Natural attenuation of antimony in mine drainage water

鉱山廃液中ヒ素の自然浄化

間中 光雄*; 柳瀬 信之; 佐藤 努*; 福士 圭介*

Manaka, Mitsuo*; Yanase, Nobuyuki; Sato, Tsutomu*; Fukushi, Keisuke*

廃鉱山の廃水中アンチモンの自然浄化を研究した。鉱山から採取した廃水,ずり,沈殿物を鉱物学及び化学の観点から調べた。廃水の化学的性質を、現場においてはpH, ORP, EC測定で、また、実験室でのICP-MSとイオンクロマト測定により調べた。それらの結果から、ずり中のスティブナイトとアンチモン二次鉱物の溶解により生じたSbは、廃水中に絶えず生じる鉄沈殿物、特にシュベルトマナイトにより自然浄化されることがわかった。沈殿へのSb吸着のみかけの分配係数(Kd)は少なくとも10L/kgであった。

Natural attenuation was investigated for the antimony in the drainage water of an abandoned mine. Drainage water, waste rocks, and ocherous precipitates collected from the mine were investigated in terms of their mineralogy and chemistry. The chemistry of the drainage water was analyzed by measuring pH, ORP, and EC on site as well as by ICP-MS and ion chromatography. The results of these investigations indicated that Sb, which is generated by the dissolution of stibnite (SbS) and secondary formed Sb minerals in waste rocks, was attenuated by iron-bearing ocherous precipitates, especially schwertmannite, that form over time in the drainage water. Bulk distribution coefficients (Kd) for this Sb adsorption to the precipitates ranges up to at least 10 L/kg.