Comparative studies for the sorption of Cs-137 on silica coated potassium copper hexacyanoferrate and potassium cobalt hexacyanoferrate materials and an efficient method was optimized for its maximum sorption. The column sorption method was applied by packing synthesized material in specifically designed columns and low level/fallout level Cs-137 was sorbed on it from 2-4 L seawater sample (0.237 Bq/L). Higher sorption of Cs-137 was achieved on silica coated potassium copper ferrocyanate by optimizing the physical conditions at pH 8. Sorption potential of copper ferrocyanate was higher as compared to cobalt ferrocyanate under same optimized conditions. The developed method was, in field, applied for seawater sample collected from Arabian Sea, near the outfall of Karachi Nuclear Power Plant (KANUPP, Pakistan) by pumping 2-4L of seawater through synthesized material packed in columns. The results suggested that developed method was much precise and accurate as compared to conventional method.