A green solar photo-Fenton process for the degradation of carbamazepine using natural pyrite and organic acid with in-situ generated HO.

Pyrite is widely used in Fenton reaction for degradation of pollutants and exhibits great potential for environmental remediation, however, its efficiency is greatly compromised by extra HO and pH adjustment. Herein, a pyrite based green solar photo-Fenton system for carbamazepine (CBZ) treatment is constructed, involving the use of simulated sunlight and natural organic acids with in situ-generated HO and without extra pH adjustment. The addition of organic acids including tartaric acid (TA), citric acid (CA), and ascorbic acid (AA) can form complex with iron in pyrite, which promotes the Fe(II) dissolution. Upon irradiation, pyrite could be excited to produce photoelectrons, which would reduce oxygen to produce HO through a two-step route assisted by organic acids. The simulated sunlight and organic acids promoted the in-situ production of HO and Fe(II) species, sustaining an efficient Fenton reaction. This produced massive hydroxyl radical (OH), as demonstrated by the active species capture experiment. Compared with no degradation of CBZ under pure pyrite, the degradation efficiency of CBZ reached to 70%, 60%, and 53% in pyrite/TA, pyrite/CA, pyrite/AA within 30 min under simulated solar light irradiation, respectively. This work reports the first use of natural pyrite, a typical Fe-mineral semiconductor, to produce OH for CBZ degradation through natural additive assisted Fenton reaction excluding the adding extra HO and pH adjustment.