Induced electro-Fenton triggers trace iron utilization for simultaneous organic phosphorous degradation and phosphate recovery
Phosphorus recovery from wastewater has the potential to alleviate both phosphorus scarcity and water pollution. Unlike mineral orthophosphate, organic phosphorus (OP) recovery typically requires multiple steps: oxidation to orthophosphate followed by separation. Electro-Fenton can synchronize these steps in a unified reactor. However, conventional anodic-Fenton (AF) that relies on the direct sacrificial Fe anode, often generates excessive iron sludge. This not only undermines the oxidative capacity but also changes the optimal pH conditions. Herein, we addressed these challenges by developing an induced electro-Fenton (I-EF) system that significantly reduces iron sludge by 94.0 %. The degradation of 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC, 5.0 mg P/L) in I-EF reached 76.7 % in 60 min, which is much higher than that (46.0 %) in the conventional AF system. Following PBTC degradation to form PO 4 3- , the I-EF system achieved 88 % PO 4 3- recovery through adsorption onto iron hydroxides. The exceptional performance in simultaneous PBTC degradation and recovery can be attributed to multiple functions of minimal iron utilization in the I-EF system. First, trace iron release can prevent quenching of hydroxyl radicals (·OH) by excessive Fe 2+ . Second, the absence of strong iron hydrolysis can maintain a stable pH condition (3.0–3.2) for Fenton reaction and avoid PBTC removal through direct coagulation process. The feasibility of I-EF was also successfully demonstrated for other OP forms containing C-P and C-O-P bonds. The degradation efficiency of various OPs was closely related to their bond energy and complexation capacity with iron hydroxides. This study makes use of the I-EF system to innovatively accomplish the degradation of organic phosphorous and simultaneous phosphate recovery.
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