Cation-exchange systems were prepared by phosphorylation of some lignocellulosic materials, namely, rice straw, cotton stalks, and bagasse. The effect of the particle size of the lignocellulosic materials as well as their chemical constituents on the phosphorylation process was studied by the determination of the phosphorus content of the prepared ion-exchange material. Phosphorus was determined using inductively coupled plasma atomic emission spectrometry. Optimization of the phosphorylation reaction was achieved by studying the effect of the different experimental parameters, namely, the reaction time, temperature, and amount of phosphorus oxychloride added, on the phosphate content of the reaction product. The treatment of the lignocellulosic material with sodium hydroxide was found to improve its phosphorylation. The cation-exchange efficiency of the produced phosphated material toward Cd2+, Co2+, Cr3+, Cu2+, Fe3+, Ni2+, Pb2+, and Zn2+ was examined.