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소성처리에 의한 황토의 물성특성 변화 및 용존 중금속 제거능력

Changes in Physical Properties and Its Metal Removal Efficiency for The Yellow Soils by Calcination Process

  • 이진원 (군산대학교 환경공학과) ;
  • 김석휘 (고등기술연구원 플랜트엔지니어링본부) ;
  • 황갑수 (군산대학교 환경공학과)
  • Lee, Jin-Won (Department of Environmental Engineering, Kunsan National University) ;
  • Kim, Seokhwi (Center for Plant Engineering, Institute for Advanced Engineering) ;
  • Hwang, Gab-Soo (Department of Environmental Engineering, Kunsan National University)
  • 투고 : 2016.12.26
  • 심사 : 2017.04.07
  • 발행 : 2017.04.30

초록

수중에서 중금속은 흡착제에 의한 표면흡착과 금속수산화물로의 침전/제거반응이 동시에 일어나기 때문에 이들 각각에 의한 중금속 제거기작은 명확하게 구분되어 설명되지 못한다. 본 연구에서는 중금속 제거기작을 보다 명확하게 이해하기 위해 $850^{\circ}C$로 소성된 황토를 이용하여 다양한 pH 조건에서 Cu, Pb, Zn, Cd, 그리고 Cr 수용액 각각을 대상으로 회분식실험을 수행하였다. 실험결과 Cr을 제외한 중금속 농도는 반응초기에(<5분) 급격하게 감소되어 초기농도 대비 약 90%가 제거되었다. 한편, pH는 대상 금속 수용액에 따라 정도의 차이를 보이긴 하나 전체적으로 반응시간에 따라 지속적으로 증가되어 7.0-9.0까지 증가되었다. 반응시간에 따라 증가되는 pH 값과 높은 pH 조건에서 상대적으로 높은 중금속 제거율은 금속수산화물의 침전과 관련 있어 보인다. 흡착제(상용활성탄, 비소성황토, 소성황토)별 반응시간에 따른 pH 변화에 대한 비교실험결과, pH 증가현상은 소성황토에서만 두드러지게 나타나 소성과정에서 황토의 물성특성이 변화되었던 것으로 생각된다. 따라서 소성황토에 의한 중금속 제거는 흡착제에 의한 단순흡착뿐 아니라, 높은 pH 조건에서 금속수산화물을 형성함으로써 흡착질 표면에 침전 제어 될 수 있음을 보여준다.

Metal removal from water has not been explained clearly by either adsorption onto the surface of absorbents or precipitation as metal hydroxides because those occur simultaneously to a certain extent. For a better understanding of the metal removal mechanisms, batch experiments were performed using soil calcined at $850^{\circ}C$ under various pH conditions for Cu, Pb, Zn, Cd, and Cr. The results showed that the metal removal efficiency with the exception of Cr decreased abruptly, even within 5 min, showing more than 90% removal. The pH of each reactant increased gradually from around 7 to 9 with time. The increases in metal removal at higher pH appear to be associated with metal hydroxides precipitation. Comparative experiments, which were carried out changing the pH by reacting with commercial activated carbon (CAC), natural yellow soil (NYS), and calcined yellow soil (CYS), showed that the pH of the CYS only increased with time. Calcination processes might lead to a change in the physical properties of the soil matrix resulting in a high pH when reacted with water. Apart from adsorption onto the surface of the absorbents, these results show that the adsorption and/or precipitation of hydroxides onto the surface of adsorbents also play important roles in regulating the dissolved metals under alkaline conditions.

키워드

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