This study reviews the application of sulfate free radicals for the oxidation of organic pollutants in surface water and groundwater. Sulfate free radicals can be generated from persulfate and peroxymonosulfate (PMS) using various activation methods. Activation methods include heat, transition metals, and ultra-violet light. Experiments were conducted to investigate the oxidation of 2,4-dichlorophenoxyacetic acid (2,4-D) by sulfate free radicals generated by the activation of persulfate anion or peroxymonosulfate using ferrous ions. 2,4-D was found to be rapidly oxidized within minutes but plateaued to a asymptotic concentration. The optimal molar ratio of persulfate:Fe2+ or peroxymonosulfate:Fe2+ for the oxidation of 2,4-D was found to be 1:1. The plateauing of 2,4-D concentration in the oxidation process may be due to the rapid conversion of Fe2+ to Fe3+ by the sulfate radicals generated which in turn slowed the activation process. Sequential addition of Fe2+ at different times resulted in further 2,4-D oxidation which indicates that Fe2+ may be limiting in the activation process. A bi-exponential first-order model provided the best fit of the experimental data with R2 values greater than 90%. Ferrous ion can be used as a low cost material to activate persulfate or peroxymonosulfate for the removal of 2,4-D and other organic compounds in contaminated groundwater and drinking water.