Magnetically separable quaternary g-C3N4/Fe3O4/AgBr/rGO nanocomposite for enhanced photocatalytic degradation of ofloxacin in water under visible light irradiation

• A novel quaternary g-C 3 N 4 /Fe 3 O 4 /AgBr/rGO nanocomposite was successfully fabricated. • g-C 3 N 4 /Fe 3 O 4 /AgBr/rGO exhibited superior performance for ofloxacin degradation. • The nanocomposite showed good stability and could be magnetically separated. • O 2 − radicals exhibit dominant role in ofloxacin degradation. • The proposed mechanism during photocatalytic degradation follows the Z-scheme. Novel photocatalytic-magnetic hybrid quaternary nanocomposite (g-C 3 N 4 /Fe 3 O 4 /AgBr/rGO) was successfully synthesized for the first time via ultrasonication-assisted wet chemistry technique. The nanocomposite was characterized using various advanced characterization techniques and its visible light photocatalytic performance was analyzed by using ofloxacin (OFL) as target pollutant. The photocatalytic degradation efficiency was 100 % under conditions (pH 6.65, 0.1 g/L nanocomposite and 10 mg/L OFL) in 5 h. The pseudo-first-order kinetic constant of g-C 3 N 4 /Fe 3 O 4 /AgBr/rGO was as high as 1.1832 h −1 . Evaluation of different catalysts, catalyst dosage, initial concentrations of OFL and initial solution pH have been studied. Based on the scavenging tests, benzoquinone (BQ) significantly decreased the removal efficiency of OFL to 41.4 %, indicating that O 2 − served as the dominant radical involved in the reaction. More importantly, after undergoing five cycles, the g-C 3 N 4 /Fe 3 O 4 /AgBr/rGO nanocomposite demonstrated robust stability and was effectively separated from the solution through magnetic means. The remarkable performance of g-C 3 N 4 /Fe 3 O 4 /AgBr/rGO is linked to substantial utilization of visible light and facilitation of Z-scheme heterojunctions, thereby facilitating charge separation. The quaternary nanocomposite can be expected to have tremendous potential for the degradation of emerging organic pollutants. Thus, it is favorable for practical application in water and wastewater treatment.