Development of the Inorganic Coagulants Using Red Mud and Evaluation of Its Coagulation Performance

적니를 이용한 무기응집제의 개발 및 응집성능 평가

Red mud is generated as a by-product during the production of aluminum hydroxide from bauxite ore. In this study the red mud coagulants were prepared by reacting 100 ml of 5 M $H_2SO_4$ solution with 10g of red mud at $85^{\circ}C$ or by reacting 100ml of 9M HCl solution with 10g of red mud at $25^{\circ}C$. The prepared red mud coagulants were tested for their coagulation performance of pollutants in the municipal and industrial wastewater. In addition, the coagulation performance was compared with that of a commercially available coagulant ($FeCl_3$). As a result, the red mud coagulants were found to have a good removal efficiency of pollutants in the municipal wastewater (turbidity, phosphate phosphorus) and in the plating wastewater (turbidity, $Pb^{2+}$, $Cd^{2+}$, $Cu^{2+}$, $Zn^{2+}$, $Cr^{3+}$). In the experiment to remove COD in the petrochemical wastewater, the COD removal efficiency by the red mud coagulants was a little poor, but it was better than that by $FeCl_3$.

적니는 보오크싸이트로부터 수산화알루미늄/알루미나를 제조하는 공정에서 발생되는 부산물이다. 본 연구에서는 적니 10g을 100ml의 5M $H_2SO_4$과 $85^{\circ}C$에서 반응시키거나 100ml의 9 M HCl과 $25^{\circ}C$에서 반응시켜 무기응집제인 적니응집제를 제조하였다. 이렇게 제조한 적니응집제의 응집성능은 실제폐수에 투입량을 변화시켜 투입한 후 여러 pH 값에 대하여 오염물질 제거효율로써 조사하였고 시판용 무기응집제($FeCl_3$)의 제거효율과도 비교하였다. 생활하수(탁도, 인)와 도금폐수(탁도, $Pb^{2+}$, $Cd^{2+}$, $Cu^{2+}$, $Zn^{2+}$, $Cr^{3+}$)의 실제폐수를 처리한 결과 적니응집제의 응집성능은 우수하였다. 그리고 적니응집제를 이용한 석유화학폐수중의 COD를 처리한 결과, 제거효율은 다소 낮았으나 시판용 무기응집제보다는 우수하였으며 응집보조제로서 양이온 고분자응집제 첨가시 가장 효과적인 것으로 확인되었다.