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Stable and affordable phosphonates removal by iron scrap packed-bed anode electrocoagulation under realistic conditions: Mechanism and passivation mitigation over long-term operation
Water Research ( IF 11.4 ) Pub Date : 2025-01-23 , DOI: 10.1016/j.watres.2025.123195
Haiyang Hu, Jiayu Luo, Linyu He, Yang Lei

Iron electrocoagulation (Fe-EC) exhibits broad application in water remediation towards various pollutants, including emerging organic phosphorus compounds (i.e., phosphonates). However, it suffers relatively high costs due to the frequent replacement of iron anode consumables, particularly electrode fouling. Here we report an iron scrap packed-bed (ISPB) anode electrocoagulation (EC) system for efficiently removing phosphonate. In Na2SO4, NaCl and NaHCO3 electrolytes, the ISPB-EC system effectively removed 39–99% of nitrilotrimethylene triphosphonic acid (NTMP) with 0.1 mM total soluble phosphorus (TSP) concentration at a coulombic dosage of 144 C/L. In contrast, only 2–23% NTMP was eliminated with conventional Fe-EC under identical conditions. We also found the partial conversion of NTMP to inorganic phosphate, primarily attributed to the formation of HO· and Fe(IV)O2+ during the oxidation of Fe2+ in the ISPB-EC system. We further validated the adaptability and robust efficacy of ISPB-EC in realistic conditions, including actual cooling water (ACW). Our cost calculation suggests that the new system achieves a lower cost (€0.0067/m3) in treating NTMP-loaded ACW than the traditional Fe-EC system (€0.009/m3). Moreover, we addressed the scaling issue in the newly developed ISPB-EC system. We did not notice apparent cathode scaling over short-term batch tests. However, orange-red scales gradually formed on the cathode in the continuous flow experiment, accompanied by an increased cell voltage. To this end, we proposed and validated the strategy of periodic polarity reversal in alleviating the cathode scaling. Notably, the voltage can be reduced to the initial level by refilling the iron scrap after eliminating cathode fouling through polarity reversal, realizing the long-term stable operation of the ISPB-EC system over 336 h. Our work established an affordable, highly efficient electrocoagulation system using cheap waste iron scrap electrodes to treat phosphonates-contained wastewater.

中文翻译:


在现实条件下,通过废铁填充床阳极电絮凝稳定且经济地去除膦酸盐:长期运行中的机制和钝化缓解



铁电絮凝 (Fe-EC) 在水修复中表现出广泛的应用,用于处理各种污染物,包括新出现的有机磷化合物(膦酸盐)。然而,由于经常更换铁阳极耗材,尤其是电极结垢,它的成本相对较高。在这里,我们报道了一种用于有效去除膦酸盐的废铁填充床 (ISPB) 阳极电凝 (EC) 系统。在 Na2SO4、NaCl 和 NaHCO3 电解质中,ISPB-EC 系统在 144 C/L 的库仑剂量下以 0.1 mM 总可溶性磷 (TSP) 浓度有效去除了 39-99% 的次氮基三亚甲基三氢三膦酸 (NTMP)。相比之下,在相同条件下,传统 Fe-EC 仅去除了 2-23% 的 NTMP。我们还发现 NTMP 部分转化为无机磷酸盐,这主要归因于 HO·和 Fe(IV)O2+ 在 ISPB-EC 系统中氧化2+ 过程中。我们进一步验证了 ISPB-EC 在实际条件下的适应性和稳健功效,包括实际冷却水 (ACW)。我们的成本计算表明,与传统的 Fe-EC 系统(0.009 欧元/m3)相比,新系统在处理负载 NTMP 的 ACW 时实现了更低的成本(0.0067 欧元/m3)。此外,我们还解决了新开发的 ISPB-EC 系统中的扩展问题。在短期批量测试中,我们没有注意到明显的阴极结垢。然而,在连续流实验中,阴极上逐渐形成橙红色刻度,并伴有电池电压升高。为此,我们提出并验证了周期性极性反转缓解阴极缩放的策略。 值得注意的是,通过极性反转消除阴极污垢后,通过重新填充废铁,可以将电压降低到初始水平,从而实现 ISPB-EC 系统在 336 小时内的长期稳定运行。我们的工作建立了一种经济实惠、高效的电絮凝系统,使用廉价的废铁废电极处理含膦酸盐的废水。
更新日期:2025-01-23
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