Microplastics are gaining growing research interest due to their significant potential threats to ecosystems and public health. Physical techniques have been proposed as a promising strategy for removing microplastics from the environment. This work innovatively proposes a process of microplastic removal by froth flotation and subsequent carbonization for synthesis of heterogeneous Fenton catalyst. The feasibility of separating different microplastics from water was verified by froth flotation, and iron-loaded carbon derived from separated microplastics was fabricated as catalyst. Carbon material was obtained by carbonization of microplastics, and iron loading was conducted to improve catalytic ability. The catalyst of iron-loaded iron was characterized by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The degradation of tetracycline hydrochloride in the heterogeneous Fenton system was evaluated by single factor experiment and kinetic analysis. The catalytic performance was mainly influenced by H2O2 concentration, solution pH, and co-existing ions. Under the conditions of catalyst 20 mg/L, H2O2 concentration 0.99 mmol/L, initial tetracycline hydrochloride concentration 20 mg/L, pH 4.0, and temperature 25 °C, the removal rate of tetracycline hydrochloride within 15 min reached 81.6%, and the rate constant was 0.138min−1. The catalytic mechanism dominated by hydroxyl radical was verified for the degradation of tetracycline hydrochloride. This work offers insights into the management of microplastics and sustainable treatment of antibiotic wastewater.