LAUSR

Abstract This work reports the use of porous graphitic carbon nitride (g-C3N4, gCN) for the photocatalytic degradation of ciprofloxacion (CPX) contaminant using two laser wavelengths (285/365 nm). The simultaneous irradiation with both wavelengths promoted the total degradation of CPX dissolved in water. First, an aqueous solution of CPX + gCN was prepared and exposed to laser irradiation with single wavelengths of 285, 365, 405 or 532 nm and no degradation of CPX was observed after 3 h under of continuous irradiation. The solution of CPX + gCN was also exposed to solar irradiation using solar simulated light (Xe lamp). In this case, the maximum degradation percentage for CPX was 68% after 3 h. Afterwards, the aqueous solution of CPX + gCN was irradiated with combined wavelengths of 285/365 nm, 285/405 nm, 285/532 nm and maximum degradation percentages of 100, 62 and 27% were obtained after 3 h, respectively. The complete degradation of CPX during the simultaneous irradiation of 285/365 nm was produced by the following mechanism: the CPX was firstly protonated (charged positively as demonstrated by DFT simulations) due to its direct interaction with 285 nm. Secondly, OH− radicals are generated after photoexcitation of gCN by the two wavelengths and these radicals attacked the protonated CPX by electrostatic attraction (the presence of such radicals was demonstrated by scavenger experiments). The results presented here demonstrated that only two wavelengths are necessary to produce total degradation of CPX (avoiding the use of lamps with full solar spectrum), which could be one way to design more efficient and more compact photocatalytic systems able to degrade organic contaminants.