The purpose of this study was to suggest feasible disposal methods for heavy-metal-contaminated soil or mine tailings through solidification/stabilization. To improve the compressive strength and enhance the heavy-metal stabilization after solidification/stabilization, we used the industrial wastes (oyster shell powder and waste gypsum) and indigenous bacteria as immobilization agents. Three indigenous bacteria were isolated from each heavy-metal-contaminated soil or mine tailing site, and the bacteria were identified by cellular fatty acid composition analysis. The results of cellular fatty acid composition analysis showed that the closest strains of these bacteria are Brevibacillus centrosporus, Lysinibacillus sphaericus, and Bacillus megaterium. To the best of our knowledge, this research was the first report of biomineralization by Brevibacillus centrosporus. As a result of mixing additives with the optimum mixing ratio suggested in this study, the compressive strengths of specimens were satisfied in accordance with the US Environmental Protection Agency (EPA) waste treatment standard after 28 days of aging. Additionally, the results of the Toxicity Characteristics Leaching Procedure (TCLP) and Synthetic Precipitation Leaching Procedure (SPLP) analysis showed the successful immobilization of heavy metals after 28 days of specimen formation for solidification/stabilization.

본 연구에서는 표면개질 활성탄을 이용하여 수용액상에서 혼합 중금속(Cr6+, As3+)의 흡착능을 평가하였고 또한 표면개질 활성탄을 안정화제로 활용하여 해양오염퇴적물 내 As 및 Cr에 대하여 중금속 안정화 실험을 수행하였다. 실험결과, 흡착평형은 약 120분 후에 도달하였다. 또한, 중금속 등온 흡착 특성은 Freundlich 및 Langmuir 방정식을 이용하여 해석하였으며, 평형흡착 실험결과는 Langmuir 모델에 잘 부합되었고 As3+ (28.47 mg/g)가 Cr6+ (13.28 mg/g)보다 평형 흡착량이 많았다. Cr6+인 경우, 용액의 pH가 6에서 10으로 증가함에 따라서 흡 착량은 감소하는 것으로 나타났다. 하지만 pH 증가 변화에서 As3+의 흡착량은 미미한 증가를 보였다. 안정화 방법은 오염퇴적물에 표면 개질한 활성탄 첨가 후 120일간 습윤 양생하였다. 연속추출 실험결과로부터, 미처리 오염퇴적물과 비교해서 Cr 및 As의 이온교환, 탄산염, 산화물 및 유기물 존재 형태 합의 비는 각각 5.8% 및 7.6% 감소하였다.

In this study, an accelerated carbonation process was applied to stabilize hazardous heavy metals of industrial solid waste incineration (ISWI) bottom ash and fly ash, and to reduce CO2 emissions. The most commonly used method to stabilize heavy metals is accelerated carbonation using a high water-to-solid ratio including oxidation and carbonation reactions as well as neutralization of the pH, dissolution, and precipitation and sorption. This process has been recognized as having a significant effect on the leaching of heavy metals in alkaline materials such as ISWI ash. The accelerated carbonation process with CO2 absorption was investigated to confirm the leaching behavior of heavy metals contained in ISWI ash including fly and bottom ash. Only the temperature of the chamber at atmospheric pressure was varied and the CO2 concentration was kept constant at 99% while the water-to-solid ratio (L/S) was set at 0.3 and 3.0 dm3/kg. In the result, the concentration of leached heavy metals and pH value decreased with increasing carbonation reaction time whereas the bottom ash showed no effect. The mechanism of heavy metal stabilization is supported by two findings during the carbonation reaction. First, the carbonation reaction is sufficient to decrease the pH and to form an insoluble heavy metal-material that contributes to a reduction of the leaching. Second, the adsorbent compound in the bottom ash controls the leaching of heavy metals; the calcite formed by the carbonation reaction has high affinity of heavy metals. In addition, approximately 5 kg/ton and 27 kg/ton CO2 were sequestrated in ISWI bottom ash and fly ash after the carbonation reaction, respectively.

A stabilization/solidification (S/S) process for lead (Pb) contaminated soils was evaluated using waste cow bone containing apatite like compounds. Soil samples obtained form firing range were treated with waste cow bone. The effectiveness of stabilization was evaluated based on the Korean Standard Leaching Test (KSLT) and soil pH. The leached concentration reduced with increased in dose of waste cow bone. Overall, the KSLT results showed that Pb concentration in soils are significantly affected by amount of waste cow bone. When soil amended with 20 % of waste cow bone, less than 0.1 mg/kg was leached, and soil pH was increased from 6.5 to 8.4. Same results were obtained when finer waste cow bone was applied. The reachable concentration of Pb in soil showed in inversely proportional to solid/liquid ratio. Aging periods indicate improving mix design was applied. Relatively high lead concentrations was observed at the first 1 days, however leaching profile are reduced significantly over time for all mix designs.