Retraction Note to: Effect of Metal Oxides on the Catalytic Activities of Sulfonated Graphene Oxide for the Esterification of Oleic Acid and Conversion of Waste Cooking Oil to Biodiesel

Nanocomposites of metal oxides with graphene oxide and other carbon materials have shown superior catalytic activities in many important chemical reactions. A systematic investigation the effect Fe, Co, Ni, Cu, and Zn, on sulfonated (GO) is detailed in present paper. The nanocomposites GO were prepared under carefully chosen conditions so that content nanocomposites remains similar. used as solid acid catalysts esterification oleic trans-esterification waste cooking oil. Paramagnetic transition showed over non-magnetic ones nanocomposite containing iron being most active. called ‘super acidic’ sites paramagnetic oxides could be reason for enhanced their nanocomposites.