에서 크롬합성폐수의 pH가 0.5 ～ 2.0일 때 폐촉매의 크롬흡착량은 2.0 g/L ～ 2.3 g/L이며, pH가 3.0 에서는 1.5 g/L이었다. 폐수 중 크롬농도가 50mg/L ～ 500mg/L로 높아질수록 폐촉매에 흡착한 크롬누적량은 1.29 g/L ～ 8.56g/L로 증가하지만, 유속이 30 ～ 80ml/min.으로 증가하여도 크롬 흡착누적량은 2.21 ～ 2.49mg/L 로 거의 유사하였다.
Abstract
A large tons of spent iron oxide catalyst come from the Styrene Monomer(SM) production company. It is caused to pollute the land and underground water due to the high alkali contents in the catalyst by burying them in the landfill. In order to recycle the spent catalyst, a basic study on the recovery of chromium ion from metal plating wastewater with the spent catalyst was carried out. The iron oxide catalyst adsorbed physically Cr+6 in the lower pH 3.0, that is the isoelectric point of the spent catalyst. It was found that the iron oxide catalyst reduced the Cr+6 into Cr+3 by the oxidation of ferrous ion into ferric ion on the surface of catalyst, and precipitated as Cr(OH)3 in the higher than pH 3.0. The Cr+6 was recovered 2.0 ～ 2.3 g/L catalyst in the range of pH 0.5 ～ 2.0, but it was recovered 1.5 g/L catalyst at pH 3.0 of wastewater. The recovery of Cr was increased as the higher concentration in the continuous process, but the flowrates were nearly affected on the Cr recovery.