The photocatalytic and antibacterial activity of graphene oxide coupled CoOx /MnOx nanocomposites

CoO x and MnO x metal oxide composites were fabricated via co-precipitation varying the Co:Mn (CM) weight ratio as 4:1, 2:1, 1:1, 1:2 and 1:4, and they hydrothermally coupled with 30 wt% of graphene oxide (GO). XRD analysis revealed the presence of Co 3 O 4 and CoO, and Mn 2 O 3 and Mn 3 O 4 phases in pure CoO x and MnO x metal oxides, respectively. The irregularly shaped metal oxide nanocomposites comprised Co 3 O 4 , Mn 2 O 3 and Mn 3 O 4 phases and were immobilized on GO. The band gap values of the composites varied in the range of 1.86 – 2.22 eV. The highest photocatalytic activity with a rate constant of 3.5 × 10 −3 min −1 was obtained with CMG (1:4). The total removal of MB increased by 55.8 % when CM (1:4) were coupled with GO. The rate of photocatalysis was dramatically increased in the presence of S 2 O 8 2- and was decreased in the presence of EDTA and isopropyl alcohol. The effect of catalyst dosage was determined by varying the weight to 25, 50, 75, and 100 mg, and the dye concentration was varied in the range of 25, 50, 75 and 100 mg/L. The presence of Pb 2+ and Rhodamine B decreased the photocatalytic activity, while it remained the same in the presence of Cl - and PO 4 3- as co-pollutants. The photocatalytic activity of CMG (1:4) was reduced to 72 % upon using the catalyst for five cycles. All the synthesized nanocomposites exhibited greater sensitivity to the Gram-positive strain than the Gram-negative strains. • CoO x , MnO x and their composites were coupled with graphene oxide hydrothermally. • Coupling with GO enhances the photocatalytic activity • The mechanism of the photocatalytic activity of GO coupled CoOx /MnOx was analyzed. • Fabricated composites show excellent antibacterial activity. • The photocatalytic activity of synthesized GO coupled CoOx /MnOx is recyclable.