Ion-exchange mediated removal of cationic dye-stuffs from water using ammonium phosphomolybdate

Abstract

Composition and morphology of micro-sized ammonium phosphomolybdate (APM) particles synthesized under ambient conditions was established using powder X-ray diffraction, fourier transform infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. Further, the ability of APM particles to remove dye from dye-contaminated water was monitored with respect to nature of incident radiation, concentration, pH and nature of dye. APM could effectively remove cationic dyes from water as long as the pH range permitted the dye to retain its cationic behaviour. This specificity suggested that the removal of dye-stuffs could be attributed to ion-exchange between ammonium ions in APM with cationic dye moieties. APM could be reused several times without affecting its efficiency. Removal efficiency of 94.6% could be retained upto 16th cycle and sensitivity to pH enabled APM to reverse the cation exchange process. The ion-exchange process was not dependent on exposure of APM particles to irradiation which confirmed that the mode of action of APM was not photocatalytic in nature.