The Effect of Magnetic Stirring Duration and Ascorbic Acid Concentration on the Yield of Reduced Graphene Oxide Isolated from East Kalimantan Bituminous Coal

East Kalimantan bituminous coal has a carbon composition of 70.24%, indicating a crystal structure of graphite layers. This makes it a viable material for creating reduced graphene oxide (r-GO), which has multiple advantages in various properties and can be employed in numerous technological applications. RGO is obtained by nearly eliminating oxygen functional groups in graphene oxide (GO) through sonication for 3 hours at pH 4. The yield with the lowest value at a 10% concentration of ascorbic acid and 50 minutes of magnetic stirring was selected as optimal. To characterize the resulting product, FTIR was utilized and revealed that O-H (84.21%), C=C (63.04%), and C-O-C (61%) had the highest %T. Technical abbreviations were explained upon first use. Energy-dispersive X-ray (EDX) analysis demonstrated a 90.6% increase in carbon content from 40.159% in GO to 76.554% in r-GO. In parallel, oxygen content decreased from 40,973% in GO to 17.551% in rGO, marking a 57.16% decrease. The morphology of the resulting rGO closely resembled the reference. Additionally, rGO exhibited a C:O ratio of 4.378, surpassing the C:O ratio of GO, which was 1.02. RGO density and pH value were 1.45 g/cm³ and 2, respectively.