Taguchi optimisation studies for removal of hexavalent chromium using magnetic chitosan crosslinked tripolyphosphate/TiO2 hybrid nanocomposite

Abstract

ABSTRACTChromium contamination has been a concern over decades owing to its carcinogenic and determinantal impact on human health. The study aims to develop an easy to synthesise environment-friendly material capable of removing Cr(VI) from phenolic wastewater. To this end, a novel hybrid composite in the form of magnetic chitosan crosslinked tripolyphosphate functionalised with titanium dioxide (CFTPP/TiO2) was prepared using a simple reduction-precipitation technique. Taguchi optimisation study showed that maximum Cr(VI) adsorption could be achieved at optimum synthesis conditions of 90% CFTPP concentration, duration 60 min at room temperature. Similarly, the taguchi optimised adsorption process yielded maximum Cr(VI) removal of 94.36% at pH (2), composite dose (0.8 g), and initial chromium (20 mg L−1) in an equilibrium time of 270 min. Successful formation of composite having a rough surface with broad pore size distribution was further verified using characterisation techniques like FTIR, FESEM-EDX, BET and XRD. Adsorption studies showed that process is mostly chemisorption aligning best with Freundlich isotherm and pseudo second-order kinetics having the maximum adsorption capacity of 82.89 mg g−1. The composite showed good reuse potential and maintained removal efficiencies around 80% even after five cycles. It was observed that %CFTPP concentration in the composite played a significant role in the behaviour of the composite as a photocatalyst in which 35% CFTPP demonstrated higher photocatalytic performance. Higher Cr(VI) removal efficiencies of 70.88% and 98.74% were attained under both visible and UV light respectively on treating 50 mg L−1 Cr(VI) in an irradiation time of 420 min. The research findings demonstrate that CsFe@TPP/TiO2 composite as an environment-friendly material is capable of providing synergistic effect in adsorption and oxidation of chromium contaminated wastewaters.