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

Abstract

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 Co₃O₄ and CoO, and Mn₂O₃ and Mn₃O₄ phases in pure CoO_x and MnO_x metal oxides, respectively. The irregularly shaped metal oxide nanocomposites comprised Co₃O₄, Mn₂O₃ and Mn₃O₄ 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 S₂O₈^2- 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 Pb²⁺ and Rhodamine B decreased the photocatalytic activity, while it remained the same in the presence of Cl^- and PO₄^3- 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.