Fig. 1 shows the schematic diagram of the present MPPM in which there are 49 polypropylene plates (each is 300 mm in
length, 300 mm in width and 3 mm in thickness) coated with nano-TiO2 particles (AEROXITE TiO2 P25, Evonik Degussa GmbH, Hanau, Germany) to enhance the hydrophilicity to form downward liquid film.