Chemically Modified Cyperus rotundus Biosorbent for Efficient Removal of Cd(II) From Aqueous Systems

ABSTRACT

Cadmium (Cd) is a harmful environmental contaminant that requires efficient removal strategies. In this study, we prepared and evaluated a chemically modified biosorbent of Cyperus rotundus (CMCRB) for the removal of Cd (II) ions from water. The biosorbent was characterized by FTIR, SEM, BET and TGA. Batch adsorption studies showed the maximum removal (90%) was achieved at pH 5. Kinetic data followed pseudo‐second‐order kinetics ( R ² = 0.9924), suggesting chemisorption, and equilibrium data fitted well with the Langmuir isotherm with maximum adsorption capacity of 168.64 mg g ⁻¹ . Negative enthalpies (ΔH° = −27.08 kJ mol ⁻¹ ) and free energies (ΔG° = −26.56 to −27.65 kJ mol ⁻¹ ) indicated spontaneous and exothermic nature of the process. Moreover, the Dubinin–adushkevich (D–R) isotherm model suggested that Cd (II) biosorption mostly proceeded through an ion‐exchange mechanism, with a mean adsorption energy of 14.4 KJ mol ⁻¹ . The biosorbent showed good efficiency in real water samples and exhibited good reusability. This research positions CMCRB as an effective, cost‐effective and environmentally friendly adsorbent for removing cadmium from water.