Treatment of arsenic-containing acid mine drainage by micro-bubble flotation

Generally speaking, acid mine drainage (AMD) contains relatively high concentration of arsenic (As), which is a very toxic chemical element. A typical example is the Horobetsu sulfur mine, located in the northern Japan. The drainage from Holobetsu mine flows into Lake Toya, which without an effective treatment would affect the equilibrium of the ecosystem of the vicinity. Actually, the drainage from the Horobetsu mine is treated by using co-precipitation process with iron hydroxide in order to remove arsenic, followed by neutralization. The aim of the research is therefore to develop a new processing method for AMD, which could be another feasible treatment option. In other words, the objective is to investigate the removal of arsenic by micro-bubble flotation. The main finding of this study is that arsenic was effectively removed when mole ratio with sulfur of sulfating agent and arsenic was 6 and pH 2.8. The experimental results also suggested that arsenic concentration was reduced from 10.2 mg/L to less than 0.083 mg/L, indicating the efficiency of the micro-bubble flotation.