A novel hybrid system for the removal of endocrine disrupting chemicals: Nanofiltration and homogeneous catalytic oxidation

Endocrine disrupting chemicals (EDCs) have received substantial attention over the past decade because of the adverse effects of these chemicals on human health. In the present study, a novel hybrid system combining nanofiltration (NF) with homogeneous catalytic oxidation was developed for the effective degradation of EDCs in sources of drinking water. Bisphenol-A (BPA) was chosen as a model EDC and iron(III)–tetrasulfophthalocyanine (Fe(III)–TsPc) was used as a homogeneous metal catalyst to degrade BPA in the presence of hydrogen peroxide. In batch tests, it was confirmed that monomeric Fe(III)–TsPc was generated under weakly acidic conditions (pH < 4.5) and possessed remarkable catalytic activity—more than 90% of BPA was decomposed within 3 min at pH 4.5. Also, based on GC/MS and LC/MS, compounds such as p-benzoquinone, 4-isopropenyl phenol, BPA-o-quinone, and 4-hydroxyphenyl-2-propanol were identified as reaction intermediates and/or by-products of BPA oxidation, which could further be converted to low molecular weight organic acids. The NF-hybrid system showed higher removal efficiency of BPA than the NF-only system (95% vs. 72%) because BPA in the retentate was continuously decomposed by catalytic oxidation. Permeate flux was slightly lower, but ion rejection was higher, in the NF-hybrid system than in the NF-only system due to precipitation of Fe(III)–TsPc on the membrane surface in the NF-hybrid system.