Dual-functional biochar-supported iron trinitrophthalocyanine for tetracycline removal

Despite having superior catalytic activity for Fenton-like reactions, iron trinitrophthalocyanine's large-scale application is still greatly hindered by its tendency to aggregate. This tendency reduces the surface volume of iron trinitrophthalocyanine and disperses its stability in solution. As a catalyst carrier, biochar can improve the catalyst's efficiency in reaction and promote the separation of catalysts in water. In this study, we prepared a heterogeneous catalyst by combining immobilized iron trinitrophthalocyanine with amino (FeMATNPc) and oxidic biochar (O-BC), derived from Flueggea suffruticosa residue for the first time to remove tetracycline (TC). The Fourier transform infrared (FTIR) studies confirmed that FeMATNPc was loaded by biochar via direct bonding and π–π interaction. The optimal loading ratio of O-BC to FeMATNPc is 10:1. The distribution of FeMATNPc on the surface of O-BC increases the catalytic activity of H2O2. Its TC removal reached 51.6% after 60 min. The effect of H2O2 dosage on TC removal fitted the second-order kinetics. The highest removal (93%) was obtained when H2O2 dosing was 60 mM, pH = 7 and temperature was 45 °C. In the catalyzing process, TC was oxidized into small molecule compounds (such as H2O, CO2, and NH4+) through demethylation, ring opening, hydrogenation, and other steps. This work provides an efficient way to prevent the aggregation of iron trinitrophthalocyanine and remove pollutants in water.