Nanoparticle-loaded multifunctional natural seed gel-bits for efficient water purification

In this work we demonstrate the use of natural seed based hydrogel bits as robust, recoverable and recyclable support for nanoparticulate catalytic media for multipurpose water purification application. We show that the inexpensive and easily available natural seeds sabja (Ocimum basilicum), which can absorb water to about 30 times their weight can be easily loaded with nanoparticles of functional metal oxides such as visible light photo-catalyst N-doped TiO2 or magnetite (Fe3O4) for effective multiple water purification objectives such as efficient photocatalytic degradation of toxins or bacteria, heavy metal ion (As3+, Cr6+, Pb2+, Cd2+) removal or simple particulate filtering. Indeed, innovative nanoparticle loading strategy can be used to load organic and inorganic materials concurrently, sequentially or simultaneously on the gel-bits while they swell in the process of water absorption. Interestingly the gel-bits maintain their individual identity without agglomeration or fusing, and given their swollen size of about few millimetres they can be easily separated out by simple cloth or millimetre scale filtering. This alleviates the difficulties associated with separating nanoparticles dispersed in the media directly for photocatalytic or other purification purposes. With magnetic nanoparticle co-loading they can also be separated out by magnetic field, which can be beneficial in situations wherein filtering may not be an easy option. It is useful to mention that the same seed gel-bits can also serve as particle size filters for specific applications.