The current study aims to valorize Ceratophyllum demersum, a common aquatic plant in lakes, ponds, and quiet streams with little use. FeCl3-impregnated C. demersum was directly pyrolyzed to yield iron oxide-loaded biochar (IO/BC). Analytical results revealed that 3.19 wt% Fe existed in the resulting composite, including predominant hematite (α-Fe2O3) and minor magnetite (Fe3O4). Moreover, the total pore volume (Vtotal) and the specific surface area (SBET) of IO/BC were 0.091 cm3/g and 113 m2/g, respectively. IO/BC was subsequently explored for catalytic rhodamine B (RhB) degradation using H2O2. At pH 3.0, 30 oC, 1.00 g/L IO/BC partly eliminated 18% RhB (20 ppm), corresponding to an adsorption capacity of 3.6 mg/g. Upon the addition of 120 ppm H2O2, total RhB removal reached 92% after 90 min. Furthermore, RhB treatment was consistent with the pseudo-first-order kinetics. The rate constant (k) at 30 oC was 0.0260 min-1, and the activation energy (Ea) was 72 kJ/mol. Overall, the findings highlighted the catalytic potential of IO/BC prepared from C. demersum for Fenton-like degradation of RhB.