Peroxymonosulfate enhanced Fe(III) coagulation coupled with membrane distillation for ammonia recovery: Membrane fouling control process and mechanism

Membrane fouling limited the application of membrane distillation (MD) process in resource recovery. In this research, the peroxymonosulfate (PMS) enhanced Fe(III) coagulation process was proposed and proved its effectiveness in eliminating natural organic matter (NOM) and emerging organic contaminants (EOCs). Fe(III)/PMS process significantly enhanced the removal of dissolved organic carbon (DOC), turbidity, and UV₂₅₄, compared to conventional Fe(III) coagulation. Thiamphenicol (TAP) represented the EOCs in the digestate, and Fe(III)/PMS could significantly degrade TAP (86 % degradation). In this course, phenols/quinones served as electron shuttles to induce the Fe(III)/Fe (II) redox cycle. The activation of PMS was boosted, generating the primary reactive substance sulfate (SO₄⁻) radical with intense oxidative properties. In addition, membrane distillation achieved recovery of 93 % of TAN from coagulation effluent without membrane fouling. No tryptophan-like, tyrosine-like, xanthate, and other soluble microbial byproducts were detected on the membrane surface following Fe(III)/PMS pretreatment. The innovation of this study was revealing that the complexation of Fe(III) with NOM could promote Fe (II) regeneration and enhance PMS activation, active substance formation and contaminants degradation. New insights into the role of NOM in the Fe(III)/Fe(II) redox cycle were gained and the development of advanced oxidation process (AOP) coupled membrane technology was promoted to mitigate membrane fouling.