Direct Determination of High Grade Gold in Ore by Flame Atomic Absorption Spectrometry with Aqua Regia Sampling Preparation
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摘要: 原子吸收光谱法（AAS）应用于高品位金矿石中金的测定，有效地解决了火试金重量法和氰醌容量法等分析方法有毒化学试剂用量大、测试条件局限性大等诸多问题。泡沫富集-火焰原子吸收光谱法（泡沫富集-FAAS法）就能够测定金品位达到500 μg/g的金矿石，但该方法在常规FAAS方法基础上增加了滤渣分离、滤液稀释及泡沫灰化、复溶等过程，由于操作环节的增多，分析效率不高，且引入测量误差的机率随之加大。本文建立了一种高品位金的快速分析方法，样品用王水溶解，分离残渣，滤液定容后无需分离富集直接采用FAAS测定金量，方法精密度（RSD）为1.6%，优于FAAS本身精密度，满足了高品位金矿石样品快速分析监控的要求。通过实验对黑龙江省某岩金矿矿样（生产监控样）、金矿石外检样品及金矿石国家标准样品采用本法、泡沫富集-FAAS法、氰醌容量法、火试金重量法进行综合分析，结果表明样品基体中铁含量的高低直接影响到本法测定高品位金量的准确性。当金量为50~110 μg/g时，允许样品中铁含量为10%；金量为110~164 μg/g时，允许样品中铁含量为20%；金量为164~218 μg/g时，允许样品中铁含量为25%。研究认为，本法普遍适用于测定金品位达到50 μg/g以上、铁含量小于10%的金矿石。铁在地壳中的平均含量为5.63%，大部分金矿石国家标准样品的铁含量均在此平均值附近，一般金矿石的铁含量也很少达到较高水平，因此本法具备较强的应用性；且与泡沫富集-FAAS法相比，省去了泡沫富集-灰化-复溶的操作过程，大大提高了金量的分析效率。Abstract: Atomic absorption spectrometry (AAS) was applied to the determination of gold in ores with high grade gold, effectively avoiding the problems caused by the fire assay gravimetric and volumetric method with forcyanide quinone, such as the large amount of toxic chemical reagents required and limits of measurement conditions. Foam enrichment-Flame Atomic Absorption Spectrometry (FAAS) can determine the grade of gold reached up to 500 μg/g in gold ore, but this method adds the filter residue separation, diluted and foam ashing, redissolving process based on the conventional FAAS method. Due to the increase in time of the operation process, the analysis efficiency is not high with increasing probability of error. In this paper, a fast analysis method for high grade gold ore is described. The gold ore sample was dissolved by aqua regia, followed by filtering of the residue. The filtrate with constant volume without preconcentration and separation was determined with FAAS. The precision of the method (RSD) is 1.6%, which is an improvement on the precision of FAAS itself and meets the monitoring requirements of rapid analysis for high grade gold ore samples. The gold ore sample collected from Heilongjiang province (a production monitoring samples), an inspection gold ore sample and a national standard gold ore sample were selected to study the established method in this paper, foam adsorption-FAAS method, cyanide quinone capacity method and fire assay gravimetric method. The results show that the accuracy of the iron content directly affects the high grade gold determination. When the gold sample size was 50-110 μg/g, 110-164 μg/g and 164-218 μg/g, the amount of iron content allowed in the samples was no more than 10%, 20% and 25%, respectively. Based on these studies, this presented method is suitable for gold ore samples with more than 50 μg/g gold and less than 10% Fe. The average content of iron in the earth's crust is 5.63%, and the iron content of most national standard reference gold ore materials are close to the average value. The iron content in general gold ores are rarely at a higher level. Therefore, this method is highly suitable. Compared with the method of foam adsorption-FAAS, the operation processes of foam adsorption-ashing-redissolving were eliminated, which greatly improved the analysis efficiency.
