Abstract Recent decreases in the grades of copper reserves have stimulated interest in alternative mining technologies, such as in-situ recovery (ISR), which may be an attractive mining approach for low-grade ores. In ISR operations, lixiviant contacts subsurface ore when it is pumped through the deposit. Continuous flow of lixiviant with suitable properties (such as pH and solution potential, Eh) is required from the wellfield injection point through the ore to the recovery point. Leach solution pH and Eh adjustment is not possible between boreholes and therefore, undesired precipitate formation may result, which could produce blockages and restrict solution flow. Our experiments aimed to simulate the chemical processes that may occur when leach solution travels through an ore deposit from the injection to the recovery well by contacting a pregnant leach solution with fresh ore over multiple stages. Low-grade natural ore that contained refractory copper sulfides mixed with gangue minerals was leached with iron (III) as an oxidant in sulfuric, hydrochloric or methanesulfonic acid at 90 °C. The leach solution was contacted for 72 h with fresh ore in five successive stages, without acid or oxidant replenishment. Although copper extraction continued for the duration of the five stages, the copper extraction dropped off after two contact stages. Precipitates formed in all solutions after three contact stages; akaganeite precipitated in the chloride systems and jarosite and gypsum formed in the sulfate systems after the second contact stage. The extent of precipitation is predicted to increase with an increase in temperature and pH. These findings provide insights into the behaviour that could be expected in ISR operations and factors that influence borehole spacing and ensure continuous lixiviant–ore contact subsurface.

中文翻译：

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多级溶液-矿物接触对低品位天然铜样品原位回收的影响：提取、酸消耗、脉石-矿物变化和沉淀

摘要 最近铜储量品位的下降激发了人们对替代采矿技术的兴趣，例如原位回收 (ISR)，这可能是一种有吸引力的低品位矿石开采方法。在 ISR 操作中，浸出剂在通过矿床泵送时与地下矿石接触。从井场注入点通过矿石到回收点，需要具有合适特性（例如 pH 值和溶液电位，Eh）的浸出剂连续流动。在钻孔之间不可能调节浸出溶液的 pH 值和 Eh，因此，可能会形成不希望有的沉淀物，这可能会造成堵塞并限制溶液流动。我们的实验旨在模拟浸出液通过矿床从注入井到达回收井时可能发生的化学过程，通过多阶段接触富集浸出液与新鲜矿石。含有难熔硫化铜和脉石矿物的低品位天然矿石在 90 °C 的硫酸、盐酸或甲磺酸中用铁 (III) 作为氧化剂浸出。浸出液在五个连续阶段中与新鲜矿石接触 72 小时，无需补充酸或氧化剂。尽管在五个阶段的持续时间内铜提取持续进行，但在两个接触阶段后铜提取下降。经过三个接触阶段后在所有溶液中形成沉淀；在第二个接触阶段后，赤铁矿在氯化物系统中沉淀，而黄钾铁矾和石膏在硫酸盐系统中形成。预计沉淀的程度会随着温度和 pH 值的增加而增加。这些发现提供了对 ISR 操作中可预期的行为以及影响钻孔间距和确保连续浸出剂-矿石接触地下的因素的见解。