Shenzhen Key Laboratory of Precision Measurement and Early Warning Technology for Urban Environmental Health Risks, School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China.
Shenzhen Key Laboratory of Precision Measurement and Early Warning Technology for Urban Environmental Health Risks, School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China.
Water Res. 2024 Sep 15;262:122117. doi: 10.1016/j.watres.2024.122117. Epub 2024 Jul 17.
Phosphonates are widely used scale inhibitors, but the residual phosphonates in drainage are challenging to remove because of their chelating capacity and resistance to biodegradation. Here, we reported a highly efficient and robust Fe-electrocoagulation (Fe-EC) system for phosphonate removal. Surprisingly, we found for the first time that phosphonates like NTMP were more efficiently removed under anoxic conditions (80% of total soluble phosphorus (TSP) in 4 min) than oxic conditions (0% of TSP within 6 min) in NaCl solution. A similar phenomenon was observed when other phosphonates, such as EDTMP and DTPMP, were removed, highlighting the importance of iron complexation and floc formation toward phosphonate removal with Fe-EC. We also showed that the removal efficiency of NTMP by electrochemically in-situ formed flocs (97%) was much higher than post-adsorption systems (ex-situ, 40%), revealing that the growth of flocs consumed the active site for NTMP adsorption. Beyond the removal of TSP, 10 % of NTMP-P was also degraded after the electrolysis phase, evidenced by the evolution of phosphate-P. However, this did not happen in anoxic or chemical coagulation processes, which confirms the formation of reactive oxygen species via Fe(II) oxidation in the oxic Fe-EC system. The primary removal mechanism of phosphonates is due to their complexation with iron (hydr)oxide generated in the Fe-EC system by forming a Fe-O-P bond. Encouragingly, the Fe-EC system exhibits comparable or even better performance in treating phosphonate-laden wastewater (i.e., cooling water). Our preliminary cost calculation suggests the proposed system (€ 0.009/m) has a much lower OPEX under oxic conditions than existing approaches. This study sheds light on the removal mechanism of phosphonate and the treatment of phosphonate-laden wastewater by playing with the iron complexion and flocs formation in classical Fe-EC systems.
膦酸盐被广泛用作阻垢剂，但由于其螯合能力和抗生物降解性，排水中的残留膦酸盐难以去除。在这里，我们报道了一种高效、强大的铁电凝聚（Fe-EC）系统，用于去除膦酸盐。令人惊讶的是，我们首次发现，在 NaCl 溶液中，亚硝酸盐等膦酸盐在缺氧条件下（4 分钟内总可溶磷（TSP）的 80%）比在有氧条件下（6 分钟内 TSP 为 0%）更有效地去除。当去除其他膦酸盐，如 EDTMP 和 DTPMP 时，也观察到类似的现象，这凸显了铁络合和絮体形成对 Fe-EC 去除膦酸盐的重要性。我们还表明，电原位形成的絮体（97%）对 NTMP 的去除效率远高于后吸附系统（异位，40%），这表明絮体的生长消耗了 NTMP 吸附的活性位点。除了 TSP 的去除外，在电解析出阶段，10%的 NTMP-P 也被降解，这可以从磷酸盐-P 的演变中得到证明。然而，在缺氧或化学混凝过程中并没有发生这种情况，这证实了在有氧 Fe-EC 系统中通过 Fe(II)氧化形成活性氧物质。膦酸盐的主要去除机制是由于它们与 Fe-EC 系统中生成的铁（氢）氧化物形成 Fe-O-P 键而发生络合。令人鼓舞的是，Fe-EC 系统在处理含膦酸盐废水（即冷却水）方面表现出相当甚至更好的性能。我们的初步成本计算表明，与现有方法相比，在有氧条件下，该系统（€ 0.009/m）的 OPEX 要低得多。本研究通过在经典 Fe-EC 系统中利用铁络合和絮体形成，揭示了膦酸盐的去除机制以及含膦酸盐废水的处理方法。
