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A Study on Cation Extraction and Impurity Separation in Slag

슬래그 내 양이온 추출 및 불순물 분리 연구

  • Lee, Ye Hwan (Department of Environmental Energy Engineering Graduate School of Kyonggi University) ;
  • Kang, Hyerin (Department of Environmental Energy Engineering Graduate School of Kyonggi University) ;
  • Jang, Younghee (Department of Environmental Energy Engineering Graduate School of Kyonggi University) ;
  • Lee, Si-Jin (Department of Environmental Energy Engineering, Kyonggi University) ;
  • Kim, Sung Su (Department of Environmental Energy Engineering, Kyonggi University)
  • 이예환 (경기대학교 일반대학원 환경에너지공학과) ;
  • 강혜린 (경기대학교 일반대학원 환경에너지공학과) ;
  • 장영희 (경기대학교 일반대학원 환경에너지공학과) ;
  • 이시진 (경기대학교 환경에너지공학과) ;
  • 김성수 (경기대학교 환경에너지공학과)
  • Received : 2019.10.02
  • Accepted : 2019.11.05
  • Published : 2019.12.31

Abstract

The cation extraction and impurity separation were studied in order to investigate the recyclability of a slag produced from the steel refinery industry. Two types of slag (Slag-A, B) were collected and characterized in this study. The initial characterization by X-ray diffraction (XRD) and X-ray fluorescence (XRF) confirmed the existence of various kinds of ions in the slag such as Ca2+ (30 ~ 40%), Fe3+ (20 ~ 30%), Si4+ (15%), Al3+ (10%), Mn2+ (7%), and Mg2+ (3 ~ 5%). Inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis on the extracted slag using 2 M HCl as a solvent indicated that a higher concentration of Ca2+ was extracted as the S/L ratio was increased. The Ca2+ extraction concentration were found to be 8,940 mg L-1 (Slag-A) and 10,690 (Slag-B) mg L-1 when the S/L ratio for Ca2+ extraction was 0.1. However, the extract was strongly acidic ( < pH 1) at 0.1 S/L. Also the other ions (impurities) were extracted simultaneously in addition to Ca2+. To increase the purity of Ca2+ in order to transform the slag to a high value resource, a pH-swing was conducted. The impurities tended to precipitate at higher rate as the pH was increased. Notably, the Ca2+ rapidly precipitated above a certain pH and at a pH of 10.5, while the selectivity of Ca2+ was over 99%. It is expected that the aqueous solution in which high contents of Ca2+ was selectively dissolved in this study would be suitable for the carbonation process for reducing CO2 and for the production of calcium carbonate.

제철산업에서 발생하는 슬래그의 자원화를 위하여 슬래그 내 양이온 추출 및 불순물 분리 연구를 수행하였다. 두 종류(Slag-A, B)의 슬래그를 사용하였으며, XRD 및 XRF 분석을 통해 30 ~ 40%의 Ca2+와 함께 Fe3+ (20 ~ 30%), Si4+ (15%), Al3+ (10%), Mn2+ (7%), Mg2+ (3 ~ 5%), 등 이온으로 구성되어 있음을 확인하였다. 2 M의 HCl을 추출용제로 사용하여 S/L ratio 별로 슬래그 주입하였으며, 추출액의 ICP 분석을 통해 S/L ratio가 높아짐에 따라 Ca2+ 추출량이 증가하는 것을 확인하였다. Ca2+ 추출 시 최적 S/L ratio는 0.1이며 Ca2+ 추출량은 8,940 (Slag-A), 10,690 (Slag-B) mg L-1로 나타났다. 하지만 추출액은 강산성(< pH 1)을 띠었으며 Ca2+ 이외에도 타이온(불순물)이 추출되었다. 슬래그를 고부가가치의 자원으로 이용하기 위해 Ca2+의 순도를 증진시키고자 pH-swing을 진행하였다. pH가 증가함에 따라 불순물이 침전되었으나 일정 pH 이상에서 Ca2+의 침전량이 급증 하였다. pH-swing을 통해 불순물을 분리하고 Ca2+의 선택도를 증진시킬 수 있음을 확인하였으며 pH 10.5 조건에서 Ca2+ 선택도는 99% 이상으로 나타났다. Ca2+가 선택적으로 용해되어 있는 수용액은 탄산화 공정에 적용되어 CO2를 저감하고 탄산칼슘을 생산할 수 있을 것으로 기대된다.

Keywords

References

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