폐광산 지역 폐광석 및 광미에서 비소의 고정 메커니즘과 용출특성 = Mechanisms of Immobilization and Leaching Characteristics of Arsenic in the Waste Rocks and Tailings of the Abandoned Mine Areas

국문 초록 (Abstract)

EPMA분석결과, 철망간-(산)수산화광물과 결정질 철-(산)수산화광물에서 각각 $0.3-11.0wt.\%$와 $2.1-7.4wt.\%$인 적은 양의 As가 검출되었다. 비정질 철-(산)수산화광물에는 $28-36wt.\%$ 범위의 다량의 As가 인지되었고 $As_2O_5-SO_3-Fe_2O_3$ 다이어그램에 도식한 결과 스코로다이트에 근접하였다. 용해된 As는 철망간-(산)수산화광물과 철-(산)수산화광물에 흡착되고 스코로다이트와 같은 2차광물로 침전되어 저감되고 있었다. 용출실험은 산성환경에서 As와 Fe의 용출특성을 알아보고자 실시하였다. 반응용액의 pH 3과 5에서 용출된 As의 함량은 청양광산의 광미의 경우, 7일 이후에 뚜렷이 증가하였으며(전체 함량의 최대 $2.4\%$), 이는 As를 함유한 2차 광물들의 용해에 인한 것으로 판단된다. 반면에 서보광산의 광미에 함유된 As는 거의 용출되지 않았다(전체 As함량의 $0.0-0.1\%$). pH 1의 용출실험결과, 서보광산과 청양광산의 광미는 각각 $1.1-4.2\%$와 $1.5-14.4\%$의 As가 용출되었으며 As와 Fe는 밀접한 상관관졔가 있는 것이 관찰되었다. 용출실험에서 kinetics 문제는 우기에 As 농도를 증가시킬 수 있는 중요한 요인이 된다. 청양광산의 광미에 함유된 As는 지표수와 지하수의 수질에 악영향을 미칠 수 있다. 반면에 서보광산의 광미의 경우, As의 이동은 2차 광물의 침전과 흡착을 통해서 제어되는 것으로 나타났다.

다국어 초록 (Multilingual Abstract)

EPMA determined that Fe(Mn)-(oxy)hydroxides and well-crystallized Fe-(oxy)hydroxides and could contain a small amount of As $(0.3-11.0\;wt.\%\;and\;2.1-7.4\;wt.\%\;respectively)$. Amorphous crystalline Fe-(oxy) hydroxide assemblages were identified as the richest in As with $28-36\;wt.\%$. On the ternary $As_2O_5-SO_3-Fe_2O_3$ diagram, these materials were interpreted here as 'scorodite-like'. Dissolved As was attenuated by the adsorption on Fe-(oxy) hydroxides and Fe(Mn)-(oxy) hydroxides and/or the formation of an amorphous Fe-As phase (maybe scorodite: $FeAsO_4\cdot2H_2O$). Leaching tests were performed in order to find out leaching characteristics of As and Fe under acidic conditions. At the initial pHs 3 and 5, As contents dissolved from tailings of the cheongyang mine significantly increased after 7 days due to the oxidation of As-bearing secondary minerals (up to ca. $2.4\%$ of total), while As of Seobo mine-tailing samples was rarely released (ca. $0.0-0.1\%$ of total). Dissolution experiments at an initial pH 1 liberated a higher amount of As (ca. $1.1-4.2\%$ of total for Seobo tailings, $1.5-14.4\%$ of total for Cheongyang tailings). In addition, good correlation between As and Fe in leached solutions with tailings was observed. The kinetic problems could be the important factor which leads to increasing concentrations of As in the runoff water. Release of As from Cheongyang tailings can potentially pose adverse impact to surface and groundwater qualities in the surrounding environment, while precipitation of secondary minerals and the adsorption of As are efficient mechanisms for decreasing the mobilities of As in the surface environment of Seobo mine area.

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