Abstract

To substantiate the operating parameters of the extraction of manganese and iron ions from water using microfiltration ceramic membranes, an essential condition is their complete precipitation in the form of hydroxides, since the main factor affecting the impermeability of such membranes is steric. The formation of insoluble hydroxide particles is directly dependent on the products of their solubility, as well as the initial concentrations of metal ions and pH of water: the higher the concentration of metal ions, the lower the pH values at which the formation of an insoluble precipitate begins. At pH 4.93 and 10.83, there is quantitative precipitation of Fe(III) and Mn(II) hydroxides, respectively. It is at the pH values indicated above that the minimum concentration of ionic (soluble) forms of these metals is observed. Therefore, at pH 7.5, typical for groundwater, there are practically no soluble forms of Fe(III), regardless of its input concentration (Fe(III) hydroxides are retained by the membrane), and the residual concentration of iron in water is significantly lower than the maximum permissible concentration for drinking water (0.2 mg/dm³). For Mn(II), at its concentrations typical for natural groundwater, the precipitation of its hydroxides, according to calculations based on the product of solubility, does not occur. However, experimental studies have shown that the concentration of Mn(II) in the input water is much higher than in the purified one. The results indicate a possible mechanism for the removal of Mn(II) from water, both due to the complexation of its ionic forms with the ferrinol groups of the dynamic membrane formed by Fe(III) hydroxides on the ceramic membrane and partly due to the steric factor, that is, a decrease in the pore size of the membrane itself. The calculations have shown the expediency of the conditions for the selection of quantitative precipitation of metal hydroxides based on the solubility products of low-dissociated compounds, as well as the possibility of assessing the mechanism of the removal of toxic metals when used as precipitation (coagulation), adsorption, membrane, and other methods. Based on the determination of the concentration of toxic metals in the input water, it is possible to estimate their equilibrium concentration in purified water.

中文翻译：

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基于理论计算确定微滤陶瓷膜净化铁锰水的最佳条件

摘要

为了证实使用微滤陶瓷膜从水中提取锰和铁离子的操作参数，一个基本条件是它们以氢氧化物的形式完全沉淀，因为影响这种膜的不渗透性的主要因素是空间的。不溶性氢氧化物颗粒的形成直接取决于其溶解度的乘积，以及金属离子的初始浓度和水的 pH 值：金属离子浓度越高，形成不溶性氢氧化物颗粒时的 pH 值越低。沉淀开始。在 pH 值 4.93 和 10.83 下，分别有 Fe(III) 和 Mn(II) 氢氧化物的定量沉淀。正是在上述 pH 值下，观察到这些金属的离子（可溶）形式的最低浓度。因此，在 pH 7.5 时，³）。对于 Mn(II)，在其天然地下水的典型浓度下，根据基于溶解度乘积的计算，不会发生其氢氧化物的沉淀。然而，实验研究表明，输入水中的 Mn(II) 浓度远高于纯净水中的浓度。结果表明从水中去除 Mn(II) 的可能机制，这既是由于其离子形式与由 Fe(III) 氢氧化物在陶瓷膜上形成的动态膜的铁醇基团络合，部分原因是空间因子，即膜本身孔径的减小。计算表明，根据低离解化合物的溶度积，选择金属氢氧化物定量沉淀的条件是有利的，以及评估在用作沉淀（凝结）、吸附、膜和其他方法时去除有毒金属的机制的可能性。基于对输入水中有毒金属浓度的测定，可以估计它们在纯净水中的平衡浓度。