Microwave conversion of Plantago Psyllium husk into carbon quantum dots for sensing of heavy metals and removal of organic dyes

The presence of heavy metal ions and organic dyes in the industrial effluents has toxic effects on human and animal health. There is an urgent growing need for the economic and effective treatment of waste water. The carbon dots (CDs) being a fluorescent zero-dimensional material have active surface area capable of binding with toxic heavy metal ions and organic moieties in water. In this study, the CDs have been successfully synthesized from hemicellulose rich Psyllium husk by means of simple green microwave method. The successful formation of CDs and the chemical state of the CDs have been successfully evaluated. The active surface area of CDs arising due to the surface defects contributed by oxygen functionality on the surface has been assessed from FT-Raman and XPS reports. The fluorescence property of the CDs as extrapolated for the sensing of heavy metal ions confirmed the successful sensing of Cr(VI), Fe(II) and Fe(III) ions with a detection (concentration) limit of 0.06 mM, 0.1 M and 0.2 mM, respectively. The photo catalytic performance of the prepared CDs for the discolouration of organic dyes, especially, the cationic dyes is encouraging indicating the successful preparation of negatively charged CDs from the biowaste. Ultimately, the study provides a simple, economical and efficient microwave method for the conversion of biowaste to a smart zero-dimensional carbon material for heavy metal sensing and dye discoloration.