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Key words:
- high-grade gold ore /
- gold /
- aqua regia /
- Flame Atomic Absorption Spectrometry /
- iron
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表 1 仪器工作参数
Table 1. Working parameters of the AAS instrument
工作参数 设定条件 波长 242.8 nm/267.6 nm 灯电流 5 mA 狭逢宽度 0.2 nm 燃烧器高度 6 mm 燃气流量 45 L/h 积分方式 Repeated mean 积分时间 3 s 延迟时间 10 s 
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表 2 方法对照试验
Table 2. Comparison of analytical results of Au with aqua regia dissolution-FAAS and others analytical methods
金测定方法 金量(μg/g) RSD(%) 分次测定值 平均值 标准偏差 王水溶样-FAAS法 (本法， n=12) 546 568 538 549 8.76 1.60 542 560 547 550 539 543 555 546 549 泡沫富集-FAAS法[3](n=5) 550 550 540 547 7.56 1.38 538 556 氰醌容量法 ( n=11) 565 561 559 551 10.98 1.99 569 552 544 546 544 537 540 542 火试金重量法 ( n=10) 544 543 546 551 5.42 0.98 552 549 555 557 557 554 556
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表 3 外检样品的金量分析结果比对
Table 3. Comparison of analytical results of Au in inspection samples
外检样品批号 样品编号 金量测定值( μg/g) 泡沫富集-FAAS法[3] 王水溶样-FAAS法 (本法) 2012B15 1 0.20 92.4 2013B68 1 3.49 15.81 2 3.66 19.66 3 0.09 14.60 4 0.09 6.24
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表 4 金矿石国家一级标准样品的金量分析结果
Table 4. Analytical results of Au in gold ore national standard samples
标准物质编号 金量(μg/g) 标准值 泡沫富集-FAAS法[3] 测定值 王水溶样-FAAS法 (本法)测定值 GBW 07809 10.6 10.52 17.15 GBW 07205 14.0 13.83 19.74 GBW 07297 18.3 18.46 20.49 GBW 07206 19.4 19.40 25.24 GBW 07803 20.9 21.20 32.83 GBW 07802 37.3 37.15 56.52 GBW 07801 57.2 57.14 71.20
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表 5 无金的铁溶液中金量测定结果
Table 5. Analytical results of Au in iron solutions without Au
测量对象 吸光度 金量测定值(μg/g) 242.795nm 267.595nm 242.795nm 267.595nm 250 g/L氯化铁溶液 0.1130 0.0657 2.64 1.90 0.1269 0.0654 2.98 1.89 0.1139 0.0672 2.67 1.94 0.1208 0.0681 2.83 1.98 0.1115 0.0635 2.61 1.84
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表 6 加标试验结果
Table 6. Analytical results of addition standard
测量对象 加TFe含量(%) 金量测定值(μg/g) 0.80 μg/mL 金标准溶液 0 0.79 0.5 1.10 1 1.45 5 3.42 10 5.65
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表 7 Au-1样品与金矿石国家标准样品的铁含量测定结果
Table 7. Analytical results of iron content in Au-1 and gold ore national standard samples
样品编号 金量(μg/g) 金量测定的相对误差(%) 总铁(TFe)测定值(%) 推荐值 测定值 分次测定值 测定平均值 Au-1 547 549 0.37 1.84 1.88 1.86 GBW 07809 10.6 17.15 62.3 5.94 5.99 5.97 GBW 07205 14.0 19.74 40.7 3.96 4.03 4.00 GBW 07297 18.3 20.49 12.0 4.89 4.87 4.88 GBW 07206 19.4 25.24 29.9 4.77 4.85 4.81 GBW 07803 20.9 32.83 56.9 12.93 12.93 12.93 GBW 07802 37.3 56.52 51.5 28.70 28.76 28.73 GBW 07801 57.2 71.20 24.5 28.95 29.15 32.83
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表 8 含铁量对金量测定的影响程度试验
Table 8. Effect of iron content on analysis of Au content
Au-1 称样量(g) 样品含铁量 (%) 金量测定值(μg/g) 分次测定值( n=3) 测定平均值 1.0 (含金量 54.7 μg/g) 2 54.4 55.6 54.3 54.8 5 55.7 54.3 55.2 55.1 10 54.0 54.3 53.6 54.0 15 55.4 55.7 56.2 55.8 20 57.0 58.2 61.6 58.9 30 57.8 58.4 58.4 58.2 2.0 (含金量 109.4 μg/g) 2 109.4 108.0 110.8 109.4 15 107.6 108.4 09.6 108.5 20 109.0 110.6 112.8 110.8 25 120.6 120.6 122.2 121.1 30 128.0 122.0 121.6 123.9 35 127.0 130.0 127.6 128.2 3.0 (含金量 164.1 μg/g) 25 161.0 164.5 165.2 163.6 30 175.4 174.5 169.4 173.1 35 177.0 175.4 147.5 166.6 4.0 (含金量 218.8 μg/g) 25 218.6 221.8 216.1 218.8 30 225.1 225.1 230.0 226.7 35 225.1 222.7 223.5 223.8
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表 9 金量测定的允许误差
Table 9. Permissible error of gold determination
Au-1称样量 (g) 金量 (μg/g) 允许相对误差 (%) 允许绝对误差 (μg/g) 1.0 54.7 5.19 5.68 2.0 109.4 4.33 9.47 3.0 164.1 4.33 14.21 4.0 218.8 4.33 18.95
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