SYNTHESIS AND APPLICATIONS OF POLYMERIC HYDROGELS AS HEAVY METAL LONS AND OTHER INDUSTRIALLY IMPORTANT METAL ION SENSOR

Abstract

The thesis has been divided into six chapters. The literature survey including several reported hydrogels based sensors and adsorbents are summarized as an introduction in Chapter 1. Scope and objectives of the research work discussed in chapter 2. In chapter 3 considering the toxicity of heavy metal ions we have developed a colorimetric sensor 11, 16-bis (phenyl)-6, 6, 21, 21-tetramethyl-m-benzi-6,21- porphodimethene (meta-BPDM) incorporated polyacrylamide/carboxymethyl guar gum (PAM/CMG) polymeric hydrogel. Meta-BPDM is an organic moiety containing pyrrolic and carbocyclic units insoluble in aqueous medium. Zn2+, Cd2+ and Hg2+ , owing to their biological significant value and environmental harm, have attracted more attention. The selective detection of Zn2+, Cd2+ and Hg2+ metal ions has always been challenging due to their closed-shell d10 electronic configuration which makes them spectroscopically silent. The meta-BPDM embedded hydrogel shows high stability, sensitivity and selectivity when it is dipped into the aqueous solutions of Zn2+, Cd2+ and Hg2+ metal ions. During detection, the binding of these metal ions in hydrogel causes hydrogel to change from red to bluish-green which was visually detected and confirmed by UV–visible spectroscopy. The hydrogel was characterized by using solid-state UV–visible spectroscopy, scanning electron microscopy, X-ray diffraction, Thermogravimetric analysis, Fourier-transform infrared spectroscopy, Energy-dispersive X-ray analysis and its sensing properties were studied. The meta BPDM-embedded polymeric hydrogel was found to be an excellent, selective colorimetric sensor for Zn2+, Cd2+ and Hg2+ in aqueous medium without leaching of meta-BPDM from the hydrogel in presence of various other alkali, alkaline and heavy metal ions.