處理水 再使用을 위한 칼슘 沈澱法에 의한 弗素廢水 處理 特性
Treatment Features of Fluorine-containing Wastewater Using Calcium as a Precipitant for Its Reuse
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초록
불소함유 폐수의 처리 후의 재사용 방안과 관련하여 칼슘을 침전제로 한 침전법에 의한 불소제거양상에 관해 조사하였다. 초기 불소농도를 10mM로 고정한 상태에서 pH4의 조건에서 칼슘 첨가에 따른 불소의 제거는 반응개시 수 분 이내에 신속히 진행되었으며 반응속도론적으로 2차 반응을 따르는 것으로 파악되었다. 또한 첨가된 칼슘의 양이 증가할수록 반응속도상수가 커지는 것으로 관찰되었다. pH4에서의 불소제거율을 최대제거율로 설정한 상태에서 pH2 및 pH3의 조건에서 칼슘을 당량비 이상으로 첨가하여 불소의 제거율을 관찰한 결과, 칼슘의 첨가량이 당량비의 10 배로 첨가되었을 때 pH2에 대해서는 불소제거율이 약 70%, 그리고 pH3에서는 약 96%의 불소가 제거되는 것으로 나타났다. 온도의 증가시 칼슘 첨가에 따른 불소의 제거율은 상승하여 침전반응은 흡열반응의 특성을 나타내었다. 불소폐수에 SiF62가 공존할 경우 불소의 제거율은 감소하였으며 침전반응에 의해 형성된 침전물의 등전점은 pH5 부근인 것으로 파악되었다.
Abstract
The characteristics of fluorine removal from wastewater have been investigated by precipitation method using calcium as a precipitant for the purpose of the reuse of treated wastewater. In the conditions of 10mM of the initial concentration of fluorine and pH4, the precipitation of fluorine was rapidly progressed within a few minutes after the precipitant was added and the precipitation of fluorine was observed to follow a second order reaction. Also, as the addition of precipitant was increased, the reaction rate constant of fluorine precipitation was found to rise. Postulating that the maximum fluorine removal was attained at pH 4, about 70% of fluorine was precipitated compared with the maximum removal when 10 times of equivalent amount of calcium was employed at pH2 and the fluorine removal was about 96% compared with its maximum value at pH3 under the same addition of precipitant. The fluorine precipitation reaction was found to be endothermic and the coexistence of SiF62 with fluorine resulted in its less removal. Finally, the isoelectric point of the precipitate was examined to be ca. pH5.
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