Work

Seasonal variation in water quality and evaluation of optimal iron removal conditions in acid mine drainage at A mine, Japan

Year: 2026

Type: article

Abstract: Acid mine drainage (AMD) often contains high concentration of iron (Fe), which can exceed 100 mg/L, while speciation and precipitation are key factors controlling the removal efficiency of Fe and other elements. This study monitored seasonal variations in AMD quality at A mine, Japan (pH: 2.6–3.2, Total-Fe: 128–162 mg/L), and found the dominant dissolved Fe species shifted from ferrous ion (Fe(II) aq ) in summer to ferric ion (Fe(III) aq ) in winter. Neutralization experiments using simulated AMD containing either Fe(II) aq or Fe(III) aq revealed that initial Fe speciation had little effect on arsenic and copper removal efficiency at this site. Furthermore, the reaction experiments using natural AMD in the presence or absence of Fe precipitates (5 v/v%) revealed the Fe(II) aq oxidation rate was 3 × 10 5 and 8 × 10 5 times higher in the presence of Fe precipitates at pH 3.0 and 3.5, respectively. Fe(II) aq oxidation was reduced substantially when using autoclaved Fe precipitates, suggesting that Fe(II) aq oxidation might be enhanced by processes associated with Fe precipitates, including microbial activity, rather than by homogeneous chemical oxidation alone. Therefore, promoting interaction between AMD and Fe precipitates, together with slight pH adjustment, could be effective for Fe removal from AMD at A mine.

Source: Scientific Reports

DOI: 10.1038/s41598-026-73325-w