The depletion of ore deposits, the increasing demand for raw materials, the need to process low-grade, complex and finely disseminated ores, and the reprocessing of tailings are challenges especially for froth flotation separation technologies. Even though they are capable of handling relatively fine grain sizes, the flotation separation of very fine and ultrafine particles faces many problems still. Further, the flotation of low-contrast semi-soluble salt-type minerals with very similar surface properties, many complex interactions between minerals, reagents and dissolved species often result in poor selectivity. This study investigates the flotation beneficiation of ultrafine magnesite rich in dolomite from desliming, currently reported to the tailings. The paper especially focuses on the impact of the depressant sodium hexametaphosphate (SHMP) on the following: (i) the froth properties using dynamic froth analysis (DFA), (ii) the separation between magnesite and dolomite/calcite, and (iii) its effect on the entrainment. As a depressant/dispersant, SHMP has a beneficial impact on the flotation separation between magnesite and dolomite. However, there is a trade-off between grade and recovery, and as well as the dewatering process which needs to be considered. When the SHMP increases from 200 g/t to 700 g/t, the magnesite grade increases from 67% to 77%, while recovery decreases massively, from 80% to 40%. The open circuit with four cleaning stages obtained a concentrate assaying 77.5% magnesite at a recovery of 45.5%. The dolomite content in the concentrate is about 20%, where 80% of dolomite was removed and importantly 98% of the quartz was removed, with only 0.3% of the quartz in the final concentrate. Furthermore, the application of 1-hydroxyethylene-1,1-diphosphonic acid (HEDP) as a more environmentally friendly and low-cost alternative to SHMP is presented and discussed. Using only 350 g/t of HEDP can achieve a similar grade (76.3%), like 700 g/t of SHMP (76.9%), while obtaining a 17% higher magnesite recovery as compared to 700 g/t of SHMP. Interestingly, the proportion of hydrophilic quartz minerals ending up in the concentrate is lower for HEDP, with only 1.9% quartz at a recovery of 21.5% compared to the 2.7% of quartz at a recovery of 24.9% when using SHMP. The paper contributes in general to understanding the complexity of the depressant responses in froth flotation.

中文翻译：

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六偏磷酸钠对富白云石脱泥尾矿中超细菱镁矿浮选的影响

矿床的枯竭，对原材料的需求不断增加，对低品位，复杂且细分散的矿石进行加工的需求以及尾矿的后处理等都是挑战，尤其是对于泡沫浮选分离技术而言。尽管它们能够处理相对较小的晶粒尺寸，但非常细的颗粒和超细的颗粒的浮选分离仍然面临许多问题。此外，具有非常相似的表面性质的低对比度半可溶性盐型矿物的浮选，矿物，试剂和溶解物质之间的许多复杂相互作用常常导致较差的选择性。这项研究调查了从浮渣中浮选出的富含白云石的超细菱镁矿的浮选工艺，目前已报告到尾矿。该论文特别关注了六偏磷酸钠（SHMP）抑制剂对以下方面的影响：（i）使用动态泡沫分析（DFA）的泡沫特性，（ii）菱镁矿与白云石/方解石之间的分离，以及（iii）对夹带的影响。作为一种抑制剂/分散剂，SHMP对菱镁矿和白云石之间的浮选具有有益的影响。但是，在等级和回收率以及脱水过程之间需要权衡取舍。当SHMP从200 g / t增加到700 g / t时，菱镁矿品位从67％增加到77％，而回收率则从80％大大降低到40％。具有四个清洁阶段的开路得到的精矿含量为77.5％菱镁矿，回收率为45.5％。精矿中的白云石含量约为20％，其中去除了80％的白云石，重要的是去除了98％的石英，最终精矿中只有0.3％的石英。此外，介绍并讨论了1-羟基乙烯-1,1-二膦酸（HEDP）作为SHMP的一种更环保和低成本的替代品的应用。仅使用350 g / t的HEDP可以达到类似的等级（76.3％），例如700 g / t的SHMP（76.9％），而菱镁矿的回收率比700 g / t的SHMP高出17％。有趣的是，对于HEDP，最终浓缩物中亲水性石英矿物的比例更低，只有1.9％的石英的回收率为21.5％，而使用SHMP时为2.7％的石英的回收率为24.9％。本文总体上有助于理解泡沫浮选中抑制剂反应的复杂性。