Abstract Over recent years, nanofiltration (NF) has been considered as an effective way to improve processing steps in metallurgical and hydrometallurgy applications dealing with mixtures of metal ions in sulphuric-acid-dominated solutions. The principal advantage of NF membranes over reverse osmosis (RO) membranes is their ability to allow for a practically free passage of acid, while metallic species, especially multi-charged species, are efficiently rejected. In general, these sulphuric solutions cover a range from strongly acidic solutions with pH below 1 up to moderately acidic solutions of pH 3. Over this range, changes in the feed acidity influence both the aqueous electrolyte solution speciation ( S O 4 2 − / HS O 4 − / H + ) and the membrane acid–base properties (protonation of carboxylic and amine groups). However, few studies have been published on the trans-membrane transport of inorganic species coupled to changes in their speciation as well as to the properties of the membrane phase. In this study, experimental data on the sulphuric acid rejection for pH values from 1 to 3 have been obtained with an aromatic poly(piperazine)amide membrane (NF270) at various trans-membrane pressures. The results were modelled by a novel version of the Solution-Electro-Diffusion model taking into account equilibrium reactions, and a general (quasi)analytical solution was obtained for the transport of weak electrolytes of arbitrary valence type. The equilibrium weak acid reaction made the total sulphate (SO42−/HSO4−) rejection decrease strongly as the fraction of single-charged hydrogen sulphate (HSO4−) in the feed increased. From the modelling procedure, permeances to H+, HSO4− and SO42− over the studied pH range were determined.

中文翻译：

---

弱电解质纳滤实验与理论研究：SO 4 2– /HSO 4 – /H + 系统

摘要 近年来，纳滤 (NF) 已被认为是改善冶金和湿法冶金应用中处理以硫酸为主的溶液中金属离子混合物的工艺步骤的有效方法。NF 膜相对于反渗透 (RO) 膜的主要优点是它们能够允许酸几乎自由通过，而金属物质，尤其是多电荷物质，可以有效地被拒绝。通常，这些硫酸溶液涵盖从 pH 值低于 1 的强酸性溶液到 pH 值 3 的中等酸性溶液的范围。在此范围内，进料酸度的变化会影响电解质水溶液的形态 (SO 4 2 - / HS O 4 - / H + ) 和膜酸碱特性（羧基和胺基的质子化）。然而，关于无机物种的跨膜传输与其物种形成的变化以及膜相的性质相关的研究很少发表。在这项研究中，使用芳族聚（哌嗪）酰胺膜 (NF270) 在各种跨膜压力下获得了关于 pH 值从 1 到 3 的硫酸截留率的实验数据。结果通过考虑平衡反应的新版本的溶液-电扩散模型进行建模，并且获得了用于传输任意价类型的弱电解质的一般（准）解析解。平衡弱酸反应使总硫酸盐 (SO42-/HSO4-) 截留率随着进料中单电荷硫酸氢 (HSO4-) 的比例增加而显着降低。从建模过程，渗透到H+，