Performance of Membrane Photocatalytic Reactor Incorporated with ZnO-Cymbopogon citratus in Treating Palm Oil Mill Secondary Effluent

•Green synthesize of ZnO nanoparticle using different concentration of ZnO solution.•The ZnO-CC 3:1 indicated smaller size (6.6–42.9 nm) of nanoparticles.•Photocatalytic process with ZnO-CC resulting higher colour degradation of POMSE and minimize membrane fouling in membrane photocatalytic reactor (MPR).