ABSTRACT

In the Quadrilátero Ferrífero Region, located in the state of Minas Gerais – Brazil, the utilization of recycled water from the tailing dams in the reverse cationic flotation of siliceous iron ores is common practice. In such process, ore concentrates assigning dolomite (2.5% to 10%) besides quartz in the mineral gangue, do not reach the desired specification for the production of blast furnace pellets (≤2% SiO₂) given the loss of selectivity occurring in the separation of quartz from the Fe-bearing minerals, which can be related to a rise in the ions Ca and Mg in an aqueous medium resulting from the dissolution of dolomite. With a view to improving the reverse cationic flotation route for this type of ore, fundamental studies (microflotation trials, zeta potential, adsorption/Fourier-transform infrared spectroscopy) into the effect of the Ca and Mg ions in the cationic flotation with the use of pure quartz and hematite mineral samples were carried out. The results attained with the Ca ions were presented in previous studies by the authors. The current investigation presents the results achieved with the Mg ions, added in water as MgCl₂. In the microflotation trials carried out at pH 10.5, amine dosage for maximum recovery of quartz (2.5 ppm) and hematite (50 ppm) was applied. A strong depression of hematite by starch was confirmed, which did not occur with quartz. In the case of the Mg ions, a stronger depression effect was observed, if compared to starch, for the two minerals, starting from a dosage of 10 ppm of MgCl₂. After the conditioning of both minerals with 10 ppm of MgCl₂, followed by conditioning with 10 ppm of starch, the recoveries attained were negligible (3.5% to 4.4%). Based on thermodynamic data, zeta potential measurements, and infrared spectroscopy, it was concluded that the strong depression effect caused by the Mg ions on both minerals owes to the adsorption of the Mg²⁺ and MgOH⁺ species and also the precipitation of Mg(OH)₂, where the starch is chemically adsorbed, preventing further amine adsorption. Only quartz recovery was reestablished after the complexation of the Mg ions in the water by ethylenediaminetetraacetic acid having close molar concentrations to the molar concentration of the Mg ions followed by starch conditioning. The results presented indicate the need for a reduction in the concentration of Mg in the water used, before flotation is conducted.

摘要

在位于巴西米纳斯吉拉斯州的 Quadrilátero Ferrífero 地区，在硅质铁矿石的反阳离子浮选中利用尾矿坝的再生水是常见的做法。在这样的过程中，除了矿物脉石中的石英外，分配白云石（2.5％至10％）的精矿没有达到生产高炉球团（≤2％SiO _{2 ）所需的规格}) 考虑到在从含铁矿物中分离石英时发生选择性损失，这可能与白云石溶解导致水介质中 Ca 和 Mg 离子升高有关。为了改进这类矿石的反阳离子浮选路线，基础研究（微浮选试验、zeta 电位、吸附/傅里叶变换红外光谱）研究了 Ca 和 Mg 离子在阳离子浮选中的作用进行了纯石英和​​赤铁矿矿物样品。作者在之前的研究中介绍了使用 Ca 离子获得的结果。目前的研究展示了以 MgCl _{2形式添加到水中的 Mg 离子所取得的结果}. 在 pH 值为 10.5 的微量浮选试验中，使用胺剂量以最大程度地回收石英 (2.5 ppm) 和赤铁矿 (50 ppm)。证实了淀粉对赤铁矿的强烈抑制，而石英没有发生这种情况。在 Mg 离子的情况下，如果与淀粉相比，对于这两种矿物质，从 10 ppm 的 MgCl ₂剂量开始，观察到更强的抑制作用。在用 10 ppm MgCl ₂调理两种矿物质后，再用 10 ppm 淀粉调理后，所获得的回收率可以忽略不计（3.5% 到 4.4%）。根据热力学数据、zeta 电位测量和红外光谱分析，得出的结论是 Mg 离子对两种矿物造成的强烈抑制作用是由于 Mg ^{2+的吸附。}和 MgOH ⁺物质以及 Mg(OH) ₂的沉淀，其中淀粉被化学吸附，防止进一步的胺吸附。在水中的镁离子通过摩尔浓度接近镁离子摩尔浓度的乙二胺四乙酸络合后，仅恢复石英回收率，然后进行淀粉调理。所呈现的结果表明在进行浮选之前需要降低所用水中的镁浓度。