In order to reduce the volume of second radioactive waste generated after waste solution treatment, and to increase removal efficiency of Cs-137 in waste solution, potassium nickel hexacyanoferrate (PNHF) has been developed and its adsorption capacity has been compared with those of other adsorption agents. The sequence of the adsorption capacity of Cs-137 in the ash waste solution was PNHF, Prussian blue, sodium tetraphenylborate (NaTPB), and zeolite, whereas the sequence of the adsorption capacity of Cs-137 in the soil waste solution was PNHF, NaTPB, Prussian blue, and zeolite. Meanwhile, the optimum quantities of the PNHF agent to adsorb Cs-137 in ash and soil waste solutions were a100mg agent in a 100mL solution, respectively. In addition, the optimum pH of the ash and soil waste solutions to adsorb Cs-137 with the agent was 7. (C) 2016 Elsevier B.V. All rights reserved.