Centre of Chemical Processes Engineering and Forest Products (CIEQPF), Department of Chemical Engineering, University of Coimbra, Rua Sílvio Lima, 3030-790 Coimbra, Portugal.
Water Sci Technol. 2012;66(9):1968-76. doi: 10.2166/wst.2012.406.
This study aimed to assess the selective separation of Cr(III) from Fe(III) from liquid solutions by using a chelating ion exchange resin, Diaion CR 11, from Mitsubishi Chemical Corporation, in the H(+) form. Equilibrium experiments with synthetic solutions of iron and chromium were carried out in batch mode. For both metals favorable adsorption isotherms were obtained, and the experimental data were well described by the Langmuir model. However, the resin exhibited higher affinity for iron than for chromium. The regeneration experiments revealed that, for both metals, HCl provided higher removal efficiencies than H(2)SO(4) and HNO(3). Moreover, precipitation with NaOH allows selectively separate chromium and iron to be stripped from the resin. Experiments in fixed bed operation were carried out to assess the dynamic behavior of the sorption of Cr(III) and Fe(III) into the tested resin by using synthetic and industrial solutions. The experiments with industrial effluent showed that the resin can remove low levels of contaminant transition metal ions, and thus the effluent can be purified for reuse of chromium during periods of 20-25 min. The resin regeneration was achieved with a sequential treatment with HCl and NaOH/H(2)O(2). High efficiencies were observed for both monocomponent and multicomponent systems. A global strategy for separating and recovering Cr(III) from an effluent that also contains Fe(III) is presented, involving the integration of ion exchange (saturation and regeneration phases) and precipitation processes. In conclusion, our approach demonstrates that efficient separation of chromium and iron is possible if ion exchange operation in a fixed bed configuration is optimized and combined with conventional processes such as precipitation.
本研究旨在评估使用三菱化学公司的螯合离子交换树脂 Diaion CR 11（以 H+形式）从液体溶液中选择性分离 Cr(III)和 Fe(III)。在批处理模式下进行了铁和铬的合成溶液的平衡实验。对于这两种金属，均获得了有利的吸附等温线，并且实验数据可以很好地用朗缪尔模型描述。然而，树脂对铁的亲和力比对铬的亲和力更高。再生实验表明，对于这两种金属，HCl 比 H2SO4 和 HNO3 提供了更高的去除效率。此外，用 NaOH 沉淀可以选择性地将铬和铁从树脂中分离出来。通过使用合成溶液和工业溶液，在固定床操作中进行了实验，以评估 Cr(III)和 Fe(III)被测试树脂吸附的动态行为。使用工业废水进行的实验表明，该树脂可以去除低水平的污染物过渡金属离子，从而可以在 20-25 分钟的时间内对流出物进行净化以回收铬。树脂的再生可以通过 HCl 和 NaOH/H2O2 的顺序处理来实现。在单一组分和多组分系统中均观察到高效率。提出了一种从含有 Fe(III)的废水中分离和回收 Cr(III)的综合策略，涉及离子交换（饱和和再生阶段）和沉淀过程的集成。总之，如果优化固定床配置中的离子交换操作并与沉淀等常规过程结合使用，就有可能实现铬和铁的有效分离。
