Suteerapataranon Siripat, Bouby Muriel, Geckeis Horst, Fanghänel Thomas, Grudpan Kate
Forschungszentrum Karlsruhe, Institut für Nukleare Entsorgung, Postfach 3640, D-76021 Karlsruhe, Germany.
Water Res. 2006 Jun;40(10):2044-54. doi: 10.1016/j.watres.2006.03.009.
The release of metal ions from a coal mining tailing area, Lamphun, Northern Thailand, is studied by leaching tests. Considerable amounts of Mn, Fe, Al, Ni and Co are dissolved in both simulated rain water (pH 4) and 10 mg L(-1) humic acid (HA) solution (Aldrich humic acid, pH 7). Due to the presence of oxidizing pyrite and sulfide minerals, the pH in both leachates decreases down to approximately 3 combined with high sulfate concentrations typical to acid mine drainage (AMD) water composition. Interaction of the acidic leachates upon mixing with ground- and surface water containing natural organic matter is simulated by subsequent dilution (1:100; 1:200; 1:300; 1:500) with a 10 mg L(-1) HA solution (ionic strength: 10(-3) mol L(-1)). Combining asymmetric flow field-flow fractionation (AsFlFFF) with UV/Vis and ICP-MS detection allows for the investigation of metal ion interaction with HA colloid and colloid size evolution. Formation of colloid aggregates is observed by filtration and AsFlFFF depending on the degree of the dilution. While the average HA size is initially found to be 2 nm, metal-HA complexes are always found to be larger. Such observation is attributed to a metal induced HA agglomeration, which is found even at low coverage of HA functional groups with metal ions. Increasing the metal ion to HA ratio, the HA bound metal ions and the HA entities are growing in size from <3 to >450 nm. At high metal ion to HA ratios, precipitation of FeOOH phases and HA agglomeration due to colloid charge neutralization by complete saturation of HA complexing sites are responsible for the fact that most of Fe and Al precipitate and are found in a size fraction >450 nm. In the more diluted solutions, HA is more relevant as a carrier for metal ion mobilization.
通过浸出试验研究了泰国北部南奔府一个煤矿尾矿区金属离子的释放情况。在模拟雨水（pH 4）和10 mg L⁻¹腐殖酸（HA）溶液（Aldrich腐殖酸，pH 7）中均溶解了大量的锰、铁、铝、镍和钴。由于存在氧化性黄铁矿和硫化物矿物，两种浸出液的pH值均降至约3，并伴有酸性矿山排水（AMD）水成分典型的高硫酸盐浓度。通过随后用10 mg L⁻¹ HA溶液（离子强度：10⁻³ mol L⁻¹）进行稀释（1:100；1:200；1:300；1:500），模拟了酸性浸出液与含有天然有机物的地下水和地表水混合时的相互作用。将不对称流场-流分馏（AsFlFFF）与紫外/可见光谱和电感耦合等离子体质谱检测相结合，能够研究金属离子与HA胶体的相互作用以及胶体尺寸的演变。通过过滤和AsFlFFF观察到，根据稀释程度会形成胶体聚集体。虽然最初发现HA的平均尺寸为2 nm，但金属-HA络合物总是更大。这种观察结果归因于金属诱导的HA团聚，即使在HA官能团被金属离子低覆盖率覆盖的情况下也会发生。随着金属离子与HA比例的增加，与HA结合的金属离子和HA实体的尺寸从<3 nm增长到>450 nm。在高金属离子与HA比例下，由于HA络合位点完全饱和导致胶体电荷中和，FeOOH相的沉淀和HA团聚使得大部分铁和铝沉淀，并存在于尺寸大于450 nm的级分中。在稀释度更高的溶液中，HA作为金属离子迁移的载体更为重要。
