Photocatalytic device able to work also at pressures higher than 1 atm. ZnO immobilized on polystyrene beads (ZnO-PS) used in a stainless steel reactor. ZnO-PS was active in the photocatalytic removal of terephthalic acid. ZnO-PS was stable after several reuse cycles. No worsening of photocatalytic activity by increasing the pressure up to 5 atm.