酸性环境下生物成因施氏矿物稳定性研究

Stability of biogenic schwertmannite in acidic solution

施氏矿物是酸性矿山废水中广泛存在的次生矿物,其形成和转化受环境pH值、温度和共存离子等条件影响。文中研究了酸性环境中生物成因施氏矿物和吸附了三价砷的生物成因施氏矿物,在不同温度和钾离子浓度条件下的稳定性。结果表明,老化温度的增加促进施氏矿物相的转变:4℃条件下,在15周的老化时间里,无砷及含砷施氏矿物均未发生相转变;而在40℃条件下,经过15周的老化,则无砷和含砷施氏矿物均发生了部分相转变。此外,钾离子浓度变化可以导致施氏矿物老化产物不同:生物成因施氏矿物在0.01mM钾离子条件下老化15周后的转化产物主要为针铁矿,在100mM钾离子条件下老化产物为黄钾铁矾和针铁矿。含As(Ⅲ)施氏矿物在0.01mM钾离子条件下老化15周后没有发生相转变,在100mM钾离子条件下发生了部分相转变,产物为黄钾铁矾。生物成因施氏矿物中的As(Ⅲ)使得矿物在环境中更加稳定。

Schwertmannites are secondary minerals widespread in acid mine drainages,and their development and transformations are controlled by environmental factors such as temperature,pH,and co-existing ions.In this study,the effects of temperature and ion concentration on the stability and transformation of biogenic and As-containing schwertmannites were investigated.The results showed that the increase of aging temperature favored mineral phase transformations（MPT）： for schwertmannites with and without As incubated for 15 weeks,MPT did not take place at 4 ℃,but partially occurred at 40 ℃.In addition,the change of potassium ion concentration resulted in different aging products of schwertmannites： for the biogenic schwertmannites incubated for 15 weeks,the major aging products were goethite and jarosite/goethite at potassium ion concentrations of 0.01 mM and 100 mM,respectively;for the As（Ⅲ）-containing schwertmannites incubated for 15 weeks,MPT did not occur when potassium ion concentration was 0.01 mM,whereas partial MPT took place and jarosite was the major aging products.Moreover,when exposed to temperature or pH fluctuation,As（Ⅲ）-containing schwertmannite appeared to be more stable than pure schwertmannite.