Incorporation of graphene/graphene oxide on a low-cost support has been established to improve adsorption performance. This study reports the synthesis of silica nanotubes (SNT) from elephant grass, its encapsulation by reduced graphene oxide (RGO)/graphene oxide (GO) and its application as a highly efficient adsorbent for the remediation of sulfamethoxazole from wastewater. The SNT was synthesized and encapsulated with GO and RGO, to obtain silica nanotubes graphene oxide (SNTGO) and silica nanotubes reduced graphene oxide (SNTG), respectively. The adsorbents were characterized with FTIR, CHN elemental analysis, thermogravimetric analysis, XRD, field emission scanning electron microscopy, and transmission electron microscopy. The FTIR, elemental analysis, and XRD results confirmed successful synthesis of the materials. SNTGO had an adsorption capacity of 125 mg/g, which increased to 248 mg/g when it was reduced to SNTG in the adsorption of sulfamethoxazole. The pseudo-second-order model best described the adsorption kinetics and the Freundlich isotherm was best fit for the equilibrium data. Thermodynamic studies showed the adsorption process was spontaneous and exothermic. The desorption studies revealed that the adsorbent could be regenerated and reused in the adsorption of sulfamethoxazole. SNTG was a better adsorbent compared to SNTGO for wastewater remediation.