To enhance biodegradation in Permeable Reactive Barriers, Diphenyldichlorosilane (DPDSCI) coated ammonium zeolite was selected as a reactive material for development as it undergoes reversible hydrocarbon adsorption and may release nutrients in a controlled manner. To investigate its hydrocarbon adsorption and nutrient release behaviour under varying conditions, batch tests were conducted by immersing the material into different concentrations of toluene and potassium chloride solutions. Results showed that the ammonium release ability was not significantly influenced by a change in toluene concentration, while the toluene adsorption performance was affected by fluctuations in potassium concentration. The overall ammonium release capacity of the modified zeolite was 0.8 mmol/g, and the toluene adsorption capacity was 9.355 mu mol/g without KCl in solution. The Langmuir isotherm fitted the adsorption isotherms well, indicating that the adsorption mechanism of DPDSCI coated ammonium zeolite is the same as that of DPDSCI coated natural zeolite: a monolayer and homogenous surface adsorption process. Regeneration tests showed that this material may be used, cleaned and reused at least three times without a significant reduction in performance.