Duinslaeger Nick, Doni Ariadni, Radjenovic Jelena
Catalan Institute for Water Research (ICRA-CERCA), Emili Grahit 101, Girona 17003, Spain; University of Girona, Plaça de Sant Domènec, 3, 17004 Girona, Spain.
Catalan Institute for Water Research (ICRA-CERCA), Emili Grahit 101, Girona 17003, Spain; Aristotle University of Thessaloniki, Thessaloniki 541, 24, Greece.
Water Res. 2023 Aug 15;242:120232. doi: 10.1016/j.watres.2023.120232. Epub 2023 Jun 15.
Graphene sponge anode functionalized with two-dimensional (2D) boron, i.e., borophene, was applied for electrochemical oxidation of C4-C8 per- and polyfluoroalkyl substances (PFASs). Borophene-doped graphene sponge outperformed boron-doped graphene sponge anode in terms of PFASs removal efficiencies and their electrochemical degradation; whereas at the boron-doped graphene sponge anode up to 35% of the removed PFASs was recovered after the current was switched off, the switch to a 2D boron enabled further degradation of the electrosorbed PFASs. Borophene-doped graphene sponge anode achieved 32-77% removal of C4-C8 PFASs in one-pass flow-through mode from a 10 mM phosphate buffer at 230 A m of anodic current density. Higher molarity phosphate buffer (100 mM) resulted in lower PFASs removal efficiencies (11-60%) due to the higher resistance of the graphene sponge electrode in the presence of phosphate ions, as demonstrated by the electrochemical impedance spectroscopy (EIS) analyses. Electro-oxidation of PFASs was more efficient in landfill leachate despite its high organic loading, with up to 95% and 75% removal obtained for perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), versus 77% and 57% removal in the 10 mM phosphate buffer, respectively. Defluorination efficiencies as determined relative to the electrooxidized fraction of PFASs indicated up to 69% and 82% of defluorination of PFOS and PFOA in 10 mM phosphate buffer, which was decreased to 16 and 29% defluorination, respectively, for higher buffer molarity (100 mM) due to the worsened electrochemical performance of the sponge. In landfill leachate, relative defluorination efficiencies of PFOS and PFOA were 33% and 45%, respectively, indicating the inhibiting effect of complex organic and inorganic matrix of landfill leachate on the C-F bond breakage. This study demonstrates that electrochemical degradation of PFASs is possible to achieve in complex and brackish streams using a low-cost graphene sponge anode, without forming toxic chlorinated byproducts even in the presence of >7 g L of chloride.
用二维（2D）硼即硼烯功能化的石墨烯海绵阳极被用于全氟和多氟烷基物质（PFASs）的C4 - C8的电化学氧化。在PFASs去除效率及其电化学降解方面，硼烯掺杂的石墨烯海绵优于硼掺杂的石墨烯海绵阳极；而在硼掺杂的石墨烯海绵阳极上，断电后高达35%的被去除PFASs被回收，而换成二维硼则能使电吸附的PFASs进一步降解。硼烯掺杂的石墨烯海绵阳极在230 A/m²的阳极电流密度下，以单程流通模式从10 mM磷酸盐缓冲液中实现了32% - 77%的C4 - C8 PFASs去除率。更高摩尔浓度的磷酸盐缓冲液（100 mM）导致PFASs去除效率降低（11% - 60%），这是由于在存在磷酸根离子的情况下石墨烯海绵电极电阻更高，电化学阻抗谱（EIS）分析证明了这一点。尽管垃圾渗滤液有机负荷高，但PFASs的电氧化在其中更有效，全氟辛烷磺酸（PFOS）和全氟辛酸（PFOA）的去除率分别高达95%和75%，而在10 mM磷酸盐缓冲液中的去除率分别为77%和57%。相对于PFASs的电氧化部分确定的脱氟效率表明，在10 mM磷酸盐缓冲液中PFOS和PFOA的脱氟率分别高达69%和82%，由于海绵的电化学性能变差，对于更高缓冲液摩尔浓度（100 mM），脱氟率分别降至16%和29%。在垃圾渗滤液中，PFOS和PFOA的相对脱氟效率分别为33%和45%，表明垃圾渗滤液中复杂的有机和无机基质对C - F键断裂有抑制作用。这项研究表明，使用低成本的石墨烯海绵阳极在复杂和微咸水流中实现PFASs的电化学降解是可能的，即使在存在>7 g/L氯化物的情况下也不会形成有毒的氯化副产物。
