A Demonstration of the Circularity Concept for Water Purification using Bionanocomposite Hydrogel Neeraj Kumara*, Hemant Mittalb, Saeed M. Alhassanb, Suprakas Sinha Raya*, aDST-CSIR National Centre for Nanostructured Materials, Council for Scientific and Industrial Research, Pretoria 0001, South Africa bDepartment of Chemical Engineering, Khalifa University of Science and Technology, PO Box 2533, Abu Dhabi, United Arab Emirates cDepartment of Chemical Sciences, University of Johannesburg, Doornfontein 2028, South Africa *Corresponding authors: N. Kumar (ynk.neeraj@gmail.com), S. S. Ray (rsuprakas@csir.co.za) Abstract The circular-economy concept has been accepted by many manufacturing industries as it offers solutions to a number of challenges, including resource scarcity, unnecessary waste generation, and the sustainment of economic advantages. We asked ourselves: Is it possible to apply the circularity concept to water-purification processes? Adsorption has emerged as a simple and economical approach to water decontamination; however, it creates large amounts of secondary toxic waste following the removal of the effluents from the water. In order to avoid secondary environmental pollution, the present investigation introduces a new circular approach that involves the following steps. Firstly, TiO2 nanorods (NRs) and a functionalized gum ghatti (Gg) biopolymer-based bionanocomposite hydrogel (TGB-hydrogel) was synthesized by free-radical graft polymerization and used for the removal of the first toxic model pollutant, namely the brilliant green (BG) dye, from aqueous solution. Secondly, the dye-adsorbed TGB-hydrogel was processed at high temperatures and reused for the photocatalytic degradation of a second model pollutant, namely the antibiotic ciprofloxacin (CIP). Finally, the spent photocatalyst was reinstated for the adsorption of the BG dye, which completes the cycle. The proposed process, different adsorption parameters, and mechanism will be discussed in