Gold losses and mercury recovery in artisanal gold mining on the Madeira River, Brazil
Gold losses and mercury recovery in artisanal gold mining on the Madeira River, Brazil
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DOI：
10.1016/j.jclepro.2015.05.012
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发表时间：
2015-09-01
影响因子：
11.1
通讯作者：
Veiga, Marcello M.
中科院分区：
文献类型：
--
作者：
Balzino, Michela;Seccatore, Jacopo;Veiga, Marcello M.
在过去的40年里，手工采矿一直在巴西亚马逊地区的龙多尼亚州马德拉河的经济中发挥着关键作用。该区域手工采矿者回收黄金的主要方法是疏浚河流。挖泥船是一种浮动平台，挖掘河底，经过分选阶段后，通过汞齐化法从沉积物中分离出金（Au）。本文的目的是绘制该过程，证明无法完全恢复Au从挖掘的沉积物，并揭示汞的实际影响。访问了几个挖泥船，并分析了采矿和加工回路中涉及的所有单元操作。Au的大量损失与低效的分选技术有关。在分选阶段被拒绝的沉积物的Au品位范围为0.1至7.8 ppm，达到高于世界平均Au品位的生产矿山。通过分析汞齐化过程，可以量化汞释放到环境中以及从环境中回收的汞。结果表明，与人们普遍认为的相反，汞是从河底回收的，而不是释放到河底，总汞-质量平衡实际上接近正回收，排放因子（Hg：Au比）低于平均值（0.1-0.2）。尽管如此，汞仍继续以蒸汽形式挥发到大气中。在马德拉河地区，必须开展一项运动，鼓励使用更有效和无汞的技术回收Au。负责任和无汞的年度股东大会运营可以有效地促进整个地区的恢复。(C)2015爱思唯尔有限公司版权所有。
For the last 40 years artisanal mining has been playing a key role in the economy of the Madeira River, State of Rondonia, in the Brazilian Amazon. The main process through which artisanal miners in the region recover gold is by river dredging. The dredges are floating platforms that excavate the bottom of the river and, after a sorting phase, separate the gold (Au) from the sediment by means of mercury (Hg) amalgamation. The objectives of this paper are to map the process, demonstrate the inability to completely recover the Au from the excavated sediments, and reveal the actual impact of Hg. Several dredges were visited and all the unit operations involved in the mining and processing circuit were analyzed. Significant losses of Au are associated with inefficient sorting techniques. The Au grade of the sediments rejected during the sorting phase ranges from 0.1 to 7.8 ppm, reaching values higher than the world average Au grade of the producing mines. Analyzing the amalgamation process, it was possible to quantify the Hg released into and recovered from the environment. The results show that, contrary to common belief, Hg is recovered from the bottom of the river instead of being released into it. The total Hg-mass balance is actually closed with a positive recovery and with an emission factor (Hg:Au ratio) lower than the average (0.1-0.2). Despite this result, Hg continues to be volatilized into the atmosphere in the form of vapors. In the region of the Madeira River a campaign must be developed to encourage the use of more efficient and Hg-free technologies for Au recovery. Responsible and Hg-free AGM operations can contribute effectively to rehabilitate the entire area. (C) 2015 Elsevier Ltd. All rights reserved.