Córdova-Udaeta Mauricio, Cheng Bowen, Fuchida Shigeshi, Takaya Yutaro, Horiuchi Jun, Masuoka Hiroyuki, Oyama Keishi, Tokoro Chiharu
Waseda Research Institute for Science and Engineering, Faculty of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555, Japan.
School of Creative Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555, Japan.
ACS Omega. 2025 Apr 25;10(17):18085-18097. doi: 10.1021/acsomega.5c01588. eCollection 2025 May 6.
Steel pickling wastewater contains valuable iron. Nonetheless, coexisting elements such as Mn need to be separated before Fe recovery. This work studies Mn precipitation phenomena under a pH resembling steel pickling wastewater and compares it to that of Fe under the same conditions. A neutralization-oxidation approach was studied, whereby either NaOH or NH were used as neutralizers and O was the oxidizer. A thermodynamic assessment indicated that NaOH is more effective than NH for precipitation because Mn can react freely with O after NaOH addition, whereas NH may react with O instead. Experimental data showed that neutralization followed by oxidation results in the formation of different Mn oxides, with NaOH confirmed as the most effective neutralizer. Moreover, XRD and XANES analyses showed that the Mn oxidation state in the solids depends on the neutralizer used. Conversely, Fe precipitation was thermodynamically and experimentally observed to depend entirely on pH, with NaOH being a better neutralizer than NH, and pH = 1.5 being the maximum pH where Fe remains dissolved. These insights suggest that using a neutralization-oxidation method that increases the oxidation potential high enough for Mn oxidation while keeping the pH low enough for Fe to remain dissolved could be an effective approach for the selective precipitation of Mn from steel pickling wastewater.
钢铁酸洗废水中含有有价值的铁。然而，在回收铁之前，需要分离共存元素，如锰。本研究考察了在类似于钢铁酸洗废水的pH值条件下的锰沉淀现象，并将其与相同条件下的铁沉淀现象进行比较。研究了一种中和氧化方法，其中使用氢氧化钠或氨水作为中和剂，氧气作为氧化剂。热力学评估表明，氢氧化钠比氨水更有效地用于沉淀，因为加入氢氧化钠后锰可以与氧气自由反应，而氨水可能与氧气反应。实验数据表明，先中和后氧化会形成不同的锰氧化物，氢氧化钠被确认为最有效的中和剂。此外，XRD和XANES分析表明，固体中锰的氧化态取决于所使用的中和剂。相反，通过热力学和实验观察到铁沉淀完全取决于pH值，氢氧化钠比氨水是更好的中和剂，pH = 1.5是铁保持溶解的最大pH值。这些见解表明，使用一种中和氧化方法，将氧化电位提高到足以氧化锰的同时保持pH值足够低以使铁保持溶解状态可能是从钢铁酸洗废水中选择性沉淀锰的有效方法。
