A novel absorbent composed of cellulose with thiosemicarbazide was prepared for the sorption of heavy metal ions and organic dyes from aqueous solutions. Cellulose was grafted with the vinyl monomer glycidyl methacrylate using ceric ammonium nitrate as initiator and was further functionalized with thiosemicarbazide to afford chemically modified cellulose (CMC). CMC was characterized with FTIR, SEM, TGA, XPS, and XRD. In this work, CMC was used for the adsorption of Hg(II), Cd(II), and acid fuchsin (AF) from their aqueous solutions. The effects of varying parameters such as pH, contact time, temperature, and initial concentration on the adsorption process were examined. According to the obtained results, the adsorption processes could be described by a pseudo-second-order kinetic model. Langmuir, Freundlich, and Temkin adsorption isotherm models were applied to describe isotherm constants. Cd(II) and AF equilibrium data agreed well with the Langmuir isotherm model, while Hg(II) equilibrium data exhibited a better fit to the Temkin isotherm model.