**Abstract**

The filtering hydro cyclone is a solid–liquid separation device, generally conical in shape. The hydro cyclone allows the separation of microplastics from water, to facilitate micro-recycling. To test the capabilities of a hydro cyclone at separating microplastics from water, Rietema's standard sizes, mathematical and computational fluid dynamics (CFD) modeling were used. The results show that, even dough the mathematical model in unreliable when considering parameters out-side standard operation conditions, hydro cyclone microplastic separation can be achieved at 98% efficiency. Particles reach the outlet on average in 1.5 s for a flow velocity of 2 m/s, and denser microplastics end up in the underflow.

**Keywords:** hydro cyclone, water treatment, microplastics, filtration, separation
