Facile Construction of Iron Phthalocyanine/Carbon Nitride Heterojunction toward Visible Light-Assisted Peroxydisulfate Activation for Efficient Tetracycline Degradation

Iron phthalocyanine/carbon nitride (FePc/CN) heterojunction nanosheets were prepared by a facile calcination strategy, which exhibited superior ability of peroxydisulfate (PDS) activation toward degradation of tetracycline (TC) assisted by visible light. The removal rate of high-concentration TC (50 mg L–1) over FePc/CN-6 reached 97% within 40 min, with the degradation rate constant of 4.4 and 9.2 times those of CN and FePc, respectively. The excellent catalytic performance of FePc/CN-6 could be attributed to the synergistic effect between photocatalysis and PDS activation. The construction of the FePc/CN-6 heterojunction with an intimate interface via π–π conjugation inhibited the aggregation of FePc, promoted charge separation and transfer, and broadened the response range of visible light. As a result, the highly dispersed Fe active sites as well as more available photogenerated electrons and holes enhanced the PDS activation and the photodegradation. EPR spin-trapping tests and radical quenching experiments confirmed the role of multiple active species in the TC removal. The effects of temperature, pH, coexisting anions, and water sources on the removal rate of TC were investigated. FePc/CN-6 also displayed good potential in actual wastewater treatment. This work not only provides insight into design and preparation of efficient and stable catalysts for PDS activation but also establishes a promising catalytic oxidation system for the green remediation of actual wastewater.