The rhodamine based receptor, P2 has been developed for the detection of environmentally hazardous Hg2+ ions with a limit of detection, 1.5 x 10(-6) M. The P2 showed a significant colour change from colourless to pink upon binding with Hg2+ ions. As a result, a new peak at 533 nm was observed in UV-vis spectroscopy which was attributed to spirolactum ring opening followed by through bond energy transfer (TBET). In addition, the presence of other competing cations did not interfere the detection of Hg2+ ions. Further, P2 has been successfully immobilized onto the naturally available and highly porous diatomaceous earth particles (P2D) for removal of Hg2+ ions from water. The covalently attached organic molecule in P2D forms complex with Hg2+ ion present in the water and thus traps the Hg2+ ions. Based on this, a proof-of-concept cartridge has been developed for water purification. The cartridge having 450 mg of P2D was able to purify 30 mL of water containing 1 ppm Hg2+ ions. The efficiency of cartridge could be visualized with a colour change from colourless to pink. (C) 2017 Elsevier B.V. All rights reserved.