粤北大宝山槽对坑酸性矿山废水中不同沉积层次生矿物研究

矿山尾矿渣中硫化物的氧化作用易形成酸性矿山废水(AMD)和重金属污染,而氧化过程中形成的次生矿物对控制重金属污染起重要的作用。本文利用XRD和SEM等主要手段,对粤北大宝山多金属矿槽对坑酸性矿山废水四种不同颜色沉积层的次生矿物种类及其形貌进行了研究,发现不同沉积层均有丰富的次生矿物。从上到下,次生矿物种类从简单变复杂多样。尾矿砂层(S1)次生矿物种类主要为叶绿矾、针绿矾、黄钾铁矾;赭色层(S2)主要次生矿物有磷铝矾、七水铁矾,四水白铁矾、黄钾铁矾等;灰绿色沉积层(S3)主要有水砷铁矿,镁叶绿矾、赤铁矾及较丰富的李时珍石;S4层主要有黄钾铁矾、施威特曼石、铁明矾、水绿矾、镁叶绿矾等。其中黄钾铁矾是最常见的次生矿物,主要呈片状、菱面体状,与施威特曼石共生;施威特曼石也相对较富集,呈海胆状、放射状、鳞片状、球状等集合体产出;石膏较富集,呈完整晶体出现。酸性矿山废水中重金属元素的活动性受到次生矿物的影响;次生矿物在一定程度上能净化酸性矿山废水中有害元素,减少酸性矿山废水对周围环境的污染。

A Study on Secondary Minerals in Different Sediments of Caoduikeng Acid Mine Drainage, Dabaoshan Mine, North Guangdong Province, China

Acid mine drainage (AMD) is a potential environmental problem. The oxidation of sulfide minerals contributes to the formation of AMD and heavy metal contamination around mine wastes. Secondary minerals produced by the oxidation process play an important role in controlling heavy metal pollution. Therefore, samples collected from four sediments with different colors in Caoduikeng AMD were analyzed and secondary minerals in the AMD were commonly found. The composition of sediments was analyzed by ICP-MS and XRD and the morphology of secondary minerals was characterized by SEM. Our study suggests that secondary minerals are rich and different in various sediment layers and becoming more complex from the uppermost to the lowest layer. They are mainly copiapite, coquimbite and jarosite in the uppermost sediment layer (S1), hotsonite, kornelite,rozenite and jarosite in the ocher sediment (S2), kaatialaite, magnesiocopiapite, botyogen as well as rich lishizhenite in the greyish-green sediment layer (S3), and more jarosite, schwertmannite, halotrichite, melanterite and magnesiocopiapite in the lowest layer. Of the studied secondary minerals, jarosite is the most common mineral that occurs in schistose and rhomb structure, and some of them intergrowth with schwertmannite. Schwertmannite occurs in aggregates as urchin-like, acicular, scaly-like and near spherical rosette. Gypsum is also an abundant mineral that occurs in perfect crystals. The secondary minerals affect the activation of heavy metals in AMD and purify harmful elements to some extent so as to reduce the AMD pollution.