Highly enhanced dephosphorylation of phytic acid via pre-complexation of PA-Fe2+ in the Fenton system: High activity, wide pH range and ferryl-based mechanism

Abstract

Phosphate (P) recovery through organic phosphorus (OP) decomposition is extremely crucial for prevention of water eutrophication and the sustainable development of P resources. In this work, for the first time, efficiently abiotic dephosphorylation of phytic acid (PA) through improved Fenton was proposed. The pre-complexation of PA with Fe2+ are creatively revealed to not only enhance the catalytic performance of Fenton reaction to dephosphorylate PA from 33.4 ± 2.1% to 76.3 ± 3.7%, but also extend the pH (3.5–9.0) of Fenton reaction to neutral and alkaline conditions. The pre-complexation of PA with Fe2+ exhibited much higher Fenton reactivity at neutral (65.5 ± 1.2% at pH = 7.0) or alkalescency (76.3 ± 3.7% and 73.1 ± 2.1% at pH of 8.0 and 9.0, respectively) condition than that at acid condition (49.2 ± 2.4% and 57.1 ± 4.3% at pH of 3.6 and 6.0, respectively). Such significant enhancement (p < 0.05) was mainly dependent on the coordination schemes for the complex PA-Fe3+, and ascribed to the accelerated iron cycle, the decreased redox potential of Fe3+/Fe2+, and the generated ferryl species (PA-FeX = O, X means high valence) as main reactive species. PA degradation by this improved Fenton system occurred in a stepwise dephosphorylation manner via I(1,3,4,5,6)P5, I(1,4,5,6)P4 or I(3,4,5,6)P4, I(4,5,6)P3, I(5,6)P2 or I(4,5)P2, and I(5)P1. Furthermore, this improved Fenton system (PA-Fe2+/H2O2) could be a promising method for the attenuation of refractory organic pollutants through ferryl species in natural environment as a kind of “broad-spectrum catalyst”.