ZnIn2S4/CoFe2O4 p-n junction-decorated biochar as magnetic recyclable nanocomposite for efficient photocatalytic degradation of ciprofloxacin under simulated sunlight

Photo-induced charge carrier mobility, light absorption ability and micro-morphology of photocatalyst are vital aspects affecting photocatalytic activity. In this work, p-n junction ZnIn2S4/CoFe2O4 and biochar (ZIS/CFO/BC) were combined via a two-step hydro- & solvent-thermal method. To study the morphology, crystal phase, surface condition and optical property of related photocatalytic samples, a series of characterization methods were carried out: XRD, FTIR, SEM, TEM, XPS and so on. The composite exhibited enhanced charge carrier separation, excellent light absorption intensity and hierarchical porous morphology. The ternary ZIS/CFO/BC composite showed good photodegradation efficiency (96.9 %) and TOC removal percentage (83.0 %) towards ciprofloxacin under simulated sunlight, as well as superior recyclability and stability after six cycles. The introduction of biochar prevented the agglomeration of photocatalytic nanoparticles, and promoted charge carrier mobility. The synergy between good adsorption of biochar and photocatalytic activity of p-n junction greatly improved photodegradation performance. Superoxide (·O2–) radical played a major role during photodegradation. The effects of coexisting anions (Cl-, NO3–, CO32–) and humic acid were investigated. Furthermore, the photodegradation pathway was studied and possible mechanism was proposed. This study provides new insights into the fabrication of recyclable photocatalyst with high potential for environmental purification.