Neutralization Potential of Overburden Samples Containing Siderite
Neutralization Potential of Overburden Samples Containing Siderite
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含有菱铁矿的覆盖层样品的中和电位
DOI：
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
P. Ziemkiewicz
中科院分区：
文献类型：
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作者：
J. Skousen;J. Renton;H. Brown;P. Evans;B. Leavitt;K. Brady;L. Cohen;P. Ziemkiewicz
酸碱计算（阿坝）是一种常用的程序来预测碱性或产酸潜力的覆盖层。当覆盖层中存在菱铁矿（FeCO 3）时，阿坝中目前所述的中和电位（NP）高估了碱度。菱铁矿最初在消化时产生碱度，但随着时间的推移，碱度被来自三价铁（Fe 3+）水解和沉淀的干燥所中和。31个覆盖层样品中含有不同量的菱铁矿，方解石，黄铁矿，石英进行了分析，由四个NP消化方法和滴定的手或自动滴定。NP方法为：（i）标准Sobek法（Sobek）;（ii）将样品煮沸5分钟的方法（BOIL）;（iii）与BOIL类似的方法，但包括在反滴定前用过氧化氢过滤和处理样品（H2 O2）;以及（iv）在第一次手动滴定后加入H2 O2的改良Sobek法（SobPer）。对于主要含有方解石、石英或粘土的样品，特定样品的NP值在消化方法中相似。对于含有黄铁矿的样品，SobPer方法（无过滤）产生的NP值最低。含菱铁矿的样品表现出很大的变化NP值之间的方法。与Sobek法和BOIL法相比，H2 O2法降低了菱铁矿样品的NP值.与手动滴定相比，自动滴定通常获得较低的NP值，因为自动滴定缓慢添加碱，这允许铁的同时氧化和水解。手工滴定菱铁矿样品需要过氧化氢处理以加速铁的氧化。使用Sobek手动滴定法的三个实验室中，特定样品的NP值变化很大，但使用H2 O2手动滴定法时，实验室之间NP值的平均变化降低了66%。实验室之间NP值的变化也是由于实验室技术人员对相同样品分配了不同的起泡等级，这改变了消化过程中添加的酸的浓度。随着更多的酸，NP值通常增加，特别是对于菱铁矿样品。需要一种更定量的方法来确定NP消化所需添加的酸量，本研究中使用的样品的不溶性残留物百分比可能是一种很好的替代方法，但需要更多的测试和多实验室筛选。阿坝值（使用来自各种方法的%S和NP）与索氏渗滤液pH值和累积碱度进行比较。13个样品中有13个样品的阿坝值与索氏渗滤液质量一致。建议在阿坝程序中进行NP的实验室使用H2 O2法.
Acid-base accounting (ABA) is a common procedure to predict the alkaline or acid-producing potential of overburdens. Neutralization potential (NP) as currently written in ABA overestimates alkalinity when siderite (FeCO 3 ) is present in the overburden. Siderite initially yields alkalinity upon digestion, but with time the alkalinity is neutralized by aridity from ferric iron (Fe 3+ ) hydrolysis and precipitation. Thirty-one overburden samples containing varying amounts of siderite, calcite, pyrite, and quartz were analyzed by four NP digestion methods and titrated either by hand or by autotitration. The NP methods were: (i) standard Sobek method (Sobek); (ii) a method that boils the sample for 5 min (BOIL); (iii) a method similar to BOIL but it includes filtering and treating the sample with hydrogen peroxide before back-titrating (H 2 O 2 ); and (iv) a modified Sobek method that adds H 2 O 2 after the first hand titration (SobPer). For samples containing primarily calcite, quartz, or clays, the NP values for a particular sample were similar among digestion methods. For samples containing pyrite, the SobPer method (no filtering) produced the lowest NP values. Siderite-containing samples showed wide variation in NP values among methods. The H 2 O 2 method decreased NP values of siderite samples compared to Sobek and BOIL methods. Lower NP values were generally obtained with autotitration vs. hand titration because autotitration added the base slowly, which allowed concurrent oxidation and hydrolysis of iron. Hand-titration of siderite samples requires H 2 O 2 treatment to accelerate iron oxidation. Variation in NP values for a particular sample was high among three laboratories using the Sobek hand titration method, but the average variation in NP values among labs decreased by 66% when using the H 2 O 2 hand method. Variation in NP values among labs was also due to the same samples being assigned different fizz ratings by laboratory technicians, which changed the concentration of acid added in the digestion procedure. With more acid, NP values generally increased, especially for siderite samples. A more quantitative approach is needed to determine the amount of acid to add for NP digestion, and the percent insoluble residue of the sample used in this study may be a good alternative but requires more testing and multilaboratory screening. The ABA values (using %S and NP from the various methods) were compared with soxhlet leachate pH and cumulative alkalinity. The ABA values with H 2 O 2 digestion were consistent with soxhlet leachate quality in 13 out of 13 samples. It is suggested that laboratories conducting NP in the ABA procedure use the H 2 O 2 method.