Photocatalytic membrane reactor based on Mexican Natural Zeolite: RB5 dye removal by photo-Fenton process

A Mexican natural zeolite (MNZ) of heulandite type was used to develop mesoporous cylindrical membranes based on the extrusion method, the mineral was previously mixed with additives to form a paste with 67.8% of solids. The membranes were calcined at 550 °C, the extruded parts suffered erosion upon water contact at lower calcination temperatures, while the structural properties such as surface area, pore volume and hardness were decreasing at higher temperatures. The MNZ had oxidation states Fe2+ and Fe3+ from the Fe3O4, and the bandgap was 2.42 eV. This cylindrical membrane was arranged as a photocatalytic membrane reactor (PCMR) to evaluate the RB5-dye removal by the Photo-Fenton process using a 2.2 W lamp as radiation source. The Fe effect in the solution and the permeation flow was analyzed at pH = 3, [H2O2] = 3 g/L, [RB5]0 = 100 mg/L, λmax = 405 nm (3.06 eV). The highest RB5-dye discoloration (D30% = 92.3) in the retained was obtained using Fe in solution and a permeation flow which did not show color signals from the reaction beginning (Dt% = 100). A pseudo-first order (n = 1) kinetics was assumed with an apparent kinetic constant of 0.0904 min-1 at the best reaction conditions. Finally, a total organic carbon removal TOC90% = 60.0 and TOC180% = 66.7 in the retentate flow was attained as well as TOC180% = 89.5 in the permeated flow.