Hydroxylamine enables rapid heterogeneous-homogeneous coupled Fenton sulfamethazine degradation on ferric phosphate

Heterogeneous-homogeneous coupled Fenton (HHCF) processes compromise the merits of rapid degradation and catalyst reusability, thus are very attractive for environmental remediation and water treatment. However, the development of HHCF processes suffers from the lack of desirable catalysts and Fe(III)/Fe(II) redox cycle (iron cycle) mediators. Herein we demonstrate the combination of hydrogen peroxide, ferric phosphate and hydroxylamine offers a promising HHCF process, where ferric phosphate and hydroxylamine serve as the catalyst and iron cycle mediator, respectively. Hydroxylamine can realize suitable iron release from ferric phosphate, effective iron cycle, and •OH consumption, resulting in efficient conversion of H2O2 to •OH for sulfamethazine removal. More importantly, the phosphorus release from ferric phosphate and nitrogen residual during this HHCF process are limited to reduce the risk of secondary pollution. This study clarifies the importance of iron dissolution and iron cycle on highly efficient Fenton processes, and also provides a promising antibiotic pollutant removal strategy. [Display omitted] •FePO4/H2O2/NH2OH offers a promising heterogeneous-homogeneous coupled Fenton process.•Hydroxylamine realizes suitable iron release from FePO4 and effective iron cycle to produce •OH.•Hydroxylamine less consumes •OH to promote oxidative removal of sulfamethazine.•Phosphorus release from FePO4 and nitrogen residual are limited.