Cogranulation of Low Rates of Graphene and Graphene Oxide with Macronutrient Fertilizers Remarkably Improves Their Physical Properties

The beneficial effects of graphene (GN) and graphene oxide (GO) additives on the physical properties of monoammonium phosphate (MAP) fertilizer granules were investigated. Low doses (0.05 to 0.5% w/w) of GN and GO sheets were cogranulated with MAP and effects on the crushing strength, abrasion and impact resistance of prepared granules were evaluated. Cogranulation with 0.5% w/w GN sheets (MAP-GN) significantly enhanced the mechanical strength of MAP granules (similar to 18 times improvement) whereas inclusion of same amounts of GO sheets (MAP-GO) improved the strength to a lesser extent (similar to 8 times improvement). The cogranulation of GN also improved MAP granules resistance to abrasion (>70%) and impact resistance (>75%). Heating MAP-GO granules at 50 degrees C after granulation is shown to enhance their physical properties in comparison to MAP-GO granules dried under ambient temperatures. The advantages of GN and GO sheets compared with current additives in enhancing the physical properties of MAP granules are explained by their high specific area, superior nanofiller matrix and adhesion/interlocking ability arising from their unique wrinkled structures and two-dimensional (2D) geometry. These results confirm the potential of GN/GO additives to enhance the physical properties of MAP granules that could be translated to other fertilizers and applied in the industry.