Abstract In areas where access to water of good quality is limited, the use of seawater in mineral processing can be an option. However, the dewatering of waste tailings is adversely affected, particularly when this follows processing at higher pH. The flocculation response of a synthetic clay-based tailings in seawater to different pH conditions was examined in detail, focusing on conditions promoting precipitation of the divalent cations present. Flocculated aggregate growth and breakage during turbine mixing were monitored in-situ in terms of chord length distributions (by focused beam reflectance measurement) and aggregate image capture, with the resultant hindered settling rates also determined. It was found that flocculation in seawater was substantially impaired at pH values greater than 10.3 due to the precipitation of magnesium species. The addition of the precipitated phase to the synthetic tailings increases both the surface area exposed to flocculant and the number of particles or micro-aggregates then needing further aggregation to attain acceptable settling rates. The direct use of seawater in processing operations without resorting to full desalination does not necessarily have detrimental impacts on tailings flocculation and thickening, provided the operation is conducted at a pH that prevents the precipitation of magnesium present within the process liquors.

中文翻译：

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粘土基采矿尾矿的海水絮凝：钙镁沉淀的影响

摘要 在优质水源有限的地区，可以选择在矿物加工中使用海水。然而，废料尾矿的脱水会受到不利影响，尤其是在较高 pH 值下进行处理后。详细研究了海水中合成粘土基尾矿对不同 pH 条件的絮凝响应，重点关注促进存在的二价阳离子沉淀的条件。根据弦长分布（通过聚焦光束反射测量）和聚集体图像捕获，就地监测涡轮混合过程中絮凝聚集体的生长和破裂，同时还确定了由此产生的受阻沉降速率。发现在 pH 值大于 10.3 时，由于镁物质的沉淀，海水中的絮凝作用显着减弱。将沉淀相添加到合​​成尾矿中会增加暴露于絮凝剂的表面积和颗粒或微聚集体的数量，然后需要进一步聚集以获得可接受的沉降速率。直接在加工操作中使用海水而不诉诸完全脱盐不一定会对尾矿絮凝和增稠产生不利影响，只要该操作在防止加工液中存在的镁沉淀的 pH 值下进行。